I'm helping my brother build a GP 60 Cub I fly he doesn't yet. I don't have tail dragger experience yet and was wondering how hard the Cub will be to take off and land?

Cubs can be a bit on the twitchy side on take off due to the relatively narrow and tall gear. If there is little to no cross wind, you shouldn't have much trouble as long as you are gentle with the rudder. Do a few practice taxi's up and down the run way to get the feel for it. When you're ready to take off, roll the throttle on gently. With the Cub, you will be able to take off easily at 1/2 throttle but make sure the model is ready to fly before you pull it off the ground. A Cub will tip stall as easy as a heavy war bird if you get heavy fisted while flying slow.

In the air, a Cub is an easy flying model though they do have a few quirks about them. Unless you setup the ailerons with quite a bit of differential throw, more up than down, the model will tend to skid through turns. You can get around this with either co-ordinated rudder, or the aforementioned differential aileron throw.

Landing is cake, but if you land too fast on a rough or grass field, you could end up flipping the model on it's back during a nose over.

John

John is right. You won't have any trouble FLYING a cub. They are a piece of cake.

But taking off with your first taildragger is always an interesting experience.

Get used to taxiing while holding full up elevator to keep the tail on the ground. When your ready for take off, keep holding full up while you add power. Once it starts rolling, slowly let off the elevator (Enough to let the tail come up, but not so much that the plane noses over). At the same time, it will want to pull to the left, so a little right rudder will be needed to keep it straight, but be careful not to over-correct. Just keep your rudder inputs gentle. It takes a few take offs to get used to it, but you'll get the hang of it in no time.

The only thing I'll add to the above is after the tail has lifted - WAIT - Let it stay on the ground and build up some more speed. Then gently lift off. If you try to lift off just when the tail breaks gound, I'll guarantee a ground loop! Cubs sometimes have a reputation of being hard to take off. Let the tail come up - build up some more ground speed and they are gentle.

Great flying planes. They need some rudder in the turns as JWN mentions but what great flyers. It's really easy to get hooked on flying Cubs.

John

I built a GP Cub 40, was a little apprehensive on the maiden, had heard so much about the dreaded ground loop. After a few practice runs, I just concentrated on the rudder and let the Cub do its' thing.

Once the tail comes up, there isn't much to do but keep it straight, let the speed build up, the plane seems to just lift off by itself when ready. An awesome plane.

Power in mine is an OS FS70, love that "putt-putt" sound. It's a tiny bit nose-heavy, but I like it just fine.

BO

Two things to watch out for besides the good advice given above: 1, put a little toe in on the main gear and 2, keep the CG at the most forward recommended position, especially for the first flights. Cross wind ground handling can be a difficult proposition, the model will want to weathervane into the wind and the downwind wing will drag and flip the model.

Most of the suggestions are good ones. I currently have eight R/C models, all with tail wheels, and have hundreds of hours flying full scale tail wheel aircraft. Based on this, here is the most effective way to take off in a tail wheel aircraft, model or full scale.

Trim the aircraft for a gentle climb. As you advance power to take off, initially hold some up elevator to keep the tail wheel on the ground. As the roll begins, relax the up elevator and concentrate on keeping the airplane straight. Be very gentle on the rudder as it doesn’t take much correction. As the speed builds, the tail will lift to place the aircraft in a slight climb attitude. Just keep it straight and when it is ready to fly, it will lift off in a gentle climb and will have plenty of speed to avoid a stall. As soon as it leaves the ground, transition to aileron control for direction.

It is unnecessary to use the elevator to “rotate” for take off and that is where take off stalls are likely to occur. The most common problem with take off in tailwheel aircraft is over control with the rudder. There is a bit of lag in directional control on the ground and by the time you see the aircraft respond it’s past time to release the control. It’s really not as difficult as it sounds. Just be gentle with the rudder and you will master it in no time.

Great suggestions. I learned to fly in a J-3 and the models behave just like the real plane. Ground loops on a narrow grass runway were really thrilling. My dad was my instructor and was pretty patient with my first couple of attempts. Remember not to jam the throttle all the way, a J-3 shouldn't take off at full throttle unless it's on floats. Flying it will be good practice for you using your left hand on the rudder both on the ground and flying. It wont' skid through turns as much if you coordinate rudder with aileron. You could program a mix in, learning to use rudder is more fun. Rudder is important for crosswind landings. You will have a ball learning to slip a Cub in for a landing. Finally don't ingnore the advice about toe-in. It will make life easier.

WOW!!!
What a wealth on info in this thread, even though it really is not "kit building"! How long do these threads remain in the forums?
I purchased the Sig 1/5 scale cub kit but haven't had the time to start it yet. Heck, I haven't even solo'd my trainer yet (hopefully this weekend, weather permitting).
I'm hoping I can find this thread in 30 - 60 days when I am done with my Cub!

Dano13

You can always go to "Favorites" and bookmark this discussion. At least it's under "Favorites" if you are using MS Internet Explorer.
John

Thanks guys this is what I love about RCU, Veteran flyers! just some info on the kit! It's the GP 60 Cub with a Saito .90 Twin and my brother decided he wanted the engine to look close to scale so he purchased 2 Saito heads for the .90twin and mounted them behind the .90 as dummy heads Also he is covering it with Stits.

Much the same as my current Cub. GP 60 size with Saito twin 100. No extra heads though. Covered with Nelson RC Fabric. Also has floats, of course. Painted with Nelson paint. He has Lockhaven Yellow which is the true Cub Yellow. Great flyer.

Next Cub project waiting in the kit stack is a Sig 1/4 which will have a Saito 160 twin. Have floats for it also.

The Sig is a very nice kit you will enjoy it heres mine





Den

Just one other point when flying. (Taking off has been thouroughly covered. )

With my Cub I have to give opposite aileron input in most turns. Many Cubs tend to have the turn tighten on it's own, and coordinating rudder will compound that. It's nothing too extreme, but wanted you to be aware.
Dennis-

I was told by one moderator that these threads stay up indefinitely. Apparently RCU has unlimited space. Most Cubs are from kits, so any discussion about them is still on topic.

I have been building and flying for about 50 years, but there is always something new to be learned from others.

BO

I dissagree strongly with DBCherry's comments on needing oposite aileron in a turn. All of mine (3 quarter scale) benefited greatly from coordinated turns--i.e. right rudder with right aileron for a right turn else severe skidding occured. Now, if you want a flat turn (no bank but change of heading) then you do have to turn with the rudder and used opposite aileron to hold the planes wings level with the horizon; looks unnatural but works. One other comment, after you get it trimmed out, you may find you can benefit by making minor changes in downthrust. All of mine require about 5 degrees downthrust to prevent zooming with sudden power increases.

DB has describe his cub's behaviour a few times. I beleive it is a quirk of DB's cub.

Are you sure your cub will skid without coordinated rudder? I would have expected it to slip through the turn.




Discipline, and other duties, may conspire to prevent me from replying... I've hit 1000 posts

Good bye for a while.

OK I don't want to sound stupid but I'd rather understand then not, so here goes What are skidding and slipping in a turn?

I suspect that DBCherry is holding rudder in the turn, which will certainly cause it to tighten up. The proper use of rudder is to simultaneously apply rudder and aileron to bank into the turn. Then once the bank is established, move both controls to neutral. In steeper turns some up elevator is required to keep things in balance. To stop the turn, simultaneously apply rudder and aileron to level the wings.

That being said, a wide flat wing like the cub will tend to over bank if the turn is very steep because the cub, like most full scale light airplanes, is spirally unstable. Usually a little more up elevator is sufficient but in steep turns, a little aileron against the turn may be required. In that case, a little rudder opposite the turn simultaneous with the aileron is correct.

In a turn, if the airplane is moving sideways toward the low wing, it is said to be slipping. If it is moving sideways in the direction of the high wing it is said to be skidding. If it is moving with no sideways motion the turn is said to be coordinated. If you were sitting on board the aircraft, in coordinated flight, you would feel no side force, In a slip you would be pulled toward the low wing, and in a skid you would be pulled toward the high wing.

Pilots of full scale aircraft (unless they are doing aerobatics) try to fly coordinated because it's more comfortable for them and their passengers. It is also more efficient because there is less drag. R/C pilots usually don't care because they don't feel the side force, and it is hard to detect visually unless it is pretty extreme.

(From Private Pilot's Guide Glossary)
Skid - "Sideward motion of an airplane in flight produced by centrifugal force."

Slip - The controlled flight of an airplane in a direction not in line with its longitudinal axis.
(the word is "controlled", not necessarily "coordinated". ) Properly used, slips are helpful, and fun.

DB said he had to use opposite aileron while IN the turn, not to start the turn. So, as Lou wrote, might be due to overuse of the rudder IN the turn. We've all done it.

Ok, we've taken off, flown the Cub, now let's land it. Main wheel landings are cool, and the preferred method, but since I have tall grass, (pasture) I like a long shallow approach, a little power, float it in slow and 3 point it. I've not experienced any bad habits on cross wind landings, though others may disagree.

BO

Den B,
I hope mine looks that good when finished!

All in all, can this bird (84.5" WS) be considered a good choice for a second plane?

Thx.

Dano13

Rodney,
I'd challenge you to fly my Cub and NOT use opposite aileron once in the turn, but I don't want to lose the plane.

LouW,
Thanks. I've flown a lot though and always coordinate rudder. I start my turn with a bit of aileron (into the turn), then almost simultaneously) apply a little rudder to keep the tail in line with the turn, releasing both once the turn is established. Both controls are now at neutral. The Cub's turn will continue to tighten (into the roll/turn) unless I apply opposite aileron to prevent it. Not a lot if done early enough, but necessary throughout the turn.

It may well be inherent in this plane only (it's an 80" Thunder Tiger ARF that I bought from an RC magazine reviewer), or it may be something with the Thunder Tiger, but it is a real phenomenon. It's my first Cub, so I presumed it was more common than it now seems.

For those who are considering the causes, I can rule out sticking control surfaces, bad servos, or binding linkage for you. The plane is also "perfectly" straight, vertical stab and rudder are perpendicular to the horizontal stab, and the stab is in line with the wing.

I would believe that there's increased drag in the low wing which slows it further, thus tightening the turn, but the reduced lift on the high wing should prevent that. Oh, and there is aileron differential (more up than down), although maybe more would help.

One other thing; the wing does not appear to have a twist to it, and the affect is the same when turning in either direction.

Thoughts?
Dennis-

I reread DBCherry's original post. I see he said opposite aileron.... I was thinking opposite rudder when I replied.

I learned to fly gliders last summer (the sit in type). We had to hold a bit of opposite aileron in during a turn. Just a bit of pressure on the stick. Otherwise, the turn tightens on it own. Something do to with the plane's spiral stability? It was a Schwiezer 2-32. It surprised me to begin with. After a while you don't think about... and just hold in what ever is required to maintain bank and keep the yaw string straight.

So I wouldn't be surprised, based on my limited experience, if a cub required a bit also.

The reason to use rudder “simultaneous” with aileron input to coordinate the turn is to counteract adverse yaw. The adverse yaw appears as soon as the ailerons are deflected so the rudder input should be applied at the same time. It disappears as soon as the ailerons return to neutral therefore so should the rudder. If opposite aileron is required to resist over banking, a little opposite rudder is required to overcome the resulting adverse yaw. The reaction you describe is pretty typical of similar full-scale airplanes I’ve flown. If the controls are released in a Cessna 150 after a coordinated turn is established, it will be in a 60 degree spiral dive in less than a minute. A slight opposite aileron is required to resist this. A Cessna 172 behaves likewise. On the other hand a Cessna 170B will circle indefinitely without tightening into a spiral dive. A Corben Baby Ace will fall off in less than half that time. I don’t have much time in a J-3 but the PA-18 similarly requires a little opposite aileron in a very steep turn. This general lack of spiral stability is of no real concern since it is easily controlled and it makes the airplane a little more comfortable to fly, especially in turbulent weather.

Most of this is rather academic for R/C models since the operator is not on board and cannot feel the subtle forces a small lack of coordination produces. Just apply whatever control input the airplane needs to make it do what you want it to. And don’t worry about it.

(With enough aileron differential, you can ignore the rudder altogether for coordinating turns, since adverse yaw would not exist)