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Thread: cedar strip build as a plug?

  1. #1

    Default cedar strip build as a plug?

    I am considering making a couple of canoes and wondered if anyone could offer advice.

    Firstly will a cedar strip canoe end up lighter Than a normal plastic construction?

    I would like to build a cedar strip as a nice project and then a second composite one.

    I'm wondering if I can build the cedar strip and then use it as a plug to layup the composite one on?

    Perhaps it more sensible to go the whole hog and build a female mold for the compsite?

    I'm just trying to get a feel for the most sensible and efficient way to go about it?

    I make surfboards so have a bit of composites experience and I also have vacuum bagging equipment if that changes the thinking on the plug or mold decision.

    Any advice welcome.

    Oh and I don't plan on making more than one or maybe two composite boats.

  2. #2

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    [QUOTE=r896neo;645578]I am considering making a couple of canoes and wondered if anyone could offer advice.

    Firstly will a cedar strip canoe end up lighter Than a normal plastic construction?
    Depends on how you build the cedar strip canoe and what you mean with "plastic", as Kevlar, Carbon, Polyester, Vinylester, Epoxy et cetera are plastics too. If you mean plastics like Polyethylene and Royalex/T-Formex, than yes you can build a lighter canoe with cedar strip -- if you do it well...

    I'm wondering if I can build the cedar strip and then use it as a plug to layup the composite one on?
    Yes, but

    Perhaps it more sensible to go the whole hog and build a female mold for the compsite?
    Probably, because this is the usual way AFAIK.

    Dirk Barends

  3. #3
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    A stripper can be used as a plug, yes. Although purpose made plugs will often be of heavier construction than anything intended for paddling so as to maintain the shape properly.
    you can then take a hull straight off the plug but you will end up with the nice surface on the inside. The outside will be as good as you can get it with finishing cloth, sanding, filling etc.
    as aid, it's normal to make a mould from the plug and take hulls from that. It just depends in how much work you want to do.
    this book's quite good on the subject: https://www.amazon.co.uk/Canoe-Kayak...Canoe+building

  4. #4

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    Rather depends on the shape - any recurve on the ends and it'll never come off the plug. Tumblehome similar.

  5. #5

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    Quote Originally Posted by Willpower View Post
    Rather depends on the shape - any recurve on the ends and it'll never come off the plug. Tumblehome similar.
    you need a 2 part mold for shapes with tumlbehome or recurved ends.
    Propper writing in English. How do you do that? with dyslexia, bad hand eye coordination, ect. and in a foreign language.
    Sorry for all the mistakes.

  6. #6

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    And that would rather spoil the Cedarstrip canoe used as a plug!

  7. #7

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    Quote Originally Posted by Willpower View Post
    And that would rather spoil the Cedarstrip canoe used as a plug!
    nope the boat can be 1 part no problem , the new build mold needs to ba a 2 part afair. like here on the right
    Propper writing in English. How do you do that? with dyslexia, bad hand eye coordination, ect. and in a foreign language.
    Sorry for all the mistakes.

  8. #8

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    Yes that's true but I read the OP as suggesting laying up directly on the Cedarstrip.

  9. #9

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    Thanks for the replies, seems like its not going to work well. Any ideas on the most efficient way to get a second composite canoe from a cedar strip hull? Both will likely be prospectors but I'm not fixed on that. Would a prospector type require a 2 part mold?

  10. #10
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    Quote Originally Posted by r896neo View Post
    Thanks for the replies, seems like its not going to work well. Any ideas on the most efficient way to get a second composite canoe from a cedar strip hull? Both will likely be prospectors but I'm not fixed on that. Would a prospector type require a 2 part mold?
    It depends on the shape of the hull. You have to imagine pulling the new hull,out of the mould. As long as the open side of the mould is wider than the inside then the hull will pull out. If thenhull curves inwards anywhere as you go towards the gunwales then you'll need a two part mould. You can't pull a wider but of hull through the narrower gap.

    even if you have a one part mould (and I have) you might still struggle. Polyester resin will shrink slightly whilst curing and sompull itself away from the mould. An epoxy resin will kit shrink (not enough to matter) and so be much harder to rlease from the mould. One way around this is to include a small hole in th bottom of the mould through which you can pump compressed air, or water, to force the hull away from the mould.

  11. #11

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    Cheers, I suppose perhaps then that will factor into which design i go for. Thanks for your thoughts. Any other opinions or advice welcome.

  12. #12
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    Quote Originally Posted by r896neo View Post
    Cheers, I suppose perhaps then that will factor into which design i go for. Thanks for your thoughts. Any other opinions or advice welcome.
    I pulled multiple hulls with tumblehome from a mould that only a split for a couple of feet of each end.The hulls would not come out easily.Rather than using compressed air as Rob suggested I used water,I put a couple of wedges between the mould and the hull until I had a big enough gap to pour water in and literally 'floated' them out.

  13. #13

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    Thanks, been looking at some Kevlar ones where the stem is left open and then closed after demolding. Seems like a possibility.

    Just got the easy task of deciding on which cedar strip to build now. That's going to be easy.....

  14. #14
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    If you want tumblehome or recurved ends and do not want to make a two-part mold you might be to make a mold from just the hull part and build the "deck" (tumblehome and/or recurved ends) on top of that. For instance a strip of plywood (finished with glass and expoy) will make an easy tumblehome if you attach it stitch and glue style.

  15. #15
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    I have never done it, but went a long way down the examination route before abandoning the idea... A split mold that pulls apart forewards and backwards just need a mid point "fence" built round your plug, so that the first half mould includes the upstand to form the joint. when its gone off, remove the temp "fence", trim the upstand to the right dimensions, lay up second half to include another up stand (wax the upstand so that it will separate). When it has all gone off, drill for fixing bolts, pull mould off each end. bolt up, lay up another hull inside. If you look at as many photos as you can find on Millbrook Boats, some show how this works for him, and he has some seriously "deformed" hull shapes that work with a two piece mould.

    Impcanoe

  16. #16

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    Don't give up on your idea.
    A heavily tumble-homed boat can still be formed over a male plug (your cedar-strip hull) if you accept that you will have to split the ends, and finish the stems off the mold. And, if when planning your boat you plan for floatation tanks fore and aft you have the opportunity to engineer the structural loads from the outset, and hide the difficult to finish inner glass/epoxy work at the stems.
    Good luck with it!
    Trevor Paetkau
    Ashes Still Water Boats
    Canoe Plans | Custom Boats

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