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Building Tips 'n' Tricks
This section of the S.A.M. Web Site is intended to provide information to both the new and experienced flyer in different aspects of the R/C aircraft hobby. Our goal is to cover all areas from building hints to pre-flighting an aircraft to flying and landing. The range of subject matter is probably unending, and only limited to articles submitted for inclusion.
If you have a particular subject matter you would like to submit, e-mail it to me at the following address:
WEBMASTER
MS Word format is preferred; however, other formats are acceptable. The following articles are available:
SPECIAL NOTICE: Permission is hereby granted to any AMA charted Radio Control
club to use the articles that appear in this section on your R/C Web Site, however
any article used must be used in its entirety, and credit must be given to the
author and to the Sacramento Area Modelers Web Site)
Pre-Flighting your aircraft
By Arno Clabaugh
During a Newbie Day Event (a day new pilots are invited to try flying their new trainers) while helping with pre-flighting of new trainers it occurred to me that an article on pre-flight would be most welcome to new builders and assemblers of trainer aircraft.
While some of the information I will discuss here can be found buried in various books on building RC planes, I cannot name or recall where a new builder can find just the information to make sure his plane is ready to fly. The purpose of this article is to provide information such so that little or no changes will have to be performed at the field prior to that first flight. Even so, a new pilot should have an experienced pilot preflight his plane if possible.
The first things I look at in a new plane are the servos. So let's start there. Check to see that all the servo mounting screws are there. Check to see that all the servo arm screws are there. It is very easy to forget one or more while removing the servo arms to connect the push rods. Next check to see that all pushrods are properly connected to the servo arms. This is a trouble spot for new builders who tend to use so called quickie or easy connectors to connect the pushrods.
These connectors make it very simple to adjust the pushrods wires but can result in the loss of a plane. Experienced builders only use these connectors on the throttle servo and steering gear servo. Reason being that the force of the elevator or rudder pushrod can dislodge the easy connector out of the servo arm. Some manufacturers provide a reliable connector so that only a ninety degree bend needs to be made on the end of the pushrod wire.
The most reliable connection is a Z bend of the pushrod wire.
Never use a clevis connector on both ends of a pushrod wire unless at least one is metal and soldered to the wire! Reason is vibration will unscrew the wire threads out of the clevis. Thus the best connections are Z Bends at the servo arms with a clevis connected to the elevator and rudder control horns.
Now take a look at the elevator and rudder clevis connectors. Almost always the kit supplier provides nylon clevis connectors. These are reliable connectors but can pop out of the control horns due to the stress of a hard turn or vertical maneuver.
An easy solution to this problem is to install a piece of fuel line on the clevis to prevent it from opening.
While there, check that the control horn screws are all there and are tight.
Now do the same checks for the aileron servo mounting screws, arm screws, pushrods, clevis connectors and aileron torque rod nylon brackets.
The next check is for the aileron, rudder and elevator hinges. Do a firm pull on all the control surfaces. If a hinge can be pulled out, be thankful that you did not fly your plane yet. One loose hinge will allow the vibration of the engine to break the remaining hinges of the control surface. I don't need to tell you what happens next.
Check the movement of your steering gear. It should turn left and right with the rudder movement. As mentioned before, a quickie connector is acceptable on the pushrod for steering a tri-gear airplane. You can use one on both ends if you wish but a Z-bend at the steering arm is more reliable. The quickie connector at the servo allows for easy adjustment of the wheel. Movement of the wheel should be just enough for a wide turn. Small movement makes it easier to steer during take-off and landing. It usually is best to have the steering wheel slightly shorter than the main gear. That helps to avoid hitting it first during landing. Finally check the main gear to see that it is well fastened to the fuselage. A slight toe-in of the main wheels will help the plane to track straighter down the runway.
Check the throttle connections and movement. Again a quickie connectors is okay on the servo arm for easy adjustment. A Z-bend is best on the throttle arm but if difficult a quickie connector will do. Theory is that if the connector does let loose it is not the disaster that would result at the rudder, aileron or elevator. Make sure that the throttle is moving in the right direction with the transmitter stick. With the stick at full throttle the carb should be wide open. When the stick is full down and the trim is full down, the carb should just be closed to allow engine shutdown.
Check the receiver, battery and fuel tank to see that all will stay in place during vertical or inverted flight. It is to your advantage to have them wrapped with foam rubber to minimize damage in case of a crash. Make sure your receiver antenna is stretched out as straight as possible for maximum signal reception. Do not wrap it back and forth as it will act as a shorter detuned antenna. It normally can come out the bottom or top of the fuselage. It is okay to hang down but can be easily stepped on.
Put the wing on the fuselage. Make sure the aileron torque rods do not interfere with the other servos. Check that the aileron servo is connected to the receiver aileron extension connector. Trainers usually use rubber bands to connect the wing to the fuse. Reason, during a crash or bad landing the wing can pop off with little damage. Not always. It is quicker and easier to make a repair to the fuse than the wing. If you multiply the weight of the plane by 1.5 and round that off to the next even number, you will have a good count for the number of rubber bands needed to hold the wing. Install the first two straight across, the next pair criss cross and continue to alternate.
Make a final check for the center of gravity (CG). Make sure the fuel tank is empty. It is best to have a slightly heavy nose. The saying goes that a tail heavy plane only flies once. Your high wing trainer will check for CG at the proper distant under the wing. When you advance to a low wing, it should be checked while inverted. The idea is to have the weight of the fuse under the wing while testing.
Check all controls for proper direction and amount of throw. With the aileron stick to the right, the right aileron should move up, left aileron down. For a left turn, left aileron up, right aileron down. With elevator stick towards your body, elevator should move up. With rudder stick to the right, rudder should move right and vise versa.
One final thought is to make sure you will not lose your engine muffler. I use high temp RTV on the pipe threads and a spot of CA glue on any nut or screw.
I am including a checklist so you will not have to re-read all this to assure you have checked everything.
It is best to have someone double check your preflight especially the first time. Experienced pilots continue to preflight their planes each time they bring them to the flying field.
I hope you find this information helpful. If it saves time at the flying site and makes your flying safer than I have accomplished my mission. Finally do not fly without help unless you have completed your solo flight. To do so is unsafe for others, yourself and can be very costly.
Preflight checklist
( ) SERVO MOUNTING AND SERVO ARM SCREWS
( ) PUSHROD CONNECTIONS AT SERVOS
( ) CLEVIS CONNECTIONS AT CONTROL HORNS
( ) CLEVIS FUEL LINE LOCKS AT RUDDER AND ELEVATOR
( ) AILERON SERVO MOUNTS, ARM SCREWS, PUSHROD CONNECTIONS,
AND CLEVIS FUEL LINE
( ) CHECK ALL HINGES WITH A FIRM PULL
( ) STEERING GEAR CONNECTIONS, MOVEMENT AND HEIGHT
( ) MAIN GEAR SCREWS AND TOE IN
( ) CARB CONNECTIONS AND ADJUSTMENT
( ) RECEIVER, BATTERY, FUEL TANK AND ANTENNA INSTALLATION
( ) WING RUBBER BANDS OR BOLTS
( ) CHECK CG
( ) CHECK CONTROL SURFACES FOR PROPER DIRECTION AND MOVEMENT
A Warning About Inverted Engines
By Arno Clabaugh
I have read or heard stories about engines firing up without a ni-starter. Usually the engine is still warm from running or sitting in the sun. The pilot turns the prop before connecting the ni-starter and suddenly the engine fires. Sometimes it just kicks over and sometimes it stays running.
This warning is about something that happened with me and I have never heard about it before. When I build or modify a model with a cowling, I like to invert the engine rather than install it sideways. In fact some models like an AT-6 I have, call for it to be inverted. It makes a cleaner front end for the aircraft.
Here is what happened. The aircraft had been sitting in the sun after filling it with glow gas. I don't prime my engines before starting so I did not turn the prop. I picked up the plane and connected my ni-starter. The engine fired, turned the prop two or three times and fortunately stopped! My transmitter was on and I always try to start with a low throttle first. If I had a higher throttle sitting, I believe the engine would have continued to run. If it had, I do not believe I could have held the plane.
I tried to analyze what occurred. Perhaps there was some gas in the piston chamber, the valves and piston were such that combustion could occur and the hot plug fired the gas. The engine on this plane is a Magnum four stroke XL52.
Connecting a ni-starter on an inverted engine is sometimes difficult. Many pilots just lift the plane while still in front of it. On my AT-6 with a wrap around cowling it was really difficult so I installed a glow plug extension to the side of the plane.
So, on that plane I still have to lift it, but I do it from behind. My new policy for inverted engines is to always install an extension for the glow plug. I shudder to think how many times I have helped my grandson start his P51 warbird with a YS-91 engine. He picks it up from behind while I connect the ni-starter in front. Never again!
I hope this helps to avoid an injury. Warbird racers do not like glow plug
extensions because they can be troublesome and difficult to remove in a hurry.
If the plane is held on the ground the danger is reduced. In my case, to look
through my bifocals I have to raise the plane.
Stronger Tail Feathers
By Arno Clabaugh
If you are a new pilot and have the help of a Sam's Instructor, there is a chance that your trainer airplane may survive all the way to and through your solo flight. Many times, however, there could be some minor or even serious damage that must be repaired before you can continue learning to fly.
Most damage occurs when you first start making your own take-offs and especially landings. It is difficult even for the instructor to save your plane when a mistake is made near the ground.
The weakest part on the airplane is the tail fin and stabalizer. Many times the plane just gets dumped upside down while attempting a take off or after landing. When this happens, the tail fin and the horizontal stabilizer can easily break lose and sometimes break out some of the rear fuselage. Usually the plane must be taken home and repaired, ending your flying for the day.
With a little effort and some balsa, you can prevent this minor damage. Of course if your plane goes in fast and hard it may not do any good.
Here's the way to beef up the fin and stab:
Install a piece of 1/4 inch balsa triangle on each side of the fin. Cut away about 1/8 inch of the plastic covering on the fin and the stab to expose the wood for the glue. It is best to use epoxy for maximum strength. Be careful not to use too much glue as to change the CG balance of the plane.
Turn the plane over and install triangles on both sides of the stab. The triangle can be covered with monokote or simply painted with fuel proof paint.
The result is very strong tail surfaces and usually can withstand the unexpected dumps mentioned above and an occasional jam while loading or unloading the fuselage.
Model Airplane Cleaner
By Arno Clabaugh
Cleaning our models can get expensive and even worse most cleaners do not entirely remove the oil and gas. Here is an old formula or recipe that I used years ago and does a pretty good job.
I still use it today. The cost is right also.
 | 2-1/2 cups or 20oz. Of water |
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| 1/2 cup or 4oz. of rubbing alcohol |
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| 1/4 cup or 2 oz. of ammonia |
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| 1 tsp. of liquid dish detergent * |
To wash the plane, spray on and use your hand to rub the plane. The spray and any oil will foam.
Use one paper towel or cloth to remove the wet cleaner. Use a second to dry and polish. If your mix is right you should not have a film on your covering. This also cleans house windows.
I cannot take credit for this as it was given to me back in the 70's when it was difficult to find a good cleaner. I hope you find it useful.
Arno
Two Ways to Make a Clean
Canopy Installation
By Arno Clabaugh
Many modelers, especially those new to this hobby find it difficult to make a really neat canopy installation. The kit manufacturer's instructions usually just say to install the canopy. Most plastic canopies come formed but must be cut out before installation. Next it must be either screwed or glued to the fuselage.
Now come the majority of problems. First, is not leaving enough lip or edge of the canopy for mounting it to the fuselage. If there is not at least about 1/8 inch for mounting screws or at least 1/16 inch for glue, you are out of luck. The only tip I can give you on cutting is to trial fit as you cut. Second, if gluing and you use the wrong glue chances are you are going to be real disappointed.
Before we get into installing it on the fuselage, I thought I would include a method I use to paint the canopy. Weather it is for a warbird or a civilian type plane, this method works. The painting is done on the inside of the canopy. The material to do this is Liquid Masking Fluid, and of course the paint.
Decide what you want the canopy to look like and then cover the inside surface entirely with the masking fluid. A soft brush does a good job of spreading the masking fluid. Let it dry thourghly then you are ready to cut out the areas you wish to paint. Using a sharp knife like an exacto, carefully cut out all areas to be painted. Be careful not to cut the plastic. The cut out areas can be removed easily by just pulling it out. Leave the mask on all the window areas. Cover the outer side of the canopy and you are ready to paint. Several very light coats does a good job.
After drying and removing the rest of the masking, you will have a paint job that looks first class from the outside. The better cutting job you do, the better your paint lines will look. Figure 1 is a drawing of a canopy I did for a Tiger 2 model. I wanted it to look more like a Cherokee cabin. I also found that using 1/8 th inch trim tape around the windows, really dressed it up. I did the taping on the outer side of the canopy. That looked the best and was the easist method. One tip here is to use Carl Goldberg tape. The ultra violet from the sun practically turns it into paint. Great Planes tape does not stay on a canopy for very long.
Now for the installation. Remember, I don't consider myself an expert on canopy installations but these two methods work for me. First if you are installing a pilot or anything else in the cabin area, do it now. Do not use CA glue to install things inside the canopy. I learned the hard way that the CA creates gas while sitting in the sun and sure messes up a neat job. I use epoxy to install the pilot and even then I drill a couple of small holes in the cabin to vent any possible gas or heat to the fuselage or outside. I have an older plane with a flat headed pilot just from heat. If you have an ARF kit with the canopy already installed you will probably find that it is not entirely glued all around and so heat can escape.
If there is reason to remove the canopy later, a good but tedious job can be done by installing small inch long screws fairly close together around the entire canopy. Drill very small holes around the canopy through the fuselage about a inch apart. Small canopy screws are available at the hobby shop. After making sure everything is okay, you can put a very small amount of yellow glue on the threads of each screw to prevent them from falling out from vibration. I have found that even a minute drop of thick CA does the job and the screws can still be removed. Do not use kicker on the CA.
My favorite way to install the canopy is by gluing. After fitting, cutting and any painting, put a 1/16 inch bead of glue around the canopy lip. See Figure 1. I use only canopy glue. It used to be known as Z56 Canopy Glue. For the past couple of years I have used the Pacer Formula "560" Canopy Glue. Also noted near the bottom of the bottle it has a number PT-56. It may be the same stuff but for some reason it seems better than the old stuff.
If you use Epoxy to glue the canopy, generally it makes for a messy job. If you use CA, it can be worse and usually runs down the canopy and may not be removable. Be sure to do a final fit of the canopy before gluing. The Canopy Glue states that it is fast drying and clear. Fast however, is about 3 hours so you have plenty of time to cleanup and align the canopy. Since it doesn't dry immediately, the canopy must be taped in position and is best left for overnight drying. I generally use 3M Magic tape to hold the canopy. Also it is handy to have someone else helping with the taping. With the bead of glue on the canopy, put it in position and wipe off the excess glue as quickly as possible. Now with two or three inch pieces of tape, tape down the canopy wherever necessary. A good tip here is to fold over about a 1/4-inch of the end of each piece of tape for easy grasping when removing.
Finally, sometimes I will dress up the bottom of the canopy with a 1/4-inch trim tape. I
might note here that if necessary the glued canopy may still be removed by using an Exacto Knife under the canopy edge and carefully sliding it along.
I hope this helps but remember practice makes perfect so keep on modeling. If you know or find
another way to istall canopies let me know and we'll pass it along.
Arno
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