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Old 02-01-2019, 12:49 AM   #1
BruceK's Avatar
Join Date: Oct 2011
Posts: 10,866
Disappearing Window Seals

Recently we inspected a boat with the windscreen glass set in a rubber seal encased in metal framing. A number of windows had missing corners of rubber seal, and there were gaps in the seal on straight sections as well, perhaps at joins. I could see down to framing underneath. We rejected the boat for multiple reasons.
Our first powerboat came with slugs of silicone slathered by finger on the inside bottom of the windscreen frames. Inspection outside showed rubber seals with gaps on long sections, and missing corners of seal, top and bottom.
These defects could admit water which among other issues can lead to rot. So, where does the missing seal go? My thoughts:
The corners are separately made and glued into position.The glue fails, but where does the formed up corner actually go.
Gaps in long sections could result from a join failing due to age related shrinkage(let`s not dwell on that too much).
My solution with our previous boat was to get a big tube of sealant, it can be polyurethane or even a form of silicone(it`s not going to be painted),mask up, and pump it into the corners, formed to resemble the original profile. Same for the gaps in straight sections. Needs to be color matched, the seal is usually black, so easily done. It worked a treat, no more water entry, and looked good too. I was also repainting the anodized metal windows,whatever I used as sealant was paint friendly(pretty sure it was a silicone, the plumbing version takes paint). I got silver paint on it in a few spots and touched it up with black paint where it would not come off.
Many windows have covers and are not regularly seen, so a check now and then is indicated as it`s likely these are not isolated events. The boat we inspected recently had so many black covers it resembled a Venice water borne funeral hearse.
Not hard to deal with if it occurs. Ignoring the gaps could lead to water entry problems we can well do without.

2005 Integrity 386 "Sojourn"
Sydney Australia
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Old 02-01-2019, 06:30 AM   #2
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Join Date: Oct 2007
Posts: 20,498
"Recently we inspected a boat with the windscreen glass set in a rubber seal encased in metal framing."

This is a common construction in bus and MH.

When the rubber dies and is being replaced , the installer can make the mistake of pulling the rubber into the channel , stretching it a bit.

Over time the rubber will shrink back to its mfg length and the corners or joint will be opened.

Its a bigger fight for the person installing the rubber if the lengths are cut 1/2 in or more longer and pushed into place , but worth the effort. Dish washing soap is a good lubricant .Once in the outer frame a string is laid in the grove, the window seated the string is pulled to get the lip to cover the glass.

Rubber cement seals cut corners and joints .

Just like the O ring on your fuel fill, rubber and other sealants have a service life , and need PM.
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