Hatch Plexi replacement

[sagablu]

Good day all,

I am rebedding a hatch and replacing the Plexi as it is old and fogged. I assume I will rebed the hatch frameto the cabin top with butyl tape, but what do I use to reseal the plexi onto the hatch frame?

Thanks!

[Captndave1]

3M 4200

[Cheechako]

Hopefully someone will chime in, I think there are products specifically for bonding the plexi to the frame.

[anchorbend]

Dow Corning 795 on Amazon

[DSDman]

I second the dow 795. Comes in white or grey

[Smokeys Kitchen]

+2 on the Dow Corning. I did my forward hatch last year with it (having never done one) and am now in Petersburg, AK for the winter. No leaks

[hellosailor]

There's a similar 3M product that is specially designed to bond with acrylics and polycarbonate. I bought one a couple of years ago and actually found West Marine sells their own label of it--for substantially more than the 3M product on the same shelf. Go figure.

Saga-
You also want to check exactly what "plexi" you are getting. The UV resistance and scratch resistance of the stuff in your plastics shop may be very low. The cheap stuff is for napkin holders and cocktail tables, not for hatches. If you're not familiar with that, ask the shop for the name of the supplier they use, and check the specs for a specific grade. Odds are you'll need to order whole 4x4 or 4x8 sheet unless they deal with it regularly.

[rom]

I was thinking about using sika 295 UV. Anyone knows how the Dow, 3M and sika compare ? It is for the saloon windows, so maybe a bit different than OP's requirement to bed against aluminum if I understand correctly.

[sagablu]

Originally Posted by hellosailor

There's a similar 3M product that is specially designed to bond with acrylics and polycarbonate. I bought one a couple of years ago and actually found West Marine sells their own label of it--for substantially more than the 3M product on the same shelf. Go figure.

Saga-
You also want to check exactly what "plexi" you are getting. The UV resistance and scratch resistance of the stuff in your plastics shop may be very low. The cheap stuff is for napkin holders and cocktail tables, not for hatches. If you're not familiar with that, ask the shop for the name of the supplier they use, and check the specs for a specific grade. Odds are you'll need to order whole 4x4 or 4x8 sheet unless they deal with it regularly.

Good point, thank you. I did consider that point. The company I used specializes in marine plastics. The guy seemed knowledgeable.

[puffcard]

Dow 795, great stuff for plexiglass.

[double u]

cheapest neutral cure silicone gave best results on many replacements

[hellosailor]

"cheapest neutral cure silicone gave best results"
Except, every silicone maker, and every plastics supplier, agrees with what I found out some years ago: Plain silicone never really bonds to plexi. It may be a good seal in compression, but it is not bonded the way a properly primed or chosen product it.

[sagablu]

Went with Dow 795, black to match the hatch frame and smoked plexiglass.

Thanks all!

[mikereed100]

Either Dow 795 or Sika 295, with primer, will work well. Keep in mind that NOTHING will work if you do not get ALL of the silicone used on the original acrylic off of the hatch. This will require not only aggressive scraping but the use of a silicone remover such as McKanica 0351.

[double u]

Originally Posted by hellosailor

"cheapest neutral cure silicone gave best results"
Except, every silicone maker, and every plastics supplier, agrees with what I found out some years ago: Plain silicone never really bonds to plexi. It may be a good seal in compression, but it is not bonded the way a properly primed or chosen product it.

we did a LOT of acrylics in my time (3 years on a base with 32 boats), & the quickest failure was with sika UV 295 plus all the specialsuperprimers: the crew pushed the lens out within a few days!
best success rate: when the headoffice sent down the cheapest neutral cure silicone, I think it was called "wie gummi" (like rubber) or so.
on our own boat in NZ: an inseal plus Silpruf
& btw: lenses of Lewmar Ocean hatches; silicone!