fixed ports

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Scott

Scott

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Sep 24, 1997
242
Hunter 31_83-87 Middle River, Md
I am replacing the fixed ports on my 86 h31 for the second time. I am using lexan, and would like the opinion of a structural engineer. I know you're out there! These ports were replaced about 10 years ago and subsequently cracked - starting at the drill holes for the screws. This time I intend to slightly over-drill the holes in the lexan in an attempt to prevent "early cracking" and failure, and will only "snug up" the screws, instead of really tightening as I did the last time. A knowledgable opinion please. Scott s/v Common Ground
 
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Steve Dion

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Dec 2, 1999
15,184
Hunter Vision-36 Rio Vista, CA.
Mark Plastics in Corona, CA

Scott: Check out Mark Plastics in Corona, CA. There is probably a reference in the archives. He makes them with a frame and the replacement plastic too. The lead time is a way out so order soon if you want them before the sailing season starts.
 
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John

Same Problem

Scott, where are you having your ports fabricated? I have the exact same problem on our 1987 H31. A local shop in South Jersey will fabricate them for me reasonably, but like you I do not want a repeat of this. Good luck.
 
Scott

Scott

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Sep 24, 1997
242
Hunter 31_83-87 Middle River, Md
John, I got prices for lexan ranging from $2-$3 per sq ft. Called a local plastics shop in Harrisburg, PA, and he quoted me $25 each, cut to specs. I have not had a chance to get to the boat to make a template for him yet. When I take it in, and he stays with his quote, I'll let you know and send his name and phone number. It seems quite possible to me that at $2-$3 per sq ft., and ~5 sq ft., he can make some simple cuts and make money. Scott
 
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Fred

I'm not a structural engineer, but I have

installed a couple of dozen lexan windows and hatch lights. The first ones cracked at the screws because I made them too tight. Lexan swell and shrinks with temperature, so the holes have to be oversize, bedding must be flexible, and the holes need to be filled with the flexible bedding compound. Sikaflex and 3M 5200 are the most common bedding compounds. There is a softer Sika product and another softer 3M product that I don't remember the numbers of, but they may be better. I have had good luck with regular Sikaflex. Because of the movement, Lexan will probably need to be rebeded after 5 to 10 years.
 
Scott

Scott

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Sep 24, 1997
242
Hunter 31_83-87 Middle River, Md
Thanks alot Fred for confirming my suspicion re. cracks and for the info. I plan to use 3M 4200 to re-bed.
 
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Jeff20979

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Sep 9, 2005
61
- - St Joseph, MI
Points about oversized holes and flexible caulk both critical. Lexan has a high coefficient of expansion, as does plexiglas. Lexan is available with an anti-UV coating. This lessens the tendency to turn brown and become brittle with age. I suggest you ask for a price on it as well. 5200 seems to get too hard to be a good application here. Polysulfides and polyurethane caulks stay pliable for 25 years in exterior applications but I'm not sure you can get them in a clear form, I never tried to buy them that way. Good Luck
 
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John

Scott

I would like info on your Lexan supplier, so do keep me in mind if all works out for you. The last time I bedded these fixed ports I used black GE silicone, maybe this was not the right application. I will be standing by. John
 
F

Fred

3M 4200 - that's one of the products

my feeble old brain was trying to remember. Should be fine.
 
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