polycarbonate and threadlock

[ken nougaret]

I was just finishing my doors and installing on the plane for the final time. I bought some blue permatex threadlock yesterday and put it on all my screws that hold the polycarbonate to the frame. I noticed nearly every hole cracking. At first i thought it was from the rubber seal on the door frame pushing too hard. But i think it was the threadlock causing the polycarbonate to become brittle.
Anyone have a fix for these holes or am i buying a new window?

[efwd]

Well I didn't use that and I still had two holes crack through. I chalked it up to just a tad too much torque on the bolts. The black adhesive tape isn't that firm and allows for some flex when the nuts are applied. It May be that I didn't do that good at deburring the holes on those two holes? My acorn nuts are barely tight at all. Im wondering how many will be falling off?

[PapuaPilot]

I used self locking nuts and just barely made them tight and still got some cracking.

[dholly]

Unfortunately, I think you're looking at a do over. The polycarbonate has only fair chemical resistance and is attacked by many organic solvents.

From the Permatex TDS (https://www.permatex.com/products/thread-compounds/threadlockers/permatex-surface-insensitive-threadlocker-blue-2/):

This product is not normally recommended for use on plastics (particularly thermoplastic materials where stress cracking of the plastic could result). It is recommended to confirm compatibility of the product with such substrates.

Don't ask me how I know. :rolleyes:

[jiott]

I believe the thread locker fumes cracked your doors. In my installation instructions, maybe it was in the instructions from LP Aero, said DO NOT use thread locker anywhere near the acrylic plastic. It will turn it brittle and crack.
I know it does this on other types of plastic also; I once used Loctite on some plastic bolts on my toilet seat that kept loosening up. The next morning both bolts had broke off.

I just used a little Elmer's glue on my window bolts and tightened them just finger tight or a little more. They have been on for 370 hours now and not one has come loose.

[ken nougaret]

Jim i want to see how you fit a toilet in your kitfox. Ha,Ha.
Unfortunately i missed the warning. Thats what happens when 5 yrs go by and parts and papers are spread everywhere. The elmers glue is a good idea.
For now i drilled the holes to 1/4" and used shoe goo to glue 1/4" o.d. clear tube in the holes. Then i used some larger white plastic washers on my screws. Time will tell.

[jiott]

Well Ken, you know that storage bin that is under the pilot seat. A little creativity and some chemicals in there and Wa-La. STI says use only with no passengers and no turbulence.

[efwd]

That's brilliant Jim. No chemicals necessary though . That's a perfect spot for the leg bag connected to a condom Catheter! For the more adventuresome you could use a Foley catheter for a more secure fit. LOL.

[mr bill]

At work, the technicians used an enamel (glyptal) to lock threads. Works great, although any non acrylic enamel would work.