Correct sealant for large port

smokey73

smokey73

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Oct 26, 2010
2,217
Hunter 40.5 Beaufort, SC
1994 Hunter 40.5

Below are some pictures of an area I need to reseal. The first picture is of the sealant around the large fixed cabin port. As you can see its a black flexible material. It currently does not leak unless its a real downpour and then only a drip or two. The window appears to be well bedded. The second picture is with me holding it up as it is loose in the groove.

What kind of sealant do I need to use here and are there any special tips for installation other than clean out all old caulking. What prep cleaner should I use and what sealant. Obviously NOT 5200 but I am sure there is some correct product. Thanks in advance
 

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capta

capta

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Jun 4, 2009
5,074
Pearson 530 Admiralty Bay, Bequia SVG
Down here we were unable to get the DOW79. The Plexi guy in Trinidad uses only Boat Life Boat caulk and it has worked very well for us.
I would, however, suggest you remove whatever is there now and clean the area very, very well before recaulking, rather than trying to patch the leak.
 
caguy

caguy

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Sep 22, 2006
4,004
Catalina, Luger C-27, Adventure 30 Marina del Rey
Dow 795 is silicon and could be a pain getting anything to adhere. I just glued new ports on the Lugar 30. The old frames had silicon as a sealer and I had to sand and scrub with acetone. I used a polyurethane roof flashing adhesive. Easy to work with, it has just the right consistency and 1day cure time gives you time to work with it. It cures to just the right amount of hardness and skins out beautifully. I glued a test piece to the frame area and it is tough as nails. I'll post pictures later.
 
M

mitiempo

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Sep 28, 2008
922
Canadian Sailcraft CS27 Victoria B.C.
Dow 795 is structural silicone, not at all like the hardware store silicone. It is designed for this purpose.
 
caguy

caguy

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Sep 22, 2006
4,004
Catalina, Luger C-27, Adventure 30 Marina del Rey
mitiempo said:
Dow 795 is structural silicone, not at all like the hardware store silicone. It is designed for this purpose.
Click to expand
Does that mean you can easily remove it if necessary? Polyurethane is used for the same purpose but has a 9X higher tensile strength with the same 50% flexibility. It is used to attach windshields to cars.
 
M

mitiempo

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Sep 28, 2008
922
Canadian Sailcraft CS27 Victoria B.C.
S

Steve Dion

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Dec 2, 1999
15,184
Hunter Vision-36 Rio Vista, CA.
It can be removed. It just takes a lot of scraping. Once it has been removed you can clean up the area with some alcohol.

The new product sticks to most anything. You need to be sure that you mask off the area.
 
caguy

caguy

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Sep 22, 2006
4,004
Catalina, Luger C-27, Adventure 30 Marina del Rey
Steve Dion said:
It can be removed. It just takes a lot of scraping. Once it has been removed you can clean up the area with some alcohol.

The new product sticks to most anything. You need to be sure that you mask off the area.
Click to expand
The polyurethane Sikaflex, mentioned in your article, has a tensile strength of 360 PSI while Dow 795 has a tensile strength of 40 PSI. With large ports and a flexing hull/cabin I would put my money on a Polyurethane based adhesive.
 
Merlin Clark

Merlin Clark

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Oct 26, 2005
2,057
- - Satellite Beach, FL.
Find out what the manufacturer of the acrylic recommends. The new acrylic and polycarbonate I've used has it right on the paper skin to use silicone and the chemicals in poly products will attack the plastics.
When I was doing my large ports (direct to painted 'glass) the WM kid recommended either Life Seal or Caulk and I was suspicious that he didn't know any more about this than he did about anything else so I called the company. The office person assured me it would stick but had no clue if it would screw up the acrylic.
 
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