I need some advice on a plexi issue.
I cut my (Van's supplied) windscreen to size a few months ago during a warm summer day (December down here), got the fit right, prepared it for installation and put it aside. I finally got around to installing it yesterday, but it's winter here now so I had two heaters going in the workshop. A temperature gauge on the workshop wall showed 70 degrees F, but the heaters were each side of the fuselage so I think the area around the front fuse was probably a bit warmer, maybe 75F. I used Lord Adhesive to glue the top side of the plexi onto the cabin top, with some light weights across the top and clips with clecos down each side. No dramas with this, the fit is really good all the way around except for the small gap all Van's mouldings have on the right hand lower side, which in my case is less than 1/8" at the widest point. I left the heaters going all night, first thing this morning the workshop was still 70F.
This morning I started getting ready to scuff and acid etch the forward fuselage area in front of the plexi, in preparation for the front fairing. Today's plan was to do this preparation work and do the fillet of micro per page 45-19 Step 1.
Almost straight away I noticed a couple of small surface cracks (crazes?) on the inside surface of the plexi. They're about 3/16" long, and definitely on the inside surface only. They're in an area where of course the angle between the plexi and the forward fuselage skin is very acute. I cut a Q-tip down and was able to get it in there and wipe it across the plexi, thinking that this might just be some lines of dust, but nothing came off so I think these are "real". I don't know whether they happened yesterday, or whether they were there previously, but I suspect the former.
Here are some pictures. The first shows the general area. The second is a "close up". Although it might appear from the second that there is a crack going right through, this is not the case, the lines that seem to be on the edge of the plexi are just shadows. I thought I did a pretty good job of sanding the edges of the plexi, but there are some pretty ordinary looking scratches on the edge in this area. Maybe the blowup just makes them look bad, to the naked eye the edge of the plexi is fine.
The obvious concern is these surface cracks/crazes could propagate over time and become real cracks. It's hard to think of ways to work on the inside surface in such an acute space. Obviously anything done would be "under" the fairing layup once it is in place, but I'm concerned that attempting to do anything at all in this area will risk making things worse.
Suggestions welcome...
Adrian
Plexi craze/crack advice
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