How to proceed after hull extension mold error

Discussion in 'Fiberglass and Composite Boat Building' started by Bigtalljv, Jan 29, 2023.

  1. Bigtalljv
    Joined: Aug 2019
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    Location: California

    Bigtalljv Senior Member

    Hi, I’m trying not to completely freak out but I pulled the forms on my hull extension today and I have a pretty bad screw up. I don’t think it’s fatal but not exactly sure what to do. One side of my mold want quite right and was about 3/4” high in the back. As usual, I’m not sure how it happened, I think I spent two months building and measuring the forms but it was wrong. Any suggestion? The other three quarters of the new section follows the hull lines pretty perfectly. This is the 30” of the starboard side.

    My plans were to next flip the hull not that I have some bulkheads in so I’ll have better access to this.

    D1C5B94E-D07B-48D8-9761-F910768EDFFC.jpeg
     
  2. wet feet
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    wet feet Senior Member

    More detail would help and maybe a view from a greater distance.Could be an easy fix-saw round the edges and use a few wedges to push it back into shape.Perhaps add struts from above and then bond back together.If its too stiff to move easily,you might have to cut part way through along a hinge line.
     
  3. Bigtalljv
    Joined: Aug 2019
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    Bigtalljv Senior Member

    Here’s a zoomed out view of the whole thing. I had a melamine mold and it was just a little high in the back….

    how about just adding some layers to the bottom to make it correct? Maybe a cored section. Not sure if having something different in one area would be an issue.
    4FE14024-5539-442A-8C38-558AAE992D8B.jpeg 43B31FE8-ADD2-4008-B728-FF33781B120E.jpeg
     
  4. fallguy
    Joined: Dec 2016
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    fallguy Senior Member

    So, you need to offer better pictures. What I am hearing is you are 3/4" high on the aft starboard corner.

    I'm not a huge fan of 3/4" of filler, but what you would do is fair it out. Whenever I have too much compound, I get nervous. Some of the professional builders are probably more comfortable with 3/4" filler. What I have done on one major area of fill is used a stack of glass.

    Is it gelcoat now or epoxy and glass?
     
  5. fallguy
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    fallguy Senior Member

    Power plan?

    Unless you are going for super speed, 3/4" of rocker might not he the end of the world..but I'd be a little nervous about bad behavior over say 20mph..
     
  6. wet feet
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    wet feet Senior Member

    Its less work to get to a good finish if you move the bottom down and bond around the edges.A template from the other side might be a good idea.
     
  7. Bigtalljv
    Joined: Aug 2019
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    Bigtalljv Senior Member

    But it’s only on the one side of the hull so I think I need to address it. It’s all epoxy and glass. How about if I added a half inch-ish of core and glass? Makes that side of the hull an inch plus but…

    it’s hard to take a useful picture by myself.
    97E72540-7CA1-4824-8D1B-46B8776FDE0F.jpeg
     
  8. wet feet
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    wet feet Senior Member

    Cut along the chine,across the transom and along the edge of the central wedge section,push down bond back together.Not difficult.
     
    gonzo, ondarvr and fallguy like this.
  9. fallguy
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    fallguy Senior Member

    I agree with @wet feet . Just cut two sides and lift it up 5/8", when upside down. Be careful to avoid going up too high and allow for some 1708 tabbing on the outside. Tab the bottom inside as well; fair it out to avoid hook.
     
  10. Bigtalljv
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    Bigtalljv Senior Member

    That sounds like a reasonable idea.

    Is it normal for me to be terrified of the idea of cutting into that? Seems like a lot more chance for me to make it worse, I don’t have a great track record right now… :)
     
  11. wet feet
    Joined: Nov 2004
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    wet feet Senior Member

    Upside down?That would be perverse for a number of reasons,as it is,gravity is on your side when laminating.No need to glass the outside if enough glass is added to the inside,where the cutting has been done.
     
  12. Bigtalljv
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    Bigtalljv Senior Member

    Thanks, I wasn’t following. So I guess I probably need to cut it off the bulkhead and stringer? This is the topside of the problem area.

    image.jpg
     
  13. fallguy
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    fallguy Senior Member

    personally, I would glass the outside with at least a single tape and it can be done either way, but the outside tape needs to be void free

    I've done plenty of glasswork and find working with the final surface up easier and the inside laminate does not need to be as perfect, but you could also do the rough work as is and flip it for the finer work. That way all the taping is down..
     
  14. fallguy
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    fallguy Senior Member

    Is is high at the stringer? Or is the stringer high then as well?

    I figured the corner was high; so only need to cut the corner?
     

  15. Bigtalljv
    Joined: Aug 2019
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    Bigtalljv Senior Member

    It’s a little high under the stringer but not as much. The alignment of the extension is perfect at the keel and as you move up the hull towards the outside the error gets worse and then it get lots better at the chine….

    The stringers lined up and were level across the top. The bulkhead I did notice was asymmetrical so I knew something was wrong but hadn’t figured it out yet.
     
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