Gunnel construction?

Discussion in 'Boatbuilding' started by Bigtalljv, Apr 2, 2022.

  1. Bigtalljv
    Joined: Aug 2019
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    Location: California

    Bigtalljv Junior Member

    Hi,

    so I found another local guy who rebuilt the same hull I am working on. He raised the gunnels, like I plan to, about 12”. He made his gunnels out of solid fiberglass and poly resin, they are like 1” at the bottom!! I’m sure they are very strong and will never rot but that seems excessive to me, am I the only one?

    I was planning on going with plywood and a couple layers of heavier cloth than necessary on each side. I hadn’t planned on asking yet but what thickness should I use for that? I was thinking 1/2” ply.

    I want it to be very strong, it is a dump truck, but at some point “more” and “thicker” are just added weight, the strength returns will diminish. While bigger and thicker may be “stronger” it’s unnecessary.

    thanks
    Jason
     
  2. jehardiman
    Joined: Aug 2004
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    jehardiman Senior Member

    A foot is more than a toe rail and less than a bulwark. Are you just raising the shear forward, or all around the foredeck and cockpit?
     
  3. Bigtalljv
    Joined: Aug 2019
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    Bigtalljv Junior Member

    See, I’m wasn’t ready to think about this. I’m raising it all around. From this:
    44F95CBF-139D-4BF6-B674-EF777F4DE626.jpeg

    To something like this:
    38CC1B5C-90FE-4CF2-80B3-F71446A1F155.jpeg

    The sole gets lowered and the sides go up. Bow gets raised but the cabin stays in the same place, just gets longer.
     
  4. kapnD
    Joined: Jan 2003
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    kapnD Senior Member

    Remember that the waterline will move up, and the deck down, where will that put the scuppers?
     
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  5. Bigtalljv
    Joined: Aug 2019
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    Bigtalljv Junior Member

    Water line is below the hul shelf/chine/step, in the black on the pretty boat, the nasty white area on the project boat. The deck is usually even with or rests on that shelf.

    Here’s a scupper on the same hull with an outboard bracket.

    B605D76C-86C0-48AA-87A6-F9BE0D7B693C.jpeg
     
  6. Bigtalljv
    Joined: Aug 2019
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    Bigtalljv Junior Member

    This is probably not worth talking about right now, I hadn't thought about it, I was just reacting to that other hull and the mountain of glass and resin he used. Most of the raising is going to be “hull” rather than just an accessory so I’ll follow what construction the hull is when I cut into it or I’ll revisit it when I have actual information.

    Sorry engaged the phone before the brain.

    Jason
     
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  7. Bigtalljv
    Joined: Aug 2019
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    Location: California

    Bigtalljv Junior Member

    So I talked to somebody who knows everything about these boats and they are made with solid fiberglass. If I extend the hull up it would be just glass….

    sorry for the dumb post.

    jason
     
  8. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    It would be a massive pain to do in all glass Jason.

    Glass requires a mold.

    I recommend you make a drawing with 3 perspectives of what you have and what you want. I am leaning toward 1/2" coosa 20# for the effort. You may have to build a relief into it on the outside. Then taper grind the existing hull and glass the coosa to the hull or something like that. The nice thing about coosa is no overbores are really needed for penetrations. Otherwise with wood, everything like a railing screw or rodholder cutout/screws takes days to mount properly. The coosa also stands up on its own, within reason and you can really go fast for one off work as it takes screws so well.

    I never said it before, but probably my principal dislike of that boat is the low bulwarks.

    You could also go with corecell M80 to M200 for the sides and the coosa for the new gunwale and any coaming, but that assumes few or no penetrations..and the boat you showed has none on the starboard side we see. Only the rubrail mount which would be best in heavier tape or core..
     
  9. Bigtalljv
    Joined: Aug 2019
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    Bigtalljv Junior Member

    Yep, they said they layout melamine molds when they have done it. It’s a big job either way and it’s one of the most important to me but I have a couple other big jobs in this before I get there…..

    I agree about the low bulwarks but they were specific for commercial urchin divers who were pulling in big bags of urchins and didn’t want to hoist them up an over. Form and function, one size does not fit all.
     
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  10. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    I'd skip the melamine, glass one side of the foams, use waterproof cores. Be all roughed in in about 5 days.
     
  11. Rumars
    Joined: Mar 2013
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    Rumars Senior Member

    It's a question of money. Laminating yourself vs. store bought solid grp sheets vs. cored (again self made or bought) with different types of core. In the end you choose what is most economical for you, and "economical" also means time and labour. Everyone's equation is different.
     
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  12. gonzo
    Joined: Aug 2002
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    gonzo Senior Member

    Why heavier than necessary? Use only what you need.
     

  13. Bigtalljv
    Joined: Aug 2019
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    Bigtalljv Junior Member

    That was sort of a joke and sort of not. Being a non-professional a “little” bit more always seems like a good idea.


    That was very well said, thanks for that. “Store bought solid grip sheets”, that’s a thing?

    When you say it like that why would I do anything else? That was my first plan, and I assume there really isn’t need for a “strength” discussion. Solid GRP is heavy and may be stronger than a cored panel but the cored panel will be plenty strong for the forces applied. Does that sound right?
     
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