Calculating tail volume co-efficient

[arx_n_sparx]

Hey folks: I had a bookmark on this, but my HD crashed, and I've lost it. Does anyone have any good links on this?

TIA<

Brad

[Ollie]

http://en.wikipedia.org/wiki/Pitching_moment#Coefficient
Horzl. tail volume coefficient (Vh) is (horzl tail area x tail arm)/(wing area x mean chord). (horzl tail area x tail arm) will have the units of area x length, namely the units of a volume. Similarly (wing area x mean chord) will have the units of a volume, hence "volume ratio". Tail arm is usually measured from aircraft centre of gravity to quarter chord point of tail.

Also, vert. tail volume coefficent (Vv) is (vert. tail area x tail arm)/(wing area x wing span).

Handling suffers with Vh < 0.4 and Vv < 0.02.

[arx_n_sparx]

You're a true gem, Ollie! Those are the formulas I "misplaced".

Got anything for V tails?

TIA,

Brad

[nmasters]

DJ Aerotech has a lot to say about everything model airplane. Just enter "v tail" into their search engine (http://www.djaerotech.com/dj_askjd/) and you''ll get more than you want.

Basically they say the tail feathers should be a bit larger than an equivalent cruciform tail

[arx_n_sparx]

Great stuff, guys. Thanx again

BRad

[Ollie]

See:
http://www.charlesriverrc.org/articles_modeldesign.htm
Tail Design and Structure

[Don Stackhouse]

DJ Aerotech has a lot to say about everything model airplane. Just enter "v tail" into http://www.djaerotech.com/dj_askjd/their search engine and you''ll get more than you want.

Basically they say the tail feathers should be a bit larger than an equivalent cruciform tail

The rule of thumb is that the TOTAL area of a conventional, V or T-tail should all be EQUAL. In our experience this tends to work remarkably well, much better than other "rules of thumb".

That does mean that the span and/or chord of a V-tail will be a little bigger (same total area, but divided between two panels instead of three) than a conventional or T-tail with the same area. If that's what Norm means by "a little bigger", then that's correct.

Some folks make a big deal about "destructive interference" between the panels of a V-tail, which supposedly requires a little extra area to compensate. However, in our experience that has not been required. I suspect that the greater span, and/or the greater chord (and therefore the better Reynolds numbers) of the V-tail panels may be involved with this (as well as the whole issue of "destructive interference" being perhaps a bit overblown).