Float/ama hull to deck joint

Discussion in 'Fiberglass and Composite Boat Building' started by bruceb, Apr 19, 2019.

  1. bruceb
    Joined: Nov 2008
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    bruceb Senior Member

    I am rebuilding two GRP ama's for a 25' sailing tri, the decks are removed, recored, and now ready to re-attach them. There is no access once the decks are placed on the floats. The hulls have a female flange and the decks have matching male flanges.
    What should I use to "glue" them together? There is about 45 feet of joints on each hull, and I don't think I can mix/apply/control that much epoxy with out it going off too soon, particularly since it is warm weather here and I have to do the job outdoors.
    Any ideas? Also, what do commercial builder like Corsair use?
    Thanks for any ideas!
    Bruce
     
  2. Dejay
    Joined: Mar 2018
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    Location: Europe

    Dejay Senior Newbie

    I have zero experience. But maybe get some helpers, work early in the morning and / or keep the epoxy components in the fridge overnight?
     
  3. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    45 feet is nothing

    You wet the tape out on a plastic table say 16 feet long and lay it over itself 3 times or 6 times on a shorter table. Mix all the epoxy for each tape, say about 45 ounces or 1:1 by weight and then once it is wetted out onto a stack above itself; roll it onto a cardboard tube and unroll it onto the hull. For multiple layers; you can work wet on green. I have rolled 32 foot tapes and done 100 feet at a time with 60 minute epoxy in 70F. Hotter temps is bad. I also recommend you peelply the final layer to avoid drippage.

    For wetting out, avoid using small cylinders and use gallon pails. Then use a bubble bister riller and a paint roller the same width as the tape to move resins. All my wirk is done on a plastic cover, you can roll it or use the other side if the first batches start to cure.

    For more questions, feel free to ask. An easy job, but you gotta move fast.
     
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  4. JamesG123
    Joined: Mar 2015
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    Location: Columbus, GA

    JamesG123 Senior Member

    Pictures help.

    Generally mfgs. use an adhesive with a longer pot life/curing time for bonding hull sections. Plus there is usually more than one person working on it.
     
  5. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    By the way, when you wetout the stack, you roll the first piece and wet heavily or double, then lay the second part over, etc., rolling the tape over a prewetted section. Run the bubble buster hard over each layer and then roll onto a tube and any dry areas you can work prior to the tube. Poorly explained, but almost no white areas left as you stack and any misses fixed going onto the roll.
     
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  6. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    Yes, usually a 2 person job.
     
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  7. BlueBell
    Joined: May 2017
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    BlueBell Ahhhhh...

    Using the clock really assists helpers with staying on schedule, especially for mixing.
    You can delegate someone to just mixing epoxy!
     
  8. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    What I do is prep all my batches, hardener and resin and label the jugs 1R,1H, 2R, 2H, etc. and I tell the person to add the #1 jugs. And I keep a strict watch and tell them never mix without me watching. Also, when you roll tapes, chopstrand out means chopstrand down on the boat. My friend is super messy and would err, even with labels, so I order them and watch him like a hawk. So far 195 gallons of epoxy and 1 mixing error done by me.
     
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  9. bruceb
    Joined: Nov 2008
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    bruceb Senior Member

    Thanks , but I can't work with tapes- this is between a deck and hull flange, with no access once the deck is lowered into place on the hull. Think like a hobie cat or Laser is built with the deck and hull "glued" together at the flange. They fit together pretty well but there will be gaps that the bonding material has to fill, all in one step. This is on a trimaran that can hit 20Kts+ so it has to be a good joint. I am quite used to working with epoxy, but in this case I am not sure it is the best choice. I would not think the mass produced boats use epoxy for the joints, but I don't know what they do use.
    I don't have a float photo right now but I will take one next week when I am back at the boat.
    Bruce Dragonfly dock.jpg
     
  10. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    Okay, so just a join. Sounds like thickened epoxy or some open time glue. Be careful about some glues 'skinning' over. If it takes too long to cover the entire flange.

    Sounds like you are gluing a deck cap to the hull. I would still use thickened epoxy with cabosil or fumed silica as a thickener. Or if you want to remove it; something that can be heated off.

    For epoxy, never make batches bigger than 15 oz or so. I would premix your batches and cabosil amounts. You want it pretty thick; somewhere around 2.5:1 by volume. But then weigh out the batches into say gallon ziplocs. Then mix as needed onto boards and apply with trowels. Definitely a two person job. One person is making glue and the other applying. It might reduce stress to have a third person just moving the boards.

    Sorry, I assumed you were taping the seam.

    You also need to have some means to pull it all together. This is a deck shoe to hull job. Came out pretty good actually; just one spot I will need more fairing than I wish. This was done dry; so much easier. There is access inside...you might want a few locating pins for your work, if possible. The 2x4s are pretty hack, but they really helped keep the curvature right. The deck shoe was glassed on a table and returned to the boat. We just used a jig and no mould; so fitment required some wrestling. Both hulls look great.

    576B52DE-8EED-4B52-9D7F-BFF5397A5E40.jpeg
     
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  11. redreuben
    Joined: Jan 2009
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    redreuben redreuben

    I’d be looking at an adhesive like Methacrylate.
     
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