prop slippage %?
- Thread starter ZIonOB75
- Start date
Help Support Intlwaters:
Jul,
30% is very accurate,believe me. The slippage is not really a big deal,
the efficiency of the blade profile according to your application is really
the big story. RPM is another big issue in the go fast equation. Our motors
work the best when we can really get them spinning to the moon. :lol:
Good Luck Testing,
Mark Sholund
30% is very accurate,believe me. The slippage is not really a big deal,
the efficiency of the blade profile according to your application is really
the big story. RPM is another big issue in the go fast equation. Our motors
work the best when we can really get them spinning to the moon. :lol:
Good Luck Testing,
Mark Sholund
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sneakysneakyracing
Well-Known Member
- Joined
- Aug 9, 2006
- Messages
- 179
i did a test on this
with on of my ob first i mesured the rmp at full speed on a long straght with a x447 prop.
the checked the gps on the boat that i was sitting in.
after a 200m run at it full speed i got some calulations to put against this configuration.
average speed for one min devide by rpm will give you a distance of the prop traveled devide by the prop size. i worked it our to a slipige of 25% to the size of the prop. but from my calculations if you are trying out work out how well a new 35,000 rpm engine will go on your boat the answere is just buy one and try it out. i have found that you can get a engine running higher rpm than the manufactures specs.
i did this calculation for my old fall to pices plan.
a geared twin K&B outboard power head.
the hull was a titan 40. i figured 1.2 ratio on the gears will make 6hp at 50.000 rpm
the result was a broken wallet and another boat on the shelf.
new project cmb 100 on a lawless lower. should give the zenoah tunnels a run for there money.
with on of my ob first i mesured the rmp at full speed on a long straght with a x447 prop.
the checked the gps on the boat that i was sitting in.
after a 200m run at it full speed i got some calulations to put against this configuration.
average speed for one min devide by rpm will give you a distance of the prop traveled devide by the prop size. i worked it our to a slipige of 25% to the size of the prop. but from my calculations if you are trying out work out how well a new 35,000 rpm engine will go on your boat the answere is just buy one and try it out. i have found that you can get a engine running higher rpm than the manufactures specs.
i did this calculation for my old fall to pices plan.
a geared twin K&B outboard power head.
the hull was a titan 40. i figured 1.2 ratio on the gears will make 6hp at 50.000 rpm
the result was a broken wallet and another boat on the shelf.
new project cmb 100 on a lawless lower. should give the zenoah tunnels a run for there money.
- Joined
- Oct 23, 2002
- Messages
- 6,451
wow... that sounds like something I want to see! A boat that will turn 35,000 rpm on the water, with a prop attached! much less 50,000 rpm twin K&B's. :blink: :blink:
What did you use to measure RPM while on the pond?
h34r:
At this point, from what I saw at the World Tunnel Champs, most anything will give a Zenoah outboard tunnel a run... They havent found the set-up for them yet (atleast I hope not). A 3/16th shaft is gonna catch hell with a CMB100, unless your going with a gas lower?
interesting....
~James
What did you use to measure RPM while on the pond?
h34r:At this point, from what I saw at the World Tunnel Champs, most anything will give a Zenoah outboard tunnel a run... They havent found the set-up for them yet (atleast I hope not). A 3/16th shaft is gonna catch hell with a CMB100, unless your going with a gas lower?
interesting....
~James
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