Tail design: V vs T vs X

[Andy W]

I have read, here and there, opinions on why one is better than the other.

Opinions include:

V keeps the stab up off the ground, but can allow a high powered model to torque on launch
T induces much stress at the root of the vertical stab but keeps the horizontal up away from the turbulance created by flaps/spoilers


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I'm sure this one will spark some comments..
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[Ollie]

T-tails have poor strength to weight ratios.

The designs by Dr. Drela, X-tail or V-tail, are the best, in every way, I have seen. The X-tails with fore horz. and vert. aft. are the best. The turbulance created by flaps/spoilers is a myth about the function of the tail, T, V or X. The subrudder lifts the horiz. tail above the ground and unloads torque of the boom.

[Andy W]

Would these all apply equally to models both large and small?
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[Ollie]

Yes, see nine of Dr. Drela's designs from 30 inches span to over 11 feet span sailplanes:
http://www.charlesriverrc.org/articles.htm

[Salto]

There's a recent thread in the Thermal forum on this topic. http://www.rcgroups.com/forums/showthread.php?t=395476

The link to the djaerotech site given by Don also has lots of info.

Graham.

[Ollie]

I should have put Don Stackhouse designs up with Dr. Drela's designs. Quote from Don:
"In a nutshell, if the three types of tail (conv., "T" or "V") are all equally well designed, then handling, stability and control authority should be essentially equal. There are minor differences, but they fall in the "splitting hairs" category. A V-tail has a little more drag than the others during a large rudder inputs, but a bit less during steady flight. Like I said, splitting hairs."

Both Don and Mark designs don't use T-tails that I have seen.

[Andy W]

Thanks for that link to the otehr thread, Graham. That really covers it in great detail.
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