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Old 14 December 2011, 09:49   #1
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Dimples

Was sent details of a rib today check out its unusual Hull

http://www.airhull.com/LH2Uploads/It...ize_resize.JPG

http://www.airhull.com/LH2Uploads/It...ize_resize.JPG

http://www.airhull.com/LH2Uploads/It...ize_resize.JPGhttp://<br /> <br /> http://www.yo...&v=Dam7ZS59X80http://www.youtube.com/watch?feature...&v=He_XJomox5U




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Old 14 December 2011, 10:05   #2
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A bit like the dimples on a golf ball which apparently reduce drag.
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Old 14 December 2011, 10:11   #3
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They make the ball climb on the air when the ball is spinning, however they also make the ball turn in the air if it's spinning left to right or right to left.

Hence, thats why golfers slice the ball.....
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Old 14 December 2011, 10:20   #4
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A bit like the dimples on a golf ball which apparently reduce drag.
So yes I think you're right, Water rushing over the dimples will cause the hull to lift and maybe feel more lighter???

Just a guess....
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Old 14 December 2011, 10:22   #5
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I seem to recall an America's Cup yacht using a similar surface (though much smaller dimples), maybe 20 years ago?

Mythbusters did an episode on a car using the dimple finish, and found it was actually effective at reducing drag (though in air.)


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Old 14 December 2011, 13:52   #6
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The dimples hold air so the hull has less friction on the water.
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Old 14 December 2011, 14:24   #7
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The dimples hold air so the hull has less friction on the water.
Clever idea must be hard for the tooling of the mold and to get a good lay up , have seen forced air under hulls to reduce viscous drag but never dimples and have seen shark skin swimsuits to reduce it also.

Very clever
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Old 14 December 2011, 15:02   #8
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Very interesting, never seen this before. Typically developments in planing hulls originates from racing boats, but don't know has dimples already been used there.

Will be interesting to see if similar constructions will be seen on other brands also at some stage.
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Old 15 December 2011, 07:42   #9
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Has anyone seen what happens when you hit a golf ball into a lake!!!!!!

Unfortunately, I have - on far too many occasions!
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Old 15 December 2011, 07:53   #10
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Has anyone seen what happens when you hit a golf ball into a lake!!!!!!

Unfortunately, I have - on far too many occasions!
Makes sense then - it becomes a 4-stroke
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Old 15 December 2011, 08:30   #11
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Very good!
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Old 18 December 2011, 11:37   #12
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See this, interesting thread from another forum:
Golf ball boat - install a dimple plate? - Boat Design Forums
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Old 18 December 2011, 17:25   #13
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Osmosis in the mould
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Old 19 December 2011, 07:55   #14
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lookin at it, it should reduce wetted surface area, though i'm not sure about the trade off with all the edges causing extra friction and reduction in laminar flow?
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Old 20 December 2011, 03:15   #15
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A golf ball spins and this won't.

Water will follow the hull and flow into the dimples as there won't be a sharp edge to separate the flow from the hull.

Making it would also be a nightmare.

I'm sure someone would of tried this before and if it worked we would see this everywhere.
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Old 20 December 2011, 03:32   #16
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Quote:
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I seem to recall an America's Cup yacht using a similar surface (though much smaller dimples), maybe 20 years ago?
If memory serves, 1200 grade sanding of the Gelcoat on an Oppie was about optimum - even smaller dimples! Granted speed through the water is somewhat less, but that theory does seem to scale down based on the three part heresay we have generated here.

I vaugely remember it being described as it setting up lots of small circular motion elements of water, thus essentially creating a "rolling" layer a bit like pushing something along on a floor covered in ball bearings. Perfectly smooth the laer of water beside the hull is in sheer, so energy wasted doing that. How that scales up to a rib at 40 knots I'll leave to the hydodynamicists.....
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Old 20 December 2011, 03:41   #17
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Boundary layer.
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Old 21 December 2011, 14:58   #18
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Quote:
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A golf ball spins and this won't.

Water will follow the hull and flow into the dimples as there won't be a sharp edge to separate the flow from the hull.

Making it would also be a nightmare.

I'm sure someone would of tried this before and if it worked we would see this everywhere.
Cookee - that seems a somewhat blinkered view to possible innovation. Everyone told James Dyson that if there was a better way to make a vacuum cleaner Hoover and Electrolux would have found it. Given, as you say, the complexities of making loads of dimples in a hull, that actually fluid dynamics are not as well understood as many people think especially when air, water and solids all interact and that a lot of boat building and design has been about gut feel and trial and error rather than computational models - even if someone thought it might work, that doesn't mean they would have turned it into reality with the right size dimples distributed in the right pattern etc.

Although the idea has been known about for years in golf balls, its only relatively recently that people have started to apply the concept to aircraft: How golf ball

Of course there may be downsides to it too, and any advantage (if there is any) may not justify the cost increase from complexity of production for either average or high performance users, especially compared to other approaches like steps / scallops etc.
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