My coverall directions read 'grain runs parallel to finished edge'. Can anyone elaborate on this mistery?

Maybe they are talking about the grain pattern in the fabric lining up with the exposed edge of your finished seam?

Sounds to me like the grain would run parallel to the leading and trailing edges of wing, and parallel to the length of the fuse.

I think you can find an answer here: [link=http://www.mat.uc.pt/~pedro/ncientificos/artigos/techbal.html]Grain and stuff[/link]. Just scroll this page all the way down...

It is description of the structure of the material. Depending how material was (is) cut you can get different material to bihave differently.
Sometimes material with different grain direction combined for strengths.

Good luck.

Not familiar with coverall, but if it is covering like any other, the finished edge is the left and right edge looking at the roll, meaning the grain would run the leangth of the roll. Sometimes it is easier to bend around corners if you have the grain running a certain way.

Normally covering material is fabricated in a certain way. Rolled, extruded, or something. The bottom line is that there may be a "grain" to the material. What this typically means is that when shrinking the covering, it will shrink more in one direction than another. Try it for yourself. Get a scrap piece, draw a circle on it, shrink it. Is it a circle now, or an oval?

When covering open bays in a wing, it sometimes helps to have the grain run the length of the wing. This is because the wing surface is curved from LE to TE, but flat from root to tip. When shrinking the material it will pull tighter between the ribs than from the LE side of the bay to the TE side of the bay. The shrinking from the TE to LE sides of the bay will pull the covering down into the bay a bit (because the covering wants to take the straight-line from the TE to LE and not follow the curve). If you run the grain from root to tip the "sagging" will be less than if you run the grain from LE to TE.

gus