Richard Lamb wrote:

wrote:

I will be happy to take you to lunch when you are in RI and I am in
airport vicinity. I will even pay for the drink if you can answer the
following simple question. For 100 points and the jackpot... ;-)

An RV-10 has a span of about 32 ft, wing area of 148 sqft and a wing
loading of 18.6 lb/sqft. It cruises at around 190mph
(optimistically). It's stall speed is 57mph.

Let's presume its wings were telescopic---which of course they are not.
Let's presume that fully extended they are still what they are. Now
presume in full flight, I could take off 1/3 of the wing. For your 100
points, how does the expected stall and cruise speeds change? [For
extra credit, assume a reasonable weight increase. hmmm...how much
does an empty aluminum wing structure weigh? I guess this could even
be fabric---it would be used only during landing.]

regards,

/ivo


Grrrr.

Ok, but don't start the clock until I hit "send"?
You left out the weight. (I Tol' you to 'Write That Down!')

148 square feet on a 32 foot span implies a chord of 5.25 feet or 63
inches.

ASSUMING a gross weight of 2700 the 57 mph stall would imply a CLmax of
2.2.
(That has GOT to be flaps down!)

Removing 1/3 of the span (.666 * 32') leaves 23.3' span
23.3' span * 5.25' chord gives (111.888) call it 112 square feet.
Predicted stall speed (with these numbers) looks like 65 mph.

ADDING 1/3 to the span gives 42.6' span and 224 square feet area.
Predicted stall speed (with these numbers) looks like 46 mph.

A guess at cruise numbers would be foolish. Too many unknowns.
And no way to break the wing drag out of the overall without better info.

Would the short wing version fly faster?
Maybe - maybe NOT - because the short wing would be flying at a higher
angle
of attack - with corresponding higher drag...

So - purest speculation....

Based on the above at cruise:
For the Van's wing, CL of .197. aoa ~ -1 degree. Cd ~ .0076
For the short wing, CL of .26 aoa ~ -1/2 degrees .0077
And the long wing, CL of .13 aoa ~ -1-1/3 degrees .008

And, most bizarre of all, the long wing version MIGHT even cruise FASTER!

HOwZaT?

By cruising at a higher altitude...
Up where the air is thinner and colder!



Ham and cheese on Rye, please?

Richard



Oh yes! As for the weight increase question...

It's still 2700 pounds gross, but it's a two seater now...


Richard