USA-Technical Details-Helium used

Discussion in 'Multihulls' started by Doug Lord, Mar 27, 2010.

  1. Chris Ostlind

    Chris Ostlind Previous Member

    Why not indeed, Evan?

    One of the cool things about the space program is that they could openly prove the use of the structural application. This supposition trail is filled with bilboards that are all about the opposite... there is no proof anywhere to be had that the USA7 hull was a stressed pressure vessel for purposes of strutural integrity. Not one bit of proof.

    I'll be happy to enjoy the possibility when one of these guys produces something... anything... of substance that supports the wild-eyed supposition.
     
  2. CT 249
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    CT 249 Senior Member

    None of us are doubting that pressurized hulls can provide rigidity in some situations, merely whether they would work in a racing yacht which is in a very different situation.

    Personally, I love pressurisation in the right place (ie my bike tyres, which are at very high PSI yet remain vastly more flexible than any boat) but not in the wrong place (ie excess pressure inside my windsurfers, which can blow them apart AND make them more flexible). So it's not bias against pressure.

    As to balloon tanks, well, I'm no rocket scientist, but the situation seems very, very different. The balloon skin tanks are cylindrical, which is a good shape for a pressure vessel; they were (according to the net) .048 to .015 of an inch thick. They were so thin that the rocket was normally stored at 90 degrees to its operational angle, always had to be pressurised, and had so little impact resistance that there was at least one instance of a rocket blowing up after a mechanic dropped a wrench on it.

    No practical racing craft is going to have such a thin skin, because it is always subject to impact loads from small objects in the water. No practical racing yacht can have such a thin skin, because there are crew running around it. No practical racing yacht is a complete cylinder, so somehow you have to build in a means of retaining a proper hull shape.

    So you're going to have to have a heavier skin to resist such loads, which means that you will surely lose the benefits of the thin skin that was the raison d'etre of the balloon tank.

    Ironically, I was reading JE Gordon (prof of engineering) last night and came across the chapter where he was dealing with the explosion of pressure vessels. It was interesting to read how the fitting of gussets and frames (which would almost certainly be necessary to handle the keel and rudder loads, rig loads, fitting loads, winch loads etc) can destroy the structural integrity of a pressure vessel. Doesn't sound like an ideal way to save a few kg.

    Let's note - inflatable sailing craft have been created. I've sailed a couple. At practical pressures, they were god-awful because the pressure was inadequate for rigidity, and that was on windsurfers were rig tension is not an issue. One practical and reasonable-performing inflatable cat did quite well in the UK, but it had to have extra "streamlining" added on to the cylindrical hulls and it suffered from lack of rigidity, therefore it was not a great performer.


    Doug, as Paul noted, there were many other ways to reach measurement trim that would not have changed the performance of BMWO significantly.
     
  3. mark775

    mark775 Guest

    "If you are looking for "lift" from the gas you would not pressurize it, and any "composite structure" is going to be heavier than a blow molded PE bottle, so would be heavier than the offsetting "lift"." - There are three different proposed reasons for the use of helium. You seem to be trying to obfuscate a bit here.
    Reason one, the original assumed and proposed reason - to help lift the hulls to meet a rule or have less wetted area to sail faster by means of reducing the weight of gas in the structure.
    Two, I suggested that there might be a manufacturing purpose that we are so far unable to qualify. We just don't know.
    Three, the reason I proposed that makes sense to evandepol and me, that a vessel (a container, be it an entire hull, a portion of a hull, or a vessel within the vessel). This reason does not so much look for lift from the lighter than air helium but lift from being able to reduce structure.
    I know why Chris is aggressive towards me. Paul, it seems you are simply being argumentative for argument's sake. I have nothing into this and was simply joining a discussion because, again, I saw someone getting cornered for no good reason. Now that I think Doug has demonstrated that someone on the Team at least mentioned helium, even if he didn't state a purpose, I'm done here. I will, however, play with the idea of applying pressure to increase rigidity in a structure - I believe many types of boats could benefit from pressure in, at least, certain areas.
    Parting shot; A 31' Cris Craft will always split its hull forward of the foward bulkead when it flexes against the hard spot of the forward end of the stringers and the bulkhead. Many have added stiffeners, which seem to simply move the hard spot further forward. I propose that a balloon of some sort (an A-4 Norfloat?) could be placed in that compartment, inflated, and absorb a substantial part of the flex without creating a hard spot. I'm sure you'all will find problems with this approach, and that is fine. Carry on...and thanks again, Doug, for an interesting thread.
    imalkjglkges.jpg
     
  4. catsketcher
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    catsketcher Senior Member

    Pressurising would not help

    Pressurizing a hull would not help reduce composite layup because you would increase the bending loads on the laminates. Any bulkhead would be a non moving hard spot and the panels between would then be deflected sideways increasing rather than decreasing deflection. As stated by CT - boilers are weakened by "strengthening inserts"

    The Atlas rockets were not well thought of by Von Braun who developed the V2 and Apollo rockets. And they are round and the skin was so thin that it would locally buckle under fuelled weight. So pressurizing stopped the walls from local buckling. It would not help sandwich composite skins which have a major load sideways across the panel. It would be much easier to laminate in a shelf or stringer for very little extra weight.

    But really who are we kidding. A story - I used to race a class where a couple of guys used to import US battens into Australia for one design racing. They were going on about the amazing properties of this batten. Well these guys weren't that fast and the guy who won the championships didn't even know what type of batten he had. He just sailed better. Do we really think that helium had anything to do with the tri beating the cat? Moving the motor forward or aft an inch would have altered the waterline length or whatever other measurement more than the helium did. Thinking that tiny things matter is the mark of the misguided. Judging the layline properly. getting the starts right, getting the shifts right. having a tall enough mast. These simple things were the ways the cup was won.

    Rodney Pattison had instruments on the FD Superdocious. He unplugged them for sailing, he just messed with the heads of his competitors. This is about the same.

    I would ask that Doug gets less emotive with his posts. It is not helpful to be so rapturous about very small things as they obscure the truly amazing. Helium is not a breakthrough and never will be but the tri had many design aspects that do truly warrant discussion. Helium definitely is not one.
     
  5. Doug Lord
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    Doug Lord Flight Ready

    =========================
    I disagree. If my sources are correct helium made the difference between winning the Americas Cup and being disqualified. My excitement about this incredible application of helium may be a "very small thing" to you but it seems that the "truly amazing" may have escaped your grasp in this case.
     
  6. Chris Ostlind

    Chris Ostlind Previous Member

    The moving of the engine comment, Phil... in one ear and straight away out the other.

    At least you tried... as did Bill, Mal, Chris, etc.

    Big, big story, this helium thing. So big they had to get additional valets at the Newport Harbor Yacht Club because all the oldtimers wanted in on the conversation at the bar. So big that the Newport to Ensenada Race has been postponed until the chatter dies-down about helium as the coming savior of the sailing industry. So big that I'm going to slip a free, carbon wrapped paintball canister of the stuff into every Europa 20 design package I sell.

    I'm convinced, helium on racing sailboats is here to stay.
     
  7. Doug Lord
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    Doug Lord Flight Ready

    ======================
    You just don't get it ,CT........
     
  8. Chris Ostlind

    Chris Ostlind Previous Member

    Actually, no, Doug.

    Judging from the vast array of learned responses to your "truly amazing", self-generated epiphany... it is you who does not get it. You and your various and sundry apologists, alone against the world. Just the way you like it.

    One look at your shaky substantiation and it becomes abundantly evident that you have zip... As In Nothing.

    Produce the sources, or be comfy in your singular cocoon of disconnect, but please... do not equate your current distraction fantasy with anything like a real story until it can be proven without question. Yes, this would include the showing of photos of the system in question, as well as a significant, on-the-record, statement by a person of substance from the USA7 camp.

    When you get that, we'll be happy to adore you as you desperately desire. Until then, this is just another flapping Lordism, much like all the others we have witnessed before. Remember that claim that the AeroSKIFF actually got it's fanny up and off the water?

    Monumental sailing development in the last 50 years? That is a completely different question and you are not even close.
     
  9. Chris Ostlind

    Chris Ostlind Previous Member

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  10. TeddyDiver
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    TeddyDiver Gollywobbler

    Agree!! :)
     
  11. Doug Lord
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    Doug Lord Flight Ready

  12. ancient kayaker
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    ancient kayaker aka Terry Haines

     
  13. Doug Lord
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    Doug Lord Flight Ready

     

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  14. ancient kayaker
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    ancient kayaker aka Terry Haines

    I see: it's because of the curve. separate horizontal and vertical boards would not do that so they are not equivalent after all. Tks
     

  15. Doug Lord
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    Doug Lord Flight Ready

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