I haven't posted much since I've been super busy and no one seemed particularly interested in the wing FEM, so I quit working on it due to the demands of work and the low apparent interest.


Anyway, one other option would be to bond in a small hat stiffener rather than a whole additional layer of skin, which would add considerable weight. The forward curved portion of the leading edge is quite stiff due to its shape, the low part is in tension so it is stable, you only need more stiffness in the upper surface of the D-tube. So, you could add material there, or add some type of stiffener.
Kenny



Hi Rick,

I'm interested to read about the wing's behaviour when you flew it at 70mph. I'm guessing the 'boink' sound you describe was coming from the upper surface of the leading edge D-section as the compression forces built up with speed.

I am vaguely hoping that I might be able to tow my CD behind the local sailplane club's Super Cub tug plane, which has a Best Rate of Climb Speed (Vy) of around 60mph (though I suspect sailplane tug pilots tend to fly faster on tow - 70-80mph?)

My existing plans are to use just two laminates of CF cloth (in +45deg & -45deg strips) in the leading edges, but I wonder now if I shouldn't take the weight penalty and use three layers for extra stiffness. How many layers of cloth did you use in yours? I've read that Steve Arndt has towed up at speeds in excess of 70mph without wing flutter or any other issues. Do you know how many layers of cloth Steve used?

Happy Christmas,

Phil.