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Thread: Sikaflex 295 UV Problems

  1. #1
    Join Date
    Sep 2011
    Location
    Eagle River, Wisconsin
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    93

    Default Sikaflex 295 UV Problems

    Hello All,
    I saw on Snake Mountain Boat works youtube video that they used Sikaflex 295 UV in their deck seams.... This product says it's paintable and the company said that you should be able to apply over it once it has created a skin.... Well it's been over two weeks and varnish will not dry on this stuff.... I've varnished the whole front and rear decks, the next day the varnish is rock hard except for the varnish that has thinly covered the sikaflex.... soooooo, I tried Petit topside gloss paint, checked it the next day and again it's still sticky....touch it with your finger and you pull back color on your finger tip....

    Help!!! this is really holding up my varnishing job.....

    Oh, the black sikaflex is rubbery, flat in color and very touchable....seems fine...

    Thanks for your time,
    Mike
    Eagle River, Wisconsin
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  2. #2
    Join Date
    Dec 2005
    Location
    Home Port Washington DC but now wandering around the US West Coast on our Schooner
    Posts
    1,203

    Default Re: Sikaflex 295 UV Problems

    The Tremco company owns Sikaflex (or visa-versa can't ever remember ) and we've used both aboard to bed a few things and between covering board/toe-rail and deck. We were told that this kind of material, a silicon-modified-polyurethane needed to be painted because UV will degrade it. When first applied in 2008, we noticed the problems with varnish drying on those varnished items. No problems with traditional enamel paints though. We've bedded a few new things onto the deck using it (pads for padeyes etc) and noticed the same varnish problem but not paint. Over time, when sanding down to bare wood and re-varnishing, there wasn't the same problem. So I surmise it is something that will remain a problem for a couple months drying time. That's not helpful to you I imagine but that was how it was for me.

  3. #3
    Join Date
    Sep 2011
    Location
    Eagle River, Wisconsin
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    93

    Default Re: Sikaflex 295 UV Problems

    Thanks for the reply redbopeep... I'm wondering, that instead of waiting for this stuff to fully cure, do you think if I apply some black enamel paint over the sikaflex to create a separation barrier between the 295 and varnish I could get on with my varnishing job....hmmmmmm

    Mike

  4. #4
    Join Date
    Dec 2005
    Location
    Home Port Washington DC but now wandering around the US West Coast on our Schooner
    Posts
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    Default Re: Sikaflex 295 UV Problems

    Maybe. That's the sort of thing I'd try. You might wish to contact the company and just ask them what the cure time really is. I've noticed if I scrape at some of it that is years old and reveal new material, it's cured but more gummy than the top stuff so there's definitely a time-cure going with this stuff. PS the paint that stuck to it was a Benjamin Moore porch paint and the Kush brand marine enamel.

  5. #5
    Join Date
    Aug 2019
    Location
    Paisley UK
    Posts
    150

    Default Re: Sikaflex 295 UV Problems

    I have noticed this with the newer "hybrid" type Sika materials. It just does not like varnish or some paints as they just lie on top of it.

  6. #6
    Join Date
    Sep 2011
    Location
    Eagle River, Wisconsin
    Posts
    93

    Default Re: Sikaflex 295 UV Problems

    Just got back from ACE hardware with a small can of oil based gloss black enamel paint and painted 4 inches over the sikaflex... tomorrow will tell if it's dried...

    Thanks for the responses...What a great Forum!
    Mike
    Eagle River, Wisconsin

  7. #7
    Join Date
    Sep 2011
    Location
    Eagle River, Wisconsin
    Posts
    93

    Default Re: Sikaflex 295 UV Problems

    Well, I went out to the boat this morning (heated shop) to see if the enamel paint had dried on top of the 295 UV Sikaflex and Nope!!!! I'd set up some test areas, one being enamel paint, another type of Petite paint and of course varnish, and all were still tacky... So I cleaned off everything from out of the 1/8" kerf joints to re-expose just the sikaflex and there was one little area where the varnish adhered to.... So, I guess I'll give it another two weeks of curing (1 month total) and try again then...

    Mike
    Eagle River, Wisconsin

  8. #8
    Join Date
    Sep 2011
    Location
    Eagle River, Wisconsin
    Posts
    93

    Default Re: Sikaflex 295 UV Problems

    Update: The Sikaflex 295 UV is still not accepting varnish over it (1-month since installing in the deck joints)... It's improving slightly.... I'd say that maybe 10% of the varnish is now drying on top of the deck joints/sikaflex filled.... I've ordered some Sikaflex Aktivator 100 to apply over the 295 to see if that will help and I'll follow up with those results... Heat's on all the time with a fan blowing...
    Mike
    Eagle River, Wisconsin

  9. #9
    Join Date
    Sep 2011
    Location
    Eagle River, Wisconsin
    Posts
    93

    Default Re: Sikaflex 295 UV Problems

    Well, it turns out Snake Mountain Boat Works has had the same problem.....The problem is not with the Sikaflex 295 UV, it's with the Captains Varnish....According to SMBW's, Captains changed their formula and this has caused the problem..... I now am using Sikaflex 291 with the same Captains Varnish and all is just fine....
    Let it cure and lay your varnish on top and it's dry the next.....
    Mike

  10. #10
    Join Date
    Sep 2015
    Location
    Viroqua, Wisconsin
    Posts
    486

    Default Re: Sikaflex 295 UV Problems

    This kind of thing is why it’s always a Good Idea to do a test first, using the combination of materials you expect to use in the BIG project, but on a small scale first. There’s just no certainty in believing what you’re using is the exact same thing as what the folks in a Youtoob video had laying about when they made the clip you saw on the ‘net.

    Nice job on that deck too... too bad the Sika # you used won’t play with the varnish you want to use.

  11. #11
    Join Date
    Feb 2009
    Location
    Portland, Oregon
    Posts
    100

    Default Re: Sikaflex 295 UV Problems

    Sika has a product specifically for caulking deck seams - Sikaflex 290 DC - https://industry.sika.com/en/home/ma...290-dcpro.html

    Maybe this is what you are looking for. It is difficult to find in the US, only used on the large super yachts with teak decks here. I've used it in the Netherlands on small boats, recommended by the yard, relatively easy to use and finish. You might want to run tests on 290 DC and see if that is what you are looking for.

  12. #12
    Join Date
    Aug 2017
    Location
    Kennebunkport, ME USA
    Posts
    26

    Default Re: Sikaflex 295 UV Problems

    A month or so ago I used 291 in the seams of the deck of a Speedster I’m building with Epifanes Wood Finish Gloss over if. The drying time of the seams is about 3x that of the planks. Annoying yes but manageable as by day 2 the seams are just slightly tacky and able to take the next coat of finish just fine. After 4 coats I’ve left it to cure for a couple weeks before sanding & commencing with the next couple of coats. I surmise that the problem behind the slow drying time of the seams is that I did not give the 291 adequate time to cure as the specs say to give it a week before painting. Everything in my basement shop takes longer to cure than normal due to the low temp so likely I should have allowed more than a week vs the 5 days my impatient self allowed!

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