Lexan Hatch issue

[YellowScorpion]

Hello prime!
I've bought a SOS lexan hatch with the carbon scoop mid last year when they were being reproduced. having it sit in my garage for a bit, feeling uncomfortable with drilling into my hatch frame. my mother decided for Christmas she would have it installed by a professional shop. Last week after getting the car from said shop and driving it about 45 minutes home i noticed about 13 fractures along the lexan all surrounding the bolts that attach to the frame. My family has had SOS lexan hatches and scoops on previous NSX's and i know that the lexan is fairly resistant to cracks. After noticing the cracks and taking pictures I called the shop and spoke to one of the owners. I was told that "thats the nature of the beast" and to expect these types of fractures. On 2/9/21 i called SOS and spoke to someone by the name of Wade and was told that the lexan should not fracture under normal driving conditions being the drive from the shop to my home on the freeway.
Has anyone else with this new run of the SOS hatch experienced this drastic of fracturing? Also a side note apparently some of the bolts that were tightened on the hatch were left intentionally "loose" while others were tightened to touch the lexan. I am just confused and disappointed that after all the money spent on both the hatch and the install, im left with a damaged end result.

 

[Big McLargeHuge]

Were the hatch bolts over-tightened? That's the first thing that came to mind, especially since you said the cracks are all around the bolt locations. That would be an installation error by the shop.

Did they tell you they left some bolts loose on purpose, or did you find that out after the cracks happened? All the bolts might've been over-tightened, then it caused cracks, then the cracks might've relieved the stress on some bolts which let them loosen up by themselves.

 

[Old Guy]

Polycarbonates have a very high rate of thermal expansion. About 3 times as high as aluminum and 6 times steel. As a result, when you fasten polycarbonate to steel or aluminum the mounting holes are normally drilled with extra clearance around the fasteners. This allows the polycarbonate to float at the fastener locations. Do the SOS instructions make any provision for clearance in the hole in the lexan to allow for expansion? If they did, did the shop follow those instructions?

The other thing that I have observed on polycarbonate products is that when fastened the polycarbonate is often fastened with nylon fasteners and the material is sandwiched between 'plastic' facing washers. The nylon screws have a coefficient of expansion that is similar to the polycarbonate so eliminates the compression issue that can cause cracking as the polycarbonate contracts around an unyielding fastener if there is insufficient float. The washers distribute clamping force at the hole and facilitate movement of the polycarbonate around the mounting points (if there is clearance at the mounting holes).

As I recall from looking at their website a long time ago, the SOS kit comes with fasteners, drills and taps and I would presume installation instructions. My only suggestion would be to look at the instructions and then look at the hatch to see if it appears that the installation shop deviated from the installation instructions or used different fasteners.

 

[YellowScorpion]

we were told that they left some loose intentionally. Some most definitely some were over tightened. i have emailed SOS and am waiting their response just to have their statement in writing.

Were the hatch bolts over-tightened? That's the first thing that came to mind, especially since you said the cracks are all around the bolt locations. That would be an installation error by the shop.

Did they tell you they left some bolts loose on purpose, or did you find that out after the cracks happened? All the bolts might've been over-tightened, then it caused cracks, then the cracks might've relieved the stress on some bolts which let them loosen up by themselves.

 

[YellowScorpion]

This new run of Hatches have come predrilled from SOS so i would assume they had accounted for the expansion. However they still included taps, drill bits, and fasteners in this kit to attach the hatch to the frame. it appears that the shop had used the included fasteners to fix the poly carbonate/ lexan hatch to the frame.

Do the SOS instructions make any provision for clearance in the hole in the lexan to allow for expansion? If they did, did the shop follow those instructions?
As I recall from looking at their website a long time ago, the SOS kit comes with fasteners, drills and taps and I would presume installation instructions. My only suggestion would be to look at the instructions and then look at the hatch to see if it appears that the installation shop deviated from the installation instructions or used different fasteners.