h a l f b a k e r yI didn't say you were on to something, I said you were on something.
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Porous propellors that exude a wetting solution to better attach the prop to the water, reducing cavitation, particularly when first getting up to speed. Probably useful for slow turning props, like a submarine. May also quiet things down.
The wetting solution could just be water, but adding a
little eco-friendly soap solution would likely make it more effective.
This idea isn't original, I borrowed it from Dolphins who do excrete a wetting solution from their skin to reduce drag.
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A few years back I saw a prototype aircraft wing that had air nozzles on the leading edge through which air was blown. The aim was to reduce stall speed by keeping the flow of air smooth across the wing. |
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I can't see a reason why this technology can't be applied to a propeller - as long as you can make a rotational coupling. |
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But won't reducing the drag of the propeller also make it less efficient at pushing water? That is, won't the prop slip/slice through the water and apply less directional force? |
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This might make more sense if we applied it to the hull of the sub or boat instead of the propeller |
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Aaauuugh! Please forgive me Phoenix, I accidently deleted your last anno. I'm sorry.
I wasn't envisioning it as a flat plate but as a normal looking propellor that had a permeable region, perhaps on the advancing edge of the blades, that liquid could be forced through.
I was imagining that the wetting solution would need to be pumped out at a pretty decent rate for it to be effective. With the fluid pressure high enough (and since it would be hydraulic the pressure could be very high) the material porosity would effectively disappear. |
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I don't know how well a 'porous' one would work, but it shouldn't be too hard to put in channels that picked up water, maybe from farther forward on the prop shaft, and ran it through little slots or something. Would probably work even better with a bit of surfactant. Waterproof bread for you... |
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You know, it's funny . . . . I really thought this idea would get more response than it has. It had been bubbling in my head since early summer, when I was vacationing in the presence of many marine craft and watching, and listening, to their behavior as they accelerated. I guess that length of time under consideration is not proportional to greatness of idea. Ah well, it was a shot. |
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Most of my ideas are like that. I think it's all a matter of timing (especially with the old interface). It was pretty easy to get swept off the 'recent 3' page, and few people check the 'new' ideas link. |
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I don't bother with the 'recent 3' page...I do like the idea, bristolz...I think the problem might be that pretty much everybody has posted what they know... |
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I could be wrong but isn't that why golfballs have their little knobby bits? |
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Passing more easily because a disrupted boundary layer increases turbulence directly next to the ball surface, which in turn disrupts, and reduces, the low pressure wake behind the ball. The reduction in the wake is where the reduction in drag comes from. |
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yes I said all that but it got deleted somehow. |
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Ooops, sorry. I must have deleted it somehow. Good thing I remembered what it was you had written. |
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Putting the dimples on a sub prop might make it work more efficiently, but probably at the expense of noise, which submariners hate. |
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I wonder if a prop made entirely out of soap would work well <until it dissolved away, of course.> |
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too kind bristolz, what a lady, but it was what UB said as well, did you delete that? |
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Starchaser, is that a rugby prop? |
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Ya got me there, po.
Hah! I love the bar soap propellor idea. |
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"Aye, tis Nuclear Spring. Tis green on the outside, and when you cut it open, glows green on the inside!" |
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don't know - ask UnaBubba |
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Ah, an Ook. "Strong like bull, smart like tractor." |
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Well, you can actually make a soap propellor for small toy boats. A little bit of soap will repel water enough to push the boat through the water. Try it some time. |
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A dimpeled propellor would actually cause more cavitation, which would cause more noise... and more damage to the prop, leading to more dimpling, this time unintentional. I suppose with very fine dimpling such as the sharks, this might be different. |
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As for reducing noise, the Navy has done far more than just research. In fact, I'd hazard a guess that they've more or less baked this idea. Not entirely sure how much of it I can explain, or actually discuss, but on my clunky old surface ship, they had a hollow propellor shaft that pumped air out near the propellor. The expanding bubbles of air cut down on cavitation, and therefore on noise, and also increased the life of the propellor. |
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I don't think they came off of the propellor itself though, as that appeared to be of solid brass. |
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i imagine those props would be made of
bronze, not brass... (as brass is a zinc
alloy, and zinc tends to dissappear in salt-
water.) |
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I would think that you'd want a water-repelling effect on the leading surface of the propeller, and a wetting effect on the trailing surface. |
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I would also hope that either of these effects could be achieved using permanent coatings, chemically bonded to the propeller surfaces. |
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Wow, a [bristolz] idea from the turn of the century (tears). |
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" Strong like bull, smart like tractor " |
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Unfortunately, I am years too late, but I fear this idea won't
achieve its goal. Even if the water sticks to the hydrophilic
propeller, what stops it from cavitating a millimeter from
the interface? |
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//Sweating Propellors// Ah, so not a term for extreme pilot panic, than? |
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