Rag and tube construction and computer models?

Stealth Pilot wrote:

On Sat, 10 Apr 2004 16:06:27 GMT, Richard Lamb
wrote:

hedge trimming

From the plans, the CG Range is 15% to 28% of the chord.
Figuring the chord as 48 inches, that means 7.2 inches forward limit,
(aft of leading edge) to 13.44 for the aft limit (also aft of LE).

(That 15% forward limit seems awful far forward to me - but it woiks)

the actual flight tested values for my aircraft are 10.4" forward
limit and 16.5" aft limit.


That sounds like a lot more reasonable range to me.
20.8 to 34.3 percent chord.


1300lb auw (well actually 590kg with an empty weight of 362kg.
empty cg moment arm is 214mm.

See, THAT's the problem with the metric system...

Is that supposed to be mm, or cm ???

Also, where is your datum for this measurement?

Knowing where the datum is located, we could "load 'er up"
and really see whazzappening.


hedge trimming

But different assumptions will give different results.
All depends on how valid our assumptions are at the beginning...

I'm real skeptical that the tail on the Tailwind is producing an
upload at high speed. The airplane handles too well for that to
be the case.

Remember that the leading edge of the stab is probably a little nose
down. Full forward trim _should_ still result in a net down load on
the tail.

I tend to agree although I'm sometimes not sure. I'd love to see a
windtunnel test on the "new" aerofoil to see just what the pitching
moment was.

Man, me too. If we had solid numbers on the airfoil it would be then
be possible to do a little comparative shopping.

This one has the thickest part of the airfoil WAY forward.
Contemporary theory moves the thickest part of the airfoil aft
to increase the laminar area on the front of the wing.
THIS one can't possibly have that much laminar wing flow.

Steve's airfoil is supposed to be a TLAR modification.
Something like a 2309 top curve and M6 (or?) bottom?

Like someone else pointed out in another thread,
TLAR is definitely in the eye of the beer holder...

On the other hand, we _are_ talking about the Wittman Tailwind.
The little airplane that somehow flies better than it should.
I'll bet a steak dinner it's not just the airfoil.

Richard