Pumped up masts and hulls ?

Discussion in 'Multihulls' started by EricJo, Jul 24, 2014.

  1. EricJo
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    EricJo New Member

    Is there any merit in the idea of filling masts and hulls with compressed air to improve stiffness and strength, while reducing the mass of the solid materials involved ?

    Best regards, Eric
     
  2. TANSL
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    TANSL Senior Member

    It is a good idea except that impractical, imo. There are several considerations to take into account. One of them is the difficulty of making air tight, any hollow object.
     
  3. Skyak
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    Skyak Senior Member

    SSHHHHH! That's my idea!
     
  4. jonr
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    jonr Senior Member

    I've suggested this too. It works well for inflatables. Fiberglass and aluminum compartments could have a plastic bladder inside to make them airtight. And while load capacity would be reduced if a bladder leaked, the boat wouldn't sink.
     
  5. TANSL
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    TANSL Senior Member

    I think I misunderstood the question and so my answer does not make much sense.
    If it is "to improve stiffness and strength" perhaps a more consistent fill material would be even better. I guess you are talking about the hull watertight compartments.
    I can think of a pair of questions:
    1. Are they detected weakness in hulls to have to resort to a solution of this type?.
    2. if that's the case, it is a poorly designed hull, why not to design it right?.
    3. What air pressure should be put to reduce 1 mm the thickness of steel, or plastic?
    I may still not understand what you talking about. In that case, forget me and apologies for my intrusion.
     
  6. gonzo
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    gonzo Senior Member

    Saturn IV and V rockets were filled with pressurized fuel. Otherwise they would collapse.
     
  7. upchurchmr
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    upchurchmr Senior Member

    Fill them with helium so he actual weight is offset.

    Pressure only provides a benefit if the size of the structure would fail by buckling. So this would be a very special case of the loads and sizing to get any benefit.
    So a mast could work, if you could seal it, and if something else did not cause it to collapse.
    Also the pressure can't distort the shape to where you get a different kind of failure.
     
  8. TANSL
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    TANSL Senior Member

    No need to go to the moon. The planes are pressurized. But I ask again, is it easy to make an airtight boat?.
    So I assumed that there was talk of some compartments of the ship.
     
  9. jonr
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    jonr Senior Member

    A full, sealed can of beer is pretty strong.
     
  10. TANSL
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    TANSL Senior Member

  11. gonzo
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    gonzo Senior Member

    Inflatable boats derive their rigidity from air pressure. The principle is well tested.
     
  12. upchurchmr
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    upchurchmr Senior Member

    Go for it. Let me know what happens to that mast.
    How much thinner will you make the aluminum?
    How much pressure?
    What happens when you are sailing along with a reduced size mast when the pressure leaks out.

    Please point out an inflatable mast.
     
  13. tspeer
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    tspeer Senior Member

    It's hard enough to make a boat that will keep the water out, let alone keep compressed air in!
     
  14. PAR
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    PAR Yacht Designer/Builder

    I've experimented with inflatable battens and foil luffs and it's not as easy as you'd think. Pressures need to be quite high, so material choices need to be well thought out. It's tough to employ reasonably priced materials that are light, strong, can be made air tight, can tolerate UV, abrasion, etc. (the things to address list is long).

    In the end, you can make an inflatable mast, but it'll be a bit like the Goodyear Inflatoplane, which showed similar promise, until the pilot fell out of the deflating nose into a lake. The real issues will be can it be made lighter or as light as more conventional arrangements, with similar abilities, how much would this cost and the practicality of the process, possibly with some failure redundancy built in, for those occasions when you're farther from shore than you can swim back to. Lastly make some raw hull wight comparisons with similar sized 'glass and wood boats, against the usual RIB suspects and see where you stand.
     

  15. waikikin
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    waikikin Senior Member

    Apparently "back in the day" some surf racing skis were blown up on the beach before competing, not sure wether to deal with cool water sucking the ski body down or to keep a positive pressure in the ski, would be funny to see some burly life savers pashing their surf craft in the lead up to a race though.

    Jeff.
     
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