Vacuum infusion Male vs Female

Discussion in 'Sailboats' started by pironiero, Oct 20, 2020.

?

Which one

  1. Female mould

    0 vote(s)
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  2. Male mould

    0 vote(s)
    0.0%
  1. Mr Efficiency
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    Mr Efficiency Senior Member

    Without seeing the lines of the boat, or something closely related, not a lot more can be said,
     
  2. pironiero
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    pironiero Junior Member

    Let's take sunfast 3300 for example then, or basically any wide body with flat bottom and chine at the back
     
  3. fallguy
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    fallguy Senior Member

    if the boat gains 5 kilograms; it is leaking or improperly sealed
     
  4. pironiero
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    pironiero Junior Member

    Im pretty sure that you are wrong, In normal use the moisture content of wood varies between 8% and 25% by weight, depending on the relative humidity of the air. And winters where i live is very humid, or is all just a big misunderstanding
     
  5. Mr Efficiency
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    Mr Efficiency Senior Member

    If your boat has the reverse bow, you would need a split mould. It's just madness talking about making a female mould for a complex shaped 10 metre boat, to build one boat. Especially an unproven hull. I think you should explore lightweight methods of building in timber and veneer, and sealing it properly.
     
  6. pironiero
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    pironiero Junior Member

    Can you clarify this? im still not sure if i got you right...
     
  7. pironiero
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    pironiero Junior Member

    But what if i disassemble the bow part of the mould, if vacuum infusion had gone right-i don't need it anymore and you can tell if something wrong with a hull by just looking at it without even taking hull off
     
  8. Rumars
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    Rumars Senior Member

    Pironiero, is your dad's boat done with epoxy? And if yes, did he seal the inside? If it is done with polyester what you describe is normal, with epoxy not.

    You can do a direct female mold, but to get the surface to gelcoat quality (so you don't have to do any sanding on the actual hull) is very difficult. The build you linked did not try to achieve that, they infused with peelply on the mold surface and sanded the hull then painted. This way they minimized the amount of filler that remained on the actual hull. I would only try it with plenty of experienced people available. It is much simpler to fair the hull directly, even if it means some more kg's of fairing compound on the hull. To infuse foam you don't need an actual closed mold, stations with battens are ok as long as you make sure that the foam surface is airtight.
     
  9. pironiero
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    pironiero Junior Member

    Yes
    No
    I Will consider it, thank you very much.
     
  10. Rumars
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    Rumars Senior Member

    Not sealing the inside with epoxy (and any solid wood furniture) explains the weight gain. If you seal the hull completely there will not be any discernable moisture exchange, and a racer will not have heavy furniture to speak of anyway.

    For "moldless" foam infusion on a "walk in" mold see the Fram trimaran blog. The construction of the first trimaran float http://www.fram.nl/float1.html
     
  11. pironiero
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    pironiero Junior Member

    What does it mean?
     
  12. Rumars
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    Rumars Senior Member

    It means a mold where you have easy access to both sides of the foam by walking in between the station frames. The frames can be on the outside or inside and the boat can be upside down or right side up, the principle is the same. Of course some boats can only be done one way, a narrow multihull or a small monohull require the frames on the outside (female mold) if you want to be able to walk between them. Big monohulls can be done on male molds because a person can fit into the inside space.
    The big advantage is beeing able to fasten the foam to the mold battens from behind, using screws (or sewing), so that the surface to be laminated is not pierced. This way you have less holes to fill and vacuum infusion or hand laminating is easier.
     
  13. pironiero
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    pironiero Junior Member

    Thank you
     
  14. fallguy
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    fallguy Senior Member

    560A360B-6151-45A6-94D5-14F709C8D2EE.jpeg
    Transom(less) view.

    I defer to Rumars here. He is a much wiser forum member; despite a recent disagreement.

    A well designed female mould for no fairing is really a lot of work for the gains. I built my boat in a jig mould and I did not track the amount of compound, but we are less than 200 pounds of fairing and paint per 32' hull. Exterior joins are tapes in rebates and may have had a few rebates shallow, etc. More jig prep could have reduced it further as well. The walk in aspect simplifies the process for easy access. This hull was built with wetbagging. But the beauty here is you get to walk in an apply bulkheads. The entire boat can be built and the outside finished later. I am not certain whether you would want to laminate the walking surface; that is a detail..

    This jig is not perfect. I would have done a nosecone instead after dealing with the narrow bow. This boat is about 24" at the bottom only, but pleasant to work inside.

    I am surprised noone flips these out of the mould and fairs the foam before skinning. That would result in a near zero fairing compound weight as long as you didn't sand away lotsa hull. But I suppose you might be breaking class rules that way.

    View to forward.
    CD5C3ED0-46B8-4405-8A6C-5B5F65D1B622.jpeg
     

  15. pironiero
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    pironiero Junior Member

    I believe the reason is that not consistent foam thickness makes hull structurally weaker, because foam adds rigidity to the hull as well
     
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