LVL Crossbeams

Discussion in 'Multihulls' started by goodwilltoall, May 20, 2018.

  1. gonzo
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    gonzo Senior Member

    There are multihulls, like the Wharrams, that are designed for solid beams and an LVL works fine.
     
  2. trip the light fandango
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    trip the light fandango Junior Member

    I didn't know wharrams used LVL, home built tremolinos make their own, I was on about about the veneers water absorption rate, Douglas fir not bad, many tropical rainforest timbers , like meranti +-1% okume probably good, and others. Over here we use radiata pine for LVL's and it expands a lot. As long as you can see the beam, not built in where water could be trapped in one spot, you're right it may not matter but I wouldn't try to encase it in glass. There may well be such thing as an exterior grade LVL, it wouldn't be cheap here.
     
    Last edited: May 25, 2018
  3. redreuben
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    redreuben redreuben

    Lvl’s have far more timber in than required an “I” beam type structure is what you should be aiming for if building in timber.
     
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  4. gonzo
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    gonzo Senior Member

    They are designed for solid laminations. They use 2x lumber because a backyard builder wouldn't have the capability of gluing veneers.
     
  5. trip the light fandango
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    trip the light fandango Junior Member

    Got it, first make a huge press or employ 50 clamps...the thread started with using house construction beams, I got a little lost with the US measurements/price and affordable beams I see in Aus. The ones we see here blow up when wet and would otherwise suit a ship.
     
    Last edited: May 25, 2018
  6. fallguy
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    fallguy Senior Member

    We need the beat a dead horse emoticon.

    Lvls are really overkill in the yy direction, ftmp.

    The weight exchange is obscene.

    Part of engineering is using strong enough materials that are not too heavy. A steel i beam would be a good example. Unneeded for cat beams of conventional recreational size.

    Building a beam outta 2x is different.
     
  7. trip the light fandango
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    trip the light fandango Junior Member

  8. gonzo
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    gonzo Senior Member

    It doesn't matter what the dimension of the veneers/layers is. The total width and height determine the structural values for the beam.
     
  9. fallguy
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    fallguy Senior Member

    Density
    Douglas fir about 30#/cuft
    LVL about 41#/cuft
    White oak 44#/cuft

    For most boats it comes down to weight.

    Of course density is only valuable when you compare wood or solids.

    The lvl is stronger, white oak likely 2nd, (We'll accept it), but the tradeoff may be unneeded against the fir. See?

    After having handled a few lvls, I know they feel like white oak. A degree of that is also due to nominal thicknesses being larger than conventional lumbers, but they are denser on the saw as well.

    LVL is a very heavy beast for boat beams.

    I was supporting your 2x assertion Gonzo! Sorry if I wasn't clearer.
     
  10. fallguy
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    fallguy Senior Member

    Nominal LVL thickness is 1.75" min; so you also have to account for that beam being thicker. And nominal measures like 2x12 are actually 1.5"x11.25" where lvl is 1.75"x11.875". Sure you can rip them, but plane?

    They simply are not a good choice for most boats.
     
  11. fallguy
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    fallguy Senior Member

    They also bend in the horizontal direction. I have no rating or technical data; but a wealth of hands on experience.

    I am rather confident in standing on the center of a large aluminum mast on its side with little deflection. A lvl will bend a lot.
     
  12. gonzo
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    gonzo Senior Member

    You are comparing a metal alloy with softwood. The LVL is rated for scaffolding though.
     
  13. trip the light fandango
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    trip the light fandango Junior Member

    I think we're flogging a dead horse here, you can laminate your own ply beam, get the correct bend and do it cheap. Mainly because you can now buy F clamps so cheap and they have reasonable strength.
     
  14. fallguy
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    fallguy Senior Member

    Beating a dead horse for sure.

    The metal alloy compare is to show how aluminum is better. I didn't even mention lighter, but it is rather obvious. I realize better is a tricky word. An lvl box beam sized with the same od as aluminum is likely stronger than the aluminum, but the weight tradeoffs are large.

    This guy might need an lvl box when he gets done butchering this (kh)boat. What will fail first here? The aft was beam or the not transoms?
    3EE23F9E-F15A-4D6E-80E9-0F16DA6FB362.jpeg
     

  15. trip the light fandango
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    trip the light fandango Junior Member

    The first cracks will appear in the top corner of the outboard bay closest to the cut off beam. , And the whole lot will come away on a rough day when the inflatable is hanging off the Davits. ..eek, but the build isn't finished yet, surely.
     
    Last edited: May 28, 2018
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