Formula 40 singlehanded trimaran build log

Discussion in 'Multihulls' started by Corley, Aug 24, 2011.

  1. Timothy
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    Timothy Senior Member

    Rob I would like to have a look at that proa . Can you tell us where we can find some pictures or specs?
     
  2. Timothy
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    Timothy Senior Member

    Just thinking" 2 hours of sun to fully recharge the batteries" How can that be ? I have been at my wits end to find enough unshaded space on a 17 meter proa for solar panels at 150 wat per sqm to power a single 2000 wat TORQEEDO For 5 hours on batteries presuming I can charge an average of five hours a day.
     
  3. rob denney
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    rob denney Senior Member

    Photos specs etc at http://harryproa.com/index.php/boats/2012-10-11-10-18-30/custom-18m-melbourne

    Electric motor info in the Re: 18m Proa Motor/Sailing thread in the harryproa chat group at http://au.groups.yahoo.com/group/harryproa/messages?o=1&yguid=312404726

    Which is your proa?

    rob
     
  4. Timothy
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    Timothy Senior Member

    Rob sorry if I gave the impression that I have a proa . I have a 40' lead mine that I have been happy with for the last 30 years but as I now spend most of my time in Thailand my boating requirements have changed. My proa musings are more computer aided fantasy than design. I just checked out your website and had a look at Solitary. A solar electric version would be almost exactly what I have in mind.
     

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  5. ThomD
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    ThomD Senior Member

    My KHSD does that when I stuff the reefing, what a mess. I am not so great at the single handing thing.

    I questioned a lot of stuff about Kurt's boats when I built mine. Every detail worked out great. He know the hydro as far as I can tell.


    I do think that board is back for a typical KHSD, but isn't this two designs not one? The F40 in the day when he built his was some kind of near shore racing boat, singlehanding is a different thing where you want a boat that can take care of itself. I could see that position for offshore sleep while scooting along stuff, though that is way out of my comfort zone, so someone else would need to comment.

    I would not build a reverse bow offshore single hander. When i built mine it came with the trad bows, I redrew mine to be blunt. That made sense because more buoyancy is normally good, more waterline, better use of materials, added weight is trivial, probably slightly wet. I see no real world advantage other than trivial weight, on the reverse bow, though maybe someone can school me.

    The original F40 had the rep of being floppy in the beams. The nearest I got to it was onboard at the dock. It is ridiculously small inside, but other than that was a cool beast.

    One thing I would do, or at least quiz Kurt on, is relative weights. There are certain truths like the weight and structural properties of say Balsa core are great, but then when applied to your situation they turn out to be heavier than ply. You may need to actually run some numbers. There are various reasons for this. One is that material increments, may not create an efficient structure on the boat size increment. when dealling with foam, this is not a big deal. an extra mm of foam is light, but with balsa or ply it can add up. Also, more complex structures often come out heavier unless one really calculates off know complete samples.
     
  6. ThomD
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    ThomD Senior Member

    I'm all for composite, in particular because one normally has that stuff when building a boat, while a lot of boat builders do no have a metal working capability. All that said. With blasa decks, and 20-30 years of outdoors storage in Canada, my KHSD has never given any trouble with the SS chainplates. For one thing, there are only 3 of them, so it is not the mess of stuff that is on a boat with a lot of wire. I rigged a lot of it alpine style whenever I could, using cordage and load points.
     
  7. Corley
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    Corley epoxy coated

    It's handy to have Kurt's numbers to refer to from his own boat which give a good picture of the kind of weights we are shooting for. The balsa reinforced cylinder mold hulls worked out well and were within the weight targets that were envisaged and the target weight for the structure. The beams on this updated version utilise a carbon laminate that should be much stiffer (and a bit lighter) under load than the original.

    I'm not really fussed by the reverse bows they are quite mild and wont take much buoyancy away from the boat. We will get slightly reduced windage and weight as well I suppose and reduced drag hopefully if we stick the bows in, not really a big deal in the scheme of things and not much change to the overall buoyancy distribution of the float.

    Overall it's not the perfect singlehanded racing boat (what is? They are all compromises right) I'd like an ORMA 60 with a cut down rig or a Multi50 if I had the money but this strikes an acceptable cost/performance solution as an offshore capable boat. Although not really their initial design intention Formula 40's have proved quite seaworthy with many of them doing Atlantic races without any issues the boats I've heard of capsizing have been wind rather than wave capsizes hence the relatively modest rig I'm looking at for this boat. They also can also make multihull category one safety requirements with a bit of work which means more events are open to them. My goal when/if I get this boat constructed is to sail conservatively "Fast but not furious" as Loick Peyron would say.

    The advantage we have these days too with fitting out weight sensitive multihulls for offshore work is that the Minitransats have spawned their own weight conscious fitouts which helps with an offshore multi as much of the lightweight gear can be bought off the shelf. With a fuel cell you can sidestep the heavier genset requirements and still have acceptable charging ability and reliable power.
     
  8. Corley
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    Corley epoxy coated

    I visited Ben the other day who is building my daggerboard. It's looking great he constructed the board in a melamine mold with vac bagged laminate and core material it looks great shapewise with a thin trailing edge. The board has a balsa core with sacrificial foam nose and tail sections and a sacrificial foam tip. The daggerboard case also integrates a crash block to absorb any impacts with minimum damage. We are going to make the crash block a reasonably close fit around the board to minimise drag from water entering the daggerboard case. The board is ready for final fairing and paint. This is the board designed for the half height case so to meet Category 1 multihull regs we have to fully enclose the daggerboard case and we have roughed out how to make a shroud to enclose the daggerboard between the half height case and the underside of the deck to fully seal the area when competing in events that require that standard.
     

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  9. cavalier mk2
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    cavalier mk2 Senior Member

    Corley, you don't save much weight with a short case and lose a nifty compression post that helps distribute loads. It's also dryer down below if things go wrong with the shower curtain.
     
  10. Corley
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    Corley epoxy coated

    A compression strut at the position of the daggerboard will not serve any useful purpose. Kurt ties the daggerboard case into the (limited) internal furniture with a strong laminate so the furniture helps distribute the loads over a large area on the inside of the hull. Pretty elegant really from an engineering standpoint.
     
  11. cavalier mk2
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    cavalier mk2 Senior Member

    It ties 2 plates together. The hull and the cabin/deck, and helps spread the mast loads, depending on where it is stepped of course.
     
  12. petereng
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    petereng Senior Member

    Hi Corley,
    Just to discuss the ply mast. I have designed and supervised the build of a 22m free standing mast for a 60ft catamaran (plus many other masts). The sizes being described here I feel you could it just in high grade plywood. Putting some UD on the outside is of no benefit. I feel you should stay in the ply, fibreglass or carbon world. Mixing materials rarely gets the best out of any of them. Take F17 plywood, it has a modulus of 14GPa get F27 at 18.5GPa). If you used 8mm ply this would be equivalent to 3.2mm of good fibre glass (35GPa) or 1.5mm of good CF (80GPa). the CF would be 2.25kg/m2, the glass would be 5.7kg/m2 and the ply would be 5.2kg.m2. These would have the same in-plane stiffness. As usual CF wins and the others are similiar in weight. I'd even look at infusing flat glass sheets and tortoring them like the ply. Once you get into the realm of big sections you don't need high strength. I think you could work up a ply design quite easily. Plus once its saturated in resin the ply gives much more strength than the books quote. cheers Peter S
     
  13. hump101
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    hump101 Senior Member

    Do you have a weight for the board?
     
  14. Corley
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    Corley epoxy coated


  15. hump101
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    hump101 Senior Member

    Many thanks for the rapid reply. I'm thinking about how much I could save replacing the two ply-cored boards in my F40 cat, and this gives me the ballpark. Mine are 62kg each, but are full length through the hull when fully down, so probably a little longer.
     
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