1994 Parker 2320 new roof

Discussion in 'Boat Design' started by Mark Heltunen, Feb 5, 2018.

  1. Mark Heltunen
    Joined: Feb 2018
    Posts: 3
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    Location: Michigan

    Mark Heltunen New Member

    Hello everyone and thanks for adding me your forum. I recently purchased a classic Parker power boat with a rotted roof. I’m undergoing the process of repairing it. Currently I have the outer skin of fiberglass removed exposing the core material. I have removed the old/rotten balsam core material and soon I am going to replace the removed core with either marine plywood or balsam. The size of the repair is approximately 60 ft sq . The removed skin was about an 1/8” thick. I am looking for some suggestions on what kind of fiberglass cloth would be best for this repair. Should I do multiple layers? If so how many would be adequate? Any help is greatly appreciated.

    Thank you
    Mark Heltunen
     

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

    PAR Yacht Designer/Builder

    Welcome to the forum.

    Plywood replacing balsa would have a significant weight impact on the boat and this high up in the structure, so not a good idea. There are other core materials that are much less likely to absorb moisture (like foam) you might consider, though costs usually come to play. I used a 5 pound density foam and skin it with a few layers of 12 ounce biax, before a finish cloth (6 ounce or lighter). Use plywood or Coosa board in the contact patches or where things are attached, such as lights, masts, fittings, etc..
     
  3. Mark Heltunen
    Joined: Feb 2018
    Posts: 3
    Likes: 0, Points: 1
    Location: Michigan

    Mark Heltunen New Member

    Thanks for the feedback. Due to the size of the repair I calculated the additional weight to be about 22 #’s heavier than balsa. In my mind this is a negligible weight gain. On my original post the total repair is listed at 60 sq ft, but the core area being replaced is about 30 sq ft. Once the core is replaced I will glass over and re gelcoat. Considering some owners install a second station tower (small one) on this model I’m thinking effects of the additional weight won’t be noticed.
     
  4. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 490, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    I was working with 60 sq. ft. (nearly 3 full sheets of plywood) from your origional post, which if 1/2" (12 mm) would be well over 120 pounds, depending on species and sheathings. 22 pounds isn't enough to get excited about.
     
  5. Mark Heltunen
    Joined: Feb 2018
    Posts: 3
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    Location: Michigan

    Mark Heltunen New Member

    Agreed. My initial post was a bit unclear on the specifics on how much re coring I was doing
     

  6. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 490, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Use as little laminate as practical, as this will weigh a lot, particularly over plywood. The laminate only needs to offer weather proofing and abrasion resistance, which means a light sheathing is all you need. I'd recommend epoxy, as it stick far better to plywood (and everything else) better then polyester and you can still gel coat over it if you want to. Some say you can, but my and industry testing in recent years has proven this incorrect. I can get slightly better bonds with sprayed gel coat over a hand laminate (compaired to polyester) and much better (okay, about 5 - 7% so) over bagged laminates. I don't do this all that often, as it's cheaper and easier to just paint it, unless I'm going for a deadnuts (technical term) color match and/or need a tougher surface in a high traffic area (soles and fore decks usually).
     
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