Pearson Boats - Common Systems > Ports & Hatches

Resealing and Rebedding Fixed Ports

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mjscottinnc:
I've started doing all four of my fixed ports and I'm wondering... The cabin thickness on my boat is 3/8" (.375) at the skinniest, the gap in between the window frame pressure ring (interior ring) and the frame's outer seal is .575". That means that we have to fill .200" with something to keep compression on the gasketing/sealing material (I'm using Butyl tape). So the question is, has anyone considered making a trim ring to fit in between the cabin wall and the pressure ring to close the gap with something solid?

Alma:
You can use your calipers to find the largest average thickness of both inside liner and boat's outside cabin sides. Then using matchsticks shim the thinner areas to match. Then use thickened epoxy to bridge gaps and make a solid unibody for the ports to fit into.

Libations Too:
mj:

I may not have understood your proposed solution correctly but if I did, the following thoughts may be useful:

1. On Libations, the combined thickness of the inner cabin liner and the exterior cabin wall was not uniform. The thickness of the the two pieces varied a fair amount and thus, the gap between the two varied too. A trim ring (of uniform thickness) placed inside of the interior liner as I believe you have suggested would seem to do little to provide a solid (no flexing) and surface of uniform thickness for the port frame to be tightened against. In my opinion, it is the flexing of the liner and/or cabin wall that poses the greatest risk to leakage. My approach was very similar to that suggested by Alma although I used longer Doug fir shims set in epoxy followed by Marine-Tex epoxy putty.

2. The second thought that occurs to me is that the the inner bezel of the port frame assembly may not be structurally strong enough to allow the screws to be sufficiently tightened to pull the exterior cabin wall, the interior cabin liner, and the proposed trim ring together tightly enough to avoid the possibility of flexing. My guess is that the bezel will deform long before you can draw the three pieces of cabin/liner/trim together. And once the bezel starts to deform, the holding power of the frame assembly is diminished. When I did the work on Libations I used several good sized clamps to hold there cabin wall, shims, and cabin liner tightly in place while the epoxy cured. Ultimately, on Libations, it was the epoxy that held everything together, not the mechanical force of the frame assembly. The screws holding the interior bezel to the port frame only needed to exert enough force to compress the butyl tape.

mjscottinnc:
I would agree with all that has been said. I'm already trying to lesson the variations in total thickness with mahogany wood shims (I have a home wood shop, I like to build furniture for a hobby)and thickened epoxy.

The idea of the trim ring is as follows: With the existing frame there is still .200" of gap when the frame is fully tightened, so we are relying on sealant to fill that gap, and .200" is a lot of gap. We are replying on tightening the inner frame to provide clamping pressure so the outside frame is sealed against the deck side wall. The smaller we make the gap the less movement, the less total reliance on a sealant. Remember, when the frame is completely clamped down, with no sealant there is a .200" air gap. If we lessened that gap to say 50 thousandths ( .050") I think that we will see a better long term outcome. Picture it, Inside wall, trim ring, inner frame. Now the inner frame is pushing on the trim ring as we tighten the screws, that has to be a better situation then before, even if there is variations in wall thickness. Besides, you will get a cute little teak halo around the fixed ports... How's that from trying to convince you? Your smiling right? I am...

Did I explain it any better, still have doubts? 

Libations Too:
mj,

Thanks for the detailed explanation. I understand your proposed solution much better now. It sounds quite workable to me...but one last question: if the screws are bottoming out before the frame assembly can be completely tightened onto the cabin/shim/liner can you simply replace the existing screws with shorter ones?

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