Lexan Windscreen

[Skippydiesel]

Just wondering what might have caused the following symptom;

My recently installed Lexan windscreen has developed some small/short (3mm) stress cracks on one side of the front bow . The cracks are not full depth.

What think you??

[Bryan Cotton]

Did you polish the edges/corners? If not it can be prone to crack when you bend it.

[wlarson861]

Many solvents and especially auto gas will crack Lexan.

[Skippydiesel]

Many solvents and especially auto gas will crack Lexan.

Definitely no fuel/hydrocarbons of any kind - engine has yet to be started.

[Skippydiesel]

Did you polish the edges/corners? If not it can be prone to crack when you bend it.

Short answear - dont know for sure. I purchased the nearly completed Sonex from another builder. He is incredibly particular so I would think so. Will ask him.

In the mean time; Just in case the cracks were caused by uneven/over tightening, I have backed off all screws on the front bow and then tightened them just enough to stop the countersunk washer from turning.

[N43WX]

Not quite to this point, but can someone clarify the polishing of lexan corners? I haven't heard this before. Is it essentially just deburring? Scotchbrite or other? Not polishing as in using any chemicals?

[Mike53]

Not quite to this point, but can someone clarify the polishing of lexan corners? I haven't heard this before. Is it essentially just deburring? Scotchbrite or other? Not polishing as in using any chemicals?

Pretty sure he is talking about deburring or putting a slight chamfer on the edge of the hole.It is also a good idea to drill a small hole at the end of the crack (1/32 bit) as this will prevent the further expansion of the crack.

[DCASonex]

If cracks are radiating from drilled holes, might be due to lubricant on drill bit. make sure drill bits are washed clean of any lubricant or solvent when drilling lexan.

David A.

[Bryan Cotton]

Not quite to this point, but can someone clarify the polishing of lexan corners? I haven't heard this before. Is it essentially just deburring? Scotchbrite or other? Not polishing as in using any chemicals?

I sanded them smooth and also sanded the corners a little bit.

[Skippydiesel]

If cracks are radiating from drilled holes, might be due to lubricant on drill bit. make sure drill bits are washed clean of any lubricant or solvent when drilling lexan.

David A.

In my (lexan) case they are very short (max 3mm) not full depth, located together, in the bottom left corner of the forward edge of the windscreen. They are probably only 6 cracks in total, appearing to come/radiate from the outer edge of the lexan.

As indicated above my initial analysis is thet the screws may have been over tight or unevenly tightened, causing a stress situation in one location. Hence my careful retightening of each screw, until I could not rotate the countersunk washer by finger pressure.