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Model Doctor #1
Rust-O-Leum paint is available at most any hardware store at very
reasonable prices in both bulk and spray cans. The paint is fuel
proof and makes an excellent finishing material.
Model Doctor #2
Alliance brand rubber bands are the preferred brand for wing hold
downs and other model applications. They do not deteriorate as
rapidly as American brand (and others). Try them!
Model Doctor #3
Some two liter soda bottles have a black plastic reinforcement on the
bottom of the bottle. This reinforcement piece makes an excellent
radial engine cowling for your next project.
Model Doctor #4
Any yardage goods store sell a variety of straight pins which serve
very well for balsa construction. Check out the extra long ball-head
pins as an especially handy item.
Model Doctor #5
Trying to repair oil soaked wood can be very frustrating. Try using
the product K2R Spot Remover in spray can, available in any super
market in the laundry section, to get the oil out of the balsa wood.
It works great. Heavily saturated sections may take several applications.
Model Doctor #6
A box of See's candy goes a long way in repairing damaged feelings as
a result of an extra long day at the field.
Model Doctor #7
According to the Model Doctor, oil soaked balsa can be successfully
glued with thin CA. It anyone is an expert at gluing oil soaked wood,
it would be him.
Model Doctor #8
Sure Stick non-shrink spackling from Orchard Supply at $1.79 a pint
makes a great, inexpensive filler putty. It's not gritty and sands easily.
Model Doctor #9
An easy way to secure Ny-rod or Golden-rod type push rods to the
sides of the fuselage is to use small pieces of light fabric. Take a
strip of the fabric and lay over the outer case of the push rod and
press against the surface to which you wish to attach the push rod
casing. Flow thin CA on to the fabric to bond the fabric to the
surface. Oh yea, unless you also want to be bonded to the airframe,
use a piece of Saran Wrap between your fingers and the fabric.
Model Doctor #10
If you are having trouble with your engine back firing and kicking
off the propeller or spinner, try cutting a washer out of emery
cloth. Put this emery cloth washer behind the propeller or spinner
back plate, and tighten the propeller nut normally. This solves the
problem even for cantankerous four-cycle engines.
Model Doctor #11
When cutting Monocote type covering material, try a Farber-Castell
Uni-Ball pen to mark the covering where you want your cuts. These
type of pens will actually write on the covering and the marks will
wash off with a damp cloth.
Model Doctor #12
The job of cutting Monocote type covering material with an X-acto
knife is made much easier when you lay the covering material on a
thick bed of newspaper. The newspaper allows the X-acto blade to
completely penetrate the covering material, and you will get
straight, smooth, even cuts every time.
Model Doctor #13
When sealing your engine compartments with polyester resin or other
similar coating materials, fill the mounting bolt holes and blind
nuts with Pic Sticker to prevent your sealing material from fouling
the threads or otherwise plugging up these areas. Another way of
achieving the same result is to use a small birthday cake candle, and
drip the melting wax into the holes. After sealing the compartment,
the wax is easily pushed aside when you insert the screws.
Model Doctor #14
Nylon control surface hinges were a boon to R/C models.
Unfortunately, none of our adhesives stick to them very well. For
safety's sake, you should "pin" all your hinges after you
assemble the control surfaces to the airframe. Do this by drilling a
small hole through the structure and through the hinge material.
Insert a round toothpick in the hole and glue with CA or aliphatic
resin glue. Some planning is necessary for covering or finishing to
avoid the hinge "pins" looking like an after thought. I
usually install the hinges in the main structure first, pin them and
sand everything smooth. Next, cover the model as you normally would.
Lay a strip of covering material on the leading edge of each of the
control surfaces. After ironing on this leading edge strip of
material, install the control surface and pin the control surface
side of the hinge. Now cover the control surface with your covering
material. The result is completely pinned hinges without sacrificing
a nice covering job.
Model Doctor #15
Given how expensive engines are now days, some preventative
maintenance is a must. The easiest way to avoid buying expensive ball
bearings is prevent ruining the ones that came with the engine. At
the end of the flying day, run the engine up to operating
temperature, then disconnect the fuel line in order to run the engine
completely out of fuel. Remove the glo plug and dump after run oil
into the carb until turning the engine over (with a starter) sprays
the after run out the glo plug hole. This usually takes two or three
good streams of oil into the carb. I use Marvel Mystery Oil as an
after run oil. It works as well as the Prather After Run Oil and at
$2.00 a pint, it's a lot less expensive. Isn't it strange how both
oils are identical in appearance?
Model Doctor #16
After cutting threads in wood with a tap (for wing hold down bolts,
for example) saturate the hole with thin CA to "case harden"
the threads. You will have to run the tap through one more time
after the CA sets to clean up the threads. The threads will now last
longer than the airframe.
Model Doctor #17
Our erstwhile Senior Instructor says Mode 1 is the only way to fly.
In most people's opinion, however, Mode 1 gives a whole new meaning
to the term, "Dead Stick".
Model Doctor #18
A easy way to add a different look to your creation is to tint the
canopy a color that compliments your airplane's color scheme. Rit
Cloth Dye, available in most any supermarket, fabric store, or drug
store will tint the clear plastic quite well. Mix up the dye in warm
water in a container large enough to immerse the entire canopy. Dip
the canopy for period of one minute or so, until you get the feel on
how fast the dye is "taking". Rinse in cool water and dry
off. If it is not dark enough, dip it again. I've had some that I
have had to leave in the dye for an hour to get the effect I wanted.
You can even be tricky about the tint by making a fixture to hold
only a certain part of the canopy in the dye. How about two tone
tinting jobs? Anyway, the effects you get are only limited by your imagination.
Model Doctor #19
The black plastic propellers made by Master Airscrew take a lot of
punishment without breaking. That makes 'em great for beginners.
While we are on the subject of propellers, it's a good idea to paint
the tips of your propellers white. You can see the propeller arc
easily this way, and better protect body parts (your body, that is).
While you are at it, you can use the white paint as an aid in
balancing your propellers (the white paint doesn't have to be on both
sides of the propeller).
Model Doctor #20
Most stationary and office supply stores stock adhesive backed, vinyl
letters and numbers which can be used to inexpensively decorate your airplane.
Model Doctor #21
Bamboo chopsticks with their ends carved to a thin paddle shape make
excellent epoxy stirrers. Wipe off the excess epoxy as you go, and
they will last forever.
Model Doctor #22
It is far more convenient to use socket head cap screws for most all
model applications for many reasons. First, you can get as much
torque as you need on the fastener without breaking the screw slot.
You can really torque down on the fastener without fear of the driver
slipping and going through the entire structure, or sliding across
that perfect finish you just applied. The socket head fastener is
also the easiest to get to at remote, confined or long distance
locations. For long distances, you can make a long distance tool by
soldering an allen wrench into a long piece of brass tubing. Try
using 2-56 socket head screws for your control horns on all flying
surfaces and you will find that you can tighten them down without
fear of punching a hole through the structure.
Model Doctor #23
Common sense and AMA rules dictate that your name and address should
be on your model.
Model Doctor #24
Use a paper punch to cut out little circles of gummed paper. Stick
these pieces to the backside of firewall blind nuts. Once you do
this, you can fuel proof the tank compartment with resin without
fouling the threads of the blind nuts.
Model Doctor #25
Roger Caron likes to save money. He uses Velcro to fasten his pilot
figure in one plane and then can transfer it around as he pleases. He
hasn't lost one yet. It must work , so the Ol' Model Doctor is going
to try it.
Model Doctor #26
Many of the small parts we buy are attached to cardboard display
backings and are covered by a protective plastic covering. Save these
protective plastic coverings that come as part of the packaging
media. They are, in effect, small "bowls" and make
excellent vessels in which to mix epoxy. The poly covers that come
with coffee and cans of nuts also make excellent epoxy mixing dishes.
Model Doctor #27
Cut square pieces of old tee shirts and other similar, soft material
and store same in a plastic bag in handy reach of your work bench.
These make excellent all purpose rags, and best of all they are free.
Model Doctor #28
The old (very old, actually) Model Doctor has heard that women's
nylon stockings are a cheap substitute for 1/2 ounce fiberglass and
are especially handy in covering a wing. Simply slide the nylon over
the wing, pull out the wrinkles and apply the resin.
Model Doctor #29
Fabric and yardage stores sell a material product known as
"pellon". This can be used for general reinforcement and is
especially good for wing center sections. Be careful when you do
apply it, as it does have "grain" and should be applied in
the direction that affords maximum strength.
Model Doctor #30
Ever try to epoxy something together only to end up with a glob of
hard epoxy that needs to be sanded, and sanded, and sanded, and
...........? Next time you need to epoxy something without creating a
"epoxy mountain" (two slabs of wood, broken fuselage sides,
lead weights in helicopter blades, etc) try this. After applying the
epoxy and joining the pieces, apply tape (masking or electrical work
fine) over the fresh epoxy. After the epoxy sets, peel the tape off
and presto...a relatively flat joint. Sometimes you will have to do
some minor sanding to get the tape remnants off, but the result is
much better than dealing with a huge ridge of epoxy.
Model Doctor #31
Do helicopters have a CG?....You bet. At least on a Shuttle the CG is
about right when you slowly pick up the heli by the rotor head. As
you take on more and more of the heli's weight, the rear of the skid
should lift first. When the rear of the skid is about one half inch
up, the rest of the heli should come off the surface it is sitting
on. My Shuttle actually needed nose weight to achieve this condition.
Model Doctor #32
During the process of building your next masterpiece, it may become
apparent that tail weight will be required. Lead weight for fishing
lines is available at most sporting goods stores in the form of round
(about 1/8" diameter) strips, several inches long. This strip
lead is easy to cut up and imbed in the model during construction.
For example, strips of lead can be inserted under the triangle stock
used to reinforce the fin or stabilizer on many model designs. It can
also be inserted into wing tips to provide lateral balance.
Model Doctor #33
Plastic engine cowls always look great on you airplane....until you
start the engine. Past experience shows that either due to minor
bumping, engine vibration or just pure spite, they will start to
crack. You can stop the crack from growing by drilling a hole at the
end point of the crack. This "crack stopper" is actually a
device to relieve the high stress area at the end of the crack and is
a common practice in working with sheet metal. the appearance of
these cracks also point out that you should have spent some time
reinforcing the cowl in the first place.
Model Doctor #34
How do you reinforce a plastic cowl, let me count the ways. One way
is to rough up the inside of the cowl with heavy sandpaper (50-80
grit) or by scratching with the sharp point of a #11 Xacto blade. Mix
up a batch of resin (epoxy or polyester) and lay fiberglass cloth
inside the cowl. The bigger the cowl, the heavier the cloth should
be. Another method simply requires the inside of the cowl be clean.
SIG manufacturing sells a product called CELASTIC. It comes in large
sheets and is about 1/16" thick and is fairly rigid. Cut a
section of this material suitable for the area you want to reinforce
and moisten it with acetone until it become limp and mushy. This does
not take long, nor does it take much acetone. Now lay this material
inside the cowl and form it to the contours of the cowl with your
fingers. The acetone will literally melt the cowl plastic and the
Celastic together and make a rigid, tough structure. After the
Celastic dries out it can be sanded, cut, drilled, etc and it will
retain its strength. One sheet will last a lifetime, unless you are
like the ol' Model Doctor and have a propensity to bust up a lot of cowls.
Model Doctor #35
Tired of trying to figure out conversion between a logical measuring
system called metric, and portions of King George's foot? Since the
Ol' Model Doctor knew the good King personally, he provides us with
the following table for the common sizes we deal with in modeling.
Inch....................MM
1/32...................1.0
1/16...................1.5
3/32...................2.5
1/8.....................3.0
3/16...................5.0
1/4.....................6.0
5/16...................8.0
3/8.....................9.5
1/2.....................13.0
1........................25.4
Model Doctor #36
Ever had the prop nut, washer, and propeller fly off while airborne?
Ever heard that sickening "crack!" when you touch the
starter to the engine and then spend the next hour looking for the
prop nut in the tall weeds? Well, try this solution. Put a o-ring on
the end of the engine crank shaft after you get everything secured.
It may keep the prop nut from spinning all the way off next time your
engine decides to be cantankerous. By the way, I hope you have been
around long enough to know that propellers, especially wooden
propellers, compress after being subjected to tightening down of the
prop nut. That's why you see so many coming loose early Saturday
morning at the field. What was tight for the last flight on Sunday,
ain't tight a week later. Check em!
Model Doctor #37
Easy and cheap (a quality the Ol' Model Doctor has spent a lifetime
refining) wheel chocks for you model can be made by cutting holes
just large enough to accept the tires in foam pipe insulation
available at most any hardware store. Cut the insulation in about six
inch lengths. When installed, you plane will roll no mo.
Model Doctor #38
How about a cheap fake instrument panel for your next project? Browse
through full scale aviation magazines until you find a cockpit view
of about the right proportions. A pair of scissors and some white
glue put you in business. Learning from sad experience, the Ol' Model
Doctor advises that you should pay for the magazine before you cut a
page out.
Model Doctor #39
File teeth shaped notches in one end of a piece of brass tubing and
it becomes a very effective hole saw. The correct size will put
perfect holes in bulkheads for push rod material. A 1/4" I.D.
tube will drill out broken dowels from wing leading edges making a
difficult repair easier.
Model Doctor #40
If you ever have had trouble getting nylon bolts started when
attaching the wing or other major subassembly, try this. Bevel the
threaded end of the bolt so it will tend to be self centering when
you're trying to get it started. The easiest way to bevel the bolts
is to stick 'em in one of those school kit hand held pencil
sharpeners and twist.
Model Doctor #41
Are you concerned that a clevis may open up under the stress of
flight conditions? There is usually some plastic tubing provided in
the package of clevis when they come from the hobby shop. The plastic
tubing is provided so you can slide it over the clevis once you have
finished with your adjustments to prevent it from opening up.
However, the provided plastic tubing often cuts or otherwise falls
off the push rod. An excellent replacement (actually better than the
originally provided tubing) is silicon fuel tubing. About a 1/4"
length is more than sufficient. While on the subject of clevis, you
should always use a 2-56 nut on the threaded rod to lock in the
clevis once you get the clevis properly adjusted. Not only does this
lock nut prevent the push rod from rotating and thereby changing your
control surface deflection, you will be amazed as to how much slop is
removed from the control system. Most of the threaded push rod ends
have the threads pressed on the wire instead of cut on with a die.
Couple this sloppy kind of thread with sloppy thread in the clevis
itself, and the 2-56 lock nut becomes almost mandatory.
Model Doctor #42
If you scratch build or are trying to repair a model that landed
somewhere other than the wheels, a replacement canopy is sometimes a
real problem, especially if you are as cheap as the Ol' Model Doctor.
Try studying the shapes of various soft drink or other plastic
bottles to find exactly the contour you need. You cut the area of the
bottle where it necks down to the cap it a variety of sections to
make windshields or entire canopies. Don't forget that heat, in the
form of hot or boiling water may change the almost right shape to the
perfect fit.
Model Doctor #43
In the never ending battle to find a way to secure the receiver
antenna to the tail feathers without breaking either, try this. A
dress maker's straight pin is one of those guys with the blob of
plastic on the head. Take one of these pins and poke it through a
piece of fuel tubing which is about 1/4" long. Poke the pin
through from the inside of the tubing such that the plastic blob
fills up the I.D. of the tubing (if you can't do this, you shouldn't
be building models). Now by pinching, twisting and pulling on the
piece of fuel tubing you can get the antenna wire started through the
fuel tubing and there will be enough friction to keep the wire from
pulling out. Now, simply stick the pin into the top of the fin, or
the side of the fuselage and pull the antenna taunt. The antenna will
stay where you put it, but will move without breaking in the event of
a large bump to the airframe. You'll never have to go on search for a
newspaper rubber band again.
Model Doctor #44
I hate doing hinges. True, pinned hinges that is. Whether I use
epoxy, slow or fast CA, or even spit, I always end up having to tear
it all apart due to the fact that my hinge joint is glued fast. What
do you do? Well you can just use small wood screws or toothpicks to
hold your hinges in place by "pinning them" or you can use
this method told to me by an old wise man (he knows who he is). Take
a drinking straw and cut off about 4" in length. Pinch one end
so that it is flat. Mix your epoxy in a mixing cup not on a piece of
cardboard. And while putting the round end into your mouth gently
suck epoxy into the straw through the flattened end. Withdraw the
straw and then put the flattened end into your hinge gap and blow
lightly. After you have done this to all the hinge gaps, say on the
trailing edge of your wing insert your hinges and use rubbing alcohol
to clean the hinge point of any excess. Oh yeah, use 15 minute epoxy
because 5 minute will set too fast.
Model Doctor #45
If you have the Dremel jigsaw combo that has a sanding wheel and low
speed Dremel tool attachment I have a suggestion for you. Have you
ever noticed that when you turn the unit on the centrifugal force of
the rotating sanding wheel causes the sand paper to "lift
away" from the wheel ? If you have and you've tried to
sand/grind that way, you will catch an edge from time to time and
quite possibly ruin a delicate piece of your model. I purchased a
small aerosol can of 3M contact cement. Spray your wheel and the back
of the sanding disk with a fine mist, allow to get tacky and install
in the usual manner pressing the disk against the wheel firmly.
Viola! No more caught edges.
Model Doctor #46
The construction phase of a built up balsa model has been known to
take several weeks, and sometimes more time! During this period it
happens occasionally that a finished sanded piece, all ready for
covering or painting gets bumped and dented. There is a way to get
these dents out of balsa without additional filler material.
First, wet the dented area with plain ol' water. Make sure the dented
section is well saturated and the water has soaked into the wood.
Then take a Monokote iron, set to its hottest position and gently
iron over the dented area. The steam being generated in the wood
forces open the compressed section (i.e. the dent). I have seen this
method take out some pretty big dents. In fact, it is not uncommon
that a little additional sanding is required because the
"dent" ends up higher then the surrounding area.
Model Doctor #47
Didya ever go through all the trouble to make up your control surface
push rods only to find at installation time they were a 1/4" too
short? Try this as an easy way to get the lengths exactly right. Tie
a string to the control horn on the control surface. Drop the free
end of the string through the fuselage. With the control surface in
the neutral position, tie the other end of the string to the servo
arm. Cut off the excess string at both tie points. Now, cut the
string at both tie points and what you end up with is a piece of
string which is the exact length of the push rod you will need to fabricate.
Model Doctor #48
If you have been flying R/C for more than two years, you will have
started to collect transmitter and receiver battery packs that don't
quite measure up any longer to cycle testing (you do routinely cycle
test your battery packs, don't you?). Don't throw them away because
there are some useful applications for these "unsafe for
flight" battery packs. First, snip off the connector pigtail for
use in making up your new battery packs. You will find homemade packs
to be just as good, and substantially cheaper, as those supplied by
your radio manufacturer. Disassemble and separate the cells in the
old pack. If you have discharged the pack down to a low voltage, you
can use a VOM (volt - ohm meter) to determine which of the cells are
really no good. They will be the one(s) that are still significantly
less that 1.2 volts, measured after you have let the discharged
battery pack sit for about an hour. Deposit those low voltage cells
in you favorite round container. The remaining cells can be wired up
in series to make a self contained electric fuel pump, or wired in
parallel with a glo connector added to make a engine starting pack,
or can be wired in parallel and used as nose weight (in lieu of lead)
with the added benefit of being an on board ignition system; you can
even get fancy with a micro switch on the throttle servo so the
current only comes on at low speeds. These are just a few uses of
old, tired nicads.
Model Doctor #49
When you are through flying for the day, you should always prepare
your engine for lay up, even if you intend to fly again the very next
day. The hard bearing surfaces inside your engine can easily rust
within a matter of hours. The quick and simple solution is to first
run the engine completely out of fuel. Make sure the engine is up to
normal operating temperature before you pull the fuel line off the
carburetor. Then remove the glo plug and pour after run oil down the
carburetor and into the cylinder (into the crank case vent fitting
for four stroke engines). Turn the engine over with your starter
until you are satisfied that the oil has been thoroughly distributed
throughout the engine. Be careful because oil will come blasting out
the glo plug hole during this operation. Reinstall the glo plug and
you'll be ready to go next time with an engine that is in A-1 shape.
There are some after run oils sold at the hobby shops that do a fine
job. For cheap people like me, Marvel Mystery Oil or any Automatic
Transmission Fluid also work just fine. Both are even the same color
as the expensive spread....strange, isn't it?
Model Doctor #50
Hanger rash is the bane of every modeler. A cheap and easy way to
afford some protection to your pride and joy is as follows. For a
wing cover try taking a beach towel and fold it in half, lengthwise.
Ask the wife to sew the towel together down its length and across one
end. Note that your wife must do the sewing part, because you are
obviously not qualified to operate a sewing machine. Presto, a wing
cover. For the tail surfaces, find three Styrofoam blocks of
appropriate size. Hog out slots in the blocks such that you can slide
a block over each end of the horizontal stab and over the top of the
fin. You can even get fancy and glue some dowel stock into the
Styrofoam block so you can rubber band it in place. Presto - chango,
tail feather protection.
Model Doctor #51
A big advantage with gliders is that there is almost no clean up
involved. Power planes, on the other hand, can be a huge pain
especially if you drip oil on to the front room carpet while you are
carrying them back into the house after a day's flying. I have seem a
variety of fluids used for cleaning up the gooey mess of exhaust
residue. My personal favorite, being the el-cheapo that I am, is a
50-50 mixture of suds less ammonia and water. It cuts through the
grease in short order, and leaves no scummy film on the airplane.
However, as with Windex and other commercial cleaning solutions there
are some drawbacks. Most important of these is that many cleaning
solutions are highly corrosive. Therefore, you should avoid spraying
them on engines and exposed radio switches. I have had switch failure
directly because I continuously sprayed my cleaning solution on the
switch. The switch internals were a rotted mess when I took it apart
to see what went wrong. One answer to this problem is to use rubbing
alcohol as a cleaning solution in engine compartments and around
electronics. I routinely douse down my entire helicopter (engine,
radio and all) with the stuff to clean it up. If used with a spray
bottle, the alcohol can be blasted on to engines, engine
compartments, etc. without necessity to rub the grease off with a
rag. Give it a try.
Model Doctor #52
Do you have trouble getting you airplane to come to a complete stop
when the engine is idling on the taxiway? Do you glace away and then
look back only to find the airplane sitting in the drainage culvert?
Try this bunkey....
Take the wheel collars holding the nose wheel on the landing gear
wire and readjust them so they are sandwiching the nose wheel
tightly, causing it to bind slightly on the axle. The amount of
"bind" can be set such that a brisk engine idle will not
cause the airplane to move. If done correctly, this braking action
will not cause any problems in taxi or takeoff. You can also do a the
same thing with the main gear wheels, but getting them so the
"bind" is equal on both sides is difficult. Differential in
binding on the mains will effect taxi and takeoff.
Model Doctor #53
I have found my purse strings tight from time to time, and that has
driven me to search for alternate painting mediums to use on my
planes. I think I have found a great, inexpensive alternative. OSH
sells a wide color range of enamels in aerosol spray cans for $1.99
each. However, they are not nitro proof. The solution to fuel
proofing is a coat or two of clear "Diamond Finish" Flecto
Varathane. This is also available in aerosol spray cans and comes in
satin, semi-gloss and high gloss. Another advantage of using the
Varathane as a fuel proofer is that it can be cleaned up with water,
if caught in time. It sprays on as a milky white, but dries crystal
clear without tinting the base color. It costs $7.49 per can.
Model Doctor #54
How 'bout a quick and dirty wind velocity meter? Take your propeller
balancer and attach a Top Flite 11 x 8 prop. Hold the balancer in the
wind to achieve the maximum propeller RPM. Measure the RPM with your
tachometer. Divide that RPM reading by 100 and the resulting number
will be within 2 MPH of the actual wind velocity.
Model Doctor #55
Hanger rash is the bane of every modeler. A cheap and easy way to
afford some protection to your pride and joy is as follows. For a
wing cover try taking a beach towel and fold it in half, lengthwise.
Ask the wife to sew the towel together down its length and across one
end. Note that your wife must do the sewing part, because you are
obviously not qualified to operate a sewing machine. Presto, a wing
cover. For the tail surfaces, find three Styrofoam blocks of
appropriate size. Hog out slots in the blocks such that you can slide
a block over each end of the horizontal stab and over the top of the
fin. You can even get fancy and glue some dowel stock into the
Styrofoam block so you can rubber band it in place. Presto - chango,
tail feather protection.
Model Doctor #56
The construction phase of a built up balsa model has been known to
take several weeks, and sometimes more time! During this period it
happens occasionally that a finished sanded piece, all ready for
covering or painting gets bumped and dented. There is a way to get
these dents out of balsa without additional filler material.
First, wet the dented area with plain ol' water. Make sure the dented
section is well saturated and the water has soaked into the wood.
Then take a Monokote iron, set to its hottest position and gently
iron over the dented area. The steam being generated in the wood
forces open the compressed section (i.e. the dent). I have seen this
method take out some pretty big dents. In fact, it is not uncommon
that a little additional sanding is required because the
"dent" ends up higher then the surrounding area.
Model Doctor #57
Do you have trouble getting you airplane to come to a complete stop
when the engine is idling on the taxiway? Do you glace away and then
look back only to find the airplane sitting in the drainage culvert?
Try this bunkey....
Take the wheel collars holding the nose wheel on the landing gear
wire and readjust them so they are sandwiching the nose wheel
tightly, causing it to bind slightly on the axle. The amount of
"bind" can be set such that a brisk engine idle will not
cause the airplane to move. If done correctly, this braking action
will not cause any problems in taxi or takeoff. You can also do a the
same thing with the main gear wheels, but getting them so the
"bind" is equal on both sides is difficult. Differential in
binding on the mains will effect taxi and takeoff.
Model Doctor #58
I have found my purse strings tight from time to time, and that has
driven me to search for alternate painting mediums to use on my
planes. I think I have found a great, inexpensive alternative. OSH
sells a wide color range of enamels in aerosol spray cans for $1.99
each. However, they are not nitro proof. The solution to fuel
proofing is a coat or two of clear "Diamond Finish" Flecto
Varathane. This is also available in aerosol spray cans and comes in
satin, semi-gloss and high gloss. Another advantage of using the
Varathane as a fuel proofer is that it can be cleaned up with water,
if caught in time. It sprays on as a milky white, but dries crystal
clear without tinting the base color. It costs $7.49 per can.
Model Doctor #59
The ol' Model Doctor has addressed ways to secure your receiver
antenna in past articles. Here's a few more.
Of course you know that you are never supposed to tie a knot in the
antenna wire. However, you can get heat shrink tubing at most any
electronics store of a size that just fits over the antenna wire
(usually 22 ga wire). Heat the heat shrink tubing on to about the
last inch or so of the antenna wire, leaving about three inches of
the heat shrink extending beyond the antenna wire itself. You can
then tie as many knots as you want in the heat shrink (i.e. tie the
heat shrink to a rubber band) without effecting the antenna in any way.
The inner tubing of most flexible control rod (i.e NYROD, Goldenrod,
etc.) makes a great fastening point for the receiver antenna. Glue a
short piece (1/2" or so) to an appropriate place on the aft
section of the fuselage (vertical or horizontal stab, fuselage side,
etc). Run your antenna wire through the piece of tubing. Then wrap
the antenna wire on the downstream side of the tube with just enough
masking tape to prevent it from easily pulling back though the tube.
Speaking of antennas, never exit the receiver antenna wire to the
exterior of the fuselage by running it out via the wing saddle, or
anywhere near the wing-fuselage joint. The vibration and relative
movement between the two during flight will eventually sever the
antenna wire. The proper method is to punch an exit hole in the
fuselage, near the receiver location and away from exhaust residue.
Obtain from any electronic store heavy sleeving material of the size
that will allow the antenna to slide through. CA about a three inch
piece of this sleeving in the antenna hole such that about a 1/2"
or so is inside the fuselage. Pass the antenna wire through the
sleeving and attach to the rear of the fuselage by one of the
Doctor's suggested methods. However, before you pass the wire through
the fuselage, put a strain relief on the wire inside the fuselage to
prevent it from being pulled out of the receiver. The best and
cheapest strain relief is either a button or a broken off portion of
a servo output arm. Simply weave the wire through the holes in the
button or servo arm about three times and its done. Make sure you
position the strain relief on the antenna wire such that there is
some slack antenna inside the fuselage when all is done.
Model Doctor #60
The Model Doctor occasionally puts his brain in neutral by simply
stealing ideas from others. The following was inspired by the PCC newsletter.
When you car corners poorly, you start looking at suspension or
tire/wheel adjustments. When your airplane turns poorly, you may need
to look at control adjustments. Many aircraft designs require a setup
called, "aileron differential" to help the airplane turn
better. The basic idea here is that the aileron moving in the up
direction travels further that the opposite side aileron moving in
the down direction. For example, the Goldberg Cub specifies 3/8"
upward deflection and only 1/4" downward deflection.
The effect of the Goldberg Cub specification is that the downward
moving aileron adds lift to one side of the plane (along with a small
amount of drag), causing the airplane to roll toward the side with
less lift, but it will also yaw away from the roll direction because
of the drag induced by the aileron deflection. On the other side of
the wing, the upward moving aileron reduces lift on that side for
added roll effect, and also creates drag. The notion of having
increased upward movement is to create more drag on that side of the
airplane to offset the drag on the downward deflecting side, which
creates an overall effect of the airplane yawing into the direction
of the roll. This helps the airplane turn into the direction of the
roll. This combination of roll and yaw will result in very smooth
turns, once you get the amount of differential figured out. Of
course, the differential can be applied in the other direction,
depending on the result you are trying to achieve. You may want to
use differential to eliminate any yaw when rolling the airplane.
Unless you use a servo for each aileron along with a computer radio
to achieve differential electronically, you will have to build in
aileron differential mechanically. There are at least two ways to get
the job done. The first method is to offset the push rod attachments
to the servo output arm or wheel. Typically, you mount the servo in
the airplane and attach the push rods to the servo output wheel such
that the push rods are at the midpoint of the wheel. That is to say
if you drew a line from the attachment point of one of the push rods
over to the other push rod, that line would pass directly over the
output wheel attachment screw. That arrangement will result in
exactly equal push rod movement in both directions; i.e. the same
amount of up and down. To get differential, move, equally, both push
rod attachment points around the wheel toward one another such that a
line drawn between the two attachment points would fall either above
or below the wheel attachment screw. The direction and amount you
offset the push rod attachment points depends on the effect you are
trying to get and the configuration of your airplane. Keep in mind
the above example with the Cub when thinking about whether or not you
want more up than down aileron.
The second method the achieve differential is by offsetting the
control horn or torque rod attached to the aileron itself. If you
looked straight on to the end of the aileron with the horn or torque
rod attached, and that control horn or torque rod is exactly
perpendicular to the aileron cross section, then equal fore and aft
movements of the push rod attached to the control horn will cause
equal up and down movement of the aileron. However, if you were to
cant the control horn either forward or aft as opposed to a
perpendicular installation, then equal fore and aft movement of the
attached push rod will not result in equal up and down movement of
the aileron. Again the direction and amount of the cant is dependent
on the effect you are trying to achieve.
Try messing around with this effect, you may turn a dog into a pretty
good flyer. By the way, this identical approach works with elevator
set up. Ever had an airplane that requires more down than up elevator
to respond the same whether upright or inverted?? Differential
elevator will fix this such that your transmitter sticks won't know
there is a difference.
Model Doctor #61
I don't want to be accused of labeling the Ol' Model Doctor as really
sneaky, but......
Doc keeps the remains of one of his most monumental crashes out in
the back forty and out of sight. When he is angling for a new kit in
the household budget, he carts the remains off to the flying field
for the day (loading up the car when no one is looking). When he
returns home that afternoon, he ceremoniously drags these same
remains through the house; acting real sad and heartbroken. After
several days of moping around, Mrs. Doc can't stand it anymore and
tells him to order up another!
I am told it works every time, as long as you remember to brush off
the cobwebs and dust first. The one time the Doc forgot.....well, you
know that limp he has?
Model Doctor #62
A broken metal engine mount or similar member can often be repaired
and returned to original strength with a product called J.B. WELD.
This is a type of epoxy that is very strong and will withstand high
temperatures. Use in accordance with the directions and you won't be
disappointed. It is available at most hardware and auto parts stores.
Model Doctor #63
Scott Morasci has found an easy way to cut complicated designs and
numbers from both trim Monokote as well as regular Monokote. He draws
out the design on paper and cuts out the paper to create a full sized
pattern for the design. Then, using spray adhesive, he sprays the
Monokote backing with adhesive. The adhesive will grab the full size
paper pattern (make sure you lay down the pattern in such a way that
the cut out Monokote comes out correctly). Cut out the monokote with
a new #11 Xacto blade. Setting the Monokote on a glass surface also
helps with clean cuts. When the design is cut out and you peel the
Monokote backing off, you get a piece of Monokote faithfully
duplicates your design and, you also end up with a reusable pattern.
Model Doctor #64
Here's something you might want to watch out for the next time you're
walking around a flea market. Latch on to a child's wagon, similar to
the old Radio Flyer wagons sold at most toy stores.
At a recent contest, I saw a fellow who had taken a child's wagon
(aka Radio Flyer) and designed a nicely finished, plywood field box
to fit within the confines of the wagon's cargo area. This included
provisions for starting battery, fuel, parts, paper towels, etc; i.e.
all that stuff you normally take to the field with you. Since there
was substantial surface area inside the wagon, the box did not have
to be very deep to accommodate all the "stuff" you need in
a field box. In addition to this nicely compartmented field box
inside the wagon, the field box was made such that at each corner of
the wagon there was a receptacle that would firmly grip a 3/4"
PVC pipe. He would then "plug in" a cradle fabricated from
PVC pipe that was designed to hold whatever airplane he brought with
him, at what ever height above the wagon he wanted it to be.
Obviously, a universal type cradle design would accommodate many
types of aircraft, while a specific design might be required for some
kind of trick scale aircraft. In addition, there is no need to glue
the entire cradle assembly together with the PVC glue. Depending on
how collapsible the cradle needs to be; you can drill, then pin
(screws with wing nuts) many of the joints together so you can easily
store the cradle inside the car. Remember to mark (color code) the
parts in such a way that you can quickly assemble it at the field.
Anyway, with his set up all he had to do was lift the wagon out of
the car, plug in the cradle, set the airplane on the cradle, and roll
the whole kit and caboodle out to the pits. Similarly, when it was
his turn to fly, the whole thing, airplane and all, rolled easily out
to the flight line.
Model Doctor #65
Have you had to bend any brass tubing lately? Oh, I know about the
various size spring sets you can buy that assist you in making a
smooth bend, but what if you don't have a spring, or can't find it,
or whatever? Here's what I found. Closely wrap the section to be bent
with soft wire, like bailing wire. You'll be able to make a nice,
almost kink free bend. Just unwrap the wire when you're done. Don't
have any soft wire you say? Try stout twine like a mason's twine.
Model Doctor #66
Here's how Elmer Hanes Jr. attached a clever water rudder to his
Eagle 63 for float flying. Elmer simply drilled a hole completely
through the fuselage just forward of the vertical fin. Into this hole
he glued a piece of inner Nyrod tubing which was long enough to stick
out both the top and bottom of the fuselage about an eight of an
inch. A piece of music wire with a brass rudder soldered on, a nose
wheel steering arm, and some wheel collars attach the rudder assembly
to the fuselage through this plastic tube. A linkage wire with
adjustable clevis connecting the steering arm to the airplane's
rudder control horn are all that is needed to put you in business.
All very neat and simple, and the neatest thing is how easily it is
removed for going back to land flying.
Model Doctor #67
From the Northeast Sailplane Products catalog comes this hint. To
remove epoxy from yourself safely, use white vinegar. It's safe,
cheap, and, of course, smelly. However, for approximately two thirds
of the modelers that the Doc knows, the vinegar odor would be an improvement.
Model Doctor #68
Tired of stripping servo gears when something bumps the control
surfaces on your plane? The answer is a inexpensive, effective
restraining device from John DuGrosse. Take spring loaded, wooden
clothespins and epoxy two pieces of 3/4" X 2" X 1/8"
thick lite ply (one to each side) to the clothespin jaws to form a
clamp. To use, simply clamp over the control surface and it's mating
fixed surface to immobilize the whole system.
Model Doctor #69
Quit guessing at the setup of you airplanes. John DuGrosse has
designed an accurate deflection degree indicator that can be
fabricated from scrap found around your shop, and maybe a quick trip
down to the drug store. All you need is a clothespin, a plastic
school type protractor, some brass tubing, screws and a fishing weight.
Start by drilling a hole in the protractor exactly at the zero by
ninety degree center axis. The hole should be sized such that you can
just slip in one of those brass eyelets that come with your servo
mounting grommets. Peen the small side of the eyelet over the
protractor plastic to keep it in place in the protractor. Take a
three inch long piece of 1/8" brass tubing and flatten the
center section over a length of about 1/2". Drill a #44 hole
(i.e. the right size for a 2-56 screw) through this flattened
section. Take a small size of music wire and solder it into one end
of the brass tube. This music wire will be the pointer to read
against the protractor, so you may want to file a point on to the end
if the wire. The distance between the hole drilled into the brass
tube and the end of the pointer wire should be slightly less that the
distance between the hole drilled into the protractor and the outside
edge of the protractor. Solder the other end of the brass tube to a
lead weight. John used a one ounce fishing weight, but the less
weight you can get away with, the better. The amount of weight
required will depend on the freedom of movement when the pointer
assembly is attached to the protractor. Attach the pointer assembly
to the protractor using a 2-56 screw, flat washers and either
Locktite or a jam nut to keep everything in place. Set the protractor
on a known level surface, such that the pointer can move freely, and
bend adjust until the pointer is at the ninety degree mark on the
protractor. Take a standard wooden clothes pin and cut about a half
an inch off of one leg. Cut a groove on the outside of the long leg
about one to two inches long. Epoxy one side of the protractor into
this groove.
To use, simply clamp the device on to the horizontal surface to be
adjusted. For example, after a trim flight, set the airplane on a
suitable surface and clip the indicator onto the control surface.
Read the degrees deflection on the protractor. Reset the transmitter
trim to its center position, and then adjust the clevis until your
previous deflection reading is obtained.
Model Doctor #70
A very non-messy way to keep epoxy out of hinges, is to cut small
rectangles of discarded backing from those iron-on coverings. Cut a
small slit in the plastic so it will slip over the hinge, pushing it
right up against the hinge knuckle. Apply the epoxy to the hinge with
a toothpick, then slip the hinge in place. After the epoxy has set,
tear the plastic strip out, then cut a new piece to be used when
attaching the control surface.
Model Doctor #71
The ol' Model Doctor has a helicopter rule of thumb, in spite of
having two left thumbs. If the tail boom shakes, the imbalance is
likely in the rotor head assembly. If it is the landing skids that
shake, the imbalance is likely in the engine fan or clutch assembly.
Model Doctor #72
If you turn a beer can upside down, the concave end of the can makes
a nifty epoxy mixing bowl. If you are worried about shaking up the
can contents, the Ol' Model Doctor runs a free beer can emptying
service just to make life a little easier for all Gold Country Flyers members.
Model Doctor #73
Try drilling a hole in the handle end of your small Xacto knife
holder. Thread a key ring into this hole. Now you have a knife that
won't roll off the work bench and has a built in hanger, as well.
Model Doctor #74
Are you getting tired of your CA glue nozzle always plugging up? Try
this as an easy solution. Tie a piece of string about 12" long
solidly around the neck of the glue bottle. Tie a loop about one inch
in diameter in the free end of the string. Now, when you are through
applying glue, twirl the bottle around with your finger in the loop
of the string. Centrifugal force will push the glue out of the nozzle
and back into the bottle.
George Reverman
Model Doctor #75
From Charles E. Snyder of Brandywine, MA comes an idea that should be
of great help to all model builders. To keep fiberglass cloth or tape
from unraveling and making all those nasty, loose threads, try
spraying the part to be cut with spray hair set. It dries in seconds,
does not get too stiff to work with and makes a nice clean edge. In
addition, he has found it to be compatible with all adhesives and coatings.
Model Doctor #76
I have recommended using "Goop" or "PFM" in the
past and I still do. However, I have found it is often a little too
thick to use. Here is the proper way to thin these miracle adhesives.
It can be thinned by using Toulene or Xylene available at your local
hardware store. Be frugal, it only takes a little.
Model Doctor #77
Bob Barnett came across a nifty way to reinforce ABS plastic parts
(cowlings, wheel pants, etc) that are supplied with most kits now
days. The Ol' Model Doctor has previously talked about using
fiberglass and resin, and SIG Celastic as ABS reinforcements. Bob's
method uses fiberglass cloth and the blue ABS cement found at most
any hardware store. The blue cement is the same stuff that you use to
glue your lawn sprinkler pipe together. Simply lay the cloth inside
the ABS part then paint on the blue goo. Let the glue set up and
you're ready to go.
Model Doctor #78
Need something to act as a wheel chock when you are transporting your
model around in the back of the pickup truck? Try taking a toilet
paper or paper towel cardboard tube and cutting in a hole large
enough to accommodate the model's wheel about mid point of its
length. Makes an excellent (and cheap) wheel chock.
Model Doctor #79
For those of you who still use rubber bands to hold down the wing
(ugh!!), try this. When you get the wing mounted and all the rubber
bands you need over the wing, put one more rubber band on the rear
dowel going across the fuselage (not back over the wing). Now, when
you are done flying for the day, slide your hold down rubber bands
off the front dowel. This rear rubber band will keep the others from
flying all over the place.
Model Doctor #80
Getting a foam rubber wrapped fuel tank slid into a narrow fuselage
is sometimes cause for using less than polite language. To make this
seemingly impossible task an easy job try this. Save the clear
plastic backing that comes with Monokote (and almost all other shrink
coatings). Wrap your fuel tank with foam rubber as you want it to end
up in the fuselage. Now tightly wrap the clear plastic around the tank/foam
rubber; so tight as to compress the foam rubber as much as possible.
Now slide the tank/foam rubber/clear plastic into the fuselage. Once
in place, pull the clear plastic out and the foam will expand to
tightly fit the tank in place.
Model Doctor #81
Did you ever have a problem where your wire landing gear seems to get
weaker and weaker. A possible solution is to remove the gear from the
airframe and remove all the hardware from the gear wire (i.e. - the
wheels, collars, pants, etc). Preheat your kitchen oven to 450 F
degrees. Place the wire on a cookie sheet in the oven for one hour.
Turn off the oven and let the gear and the oven cool down together.
Don't try to speed up the cooling process! What you have just done is
to re-temper the music wire and you should have put new life into
that old gear. Note that soldered joints should not be harmed as
solder doesn't melt until about 700 F degrees.
Model Doctor #82
Installing cable pushrods for the throttle linkage has its
advantages. One of them is that it doesn't have to be an exact
length. It can be cut long and still serve well. The cable will flex
when pushed forward and not cause a bind at the servo.
Model Doctor #83
If you have trouble cutting a cable without fraying it try melting
some solder into the area you wish to cut. When hardened, use a
Dremel cut off wheel to get a perfect cut.
Model Doctor #84
Want a cleaner running and looking engine? The ol' Model Doctor sez
to put about three ounces of automotive fuel injection cleaner into a
gallon of fuel. It is said to remove varnish and carbon from the
engine. Will it harm your engine? We don't know; however, the Ol' Doc
has been drinking it over ice cubes for years now. He shows signs of
just a minimal amount of varnish and carbon.
Model Doctor #85
Looking for an inexpensive alternate to dope thinner? The
manufacturer of paints used on most race cars, PPG, has a product
labeled as PPG 876 that works well.
Model Doctor #86
People who have tried it claim that Formula 560 is an excellent
canopy glue from the makers of ZAP. It is supposedly better than the
old standby RC 56, which has been the standard up to now.
Model Doctor #87
Proving once again that Ol' Doc can actually read (I know he says he
gets Playboy Magazine for the articles), he passes on that he read
somewhere that it take two #64 rubber bands for each pound of total
aircraft weight. Therefore, a six pound airplane would require at
least six rubber bands on each side of the airplane to properly
secure the wing, if you follow this theory. Be sure to account for
the weight of a full fuel tank and the weight of the extra electrons
of a fully charged battery.
Novices will often tend to orient their aircraft perpendicular to the
ground with the hope that their instructor will save the day. The
pull out from such an attitude will stress the wing hold down rubber
bands to the limit.
Another way to determine if there are enough rubber bands (aside from
the test procedure mentioned above) is to install six or eight bands
on each side. The holding the fuselage directly in front of the wing
(usually just above the fuel tank bay) attempt to lift the wing up
from the saddle. Use a fair amount of force in this test. If you have
enough rubber bands, the wing should not move at all. In most cases
using new rubber bands, you should not need more than eight to a side.
Model Doctor #88
Have you lusted over one of those really spiffy transmitter cases
advertised by Tower Hobbies and others? Well, you can achieve the
same utility at about one forth the cost by using a plastic or
composite brief case. I have seen these at flea markets for just a
few dollars and they will easily hold two transmitters. You can get
them new at a large office supply store for less than $20. The next
problem is to get the foam rubber cut out to the shapes you need to
fit the brief case and the transmitters. The foam can be obtained at
any furniture upholster's shop or craft store. Cutting the foam so it
looks like a professionally cut piece is easy...if you have an
electric carving knife. Yep, the same thing that carves up Tom Turkey
does a first rate job on the big slabs of foam. Anyway, I ended up
with a two transmitter case that can take being bounced around in the
trunk of your car without breaking off those tiny transmitter rate switches.
Model Doctor #89
Dubro makes a fitting set for the purpose of setting up a one gallon
fuel can for easy attachment of fill and vent tubing. This same
fitting set can be installed in that red plastic inner seal that
comes with most plastic bottles of fuel. Punch two holes in this
plastic seal, just as you would in setting up the cap of a metal fuel
can. Install the pick up fuel line and filter, and vent fitting in
the same way you would with a metal can. Now, use a very short piece
of fuel tubing to hook up the filler piece that come with the DuBro
fitting set. That way you can plug the filler piece into the vent
hole of the fitting set AND still screw the plastic bottle cap onto
the bottle, thereby sealing in the entire filler system and the fuel.
The whole thing ends up more air tight than the metal fuel can
version for the same amount of work, and can be easily transferred
from one bottle to the next.
Model Doctor #90
For those who read my misfortunes while painting the Bucker Jungmann,
here's a tip that might have help. You can remove masking tape with a
lessened chance of pulling up the paint if you heat the tape with a
heat gun as you pull the tape. Just a little heat is all that is
needed; don't overdo it. Also, pull the tape back over itself when
you are removing it to further reduce the risk of pulling paint up.
Model Doctor #91
If you have a "favorite" or otherwise standard fuel can you
use in your flight box, then you routinely transfer fuel from one can
to another. While you are doing this transfer, it is the perfect
opportunity to make sure you are using only the cleanest of fuels.
Put a "Mr. Coffee" or similar coffee filter in the funnel
you use for the transfer for super fine filtration of the go juice.
Howard Smith
Model Doctor #92
It has become very popular to use multiple servos for single control
functions. For example, splitting the elevators using a separate
servo for each side for control redundancy, or utilizing one servo
for each aileron to eliminate complex linkages are now commonplace.
For those of you that follow this practice keep in mind that your
receiver expects a certain power draw for each channel. When you
utilize a "Y" connector to connect two or more servos to a
single channel, you increase the power draw at that channel
substantially. Further, if you start doubling up servos and those
servos are the big quarter scale variety, and then use long servo
leads, then put the whole mess under flight loads, you can overload
the power output section of your receiver and cause component
failure. Such a failure is usually immediately followed by the crash.
How do you know when you've put too much power output load on any one
channel? I don't know. The power draw can be measured easily enough
with a ammeter, but the receiver specs with respect to max power
output from each channel are generally not available. I do know that
I have had a mysterious servo drift problem with two large servos on
a single channel go away when I pared the channel down to one servo.
Modern computer radios ease this problem by allowing you to use two
separate channels for the same control by mixing them together on the transmitter.
Keep this in mind as a possible cause if you are getting inconsistent
performance for you radio system.
Model Doctor #93
There are a variety of methods to prevent airborne battery pack
connectors and servo extension connectors from coming apart. The
neatness of you radio installation has a lot to do with the
susceptibility of your system for such a catastrophe. There are
commercially available plastic clips, and the old stand by - plastic
tape. Here is a new twist: Slide a piece of 3/8" or 1/2"
heat shrink over one of the pig tails, then push the connector
together. When satisfied, slide the heat shrink over the connection
and shrink it down with your heat gun. The connector will never come
apart and the installation looks very neat. The heat shrink can be
easily removed with an Xacto knife.
Model Doctor #94
Neatness counts in your radio installations beyond just the
appearance of your handiwork. Neat installations make maintenance and
trouble shooting much easier, and they are far less prone to
accidental damage (i.e. squeezing wires between the fuselage and
wing, nicking a wire with a screw, etc.).
A standard for radio installations has been the use of the nylon pull
ties used in the electronics industry for bundling wire runs to keep
servo pig tails out of the way. These are especially prevalent in R/C
helicopters. However, these pull ties are rigid and tend to have
sharp edges. Coupled with the vibration of the plane (worse yet in a
helicopter), the pull ties have been know to cut right through a
servo lead.
A better alternative is available from some motorcycle shops in the
form of one foot long, 1/2" wide Velcro strips. These strips are
double sided in that the fuzzy stuff is on one side of the strip and
the velcroie stuff in on the other side (I's proud of my ability to
use technical terms). These strips can be used in the same manner as
the pull ties, but are much softer around the wires.
Model Doctor #95
Do you wear glasses? Do you spray paint your models? The next time
you do both at the same time, try this. Stretch a piece of Saran Wrap
over the glasses using some Scotch tape to hold it in place. Now,
when you are done painting simply peel off the Saran Wrap and you'll
have glasses that you can actually see through.
Lowcountry R/C Flyer
Model Doctor #96
by Brooks Goodnow
Drill a small hole in the ferrule of your new paint brush and drop
some CA in it. Now you won't lose nearly as many bristles on your work.
Model Doctor #97
by Brooks Goodnow
After doping, rinse the paint brush with thinner until clean, then
wash the brush with warm, soapy water. Squeeze dry with a paper
towel. Place the brush(s) in a jar, handle down. I use an old
mayonnaise jar. You'll find that when the brush dries, it will be
soft and with no paint or thinner to harden the bristles.
Model Doctor #98
by Bob Hatschek
(a greatly condensed version of his article in the FLYOFF)
Everybody seems to have a secret on keeping CA adhesives usable for
long periods of time. One of the most popular is to store the CA in
the refrigerator. However, the answer may really be simply keeping
moisture away from the opened container. Bob does this by storing the
opened CA bottles in a plastic baggie that has silica gel desiccant
bags included. The silica gel keeps the moisture out and the CA
flowing..... Oh yea, the silica gel can be revitalized by baking in
you oven.
Model Doctor #99
A good surface to use for mixing epoxy is a notepad. After each use,
the top sheet can be torn off, and the surface is ready for the next
use. These notepads usually can be obtained for free as advertising
from local businesses. For mixing sticks, there are a myriad of sizes
and shapes available from craft and hobby stores for building
"toothpick" models. They come in a large bag for a
reasonable price. (Most common toothpicks are too small for most R/C
use, and Popsicle sticks are kind of large.) I have found these two
tips to be the most convenient and mess free way to deal with epoxy.
Mark Kallio
Model Doctor #100
The easiest way I have found to epoxy hinges in control surfaces and
be sure to get the glue to fill the hinge slot is to use a plastic
drinking straw as a disposable "hypodermic". Flatten the
end of the straw between your fingers and test fit into the hinge
slot so you will get the hang of inserting it. Then mix your epoxy,
scoop some up in the end of the flattened straw, insert it into the
slot, and "milk" the epoxy into the slot. You can then wipe
the outside of the hinge slots off before inserting the hinges. This
assures that each slot is filled with epoxy. I then like to take a
small drill and drill though the control surface and pin the hinges
with a toothpick. The toothpick should then be cut off flush, and a
small piece of covering placed over the pin. These are only
noticeable upon close inspection, and the benefit to the control
surface is substantial.
Mark Kallio
Model Doctor #101
I came across a great way to cut hinge slots in wings and control
surfaces. In the Bottom of my toolbox I found a circular saw blade
with a hole for a 1/4 inch mandrel. I am sure there are many sources
for such a blade at your local hardware store. Using a 1/4-20 bolt as
a mandrel, I chucked this into my drill press. You should then
"square" the blade to the table of the drill press (the
markings on the drill press are usually not accurate enough for this)
by setting the blade flush on the table and tightening it down. Then
set the depth you want for the hinge slot. This cuts perfectly
aligned hinge slots of the right size for pinned hinges. I have tried
a lot of methods for cutting hinge slots, different jigs, etc., but I
haven't found anything that works as well as this.
Mark Kallio
Model Doctor #102
Ever had trouble peeling the backing from mylar covering material? I
certainly have, especially with the lower temp coverings. The easiest
way to prevent a nervous breakdown trying to peel this stuff is to
use two pieces of masking tape. At a corner of the mylar, stick a
piece of masking tape on the front and back of the covering , with
about half hanging over the edge so that the pieces of tape stick
together past the edge of the covering material. Then peel the two
pieces of tape apart, and presto! the backing peels right off. Happy covering!
Mark Kallio
Model Doctor #103
This month's tip shows you one of the most useful and inexpensive
tools in my workshop. They are simply pieces of scrap aluminum angle
iron cut to various links and of various sizes. I find that a
selection of 1", 2", and 3" pieces varying in length
from 1" to 6" to be quite helpful, and these can be
obtained at a metal supply shop. If you have a metal fabricator near
you, you might try asking him to sell you some scraps of angle about
these sizes. Since these lengths are considered trash to these
fellows, you may get lucky and get them for free. Even if you don't,
the cost should be minimal, and as useful as these are I would have
purchased new stock and cut it up into pieces to obtain these tools.
What good are they, you ask? Well, here are a few of the things I use
them for, and I 'm sure you can come up with more once you start
using them. First off, this is a great way to align the table on
disk/belt sanders, drill presses, band saws, etc. You can use them to
hold items to be glued or drilled exactly perpendicular to the work
surface, such as drilling into the edge of sheeting, or holding ribs
at 90 degrees to the table while your adhesive dries.
Mark Kallio
Model Doctor #104
An easy and cheap way to obtain an instrument panel for that sport
model is to look through a full-size plane magazine for an
advertisement showing instruments. I found one I liked and used my
scanner to scan the image into the computer, and then pasted It into
my word processor, scaling it to different sizes. This could also be
done using a copy machine that will reduce. If using the computer,
any size can be easily scaled, and I printed out several different
sizes to have on hand. The ones I did were all in black and white,
but if you have access to a color scanner and color printer, some
really nice instrument panels can be made this way. One could also
add color to black and white copied instruments using markers or
colored pencils for even more realism. Shown is one of the planes
that I have installed these instruments in. An instrument panel
really adds a finishing touch to any model. Happy Modeling!
Mark Kallio
Model Doctor #105
Curving Balsa
Get some ammonia, found in the household section of the supermarket.
Put some in a spray bottle, and spray both sides of balsa sheet
liberally. Carefully bend the sheet to the right shape. You can even
tape it to a form, such as aluminum soda cans, and let it dry. Once
dry, it may be used as turtle-decks, etc.
From Jeff's R/C Aviation Web Page
Model Doctor #106
Wing - Tail Alignment
Get an old (but straight) telescopic antenna, the same type as on
transmitters. Use it as an adjustable-length measuring rod to compare
critical measurements on planes during construction. I use this idea
to compare the distance from one wingtip to the stabilizer, and to
make sure this distance is equal on both sides of the plane. This
ensures that the stabilizer is parallel to the wing.
From Jeff's R/C Aviation Web Page
Model Doctor #107
Here's a flying tip for new pilots:
Something to pay attention to when learning to fly is control
reversal. Control reversal is when the inputs on the transmitter
sticks must be reversed when your plane is flying toward you, rather
than away from you. When flying away from you, there is no problem,
just move the stick in the direction you want to turn. Many new
pilots become Disoriented when their plane is approaching them. To
help with this, move the stick in towards the low wingtip. This will
level the wing when your plane is coming toward you, avoiding a sharp
bank, and possibly a crash.
Example: Say your plane is coming toward you, and the right wingtip
is low, as if banked to the right. Move the stick to your left,
toward the low wingtip. This will bring the plane's right wingtip up,
and level the wing. In other words, when landing just tell yourself
"push it up" as you always move the stick in the direction
of the low wing.
From Jeff's R/C Aviation Web Page
Model Doctor #108
Installing Triangle Stock
For me, triangle reinforcements have always been difficult to handle
due to their shape, especially if they're coated with epoxy. Try
sticking your Xacto knife loosely into one end of the triangle. Then
lay it on the bench so that the wide part of the triangle (the
hypotenuse) is against the bench top. Now apply the epoxy or other
adhesive to the sides that will contact the airframe. Next, by using
the knife handle, insert the triangle into position in the airframe.
Press down with your finger onto the wide side that has no glue, and
carefully slide the knife out of the piece. This way you can cleanly
install triangle stock, and not get any glue on your fingers.
From Jeff's R/C Aviation Web Page
Model Doctor #109
Sandbag Weights
Fill plastic zip-lock bags of various sizes about 3/4 full of fine
sand, and seal each well. Use these to hold down large parts while
building, such as wings. The sand will conform to the shape of parts
well. They also work good when gluing sheeting to foam.
From Jeff's R/C Aviation Web Page
Model Doctor #110
Cutting Balsa
When cutting a piece of wood with an Exacto knife, draw the knife so
that if gets "caught" by the grain, it will go towards the
scrap piece of material. This should always be done even with the use
of a straightedge as the knife could be drawn towards it and possibly
push the straightedge out of alignment.
From Jeff's R/C Aviation Web Page
Model Doctor #111
Servo Holes
When trying to install a servo in a plane, try this clever idea.
Often, the cramped quarters inside your pride and joy doesn't leave
enough room for a standard size drill. Use a standard Exacto handle
with a 1/16" drill bit installed (yea, it will fit). The pilot
hole can now be drilled by turning the handle and will make an
acceptable hole for the servo mounting screw.
From Jeff's R/C Aviation Web Page
Model Doctor #112
Installing Easy Hinges
When installing CyA hinges, mark and slot balsa as you normally
would. First, cut approx. 1/8 inch off the out side corners at 45
degrees so that the hinges go in easier. Then take a T-pin and insert
through the hinge at the center so that the hinge can be pushed in
only half way into the surface you are hinging. This keeps the hinge
from being pushed too far into only one surface. once the control
surface is in place, then remove the T-pin. Take your thin CyA with a
small applicator tube and place 2 to 3 drops onto each hinge while
keeping the surface pushed tightly against the trailing edge. It's
best to do the two end hinges prior to gluing in the interior ones.
Flex the control surface slightly and the CyA will soak right in.
While you have it flexed, add 2 or 3 more drops on each hinge. As
long as the CyA is being wicked in, you're OK. Do not put on any more
than this or you will have it all over the MonoKote and your fingers.
If this does happen, better have a real bottle of debonder handy.
From Jeff's R/C Aviation Web Page
Model Doctor #113
Installing Radio Gear
As a general rule while installing radios and servos, keep all weight
forward. Most all airplanes have a short nose moment. For example, to
balance a nose heavy aircraft, 1 oz. at the tail could be all it
needs. While the same aircraft, being tail heavy, could take as much
as 10 oz. or more to balance. It's a lot easier to add a little
weight to the tail than a ton of weight to the nose. The best thing
to do when you're unsure, is to temporarily place the battery,
receiver and servos in place and check the C. G. without adding dead
weight. But don't forget to check that lateral balance as well. It's
best to check this prior to covering and after all radio gear and the
engine are installed. In this way you can add small amounts of weight
to the extreme tips of the wing, reducing the overall
"balancing" weight greatly.
From Jeff's R/C Aviation Web Page
Model Doctor #114
Fiberglass Hint
How do you get the creases or lumps out of the fiberglass cloth we
use to reinforce the center section of the wing? This method will
completely eliminate them. Prior to applying the fiberglass cloth to
the center section of the wing, take the time to iron it flat with
your clothes iron. This will make it soooooo much easier to achieve a
FLAT surface. Next, place the glass cloth or the center of the wing
and tack it down to the surface with one drop of CyA (each corner,
top and bottom). This may require that you may have to pull the cloth
taught, but don't overdo it! Now you should have the cloth resting
smoothly on the top of the wing. Now apply the resins (or CyA) over
the cloth. You may find that after 3/4 of the cloth is attached that
you now have puckers along one edge or the other, but this is easy to
fix. Lift the material where you tacked it to the wing (remember I
said to tack it down, not permanently attach it), pull taught, and
tack it down again. There you have it!
From Jeff's R/C Aviation Web Page
Model Doctor #115
Polish that Gear
Have you ever found that the aluminum landing gear that came with
your new pride and joy looked so ragged that you either want to paint
or replace it? Here's a way that will not only make it look better
than new, but will take less than 30 minutes! First you'll need the
following materials:
400 to 600 grit Wet-or-Dry Sand Paper
Emery Cloth
Twinkler Silver Polish
Aluminum "Mag Wheel" Polish
If your landing gear looks really crappy and has allot of scratches,
the first thing you'll need to do is to wet sand the aluminum (sound
a little strange, but this goes pretty quickly). Keep your sanding
strokes long and lengthwise along the gear. After most of the
scratches are gone, the next step is to go over the landing gear with
the Emery Cloth (don't wet sand with Emery Cloth, use it dry!). Just
as you did earlier, keep your sanding strokes long and lengthwise
along the gear. Now wipe down the gear to remove all the dust and
crud. After that, apply the Twinkle silver polish and buff. Don't try
to get the gear to shine at this point, that will come after the next
step. Now go over the gear with the Emery Cloth lightly, this will
bring the aluminum to it's optimum sheen this is the real/ trick, and
I must admit was discovered by pure dumb luck). As a final step, go
over the gear with the Mag Wheel Polish to protect the luster of the aluminum.
You'll be quite amazed at the looks of your "NEW" gear, as
I was when I did this last week. The only draw-back to this process
is your fingers will get a little dirty (OK, really filthy!) because
of the aluminum dust, BUT I'm here to tell you, the finish looks stupendous!
From Jeff's R/C Aviation Web Page
Model Doctor #116
CyA Tip Clogs Unstuck
One of the real hassles of using the gap filling CyA's is, as always,
the clogged tip on the bottle. As everyone who uses it knows. even
with the best of techniques, the nozzle gets clogged long before the
CyA is gone. There are several ways to solve this problem.
1. Cut off the tip. Now you are rid of the clog and with that
1/4" hole in the end of the nozzle the CyA is really easy to get out.
2. Drill out the tip. Same as above but now you also have a drill
that is full of glue.
3. Throw the bottle across the shop and go get a new one. of course,
if it's 11:30 on a Friday night you can kiss off wowing them with
your new Belchfire 60 at the field Saturday.
Here is a solution that will work. Buy a package of extra tips and
don't mutilate the tip when clogged. Instead, put it in a tightly
capped jar (baby food or olive oil), filled with acetone. Acetone
will dissolve the CyA and will not affect the nozzle. The next day it
will be as good as new. Make sure the tip is dry and free of acetone
before installing on the bottle. Remember, acetone is a fire hazard
so treat it as such.
From Jeff's R/C Aviation Web Page
Model doctor #117
In our hobby we need lots of knickknacks with which to build our
models, and some things are not often found in model shops. For
example, do not throw away broken Tx aerials, or any other extendible
antenna which comes with portable radios. This contraption offers an
excellent variety of thin brass tubes which are very useful for
bushes, small pushrods, tubing, guides, etc.
Model Doctor #118
If any of you build models from scratch or from a plan, you will know
how tedious it is to copy ribs, formers, etc on to wood. I found an
excellent way of doing this. You make a photocopy of the part you
want to copy, dampen the paper with some cellulose thinner, place the
paper on the wood facing down and iron it with an electric iron and
hey presto, the ink from the photocopy is transferred to the wood.
Model Doctor #119
Nowadays it is common practice to seal our balsa covered models with
laminating epoxy only (without any cloth) before painting. A lot of
elbow grease is needed, however, to smooth down the resultant
surface, and most of the time a second coat would also be necessary.
For flat surfaces or straight curves (not compound curves) I have
solved this problem and eased the process. After applying the epoxy
place a smooth piece of plastic large enough to cover the whole area
and without any creases over the surface, and smooth it out so that
no creases appear. This may be a bit tedious, but you will get used
to do it quickly. Remove any surplus epoxy that oozes out from the
ends and leave overnight. When cured, remove the plastic sheet and
you have a very smooth surface which needs a minimum of sanding.
Needless to say, you can only do, for example, one surface of a wing
at a time. While acknowledging the fact that there are other more
sophisticated ways of achieving a smooth finish without too much
sweat, I think this method is cheap and easy. What is actually
happening is that the surface tension of the epoxy keeps it on the
surface of the wood and as a result does not seep into the grain,
leaving a glassy cover over the wood - just what you need! Again,
attention must previously be given to producing a very smooth
surface, otherwise the -results weal! -not -be-good.
Model Doctor #120
A lot has been said in the magazines on how to produce miniature
rivets on scale models. One method which I have never seen is the use
of those subminiature circular pieces of paper that fall out from a
Telex machine!! I am aware that Telex machines are rapidly going out
of existence, but if you ever saw one, you will note that it has a
yellow and narrow strip of paper in the form of a roll which is
punched with miniature holes (two sizes) while the machine is working
- the tiny pieces of paper are perfect as scale rivets on normal
sized scale models. Putting them on the model is another matter, as
it needs quite a bit of patience - I use a small modeling pin to get
hold of each of them, and dip each one of them in diluted PVA glue -
thirty rivets is the maximum I could manage in one session!!!!
Model Doctor #121
When you rig up your fuel tank in your model, the usual practice is
to use three outlets, one for the feed, one for filling and emptying
(which end must be at the bottom of the tank) and another to act as a
vent (which end must be at the top of the tank). Although when using
two outlets only this idea is not so useful, it can also be used.
Instead of bending the brass tubes so that their end is at the top or
bottom (making it very awkward to insert the rubber plug) just bend
them slightly up and down and use a short piece of silicone tubing to
carry on to the top or bottom - it makes life easier!!!
Model Doctor #122
Broken or old and unwanted mains plugs and sockets, connectors, etc
can come in quite handy in our hobby. The British type of three pin
13 amp plugs and sockets are particularly useful when you need any
sort of collet for holding wheels in place or spacing your engine out
from the firewall. The smaller two pin ones, even those sockets for
bayonet type bulbs have small brass fittings which can be utilized
for many things in our hobby. I have also come across large broken
mains switches which have large diameter collets and large screws - I
have used a couple of these to restrict air flow in my pneumatic
retracts - a small piece of sheet brass or alum between the screw and
the pipe will minimize the risk of puncturing the air pipe.
Model Doctor #123
When aligning wings with fuselage, all kit instructions emphasize
accurate measurements generally from the wing tips to the end of the
fuselage, but fail to suggest how. I found a very handy tool to do
this job - your transmitter aerial!! Just extend it to the required
length on one sic and see if the measurement of the other side
tallies without varying the length, of course.
Model Doctor #124
Mike's Painting Tip
I am building a Midwest Cap 232. I am covering it with Ultracote deep
blue, turquoise, and white, just like the ad. Now it was time to
paint the cowl and wheel pants. Where do I get the paint that matches
Ultracote? So I came up with Chevron Perfect paint, and let me tell
you the perfect part is only a name. The blue was about four shades
off and the white didn't even match, not to mention they don't have
the turquoise. Oh well, every thing I've been doing on this plane has
come out rotten, that's why it hasn't been to Show & Tell.
Anyway, I went to Car Color in Salinas on Abott St. and brought a
piece of my covering. The guy scanned it in a photo-type of computer
of some sort, got the paint code, mixed the paint, and guess what?
Matches perfect; and to make things better they put it in a spray
can, a regular aerosol type, for nine bucks and it sprays like a
paint gun. Now I've got six inches of one color that matches. Oh
well, good luck and good painting.
Submitted by Mike Aliorri Salinas Area Modelers
Model Doctor #125
Here's a tip my buddy Jay and I just discovered. Please excuse if you
already have it.
I was unsatisfied with my World Models T-34 performance with a
OS-46LA, and wanted to upgrade to a OS 46FX. The footprint of the FX
is slightly larger than the LA, so I needed to adjust the engine
mount. While wrenching on it, I sheared the screw head off, and
conventional methods would not remove it. This was a typical screw to
blind nut through the firewall type installation, with Loctite. After
contemplation and consternation I knew that my last resort short of a
difficult removal and reinstallation of the blind nut in a very
inaccessible place would be to heat the screw shank. But how? A torch
or any other flame in the engine compartment is just asking for
trouble. Charred wood, burning epoxy, and other visions danced
through my head. Then Jay said, "how about a soldering iron
applied to the screw shank and heated to melt the loctite? No flame,
and it still gets plenty hot. " I heated it, applied a good vice
grips and unscrewed it with ease. I tried it, it worked, and it saved
me a whole lot of time and aggravation.
I hope this saves some other people time and aggravation.
Share as you see fit.
Chris Larson
Model Doctor #126
After a day of flying....take the oil/fuel covered rubber bands and
place them in a container containing "corn starch". Shake
em up good so that they are covered well. The corn starch soaks up
the oil and you'll have almost new rubber bands for that next flying
session. Snap them before securing that wing and you'll find
that most of the corn starch just flys off.....leaving a fresh rubber band.
Cheers, Bill Varney Fredericksburg Aeromasters |
