How big a boat can built with glued lap construction ?

Discussion in 'Boat Design' started by PeterSibley, Feb 10, 2011.

  1. PeterSibley
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    PeterSibley Junior Member

    I contacted my local supplier ,''Bote Cote ''and he was adamant that his product had been formulated for use with ACQ ...I'll have to ask him about other chemical treatments .LOS and such .
     
  2. PeterSibley
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    PeterSibley Junior Member

    Now that's interesting ,I posted a reply it appeared then disappeared ....

    PAR ,yes agreed but I rang my local epoxy supplier ,Bote Cote . I assured me that his epoxy was completely compatible with ACQ .I'll have to ask about other preservative chemicals .

    and now it's back ,maybe it was just hiding over the page ? :eek:
     
  3. PAR
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    PAR Yacht Designer/Builder

    My understanding from Australia clients and friends is your pressure treatment chemicals are still CCA, though this is expected to change (like we just did). Personally, I don't see the need for treated plywood if it's encapsulated in epoxy. I've also found that most treated plywood (at least in the USA) is some of the crappiest stuff available. It's usually very wet with the treatment, the panel construction is poor with overlapping veneers, lots of voids, repairs, etc. and it's generally only acceptable for use on someone's house. Now, this may not be the case in your country. We can get good quality pressure treated plywood, but it's more costly then the finest marine grades. Unless it was a work boat, I wouldn't use pressure treated anything on a boat you'd live in for any length of time.
     
  4. PeterSibley
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    PeterSibley Junior Member

    Good points PAR ,I'll be at the factory on Monday to pick up one sheet of 15mm for another job .I'll be ripping it up so will be very interested to have a good look for voids and overlaying veneers .I'm well aware of the various problems ply can present , I've used a lot of the stuff .Rot is one of the big ones however .I know ventilation is the answer and I am very careful ....however there always seems to be some part of a boat ...behind fitout ,somewhere where the damp stagnates that is hard to open .This time I'm interested in stopping it before it starts !

    I haven't been able to find the first grade marine I'd like in ACQ ,it just isn't available here .All the ply I've looked at and am willing to use is hoop pine plantation timber .It's a sustainable produced material .I'm not will to use some exotic African grown timber in my ply .I like to know where my timber comes from and it's impact on the world .I know nothing about the logging in Africa .

    I'd rather use a lesser grading and repair as required .

    The CCA ....I'm assuming a few coats of paint will isolate the living space from the stuff .Am I right ?
     
  5. PAR
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    PAR Yacht Designer/Builder

    Gaboon is available down there as is Meranti, both quite good.

    If you're going to encapsulate the plywood, ventilation isn't as big an issue, nor is rot. If on the other hand you treat plywood as if it's timber, then yes, it'll rot under the same circumstances.

    I have a number of clients down there and using epoxy encapsulation methods they have good results with hoop pine too, though most are also aware of the possibility of issue with it. Have you talked to the folks over a DuckFlats?
     
  6. PeterSibley
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    PeterSibley Junior Member

    I haven't spoken to Duck Flats ,they are a VERY long way from here .
     
  7. PeterSibley
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    PeterSibley Junior Member

    Par ,Bataan , what are the usual choices for laminated backbones .I know fir is popular but it's very expensive here .
     
  8. BATAAN
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    BATAAN Senior Member

    Can you find Fir building timbers that are warped, checked and/or split? This often makes them cheaper yet can be cut into good lams with a little work. Of course Kauri or Huon pine are the preferred Aus woods, but seem unobtainable these days. Can you find some salvaged building timbers to be cut up into lams? Building demolishers often have good stocks of nice old wood.
     
  9. PeterSibley
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    PeterSibley Junior Member

    There is some good fir occasionally , usually about $2500 per cubic metre for anything worth buying .It's pretty rare .I'm thinking about just milling some of the local softer ,glueable eucalypts ...and yes ,I do know the right ones ! We have one here that is just a bit heavier than fir ...I think I'll run a few bending and glueing tests .
     
  10. ancient kayaker
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    ancient kayaker aka Terry Haines

    $2,500 per m^3 = US$5.97 per board-foot

    FWIIW
     
  11. PeterSibley
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    PeterSibley Junior Member

    How does does that compare to your prices ?
     
  12. BATAAN
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    BATAAN Senior Member

    The Gougeon brothers have some interesting observations about testing, are very much for it, and give techniques in their books.
    You might try a thin test section with a lot of bend, totally saturated and coated, and boil it, and see how long it lasts. Your boat won't be boiled, hopefully, and this would be an interesting test.
    Another would be to make another thin test frame section, fairly long, grip it in a vise with a long cantilever and hang more and more weight on it until it's bending a lot, then wrap it in wet rags with a steady drip on it and see if it sags more in a few days.
    Both these would tell you if you were getting water penetration in your chosen timber. I have always found keeping the laminations thin make things work for me when I did frames and such with oak.
    But I did repairs, not much new building, and that was years ago so I am out of touch. Covey Island Boat Works has the laminated building methods quite well thought out and practiced.
    Check them out here to see build of FARFARER, hot fusion schooner to ultra-cool Nigel Irens design.
    http://www.coveyisland.com/projects.php?display=02
    On this page go to lower right, to 'view gallery from construction to sea trials' to see photos of how these guys do it after doing it so many times. This may answer a lot of your questions about modern glue/wood construction.
    Good clear kiln dry fir in long lengths here in the Pacific NW where it grows is often $7.00 US per Bd ft. This is one reason we use Larch often for planking, @ $3.00 bd ft.
    Wild ball park estimates probably having little in common with reality:
    Keel 4x12x20' = 80 bd ft + stem and stern so double that + 20% =roughly 200 bd ft @ $5.97=$1,194 if $5.97 per bd ft timber is all usable, perfect (LOL) so $1,400 for the wood and half that in glue etc = $2000 materials for a laminated backbone, continuous, LBP end to end. If too little timber, add 20% for $2400, still not bad for the long life and low maintenance and required long-time haulout capability. And that is fir. Your tests and research may come up with something better and cheaper locally.
    BERTIE was $15000 for hull and deck, about 15 tons or $1000 per ton. If you can build 7 ton MM to the same state for $7000 materials, it doesn't get much cheaper, even in timber and fish boat build like B.
    That flattish bow above the waterline will be heeled and pounding for days on end sometimes.
    Had to do big repair on William Garden designed, laminated African Mahogany 1960's ocean racer RAMPAGE, about 50 foot LOA. Her 4 layers of Resorcinol glued 3/8" were fractured from the mast to the bow at and above the waterline because the designer used longitudinal stringers at too great a spacing, about 36", and few if any frames.
    Falling off all those waves on that flattish surface just worked it so much it broke all the lams.
     
  13. PeterSibley
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    PeterSibley Junior Member

    That was a good price comparison Bataan ...it makes the used fir i can get cheap enough but I can't get enough to use the same through out so I'll experiment with local timbers .

    We have one here called rose gum ,( eucalyptus grandis) , the regrowth is good ,about the same durability as fir , possibly slightly better , it doesn't bend quite as well ,but pretty close and glues well .

    I can buy standing trees and have them sawn by a mobile mill and get a lot of good and reasonably priced timber .I'll saw to 1'' and air dry for a year .That should be OK .
     
  14. BATAAN
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    BATAAN Senior Member

    Local woods from a local mill are often best. They are almost always the cheapest, and you can personally bargain with the sawyer to get just what you want.
    BERTIE's wood came from a small mill in Oregon several hundred miles away, but his price was right, and I loved it when the overloaded mill truck would arrive and I'd have new piles of fragrant Port Orford cedar and Doug fir.
    Rose Gum sounds interesting. The ability to glue well is probably most important, as even much less durable woods work well when thoroughly isolated from moisture changes with proper, thorough use of epoxy.
    One inch per year is the old rule for air drying.
     

  15. PeterSibley
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    PeterSibley Junior Member

    I've been wandering around my property , I live up in the hills on the North Coast of NSW Oz on a 20 acre block, a wet ,very hilly area .I've found 3 trees that I planted 27 years ago .They will give me all the timber I need for a hull .I have some lovely sticks of pine that will give me my spars .It's looking good .

    I bought a sheet of 15mm ACQ ply yesterday for another project , I'll slice it up and get an idea of the quality . I will use either 17mm or 19mm for the boat .

    Yep ,small local mills are the best , they know where their trees come from and are usually keen to keep the place alive for their children .
     
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