Lewmar opening port in Fixed acrylic panel

[Sailmonkey]

Ok, I have an Allied Seawind II that I've been fighting main salon ports in for 2 years. the original fixed ports are of the variety of Alu frame with acrylic lenses. I have had the frames and lenses out already, new lenses, etc......they still leak after some motion and don't let in any air. I would love to replace them with opening ports, but the holes are bigger than any ports I can find (8"x28"). My next thought is to attach acrylic to the cabin sides using either straight DOW 795 or the 795 combined with some 3M monster tape. Now the kicker, I'd like to put a small lewmar port in the middle of the acrylic window to allow for some ventilation.
Is this a good idea? Can the acrylic glued to the cabin sides withstand the pressure of pushing the port closed? will the acrylic be strong enough to hold a port attached to it?

[Sailmonkey]

bump1

[jstevens]

Sailmonkey,
What you are describing is something I did on my previous boat, a Columbia 8.7. The ports persistently leaked no matter how often I rebedded them, and of course they provided no ventilation for the cabin.
My solution was to screw and bed 3/8' acrylic to the outside of the cabin and then install Lewmar Ocean opening portlights into the acrylic. No more leaks and I had good ventilation in the cabin.
I sold the boat 15 years later and the current owner still has the ports after his 11 years of ownership.
I can't say it was an elegant solution, but it worked.
http://www.svsarah.com/Images/VelaLlena01.jpg

John

[Sailmonkey]

John,
So there was no problem with the ports supporting the lewmar ports? I think what I finally do may be a little more elegant than that (same shape as the existing ports) and maybe not 3/8" as the spanned area is small.
Although maybe the 3/8" should be used to add strength...........I'm just not all that comfortable with the perceived strength of the acrylic, although I know that it's plenty strong at 1/4"

[jstevens]

No problems with the strength of the acrylic. 3/8" was the minimum thickness for the Lewmar portlights.

John

[Sailmonkey]

Ok then.......what about the joining of the acrylic to the cabin side? I would like to avoid screws if at all possible. Is the adhesive strength of the DOW 795 by itself sufficient to take a load like this?

[jstevens]

Don't know about using adhesive. I used screws and lots of GE Silpruf (silicone).

John

[sy_gilana]

Just make sure the screw holes are about 10% bigger than the screws to allow for differential expansion.

[Dave]

Originally Posted by Sailmonkey

Ok then.......what about the joining of the acrylic to the cabin side? I would like to avoid screws if at all possible. Is the adhesive strength of the DOW 795 by itself sufficient to take a load like this?

Lots of new boats have openning ports mounted in acrilic windows and lots have glued in windows. Keep in mind that the hulls were designed for this with a recessed flange to glue onto and sufficiently reinforced because the acrilic / hull joint will be subject to flexing. The adhesives are often subject to UV degradation which is why many cats have exterior-snap on window covers.

You may have already done this..but search around for window re-bedding and see what comes up. There's been a lot discussion out there, it's a nasty job on some boats.

Manufacturers will have detailed procedures/instructions/adhesives regarding their installations.

Dave L38 #38