Framing a small boat

Discussion in 'Boatbuilding' started by Damian3716, Aug 31, 2016.

  1. Damian3716
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    Damian3716 Junior Member

    Guys...I already know this is a stupid question... But, cam you use marine ply, laminated to the required thickness, for gaming a small boat?
     
  2. rasorinc
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    rasorinc Senior Member

    Ply is not used as frames do to its flexibility. lamination removes (3 layers) removes most all flexibility and for a small boat, not heavy, low HP it would not be a problem,
    Why??? a lot more work, and more money using epoxy and all.
     
  3. PAR
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    PAR Yacht Designer/Builder

    What design are you building? Small boats don't need frames with certain build types, saving the bother of buying, cutting and installing them. Changing build materials, needs to be done carefully, to match modulus and other considerations.
     
  4. Damian3716
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    Damian3716 Junior Member

    I am looking at the Glen L squirt. I'm in the UK and we seem to be so limited when it comes to affordable hard woods ( in my limited experience). Was just trying to think of ways around it to keep costs to a minimum (got to keep the Mrs. on side you see) Any advice would be appreciated.
     
  5. rasorinc
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    rasorinc Senior Member

    Look at the Glen- L costumer build photos qf the Squirt. they will answer your question.
     
  6. Mr Efficiency
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    Mr Efficiency Senior Member

    Don't spoil the ship for a ha'penny worth of tar ! I get nervous when people talk about wanting cheaper/lighter methods, the thing has to have a reserve for safety sake.
     
  7. Petros
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    Petros Senior Member

    boat frames do not need to be made of hardwood. Anything and everything, even grass reeds and bamboo, has been used to build wood boats.

    Any fairly clear, reasonably strong tight grained wood should work fine, if it has fairly good rot resistance so much the better.

    If you are building a large boat you may want to adjust the size of members for relative strength. But on a small boat, it will not make any difference. Many of the small boats I have built I have built from salvaged lumber, doug fir, red cedar, western hemlock, mahogany, Alaskan yellow cedar, white oak, unidentifiable "white wood", and many I have no idea what it was made from. It was a nice piece of wood I found discarded at a construction site or in a pile of "free" wood at an old building demolition sites (some of the best wood in fact comes from very old buildings being torn down). You just need to use your imagination to find acceptable wood, and remill it on a table saw, or even a hand held circular saw. Just keep your eyes open when going about your buisness in your neighborhood, you will likely find something you can use. I have even dismantled hardwood shipping crates or pallets that came from overseas, most of the wood was junk, but I was able to pull enough good pieces out that I used it as hardwood flooring in a small room. Most of it was firewood, but it was all free for the taking. I picked those up from behind big stores that large piles of these crates and pallets (I asked for permission first).

    There are a few boats that were designed to use plywood frames, so it can be done, you might see if you can find plans that use plywood frames and follow the plans.

    but it is not that weight or cost efficient since half the grain in a piece of plywood is not in the correct orientation to provide strength. Also putting fasteners in plywood frames is troublesome, you need to add cleats or nailer strips so you never have fasteners going into the end grain of plywood.

    I would prefer to not use plywood frames, it is actually wasteful of materials and not very lightweight way to build. I have built some 30 or so small boats, almost all of wood. Kayaks, canoes, dingys and small tris, none had motors, all muscle or sail powered.

    good luck.
     
  8. PAR
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    PAR Yacht Designer/Builder

    The Glen-L Squirt is a pretty highly loaded frame of minimized pieces. I'm not sure of the scantlings list, but if they're calling for oak, I'd be very hesitant about tossing some spruce in (or whatever), because it was all I could find.

    [​IMG]

    Plywood frames are almost always employ as ring frames, supporting longitudinals, which saves some internal volume, but very rarely as traditional athwart frames. I agree in all that Petros mentions, in regard to poor fastener holding and stiffness, because of grain orientation, etc.

    If you need to make species substitutions, try to match up what you have available with what is called for. There are several locations to get physical properties for common species, so look them up or post them here. Even the UK has dense woods available, if you need them. Typically they're not in the more common places to find wood, but they're available.
     
  9. Damian3716
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    Damian3716 Junior Member

    Would redwood pine be suitable? (bearing in mind I'm in the UK so European redwood may differ from American.)
     
  10. gonzo
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    gonzo Senior Member

    Is there a reason you don't want to use oak? The difference in cost of materials is not a lot.
     
  11. Damian3716
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    Damian3716 Junior Member

    Maybe not in the US, but here in the UK I'm looking at £1.04 per Metre for the pine or £5.95 per metre for oak. In my book that is a big difference in cost.
     
  12. Petros
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    Petros Senior Member

    red pine has about 85 percent the strength of white oak. I presume by "redwood pine" you mean red pine. Or do you know the scientific name for it? So I can verify the weight.

    Seems red pine would work fine, you can make the members perhaps 20 percent larger in cross section if you are concerned. It will not affect finished weight because red pine is lighter than white oak anyway. You may also want to up the size of the fasteners into it, so it has similar fastener strength.
     
  13. PAR
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    PAR Yacht Designer/Builder

    I remember seeing one of these years ago with Douglas fir and SYP frame elements. It was overpowered 50% (20 HP) and seemed to do well. Again, I'm not sure of the scantlings, but if well built, with good technique and species substitutions, you'll be fine.
     
  14. gonzo
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    gonzo Senior Member

    Is that for linear meter? I worked as a shipwright in the UK not that long ago, and the prices were a lot cheaper than that.
     

  15. Damian3716
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    Damian3716 Junior Member

    Yes. The prices I quoted was for 27mm x 44mm stock per linear meter, just as an example of the price difference. I'm just finding it very difficult to find reasonably priced hard woods.
     
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