alternative plywood types for stitch and glue

Discussion in 'Wooden Boat Building and Restoration' started by stubbymon, Aug 20, 2016.

  1. stubbymon
    Joined: Aug 2016
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    stubbymon Junior Member

    Always trying to save money, aren't we all. What about Plytanium ply or even just t 1-11. I'm not trying to build for eternity, 10 years before any real rot would be fine. Any takers?
     
  2. gonzo
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    gonzo Senior Member

    Those are either rough sawn or beaded; both a rather bad idea. Use exterior grade. If you go through the pile, there are usually a few good ones. I have done it many times.
     
  3. PAR
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    PAR Yacht Designer/Builder

    Welcome to the forum.

    T1-11 is a good quality construction grade, but as Gonzo mentions, the good face has a rough cut veneer. It can be had without the grooves, but again the quality and veneer count are quite low. T1-11 use to be made to the PS1-95 standard (marine), but since the recent terminology changes (a few years back) T1-11 is now an exterior sheet, not marine, which is a damn shame, because I use to use it a lot. The same is true of MDO, which has suffered the same fate.

    Plytanium ply is an "Exposure 1" grade and not suitable for boats. It does use a WBP glue, but its construction is very poor, many defects, few veneers, etc. Exposure 1 grades are designed to be covered with something relatively quickly (house wrap, vinyl siding, tin, tile, etc.). If left exposed to the elements, it does break down pretty quickly.

    If you must use construction grades of plywood, make sure the label or stamp says "Exterior" only, with no mentioning of Exposure 1.

    FWIW . . .
     
  4. tom28571
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    tom28571 Senior Member

    T1-11 is maybe the worse plywood to build a boat of. Its barely good enough for vertical siding on a house with a limited life expectancy. Nothing less than exterior grade ply should even be considered to put any labor or money into.
     
  5. PAR
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    PAR Yacht Designer/Builder

    T1-11 is an exterior grade and built to the former PS1-95 standard, which is now modified to include a letter grade system. Marine grades are PS1-95 grade A-A, A-B and B-B, all Douglas fir construction, with B or better internal veneers and various defect and repair allowances. A typical T1-11 sheet will be a C-D or B-C sheet. It can be ordered without the grooves and with a better good face, but this isn't very common to see.

    All this said, it is the lowest form of suitable material you can use on a boat, that still has a WBP adhesive. I would be very selective about its use, which would be above the bilge and internally only.
     
  6. SamSam
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    SamSam Senior Member

    It would help if you gave even a dim clue as to what you want to build. Plytanium or T 1-11 could work, or not, depending on what you want to build. Plytanium or T 1-11 could work, or not, depending on the conditions the boat is subjected to. Plytanium or T 1-11 could work, or not, depending on other variables. It's hard to say whether Plytanium or T 1-11 would work, or not, it just depends.
     
  7. PAR
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    PAR Yacht Designer/Builder

    Plytanium will not work for hull planking nor heavily loaded bulkheads. T1-11 can work, if really cheap and not especially long lived is desired. 10 years isn't much to ask and you can use bathroom tissue for planking, given enough epoxy and fabric, but the "goo factor" goes up dramatically, which kills the inexpensive portion of the problem.

    The cheapest way to go is APA, AB or BB sheets with exterior plywood used internally. This can last without a full sheathing, just taped seams for 10 years. You'll have some repairs, but any boat that sees reasonable use will also. You can go cheaper using an "exterior" sheet, but if a powerboat that's blasting around in some chop, it will not last long.

    Current pricing for 1/4" BB marine is about $39 from Menards (who's usually higher than most, but a good retail gauge). A meranti Aquatek sheet, which is built to the much better BS-6566 standard is about $50, although it's not as commonly available. Hydrotek is built to the BS-1088 standard (much, much better than PS1-95) and this is about $55% bucks per sheet.

    So, let's take a small boat that needs 10 sheets of 1/4" plywood. You can spend $399 on BB marine at the local big box store, if they will bother to order it for you. This plywood will be Douglas fir, which checks like crazy and only 3 veneers, so quite weak. On the other hand, you can get some Aquatek at $500 bucks or Hydrotek at $550 and in the big picture the most you'll save is $150 bucks, which you'll easily spend on fabrics and goo, trying to control the cheaper Douglas fir from checking. Simply put, yeah you can find places to save money, but generally the planking is some of the best stock on the boat, for some obvious and others not so much, reasons. If $150 bucks kills the deal for this hypothetical boat build, you need to consider building tool sheds instead. You'll spend $150 on painting it alone, once you count up rollers, brushes, thinners, paint, primer, masking tape, etc.
     
  8. tane
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    tane Junior Member

    "...10 years before any real rot would be fine..."
    you'd be surprised...
     
  9. Green65
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    Green65 New Member

  10. messabout
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    messabout Senior Member

    Check the weight of the Plytanium panels against the weight of the several other plywood options. Pine is generally heavier than fir and much heavier than some of the more exotics like Meranti or Ocumee.
     
  11. JamesG123
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    JamesG123 Senior Member

    Chipboard? :confused:
     
  12. Green65
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    Green65 New Member

    So, I did look up the weight per cu. ft of a variety of wood types. For a few, I needed to take an average of weights (SYP can be made up of 4 different trees).

    SYP 38lbs
    Meranti 36lbs
    Okoume 27lbs
    Fir, Douglas 32lbs
    Birch, Baltic (Finland, Baltic, Russian) 40lbs
    Ash, Green/White 41lbs
    Oak, White 47lbs

    The Birch has the highest Modulus of Rupture at 17,700 lbf/in2 and Okoume the lowest at 10,900 lbf/in2. About a 40% difference in strength.

    This has been an interesting exercise, but has not really helped to make up my mind. Wish I was made of money...luckily, it will be a while before I need to decide.
     

  13. messabout
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    messabout Senior Member

    Consider that even a small boat will require that you spend many hours to build it. You will have an investment in sweat, passion, and skinned knuckles that transcends differences in the cost of materials. If you use....say 10 sheets of ply that cost $30 or alternatively you might use ten sheets at $60 for a far better and more pleasingly workable material. Sure enough you might have saved three hundred dollars. You may have traded the three hundred dollars for an inferior finished product. A ten sheet boat would sure enough take you weeks and weeks of labor and you have opted for a questionable quality material. Does that really make sense?
     
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