Compound curve

Discussion in 'Wooden Boat Building and Restoration' started by Gasdok, Jan 6, 2023.

  1. Gasdok
    Joined: May 2020
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    Gasdok Junior Member

    Thinking of cold molding a hull w Carolia flare. Plywood. Kerf in x and y axes for compound curve?
     
  2. Rumars
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    Rumars Senior Member

    No, spile.
     
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  3. Blueknarr
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    Blueknarr Senior Member

    Kerfs will allow a tighter radius but not a second axis.
     
  4. messabout
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    messabout Senior Member

    If the boat is to be cold molded then why would you need kerfs? If the strips are sufficiently narrow and sufficiently thin in the appropriate places, you can create the shape you want. Kerfs leave a void space in the strips. The evil rot spores will thank you for the accommodation.
     
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  5. DCockey
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    DCockey Senior Member

    If the curvature is too tight for the plywood use more layers of thinner plywood.
     
  6. Kayakmarathon
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    Kayakmarathon Senior Member

    Wood strip construction will handle compound curves better than plywood.
     
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  7. wet feet
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    wet feet Senior Member

    That may be so,but then you are compelled to go through the drudgery of glassing both sides to provide strength.I realise that people can,and have,built strip hulls without glassing but these tend to be intended for slower speeds with much less likelihood of slamming.I find fixing strips of veneer or plywood to be a much more pleasant experience.I've also found that it is really hard to get kerfing done well enough to leave an even bend and not a series of kinks,which means a lot of fairing before the next layer is applied.
     
  8. Will Gilmore
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    Will Gilmore Senior Member

    Why would that be? You should basically be laying up your own plywood right on the hull, by layering the thin wood strips. Why would you need to glass where plywood doesn't require it?
     
  9. rangebowdrie
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    rangebowdrie Senior Member

    I read that being in relation to kerfing, cutting a bunch of grooves in plywood most certainly reduces its strength.
    If done, one needs to go over the whole kerfed surface, carefully filling all the grooves with epoxy and glassing over to regain some strength.
     
  10. wet feet
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    wet feet Senior Member

    If you cold mould with strips of veneer or ply that run in an assortment of directions there is no need to glass.If,on the other hand,you just use one layer of longitudinal strips then you don't have much strength across the grain and are likely to need to glass in the manner of stripper canoes.If the strips are of substantial thickness and fastened to transverse frames then the frames provide the strength.Whichever way you choose to build there is a need for something that ties the various pieces together.It can be glass or frames but cutting kerfs will leave a break in the structure that needs reinforcement in some way.
     
  11. gonzo
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    gonzo Senior Member

    I have built Carolina boat with strip planking and with three layers of plywood. Either one works fine. Kerfs will not let you get the compound curves necessary for that type of hull.
     
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  12. Will Gilmore
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    Will Gilmore Senior Member

    I don't have much experience building actual boats, but I have worked with wood all my life, and I agree, kerfing weakens the wood unnecessarily. Thinner plywood in layers or solid wood omnidirectional strips will do the job very well. Glass would be redundant.
     
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  13. gonzo
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    gonzo Senior Member

    Glass is not redundant. It should be part of the planking schedule.
     
  14. Will Gilmore
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    Will Gilmore Senior Member

    In terms of strength. It is not needed. For other reasons, rot especially, you are right. And lots of wooden boats use no glass.
     
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  15. gonzo
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    gonzo Senior Member

    It depends on the planking schedule as designed whether it needs glass or not.
     
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