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Thread: Opti 200 vs 250xs vs 300xs!
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11-10-2012, 09:29 AM #16Team Member
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All things being equal, which they never are, drag is proportional to velocity squared, so speed would be proportional to the square root of horsepower. Except that f=ma, so you need some extra power to actually accelerate to the higher speed. I'd still expect the square ratio to be closer than the cube ratio.
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11-10-2012, 10:15 AM #176000 RPM
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That's exactly what I thought a few years ago, before being corrected by someone on another forum.
Drag force is proportional to speed squared. However, power is a function of force x speed, so speed gets in there one more time making it speed cubed. Here's a good read:
http://phors.locost7.info/phors06.htm
The actual equation is here, showing velocity cubed:
http://www.gtechprosupport.com/support/AeroDragCalc.htmLast edited by engineermike; 11-10-2012 at 10:20 AM.
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11-10-2012, 11:08 AM #185000 RPM
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Nice!
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08-13-2013, 01:15 PM #195000 RPM
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Hello
I was lucky enough to have the oportunity to Check a 250HO on my boat.
Top speed went from 70 to easy 76 mph but with a little difficult sea conditions!
With better sea conditions i think that i could go to 77/79 mph.
The only problem is that the 250HO is borrowed from a friend of mine so i have to take it out of my transom.