building new amas/floats from recycled beachcat hulls

Discussion in 'Multihulls' started by trip the light fandango, Apr 23, 2019.

  1. trip the light fandango
    Joined: Apr 2018
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    Location: Rhyll Phillip Island Victoria Australia

    trip the light fandango Senior Member

    No I didn't know that, thanks.
     
  2. redreuben
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    Location: South Lake Western Australia

    redreuben redreuben

    Yes, the paper last longer because the water washes the "dust" away, it cuts better because of the lube, like drilling steel.
    Add a few drops of dishwashing liquid to the water.
    With wet and dry 120 is quite coarse, you can then go through a few grades till 1200 after which you can buff with cutting compound. Say 120,320,600,1200 buff.
    Wipe or spray on India ink in acetone as guide coat. :)
    If you have large areas to rough down use an air powered sander.
    Obviously because electric and water aren't a good combination.
     
  3. trip the light fandango
    Joined: Apr 2018
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    Location: Rhyll Phillip Island Victoria Australia

    trip the light fandango Senior Member

    I didn't think of air powered, I've used wet and dry years ago with an electric orbital on flat surfaces successfully, useful information thanks redreuben.
    My epoxy has dried so I can go ahead, the bloody weight issue is annoying me though, to stop now and start a better longer lighter more expensive version is going to take many months to get to where I am now, I would dunce the daggerboard idea though . I'm surprised how many obligations I have that I didn't think took up much time, it has become apparent they do,..ha.. err. Throwing away what I have built without testing /using them would be pretty depressing. but save time and money.I just don't know whether the weight will sink their usefulness .
     
  4. BlueBell
    Joined: May 2017
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    Location: Victoria BC Canada

    BlueBell . . . . .

    Don't quit Trip.
    Finish what you started.
    Try and reduce or minimise weight.
    Get her in the water.
    If it is the disaster you're anticipating, then remove all the hardware and scrap it.
    You'll have learned a sh*t load and be that much wiser for the next build.
     
  5. trip the light fandango
    Joined: Apr 2018
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    trip the light fandango Senior Member

    I've cleared the decks and reclad the side of the house , as to wife's wishes, should be able to get the boat home and start working on it in the next couple of weeks.
     
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  6. redreuben
    Joined: Jan 2009
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    Location: South Lake Western Australia

    redreuben redreuben

    Ah yes the key to domestic happiness;
    “Do half of everything she can do and everything she can’t “
     
  7. trip the light fandango
    Joined: Apr 2018
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    Location: Rhyll Phillip Island Victoria Australia

    trip the light fandango Senior Member

    This will be the 3rd time I've gone to Vic roads and bought a 1 month trailer permit; I've got the mast and beams home.
    I've been going to bed planning new birdlike beams with enough float to keep the boat mostly out of the water upside down with a wishbone prodder that can both lower /raise the mast and be 2 arms of a tripod to lift a bag of water overturned. Also lightweight... lengthening the bows of all 3 to make up for the extra weight already gained, a slippery slope.
     
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  8. trip the light fandango
    Joined: Apr 2018
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    trip the light fandango Senior Member

    An update, reading advise it has dawned on me that my amas/floats are getting too heavy so I've started trying to find away to make them lighter.

    The H18 bow profile is too fine and I think pretty heavy since I've glassed on the H16 shoe[ to small a space to cut out theH18 bows]. , so it seems logical to cut them back about 600mm, put in a bulkhead and extend them about 1200 with more volume.
    I've looked around for a polyurethane supply of foam block but the one I have used previously with success has closed down.
    I can buy 10mm sheet that could bend to shape but the glass to make this strong enough including stringers including making a form is pretty complicated, heavy or expensive.
    So as BigFork has been considering I'm wondering is expanding foam poured into a form maybe an easier alternative
    1 kg of mixed GPF32 foam expands to a volume of approximately 15 litres.
    I would like about 100kgs of extra floatation so 7kgs of foam alone. I've read about how much punishment this part of the leeward hull cops it is going to need some aramid or carbon re enforcement and maybe some basalt or 300gsm S glass matting to keep it strong and light, the shape would try to minimise windage and spray and not look ugly.
    I'm confident that the hulls are strong enough to take the extra load, it does mean that my cases will be further back than I wanted but the hulls are mostly H16 profile so it isn't that big an issue if the daggerboards are quite small, it rules out semi foils though, too far aft probably, but they were a bit of a pipe dream anyway,ha.
     
  9. trip the light fandango
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    trip the light fandango Senior Member

    I'll explain the rationale, the amas are too heavy but if they're longer with little weight penalty the extra length begins to make the equation more feasible. they probably need to be a metre longer or even 1200 to gain the 100kg floatation, it is easy to buy short lengths of exotic matting and tapes from surfboard suppliers.
    It does mean that the cases are then 4 metres back from the bow, which means adding 1 metre to the bow of the centre hull using the same treatment becomes more tempting, which I wanted to do anyway but didn't want to look like a loony, I think my cover was blown some time ago on reflection. The density of the pour foam is 32 which has reasonable strength and rigidity.
     
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  10. upchurchmr
    Joined: Feb 2011
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    upchurchmr Senior Member

    So what are your ama's going to weight?
    Putting form in an enclosed hull doesn't increase flotation, it just increases the weight.
    Foam only helps if you get a hole in the hull.
    And only if it is closed cell.

    Every new joint you make in the hull just increases weight over what you could have had.

    The way to make amas lighter for their volume is to make new ones from scratch.
    I think this was on page 1 or 2 of this thread.
     
  11. trip the light fandango
    Joined: Apr 2018
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    Location: Rhyll Phillip Island Victoria Australia

    trip the light fandango Senior Member

    Hi Upchurchmr, I will check whether the foam can take on water and at what rate, I expect foam to absorb some moisture in a marine environment so at the risk of aiding the wicking process I think a drain to the bilge is warranted. Otherwise not your most erudite comment, unless it's a veritable sponge, then thank you.
     
  12. upchurchmr
    Joined: Feb 2011
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    upchurchmr Senior Member

    It's only not erudite to people who won't listen to the truth.

    A drain won't do anything for open cell foam, since the foam will only hold a certain amount of water.
    Then it holds that amount until you cut the foam out and throw it away.

    I don't think the physics changes "down under".
     
  13. trip the light fandango
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    trip the light fandango Senior Member

    I'll check with the manufacturer, I explained that the purpose was for a marine environment, they didn't mention any such issue. so I'll find out tomorrow and respond accordingly to your post.
     
  14. trip the light fandango
    Joined: Apr 2018
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    Location: Rhyll Phillip Island Victoria Australia

    trip the light fandango Senior Member

    Upchurchmr , Nothing worse than being uninformed, but most of the time someone employed by the manufacturer gives accurate information here. If immersed for a long period of time this type of polyurethane foam will take on water but it is designed and used as buoyancy for marine applications and other purposes. Its main issue is the reaction happens in 20 to 30 seconds, but small batches will blend with no issues.

    What I was eluding to with the less erudite comment was what you chose to leave out, oh and I am aware that floatation and volume are 2 different things , I would consider in this case that is semantics though.
    .increased waterline
    . increased volume
    .impact safety
    . the weight being removed.
    .the project has had quite a bit of effort already invested with some success
    . waste
    . the heading
    .money
    . trimaran amas proportion, the list goes on.
    I remember having to apologise repeatedly and being given quite a serve by your good self using the term sheer incorrectly, how do you roll with apologies?
    For what its worth I think your foam strip planking suggestion is the best alternative for me by the way, I want to avoid ply although I think for the right person /vessel it's excellent material[ good quality stuff]
    .
     

  15. SolGato
    Joined: May 2019
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    Location: Kauai

    SolGato Senior Member

    I was going to suggest cutting out portions of the deck and replacing it with plastic hatch covers but see from an earlier post that you have already done/planned to do that.

    Have you considered cutting off the deck joint and glassing smooth?

    Not only would this reduce some weight, but I would think it would help improve speed when the ama is pressed and reduce spray, no? A few Farrier Tramp owners have done this mainly to seal the amas to eliminate deck joint leaks.
     
    Last edited: Nov 11, 2021
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