Fiberglass overlap bumps

Discussion in 'Fiberglass and Composite Boat Building' started by John Rivers, Oct 8, 2022.

  1. John Rivers
    Joined: Oct 2022
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    John Rivers Junior Member

    What is the strategy to prevent small bumps where fiberglass is overlapped on the hull?
    Are we just using fiberglass bondo, and primer surfacer and hopping there isn't a ripple.. I want a professional superclean hull with no small ripples,, that suddenly appear when I put the wet paint on. I can't get a wet look of the surface to look for a ripple,, until after I paint.. I know how the tiniest imperfections can show from body work and have done alot on cars and bikes, but I'm not using bondo and I've never fiberglassed bondoed such a large finish layer surface area. Ive always used fiberglass bondo at the base and used regular bondo over top for smooth finish.. Any tricks or tips for smooth fiberglass overlaps?

    This is also connected to an idea I am wanting to explore using carbon fiber yarn in a conforming netting structure as a reinforcement, and am wonder how to lessen the bumps that will appear. Is it just a manner of doing an extra few gel coats over the last cloth layer?
     
  2. fallguy
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    fallguy Senior Member

    Fill and fill and fill across all high spots and fill in the lows.

    If you are building in foam, you can add reliefs to reduce the height of seam tapes if the structures allow.
     
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  3. John Rivers
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    John Rivers Junior Member

    With gel and cut glass or fiberglass bondo?
     
  4. fallguy
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    fallguy Senior Member

    I am sorry, I am only familiar with epoxy work. But super thick gel coat is typically undesirable, so I'm guessing the esters also use fairing compounds.
     
  5. John Rivers
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    John Rivers Junior Member


    I'm surprised there isn't a pulp density guidelines for fiberglass bondo. There is the tiger hair, which is 1 inch or 1/2 inch strains but I don't see pulp specifications, yet they sell different types of carbon and kevlar pulp.

    I suppose I'll go your route and just use an extra amount of surfacer/primer with extra long flexible sanding pads. I want her to look immaculate and I know how every slightest deviation from the body will show with dark gloss and especially black. But I heavily desire that dark gloss look and am doing a space themed airbrush design over the black/dark blue.
     
  6. fallguy
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    fallguy Senior Member

    @ondarvr is a contributor with great knowledge of gelcoats n such

    give it a few days and see if he comments; I would be awfully worried about print through if I were you now knowing your plans until the last post...you'll need to be prepared to avoid it I'd say...my epoxy build, I got quite a bit of print through on all the surfaces that were not post cured (cooked)..boat is white and in a cool climate
     
  7. Blueknarr
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    Blueknarr Senior Member

    Bonds is usually NOT recommended for marine use.

    Are you building or repairing?
     
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  8. fallguy
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    fallguy Senior Member

    Yeah, I hope you didn't mean Bondo..
     
  9. John Rivers
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    John Rivers Junior Member

    I said multiple times I'm not using regular bondo. But fiberglass bondo.
     
  10. DogCavalry
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    DogCavalry Soy Soylent Green: I can't believe it's not people

    Polyester filling and fairing compound, from Totalboat, for example. After that the physical techniques are the same as autobody work.
     
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  11. Blueknarr
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    Blueknarr Senior Member

    Boat repair differs significantly from auto body.
    Fiber reinforced bondo has little place on boats. If you are thinking of using kitty hair DON'T.
    FG cloth of various forms is used extensively in marine repair.
    We can't give better advice without a more thorough explanation of what you are wanting to do.
     
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  12. John Rivers
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    John Rivers Junior Member


    Just want it smooth. I'll just go with the brand mentioned above.
     
  13. fallguy
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    fallguy Senior Member

    Be mindful of the problems of printing through if you want to go dark colors. I'm sorry I cannot tell you what is best visavie post curing esters, but you do need to use finer laminates at the top; covering roving with fairing compound will fail in dark colors under sun.
     
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  14. John Rivers
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    John Rivers Junior Member


    Aha. So the plot thickens....
     

  15. wet feet
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    wet feet Senior Member

    Nobody has mentioned it yet but don't allow all the overlaps to stack up in one place.Stagger the joints in the layers to reduce the height of the bumps and to disperse them.
     
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