Temperature Cracked Portlights

[svHyLyte]

I am wondering if anyone has seen this before. A friend with a yacht similar to ours returned to his boat following an unusually cold night here in southwest Florida (high 20's) last week to discover that one of his fixed ports had cracked diagonally from top to bottom. The port is a truncated rectangle, roughly 6 feet long and 10-12 inches wide at one end and 6" at the other. Evidently there was some crazing in the port before hand but I don't know whether that is relevant or not. Replacement will be a problem...

Anyone?

[David M]

Any pictures?

[beetle]

Originally Posted by svHyLyte

I am wondering if anyone has seen this before. A friend with a yacht similar to ours returned to his boat following an unusually cold night here in southwest Florida (high 20's) last week to discover that one of his fixed ports had cracked diagonally from top to bottom. The port is a truncated rectangle, roughly 6 feet long and 10-12 inches wide at one end and 6" at the other. Evidently there was some crazing in the port before hand but I don't know whether that is relevant or not. Replacement will be a problem...

Anyone?

By 'fixed port' do you mean a window that does not open? I tend to think of a port as something that opens, and are usually smaller than a 6 foot long window

I haven't directly seen such a break due to temperature alone - I have seen many cracked polycarbonate fixed windows due to incorrect installation, such as failure to allow for thermal expansion/contraction. I have not seen a cracked polycarboate port where the material is set into a frame (no fasteners through the glass itself).

What was the material, and who makes the window? Polycarbonate (lexan) has a significant thermal contraction/expansion, to handle this requires over-drilling any fasteners put through the window. Acrylics are more stable thermally.

- rob/beetle

[steve_hendry]

Was the boat an Irwin? Most of them have long windows. The two long windows in my cabin have vertical cracks, but I've been blaming that on 'optimistic' structural design.

[svHyLyte]

Originally Posted by David M

Any pictures?

The window can be seen (somewhat) on the side of the coachroof in the following snap:




More information subsequent to my original posting. It seems that the crack originated at the location of a recently replaced "sex-bolt" (aka "tube bolt") through the window, which I have learned is approximately 1/4" thick acrylic, 84" long (rather than 6' as previously guestimated). The owner also informed me that he discovered corrosion around the bolt indicating that there was some leakage around the bolt for the few months it was in place.

Based upon the foregoing, and the fact that there had been heavy rain in the daze before the "freeze", I suspect that some water might have made its way into the bolt-hole and, with the freeze, expanded enough to crack the pane which had survived 25 years of weather including sub-freezing temps in Wisconsin each winter for a number of years.

FWIW...

[steve_hendry]

If the replacement bolt were slightly thicker than original, that could be the problem. Bolts through acrylic and polycarbonate need some room around them to avoid problems.

[SailFastTri]

That shouldn't be too difficult to replace. Get some acrylic sheet of the proper thickness, trace the old piece, while protective paper is still in place cut it out with a small-tooth jigsaw or rotozip cutting tool (use a straight edge clamped in place for a fence) and finish/bevel the edge with a belt or pad sander using 100 grit paper, finish the edge with 220 grit.

Cut and finish the edge on few small practice pieces to get used to the materials and cutting speed, before you commit to more expensive mistakes.

Drill holes oversize and do not leave sheet plastic in the sun with the protective paper on, or you might never get it off in one piece.

[svHyLyte]

As others might benefit, I thought I would add a final note to this thread to report on the outcome.

Our pal was able to obtain made to order replacement windows of 1/4" plexiglass locally without difficulty. The greatest problem proved to be the "sex-bolts". These were available through BeneteauUSA for $.50 USD each several years ago but are no longer available except by special order at several dollars each. After dismounting his windows--since both sides had to be replaced to match, he needed upwards of 60 bolts due to corrosion, frozen bolts et al.

The solution proved to be 3M VHB 5962 double-stick tape which is also used to secure the canopies on several types of aircraft. This is applied directly to the plexiglass and to the coachroof sides with a primer applied to the gelcoat. The grip is tenacious and cannot be adjusted once the tape makes contact with the glass or coachroof sides so alignment guides have to be set-up in advance and everything dry-fit.

That's it. VNB only. Some may question the adaquacy of this installation but the yacht is now at the Ocean World Marina in the Dominican Republic, having made the trip from Tampa in a few weeks, essentially all to weather, in some very trying conditions that reportedly had the entire top-sides submerged in waves several times. Only one small leak at a point less than an inch long where our pal admitted he skimped on the primer because he was "in a hurry". Fortunately, that was corrected with an injection of compatable caulking--also by 3M (obtained for just such a contingency). Their next stop will be on the south coast of Puerto Rico.

In hind sight, our pal's only comment was that he wished he'd used 3/8" glass rather that the 1/4" that matched the original so that the edges of the glass could have been beveled more.

FWIW...