Tail landing gear

[Matt Piatkowski]

Hello,
Imagine Leonidov's La-4e, RTF weight=1830 grams (64.55 oz.), standing on a hard surface of a circle.
The main gear struts and the foam of the main landing gear wheels (2.25 " dia) deflect a certain amount.
Most of this deflection comes from the deflection of ultra-light wheels.

The tail landing gear also deflects, but most of this deflection comes from bending the steel wire that constitutes the tail landing gear strut.

When the model stands on the ground and is ready to be launched, both deflections mentioned above produce the wings AOA about 4 degrees.
When the motor starts and the model accelerates, the tail gear strut gradually straightens, maintaining contact with the hard surface of the circle for about 15-20 feet. Then, if I do it right, all wheels leave the hard surface, and the model gradually climbs to the horizontal flight at 1.50-1.80 m. above the ground.

Should the tail gear wire be softer or stiffer? With stiffer wire, the model sits on the ground at 2 degrees AOA and rolls ~30 feet before taking off.
Please note that the length of the tail wire is the same - only the bending flexibility differs.
Regards,
M

[Mike Alimov]

Matt, I don't think you have explained what is it that you don't like about the tail gear and/or the resulting takeoff, and what is it you are trying to achieve.

[Motorman]

Is this a joke or something? The flexibility of the tail wheel wire??

[Mike Alimov]

Is this a joke or something? The flexibility of the tail wheel wire??

If you fly competitively, no, not a joke at all.

[Bob Hunt]

Is this a joke or something? The flexibility of the tail wheel wire??

It's not a joke at all. The flexibility of the tailwheel wire - and its length - can be a profound benefit... or problem. I prefer fairly long tailwheel wires to allow the model to sit near a zero AOA. I find it easier to land in wind if I don't have to flair the ship to a great degree to achieve a three point landing; I can just "fly it on" when landing, and then immediately hold a bit of down elevator to "stick" the model to the ground firmly. I find the flexible tailwheel wire a benefit during this process. Bob Gieseke was probably the original "tall tailwheel" guy with his Gieseke Nobler. And, he received some flak from the purists about the ground attitude of his models because they did not look like "real" airplanes in that configuration. Please someone tell me where in the rule book it says anything about the attitude of the model on the ground... But, I digress. We are talking here about the length and flexibility of the tailwheel wire.

The downside to a long and flexible tailwheel wire is the possibility that your helper when launching the plane may compress the tailwheel wire too much and when the model is released the compression rebound of the wire causes the tail to spring upward... and the prop downward! Lots of chipped props have been the result from this over the years. I always caution my helpers to not compress the tailwheel wire when launching. 

Bottom line is that this is one of those personal preference things. Use whichever tailwheel configuration you like best and can score best with.

The attached photo depicts my dear departed friend, Buddy Wieder launching my Crossfire at the 2011 Nats. Note that he is visibly concentrating on not compressing the tailwheel wire. He was a great launcher!

Later - Bob Hunt

[Ken Culbertson]

I learned about the long wheel and the arguments against it flying with Bob G. and the "Purist" back in the 70's.  Been using one ever since.  Interesting that I have had 2, that I can remember, prop strikes at contests and both times it was when someone outside our flying group was launching.  Never gave that any thought.  Thanks Bob for the technical answer!

Ken

[Howard Rush]

The downside to a long and flexible tailwheel wire is the possibility that your helper when launching the plane may compress the tailwheel wire too much and when the model is released the compression rebound of the wire causes the tail to spring upward... and the prop downward! Lots of chipped props have been the result from this over the years. I always caution my helpers to not compress the tailwheel wire when launching. 

That's one reason I'm not allowed to launch Varsity airplanes. 

[Bob Hunt]

That's one reason I'm not allowed to launch Varsity airplanes.

But, you're allowed to fly them... Weird! 

Bob

[Brett Buck]

But, you're allowed to fly them... Weird! 

Bob

You are just yanking Howard’s chain, but a lot of people don’t realize that launching them in any  significant wind is much harder than flying them, and much more risky.

Brett