Fiber Glass Pontoon construction technique - Joining sections

Discussion in 'Boat Design' started by Michael Hyder, Jun 30, 2020.

  1. fallguy
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    fallguy Senior Member

    Contributions to these threads fast fall to polemics. It is important to remain objective. I can see how a barrel rusting out could be big trouble.
     
  2. KeithO
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    KeithO Senior Member

    Some suggestions are just really inappropriate. Perhaps you heard that the McCandles bus in AK has just recently been removed from the trail where it sat for nearly 70 years ? Turns out that after the book and movie, all sorts of people wanted to make a pilgrimage out to the bus, resulting in multiple deaths and many search and rescue attempts mainly due to the river flooding which was the exact reason McCandles got trapped there in the first place.

    Even if the OP didnt take the advice, who knows how many people may read this thread years from now and some fool will get it in his head to make a raft from steel drums and set in motion something bad. I personally knew of kids who drowned in a pond after making a steel drum raft, usually after initially working great they get all their friends over and then 1 drum fills with water, the thing capsizes/pins someone to the bottom etc... The first thing we did if we found such a contraption on public land was to make sure every drum was so thoroughly ventilated that no-one would ever think of floating it again.
     
  3. KeithO
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    KeithO Senior Member

    An alternate construction method for making long skinny hulls in composite is cylinder molding using scarfed plywood and glass fiber. CYLINDER MOLD MULTIHULL CONSTRUCTION https://www.multihulldesigns.com/pdf/cm/CYLINDER%20MOLD%20MULTIHULL%20CONSTRUCTION.htm

    It is apparently a very fast way to build a composite hull for fast CATs and one of the major plusses is that the formwork for the mold is used to make both sides of the hull. For a CAT you would make 2 port halves for the port and starboard hull, then reverse the forms on the strongback and make 2 starboard sides. On the formwork, glass layups are vacuum bagged to the outside of the surface. Then the cylindrical surfaces are trimmed around the edges to generate the contours for bow and stern (opposite hand for each side of 1 float). Then the keels are stitched together, and a strong epoxy filler containing milled fiber is poured into the keel of each hull and while tacky the inside of the keels is glassed with the sides of the hulls spread apart approximately the right amount. Anyway, refer to illustration below. Ultimately the inside of each hull is glassed, the ribs glassed in place and decks bonded on. All plywood is encapsulated in epoxy and glass to protect it from inadvertent exposure to water. Most of the time, builders are not using marine ply, rather CDX or similar plywood from the DIY store.

    Needless to say, like any composite hull, it has to be painted to protect the epoxy from breakdown from UV. Its probably worth investing in some 2 part paint, even if it is automotive paint instead of "yacht" paint. There would have to be strong points embedded in the hulls for attachment to the deck and protecting the hulls from water entry at any attachment points.

    The problems with this method, like any other composite item would be having a warm enough work environment for the epoxy to be able to flow and cure. You should have the means to maintain at least 70-75F at all times and any material brought in from the outside would need to warm up to the higher temp before trying to do any epoxy work on it. You would need something like an insulated tent or a refrigeration shipping container to work in as well as a 24/7 adequate source of heat. One thing that should shorten your build time is the fact that you would just be trying to get a fair shape, instead of a yacht finish which is probably 80% of the work on a pleasure boat hull.

    [​IMG]
     
  4. fallguy
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    fallguy Senior Member

    maybe so, but none of that justifies obtuse responses a future, uninformed reader won't comprehend; based on your other replies; I think you understand

    be careful about polemics; it can be useless
     
  5. ondarvr
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    ondarvr Senior Member

    Just typed a long and detailed reply, pushed the wrong button and poof.

    I'll try again later
     
  6. fallguy
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    fallguy Senior Member

    Don't you hate that!!&:'sn!!
     
  7. bajansailor
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    bajansailor Marine Surveyor

    Easier said than done I know, but it is probably worthwhile to type up a draft in (eg) a Word document or (even better) an email like Gmail (which automatically saves periodically), epecially if you are anticipating writing a longish post.
    It is still possible I find for Gmail to do weird things, but hopefully you still have the saved draft somewhere.
    I used to do this (re writing a draft copy) often on the old YBW Forum in England (the new Forum now is much better) - the old Forum was notorious for 'timing out' where everything you typed would disappear when you click on 'send'.
     
  8. Michael Hyder
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    Michael Hyder Junior Member

    Valid ideas, KiethO. But i can say in Nome. Steel drums would not be advised. Weather conditions can worsen in a matter of hours, and the last thing you need is a catastropic failure when you are downwind 8 miles and need to get back to harbor in 2 hours. Too dangerous. Plus, I am not sure if Coast Guard will even approve a steel drum vessel.
     
  9. KeithO
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    KeithO Senior Member

    Dont worry, I was 100% against the drum idea from the beginning..... I think you would be surprised how fast a steel plate design could come together. Aluminum would be more expensive, but not need blasting or painting. The welding is a bit more intense because of the need for cleanliness and removal of oxide prior to welding. One needs to avoid drafts and noxious vapors condensing out on the highly conductive plate overnight, for instance. Especially bad if working in a shop that has multiple different activities going on. On the other hand, steel basically needs to be dry and that can be achieved with a bit of preheating with a big propane torch. Pick your poison...
     
  10. gonzo
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    gonzo Senior Member

    Steel doesn't really need to be dry to weld. Otherwise, underwater welding would not be possible. Also, as soon as you strike an arc, any moisture will boil away.
     

  11. gonzo
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    gonzo Senior Member

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