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Old 12-26-2008 | 11:07 AM
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Craig-RCU
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From: minneapolis, MN
Default RE: toe in


ORIGINAL: Flyboy Dave

I've been flying Cub's for over 35 years. They can be the hardest of all
planes to take-off if the wheels are not set correctly....it's just the way they are.

With the wheels set the way I described, they set up an equal amount of drag.
If you have ever taken a skiing lesson....the idea is the same as the "snow plow"
technique...where the skies are tilted and pointed inward to gain stability.

If you want to see a totally uncontrollable Cub....set the wheels perfectly straight "up",
then turn both wheels "out" just a tad....

....you will find out what a ground loop is all about.

Take-off tips I have been successful with:

Only use 1/2 throttle until you pull the plane off the ground, then apply more throttle.
Start the take-off roll out with 1/2 right rudder applied, and full up elevator for the first
15 or 20 feet. The "right rudder" and keeping the tail wheel on the ground will keep the
plane from veering to the left from th prop/engine torque. Some right thrust in the engine
is always desirable with a Cub as well.

Once the place rolls the 15 to 20 feet, release the elevator and allow the tail to come
off the ground. At this point you should have enough speed so the rudder will be effective.

Release the right rudder as the plane starts to move to the right...keep the right applied
until this happens. The trick is having the correct amount of steering (rudder) and the correct
amount of throttle to keep the plane going straight until the speed is right for take off.

Increase the throttle very gently as the plane lifts off...and don't lift off until you have some
decent speed.

I think one of the reasons I've always had a Cub is because they are challenging to fly. My
last one was a built up clipped wing Goldberg Anniversary Cub with a Magnum .91 four stroker
in it. I had it for about 15 years, and sold it to a friend who wanted it. It was built like a tank.

I have a new kit in the pile....I must build it soon.

FBD.
I've had success with toe out in my H9 Corsair's gear, so I'd thought that I'd throw my hat into the "great toe in/out debate." I even made a neato-swell diagram and everything too. One thing that I would say about my diagram is if throttle is applied too abruptly at take off on a taildragger with toe out, the torque of the engine will cause a weight shift to the left main and that will accentuate any left ground looping tendencies. With gradual throttle control, the stability dynamics shown in my diagram should be in effect. Another thing about the diagram is that when the mains are the only wheels touching the ground, the vertical stab serves the same function as the tail or nose wheel as the case may be.

I did some research and found that many full scale pilots recommend toe out for taildraggers too. They even mention that some cars have toe out too. http://www.mombu.com/aviation/aviato...n-1400001.html Post #8 in this thread http://www.rcuniverse.com/forum/m_48.../tm.htm#488183 said that toe out worked on his narrow geared spitfire.

I don't think that the above analogy of a snowplowing skier is good because skiers can shift their weight around (fore and aft and left and right) thus changing the steering qualities of their "wheels" in a way that airplanes can't. The inward pointing of the skis is mainly done because the inward pointing skis force the knees against each other and requires less muscle strength to hold that position than outward pointing skis. As with my diagram below, the skier's direction is based on the ratio of weight on each ski. In a plow, the skier can go left by putting more weight on the right ski.
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