Originally Posted by Thermaler

What would we do today? . . .

Joe

Balsa Breaks Better
Woodies Forever

We probably couldn’t fly R/C.

Found in an old Legion Air Kit is some Good Do's and Don'ts

Craig
Sounds like pretty sound advice for any Glider....
Gotta go plug that Tow Hook in to its own slot.
Hope all is well
LJ

Why shouldn't one build washout into the outboard wing panels?

Originally Posted by Trisquire

Why shouldn't one build washout into the outboard wing panels?

Likely because they already have aerodynamic washout owing to the flat bottom and diminishing rib thickness as the wing tapers to the tip. Adding more would go beyond the design and add unnecessary drag.

You can see this if you plot two ribs of the same airfoil and different length atop one another with the TE at the same point. Now draw the camber line from TE to center of the LE and note that the smaller rib is at a lower angle of attack than the larger rib. Voila, washout.

JT

Trisquire
Excessive washout can be a double edged sword. At low speed it does help hold a stall off by forcing a tip to stall later than the main panel.
The other end of that is the VNE speed for a a wing with washout is lower than a wing without. This is because at high speed with washout and a light weight structure a huge negative bending moment can be transferred to the main panel. I am guessing that Cecil was thinking of F3B when he added this thought. L

Originally Posted by Trisquire

Why shouldn't one build washout into the outboard wing panels?

Legionair gliders were designed with the Texas winds in mind. The tip-panel airfoil actually changes slightly in the percentage of thickness and leading edge entry point... thinning toward the tip, and the leading edge entry point actually not following that but placed to keep the angle of attack the same throughout... instead of having a natural washout due to thinning. I could almost put quotation marks around that because that was what I was made to understand, by the late Cecil Haga. In his advise, the "dos" say fly fast... and the "Don'ts" say don't fly slowly. The higher speed will negate the tip stall we're trying to prevent with washout. When I forget these pieces of sage advise, my Legionair suffers for it. They were ahead of their time... both Cecil, and his designs.

More on Do's and Don'ts from Cecil

Up turned or down turned tips will take up valuable building time

and a bit from his Construction Details on Trim and Flying (Pics)

He also pointed out there were 4 Types of Sailplaners

Sunday Flier
Experimenter
Sport
Competitor

and he hoped the ship would fullfil your Requirements

whacker
in sny Tatamagouche

Interesting. Thanks for the info guys.

Interesting discussion. Anyone that has built the original Mirage by Blaine Rawdon will note on the plans, that he suggests building in 3/8" washout starting halfway out in each wing tip. I questioned that but figured, he being the designer, knew what he was doing. At the Nats this year, I compared my Mirage to the one Barry Anderson built and his had zero washout. He said his flew fine that way. Can't say that about mine. Go figure.

Having built a Mirage back when it was designed, and I still correspond with Blaine, I would just build the wingtips flat and add any sort of washout during covering. The airfoil is very forgiving as it s quite thick. Being thick, the dependence of the angle of attack is not as sensitive as a thinner airfoil. Also, if you kept the LE sharp, that reduces the stall dependence due to the angle of attack. The airfoil is very forgiving, so if you are having issues, make sure everything is straight, there are no warps, and then add the washout. Keeping the tips light is always a benefit.

Chris

Okay guys, dig deep into the back of the mind and closet.


Looking for a set of these plans . . . ;>)


Joe


Balsa Breaks Better
Woodies Forever