Please help with cheap ama construction

Discussion in 'Multihulls' started by stove, Feb 3, 2015.

  1. Turnpoint
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    Turnpoint Junior Member

    A decent layup of the mold would be 15 mils of gelcoat, 1 1/2 oz mat, 24 oz roving, 1 1/2 oz mat, 24 oz roving. Then build a supportive box out of plywood around it that is tabbed to the back of the mold. Finish laminate thickness will be around 1/4".

    To try to get a good release from your plug you should start with a mold sealer like chemlease. The plaster is really porous and this will help seal off the surface. Then wax and then pva. You might be able to pull the part without tearing off the top layers of plaster if all goes well.
     
  2. stove
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    stove Junior Member

    I was also thinking plastic sheeting, I read elsewhere that one can use box sealing tape on the plaster and then plastic sheeting stretched over the plug. The hull will then release with the plastic sheeting still attached to the inside of the hull which can then be removed afterwards. This can then be repeated with the second hull. The idea is that the plastic sheeting will release easily from the plastic tape, no wax or PVA
     
  3. catsketcher
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    catsketcher Senior Member

    Stove

    You don't have to make a skinned mould. Just mould ribbands - or wood strips over bulkheads is fine for core construction. Use about 40-19 meranti spaced 150mm apart and there is no need to put a skin on it. Then screw the core on. When the core is screwed on you jump inside and put dabs of epoxy filler on the core and ribband to hold it then you pull the screws out.

    With the screws out and holes filled you put 600gm biax on the outside. Make a rough cradle to hold the thing and pull it off the mould. Then clean up the inside and put 600gm on the inside with reinforcing under the main bulkheads. Put an extra bulkhead up the front in front of the front crossbeam bulkhead.

    Then flip it back over and fair it up using a notched trowel epoxy mix.

    No need to make a skinned mould if you use a core.

    cheers

    Phil
     
  4. zaca60
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    zaca60 Junior Member

    I do not think you will get a low cost solution with this setup. For a heavy Soling hull, you could do it with a pair of suitable beach cat hulls as amas. They will be cheaper and stronger in money/weight than what you can build. And will bring you faster on the water :). Good luck anyway, will follow your experiment!
     
  5. redreuben
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    redreuben redreuben

    I agree that beach cat hull would be the cheapest, but what to use ? Seems even Tornado is not big enough.
    If your going cheap then you will be using polyester resin which will attack any tape or plastic covering. Cheap way to seal the plug is - polyester resin or gelcoat, one or two coats unwaxed followed by a waxed final coat, you can even give it a wet&dry and polish it.
     
  6. stove
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    stove Junior Member

    I will make a test sample on part of the plug using different release methods over the weekend. I will report back soonest. Thanks again guys
     
  7. zaca60
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    zaca60 Junior Member

    Big enough for what? As far as i understood you cut of the keel from the Soling hull and use it (the hull...) as the aka of your future trimaran. The Soling is a 3-man keelboat with a 500kg keel and the hull form is not designed to go very fast unballasted. I do not know what rig you will use, but as it will not be a racing boat, you will probably not want to fly the aka...:D. If you bury a beach cat ama, you know your boat is overpowered. I do not expect you to go faster with more volume in the amas, because you will have to build a lot of structure into the aka and the ama to support the forces, which makes your boat heavier (but the aka not more up to his new role).
     
  8. redreuben
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    redreuben redreuben

    Zaca60;
    The OP originally stated that his plug is a Tornado hull stretched to 9m.
     
  9. zaca60
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    zaca60 Junior Member

    Yes, sorry Redreuben... Depending on the plugs form you could strip plank over it; you will save a lot of sanding and get a fine hull surface.
     
  10. stove
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    stove Junior Member

    Hi all
    I've made some test samples over the weekend, tried different kinds of plastic sheeting. Redreuben you were correct, the polyester attacked all of them. Then I tried sheeting that looks like plastic but it's not a plastic it's made of cellulose and it's called Cellophane. Cellophane works great. I can buy cellophane for 35 cents (US) a square meter so it's relatively cheap. After googling "Cellophane" I realized that it has been used as a release film on polyester for some time. If I coat my plaster plug with cellophane adhesive tape (Sellotape) and then stretch another cello film over the tape I've got a great release system. The test sample released very easily with a layer of cellophane stuck to the inside of the lamination. It was very easy to peel the cellophane from the sample and it left a mirror finish. It might even be possible to heat shrink the cellophane over the plug for a better surface. I think it will even be possible to use cellophane as a type of peel ply on polyester as the last layer, it will leave you with a great surface that needs less sanding.
     
  11. redreuben
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    redreuben redreuben

    And a dozen people go "oh **** cellophane, of course" !!!!!
     
  12. stove
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    stove Junior Member

    Two pics of mono hull Soling converted to Trimaran. Yellow trimaran uses Soling as center hull with two self made amas.
    The other trimaran uses Soling center hull with added cabin and Tornado hulls for amas.
     

    Attached Files:

  13. stove
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    stove Junior Member

    Hi
    I'm struggling to find single skin polyester-glass scantlings for my amas. I can get woven roving 600g/sm at a great price (old but still in plastic liner). Is someone brave enough to give me a guestimate layup of this woven roving 600g/sm followed by csm 450g/sm. How many layers of each? Will be greatly appreciated.
     
  14. redreuben
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    redreuben redreuben

    Stove;
    Solid glass will be very heavy, try and find coremat (as used by Sundance pools in Capetown) It's like a fibrous blotting paper to bulk out the laminate, not incredibly light but lighter and cheaper than solid.
    Maybe 600wr 4mm coremat 450csm
     

  15. redreuben
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    redreuben redreuben

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