Air injection for planing hulls

Discussion in 'Boat Design' started by CDK, Feb 3, 2008.

  1. charmc
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    charmc Senior Member

    This article from New Scientist (Feb 2006) gives a good overview of research and protypes so far, including mention of the practical problems inherent in scaling up from tow tank test models, as well as discussion of the supercavitation tests which have seen torpedoes travel at more than 100 knots fully submerged.
  2. erik818
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    erik818 Senior Member

    The fan needed to inject air doesn't have to be very complicated. I tried a conventional dust-collector fan (actually the cheepest one I could find in the cheepest store in my area). It provides enough pressure for the purpose of helping the ventilation of a stepped hull.
    My fan has the capacity of 15 cubic meters/minute. A slightly more expensive one, with a 2 kW motor, has the capacity of 45 cubic meters/minute (1500 cubic feet/minute) so feeding the step with enough air isn't a problem. I don't know at which pressure the flow was defined.

    I don't have any results to add to the discussion, as my contraption had too many other problems. The fan worked however, and the bubbles were impressive. (And of course the boat didn't sink, i rose a few cm.) Next time I hope to do it better.

    I think that the hull shape needed to trap the air used for lubrication gives properties that are considered negative from other market aspects. A deep V bottom wouldn't work.

  3. Village_Idiot
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    Village_Idiot Senior Member

  4. AmnonMikeCohen
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    AmnonMikeCohen Inventor

    Thanks kach22i, these people are closer to my invention, but mine is more advanced

    Thanks George, these are closer to my invention, but mine is yet more advanced solution which offers more internal room inside the hulls for cargo or personal use for owners, which are important values to owners; and furthermore, my hulls employ my Water Lubrication layer which by itself is more efficient then the 15% they say come with the additional lubrication while not saying how much more power is being used (I'll try to get this information from them, if they answer me) and also please note, my invention also has an option of reduced pollution as well, so I am still ahead but it is unfortunately still only in my head and my corporate records - and not yet on the market which need good advanced inventions.

    :!: Lets hope we see good news, and thanks for sharing this good DK GROUP work in the art of better and more economic sailings of big ships

    Respectfully and thankfully yours, Amnon Ami Cohen
  5. rasorinc
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    rasorinc Senior Member

    This is probably not of any assistance but don't we have a very high speed torpedo that moves within an envelope of air ? (a bubble)
  6. AmnonMikeCohen
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    AmnonMikeCohen Inventor

    Under the surface travel is not like traveling on the surface, as under the water travel is more like traveling in air to space, with water pressures which are much higher the in atmospheric air and the vacume of space itself.
    Russia had worked on this technology, and I am not sure where the USA is on this art, which is good for Submarines as well as Torpedoes.

    You basically have water and special lubrications options you can pack into a torpedo or a submarine, but air (compressed) is too dear for such use, and can be good for short term as in short distances only.
  7. rambat
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    rambat Member at large

    New stuff?

    I ran a quick calculation and the 20% gain is not proven for the "Ocean Mist" As I am not the only one on this forum with a horsepower to weight, speed prediction program this is offered for comparison. I show that a craft of the weight and horsepower stated would go 27.6 knots conventionally propelled, and 30.4 Knots with surface drives. Both of those predictions are at full load and boats are seldom run for speed trials at full load. I have grown skeptical of most air-film enhanced hulls. I think like any beneficial technology if it were real after the last 127 years since John Thorneycroft discovered it, it would be in widespread use. But I am not here to cast dispersions at inventive ideas, just wish we had something new to check out.
    I think the concept for a air-lubricated hull breaks down in practice when the "film" separates upon contact with the bottom flow, its not like a cohesive sheet and tank video often shows the air "film" streaking into tendrils, wetting the supposed lubricated surface. In spite of this I am a big proponent of SES's and ACV's as they ride on a true air-bottomed hull, most of the time clear of hard contact with the wave tops. And Tom was right IMHO, a cavity sucking air is also likely to suck the hull lower in the water. Also a ACV pushes a depression in the water while at rest but on cushion as if it was a displacement hull, it crawls over that depression or Hump as its known when it starts going too fast for the viscous water to move out from under it, then its planning on its air cushion. The first program I ever wrote was to calculate the depth of water displaced by a SES when on cushion while at rest.
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  8. tom28571
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    tom28571 Senior Member


    Did you look at the proportion of the hovercraft weight supported by the air cushion (pressure) versus the amount supported by the thrust of the fans? The former is bound to cause a depression in the water. I would think the depression gets shallower at speed because of the time element.

    This would be similar to waves from a speeding planing boat getting smaller than at low speed. That is, the dynamic force supporting the boat must be the same at all speeds but the waves created at high speed are spread out over a larger portion of water, making them of smaller height. Total energy in the waves remaining the same.
  9. kach22i
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    kach22i Architect

  10. mmd
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    mmd Senior Member

    The issue with Ocean Mist that made me hesitate to yell about it from the mountaintops was that the entrained air "lubrication" was difficult to maintain in a seaway. Worked great in sea state 0 to 3 or 4 (depending on wave period and form), but failed after that. Since this particular boat worked in the northern trade winds where sea states were normally 4 to 6, it was operationally a failure. In different ambient conditions, such as a sheltered bay or river, it would be a good concept. I'm just waiting for the right commission to come along to ressurect the idea...
  11. rambat
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    rambat Member at large


    Its Mardi Gras down here so that may be why I dont understand the dynamic vs Thrust issue, its also tooo bright right now, must find ....a dark bar to shield my bloodshot ....eyes
  12. AmnonMikeCohen
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    AmnonMikeCohen Inventor

    Air Injection, will leak out if A SKIRT or The HULL can not keep it in the open seaway - and this is its real challenge - as it can grant up to 30% increased efficiency from what I have been told.
  13. kach22i
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    kach22i Architect

  14. AmnonMikeCohen
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    AmnonMikeCohen Inventor

    Thank you, but as you can see, my invention is ahead of them also

    Thank you, very much George, again; I have heard about this project, so thanks for spotting it for me - - but as you may and can see from my more primitive pictures resulted from poor funding, my invention is well ahead of them, as they still have a wake next to the hull (The hull is still Plowing, even it being sharper to cut through the water) and have not climbed "The Hump" of the Bow-wave my invention cancels along with the Skin Friction and Drag which have been virtually eliminated by my invented FINS, achieving this, even without my Secured Air Cavity which is also included in my inventions, as in my registered application in April 1991.
    Yet, this is who should call or contact or respect my work and invite me into the project Europe or America, so we can offer everyone what I can not do alone, as a privately funded successful and honest inventor.

    I wonder how can I get these good guys to contact me for my help to the positive evolution of our maritime industry


  15. rwatson
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    rwatson Senior Member

    "I wonder how I can get these good guys to ...."

    Hi Amnon

    I have been following your contributions with interest, and I do hope you have a successfull technology there, that will be of value to the marine industry.

    May I comment in a constructive manner without wanting to be unkind at all.
    I dont think I am in a position or be an investor or whatever it is you are seeking, but my observation is that your presentation of information could do with a bit of polishing from a competant English speaking technical public relations person.

    While you are listed as being based in Canada, I gather that english is not your first language. The letters you write and your website give me the same feeling as those emails we get from someone in Kenya who wants to send me 3 million dollars and will give me 25%, in other words, they dont inspire confidence in any business dealings.

    From my experience, this appearance in written and web publication, together with your enthusiastic claims, is likely to discourage serious businessmen from approaching you to talk about business opportunities.
    As I say, I am not saying this to be unkind or critical, but as a contribution to your effort.

    I do hope my suggestion isnt at all offensive, and I hope it will help you achieve all the success you deserve. I know it can be difficult to share ideas and research secrets with other people, but I do think you need to approach english speaking clients with a more inspiring standard of communication if you want to achieve good results.

    Good Luck with all your efforts.
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