white fiberglass sheets from Home Depot?

Discussion in 'Boatbuilding' started by mmelnick, Aug 20, 2010.

  1. mmelnick
    Joined: Jul 2010
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    mmelnick Junior Member

    I've been researching for a few months and I plan on building a 16-18 foot pirogue kanoe this winter.

    I was looking at doing a plywood stitch and glue boat, but today I saw sheets of white fiberglass panels for $15 at Home Depot.

    Can these be used for building a small boat? Or will I run into problems. It seems like they are more flexible than 1/4" luan, and would already be water proof.
     
  2. apex1

    apex1 Guest

    No, you cannot use them. They are not strong enough. Ply is much stronger.

    Regards
    Richard
     
  3. CatBuilder

    CatBuilder Previous Member

    I will second Apex1's advice. I'm very familiar with these sheets, having used them as headliner material in the past.

    The sheets have the following problems:

    *They have too low tensile strength compared with ply
    *Ditto on bending strength
    *You'll have trouble wiring them together because they are brittle and crack apart easily

    Use the ply...
     
  4. mcollins07
    Joined: Jan 2006
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    mcollins07 Senior Member

    What about using them to create a female mold that becomes the outer shell of the boat? What about cutting the panels from these fiberglass sheets, using duct tape on the outside to hold them together and provide the form, then use vaccum resin infussion to build a strong fiberglass layer inside the shell?


    This is just an idea, I have not tried anything like this.
     
  5. mmelnick
    Joined: Jul 2010
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    mmelnick Junior Member

    Gotcha, thanks.

    I was thinking of doing a stronger wooden frame to get around the flexibility and tensile strength, but if it's brittle that would be a whole different story.
     
  6. apex1

    apex1 Guest

    Not to be offensive, but that is quite obvious!

    He goes to build a S&G boat! For what should he waste his time and money on a mould?

    And even for that application the sheets are a very poor choice, much too wobbly, brittle and instable.
    There is no application in boatbuilding where one could use them (as far as I am aware of).

    Regards
    Richard
     
  7. mmelnick
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    mmelnick Junior Member

    Yeah, a vacuum mold would probably be a little more than I'm wanting to do. And the fiberglass sheets are about the same price as 1/4" luan anyway. And the luan there is a 3 ply with 3 layers of the same thickness, not the stuff with the really thin veneers. So I think I'll stick with that and then just seal it.

    Thanks for all the input guys! (and for putting up with my dumb questions)
     
  8. hoytedow
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    hoytedow Wood Butcher

    Home Depot lauan will probably disappoint you. It has voids which will cause you problems if water gets into the wood, and it will. Check for marine grade or try wood strip canoe are my 2 cents' worth.
     
  9. mmelnick
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    mmelnick Junior Member

    Not a single sheet of the luan has an area on the edges where you can see that there was a void. Do you still think that there are voides in the middle?

    I can't get marine grade plywood where I live, and the only lumber yards can only order me 8 sheets or more. And to get it online would be cost prohibitive due to shipping.
     
  10. hoytedow
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    hoytedow Wood Butcher

    My first build was regular exterior 1/4" fir plywood, not marine. Check glue type for waterproofness. It is only a piroque, not ocean going. Sometimes you make do with what you have. Have fun and good luck. Just be prepared for some bulges or wrinkles in the hull. That won't mean it is unusable, just mostly cosmetic blemishes.
     
  11. mmelnick
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    mmelnick Junior Member

    Good to know, thanks.

    I can get the 1/4" luan for around $10 a sheet, or a 1/4" exterior grade birch for about $25 a sheet. But the luan bends nicely, and the birch seems like it wants to crack when I try to bend it. Maybe I'll use birch for the bottom of the boat and the transom (if I have one) and luan for the rest of the hull.
     
  12. apex1

    apex1 Guest

    DonĀ“t use birch!

    The sugar content in the birch wood lets it deteriorate fast in marine environment.

    Lauan (not Luan) is a well proven boatbuilding wood (a variety of Shorea species).
    BUT
    What they sell you in the US is as much Lauan as it is "Christmas tree".
    Most commonly it is just any sort of tropical hardwood timber of unknown species and properties! Just the outer veneers are either some Shorea or similar looking!!! wood.

    The technical properties of such ply are as reliable as the wheather forecast for next month. But that is as valid for almost ALL the ply sold in the US, except those with a stamp of approval from classification bodies like GL. (Bruynzeel)

    Anyway, you can use that lauan ply cr@p. And it will be the better choice than outdoor ply made from coniferous timber. Because it bends nice and is not as brittle.

    But you MUST encapsulate it in Epoxy all sides, and you MUST sheath the entire structure in glass Epoxy.

    Do not skimp on paint after sheathing! Put at least 4 coats on the insides. Outsides are not as important on a boat hauled after every day of useage, but the standing water inside lets them rot away soon.

    Regards
    Richard
     
  13. tinhorn
    Joined: Jan 2008
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    tinhorn Senior Member

    Clever. But if the panels at mmelnick's Home Depot are the same as the ones at my Home Depot, they have a pattern showing on both sides of the panel. A female mold could be built with Abitibi (whiteboard), though, which would provide a smooth outside surface. The cheap luan could be used as a backer where the Abitibi might want to bow or warp. I've used contact cement to glue Abitibi to plywood for just this purpose--no nail holes.
     
  14. hoytedow
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    hoytedow Wood Butcher

    Yes, it is lauan, which I knew but mis-typed. Post corrected. Thanks. In storage it will last longer if inverted.
     

  15. mmelnick
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    mmelnick Junior Member

    I was planning on doing the stitch and glue with laminating epoxy, then covering it with exterior grade oil based paint.

    What is glass epoxy though?
     
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