Air bubble lubrication successful trials

Discussion in 'Boat Design' started by jakeeeef, Oct 22, 2021.

  1. alan craig
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    alan craig Senior Member

    Dennis Adcock of the Cordless Canoe Challenge did almost exactly that but couldn't detect any improvement. There is a mention in one of my old Watercraft magazines.
     
  2. DogCavalry
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    DogCavalry I aim to misbehave.

    Nope. Stagnation pressure is not the same. If it was, drag would not exist.

    See Pascal's Law
     
    Last edited: Oct 29, 2021
  3. jakeeeef
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    jakeeeef Senior Member

    Yes, I remember!
    I opted for a single 640 Watt Makita drill and two windsurf boards and left everyone in that class standing!
    But, I don't think Dennis had any side fences to keep the bubbles in. It was also a very short hull and very deep in the water.
    I do miss the Beale park show and the CCC which did a good job over the years of filling my garage with Makita drills!
     
  4. jakeeeef
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    jakeeeef Senior Member

    Just a quick note on this subject.
    What about boiling the water so the boat rides on a thin carpet of steam?

    Would be outside my scope and skill set!

    But say you COULD GENERATE the watts to do it, (nuclear perhaps?), Just to boil the thin film of stationary boundary layer water close to the hull?

    Someone must have thought about this and done some sums at some point?
     
  5. Skyak
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    Skyak Senior Member

    Off the top of my head it takes 540cal/gram in addition to the (100-t)/g of power to create the vapor plus whatever heat is needed for the vapor bubbles to survive the length of the hull. If you have that much waste heat there might be better uses.
     
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  6. DogCavalry
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    DogCavalry I aim to misbehave.

    And since the entire point is moving for less energy, that's a hard no.
     
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  7. jakeeeef
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    jakeeeef Senior Member

    Oh well,
    Perhaps humanity will come up with a method of power generation that produces an enormous quantity of waste heat. Enough to heat the whole of the bottom of the hull enough to boil water everywhere on it, even when that water is passing by.
    Then my idea will be less idiocy and more 'ahead of its time'.!
     
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  8. alan craig
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    alan craig Senior Member

    Jakeeef what year did you do the CCC? I was in it 2011, 2012 and 2013 with Four Candles. It was great to see so many different ways of solving the same problem.
     
  9. clmanges
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    clmanges Senior Member

    Don't we already have too many of those? Or are you looking to power a boat on pure entropy?
    Steamboat V 2.0, I take it?
     
  10. jakeeeef
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    jakeeeef Senior Member

    Yes I remember reading about Four Candles.
    You went air prop one year if I remember?

    I did the last 2 years it ran, so probably 2017 and 2018.

    I targeted the subsidiary prize (with limited power allowed) on both occasions, as the main "top speed with any number or combination of power tools" prize was a bit of a chequebook sport. I won both the competitions I entered and the subsidiary prizes were the same as the main one anyway. I don't think I was Mr popular at either of them as on both occasions I did pretty quick and dirty rearrangements of existing plastic hulls, and I think the spirit of it is 'building' a boat, not going round the back of the shed, getting a couple of identical windsurf boards, flicking the dead snails off them and lashing them together. I've found, however, building boats from scratch takes an inordinate length of time, and I'm not minded to do it for a single 2 minute race, when you can clearly win it with existing hulls you can adapt.

    I've only got a bit of video of my last boat. A catamaran. The one before it was a stabilized monohull (trimaran with amas in the air).
    Here it is in testing. It did 9 mph with a single 18V Makita combi drill


    Note ice packs round the battery to delay the dreaded Makita overheating battery shutdown.

    Such a shame the event ended, I had collected enough power tools (partly by the above prizes) to make foiling viable for the first time in the competition. I had a design ready for it.
     
  11. alan craig
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    alan craig Senior Member

    It looks like you are already planing in that video! Yes FC had three propellers in water, then two 32" air props, then two long shafts which kept popping up due to trying to align with the general flow (easily seen in some of the CCC videos on youtube). If you get around to testing air bubbles or foiling etc. get a power meter from a hobby shop; best way to check power requirements and monitor effect of changes.
     
  12. jakeeeef
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    jakeeeef Senior Member

    Yes, very close. I planned to set up a sliding seat later so I could get back and forward at the right times to help it over the hump, but it destroyed itself on the car roof on the way back from the CCC. It would have planed nicely with a bit of fore and aft weight control.

    I ought to post the video on my other thread where people are talking about needing 3.5 kW to get a boat of this weight planing. That drill is the most powerful 18 volt unit that Makita ever made, but it's still only 640 Watts power. That's probably input too, not output, plus I weighed 100 kgs back then.
    Some other people on this forum need to actually get in the shed building stuff a bit more and out on the water trying stuff a bit more.
     
  13. jakeeeef
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    jakeeeef Senior Member

    Direct drive to a very low drag shaft and efficient high aspect prop is phenomenally efficient.

    The human powered boat guys have known this for years!
     
  14. Barry
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    Barry Senior Member

    Why would you think that steam would be a more fuel efficient method of getting air, albeit steam, underneath a hull for reduced skin friction?

    Some other people on this forum need to actually get in the shed building stuff a bit more and out on the water trying stuff a bit more.[/QUOTE]

    There are many contributors on the forum who have built boats, bigger than a couple of paddle boards and an electric drill for power.

    BUT all that being said, you comment about "power generation that produces an enormous quantity of waste heat" got me to thinking that perhaps re routing the exhaust under the hull would be a fuel cheap method of getting air under the hull until I realized that a person would not want to be surrounded by all that ambient toxic fumes. So then a solution may be then is to use a low pressure differential turbo charger/blower, ie the exhaust gas turns the a blower to supply the air.

    The downside then is some additional back pressure on the exhaust side of the engines and the subsequent additional fuel burn. Note the turbo/blower could/would operate that the same pressure on either side
     
    Last edited: Nov 10, 2021

  15. jakeeeef
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    jakeeeef Senior Member

    I read somewhere that several people have tried routing exhaust gases under the hull to little effect.
    I think they found that the issues with back pressure more than wiped out any hull drag advantages.
    The pressurised gas needs to largely be released near the front of the boat and that's not generally where folk want to put their engine, hence a lot of plumbing involved to get the gas up forad.
    It's a good idea in principle I think, just one of those, like air bubble lubrication in general that is rather difficult to execute in the real world.
     
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