On Wednesday, July 31, 2019 at 6:34:52 PM UTC-4, Bob Kuykendall wrote:
On Tuesday, July 30, 2019 at 9:00:34 PM UTC-7, wrote:
Can anyone tell me specifically how to tell how closely a wing is following its intended shape or to know if it has "issues"? Also, if I'm sanding, polishing or refinishing it, how do I accurately correct for any deficiencies? Asking for a friend... : )

It depends entirely on the nature of the wing. For aggressively laminar profiles like the old FX67, it can matter a lot. For others, it matters a lot less.

In my direct experience, freedom from waviness (Johnson reading below 0.004" per linear inch) is a lot more important than absolute fidelity to contour. Time spent trying to impose some sort of theoretically ideal contour with filling and sanding is a lot better spent just getting any big waves out and then concentrating on soaring strategy and tactics.

Case in point: Do a template check on any LS6 or LS8. I can probably loan you the templates for that, though I haven't seen them for a while. Anyhow, what you find is that the camber lines for the right and left wings are substantially different. The template for one wing fits the opposite wing like maybe they're from two different gliders. This applies to all of the six or eight ships I've checked, and all of them have been different in pretty much the same ways, so I'm pretty sure that's how they come out of the molds. But these are not dogmeat gliders-- they go like stink, fly arrow straight if they're tuned properly, and have won regional and national contests. Who's to say whether the right or the left wing has the correct profile and the other not? They both seem to work pretty damn well.

--Bob K.

Just to amplify what both Bob and Hank are saying, I'm currently in the midst of an LS3 refinish project with our club. While there ARE published coordinates (though even there some uncertainty exists about the intended thickness of the outer section), we are finding that there is a lot of work involved just in getting the templates correctly situated. This is a glider that won the sports class nationals last year, and so far we are finding a lot of very big deviations from the supposedly accurate profile in the outer third. It is much too blunt. The work involved to "fix" that would be significant. Could we actually make the glider worse - yup. Would anyone notice the difference if we got it "right". Probably not.

Meanwhile, we are paying a lot more attention to building up the spar lines to get rid of the shrinkage there and smoothing everything out.

We pulled the coordinates from Soaring articles published by Dick Johnson and updated later with "corrections". We cut the templates for the LE out of 1/4 inch ply on a CNC router. To do the full chord we will need a bigger router, but we've got plenty of guys in the club who have access to what we need. But, at this point (first pass of priming and filling), we're leaning toward smoothing and leaving the profile alone.

One group's experience...