Buccaneer 24 Builders Forum

Discussion in 'Multihulls' started by oldsailor7, Jul 22, 2009.

  1. oldsailor7
    Joined: May 2008
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    oldsailor7 Senior Member

    Yes Bruce. I built my Piver Nugget using bronze ringnails. Worked well.

    Those were fun times we had on Lake Ontario. :D
     
  2. Gary Baigent
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    Gary Baigent Senior Member

    30 odd years ago when we built the first Tennant Bamboo Bomber, Malcolm suggested, instead of using double thickness ply, then stainless plates with drilled holes for bolts for the chainplates, that I try gluing a rigging thimble to the gunwhale where the shrouds connected, then use uni directional glass (couldn't get carbon in those days) wrapped over the thimbles and then carried down the hull sides and purposely placed ring frames, spreading the loads over a very large area ... so that is what I did ... and have done the same thing ever since, but switching to uni directional carbon after the first glass layer instead. Never had any problems on numbers of boats built or altered. The result is cleaner, simpler, neater, and much stronger.
     
  3. catsketcher
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    catsketcher Senior Member

    Move with the times

    You know I love your work Pat but I think times have moved on since you last built a Bucc. I certainly would get every fastener out of any boat I was building. If you think of the shear loads involved in splitting the stringer off the epoxy then you are talking massive loads and you may even get an earlier failure where the nail acts as a stress concentration. This may lower the ultimate load the stringer can take. These boats could have been built with resorcinal glue which is not as strong as epoxy unless the clamping pressures are greater - hence the nails. I would use tek screws to screw the stringers on and then when the glue sets get them ALL out.

    I would also back up Gary with the chainplates. Anyone who puts stainless chainplates in a modern multi will rue the day they did. You are trying to joint two dissimilar materials so get a thimble, a short piece of tube, or even a large shackle and drape a heap of unis over it and you can forget it and it will never leak. Due to the stringers on the inside of the bucc you may like to put a small bulkhead at this area to take the unis or even put the chainplate on before the stringers go on.

    I love ply but I avoid fasteners and penetrating it with bolts and chainplates with all my might. Nice dry bunks and no rot is the result.

    cheers

    Phil
     
  4. oldsailor7
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    oldsailor7 Senior Member

    Phil and Gary.
    Points taken.
    Cheers. Patrick. :D

    In 1977 I designed a 29 ft foam/glass Cat which never got built.
    It had the shrouds anchored to the foam sandwich sides in exactly the same way that Gary describes.
    However I would not have felt so sure if the hulls had been plywood.

    Strong points have been bolted through wooden members in boats since Pontius was a Pilot. ;)

    However I pondered this whole subject for a while and then went back to a statement which I made in a book I wrote back in 1978.
    " A boat with all the parts glued together with epoxy glue, all the recesses filled with fortified epoxy and then coated inside and out with a thin saturating epoxy, becomes a single solid unit. The result is an immensely strong, strain free and rot free free structure"

    I guess I can't go back on my own words, can I. ???
     
  5. cavalier mk2
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    cavalier mk2 Senior Member

    Hey Gary and Phil, I have neat bronze chainplates (very retro) on the Nicol but plan to change them out eventually. What Layup schedule would you suggest? It would be fairly easy to run the layup through the deck and into the existing hull structures to avoid bumps on the outer skin.
     
  6. catsketcher
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    catsketcher Senior Member

    A quick look up a composite design manual gives about 600MPa for uni E glass. (at 60% fibre to resin ratio) Now you don't want to get more than about 1% strain or you will get microcracking and as strain is proportional to stress. Back this off to 6 MPa and you will be very safe.

    Now Cav you have to get the size of the wire and and use its SWL to find a max load. Usually chainplates are about 3 times stronger that the wire. So find the wire load and then work out how much glass you need to get the load down to 6MPa. Make the chainplate about 100mm wide and glass over a tube helps get enough glass in there.

    cheers

    Phil
     
  7. cavalier mk2
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    cavalier mk2 Senior Member

    Sounds good Phil, while I have e-glass uni I have carbon uni which I'd use instead. I'll look for its data, should need less and have better long term fatigue. A bit less than 600 square feet in the rig, I think it uses 3/16, 1/4 max on the upper and lower side stays, I'll check.
     
  8. Gary Baigent
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    Gary Baigent Senior Member

    Cav, I get a decent sized thimble (larger than what you'd normally have for conventional rugging, my rule of thumb) glue them to the in or outside of the hull/float, then one layer of glass (to break metal/carbon connection) then lay in the lengths of uni- directional carbon. You run the long tows to correspond to the rigging angle and so carry the loads most efficiently. Once you've built up the tows to fill slightly above the concave shape of the thimble ... then that's as far as you can go and you've ended up with a mighty black composition which won't break or crack or leak brown stainless stains etc. I finish with some simple box weave glass over the carbon to smooth off the finish, then some filler.
     
  9. cavalier mk2
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    cavalier mk2 Senior Member

    Thank you Gary, sounds like what I'm after. I'll try it on the running backstay chain plates first. I'll do the math for fun but it sounds like a good thumb. I run Dyneema/ Amsteel there and eventually want to get all the wire out of the rig. Bronze thimbles could be used I suppose to eliminate any galvanic reaction.
     
  10. farjoe
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    farjoe Senior Member


    Phil,

    I have met with, at least one situation where the fastener was necessary.

    I have a ply daggerbox which spans from the keel to the deck. The flat part of the daggerboard itself only went half way up the box and this resulted with a huge force trying to push out the ply panel outward. My glue line as well as the glue joining the individual plies was and remained perfect but the panel still parted when the individual wood fibres within one of the ply layers parted. The solution was to replace the whole panel but fasteners were also employed along with a good glue line to ensure that the forces were taken up by all the veneers of the 6mm ply.

    Regards
     
  11. cavalier mk2
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    cavalier mk2 Senior Member

    Speaking of loads if I kept my chainplates outboard the carbon should be outside the ama at the top so the sheer timber spreads the load.
    Fanie, did you have a reinforcement/shelf at the loadpoint to carry the midsection loads? Bigger boats do.
     
  12. catsketcher
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    catsketcher Senior Member

    Think of uni like string

    Gday Fanie

    I would be very worried about not having a shelf halfway up the case as Cav says. All my boats have daggerboards that go only half way up the case and they have a massive bit of reiniforcing at the halfway point. As they are cats I put the case in a shelf. The inside of the shelf takes care of one tack but the other side gets more reinforcing. I put a timber piece (say 40x30mm) just below the top of the board at full down and then glass over it with unis. I ensure that I wrap the unis around the case and feed the load back into the shelf by spreading the ends out like Gary says. If you think of unis like string that works well.

    It makes the case bulletproof and much better at distributing loads

    cheers

    Phil
     
  13. Gary Baigent
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    Gary Baigent Senior Member

    Cav, I forgot to mention that first I glue the ss thimble to the gunwhale with just enough gap for shackle or spectra to thread through, doesn't want to be cantilevered so near the whole thimble is above the gunwhale (that is asking for trouble) - and when the long uni carbon tows are laminated (cross them just below thimble), finish with a few layers of same across the high point lever loaded area at lower thimble/gunwhale connection. I've found on my light boats that the tows should run at least a couple of handspans distance to spread the loads and provide strong adhesion. You could drape them further if you're concerned that that distance is not enough. On my beam connection to hull (where there are really high loads) I run the tows over coved frames to hull floor. Never had any problems.
     
  14. cavalier mk2
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    cavalier mk2 Senior Member

    Getting clear a mud Gary! An angle wedge on the gunwhale to position the thimble at the right angle would help spread any lever loads too. Think of Keith's old Vagabond for a reference. Is anyone doing forestays this way ? We have a great set up now but it would saved some hardware to go all carbon.
     

  15. Gary Baigent
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    Gary Baigent Senior Member

    Yeah, I guess the explanation does become convoluted.
    If you run a brace/wedge across the deck you'll have to make a Y junction against the thimble - to allow room for shackle or spectra, bit messy IMO.
    Sure, you can do exactly the same process with forestay/bulkhead/ring frame.
     
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