Has anyone tried...

Discussion in 'Fiberglass and Composite Boat Building' started by Moht473, Mar 18, 2014.

  1. Fanie
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    Fanie Fanie

    At 7' I think he's already settled for the 50 percent (or less) scale hull.

    The easiest way to make a former is to use wood strips or metal tubing. I prefer metal tubing. They must be of a rigid size but must still be able to curve with your design contours. These you want to arrange around a center so that looking through the length the outside of the strips connected around makes up the form you require.

    Towards the bow they come together to form say displacement, and towards the stern a bit fatter and flatter to reduce drag and pitching.

    The former you have to make so you can strip the inside parts out to reassemble for the next hull.

    Once you have the form to your liking, you wrap it with plastic so that the plastic forms the support and spans all around the hull.

    Now you flip the jig upside down, wet the glass on some PE or other suitable sheet, squeegee excess resin out to reduce weight, take the glass and lay it over the form so that the glass is supported by the plastic and doesn't stick to the former.

    You have to calculate the amount of layers which depends on the fiberglass thickness you use to provide the correct thickness, stiffness and strength.

    You can paint it with a water based high quality outdoor paint and lay peel ply over it to reduce finishing, the paint will help fill the small cavities. Haven't tried the paint and peel ply but it should work.

    When dry enough in a few hours you carefully peel the peel ply off, flip the hull and cut the edges just above the top deck.

    Wrap some plastic around the upper edge all around so the deck won't stick to the hull.

    Now you can repeat the same process with the top and glass it over, overlapping with the hull.

    When the deck is cured, you can pull it off the hull, it will be a perfect fit. When re-assembling after you stripped the jig, fitted flotation foam and trimmed the deck edges, fitted the beams, etc, you smear some industrial sealer on the lip and replace the deck. It's going to fit like it came off. The sealer will seal and hold the deck in place.

    When the sealer has dried it should be a thing that can float. I don't think there is an easier and quicker way to build a boat.
     
  2. Mr Efficiency
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    Mr Efficiency Senior Member

    You want the shape you want, not the one the material takes up of its own accord. If your want a "half pipe", use a half pipe of PVC or something else as a former. What use a constant section pipe would be as a hull, though, is not clear to me, how do you treat the ends ? Just slap a cap on each end ? I am not seeing how this "technique" ends up in any kind of hull you'd want, or need.
     
  3. Fanie
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    Fanie Fanie

    I think he's just upset because it seems so simple a thing to do and now it seems it's going to be a big operation.

    Buy two kayaks and rig them up. I made mine foldable and it works very well and easy, I haven't fitted sails yet but the rudders and daggers are cut..
     
  4. groper
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    groper Senior Member

    Im not convinced... i think this could actually work... Ive often thought of something similar, but never tried it. Provided the shapes are developable, then the fabric should drape perfectly fair and without wrinkles. Of course not all shapes will be possible, but i think some very workable ones would be possible.

    Bit of history, everyone thought you had to be some kind of professional guru to do resin infusion, its not the case and ive proved it along with many other amateur builders. Noone thought that such a cheap slap together flexible mold would be possible to do infusion in, the vacuum will collapse the mold they said... - i proved its possible and worked very well in fact;

    [​IMG]

    [​IMG]

    The way i envisioned a similar idea to the OP was like so;

    1. Affix some plastic film (such as a 100um PE) to a batten of some description along each edge, like a 2x1 lumber etc. Use staples or similar etc... Seperate the battens and let the plastic hang between. The degree of curvature is controlled by the seperation of the battens, a round or elliptical section hull shape will result and is a desireable shape for something like a multi hull ama. This could then be over layed with `glass, transfer media etc etc and envelope bagged for infusion with a second layer of PE film. This could create a nice midbody hull section. I specifically refer to infusion, because you have infinite time to setup all this up and get it all hanging right before you infuse, as opposed to a wet lam, everything would move and change as you added resin and thus weight. Youd be constantly racing against the clock in terms of pot life and would most likely end up in a mess...

    2. For the fore and aft sections, we could then use a partial cone section (100% developable) bonded to each end of the midbody section. Again done in the same way, however the battens would be touching each other at one end and have the same seperation as the midbody at the other end. Also the length of plastic draped between is reduced as it approaches the bow end so you end up with a constant round section of reducing diameter, or a half cone in other words.

    3. If the chosen plastic film was stretchable - like some films are, then the battens could be curved and the plastic could drape to some amount of compound curve as it stretches and hangs.

    4. If enough glass layers are used/infused, along with perhaps some core mat type material, eg soric, there is plenty of stiffness available and a lightweight structure is definately possible.

    5.All of this amounts to eyeball boat building. You cant design a specific shape and make it so, as it would be very difficult to predict the exact hang and stretch of the layup. But this doesnt mean you cant build a good boat, many of the previous greats and even some of the current minds still build boats in this manner - just letting shapes form and evolving the design around what you have as it takes shape. You will be able to get things very close, just not perfect in terms of overall dimensions. Certainly close enough in order to make reasonably accurate calculations of CoB , prismatic, draft, beam, and displacement etc...

    If i had the time, id try an experiment, but alas i have nil...
     
  5. Mr Efficiency
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    Mr Efficiency Senior Member

    It would all work like a charm once you got the "hang" of it. The first 25 years of learning the art of it would be the worst.
     
  6. rwatson
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    rwatson Senior Member

    Who was the 'no-one' who said it wouldnt work ??

    You made precise forms, inserted a substantial 'former' in them, and vacuum formed them to ensure conformity to the mould.

    The OP was trying to hang pre-wetted, non restrained layers of cloth.

    World of difference.
     
  7. Mr Efficiency
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    Mr Efficiency Senior Member

    As John Mc Enroe would say, to anyone intending to build boats this way.........

    " You have got to be joking !!!! " :p
     
  8. Fanie
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    Fanie Fanie

    The problem wit vacuum forming Groper, is you can achieve one atmospheric pressure at best.

    With pressure you can achieve several times atmospheric pressure... how can we use that instead ?
     
  9. nimblemotors
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    nimblemotors Senior Member

    Are you going to give a link to the video??

    BTW, if there is a video of someone doing this, then you already have the answer to your question, someone HAS tried it. Duh.
     
  10. groper
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    groper Senior Member

    The proposed idea for using plastic molds doesnt have much to do with your question. 1atm is 14.7psi (sea level) more than you get with wet lam... It has been shown to produce aerospace quality laminates if executed correctly.

    However if you wish to laminate with higher pressures of +1atm, then you should look at bladder molding. You will need proper high strength fully closed molds, and it doesnt lend it self to large structures as the bladders and volume of air just gets too large. Probably dangerous too on a large scale...

    Great for making tubes, and other hollow type structures of not too large size..
     
  11. rwatson
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    rwatson Senior Member

    Thats not an issue. 1/2 an atmosphere is plenty. You cant make the glass laminates any thinner no matter how much weight you apply. Glass is virtually incompressible.
     
  12. Fanie
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    Fanie Fanie

    The idea is not to compress, but to get as much resin out as possible.
    (Assuming there is no air in it)
     
  13. rwatson
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    rwatson Senior Member

    Yes it is - you get the excess resin out by compression !!!

    But, you don't want the resin to be lower than the top layer of glass - you need the compressive strength. The thickness of the layer is part of the strength calculations.

    Nor do you need to compress the glass so much that there is no resin between layers of glass. You have to have enough to provide adhesion.

    You are looking at OPTIMUM resin ratios, not MINIMUM resin ratios.

    For example, you don't put a ten ton press over your panels - its counterproductive.
     
  14. Fanie
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    Fanie Fanie

    I saw some lids made with the mold compression method, the strength is impressive for it's thickness, and it is very dense. They use this method because it is fast to do production, probably run it at a high temperature too.

    Vacuum is easier since you implode on a ridgit form instead of trying to create a pressure over a large area. We think about pressurizing the air, pressure molding are done between two solids.
     

  15. Fanie
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    Fanie Fanie

    For instance, I wanted to build a frame for a hatch that would close water tight when the lid is closed. The frame is rectangular, so laying glass up evenly is difficult.

    If you use a pressure method with a male and a female part, you can overlap the wetted glass on the corners. The pressure forces the outcome evenly, where with a vacuum process the overlapped corners are thicker and it doesn't look so neat. With the pressure you can also get some fine details like a logo which may be challenging with vacuum.
     
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