Long-lasting exterior caulk?

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kenn

kenn

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Apr 18, 2009
1,271
CL Sandpiper 565 Toronto
I tried to stuff this question into another sealant thread, but there were no takers. ;)

Our boat has a teak rubrail, and like any horizontal trim, there's a variable gap between the rubrail and the boat side. Five years ago I caulked that gap with 3M 4200, but the exposed caulk has deteriorated in the sun and elements - the surface is cracking and chalky, and pulling away from the joint in places. This happened even though the boat is covered for 6 months out of 12.

So, can someone recommend a good marine-grade caulk/sealant that won't deteriorate quickly in the elements, especially sun?

Thanks.
 
S

Steve Dion

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Dec 2, 1999
15,184
Hunter Vision-36 Rio Vista, CA.
Ken:

You may consider a silicone based caulk like DOW795. It is used to glaze windows in skyscrapers. It holds up well in the sun. You need to be aware that it is NOT easy to remove.

I would suggest that you mask off the area where you would be applying it also.
 
A

alexco38

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Sep 25, 2008
1,096
CS 30 Toronto
Butyl tape !

They've been used in hull- deck joint for many boats. Last for years and years.
 
kenn

kenn

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Apr 18, 2009
1,271
CL Sandpiper 565 Toronto
alexco38 said:
Butyl tape !

They've been used in hull- deck joint for many boats. Last for years and years.
Click to expand
Thanks, I'm a convert to butyl... for mounting hardware to deck, etc.

But it's too runny/gooey for use as a caulk - something laid as a bead along a gap, or filleted into a corner, where alot of the caulking material remains exposed, so it needs to firm up and not remain sticky.

Hope that's clearer.
 
caguy

caguy

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Sep 22, 2006
4,004
Catalina, Luger C-27, Adventure 30 Marina del Rey
I use a roof sealer that came in a tube from Home Depot. It was also butyl but formed a nice flexible/durable skin. It's been on my roof for 2 years and still looks the same. I found it in clear but have not seen it since. It was sold as a sealer for flashings.

I believe this is the same stuff. I plan on using it to caulk my rub rail on the Luger where I also have to 1/4'' gaps.

http://www.plumbsource.net/product/1709/Butyl-Rubber-Caulk.html?meta=NEXTAG&metacpg=1709
 
thinwater

thinwater

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Mar 26, 2011
3,677
Corsair F-24 MK I Deale, MD
Consider PL Window by Locktite

I've been using this on my boat for 5 years and have been pleased. It seems more durable than 4200 and nearly as tenacious as 5200. The cure time is intermediate, generally several days. It is also much cheaper (~ $5.00) tube at Home Depot) and easily available.

http://www.loctiteproducts.com/p/17...lyurethane-Window-Door-and-Siding-Sealant.htm

That said, you are bonding to teak, and I think polysulfides are generally recommended. I've never used it for that.

Like any PU caulk, you want to tape it off; it is messy stuff.
 
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bria46

bria46

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Jan 15, 2011
286
Oday 272 Waukegan, IL, Sarasota, FL
try Dow Corning 795. 795 comes in many different colors. Tape all areas with blue masking tape that you don't want the 795 to stick to the hull/deck. Let the 795 set for 24/48 hours. use an exacto knife to clean up excess overflow. Use paint thinner to smooth out/clean up remaining 795.
 
R

RedRex

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Oct 9, 2008
14
hunter 25 barnegat nj
I have used dc795 since 1988 on both buildings and boats, and I have nothing but good things to say about it except DON'T get it on your shirt. Regards, Cap'n Red
 
Maine Sail

Maine Sail

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Feb 6, 1998
11,701
Canadian Sailcraft 36T Casco Bay, ME
Guys,

Please be aware that Dow 795 is first and foremost a SILICONE.. Silicone contamination is very real and almost impossible to get rid of once cured, short of sanding or grinding it away. The only thing that lasts close to forever on a boat is silicone contamination.;) Any future re-sealings will be short lived trying to adhere to the now silicone contaminated surface.

Sikaflex 295UV (uv stabilized polyurethane) or a polysulfide like Life Calk would be good choices..
 
woodster

woodster

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Sep 15, 2009
6,243
S2 9.2a Fairhope Al
Maine Sail said:
Guys,


Sikaflex 295UV (uv stabilized polyurethane) or a polysulfide like Life Calk would be good choices..
Click to expand

how will this work on lexan to fiber glass as in fixed port light instalations Main...

regards

woody
 
Calypso

Calypso

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Mar 29, 2008
187
s2 9.2C NJ
What about replacing fixed windows that have been bed in this stuff alone? Will they not adhere?
 
Maine Sail

Maine Sail

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Feb 6, 1998
11,701
Canadian Sailcraft 36T Casco Bay, ME
woodster said:
how will this work on lexan to fiber glass as in fixed port light instalations Main...

regards

woody
Click to expand
It works well but you need to use the special primer which is an extra item to buy. Cast acrylic is a better choice though for fixed ports and 295UV can be used for these as well but again you need to use the primer. Cyro's Acrylite is what is most widely used in the industry for fixed ports and hatches.
 
Maine Sail

Maine Sail

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Feb 6, 1998
11,701
Canadian Sailcraft 36T Casco Bay, ME
Calypso said:
What about replacing fixed windows that have been bed in this stuff alone? Will they not adhere?
Click to expand
They might appear to adhere for a period of time but will eventually fail. Silicone is the same stuff they make those flexible baking tins out of that nothing sticks to.. It is imperative that all the old silicone be 100% removed before re-sealing. There are no chemicals I have found that are safe for gelcoat and that soften & dissolve silicone. You remove as much as you can physically the tape off the surrounding gelcoat with 3M film tape, to protect it, and then go to town with the sand paper or Scotchbrite.
 
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