On Thursday, January 14, 2016 at 8:56:17 AM UTC-5, wrote:
On Thursday, January 14, 2016 at 8:30:07 AM UTC-5, David Crimmins wrote:
In his flight test reports Richard H. Johnson usually included an
assessment of the glider's wing condition.
He often sites 0.004" as being a acceptable degree of waviness. I'm
assuming this is wave height, but over what length?

The reason for asking, is I'm current having my wings refinished and I want
to determine how much of the spar shrinkage needs to be corrected.
I'm thinking that a flat spot in the wing profile can be tolerated as long
as the transition is gradual. The current distortion isn't too bad and
could most likely be fixed with a extra coat or 2 of gel confined to the
spar area. However, not sure thick gel is a good idea on an asw20 with
such flexible wings.

Thanks
David

The measurement Dick did used a dial indicator mounted in the middle of a block with 2 legs 1 inch away and 1 leg 1 inch away in the opposite direction. This was described as measuring over 2 inches.
If the glider is in refinishing now is the time to contour. This is a small amount of fill if the waves are as you describe. If there is some surfacing filler being used before final finish, a couple extra coats on that area, then contour sanded out will do the job.
Good luck
UH

To clarify a bit (to help David), imagine a capital "T" on a block, the 3 "contact points" are at each end of the top bar of the "T" & the 3rd "contact point" is at the bottom of the vertical part of the "T".
The dial indicator is mounted in the middle of the vertical part of the "T"..
I believe we used nylon screws for the contact points so as to not leave marks on the wing when checking for waves.
[When the block is made and laid on a flat surface, it will contact the surface in 4 spots, the 3 screws and the dial indicator tip with the long axis of the indicator & screws perpendicular to the surface, you can easily make it in aluminum and drill it in a drill press]

As you go over the curve, the indicator will move up & down due to the curve, you're looking for rapid changes as you measure highs & lows.

Hope that helps a bit.