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Old 02-01-2006, 02:51 PM   #1
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Power = Speed = Power ?

Furthering my education:

Take a 'standard' v hulled stepped boat - for this example assume it is a V24.

Assume we have 300HP engine, and we travel 70mph at top speed. Assume we are pulling 4500 RPM top end and the engine is unlimited in RPM.

Without changing the props, drive hull weight or anything else, we magically increase the power to 400HP. Now to my brain, we have an increase of 33% in power. ( no rev limitiations in this magic engine ) I am going to assume I do not get a 33% increase in speed ( only the engine is magic, not the boat! ) - So I will have losses due to increased wind resistance, and increased resistance to the water by the hull. Is there a calculation I can apply?

What if the engine can suddenly apply 600HP. This is doule the power. I will not see 140mph, what speed would I see. Is this a guess or is there a calculation?

??
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Old 02-01-2006, 02:57 PM   #2
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http://www.go-fast.com/boat_speed_predictions.htm
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Old 02-01-2006, 07:36 PM   #3
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What should i enter the Constant as???
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Old 02-01-2006, 08:08 PM   #4
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Because I have exact information, I can alculate the formula constant for my boat ( 248 )

From this start point, I can then move forward to experiment with new values.




John, matttt, This would be very very easy to write for Boatmad, and you could place it in a section of the website.


I have written a very simple popup for conversions at www.seahorse.org, second menu option: Calculate. This is used regularly, and the process would be similar to do the calculations for the boat stuff here....
.
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Old 02-01-2006, 08:42 PM   #5
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Doesn't everything increase by the square? So you'll need at least 4 times the power to go twice as fast.
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Old 02-01-2006, 09:00 PM   #6
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Quote:
Originally posted by jw.
Doesn't everything increase by the square? So you'll need at least 4 times the power to go twice as fast.
In cars its roughly 8times the power for twice the speed
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Old 02-01-2006, 09:46 PM   #7
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i was always told:

the Angle of the Dangle
Is directly proportional to
Lust of the Thrust
providing the Urge remains Constant

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Old 02-01-2006, 10:02 PM   #8
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Quote:
Originally posted by jw.
Doesn't everything increase by the square? So you'll need at least 4 times the power to go twice as fast.
spot on!
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Old 06-01-2006, 05:32 PM   #9
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power=speed

another rule of thumb you can use from our experience is speed increase is aproximately the square root of the power increase
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Old 06-01-2006, 06:08 PM   #10
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Isn't that the same rule with different words?
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Old 06-01-2006, 06:15 PM   #11
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Quote:
Originally posted by streamlined propellers
another rule of thumb




Quote:
Originally posted by jw.
Doesn't everything increase by the square?

dat streemlyned nobbur az probubly gott too thums

wan ov dem mus bee upp iz azz

gArf
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luk arfter nummber wan. downt stepp inn nummber too
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Old 06-01-2006, 10:59 PM   #12
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u must be pissed. if you dont want help dont ask questions
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Old 07-01-2006, 01:10 AM   #13
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Quote:
Originally posted by streamlined propellers

u must be pissed. if you dont want help dont ask questions
What question dude???
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