Epoxy vs Polyester Resin

Discussion in 'Boating' started by catsmith1, Apr 26, 2007.

  1. catsmith1

    catsmith1 New Member

    Messages:
    1,073
    State:
    Haughton, Louisiana
    Ok, I can get "polyester resin" locally for under 30 dollars a gallon with hardner from a fiberglass supply place. First, what is it and Second will it work as well as Epoxy for building a pirogue or other boat? I read online where it is used for boat building.
     
  2. turtle1173

    turtle1173 Member

    Messages:
    613
    State:
    Mayfield, KY
    If you are serious about doing it "right", definitely go with Epoxy. I can't give you any technical info but the Polyester Resin will not last very well on the wood. Mark J talks about this frequently & rightly so. I went the cheap route when I re-did my floor a year and a half again. Just after a few months, the seams starting separating.
     

  3. Mark J

    Mark J New Member

    Messages:
    9,407
    State:
    Four Oaks, NC
    I can assure you with complete confidence that any way to save money has been tried by boat builders. The most common is with polyester or vinylester resins. They are not nearly as waterproof as epoxy and it does not laminate to wood very well at all.
    Polyester resins are used in fiberglass boat building. This is why youy see so many rotted floors in fiberglass boats.
    To cut corners manufacturers will coat the wood floor with what they have on hand which is polyester resin.
    The same floor properly installed with epoxy would outlast not only the boat, but you as well.

    I highly recomend several issues of Wooden Boat magazine. You'll quickly find similarities in products used by the professionals in their trade that build and refit for profit.

    A couple of years ago I did some electrical work for an older man and in the process I went in his garage where sat a good sized sailboat he was building.
    He was all the way to the paint stage but told me the project had stalled 5 years earlier and he just didnt have the motivation to finish this sleep aboard.

    I didnt persue it but I knew exactly where his motivation went. He went for the 30 dollar polyester and before he could get the hull faired he had delaminations 6 inches wide and 4 feet long.
    He'll never finish it. To finish it now would be harder then starting all over.
    The majority of boats built at home are never completed and this is one of the reasons why. Cutting corners backs them into a corner they aren't willing to correct or they cant get past the frustration of it.

    Using the right materials for the right job will make your project flow like water.
    Just like clock work until you splash it for the first time.
     
  4. TDawgNOk

    TDawgNOk Gathering Monitor (Instigator)

    Messages:
    3,365
    State:
    Tulsa, Oklahoma
    Mark,

    I know you have done so many times, but can you suggest a good epoxy to use? For example, if someone was going to replace a wooden transom in an aluminum boat. Also, is there an acceptable replacement for marine plywood if someone is unable to locate a local source for marine plywood?
     
  5. Mark J

    Mark J New Member

    Messages:
    9,407
    State:
    Four Oaks, NC
    I recomend any 2-1 epoxy over the more expensive 5-1.
    With epoxy if you screw the mix up you just cant throw more hardner to it. You'll have to get all that goop off and start over with the lamination. Its not Bondo.
    There is too much room for error in 5-1 especially when you get in a hurry in a big lamination.

    Systems 3 is good epoxy as is the cheaper Marine Epoxy brand. In many ways I like the marine Epoxy better. Systems 3 offers a complete line of epoxy products though that surpasses most anyone else and they have their own paint too. their paint works on their epoxy, so there is no wondering the outcome while you brush or spray away.

    For something like your project exterior plywood be fine.
    Building a planing hull I wouldnt recomend it.
    Inside of a planing hull for something like gunnels or a console exterior is fine.

    Marine plywood excels in strength above that of exterior plywood.
    Its void free.
    It has more plies and is lighter.
    And its easily machined and faired.
    Marine plywood like Meranti or Gaboon dont check. Therefore you wouldnt have to glass the entire boat inside and out on some boats. Less weight and alot less money.

    If you built a boat out of exterior plywood you would spend more money getting it faired out then what marine plywood would have cost up front, have a heavier boat, and have voids that will collect water vapor over time and take away from strength as its built.

    Its referred to as a false economy in boat building.

    For a canoe or knock around pond boat exterior is fine as long as you arent trying to build light. If you are after the 15 or 20 pound kayak you'll have to open the wallet a little wider but if you can deal with 45 pounds you'll be economy class and sluggish especially when you try to get her to look good.
     
  6. catsmith1

    catsmith1 New Member

    Messages:
    1,073
    State:
    Haughton, Louisiana
    I thought it might be too good to be true for something that cheap.:cool2:

    I looked at HD yesterday for some Luan for a test run on a pirogue. I want to try my hand at this boat building stuff before I bite off something bigger. The luan was full of knots. I am going to keep looking for two good pieces. There is no1/4 marine within 150 miles of me. I would have to go all the way to South Louisiana. Maybe for the next progect but not for a pirogue.
     
  7. last chance

    last chance New Member

    Messages:
    56
    State:
    Louisiana
    catsmith1, have you tried Hart Lumber Co. on midway st. in Shreveport?
    I've bought 3/4'' and 5/8'' marine plywood there and they probaly have 1/4'' and 3/8'' aswell. There should be plenty of good 1/4'' cabinet grade plywood around shreveport that would work very well if you use the right epoxy that Mark sugested. Hope this helps.