Foam cored flats boat?

Discussion in 'Boatbuilding' started by gotmuddy, Jan 7, 2013.

  1. gotmuddy
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    gotmuddy custom user title

    A friend and I are wanting to build a tunnel hulled flats boat. It will be a one-off build so we figured we could build the core out of foam and fiberglass the outside to give us the hull we want. My friend has built airplane wings in the past doing the same thing and he thinks building the boat like this would be economical and very strong. we are wanting to build it 60" beam and 16-18' long.

    http://www.gulfcoastboats.net/
     
  2. michael pierzga
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    michael pierzga Senior Member

    The problem is ECONOMICAL. Do the math with ply, Glass and epoxy then calculate Foam ,glass, epoxy.

    A logical comprimise is Ply glass hull and lightwieght foam core glass, interior fit out.

    Ask your designer for suggestions .

    The boat you propose is very powerful with a complex hull form . Engineering is required.
     
  3. messabout
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    messabout Senior Member

    Boat bottoms are exposed to a lot more frequent impact loads than an aircraft wing. The impacts are far more severe and localized on a boat, particularly if you are going to use generous power and high speeds.

    If you use foam like Klegecell or other appropriate foam, the build will not be cheap. You will use a lot more glass and resin than you'd need with plywood. If you use cheap foam from Home Depot or a similar source, you will almost surely need to use epoxy resin as opposed to polyester. Epoxy-costs-aplenty.

    Check your sources and prices before you commit to a particular method. A good flats boat can get along nicely without all the sexy looking concave sections on the Texas boats shown in your link. Thus you can build with sheet stock like ply or non scrimmed foam.
     
  4. groper
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    groper Senior Member

    sure its doable... another forum member is building exactly this at the moment. A corecell foam core epoxy laminate flats boat. He is also teaching himself resin infusion at the same time. hmmm.... sounds strangely familiar....

    See here;
    http://www.boatdesign.net/forums/fiberglass-composite-boat-building/infusion-plan-43380.html

    My boat is a big bigger, but same deal... http://www.boatdesign.net/forums/bo...displacement-powercat-build-thread-38588.html

    i infuse foam cored panels and tape them together, its a suitable and efficient method for building any boat if you design it without compound curvature. Compound curvature complicates everything, you need molds or formas and the latter restricts you laminating 1 side at a time. Strip planking is also time consuming and then you still need to laminate both sides and hold everything in alignment whilst your doing so each side.

    I would definately recommend a design that doesnt have compound curvature, simple curvature only - this will make the build so much less time consuming.

    If you have the help of your friend, definately look into resin infusion, if he is into aircraft he will be interested in infusion if he is not already doing it. It makes working with fibreglass and resin so much more enjoyable... if you go this route, you will need nothing more than some simple jigs and ratchet straps to torture the panels into shape whilst you tape them together. They will naturally fair themselves. You should have a flats hull built in pretty short order this way...
     
  5. gotmuddy
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    gotmuddy custom user title

    very neat build, unfortunetly I dont believe I can afford that method, even if it is far superior. I may be looking into plywood for core material.
     
  6. groper
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    groper Senior Member

    The good thing about foam cored methods, is that they are basically identical to plywood build methods. you can do the same thing with tortured ply as you can with foam cored panels and it would also suit a flats boat build very nicely, and a bit more robust for the occational sand bar enounter which is rather inevitable considering the usage... :)
     
  7. Oyster
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    Oyster Senior Member

    Hum, I would never atttempt to skin any foam solely with finish cloth as is done all the time with plywood hulls for any hull slated for an open water planing hull. While a lot of specifics are missing when talking about plywood boats and their scantlings, I don't think your observation has merit.
     
  8. groper
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    groper Senior Member

    I said *methods* not scantlings...
     
  9. Oyster
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    Oyster Senior Member

    Well then let me rephrase my reply. You cannot use 1/4" foam for a boat hull thats been speced out for 1/4" plywood and end up with a sea worthy hull without reengineering your project. While the steps may be the same, that is use a substance and then cover it with some glass, not only will you need to have an entirely different jig form for foam, but you will need an entirely different glass and more of it in most cases. While the actions of glassing a foam hull versus a plywood hull may be the same, the work of the two contrasting types of hull material and layup are not identical, IMO.
     
  10. groper
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    groper Senior Member

    I disagree again, you dont need an entirely different jig form... it can be the same for either build method - you torture the material over the forms (or not use forms at all) and glue and glass the panels together. So the jig can be identical, and you go about building the hull in the same manner... ie the build method is the same.

    If you preglass the foam panels, they have a stiffness similar to plywood and can be tortured over very large frame spacings to get very fair curves and/or twisted developments.

    We already covered the scantlings, i agree the scantlings are different which is a point that is so obvious it need not be mentioned...
     
  11. Oyster
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    Oyster Senior Member

    You cannot suspend sheet foam across the same jig or form that is slated for plywood without sheet or cut paneled foam sagging, because normally the spacing is too wide. This just causes additional work in the fairing stage in particular to get a uniform surface in which to apply a decent topcoat. YOu need additional support. But whatever,,,you can have the last word in this one.
     
  12. fpjeepy05
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    fpjeepy05 Senior Member

    Duratec Styrosafe

    You can use the cheap home depot foam if you want to. I've never done it but I've wanted to. If you put two coats of Duratec's Styrosafe, over polystyrene foam you can then switch to regular polyester resin. The styrosafe creates a barrier so the polyester can't bleed through, and melt the foam. I'm not sure how strong the bonding is, or how much it is. But if it works it sure would cut down on costs.
    Are you planning on cold molding over a jig? I wonder if the styrosafe is strong enough itself to hold the foam strips together just long enough to back all the screws out and get a layer of glass over it. Or for that matter you could probably pull the screws out from the inside if you didn't put washers on them.
     
  13. groper
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    groper Senior Member

    If you bothered to read a little you might learn something... I wrote in an earlier post, if you pre-glass your foam panels, they end up stiffer than plywood and thus can be worked in the same manner as plywood. :rolleyes:

    Here is a hull being tortured into shape using flat sandwich panels (both sides e-glass) being tortured into shape from flat developments, the frames are about 10feet apart for this 40ft hull - try that with plywood and see which one needs a longboard i challenge you...

    [​IMG]

    In fact foam cored panels are a bit more versatile than ply...
    Here is a flat foam cored panel in the process of bending it.

    [​IMG]

    Then to get it right around, a few ratchet straps are needed and viola, the bilge of a 35ft hull is done;

    [​IMG]

    Take it a step further, and you can torture your composite panels around your bulkheads, not needing temporary frames at all because the panels are so stiff, let them naturally fair themselves...

    [​IMG]

    Or you could do it in the same less efficient manner as plywood, using closely spaced framing to form your shapes... foam works either way just as well if you think outside the box and apply appropriate fibres to get the stiffness you need before you work them into your desired shapes... you can even rip composite panels into strips and strip plank it over widely spaced framing for compound curvature if you so desire... the choices are virtually unlimited...

    have you learned anything yet?
     
  14. Oyster
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    Oyster Senior Member

    Yep, sure have, you have a bit of a nasty streak sir, and its of no interest to me to match your wits.

    Your examples are apples to oranges, and its of no concern to me, as with your condescending remarks,, Your response and project has nothing to do with the OP inquiry either. Go grind your axe somewhere else.
     

  15. michael pierzga
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    michael pierzga Senior Member

    To the OP , by all means purchase some foam core then use it to lighten up the furniture components on your boat. Working with the foam will give you good experience for future projects.
    When foam is used for furniture its much easier to get the engineering right and much cheaper when you get it wrong and have to scrap the steering console or seating arangement.

    A foam core cooler, seat is a great detail, also Live bait well....foredeck....
     
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