Sikaflex - What Did I do Wrong?

Discussion in 'Wooden Boat Building and Restoration' started by nbehlman, Apr 8, 2018.

  1. nbehlman
    Joined: Aug 2011
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    Location: CT

    nbehlman Junior Member

    I'm in the final stages of finishing my mahogany runabout project. I am in the process of caulking the gaps in the deck. I taped off the entire area then, one seam at a time, I applied Sifaflex 295 UV with a caulking gun and ran over it with a squeegee to level it. I was surprised by how quickly it cured. When I got to the end of a seam, it would be the consistency of marshmallow fluff and just stuck to the squeegee. It became a real mess. You can see from the pictures that some areas came out pretty awful, and some were just ok. Is there a trick to this that I'm missing? Is it possible to sand this stuff? I'm thinking I have to go tear it all out and try again. Is there another product that gives more work time? I just need something white to fill in the gaps and make it look nice.
     

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  2. PAR
    Joined: Nov 2003
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    Location: Eustis, FL

    PAR Yacht Designer/Builder

    I feel your paint, but why did you use a "glazing sealant" on your deck seams?

    Personally I prefer to to put this in long before the finish, but . . .

    Pro's tend to use a two part polyurethane or polysulfide. I can be applied with a gun, though a pneumatic gun speeds this up considerably. You look to have several issues, most application related. You have to stay within the working window of the product, or it'll skin over and not stick, except to the putty knife. There's a big debate about tip bevel with or against the bead during application, neither is perfict. If the tip is angled toward the pull direction, it piles up in the groove, but also gets pushed into it, help prevent bubbles and voids. If the tip is angled away from the pull direction, it sort of "pukes" out the back and trails the tip a little, but it leaves a cleaner line if you're good. Both methods have application techniques that can help their related issues. You seem to have discovered most of these issues.

    You probably already know the answer and I've been the bearer of this sort of thing previously if I remember correctly, sorry. Any area where there's, bulges, bubbles pockets, depressions, voids, etc. need to be "reefed" out of cured goo. When reapplying the caulk, they have to be completely filled, with enough extra to absorb any shrinkage that will occur during the cure. The thickness of the tape is usually enough, it's easy to be safe, then sorry on this. The goo needs to be dry, which typically takes a few weeks to be on the safe side. You also need to use a product that's designed to fill, set and sand uniformly. I'm a two part polysulfide guy, but I know of plenty of others using what they dare. Once this is done and very well cured, you can it flush with the deck and refinish.
     
  3. gonzo
    Joined: Aug 2002
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    Location: Milwaukee, WI

    gonzo Senior Member

    If it starts to set, it is time to stop and let it cure. We have all tried to push it instead of waiting and ended up with a mess..
     
  4. nbehlman
    Joined: Aug 2011
    Posts: 63
    Likes: 3, Points: 8, Legacy Rep: 50
    Location: CT

    nbehlman Junior Member


  5. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 484, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    That product is a single part polysulfide. It does work , but not as well as the two part versions at sealing seams. Reefing hooks are easily made, which works well if your seams are tight and fairly uniform. With a single part; getting it to flow from the gun, completely fill the seam and still stand slightly proud is the ticket. Application speed, gun angle and consistency will help.
     
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