Join Date: Sep 2008
Location: Victoria B.C. Canada
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Re: Proper adhesive/sealer for Lexan
Dow 795, GE SG-4000, or Sika Flex 295 UV with primer are the best choices.
The details are here: Which Sealants To Use
Select Plastics is the largest marine hatch repair facility in the world.
Lexan is not the best choice for a hatch unless it was lexan originally. Only Bomar hatches with the metal cross beams use lexan. Every other hatch manufacturer - Lewmar, Bomar, etc all use cast acrylic for the very reason you found. Lexan deflects when stepped on and the seal will break - regardless of sealant type. Cast acrylic is also much more scratch resistant and will last years without crazing, lexan crazes in a few years.
If you have not yet purchased the lexan use cast acrylic (plexiglass) instead for the reasons above. Lots of good information at the link posted.
Living aboard in Victoria Harbour