Building a racing canoe

Discussion in 'Fiberglass and Composite Boat Building' started by Yukon, Jun 15, 2019.

  1. Yukon
    Joined: Mar 2019
    Posts: 3
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    Location: Belgium

    Yukon New Member

    I'm Francis from Belgium, and after building 2 strippers in WRC it's time to start with a new project, a racing C1 in composite. The idea is to make the hull with strips Corecell (7 mm thick) and then laminating with carbon fiber. Because I have no experience with carbon, the question is: can I use 4 oz Twill weave in a hand lay-up or is it better to work with 6 oz. I've heard that 4 oz difficult to work with... Is it an idea to wet out the carbon on a plastic sheet with epoxy and then lay it on the hull? Because I can't buy carbon who is wide enough to cover the hull in 1 time I have to make a seam. Or I lay the fabric lenghtwise over the hull and make the seam at the keelline or I lay it from gunwale to gunwale, but then I have more seams, so how can I make them less visible? I want to build the boat as light as possible, so I think using peelply after the wet-out is maybe a good idea? I don't know if it's possible to use also the vacuum technique on a male mold so I have the best ratio carbon/epoxy. All tips are very welcome to build my first composite foam core C1.
    Attached you can find the type of hull that I want to build.
     

    Attached Files:

  2. DCockey
    Joined: Oct 2009
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    Location: Midcoast Maine

    DCockey Senior Member

  3. rwatson
    Joined: Aug 2007
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    Location: Tasmania,Australia

    rwatson Senior Member

    "using peelply after the wet-out is maybe a good idea?"
    Yes, that is good but not as good as
    "vacuum technique on a male mold "

    As carbon fiber is hard to sand, and you might like to keep the carbon "stripes" as a decorative feature, there is a big case for building a female mold, and laying the foam on top under vacuum once the first Carbon layer has been laid and cured..
    If you can avoid as much paint as possible, it will save weight.

    From experience, using 4mm Corecell produces a very tough shell with layers on either side. I wonder if you could save much weight using the 7mm core as "ribs", and the 4mm as "skin".
     
  4. Yukon
    Joined: Mar 2019
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    Location: Belgium

    Yukon New Member

    And what do you recommend about the weight of the carbon? If I see and read the articles about foam strip building, the most works with a female mold, but the boats are also bigger. I hope the technique works also with a male mold and maybe I can Thermoform the Corecell over the forms on some place. The forms are 1ft separated from each other, but I have no idea if I need smaller battens between them, especially if I want to try the vacuum technique.
     
  5. Steve Clark
    Joined: Jul 2004
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    Location: Narragansett Bay RI

    Steve Clark Charged Particle

    The most usual carbon cloth is about 200 g/ m^2.
    This is woven from 3k carbon yarn and is the most affordable carbon.
    There are fabrics woven of 1k yarn, but they aren’t 1/3 the weight, more like 160g/m^2
    The lightest woven materials are “spread tow” and consist of an almost basket like weave of carbon yarns that have been turned into tapes before weaving. This stuff is harder to laminate because it will not stretch on the bias as nicely as conventional cloth, so you will have to use more smaller pieces, and probably use conventional cloth for stems and places where drapability matters.
    If you have glassed strippers, your laminating technique will be fairly comparable.
    Carbon does not become translucent like glass, so it is hard to tell if you have completely wet the area and removed all the air. This is perhaps the biggest benefit of squeegeeing pell ply into the laminate. You can see the dry areas and can tell when it is fully degassed by the color change of the peel ply.
    Foam will absorb more resin than you think, you have to account for the resin that bonds the laminate to the core. I use 150 g/m^2 as a budgetary number when calculating weight.
    SHC
     
    rwatson likes this.
  6. Yukon
    Joined: Mar 2019
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    Location: Belgium

    Yukon New Member

    Thanks already for all the input. I know, that the top layer of Corecell is a little bit porous, so I thought to give it first a primer layer (epoxy with microballoons) and when the epoxy is still tacky, lay the carbon.
    Maybe it's also good idea to do first a test with the 2 different weights (160 gr vs 200 gr) and see how it handle. I found on the internet a good technique:

    • Begin by laying down a heavy sheet of plastic film, such as Visgueen or our Nylon Vacuum Bagging Film. The thicker the film the better.
    • Layup the fabric reinforcement on top of the plastic film and pour resin over material.
      • Be sure to use a resin that has a longer working time. By using a lower viscosity resin, the resin with flow through the fabric easily.
    • Squeeze out excess resin.
    • Place another layer of the plastic film on top of the fabric.
    • Using a drum roller or a rolling pin, apply pressure forcing resin into the fibers while pushing any remaining excess resin.
    • Keep the plastic film on to cut out templates.
    • Remove top layer of plastic film and apply the fabric to mold surface.
    • Once in place, remove the other plastic film layer.
    • Handle as you would a commercial prepreg from this point onward with respect to vacuum bagging

      Is it necessary after the vacuum bagging to give the carbon on the outside a second coat of epoxy to fill the weave, or can I directly apply the UV varnish?
      When I want to do the vacuum technique on a male mold, do you think that the Corecell (7 mm) gonna be deform between the forms? The forms on the strongback are installed every 1ft from each other.
     
  7. rwatson
    Joined: Aug 2007
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    Location: Tasmania,Australia

    rwatson Senior Member

    "do you think that the Corecell (7 mm) gonna be deform between the forms? "
    Absolutely. You have got some hard curves there. 7 mm is very thick for tight places.
     
  8. BlueBell
    Joined: May 2017
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    Location: Victoria BC Canada

    BlueBell Ahhhhh...

    It's okay, it's all carbon fiber, what can go wrong?
     

  9. Blueknarr
    Joined: Aug 2017
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    Location: Colorado

    Blueknarr Senior Member

    Yucon

    I have seen foam on male plugs done several ways. Most newbies think they can lay foam and glass then bag the whole thing. The plug always collapses under vacuum pressure. To prevent this the plug should be isolated from the vacuum.

    How I have successfully vacuum banged over partial plugs:
    Double stick foam tape on edges of stations don't exposed top adhesive.
    Shrink wrap
    Staple foam strips
    Fair foam
    Seal foam
    Lay down fiberglass
    Vacuum bag sealing to shrink film.
    Fair and finish.

    The double stick foam tape will seal around the staples

    Good luck
     
    rwatson likes this.
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