All the LE sheeting has developed a starved horse look. I have no idea when, how or why. I've been on and off this build.
The plane is and RSM Naughty Girl. LE sheeting glued with titebond. 3-4 coats of 50/50 non tautening nitrate, polyspan attached with same. 3 more coats of the 50/50. I set it aside for a month or so before going back to it.

My questions are what caused this and can it be fixed?


Thanks
David

I fly small and I use DocSpan..so this may not mean much on the big stuff typically seen here.

How much swag between the ribs have you got?
I'm guessing the sheeted edge sits across ribs in open space just below the crown of the rib, without closing in the backside of the LE?

I get the same thing with tissued LEs and recognize as the covering is pulling across the wing, it is also pulling fore/aft (thus down) between the ribs..from LE to TE. That fore/aft part is doing a fine job of straightening out/pulling down...more/better than the straightening out/pulling across from rib to rib.
I saw this happen to an extreme on a kit I really wanted to finish, so I laid into it with fresh, really cut thin nitrate dope and a hair drier trying to shrink between the ribs more. Now I have a yellow non-flying Pringle.

For my little guys, I accept it and move on. My next few small planes will have one or two small stringers across the ribs from the rib's high point or spar to LE just so shrink going side-to side-will have a better chance of beating fore-and-aft shrink. I suspect it will be minimized for a while yet never beaten for long.

This may not be the lightest way to go and it certainly isn't a permanent solution (unless you close in or brace an open-at-back LE)...cut the covering away from the open space and recover dry, skip shrinking for shrinking's sake, and repaint. Take care to avoid significant shrinkage, which may entail including a flex agent.

Oh did I mention I build entirely too heavy?

It may be the titebond with the very lite, 6#, a grain balsa in the RSM kit. I build all my wings with LE sheeting the same way. This is the first time this has happened. The others were also covered with kote. Most kits I've built have heavier balsa. Maybe thin the titebond next time?

I had the bright idea to brush straight thinner,  Randoloh, on the LE sheeting. The balsa did spring back some.  I brushed another coat and will check it tomorrow.

My wife did not care for the name of the plane. I added a balsa teipler and sheeted the wing tips Doug Moon style. Told the wife I'll rename the plane. Haven't told her the new name will be Reformed Naughty Girl..........

Titebond will soften somewhere between 150 and 200 depending on the source.  If you were to use a Monokote iron and run it over the ribs slowly it might soften the titebond and shrink the Polyspan.  If you have the polyspan grain spanwise it would pull the balsa up.  This is 100% theory.  I don't use anything but CA and Epoxy on sheeting and I don't use light(<5) or heavy(>7) wood either.

You can always use panel lines on the highpoints to make the horse look well fed. 

ken

It's what I'd call a C-tube. No shear webs.

The thinner trick didn't work. Guess I'm stuck. It's not as bad as a Twister wing with no half ribs covered with kote. I'll tell the appearance judges that the LE dips are areo enhancements similar to VGs.

Yep. I mold the wet LE sheet over a solid form by Bob Hunt’s method, then stick the shell onto the ribs after it dries. This probably helps, but I have been sneaking extra ribs into the wing after it’s built.

When I use polyspan, I attach it to the wood only around the edges, using clear dope.  I let that dry then I shrink it with the Monokote iron.

Maybe doping the polyspan down to all the sheeted areas before shrinking it would cause your problem.  If the polyspan is stuck to the sheeting, then you shrink the polyspan, the shrinking of the polyspan might take the wood with it, if you know what I mean.