Questions about epoxy

Discussion in 'Fiberglass and Composite Boat Building' started by schlever, Jul 21, 2009.

  1. schlever
    Joined: Jul 2009
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    schlever Junior Member

    Hi,

    I am restoring my 8 foot fiberglass pram. Not trying to make it a show boat, just something that is safe and gets me to some backwoods fishing spots.

    I just have a few questions regarding materials. I have some small holes that are not right through, but rather the outer hull has chipped away in a few places. They are about the side of a eraser on the end of a pencil.

    I went and bought a 3M Bondo marine fiberglass resin and hardener kit, which includes fiberglass cloth as well. My questions are as follows:

    1. for neat expoxy, I just don't use the hardner, just the resin. I am making a motor mount as well
    2. can I use this for mounting the motor mount to the boat with the hardner, or should I use something else?
    3. can I use the resin/hardner combination to fill the holes above in the hull without using fiberglass mat? The product said I must, but given the size I'm not sure I can without making the holes much larger.

    Thanks,
    Kevin
     
  2. KnottyBuoyz
    Joined: Jul 2006
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    KnottyBuoyz Provocateur & Raconteur

    Hi Kevin

    That's some loaded questions you got there. Have you read the instructions?

    No you'll need to follow the instructions on properly mixing the resin and hardener. The resin will never harden without the hardener, sorry it's a sad fact of life. If you're just touching up some dings in the fiberglass you can use the resin & hardener without the fiberglass.

    Motor mounts are subjected to a lot of stress that's why they're reinforced with strong cores and multiple layers of fiberglass. If you do a search on "Transom Repair" you'll find plenty of answers.

    Normally if these holes are below the water line you'll want to open them up to allow you to lay in multiple layers of fiberglass in ever larger sizes. Here's a video on youtube that can explain it better than me.

    http://www.youtube.com/watch?v=6N7YMr6E564&feature=related

    Small holes that won't affect the watertight integrity of the hull can be filled with the fiberglass & epoxy you have. Cut up some of the fiberglass into short strands (kitty hair) and mix it in with the epoxy. This will add some strength to the repair. Just sand off and paint after.

    Good luck with your project.
     
  3. schlever
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    schlever Junior Member

    Thanks Rick. The holes in question are not right through, so I will fill them with the fiberglass and epoxy. As for the transom, I had a previous post on here that PAR said I could use a 9x12 inch board, covered with neat epoxy, then epoxied to to the transom as a mount. It will only hold a 3 hp engine. Do you think this will suffice?
     
  4. schlever
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    schlever Junior Member

  5. KnottyBuoyz
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    KnottyBuoyz Provocateur & Raconteur

    PAR knows more about the engineering than I do. I would defer to his advice. It's well given.
     
  6. PAR
    Joined: Nov 2003
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    PAR Yacht Designer/Builder

    The product you have - 3M Bondo marine fiberglass resin and hardener kit - is NOT epoxy. This is polyester resin and catalyst (hardener). It will work, but not for very long on the engine support.

    It's rather important to read the instructions on the products you're using. Neither polyester, nor epoxy resin can cure without the hardener added and it's assumed that it is added in ALL cases.

    Nest epoxy means nothing is added to the mixed resin to thicken it or make a glue. Neat epoxy is used as a moisture proof coating. You'll need three coats for good protection.

    You can glue the plywood reinforcement to the transom with epoxy (thickened) or you can bed it with goo in a tube (3M 5200 or similar) which will be easier, but will require hard fasteners (bolts) to insure it doesn't fall off.

    The plywood suggested is more then sufficient to handle the power of your little outboard, especially if it's bonded to the transom with thickened epoxy.

    Log onto www.Westsystem.com and www.systemthree.com and have a look at their user's guides. It will explain the different products, fillers, sealing wood, gluing things, etc.
     
  7. schlever
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    schlever Junior Member

    Thanks guys ..... much to learn!

    Do you think I should return the kit I bought, or will it suffice to fill the small holes in the hull?
     
  8. KnottyBuoyz
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    KnottyBuoyz Provocateur & Raconteur

    Epoxy is better than polyester resins. Take it back if you can. If you just need a little fiberglass PM me your address and I'll send you enough for your repair.
     
  9. schlever
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    schlever Junior Member

    Thanks Rick. Bought the stuff from Walmart, so easily returnable. Going to call around to find some marine epoxy and will keep you posted on how things turn out!
     
  10. KnottyBuoyz
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    KnottyBuoyz Provocateur & Raconteur

    Small batches in marine stores (chandlers) will be very expensive. If you're not in a hurry I have an e-Bay supplier who's reasonable. If you're close to a border you can send it to a UPS store and nip over to pick it up.
     
  11. schlever
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    schlever Junior Member

    Was going to try PC-11 Marine epoxy. I can get it from Home Hardware for $20 for a 1/2 Litre.

    http://www.pcepoxy.com/pastepoxies/pastepc11.asp

    I've read on some other sites that people have used it to repair hull damage and its very similar to Marine-Tex, so I'm going to give it a try. I need to have the boat ready for next weekend, as I'm heading out the the lake in Ontario and am going to be leaving it there for the rest of the summer.
     
  12. alan white
    Joined: Mar 2007
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    alan white Senior Member

    I don't know if a small boat like that with little chips here and there needs to have anything more than a that marine repair kit since the boat is also polyester and if the gouges are abraded, the stuff ought to stick fine.
    Not so for the motor mount! You could make the motor mount out of plywood, paint it both sides, and forget the adhesive--- bolt it through the transom. Remember to seal the holes before running bolts through. A tube of polyurethane sealant (marine grade) could be applied to the surfaces being bolted together and the bolt holes as well.
    The last thing you want to do is start ordering things from someplace far away when you need the boat for next weekend.
     
  13. bigdawg10132009
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    bigdawg10132009 Junior Member

    hey knotty.....can you get me that contact for the epoxy? i am starting a redo on an ebbtide i bought....thanks
     
  14. mitch55
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    mitch55 New Member

    Isophthalic Polyester Resin

    I know that epoxy resin is better than polyester resin, but I read about isophthalic polyester resin, (which is less than half the price of epoxy resin), how does it compare to epoxy resin? How would it be to build a boat with?
     

  15. mitch55
    Joined: Aug 2009
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    mitch55 New Member

    I know that epoxy resin is better than polyester resin, but I read about isophthalic polyester resin, (which is less than half the price of epoxy resin), how does it compare to epoxy resin? How would it be to build a boat with? I am new at this so any help is greatly appreciated.
     
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