Helium?

Discussion in 'Laser Talk' started by Crazy-J, Dec 30, 2011.

  1. Crazy-J

    Crazy-J New Member

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    Is it class legal to fill your hull with helium? Would filling your hull with helium make your laser sit higher in water, thus reducing friction on some bits of the hull. In theory making you go faster?
     
  2. cmansonh

    cmansonh Member

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    I have pumped air into my boat to prevent make it cut through the water better but i never have heard of helium......
     
  3. Crazy-J

    Crazy-J New Member

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    I thought it was a neat idea and would be something test. But you know what i mean about floating higher, right?
     
  4. 49208

    49208 Tentmaker

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    Just add some foils, a nice 2 element wing, and a carbon fiber/nomex hull, should be good to go... Shoot, forgot, add a trapeze and carbon mast..
     
  5. spencer.

    spencer. New Member

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    if you're going to try this, be very careful... a little bit of pressure can rip your boat apart at the seams
     
  6. Crazy-J

    Crazy-J New Member

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    I havn't tryed it out or anything but what i meant is it would be neat if it would work.
     
  7. sorosz

    sorosz Member

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  8. torrid

    torrid Just sailing

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  9. SFBayLaser

    SFBayLaser Member

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    I would argue that the Fundamental Rule would say its not class legal since you would need to modify the boat to make it airtight (in particular sealing the air hole under the hiking strap). But in the end it would be the interpretation of the Chief Measurer that would matter.

    That said, I wonder if it would really make a difference? Don't forget that most of the "weight" of a floating Laser is in the hull/spars/sail (we'll come back to the sailor in a moment). Assume an order of magnitude guess of about a cubic meter of volume inside the hull, that's around a couple of pounds of air. So even if you could create a vacuum in your hull you could at best save around a couple of pounds out of an all up weight of something like 150 lbs (hull plus spars plus rigging plus sail minus sailor). In the end its a bit hard for me to believe that a couple of pounds will make a difference...

    ... because, when you add in the sailor you typically more than double the weight of the boat. And depending on conditions, the gear that a sailor wears can weigh a fair bit too. These are variables that can be more easily controlled, with greater overall impact, than trying to do something fancy with the boat. At least in my opinion, reinforced by noting that regatta results generally depend on sailor weight to the 10's of pounds level, not the 1's of pounds.

    That's just off the top of my head, maybe the naval architects can weigh in.
     
  10. Crazy-J

    Crazy-J New Member

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    considering i'm 78 pounds. And gases are compressible... you have to figure out how compressed you can get it per meter cubed, and figure out how much that gas weighs in total. Take the lifting force of gas per meter cubed and subtract gas weight and hull, spars and sailor weight = how much boat could potentaily weigh. Thats just my guess at a way to figure that stuff out. equation is as follows(in my opinion):

    modifiedweight = ((gas per cubic meter x volume of hull) x lifting power of helium per cubic meter density) - (sailor weight+ spars + gear + sails) =modified weight

    theory= displacment(in pounds) - modified weight

    ^^ not acurate im just guessing and throwing stuff
     
  11. Elessar

    Elessar Member

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    What I thought would be a good plan in addition to the hull filled with helium is....

    To use a completely sealed top section, filled with helium.
    Thus lowering the centre of gravity and making it easier to stay upright in strong winds.
    =P
     
  12. Crazy-J

    Crazy-J New Member

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    Thats a good point. What if you injected helium into your top section spar and compressed it and sealed it? Would that not have the same effect but not on same scale?
     
  13. racingkyle162

    racingkyle162 New Member

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    It is true that gases are compressible but i wouldn't want to have any sort of pressure in my hull even something as small as 1 psi could split your boat in to pieces. If you think about it 1 pound per square inch is a lot of total pressure when you also think of the amount of square inches that this pressure would be exerted on. i don't actually know how many square inches it would inside the laser hull but just as a small example 1psi on something that is 700 square inches is equal to 700 pounds of force,and the amount of space in a laser is probably a lot more then 700 square inches and these amount of pressures could surely tear your boat apart.
     
  14. SFBayLaser

    SFBayLaser Member

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    Remember, helium has no special "lifting" property to it, other than its mass. So, for example, an airship achieves neutral buoyancy and "floats" in air because the mass of air displaced by the the volume of the airship equals the weight of the airship. The standard gas used in an airship is helium because it is the second lightest element, is readily available and doesn't combust (hydrogen gas, if you like, is half the weight but, of course, we all still remember what happened to the Hindenburg).

    Also note that you want to equalize pressure in an airship - overpressuring does you not good as it simply adds weight to the airship, decreasing its bouyancy. (Ok, skipping some details related to atmospheric pressure at different altitudes...)

    Here's an example (and for this thread think of the block of wood as a Laser, the oak block as a Laser filled with air and the pine block as a Laser filled with helium). Anyway, the point remains that it is the difference in the mass of the volume of air that is changed out that matters, and I'd think that would be small here.
     
  15. Emilio Castelli

    Emilio Castelli Member

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    If you are 78 pounds you are plenty light already.
    Compressing the gas would just add weight.
    E
     
  16. Emilio Castelli

    Emilio Castelli Member

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    Compressing the gas would just add weight.
    For the mast, pulling a vacuum would be lighter and cheaper. Difference in weight would be hard to measure anyway (grams I would guess).
    Pulling a vacuum in the hull would crush it.
    Happy New Year!
    E
     
  17. Crazy-J

    Crazy-J New Member

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    But if you inject helium into your top section and seal it, would that not make top section want to stay up right. Thus helping you boat stay up right
     
  18. Rob Hair

    Rob Hair Member

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    So I guess we could pump enough helium into our masts and get our Lasers to fly!
    I think this discussion is three months and one day early.
     
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  19. Crazy-J

    Crazy-J New Member

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    No want im getting at here is that would it help them stay up right? Plus i don't understand 3 months and 1 day early.
     
  20. Merrily

    Merrily Administrator Staff Member

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    April Fools. You've already had a rocket scientist in this thread indicate that it won't work.The mast section is too heavy to be affected by the amount of helium that you could get into it. Do you see the tank of compressed helium at the balloon store trying to float away? You can't achieve the necessary neutral buoyancy.
     

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