Lock Crowther 1962 Kraken 25 trimaran build and rebuild log

Discussion in 'Multihulls' started by Corley, Jun 7, 2011.

  1. whitepointer23

    whitepointer23 Previous Member

    Thanks corley. Thats helpful to know. I have spoken to m/timbers but did not get any prices. I ended up buying recycled oregon out of An old building.
     
  2. Gary Baigent
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    Gary Baigent Senior Member

    I built this airfoil shaped single beam in 8mm paulownia strips then laid glass inside and out then carbon bands across the planks; has lasted well ... and is light.
     

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  3. cavalier mk2
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    cavalier mk2 Senior Member

    Oregon is Doug fir. I'd keep the fairing light and put a layer of kevlar on the inside. Sitka spruce is great stuff, do any of the PNW suppliers send things your way?
     
  4. Corley
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    Corley epoxy coated

    We do see some timber from the PNW here through resellers. Good quality kiln dried douglas fir seems reasonably priced for weight but Western Red Cedar is very expensive versus its price in the US.
     
  5. cavalier mk2
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    cavalier mk2 Senior Member

    Western red cedar would have to be way oversize to have the strength of fir. I wouldn't use it for beams, Grain is important in these species, the tighter the grain the better the strength. In spruce aircraft grade is the tops. It might be worthwhile to get a club buy to fill up a container of assorted wood.
     
  6. cavalier mk2
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    cavalier mk2 Senior Member

    This is one of the best ways to get good fir and other woods. It is dimensionally stable having gone through years of air drying cycles and the trees were usually better, often old growrh.

    Slow growing trees have tighter rings and more strength. Now people want fast yield so often harvest small fast grown low land trees. In the PNW one way to get occasional good deals is at the homestore of all places. Every now and then a batch of lumber will come in from a mountain cut with older trees. The same size tree as a low land one may be over twice as old due to the shorter growing season. When this happens I stash some for later.
     
  7. Marmoset
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    Marmoset Senior Member

    As a Hardwood guy I concur. Thats why despite proper moisture contents a lot of "wood" doors are going cored now. I have seen proper cured, tested, kiln dried 2 inch new growth stuff just warp like crazy, yet old stuff shaved up to new dimension holds.
     
  8. Marmoset
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    Marmoset Senior Member

    and maybe Lowes online could deliver! haha They do have the usual green c**p, but! they also do have kiln dried timber thats ok. It still needs a quick run on jointer for large sizes but! for your case you splice on down much smaller and get more mileage with smaller strips after a run through band saw and planer.
     
  9. Corley
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    Corley epoxy coated

    My Kraken 25 trimaran project got some love today. I've been scratching my head for a while on how best to reproduce the floats on the boat. These floats are custom and came out of Lock's head and don't align with dimensions of the ones in the plans. The later floats as shown in the plans were used on the more refined racing version of the boat "Jabberwock" Initially I built a hull shell using one of the floats as a plug. I've never been happy with it's shape so what I've done is use the one float that is in tolerably good shape as a plug to build a female mold. My intention is to split it down the middle using my oscillating cutter and build the float hulls in halves. Possibly vac bagging the veneers in position rather than stapling them. I've done quicky molds like this before when making custom bonnet scoops. More sanding required but gets the job done for a one off.

    My wonderful father Graeme came down and helped me do the gelcoat and wetout the CSM.
     

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  10. Corley
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    Corley epoxy coated

    Over the last week it's been more tedious work strengthening the mold with stringers. I used closed cell spacer round section foam to form the ribs then glassed over. It doesn't look like much but I've found it adds a surprising amount of stiffness to the female mold when I've done it this way in the past. I also broke up the most rotted of the two floats to make some space for laminating new float halves.
     

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  11. Corley
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    Corley epoxy coated

    Now it's cut in half thanks to Mr Fein saw. They are a bit rough but since I'm going to cold mold inside the form I'll just wax and coat the forms with PVA release. The cold mold fairs itself pretty well and since the shape is basically a curved V the veneers wont require much effort to conform to shape.
     

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  12. Marmoset
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    Marmoset Senior Member

    whats the plan, do side then other and combine, or combine mold and lay up inside recombined mold?


    Barry
     
  13. Corley
    Joined: Oct 2009
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    Corley epoxy coated

    This is what I'm thinking:

    a) I'll lay the sides up in the molds I'll probably mark out and sit the lower keelson edge against a lip to hold in position. I'll fit a slightly higher than needed gunwale strip and just staple at the very top. Should save me a lot of stapling as the veneers will be constrained inside the mold. Bottom layer laid dry and thickened epoxy between it and the second layer. Could vac bag but may not if it all sits together ok

    b) coat the inside of the finished lamination with two coats of epoxy.

    b) Glue and tab in the bulkheads on one side, glass in with double bias over the tabbing

    c) Offer the other side up and fix both sides in the deck jig

    d) tab the bulkheads in on the other side.

    e) Join the two sides along the base with double bias.

    f) Pour the keelson on the inside and cover the fillet with double bias.

    g) Then do the same for next float.
     
  14. hump101
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    hump101 Senior Member

    Much better to vac bag the veneers, not just for shape and excess resin removal, but as it draws the epoxy into the veneer increasing the veneer strength significantly, as you then have epoxy bonding the fibres together inside the veneer, not just cellulose. You can do this with either unthickened, or marginally thickened epoxy, depending on how flat your mould is.
     

  15. Corley
    Joined: Oct 2009
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    Corley epoxy coated

    Thanks, I will have to tidy up the mold edges up a bit to vacc bag but it isn't a major job. If it avoids having to pull lots of staples and gives a superior end result then a bit of extra setup time isn't a problem.
     
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