Stitch & glue outrigger to glass inside or not?

Discussion in 'Multihulls' started by erikhaha, Jun 12, 2010.

  1. erikhaha
    Joined: Sep 2007
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    erikhaha Junior Member

    So this is my 1st build. I am building a 20ft tri, based on the Ulua main hull from Gary Deirkings book. I increased the overall dimensions by a factor of 1.12 therefore increasing the total displacement. The main hull was stripped using 1/4" thick strips of DF clear then glassed outside w/ 2 layers of 7.5 oz glass and 1 layer inside. The main hull is about 90% complete and currently I am working on the outriggers.

    The outriggers are 16ft in length, and am building them using 1/4" thk marine ply stitch & glue. The outrigger shape is an isosceles triangle, with the sides having a length of 16", please refer to the attached photos.

    My question to some of the more experienced builders is should I fiberglass the inside of the outriggers even though they will be sealed?

    I realize that doing so will increase the strength as well as water resistance, but I just want to verify if it should be done,and or others experiences with outriggers that have not been glasses inside.

    Thanks in advance. I have posted here in the past, about a year ago, but due to getting married and buying a house and studying for my PE license I have had little time to work on her.

    Erik
     

    Attached Files:

  2. apex1

    apex1 Guest

    You must not glass the inside. Apply three layers of neat epoxy to seal the wood completely, thats it. And do it in one go, when the first layer kicked, apply the next. Once fully cured the next layer would´nt stick without sanding.

    Regards
    Richard
     
  3. hoytedow
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    hoytedow Old Woodbutcher

    I wouldn't glass the inside either, but I would use a copper solution any where water might reach wood, applying before sealing with epoxy.
     
  4. Doug Lord
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    Doug Lord Flight Ready

    Richard/ Hoyt, just out of curiosity, why wouldn't you glass the inside?
     
  5. DrCraze
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    DrCraze Junior Member

    As far as know canoes are dry boats. Why the copper? Its not as if he plans on renting a slip for an outrigger. Or are you simply trying to impress apex with your knowledge:p
     
  6. Chris Ostlind

    Chris Ostlind Previous Member

    There's all kinds of opinions. One should carefully consider the experiences of those that make the comments with boats of this type before running off on a tangent at their direction.

    Gary knows what works for his boats and you'd be wise to follow his instructions and let the rest of this stuff go flowing past your attention span.
     
  7. erikhaha
    Joined: Sep 2007
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    erikhaha Junior Member

    Apex why shouldn't I glass the inside? I thought that I should glass the inside, even though I didn't want to, which is why I posted this. I hoped that someone would tell me that it isn't necessary and give me reasons against it. What is your reasoning for not glassing the inside?
     
  8. apex1

    apex1 Guest

    Weight saving what else?

    Though if the design was calculated with a glass layer for additional strength, then of course you should not skimp on that. But that was not mentioned.
    For just protecting the wooden structure the neat epoxy is a perfect and relatively lightweight solution. And no additional effort is necessary.

    The "opinions" are nothing but expertise in wood epoxy building, to comment on that dumb side blow. What is valid for the protection of one wooden structure in marine environment is as valid for another, using similar material.

    Regards
    Richard
     
  9. hoytedow
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    hoytedow Old Woodbutcher

    I never glassed any of the insides of the boats I built. It saved weight. I did use copper solution which kept the wood from rotting as it was exposed to rainwater from time to time. Dr. Craze, why the rude comment/question? I was just sharing my personal experience. If you want to fight, join the marines of any country except Costa Rica.
     
  10. erikhaha
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    erikhaha Junior Member

    Apex and Hoytedaw, no offense but do you know that I am asking questions about an outrigger for a small trimaran and not the main hull?
    Do not take this as being rude I would just like to know if you have experience with multihulls, in particular outriggers for a small daysailing trimaran.
     
    1 person likes this.
  11. Chris Ostlind

    Chris Ostlind Previous Member

    When building a pure stitch and glue ama, as suggested, it all comes down to the integrity of the shell and its seams. Chines can be high wear points, especially the simple triangular shapes you are using. If this were one of my designs, I'd be glassing the entire exterior of the ama, adding a wear strip of a minimum, 6 oz. 4" glass tape on the keel seam and giving the interior of that same seam a run of 6 oz. 4" glass tape... minimum. If your use intentions run toward the extended coastal cruising adventure style of sailing/paddling, then consider the places where you might be taking the boat to shore. Light layups are good for day sailing, but hard use journeys may require that you toughen-up the seams for the eventualities.

    Having the seam taped on both sides will guard against ama failure at that point due to hard landings, repetitive handling on abrasive shores and an accidental dropping of the ama when assembling the boat at the launch ramp. For a 6mm marine ply build for an ama of this length, you would probably not need to do more than tape the seam internally as a day sailing boat.

    Again, check with Gary. He knows his boats well and has probably already had to deal with the optimal layup concerns from the many builders he has for this model.
     
  12. hoytedow
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    hoytedow Old Woodbutcher

    My first boat was a multi-hull and my remarks were mainly intended to suggest a way to make your ama last longer. Rainwater or other fresh water encourage rot. The final solution will come from you as your best local expert.

    http://www.boatdesign.net/forums/sailboats/small-trimaran-ama-design-32966-2.html
     
  13. hoytedow
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    hoytedow Old Woodbutcher

    Chris mentioned internal taping at major impact points. Good advice.
     
  14. DrCraze
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    DrCraze Junior Member

    The benefit of glassing the inside is impact resistance and added stiffness. If you don't glass the inside you'll lose peace of mind but probably nothing else since it is plywood and not strip planked. You could glass tape the keel seam on the inside for peace of mind.
    Your amas look just like the main hull of Ulua. I think I see what you are up to. You might need to make your aka's a little more beefy than the original design since one of your ama's have enough displacement for the whole craft.
    One question....Why a trimaran? It would be better at breaking through the surf in an outrigger configuration and quicker to build. I have to admit I'm a proa guy myself so I am a little biased.

    Looks like Chris beat me to it:p
     

  15. erikhaha
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    erikhaha Junior Member

    Hoytedow, thanks for the advice, I now see what the situation is. I assumed that I had to fully glass the inside, because upon begining the building of the main hull, which is stripped I researched how to build using that method and everyone said to glass outside as well as inside. But for the outriggers since I am building them stitch & glue method the ply is already one piece, therefore I should only have to waterproof the inside.

    Now as Chris suggested I will be glassing all of the interior seams for added strength and stiffness.

    Dr Craze, I started off intending to build a proa, but as I did more research I changed the design to a tri. At this time the main hull was almost complete, as far as stripping and glassing the outside, so as far as design changes I just had to strengthen her at points of additional stresses.

    In the attached pictures you can see one of the support bulkhead for the aka, or cross beams for the outriggers. For those I also had to come up with a different design then Gary has suggested in his book. I will be using either a (3-1/2" or 4") dia x 1/8" wall aluminum tubing for both beams. I have calculated the required section properties for the aka's based on a sial area of 120s.f. in a 15 knot wind. Although I simplified the analysis I believe that the sizes that I am getting are proportional to the displacements of the hulls.

    Attached are a few pics of the main hull and the outrigger for comparison . It was a little hard to get a good shot of both but I think you can get an idea.

    Thanks a lot guys for your advice.
     

    Attached Files:

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