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Thread: Plywood Catamarans

  1. #41
    Join Date
    Jul 2011
    Location
    lac magog, sherbrooke city, quebec
    Posts
    28

    Default Re: Plywood Catamarans

    I have been busy with work and neglected to develop on my catamaran project.
    But the ease of repair of ply/epoxy has been a major factor. I have looked at in some extent used carbon fiber products. A high tech product and a there are ways to reduce the cost and even increase performance with combos with glass. Not 100% happy with the brittleness.
    But at the end of the day, wood products and in combo with glass, carbon and other (looking at innegra) can be my final choice. Nanno wood products are about to come out, some say it will make paper as strong as steel, are we ready for a cardboard cat ?
    One added subject can be the finishes. I just can't silent the fact that the increasingly popular vinyl films they use for changing the color of cars is catching my interest. (check it out on youtube) Ease of application, cost, colors (how cool would a chrome cat hull be with 3dcarbon stripes ) . This is only for above the water line (would say about 12 inches above) although my stickers still hold on after 7 years of outdoor beating in freshwater.
    My first choice was Alexseal paint system, and will certainly use it likely in combo with those vinyl.
    They say 5 years, but with a protective tarp (we will be mostly at anchor/mooring or marina) should make it last longer. For interior finishes the 3d carbons are making a killing with the wife and friends. I figure a lag time might be necessary for the evacuation of the gases from vinyl (pvc) products (has been an issue for shower curtains).
    Getting motivated to chrome a Nacra ...
    On the large cat, i am considering a double skin under the water line, this skin would be part of the raft tubes, so if damage occurs to the hull, it is quick and easy to replace, the raft tubes being identical to the hull section, hence repair afterward for reuse for the raft. (the raft is the activity floating platform sitting under the tramp, 32 ft long x width of the tramp) . Can be done with ply/epo or glass/carbon/corecell and a tramp also. Just got to have space for blowing those huge kites ...
    cheers

  2. #42
    Join Date
    Jul 2011
    Location
    lac magog, sherbrooke city, quebec
    Posts
    28

    Default Re: Plywood Catamarans

    i am looking for chinese or other emerging market marine ply, do anyone have some good references ? I have a group of contractors who would buy the balance of a container if the supplier can offer 1/2 in up to 3/4 in plys, this will be for balconies covered with fiberglass. I plan tu use 1/8 in 4 ft x 4 ft plys, BS stamped .
    Thank you

  3. #43
    Join Date
    Sep 2010
    Location
    Tampa Florida
    Posts
    888

    Default Re: Plywood Catamarans

    good luck with all that lol

  4. #44
    Join Date
    Oct 2010
    Location
    east coast uk
    Posts
    225

    Default Re: Plywood Catamarans

    Quote Originally Posted by mikecat View Post
    i am looking for chinese or other emerging market marine ply, do anyone have some good references ? I have a group of contractors who would buy the balance of a container if the supplier can offer 1/2 in up to 3/4 in plys, this will be for balconies covered with fiberglass. I plan tu use 1/8 in 4 ft x 4 ft plys, BS stamped .
    Thank you

    hmmm all I can say on this is be very very very careful

    I used Ear Eastern BS stamped 9mm ply and I had 4 sheets with virtually no glue inbetween some laminates. it delaminated on cutting
    also they role the lumps and bumps flat.if you cut through on, it expands again and makes a decent join nigh on impossible without sanding away a layer or two.I understand that good quality stuff (Lloyds approved) does not
    I am know wishing I had spent the extra for realy good quality ply, but on the upside, it is easy to replace

    Kim
    just a scared rabbit in the headlights of life

  5. #45
    Join Date
    Nov 2008
    Location
    Santa Barbara, Calif.
    Posts
    539

    Default Re: Plywood Catamarans

    I have had the same experience as Kim with Malaysian "marine" ply. Delaminated when cut. Interestingly, I left some scrap birch ply in the cockpit along with the Malaysian marine ply for a week in the rain. The Malaysian stuff virtually exploded when it got wet, the birch ply grew mushrooms but held together. I have found excellent marine ply in Thailand, but it is very heavy. Sourcing from abroad would be very risky as you cannot test the ply before shipment. I would think you would be able to source much lighter, better quality and probably cheaper ply at home in Quebec than taking a chance with foreign stuff. You will put so much labor into your cat, it would be a shame for it to turn out shoddy for the sake of a few dollars in ply.

    Mike

  6. #46

    Default Re: Plywood Catamarans

    I have a plywood vessel and I have to say that most of it is fine--but it is essential in any plywood craft to never enclose a space and to have forced ventilation in under sole areas and crossbeams. On a wooden vessel in the tropics enclosed spaces are rot factories. It is possible to completely saturate with epoxy but add that to the now expensive plywood--it is no longer cheap--and alternative materials become viable. If any water ever gets in the damage spreads very quickly under the epoxy skin--and if it is not gas-tight water will get in through air going in and out through expansion and contraction. Saturation by epoxy s good as long as the thin skin of saturated timber is not damaged or some idiot has not drilled or sawed through it while adding something quaint to the hull. I have spent a bundle rectifying mistakes in both design flaws which allow water to collect and in subsequent damage caused by rot. I have got rid of it all at last--and now use forced ventilation and inspection ports to all such areas and to allow for the placement of fungicides, salt etc.

    Plywood is wonderful stuff--but by the time one has added all the expensive epoxies and paints and stainless scantlings and fittings and solved all of the problems of edge-saturation it might have been better to use alloy or some kind of resin/glass construction. I will not be building a plywood cruising catamaran, and my next tub will not be wooden. Had I bought a glass boat I would not be reduced to a value of about 30% of what I spent on it together with what I paid for it--which seemed reasonable at the time. Now I pass on all of this to a new owner, or I keep her and put up with a vessel too large for the two of us.

    Foam sandwich or solid glass vinyl ester or epoxy would be my choice. Plywood leads to rot problems eventually, and it is freshwater ingress, either from condensation or rainwater, that does the damage.


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    Last edited by Mike Banks; 27th March 2013 at 12:11 AM.

  7. #47
    Join Date
    Sep 2010
    Location
    Tampa Florida
    Posts
    888

    Default Re: Plywood Catamarans

    Quote Originally Posted by kim s View Post
    hmmm all I can say on this is be very very very careful

    I used Ear Eastern BS stamped 9mm ply and I had 4 sheets with virtually no glue inbetween some laminates. it delaminated on cutting
    also they role the lumps and bumps flat.if you cut through on, it expands again and makes a decent join nigh on impossible without sanding away a layer or two.I understand that good quality stuff (Lloyds approved) does not
    I am know wishing I had spent the extra for realy good quality ply, but on the upside, it is easy to replace

    Kim
    Chinese Plywood is SHIT labeled BS (The BS is for bull shit)

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