Prop slip-prop efficency formula

[Costa]

I once had a formula where you multiply rpm times gear ratio times speed or something like that and it gave you your prop efficency but I cant seem to find it :nonod: Does someome have the formula or can tell me what it is? Sorry for the dumb question but I am testing some new props and would like to find out what the "slip" ratio is.

[Ted Stryker]

This is My favorite of the charts found on the internet...

http://www.mercuryracing.com/propellers/propslipcalculator.php

[Mark75H]

Prop efficiency and slip are not the same thing. Efficiency is how much thrust is made vs the input energy, slip is how effectively the thrust is used ... technically a prop can be very "efficient" and the rig can still have very high slip because the boat is a piece of crap.

I like the rbbi online calculator: http://www.rbbi.com/folders/prop/propcalc.htm

[Costa]

Thanks a bunch guys! Those were the ones I was looking for.

[larwat]

file:///C:/DOCUME%7E1/Larry/LOCALS%7E1/Temp/moz-screenshot-4.png211149

[Jimboat]

Prop efficiency and slip are not the same thing. Efficiency is how much thrust is made vs the input energy, slip is how effectively the thrust is used ... technically a prop can be very "efficient" and the rig can still have very high slip because the boat is a piece of crap.[/url]

I agree with Mark75H - it's worth understanding the differences between 'slip' and 'propeller efficiency', since the most 'efficient' prop may well demonstrate a higher 'slip' than a less efficient prop/setup. Slip is merely the difference between 'theoretical mph' and 'actual mph' and is a pure calculation. So slip isn't usually a measure of 'efficiency'.