TECHNIQUES

Welcome to the Technique pages.

Here you will find information on building, setting up and flying rc warbirds and multi engined warbirds.

1. R/C Warbird Flying Technique By Jack Devine

2. Twin And Multi Engine R/C Warbird Technique By George Lumpkin (Twinman)

3. Metalized Polyester Tape Application for R/C Aircraft By Carl Bachhuber

Our first set is by Jack Devine. Jack has built and flown almost every style of rc warbird available and his knowledge is your gain.

NEW WARBIRD PILOT BRIEFING

By Jack Devine

The purpose of this article is to make an effort to prevent the unnecessary loss of model Warbirds. It is all too common to see a message posted on one of the internet RC sites where a new Warbird was taken up for it’s first flight and the duration of the flight was about ten seconds and the final result was a severely damaged or worse a completely destroyed airplane.

As you enter this area of our great hobby you will quickly realize that it becomes a passion and a mindset that will help you preserve your models will go far in keeping you involved. As you learn and perfect the skills that make you a good pilot, your desire to build and fly these complex aircraft will dramatically increase. We want to make sure you get started on the right track.

This effort is a collection of information with real application to our hobby. It’s designed to make the new pilot have a much higher chance of successful flight with his/her new pride and joy and to share in the experiences that make successful flight possible. A good Warbird should last many seasons and we hope the following articles will build a solid foundation for the up and coming Warbird generation. The skills and techniques we will discuss have been developed through experience. You can’t buy experience but you can surly consider the points we discuss and realize that implementing them into your flight routines will make you a better pilot and will help you extract the full potential from your Warbird. Let’s get started!

 

GROUND SCHOOL 101

By Jack Devine

Before you even consider attempting to fly a scale warbird you need to insure that all of the aircraft’s systems are functional. The check and recheck plan here will insure the model is ready. If anything on the model checks out unsatisfactorily, DO NOT FLY. It’s much better to come back another day than put your plane at risk. You have to understand that you are the ground crew as well as the flight commander and putting a dysfunctional aircraft in the air is extremely dangerous and not a wise thing to do. Setup on many warbirds is a complex task and you often find there are many distractions occurring while you assemble your plane.

Most planes go to the field in pieces and as the assembly process takes place great care needs to be taken that all of the assembly steps were completed to perfection. You make the decision and also bear the responsibility of a plane being airworthy. Take this seriously because the survival of your plane depends on it.

Check your batteries before every flight. If the batteries are even marginal take the time to recharge them. The little charging units that you get with a radio are good chargers but they are very slow. A full charge will normally take 16 – 18 hours. There are many battery system checkers on the market and you should use a device that loads your batteries as they are being checked.

Make sure your fuel tank clunk is free and in the proper area of the tank. Many models get stored on their nose and this often leads to the clunk in the tank bending around and going to the front of the tank. If the clunk stays there you will probably loose the engine on takeoff and a low and slow deadstick warbird is a disaster waiting to happen. Take the time to check the fuel clunk.

Carefully check all of the fuel lines and make sure they are secure at all connections. Also make sure you have used the proper diameter line and that the line is the right type for the fuel you are using. Glow fuel and gasoline fuel line is not interchangeable. All of your fuel should be filtered and make sure you clean your filter regularly. Many modelers have a filter in the filling line as well as one between the carburetor and the fuel tank. Clean fuel enhances engine performance and it increases reliability.

Retracts also require a thorough check.. Pump the system up and see if it holds air. A pressure between 80-100 PSI is about normal and your should be able to get four or five gear cycles completed before you loose air pressure. If you run out of air after two cycles check for leaks first and if no leaks are found you most likely need a larger storage tank in the plane. I prefer the metal tanks over the plastic bottle tanks. If the retracts loose pressure find the leak before you fly. Repair it and then recheck the system.. Monitor the air pressure with the gear in both the extended and retracted positions. Also make sure the gear lock in the down position and if they are designed to lock in the up position insure that feature works as well. If a retractable tail wheel is used make sure the steering of the tail wheel does not interfere with the tail wheel retract operation. Double check all of the wheel collars that hold the wheels on the axles too. I have see many warbirds take off and leave a wheel behind rolling down the runway.

Flight control surfaces are next. Make sure all linkages are secure and tight. You are required to use some type of method to insure control linkages will not become disconnected in flight. Make sure they are properly secured and that they deflect in the right direction when commanded to do so from the transmitter. Make sure the throws are even and opposite flight surfaces have equal travel when compared to the opposite control surface. I am not saying they need to travel the same distance in each direction they just need to be the same distance movement when compared to the opposite surface moving in the same direction. When you compare the ailerons as an example. When the right aileron is up it should move the same distance in the up direction as the left aileron moves when the stick is moved in the opposite direction. Both should go the same distance up and both should go the same distance down when they are compared side to side. This is really critical on flaps if the plane is equipped with them.

Warbirds need flaps and they should be built whenever possible. They are extremely effective for landing and they dramatically increase slow flight stability. Also make sure that all of you flight surfaces are securely mounted and that all hinges are securely mounted and free of any bind. Double check every thing a second time and if anything is not right DON”T FLY. Fix the problem and then get ready to fly. Make sure you check all of your servo mounts as well. They will loosen up and losing a servo mount could be the end of your plane so look them over before you fly .

Check the engine mount and the muffler before every flight. Vibration is your enemy and it is difficult to remove all of the vibration. Carefully balancing the prop helps but there will always be some vibration. It will loosen everything over time so stay on top of this. Also check the prop for an signs of problems and don’t fly with a damaged prop. If you loose a blade in flight it will destroy the airplane. Don’t chance it. The money you spend to replace a bad prop is far less than replacing your entire airplane.

If your plane passes the complete inspection it’s time to put on your pilot hat and sunglasses and get ready to put your pride and joy into the air. The next unit will cover Radio range checking, starting and engine proveout, taxi and takeoff procedures.

Flying warbirds is different and there are several thing you need to know before you fly. Understanding the things that can happen before they do happen will aid you in being able to correctly react and give you the chance to enjoy the reason you took all of this on in the first place. Warbird flight is a thrilling experience and getting you there successfully is the reason we decided to do this article. We will discuss all aspects of flying a scale warbird from takeoff through post flight inspection and hopefully pass on some tried and proven information that will keep you involved with this great area of radio control modeling.

 

FLIGHT OPERATIONS

By Jack Devine

With the big day upon us the nerves will most likely be very tense and this is the time when many things can get overlooked and most of them lead to big problems so let’s go back and recheck one last time.

Fuel the plane and make sure all fuel lines are securely fastened and properly routed. If you are using Air powered retracts make sure your onboard supply tank is pressurized to your desired system pressure. I’d recommend a minimum of 80 psi. Cycle the gear and make sure they function properly and that they lock in the down position when you command them down. If the gear checks out recharge the air tank to the proper pressure. Check the flight battery pack with a volt meter. If the flight pack is even marginal DO NOT FLY. Charge the batteries. If the batteries check out, insure you have control of your radio frequency and turn on your plane and radio and range check the radio. If anything appears abnormal fix the problem. Do not attempt to fly unless the radio system is 100% functional. Standing directly behind the plane, go through all of your flight surfaces and make sure you have everything moving the right direction. Always do this check from behind the plane because it’s easy to make a mistake if you do this check from any other position and a reversed control surface is usually a fatal mistake for your plane. If everything so far looks good it’s time for engine start-up. Secure the plane with some type of restraining device. Another person is always best. Make sure your helper is aware of what you are going to do and if necessary walk him/her through the start-up before you actually start the engine. Big birds and most Warbirds have high powered engines on them and the power may surprise your helper so make sure they understand exactly what you want them to do.

Start your engine and allow it to warm up to normal temperature. This normally will only take about a minute but it insures the engine will operate properly when you activate the throttle. Run the throttle up to maximum power two or three times and the engine should run through the transition to maximum power smoothly each time. If the engine sputters or hesitates correct the engine problem before you fly. The engine needs to be reliable and consistent and it should respond smoothly to every throttle change. Spend what ever time you need to here to insure the engine is properly adjusted. Deadstick warbirds are difficult to fly at best and the potential of having a deadstick plane to deal with on your first flight is dramatically reduced if you make sure you can count on the engine.

Ground handling is next and you need to practice taxiing the plane to learn how it responds to your radio input. Most Warbirds are tail draggers and the tail wheel input is the key in making the plane go where you want it to. Turn in both directions and make sure the plane quickly executes the turns on the ground that you are commanding through the radio. If the taxi capability checks out it’s time to get airborne.

Check the wind sock and verify the wind direction. On your first flight it’s best to fly in as little wind as possible and I would recommend you wait for calm winds until you have a few flights under your belt. I’m not saying Warbirds should not be flown on windy days I’m just saying you should give yourself every advantage possible on the first few flights.

Taxi to the active end of the runway and once traffic is clear call your takeoff . Taxi to the center of the runway and turn for departure. Take a good deep breath here because you may forget to do that for a little while and think about your takeoff routine. Release the elevator stick as we want the plane to run on the main landing gear until it has sufficient airspeed to fly.

The premature takeoff is the big killer here and avoiding it is not difficult if you stay with the routine. The elevator is the killer of many new planes because they jump into the air without sufficient airspeed. The throttle goes to maximum power and a torque induced roll to the left begins. Your reaction is to input maximum right aileron which further effects the stall and with no altitude and not enough airspeed disaster is just a second or two away. You need to manage the throttle and input enough right rudder to keep the plane centered on the runway. Slowly advance the throttle and let the plane start it’s takeoff roll. Don’t worry about building speed quickly and DO NOT advance the throttle too quickly. The tail will come up as the speed comes up and once it does avoid adding up elevator. The takeoff speed you need will take a second or two to develop and you should be just passing through half throttle at about this point. As the tail comes up the rudder authority will increase and you will have to reduce the right rudder input to keep the plane going straight down the runway. Continue adding power and you should be getting very close to takeoff speed. Add just a touch of up elevator and your plane should break ground and begin it’s climb out. DO NOT attempt to turn and keep the aileron input to a minimum until you are sure you are flying and the airspeed is continuing to come up. Use just enough up elevator to establish a gentle climbout. If you have ever watched a real warbird takeoff this is exactly what happens. You don’t see them heading straight up two seconds after leaving the runway. You don’t see them turn either until they are well established in flight. Keep using the rudder to keep the plane on course.

Once you have gained about fifty feet of altitude begin your first turn slowly and as the plane comes around and starts down the downwind leg take a big breath and throw your gear switch to retract the landing gear. Briefly look down and make sure you throw the right switch. The gear should begin the retract sequence immediately. Once the gear is up gain some more altitude and it’s time to work on your flight trims. The goal here is to trim the plane so straight and level flight is established with no transmitter input. You should be at about ¾ throttle and if that seems a little too fast throttle back to a more comfortable airspeed before you trim the plane. Just remember you are not flying a trainer or a Cub here and the wing loading on your warbird is high so keep the airspeed at a manageable level. A properly trimmed airplane will give you time to relax a little bit and I’d think it will go along way to get your knees to quit shaking too. After flying a couple of circuits you should have the plane trimmed for hands off level flight. If the plane is difficult to trim then something is set up wrong and you should land as soon as possible but don’t panic. Think about what is happening and input the commands you need to keep your plane flying as normally as possible. Avoid over controlling the model. Warbirds respond very quickly to transmitter input and in most cases a little input results in allot of reaction from the plane. If the plane seems overly responsive switch the radio to low control rates on the ailerons and the elevator if your radio is equipped with these features.

Make nice smooth inputs and you’ll find that a Warbird goes exactly where you tell it to. Don’t attempt any fancy flying until you have the plane trimmed for level flight. You can do all the hotdogging after you are comfortable with how the plane flies. Turn the plane in both directions so you get an idea of how it will turn. Warbirds need to be flown with both rudder and ailerons and use the elevator to keep the plane at consistent altitude during your turns. If you want a warbird to look good in a turn use the rudder to help you turn. You need to become familiar with the rudder because you are going use the rudder in the landing routine. Warbirds force you to use the rudder and many of us have learned to fly without using the rudder. You will be amazed at how well your plane will turn when you apply a little rudder. Now Enjoy your model. Fly nice smooth circuits and get to know your new plane. I’d highly recommend you stay away from the rolls and loops for a flight or two.

The next step is to figure out how your plane will react in a stall. It will help you recognize the minimum safe airspeed for your plane and if there is going to be and adverse reaction to the stall. Some planes just start to buffet a little bit and stall straight forward and others will snap violently and you need to be able to react to either condition. I recommend you do this on the first flight if you are comfortable with this routine. If not you need to get it done before you start putting the plane through any advanced maneuvers.

Climb to a safe altitude. Altitude is the safety blanket and you need to make sure you have enough of it to recover safely. Fly the plane in the traffic pattern and apply just enough up elevator to start climbing. Start reducing the throttle and slowly increase the up elevator until the plane stalls. If the plane just buffets and kind of mushes forward release the elevator and add a little power. If the stall continues drop the nose and gain some airspeed and fly out of the stall. If your plane snaps don’t panic. Get the nose down and add power. Stability should return quickly and once your flying surfaces are actually flying again you should quickly regain control. Get the plane leveled out and relax and take another deep breath. You have just found your absolute minimum flying speed and you crossed the line and saw how your plane reacted. You must stay above that airspeed to avoid disaster while you fly your plane.

Now the only mandatory maneuver, LANDING!!!

Every flight will end with some type of landing and if you prepare and set it up properly you will have successfully completed another flight. This routine needs to be automatic. Setting up the plane for landing is not difficult but you need to understand again that you are flying a warbird. Warbirds have flaps and if your model has them …. Use them. Throttle back in straight and level flight and drop your flaps and see what it does to the flight characteristics of your plane. It should immediately start to slow down and if the power level is above half throttle it should start to climb. At low power it will continue to slow down . You manage the decent with the throttle not the elevator. This is important and you need to make sure you understand it.

Now let’s set the landing up.

Call your landing so the other pilots on the flight line know your intentions.

Make a straight and level pass in front of you and reduce the throttle to about half and drop the landing gear. Fly another circuit and visually verify your landing gear is down. You should be 100 feet up as you turn onto the down wind leg. Drop your flaps and correct any altitude change. I dial in about 5 degrees of down elevator mix with the flaps through the coupling available in my radio and this keeps the plane flying level. It also gives me a shorter list of things I have to do as the radio automatically takes care of the trim change after dropping the flaps. Turn onto the base leg and you should still be at about 100 feet. Turn final and start your decent as you reduce throttle to about 1/3rd. Point the airplane at the touchdown area at the end of the runway and control the decent with the throttle not the elevator. To steepen the decent reduce the throttle and to decrease the decent add a little more power. Steer the plane to touchdown with the rudder. Use the ailerons to keep the wings level. The entire approach should be at about a 45 degree angle. This seems pretty steep to some pilots but this is the right method. At about ten feet of altitude you should be just over the end of the runway and if everything looks good reduce the throttle to idle and at about three feet start your flair. Let the plane settle on the mains and do not force the tail down with up elevator. Use the rudder not the ailerons to keep the plane going straight and as the speed bleeds off the tail will come down on it’s own and then you can steer with the tail wheel. Forcing the tail down can cause a takeoff and at this airspeed and low power you will certainly stall and we know the result.

If you are not satisfied with the approach simply add power slowly and keep the wings level. As the power comes back up so will the airspeed and the plane will start flying again. Climb slowly and do not attempt to turn until you are sure you have enough airspeed to do it safely. Just remember that if you are going to miss the approach add power slowly. You will want to jamb the throttle wide open and this could cause the dreaded death roll that has been talked about before. Don’t panic just add power slowly and start a gentle climbout back to your landing setup altitude and try it all over again. Don’t force a landing any more than you would force a takeoff.

Once you have your plane back on the ground and you are breathing normally again analyze the entire flight and think about what you could have done to improve it. As you practice these two routines- Take off & Landing they will start to become automatic. One step naturally leads to the next and with a little practice you will master both and you should have your plane for many flying seasons. I practiced these routines many times before I ever attempted an actual flight. The steps have a natural transition and with a little practice they really work.

I had the honor of knowing a very special man that was an instructor pilot and a combat veteran of over 50 missions in WWII. He saw me crash my first Corsair and he took the time to tell me what I had done wrong. He became a great friend and we developed what you see in these few pages. I took advantage of what he knew and I became a better pilot because he took the time on that first day to ask me if I knew what I had done wrong. I was very upset that day but I knew by the tone in his voice that he felt as bad as I did seeing me sort through the pile of broken airplane trying to find out why the crash had occurred. He told me there was nothing wrong with the plane and that stung a little but in the next couple of hours I found out just how right he was. He knew the Corsair like the back of his hand and he often called it the “Bentwing Bitch” but he loved and respected the plane and he took the time to share what he knew. The reason I agreed with Paul to put together this article was to pass on to other pilots what he had passed on to me. It was an honor to know him and call him my friend.

Welcome to the wonderful world of Radio Control Warbirds!!!!

Jack Devine

 

Twinman (George Lumpkin) our multi engine advisor describes the art of flying these two, four and more engined warbirds.

Twin Engine Saga: So You Want To Do Twins ?
By Twinman

My personal list of suggestions for success with Twin Engine Aircraft.

Rules:
1. Don’t do twins – four times the trouble and worry of a single engine airplane.
2. See #1.
3. As you can’t follow instructions (you skipped #2) please read on for my personal suggestions for success to enter the “exclusive” (see “eccentric” in the dictionary) and challenging world of twin engine radio control airplanes.

Twin Engine Tips for Success
Twins are for experienced pilots. Not a second airplane!
Pick a plane where the engines are close together, as this minimizes problems during an engine out situation . DO NOT start with a warbird for a first twin.
Long tail moments and large rudder control surfaces are also a strong advantage to control differential (uneven) thrust from two separate engines.
Learn to fly with the rudder! It is very important during take off and for control when an engine out emergency occurs. This is far more important than in single engine airplanes, set for near maximum control deflection.
Pick a tricycle landing gear arrangement. During the take off run, the two engines never come from idle to full speed together. This causes the plane to wonder on take-off far more than you are accustomed to. Tail draggers are much harder to control in twin engine configuration.
Engine control.
Always bring the engines up slowly on take off to avoid engine flame out in transition. Do Not immediately fire wall the engines. If an engine sags on take off run – do not take off! (Burn in brain).
Never, ever, “peak” the engines for maximum RPM by leaning the mixture. This almost guarantees a dead engine . run them slightly (Read “more than normal” for a single) rich for increased reliability.
Never lean an engine to match the stronger engine. Yes, one will always be stronger. Richen the strong engine down to the weaker (that is running slightly rich …remember ).
Check that idle speeds match and idle mixtures are consistent for reliability and smooth transition to full power.
Most important!!! Before take off, always (use a helper if possible for safety) go to full power and hold the plane straight up for 5-10 seconds. If you lose an engine at rotate or climb out you will crash! This is the most vulnerable point in the whole flight. Lose an engine here, and the plane will immediately rollover and spin in. (Spectator note: Applause is really not appreciated in a twin take off Crash!)
If an engine sags or screams to a lean out RPM – Don’t take off until you correct the problem! Personal suggestion – do it once at the pits and again before take off on the runway. Yes, things change from a cold engine to a warm engine. It may work OK in the pit, but lean out on the runway. Do it every time you fly! Engine performance can change as the daytime temperature increases. This can cause lean runs.
Idle speeds need to be reliable and reasonably close to the same speed to avoid differential thrust during landing.
Next issue……...Flying Characteristics

Twin Engine Saga: So You Want To Do Twins ? {Part 2}
By Twinman

Flying Characteristics
After the normal 3 mistakes high altitude is attained, (yes 3 mistakes high not 2 as is normal for single engine) the plane will fly very similar to single engine airplanes.
You will note the maneuvers, rolls, turns, etc., require greater input as the wing loading is heavier than a single. The plane feels slightly heavy. Note the wings are heavier due to the greater mass of engines located on them and away form the center of the fuselage as is normal for single engine airplanes. It takes more force to start and stop this mass.

Landing (Normal Twin Engine Operation)
Wing loading is higher than standard airplanes and so landing speeds are faster be prepared for this. Do not try to slow down and risk a stall like a single. The plane is more likely to fall out of the sky than is a single at stall speeds.
Make your approach with reduced power; not full idle as you would with a single. This will prevent stalls due to low airspeed. It also increases the reliability of the engines because of the slightly higher engine speed.
If (and it will happen) a go around is necessary. Do not firewall the engines!!! You are near stall speeds and differential thrust at this speed and altitude is very difficult to handle. Lose an engine here and you will crash. Gently bring the engines back up to flying power. Fly straight to gain speed during power up. Climb after engines are at full power.
During power up listen carefully to the engines. Any sagging of one engine means go to idle and land now. Do not risk an engine flame out at landing speeds. Damage from a grass landing and weeds will be less than a high RPM inverted flat spin. (More tree branches are better than tree trunks). Taking off with two engines does not guarantee landing with two engines. Thought for today.

Single Engine Out Emergency
If possible fly alone as you want to hear the “harmonic” of the two engines. Loss of this sound means trouble, perspiration, elevated pulse, blood pressure trembling hands, etc. Prepare to land NOW!
If flying speed is high, you are relatively safe as control surfaces can control differential thrust. I suggest you pull back power to an absolute high of 75%. With 50% being safer.
Use the rudder!!! If you lose the right engine the plane will yaw and try to turn to the right. Apply left rudder to control yaw. You can apply left aileron to hold the wings level, but you must control yaw or the right wing will stall. Use the rudder! Prepare to land- now! Keep your speed up.
Left hand turns are very difficult with the left engine running at high power. If you must turn, I suggest powering back to less than 20% throttle, to reduce differential thrust, and keep the nose down to maintain speed. Make the turn and slowly bring up power if necessary, slowly! No more than 50%. The plane will react as the power comes up, be prepared for it, and prepare to reduce throttle if yaw cannot be controlled. Now use only 50% throttle max as you have lost airspeed and controllability during the turn.
Right turns can be made easier than left turns with the left engine running, but the risk of a spin is higher if power is not reduced during turn. Keep the nose down to maintain air speed.
Make a normal approach – keep up airspeed. When lined up, cut engine to idle, (this eliminates differential thrust) and land.
On final approach do not bring the power back up. You will crash as airspeed is too low for the rudder to control yaw, use of the ailerons will actually cause the under powered wing to stall. This will cause the plane to roll over and dive into the ground. Landing short or long it is always better than an inverted crash. Do not try a “go around”! The slower you fly the less engine power you can use as rudder effectiveness is reduced as air speed reduces.
Twins are definitely fun to fly, draw attention, sound neat, look cool, and will demand your best flying skills. Big point never let them see you sweat or shake.
If at any time during single engine flight, yaw increases, a wing rises, you enter a spin, bring the throttles to idle. This will eliminate differential thrust so you can gain control. Lower the nose to gain speed and Land!!! Trying to power up again is very dangerous. You are too slow for single engine control.

Your first take off with a twin will be less stressful if, after mandatory vertical power check, a helper holds the plane on the runway at full power and releases it at the pilots signal. This eliminates differential thrust during run up at take off. You are already nervous, and this reduces some of the potential problems. If you are starting with a tail dragger this is strongly recommended.
Futaba 8 channel, Hitec, and I assume JR all have mixing menus that will allow the two engines to be slaved to the rudder. Example: Right rudder will slow down left engine and increase right engine if below max throttle. This could produce fantastic hammer head turns, reversible spins, easy spin recovery, knife edges etc. I have not tried this…. Yet! But I do suggest you be able to cancel this function very quickly.

Next Issue: What kind of Twin

Twin Engine Saga: So You Want To Do Twins ? {Part 3}
By Twinman

Additional Twin Points
Do not mount twin engines inverted. They are less reliable due to carb flooding and tank positions. You will also experience more problems due to fuel puddles at glow plug. A 90 degree mount is ok with easier access to the carb needles for mixture adjustments and better fuel tank positioning.
Using 10% fuel produces less power than 15%, but the engine runs cooler and helps prevent lean out due to heat. Increasing the oil content of the fuel will also help with this. As stated in previous articles the reliability of the engines is the most important part of multi engine flying.
Flaps are a good idea, as it significantly reduces landing speeds that accompany high wing loads, as well as on board glow drivers, which are good for increased reliability at idle and power up. If you use the on board glow driver keep the power on up to the 25% throttle setting.
Safety:
Always start the engines from an angle to avoid propeller arc and “in front” dangers. Always start engine farthest from you to keep from having a running engine near your body. I suggest using a helper whenever possible. With two engines, two props, there is twice the possible dangers. Only adjust needle valves from behind airplane.
What kind of plane:
You can convert standard single engine to twins. I suggest using one with thinner wings for less drag during single operation and higher speeds. Just add a nose cone over the existing mount and build nacelles on wings. You will have to set the Thrust Alignment, however it is much too complicated for this article. Another option is to mount quarter inch plywood beams across the existing single engine mount. Install two engines on this in a “hammerhead” design. Plan on using a lot of tail weight. You will also need two separate fuel pick-ups if you want to use one tank.
If have two like fuselages, can marry them together for a “twin Mustang” effect. The advantage to this is there are also two rudders in the prop blast for better low speed control. There are also less fuel problems with this design than a hammerhead due to separate tanks.
All of this is fine if you are already flying twins or have a lot of scratch building skill. For first timers however I suggest you get one of the twin ARF’s or kits.
Suggested Models:
Twin Star – 25 size, AARF and good flight characteristics.
PBY- as engines are very close together and big wing.
If you can find one of the inline push pull twin designs used by the US army and German Army. This eliminates the differential thrust worries. Example: Cessna Skymaster.
ARF Twin Mustang– two rudders and the engines are close together, but it is a tail dragger.
Twin Sukoi ARF- More aerobatic, engines close together but it is a tail dragger.
Texas twins has a Bobcat series of twins 20, 40, and 60 size. My personal experience with the 60 size is very good. Yes, I have 90’s on it, but that is another story. (Note: Over powering a twin can get you into trouble faster than normally powered planes.) These designs are now handled by a Florida company. They are a tricycle gear arrangement.
Personal suggestions of planes to not to start with:
P-38, Mitchell B-25, Cessna 310, or any war bird with wide engine spacing and high wing loading. Build up to these. Yes, I have two P-38’s …… Do as I say not as I do! The DC-3– a tail dragger and wide engine spacing. Fly’s well, but not for your first twin. The Cessna 310 wide engine spacing and short fuselage again not a good first twin. In short if you are not sure talk to people that fly twins for their recommendations.
The main point of flying twins is to impress people around you. So never let them know how close to disaster that last “really neat maneuver” really was!!!
Remember losing an engine does not cut your power by one half. It can cut climb power by 90%. If you have two 1.6 HP engines for a total of 3.2 HP Assume the plane needs 1.4 HP for level flight. Lose one engine and you have .2 HP reserve and this does not take into account the drag of the dead engine or heavy rudder deflection necessary for straight flight. Now you want to climb too – get real!
On board gyroscopes for the rudder will significantly reduce unexpected turns due to differential (unequal) thrust. They will help in take off runs and avoid (with out control limits) or minimize ground loops. They are not able to fly the plane completely as they are not heading hold systems and cannot compensate for engine loss after airspeed drops below the ability of control surfaces to counter engine torque. They will give you more time to react to engine failure problems. If used, practice first on single engine airplane and be able to turn it off in flight. Rolls can be quite “interesting” with a gyro on.
The Futaba 8 channel (I don’t know about the others so don’t yell at me) has the ability to have separate throttle control. With this you can practice single engine performance and flying characteristics. (Minimum 4 mistakes High). Learn to use the rudder! While this is important for all airplanes it is mandatory for a twin’
Do not ‘slave” the rudder to the ailerons. It will not work to counteract engine torque during single engine operation. This is due to changing rudder requirements due to airspeed and engine thrust settings. Not only is it a crutch but inverted flight (where rudder functions reverses) becomes impossible. Forget knife edge etc, etc,. If you can’t fly (Or won’t) with coordinated rudder control, don’t fly twin engine airplanes; you are a crash waiting to happen.
Use reliable engines that you are familiar with. Do not “mix old and new engines, mufflers or engine types. They need to be a matched set capable of similar power (thrust) and reliability. If you need to buy a new engine to match your current old engine, rebuild the old one. This is easy and inexpensive if it is a ring type engine.
Try to get the engines to idle, midrange and hit peak RPM as close together as possible. This is important to minimize differential thrust. I realize this is tedious, time consuming, and a pain in the a__ , but very important for twin operation. Note earlier comments on setting engine RPM.
Don’t use bell cranks for throttle linkage. This just adds to the play and set up problems. If you use nyrods (which is OK), make absolutely sure they are the same length along the nylon push rod length. These rods expand and contract with heat. If they are the same length these changes in length will be uniform and so not affect engine synchronization.
Any Body for Four Engines?
2 engines are 4 times the problems of a single.
I do not want to think about four . How about the Spruce Goose – 8!!! *&%$#^&**.

There’s more to come…...Twinman

Twin Engine Saga: So You Want To Do Twins ? {Part 5}

By Twinman

Rule Number 1– Don’t Do Twins– Four Times the Trouble
I guess if you’re still reading this section you obviously aren’t going to listen to rule number one so here is a suggestion to try and ease some of the anxiety associated with flying twin’s. Are gyro’s the answer?
I have previously explained how losing an engine on a twin can result in an inverted flat spin faster than you can imagine. It’s worse on Warbirds with high wing loading and wide engine spacing (P-38, B-25, etc)
I have decided to see if the problem can be solved by using two gyro’s on the plane. One gyro on the rudder, and a dual inlet/ outlet Hobbico “Aero Gyro” on the ailerons. This in mind, and for the glory of Bayou City Flyers (I hope Greenwood is getting this), I programmed my kit bashed Twin Ugly using a 8 channel Futaba to intentionally cause an engine failure and possible crash! Via a rotary dial channel, my copilot, and son Kyle, (who was only too happy to deliberately cause a crash) was able to bring one engine from full power to an idle on my command. As a side bonus this allowed me to sync the engines at idle very easily. After the initial setup and trim in flight I noticed a much more stable aircraft. Maneuvers became really rock solid. Hanging on the prop straight up was almost hands free. Now for the test. I flew level at half throttle, pulled the nose straight up and went to full power. At this time I signaled to the copilot (who was dying to help) to cut one engine to idle. This should have caused an immediate inverted snap roll. It did not. The plane slowly yawed toward the retarded engine. (I said retarded engine not pilot!) I then applied down elevator and flew three laps around the field, at various power levels, in a tense but controlled manner. The plane was flying at almost a 30 degree yaw angle in level flight, but fly it did and it should not have. I signaled my copilot (who had his mouth open in amazement or disappointment!) to bring the idling engine back up to speed. The engine promptly died! Naturally there was a cross wind, and I’m starting to have chest pains! The landing however was uneventful.
This test did prove that the concept works. The gyro’s, as used here, do not take control of the plane but rather dampen unexpected actions sufficiently to allow you time to react. If you have to rely on your reflexes to do this you are already about a second or two behind the plane which, in a lot of cases, is too late!
As a side note I used the Hobbico “Aero Gyro” because it allowed me to use separate channels for the two aileron servos so I could mix in aileron differential. You could also couple the elevator and ailerons for more positive elevator control. This gyro also allows me the option of turning it off in flight as needed for aerobatics.
Are gyros the answer? Nothing replaces ability, but they do allow you to relax a little while flying twins. I have already had my heart attack trying this and could use a little relaxation.

Additional. This concept was further used with great success, on an Areotech P-38 and was proved to be a viable way to control the P-38.

Twin Engine Saga: So You Want To Do Twins ? {Part 6} By Twinman

It has been five weeks of me trying to talk you out of trying twins. Still you won't listen, so I will write the final chapter. (Cheering is in bad taste) The old twin ugly has served it's purpose to be the test bed of these articles and now retired and in the hanger. No, it is undamaged!!!! The final test was to try the most difficult and dangerous maneuver for a twin engine airplane...The Single Engine Takeoff! The twin ugly has served well in these tests and so the decision to try the single engine takeoff was an easy one....Yeah, let's do something new!!!!! (Told you flying twins was a nutty idea!) Total time for the decision....2.5 seconds. One early (so as to have not too many witnesses) Saturday morning the old plane was fired up on twin engines and twin gyros (See Last Month Story on Gyros) for a refamiliarization flight. This went well by trying eight point rolls inverted low passes etc.. The plane was landed and one engine refueled and the other tank drained. Gyro for the ailerons set to maximum rate. My son and copilot Kyle ( always one for a good crash ) assisted to carry the doomed plane to the far end of the runway with the single engine at quarter throttle to maintain heat. The single engine run up and was held at the straight up position for the 10 second requirement, for safe take off. The plane was set on the runway (The peanut gallery was unusually quiet.. Or was taking side bets) Rudder and aileron set at 50 percent into the running engine, (This rapidly increased to 75% during the roll out) and with a deep breath, the plane was off at a very slow pace. Remember that one engine out is not half power, but a loss of up to 90% of the required power for flight and climbing. The plane was held to the ground the full length of the runway to gain maximum air speed and so control at lift off. I pulled up around 20 feet from the end of the field and began the slow climb for altitude. ( Your Friend) Controls were sluggish to say the least, but controllable. I made a turn into the engine( Not recommended and difficult as the plane wants to turn away). First concern was to put as much space between the plane and the ground as possible. After three circuits around the field, I decided that it was time to land. (OK, my hands were shaking so bad that I was having trouble holding the transmitter.) The peanut gallery seemed unconvinced that one flight was actually a test of skill, so a second flight was attempted.( My son is concerned that insanity is hereditary, I assured him that only hair loss is!) The second flight was as uneventful as the first( OK so it was just as terrifying as the first) It was going OK until the peanut gallery (One half of my club...to name but a few of my "friends") started screaming to LOOP IT,ROLL IT. Well, not having good sense to ignore the challenge, I climbed as high as possible. This is a difficult process on one engine. Yes, the plane did both loop and roll on command. One low life commented that a real pilot would have done as low level inverted pass! Call me woosy,,, No way!!!!! Seriously, the tests conducted with the twin gyroscopes are, in my opinion, a complete success, and will be added to two P-38's I and my son are finishing as we speak. No, the gyros are not necessary for all twins and I don't use them on my other two twins, but if you are going to start with twin engine airplanes, and even think about the P-38 ( Understand an ARF is coming) or any other heavily loaded high powered twin and expensive war bird, I would really like to recommend them as cheap insurance. Good Luck and see you at the field...I'm the one with the twin electric fans on my Aggie hat!!!!!

 

Carl Bachhuber describes how he does his great metalic warbird finishes

Metalized Polyester Tape Application for R/C Aircraft.

By Carl Bachhuber

Some of you have asked how I simulate the aluminum finish on some of my scale aircraft. Since the 1980's I've been experimenting with types of Metalized Polyester(MP) tape. 3M and others manufacture it mostly for silk screening, and slide masking. It also can be used as I've found on model aircraft.

Well let me give you some of the advantages. Unlike heat shrink coverings this will not bubble or loosen over time. I've had it on one airplane for over 12 years and it really looks as good as the day I put it on. It is much stronger than plastic films. It is easily repaired. Applying the tape is a fairly fast process and it can also be painted. The tape is impervious to Gasoline, Methyl Ethyl Ketone(MEK) and most other thinners. It is lighter in weight than most paints. It is about 2 mils thick and is non-conductive. Mixing and matching different types of materials such as aluminum tape, paint and MP tape can create a very realistic finish.

Disadvantages. Well, the biggest disadvantage is the limited ability of the tape to conform to compound curves. A bit of heat helps but if the curves are too sharp you may need to cut the tape or come up with a different method of metal covering simulation to achieve a satisfactory result. MP tape is for covering solid surfaces not open bays.

Prepare the model the same way you would for paint. I usually cover the model with a 3/4 oz. glass cloth and a laminating epoxy although polyester resin can be used also. I use an acrylic auto primer after the model has been sanded. Instead of spraying on the primer try using a short nap small paint roller. Seems to be a very fast process with no overspray. Sand and fill till your satisfied. Remember, too much sanding is never enough. Once satisfied, wash and wipe down the model so that it is as close to clean as possible. You should now be ready to apply the tape. I use a squared sheet of metal as a cutting board. Since the tape has an aggressive adhesive on one side put that side to the cutting board and unroll a length. Cut into the desired panels. Buff with Scotch-brite if you want that abused aluminum look instead of a mirror finish. Make sure you have removed all particles from that process and the aircraft lest you should have contamination under the tape after it is applied. Now, raise an edge of the panel with a Xacto knife and peal it off the cutting board. Place the panel on the desired spot on the model and press from the middle of the panel to the outside to keep air entrapment to a minimum. You might also want to keep a covering iron on a high setting while your working as it can be helpful on minor compound curves. Again work from the inside out. Don't worry if you screw up a panel just peel it off and reset or toss it out.

After your finished applying the panels you might want to try simulating rivets by using r/c 56 glue for raised rivets. In the case of flush rivets the hot tip of a wood burning tool shaped like a rivet works very well although it takes too much time for me. Instead I came up with a "dritz wheel" like tool with brass tubing spokes which does an acceptable job of making rivets fast.

If you want to experiment with this material it can be found in manufacturers directories under specialty tapes. Look for 3M #850 or equivalent. One company Specialty Tapes uses the part number #298 Silver metallic tape in their catalog. Don't be afraid to shop around. There are others. Good luck!

There will be much more to come so please stop back and check often.

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