Dow 795 silicone vs. 3M 8609 fast urethane for Rebedding

[Dan_Y]

A search of the forums shows Dow 795 seems to be the choice for rebedding salon windows (acrylic to fiberglass). The yard has failed in four attempts to get sika 295 uv to bond even with the primer (too long and painful of story, but first attempt was supposedly ruined, meaning no cure, due to wiping it with acetone. Second tube was supposedly defective, with no cure, 3rd and 4th try the primer apparently did not help the sika adhere to the acrylic. After a month, the acrylic completely disbonded from the sika. No guarantee yard used the products correctly though.)

Has anyone used the 3M 8609 product for rebedding acrylic (cast or otherwise) to fg? It's used to bed windshields in cars. Or has anyone used Life Seal?
Thanks
Dan

 

[Steve Dion]

I think you may need to use mechanical fasteners until the product cures. Once the product cures remove the fasteners and fill the holes with the product.

 

[KD3PC]

The forums are awash with Dow, for a reason....it works - as long as it is not out of date. Why reinvent the wheel with some new product or process that may or may not work. There is a lot of labor involved, that will have to be redone, for the sake of a $7 tube.

Use the DOW 795, it is very affordable, and readily available. Car products - as good as they are, seldom hold up in marine/structural things, like the DOW does.

 

[woodster]

i will add to this

1st you have to sand the surface you are bonding acrylic and fiberglass then wipe with
denatured alcohol and let it dry
2nd you have to use this stuff applying a liberal layer (put it on heavy) on both parts
3rd you have to tool the stuff on or it will not bond well (a plastic spoon works well
4th after all the above you set the acrylic to the fiber glass and put it where you want it
and clean off the excess and then leave it alone for a couple (if you can't believe the
wet paint sign pay some one who can to do the job) of days maybe securing
it with masking tape the green or yellow scotch kind not that blue crap from the big
box store

 

[njlarry]

Only have experience with 795. It works-seals and bonds. I used 3m vhb tape to hold the sidelights in place and bricks to force the hatch light into a curve. neither will now budge an inch and both are leak free. No need to drill screw holes which sped up the project
795 also comes in 3? colors.

 

[woodster]

Only have experience with 795. It works-seals and bonds. I used 3m vhb tape to hold the sidelights in place and bricks to force the hatch light into a curve. neither will now budge an inch and both are leak free. No need to drill screw holes which sped up the project
795 also comes in 3? colors.

yes...... bronze,black and white

 

[KD3PC]

yes...... bronze,black and white

actually it comes in at least 12 or 14 colors, standard, and they can custom color it, if needed. At a price, of course, I am sure.

 

[Velero49]

I used black butyl tape, a layer in the acrylic and a layer in the fiberglass. almost like contact a cement application, you may only have one chance to align the acrylic. Probably an overkill but I had gaps up to 3/16 between the acrylic and the fiberglass. You can find butyl tape in pond/landscaping stores. The black butyl is use to repair/glue plastic liners for ponds. You have to make sure that you remove any air pockets otherwise the air will expand and break the bond over time. I then applied 795 to seal the gap between the acrylic and the fiberglass. Its been almost a year since I rebedded my skywindows. Your mileage will vary......

 

[Pat]

Dow 795 works great...it is a product of choice because it withstands changes in temperature allowing expansion and contraction without shrinkage...it comes in white or black at least. You may need to position the hatch or portlight but ours was secure over-night and has never leaked since. This was in an O'Day 272, w/ leaking portlights.
Good luck....btw, we purchased the 795 from an automobile windshield installer. Pat

 

[Dan_Y]

Wow - great responses folks. Learned several things I had not considered. Thanks!