When I land my plane and just as it slows down enough for the tail wheel to touch down, I lose all steering ability. If I push the plane down the street I can turn it fine and also while the tail is still in the air my rudder is able to turn the plane just fine. Something to do with certain speeds I guess? Tail wheel need to be bigger perhaps? Or do you think the main gear is out of alignment and it is magnified at higher speeds and the tail wheel can't overcome the tendency to turn?
The plane in question is Great Planes 1/4 scale Cub

Edit: Also, I have flown tail draggers before, its just this one giving me fits.

Cubs are notorious ground handlers. A few degrees of toe-in on the main wheels helps. As does flying the tail as soon and as long as possible.

When the plane slows enough that the rudder loses effectiveness, the tail wheel needs to take over. That can only happen if the tail wheel has enough weight on it. Try giving a little up elevator to nail the tail wheel to the ground.

Storm

Is this just when you are taxing or are you trying to steer as your are touching down?

Jester when I am flying one of my tail dragger s, I keep full up elevator at all times when on the ground. Once I am lined up for take off I increase throttle and slowly release the elevator as the speed increases. This allows for speed to reach the point at which the rudder takes over. I do pretty much the same on landings only in reverse.

Just when I am landing, right after the rudder loses effectiveness.

Thanks for the advice everyone, I took 12 years off from flying so maybe I used to know about holding up elevator and just forgot about it. I will try that next time.

I'm still confused. Are you having your trouble after you've fully landed and need to taxi back to the pits? If so, the up elevator is the fix along with using small blips of throttle to keep the plane moving instead of steady power. If it's during your landing rollout though I don't see why you'd need to steer then. The whole point is to keep the plane going straight, not to turn it.

I guess I don't understand you either. Theres a small period of time I am talking about in which I cannot steer the plane, I cannot keep it going straight. This period of time is right after the tail touches down. When the tail wheel is still off the earth I can steer with the rudder. However, I can steer just fine with the tail wheel once once I slow down considerably. Its just a small range of speed that I lose control and I end up hitting a curb.

Take the fuselage of your cub and look at its side from a distance. Imagine the plane taxiing across the ground. You will imagine the wind, which is parallel to the ground, hitting the elevator lifting it up. This lifting force makes the tailwheel ineffective. Now, couple that with the lack of wind on the rudder, also making it ineffective. You get what you have.

The only solution is to hold up elevator long enough for the rudder to become effective.

I have three cubs, once you master the cub all others are easy.

Watch his elevator. On the takeoff he actually lifts the tail, which I dont do. Even the full scale starts to turn. On the landing he holds full elevator keeping things straight.

http://youtu.be/xcafcV60Uck

Can anyone spot the flaw in the video reference the Cub?

SunDevilPilot

I see. So the plane is turning itself as the tailwheel touches down. I would expect your issue is a crooked main gear which has led to you tweaking your tailwheel to make it taxi straight. At the moment you are talking about, you are light on the mains and probably still skidding a bit, then the tailwheel touches down and throws the whole thing out of whack. Do you have an issue with the plane getting wonkey just as the tailwheel comes up and maybe even again just as the mains are getting light or breaking ground? A well set up undercarriage on a Cub will give you a bump of left as you advance the throttle with the tail down, then will roll straight on its own once the tail is up, then will lift off with no changes in yaw. Landings will be a straight approach and a straight roll on the mains with little to no yaw effect (unless you do it) as the tailwheel touches down.

All good advice. First off, check the main gear alignment as advised above. Check also for a dragging wheel on an axle. Second, up elevator helps immensely and is proper technique with models as well as full scale.

An issue you may have is that the tailwheel gear springs are too soft or too loose. At low speeds the tailwheel can turn, but at higher speeds the friction of the tailwheel on the ground is stronger than the springs. When you input rudder, the springs just stretch without turning the tailwheel. Then when you slow down, the friction decreases and then tailwheel can turn.

Bryan

Engine torque will make any tail dagger "hook" to the left, adding another dimension of fun.

I see thread after thread of guys complaining about how their Cubs ground handle.I went through all of this with my H9 Cub .40 size that was previously owned by a bubba that tweaked, torqued, broke, and mangled everything on it during his rather brief Cub phase. I spent a few weeks chasing that thing down the runway fishtailing left and right and yanking it up off the ground as fast as I could. When I finally did some precise measuring, I got the main wheels perfectly square (that took some channel lock work) and got it to the point that I could lift the tail and point it at the spinner and get a straight roll. That's step one. I then found that my tailwheel had been crooked to compensate for the tweaked main gear, so step two was to trim the tailwheel to taxi straight. Of course, that mean some more time with the channel locks and vice grips getting the tailwheel to roll straight without messing with the rudder trim. The reward for my efforts was a Cub that torques a bit during the initial 10 feet of a gentle acceleration and then as soon as the tail comes up locks in to a straight track the rest of the way down the runway until I rotate for takeoff at which time it torques a little to the left again. That's exactly how a Cub should handle- quirky but predictable. If you ever get any right yaw tendency there's a problem, and if the left yawing is not consistent at those specific times you have a problem. Of course, rough runways can throw a big wrench in that mix, but even then the same basic tendencies should be there.

Oh, and if you decide to go through that process, do remember to take into account the wobble of your wheels. Measure the alignment of both extremes of your wobble and tweak your gear to get the midpoint right. Obviously for our purposes tighter wheel to gear fits are preferred, but all of our wheels wobble a little because we just stick a plastic hub onto a steel shaft. It really doesn't hurt much though because under load the wheels are going to center on the axle pretty well.