Has anyone tried...

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

  1. Moht473
    Joined: Mar 2014
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    Moht473 Junior Member

    I want to build a couple simple 7' long floats for a slow trimaran sailboat. I looked at some of the different techniques that you see on YouTube etc. One of the techniques was intriguing. Basically, you make your own prepreg. Start with dropcloth material that epoxy won't stick to, put your glass layers on top of that. Impregnate the glass and put another dropcloth on top then squeegee out the excess glue. Now you have a simple panel. What I'd like to try is cutting the prepreg into a rectangle while still wet but leave tabs every foot or so. Then suspend the whole thing from the ceiling to cure. Voila, a half pipe which could be the bottom of the float (shape should be a catenary). Has anyone used this technique? :idea:
     
  2. gonzo
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    gonzo Senior Member

    Those techniques have several drawbacks. First, it has a very limited amount of possible shapes. Second, it is very difficult to control the shape. Third, it is virtually impossible to make several panels of the same shape. Finally, why do you want to build a slow trimaran? Their main advantage is speed.
     
  3. Moht473
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    Moht473 Junior Member

    Atq

    Appreciate the reply, but prefer someone answer the question (ATQ). :rolleyes:
     
  4. Petros
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    Petros Senior Member

    what you propose is actually not that easy to get consistant results, you will spend a lot of time tinkering with the tension, shape etc to get a decent shape. And a single skin is not strong enough, so once cured you would have to add additional layers anyway.

    stitch and glue would likely be just as fast with more predictable results and less waste. I once built a skin on frame kayak using fiberglass as the skin, this would also result in a more predictable shape (stretch the skin over the frame and than wet out the cloth). You could leave the stringers and remove the frames and than put another layer on the inside. would make a more predictable shape.

    besides, your hull costs are not the most expensive part of the build, just one of the many. why take a risk on such a process?
     
  5. Moht473
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    Moht473 Junior Member

    OK, so far no one has tried it. If you recall, that was the question. Has anyone actually tried the process I outlined? And please, don't tell me what you would do instead, I just want to know if anyone has done this. One of the things they taught me in the nuclear navy, ATQ.
     
  6. redreuben
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    redreuben redreuben

    Maybe you should go back to the Navy and ask for some advice on evaluating answers.
    You won't be told so just do it, then come back and tell us all about it. :D
    P.S. Use an equation or a chalkline to derive your shape then transfer it to stations and use a thin formica faced board as a reproducible mould. Male or female, whatever works for ya. :D
     
  7. Mr Efficiency
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    Mr Efficiency Senior Member

    Isn't that what John McEnroe famously said to the umpire ? ATQ......JERK !!!!!!!!!! :eek:
     
  8. rwatson
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    rwatson Senior Member

    Its been done a lot - but only by accident. I have had a prepreg cure too quickly as it was being transported before it got laid out properly. edit: Oh, a small detail to add. The glass was suspended between two 'broomhandles', and left to go off when it started smoking. What 'everyone' know is that unsupported glass warps while it cures. In a stretched fabric support for example, it creates a concave surface. The bit on the 'broomhandles' was fairly uniform.

    Its so bleeding obvious to anyone who has tried to hang a wet sheet on a clothsline, that you will go mad trying to tension the edges to avoid wrinkles and curves. You could tape or nail the edges to solid wood, but you would get a wavy waterline as the 'panel' cured freeform.

    Why dont you want to make a simple form, and put the layup on top or of that ? Its not that hard to do properly.

    But as previously mentioned - a layup of glass 'sheet' thick enough to be strong enough for a trimaran hull would be way heavier than it needs to be.
     
    Last edited: Mar 19, 2014
  9. Moht473
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    Moht473 Junior Member

    Thanks

    At least rwatson knows how to answer a question.
     
  10. Fanie
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    Fanie Fanie

    I think every one here gave you a decent answer. The problem is you want only to hear a certain type of answer.

    Most of the okes that did reply gave you some good advice. If it was so easy and simple to just hang fiberglass up and a hull appears... I guess the washing lines would be hanging full of hulls in the making.

    Take some advice, go to a little trouble and form the hull to something that resembles something workable and make it something we won't all be ashamed of or laugh our butts off at.

    The worst of a poorly made floating thing is when it stops floating and people drown, or it becomes expensive when things get wet or sink. Some even leave their poor handiwork abandoned for others to clean up.

    Don't be ignorant.
     
  11. Moht473
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    Moht473 Junior Member

    Who asked you?

    Don't be arrogant. I may be ignorant, but that is correctable--Which is WHY I asked the specific question and FINALLY got a specific answer. Arrogance is something completely different and something you probably have had to live with your entire life.
     
  12. rasorinc
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    rasorinc Senior Member

    Your attitude is going to make it difficult Moht473 for others to comment on your postings.
     
  13. Fanie
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    Fanie Fanie

    Who asked you ?

    You did.
     
  14. nimblemotors
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    nimblemotors Senior Member

    Can you give links to the videos where they use this technique?
     

  15. Petros
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    Petros Senior Member

    consider boats have been made since before recorded history, fiberglass boats have been around for over 60 years, no one advocates this kind of construction. You think there might be a reason for it?

    I do know of a number of instances where "free form" home built canopies are made for home built aircraft, using heated plexiglass (ploycarbonate), and despite the considerably simple concept of using compressed air to form heated plastic, most find this method not very practical.

    So, go ahead and prove everyone else is wrong. Knock yourself out. I have built some 20 small boats using various materials, I have rebuilt some 20 or so cars, I have built my home and lots of other things and I have over 30 years as an engineer in a number of fields. I would not try it.

    You might try it on a 50 percent (or less) scale hull and see what you get, you can use it as a day sailor if it works and you might actually teach us all something.
     
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