Epoxy only on inside?

Discussion in 'Strippers, Stitch-n-Glue, and Other Wood Composite' started by ravfirefighter, Jun 28, 2017.

  1. ravfirefighter

    ravfirefighter New Member

    Hi,

    I'm doing some repair work on a strip canoe that required removing all of the original fiberglass on the inside of the hull. I'm wondering if it is okay to just apply epoxy to the inside and not add the extra weight of the cloth.

    Thanks in advance for your thoughts on this.

    Howard
     
  2. Rob Stevens

    Rob Stevens Wooden Canoes are in the Blood

    No. The structural strength in a strip built canoe comes from the sandwich effect aka monocoque construction. I assume you want to trim some weight. You may have done that already by removing the original fibreglass and epoxy, which may have been "renewed" with additional coats. And it's a stripper, so most likely lighter than most other canoes anyway.
     
  3. Todd Bradshaw

    Todd Bradshaw Sailmaker

    As a matter of fact, the inside fiberglass layers on a stripper are actually a lot more important in keeping the boat from breaking in use than the outside layers are. Forces from outside (rocks, waves, beaches and simply the weight of the occupants pushing the hull down into the water) will be pushing upward on the canoe's bottom with pretty substantial force. The outside fiberglass layers are put in compression when this happens, and they aren't in a position to resist these upward forces very well. It is the inside glass layers, which are being put in tension, that are providing most of the hull's strength in those situations. Fiberglass does tension pretty well as long as there is enough of it.

    One of the biggest rookie strip builder mistakes we see is a new builder thinking he wants to shave some weight off of his canoe, so he reduces the amount of cloth used in the inside of the boat. These are often followed by "My new canoe's bottom split open. What do I do to fix it?" threads.
     
  4. OP
    OP
    ravfirefighter

    ravfirefighter New Member

    Thanks for your responses. I learned a lot from both posts. I never knew that the method of sandwiching the wood between fiberglass had the special name monocoque construction. Plus I didn't know that bit about the compression issue. I'm not exactly a novice at building strip canoes (I've made 6) but boy there is sure a lot I still don't know about the process.

    Howard
     
  5. Dan Lindberg

    Dan Lindberg Rotten Wood Hoarder

    As for the strength thing, do you remember how floppy the hulls were when you removed them from the form? Those are hulls without glass on the inside.

    Dan


     
  6. Scott Rowe

    Scott Rowe Random Adventurer

    Adirondack Guideboat Co. out of Ferrisburg Vt. uses glass cloth on the outside and just epoxy on the inside of their cedar stripped hulls, BUT...the inside has ribs! You might be able to add laminated ribs for strength and just epoxy? Just a thought. But then would you save any weight?
     

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