Seam Caulking

ttmott

ttmott

PhD in OCD
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Apr 3, 2012
8,127
Space Coast Florida
Boat Info
2006 52 Sedan Bridge
Engines
Cummins QSM11
November will be haul out time so the "to do" list is started.

One of the bigger items to get done is to re-caulk the boat's seams. I've been considering Sikaflex 295 UV for the seams.
Any good advise or experience with the Sikaflex products? Other products you have good results with?

As a note, the 3M 4000, 4200, and 5200 products are not viable; they simply will not tool with good results.

Thanks
Tom
 
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All of the fiberglass to fiberglass joints, top of rub rail, fitting perimeters, etc.

Also I'm going to re-bed all hatches but I've already selected the bedding compound; that will be 3M 4200 UV.
 
We did our boat top to bottom sections with same stuff. Took off rub rail, and exposed all the shoe box seam. It took 3 people 16 hours to do it. We used a banana knife to remove material. Replaced all screws. Stopped seam leaks. Did not do railing or deck fixtures as they were not leaking and could not get to most of the nuts out.
You may find some of the wood the screws go into soft or rotten. We had one soft section about a foot long. Did not replace it.
 
A recommendation on GE silicone II. After buying a tube of 3M at the boat store I got to the boat and said why did I just pay $20+ for one tube of "marine" UV blah blah caulk??
Found a forum discussion and someone mentioned the GE stuff being used on a high end yacht. I wound up buying some for like $6-7? a tube and two years later it still looks good. Ask me about the "marine" stuff I put on the rub rail a couple years ago. Its since turned into bubble gum.
 
I did mine with Boat Life Caulk. Kept my finger wet with alcohol when smoothing the seams and it was very easy to work with and came out perfect.

Bennett
 
Definitely do not use any kind of "adhesive" caulk like 4200 or 5200, etc. to seal the deck/hull joint; it needs to be able to freely flex as much as possible after dried. Adhesive sealant dries harder than regular silicone sealant. Sikaflex 295 is appears to be listed as an adhesive so I would not recommend. NOT using an adhesive sealant for tis purpose was a specific recommendation from Rusty Higgins at Sea Ray. I used 3M Marine Silicone Sealant (no UV designation since under the RR). Boat Life caulk is great too.

I chose not to caulk above the rubrail and removed the factory bead below the rubrail after a conversation with Rusty Higgins. Just resealed the shoebox joint and all screws, one at a time.

You can see some pics and discussion on my project here- http://clubsearay.com/showthread.php/65678-Rebedding-rails-and-cleats/page2
 
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I use Sika 291 on most boat fittings. I damp my finger with wax and grease remover smooth over and results in a perfect finish and simultaneously helps cleanup. I recall from another forum the mention of soapy water (dishwashing liquid) on the finger also works to provide a neat finish. 295 may be better for your purposes though as 291 sets reasonably quickly and so I find is better for smaller jobs.
 
I used Boatlife on some other things and it chalked up quite badly over a couple of years. It's a non-starter for me.
I'll talk to Capt. Higgins regarding silicone based caulks; I'm sure it will cost be lunch, again..... There is now a silicone/polyurethane caulking system that maybe they are using for new boats.
Sitkaflex 295 UV is listed as an adhesive/sealer. From what I understand many of the larger fiberglass boats are using the 295 for seam sealing. Maybe buy a tube and experiment....
Plan is to mask all the seams after removing the old and cleaning; this will ensure a well dressed seam.
Tom
 
All good stuff here as this is on my list as well. I plan on attempting to remove what caulk I can prior to applying the new caulk. Any advice for the prep of surfaces after old caulking is removed? I want this to look like it came out of the factory when I am finished! I am on the fence for doing the rubrail though. My boat is in a covered slip so it doesn't have much exposure. It was an ocean boat for 8 years before I bought her though.
 
HUMPH said:
All good stuff here as this is on my list as well. I plan on attempting to remove what caulk I can prior to applying the new caulk. Any advice for the prep of surfaces after old caulking is removed? I want this to look like it came out of the factory when I am finished! I am on the fence for doing the rubrail though. My boat is in a covered slip so it doesn't have much exposure. It was an ocean boat for 8 years before I bought her though.
Click to expand...

I used a myriad of plastic scrapers to remove the old caulk so as not to damage the gelcoat, used some cleaner wax and compound and did final clean with acetone. Looked like new when I was done. (see pics in the thread I posted before) Hopefully your boat has the original caulk like mine did and not adhesive a PO used or you will really be in for a challenge. Removing the caulk was hard enough. I can't imagine having to endure the same process with adhesive.
 
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ttmott said:
I used Boatlife on some other things and it chalked up quite badly over a couple of years. It's a non-starter for me.
I'll talk to Capt. Higgins regarding silicone based caulks; I'm sure it will cost be lunch, again..... There is now a silicone/polyurethane caulking system that maybe they are using for new boats.
Sitkaflex 295 UV is listed as an adhesive/sealer. From what I understand many of the larger fiberglass boats are using the 295 for seam sealing. Maybe buy a tube and experiment....
Plan is to mask all the seams after removing the old and cleaning; this will ensure a well dressed seam.
Tom
Click to expand...

Just FYI- I just rephrased a line in my earlier post to be more clear that Rusty told me NOT to use any kind of adhesive sealant for the shoebox joint. The way I had it phrased before could have been taken either way. It was late! Good Luck on your project!
 
I just did my windshield and such this spring. I used silicone and worked great. Can't imagine using an adhesive product. Good luck and take your time.
 
juggernaut1 said:
Here's a quick summary of the various options.

http://blog.dankim.com/2009/04/24/marine-sealants/

http://www.myboatsgear.com/marine-caulking-products-guide

sika guide

http://www.bluemoment.com/downloads/sikaflexmarinehandbook.pdf
Click to expand...

My research has reviewed these as well as many more sources. The key issues are the ability to tool the product to a good looking seam, UV stability, flexibility, and good adhesive qualities. Most polyurethane products skin rather fast and tend to drag and ball up when profiling the joint; the 3M 4000UV is particularly difficult. Silicones, latex, and butyl products tool well but have poor qualities in an open marine environment. The polysulfide products also tool well but about the only manufacturer that still offers these is Boatlife; again I have not had good results in the past with Lifecaulk and Lifeseal so these are out.
The only literature that talks about tooling the product is Sika Sikaflex 295 UV.
 
I just looked at the product data sheets for 291, 292 and 295uv and they all cover tooling. As previously mentioned above I've had no problems finishing 291. 292 and 295uv are more of a paste like consistency though. I'm also not so sure the 295uv is the best product for your intended application. The guide I linked above seems to suggest 291 or 292 but more likely 292.
 
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It seems that 291 and 292 are adhesive sealants based on their descriptions. Would it not be better to use a UV sealant without being adhesive or am I missing something?
 
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