Restoring 20' fiberglass boat - Challenge needs solution

Discussion in 'Boat Design' started by MBMarine, Feb 25, 2009.

  1. MBMarine
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    MBMarine Junior Member

    Hello

    I'm in the process of restoring an old 20' fiberglass boat. Allthough I guess restoring would imply that I am bringing it back to it's original look and condition and that's not quite true. I am removing the small cabin and making an open boat out of it. The boat looks like this http://www.yachtcare.se/myra.htm and is becoming more like this
    Myra20.├ąpen.jpg

    To get to the point here I am trying to create one uniform profile around the inner edge of the deck to avoid getting the "a part of my boat is missing"-look. And to do so I would like to recreate this profile all around the inner edge. (see picture) Unfortunately only the stern has this now.
    akterdekk3.JPG

    How can I achieve this? what choice of material and method could work to end up with a decent result? If the profile can't be recreated I am open to other suggestions.

    Thank you!
     
  2. Maineac
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    Maineac Junior Member

    Like a bulwark on the gunwales that runs fore and aft both sides? Your question isn't clear.
     
  3. MBMarine
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    MBMarine Junior Member

    Right. Sorry for the unclear question. Only the horisontal surfaces of the decks are left and a new bulwark needs to be constructed.
     
  4. Maineac
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    Maineac Junior Member

    Fiberglass. I'd probably find a hard plastic or pvc pipe or hose size the right radius (smaller, because you're going to allow for layers of glass on it) in comparison to the existing spray rail/bulwark. Figure out the curve of the gunwale area end to end, mark it on a bench and make both sides off the boat with 1/2 oz chop/biax/chop/chop. Make them a little long so you can cut/grind them to fit, glass them to the existing, grind, fillet, fair & paint. Thing is, will they sit on existing deck or is further modification necessary?
     
  5. MBMarine
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    MBMarine Junior Member

    Good idea. I would probably have to make an arrangement to make it sit on the existing deck, but I will figure something out. Thank you very much. This has been bugging me for days now.
     
  6. PAR
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    PAR Yacht Designer/Builder

    I've done exactly what you're about to try.

    Build a flange out of fabric. The way I did it and found the easiest was to temporarily screw a fitted piece of wood under the deck, with it's inboard face at the angle I wanted. I covered this with clear packaging tape, then laid up fabric over this, bonding it to the deck, which was feathered back to receive the additional bulk of the new fabric.

    This makes a tabbed in flange, once the wood is unscrewed and removed. Fill the holes and attach a wooden coming or make a 'glass one to suit. I use a brightly finished piece of mahogany, but you can laminate anything you want to the flange. You can bond it, so it's a continuous, seamless coming, or fasten a bedded coming, which is what I did, in case I needed to remove it for repairs, refinishing, rebedding, etc.

    Not much will stick well to PVC, so I'd be hesitant about using it. PVC also gets quite brittle and will depolymerize with prolonged UV exposure, not to mention it's not very strong.

    I'd use epoxy, just to insure a really good bond and to skip the need for mat, but polyester will work, though you'll need to bulk it up.
     
  7. Maineac
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    Maineac Junior Member

    The pvc is only to hold the shape while the West System kicks. It should be covered in wax paper or mold release so it's removable, but like you said, not much sticks to it, but epoxy will when you don't want it to. With the epoxy, you're just making a substantial hollow bulwark. I could go into detail about benching, but a piece of pvc longer than you'll need, bent to shape and held in place by a few nails, blocked up at the height you want, less room for layers of cloth on top to come to the correct height, work around the nails on the first couple of layups, then move the nails, fill the spaces where the nails'd been, etc. The bench should be covered in wax paper taped or stapled down as well. Once the first couple of layers have kicked, lose the pvc and start fitting and trimming on the deck where you want it. Final layups will tie it to the deck and the existing stuff. Grind, fill, fillet, sand, deblush and paint. Read the West System manual carefully FIRST. I'm just doing stream of consciousness stuff here, but that's usually how I work. Sit, stare at it for 1/2 hour, get to work. I like the idea of maybe doing it in wood, too.
     
  8. MBMarine
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    MBMarine Junior Member

    Thanks for the good advice. I will be able to work something out form the ideas you have provided. One more question though. Why do it off the boat? Wouldn't it be better to create the curves accurately while the pvc (or other support material) is termporarily attached and laid up correctly with mold release on the deck. Then after the epoxy has hardened, remove the piece and the pvc and re-fit the rail by applying fabric both over and under to attach it to the existing.
     
  9. Maineac
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    Maineac Junior Member

    Either way, I suppose. I was just ruminating on trimming and creating the flange radius at the base of the piece, then fitting it to the boat and tying everything together.

    Using teak sounds pretty nice, too.
     
  10. PAR
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    PAR Yacht Designer/Builder

    Yep, on the boat would insure everything fits precisely.

    Again, if it was me, I'd grind back the contact areas on the existing decking. Feathering it back to get a good tabbing into the old work, then install some sort of mold, directly on the boat.

    I find it easier to bend wood reliably then PVC. I've bent enough PVC pipe over the years to know it's often hard to get curves just right, especially if you have to toss heat at it. Wood will usually bend to a uniform curve. If it's thin enough you can tie knots in it. PVC will bend to a uniform curve if you don't heat it, but it does have a limit to which it will bend without kinking, buckling or requiring heat. So I guess it depends on how tight the smallest radius is, as to which will make the best mold.

    I'd also do everything in one shot, rather then molding, then bonding. I'd bond and mold at the same time.

    It depends on what you desire. Do you want a "cast" coming, like it came out of a mold or do you want a distinct separation, possibly from another material (wood, HDPE, etc.). If the molded look is desired, design a mold to suit your shapes. If you're looking for a separate coming, then all you need is a flange to attach to. Of course the flange should be molded to accept any angles, curves, etc. you might need.

    A flange is easier from a finishing stand point, as it can be done fairly rough with the coming, caulk and trim pieces covering much of it. An all molded in coming requires the finish work, preformed directly on the boat and the mold needs to be more precise, to save yourself fairing work.

    Most times an picture describes better then words . . .
     

    Attached Files:

  11. Maineac
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    Maineac Junior Member

    That would do it nicely!
     
  12. PortTacker
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    PortTacker Junior Member

    I would do similar to Par's idea (but it doesn't have to be anywhere near that complicated) with foam. Simple foam sheets from Home Despot (the extruded stuff ("blue foam" or "pink foam" not the white "pressed bead" stuff) cut into strips and put it place. Shape to suit, glass the whole mess.
     
  13. Maineac
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    Maineac Junior Member

    But having that vertical piece of wood as a foundation would make for a much more substantial coaming/bulwark. And prottacking the start is the cat's *** when they ain't expecting it and it works!
     
  14. MBMarine
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    MBMarine Junior Member

    That drawing did it. Thanks.
     

  15. PAR
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    PAR Yacht Designer/Builder

    You'll note the wooden blocks that create the foundation of the coming in my drawing above are intended to be removed after everything is cured. They could remain in place, but aren't really necessary if the new laminate is thick enough. If you did leave them in place, you could get by with much less laminate thickness, which to some, may be a reward.

    If you elect to use foam, it has to be fully enclosed (cored laminate) or the new laminate has to be relatively thick, because the foam is only a mold in this case and not helping the strength department (unlike wood). Be very careful of the stuff you by from the big box stores. All of these foams will absorb water over time, which generally isn't a good thing, within laminates, but is just fine if the foam is a temporary mold.
     
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