Historical multihulls

Discussion in 'Multihulls' started by Gary Baigent, Feb 26, 2012.

  1. buzzman
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    buzzman Senior Member

    Yeah, well that was my rider - it's easier if the foil shape is constant - so a rectangular foil in side elevation.

    You just need a dead flat workbench the length/height of the foil, and set up two 'guides', one representing the height/width of the mid-foil rib, the other the mid-point of the trailing (or leading) edge, whichever 'half' you're working on.
    l
    So, maybe an _l....................l_ shape open topped box.

    Then *carefully* curve the hot-wire tool to the shape of that section of the foil, and run the tool from one end to another, slowly, while an assistant or two follows behind lifting off the waste.

    Probably you'd need to do four sections, so half of each half, if you get my meaning, so you always had a dead flat base to the foil section you were hot-wiring into shape.

    Glueing them together is easy-ish - same way we old-time chippies used to glue laminates to particle board or ply - using 'separation sticks', which in this case would need to be coated or wrapped in polyethylene plastic that would not stick to the epoxy 'glue'.

    Apply glue immediately ahead of the area being glued, add 'sticks', crossways, then lower the top piece onto the sticks then slowly one by one remove the sticks.

    With laminates, we used contact glue, so you'd glue the lower surface, wait till it wnet very 'tack dry', then add the sticks, then lower the laminate over the top, then pone by one remove the sticks and press the pre-glued laminate to the pre-glued surface. That's the point of 'contact' glue......

    But with epoxy, which goes off so quickly, you might need to have someone mixing small batches for you so you could keeep a 'wet edge' going.

    Would be tricky, but do-able, in a good dry clean workshop.

    And the resultant foam core would be *light*!!!

    Skads lighter than the older ply-style wings like the Danish one and probably those of GB's efforts as well.

    It would need a good force designer to decide what laminates to put where, but my guess would be mucho carbon strings or tapes down the centrelines of both sides and the leading edge, with maybe a bit less carbon fabric over the foam bits in between.

    But it *would* be light, especially if the epoxy over the fabrics was vacuum infused.

    Eventually the tech has to catch up, and when it does, fabric sails will go the way of the dinosaur - at least for big-bucks racing.

    Or am I just another dreamer..??
     
  2. Gary Baigent
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    Gary Baigent Senior Member

    Here's the mail address for the Danish Cs:

    http://www.voilesetvoiliers.com/cou...le-plus-etonnant-des-classe-c/deliaPreview=1/

    Buzz, your approach seems very complicated to a backyard build crude butcher like me. The simplest way, imo, would be a male mould in foam, a long D shape with the trailing main section the same width as the mid chord, faired, then carbon box weave and unidirectional laminate over with peel ply for finish. Sure there would need to be some lightweight filler but if careful, you can get an excellent finish. Then chop/acetone out the interior, slide in and glue your already prepared carbon I beam. pull the trailing sections together to the cup shape (for leading second element) and glue. The second (or third) sections could be normal frames, stringers and heated plastic skin.
    Of course the correct build would be split female mould ... but that is a long job requiring perfection .... and I yam what I yam.
     
  3. BobBill
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    BobBill Senior Member

    Off topic.

    Gary, Buzz' ideas notwithstanding, I too am in the backyard butcher club. I was going to make a cutter out of a rheostat, copper wire and plug it in, but when I saw the cost of foam blocks I went for a cast off Hobie 16 hull, after I could not find a trailer for a nifty Tornado offering by our generous Mr. Upchurch here. I am butchering this moment. Pics on another cat forum here.
     
  4. buzzman
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    buzzman Senior Member

    GB - I hear ya, I hear ya, but my version with the foam retained provides buoyancy in the inevitable capsize and adds 'some' strength, admittedly mainly compressive rather than tortional or linear, but the carbon and e-glass outer does that.

    And if you want to pre-place the carbon I-beam between two blocks of carved foam, then that simplifies the 'adding it in later'. Honestly can't see the point of removing the foam. It weighs almost nothing.

    And my method, also effectively a male mould, vacuum-infused with peel ply, would require little to no finishing.

    Not that I've ever done it myself, but from what I've read,and watched, it 'ought' to be possible......

    And if the first one 'works', why, then make a female mould from it and voila, a new series is born.... lol


    Did you scroll down the Voiles page and watch the vids as well? Cool foilies like Groupama et al.
     
  5. Gary Baigent
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    Gary Baigent Senior Member

    There's a lot of running rigging and blocks and things to go inside, Buzz.
    Yes, V et V have great videos.
     
  6. buzzman
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    buzzman Senior Member

    Yeah, true, good point, normal masts are hollow for a reason.....

    But on a wing, what rigging would you need? I understand low down you'd need turning blocks for the moveable foil, but the pivot lever for the main wing would be at deck level, surely...???

    I know nothing about these things, just curious.... :)
     
  7. brian eiland
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    brian eiland Senior Member

    Somewhere I posted a neat photo of something like that, but I can't remember where at the moment.
     
  8. Ooks
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    Ooks Ian

    Grainger MTB 920

    Hi all - looking to the collective wisdom pool here.
    Mad Dogs Tip Truck has been sitting unloved for about 5 years and is for sale pretty cheaply on gumtree: $7500 - but has a fair amount of $$ and effort required to get her up to scratch. No sails or outboard, identified de-lamination and probably rot in rear starboard beam. My fairly uneducated guess is you would spend around $30K, still good price for what she could be.

    But - she is constructed of balsa core and that sort of scares me. What are your thoughts on this method of construction and a boat that has sat clearly neglected for at least 5 years? boat was built in 1994.
     

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  9. buzzman
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    buzzman Senior Member

    Balsa core.......scary.....once water gets in it wicks along, so could be bad.....

    But if it's only the beam delaminating...it ought to be fixable.

    Get it on a slip, let it dry for a day or two, and go over the hulls carefully with a moisture detector. It's riding high so doesn't look like there's any extra weight in it, so might be OK, but I wouldn't buy it without a thorough on slip examination and a marine surveyor's report.....

    But if it checks out, $7500 is an OK price. As you say, might need $20-30K to get it race-worthy or cruise-worthy, but that's still not bad and could be done over time, not all at once, unlike buying a new boat.
     
  10. oldsailor7
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    oldsailor7 Senior Member

    I like Malcolm Tennants way of making foils.
    Bend a sheet of aluminium around a steel mandrel, (pipe), to form the required section.
    Allow the metal sheet to spring open, wax the inside, paint or spray in a gel coat. lay in two or more layers of glass/resin, pull sides in to restore the foil section and clamp the edges together. Seal one end and pour in expanding foam. When all has cured seal the other end and you have a complete dagger board, with a perfect foil, a low friction surface, lightweight and strong. :D
     
  11. Ooks
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    Ooks Ian

    Mtb 920

    Thanks for reply Buzzman,

    MDTT is now sold so I hope whoever got her grabbed themselves a bargain rather than a big problem.

    Thanks again
     
  12. Corley
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    Corley epoxy coated

    Those Grainger MTB920's are demountable so it's not too much of a problem to fix individual parts. It would be nice to see Mad Dogs Tip Truck repaired it's quite a historic racing multihull in it's own right.
     
  13. Ooks
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    Ooks Ian

    Yeah had not realised that till I saw the pictures. Seller told me Mad Dogs Tip Truck was significantly lighter than some of her contemporaries (Big Bird?) Out of interest is this likely due to the construction with balsa at the time?
    Anyway hopefully the new owner finds their way to the forum and we hear how she goes.
     
  14. Corley
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    Corley epoxy coated


  15. Gary Baigent
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    Gary Baigent Senior Member

    Marvelous photograph of the Walter Greene trimaran ex-Friends and Lovers, now Bilfot, preparing for Route du Rhum. This boat was originally sailed by Kiwi Phil Steggal.
     

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