Prop calculator ( slip % number )

[Christopher Willis]

Using the prop calculator , what's the best all round slip % number to use ? I know each prop is different . Just wondering what average ball park would be !!! ( USING THE ONE ON BYUBOYZ )

Thanks Again

[pyro]

Prop pitch is subjective, because it's only a physical measurement.

There is no "normal" or "baseline" slip percentage.

[rev.ronnie]

I usually throw in 5-7% for sake of argument. I have a couple of props that actually calculate out at less than zero slip though, when rpm is read against GPS readings, so that's where Chad's point comes into play.

[Christopher Willis]

Thanks , just looking for a ball park % number to plug in . I was using 4%

[FrenchPhil]

Cats around 5, vee's 10

[pyro]

By the numbers, mine is around 12-15%, but that's not what matters. The quickest or fastest prop doesn't always have a low slip number in paper.

[Fish]

i usually start with 10% as a WAG and then adjust from there.

[RIVERRUMMER 70]

by the numbers, mine is around 12-15%, but that's not what matters. The quickest or fastest prop "you have tried so far" doesn't always have a low slip number on paper.

i believe the "best" prop IS the one that pushes your boat the fastest AND has a low slip #. You just havent found it yet!
YOU FOUND A PROP THAT WILL PUSH YOU TO A SPEED YOU FEEL IS "GOOD ENOUGH" @ 12-15% ON PAPER.
DO YOU BELIEVE A PROP THAT WILL PERFORM BETTER EXISTS? OR COULD BE BUILT?
I DO! WILL THAT PROP HAVE A LOWER SLIP # I THINK SO!
SO IS IT A COMPROMISE TO ACCEPT A SLIP # OF 12-15% AS YOUR BOAT IS FAST ENOUGH FOR YOU?
OR DID.... TIME , MONEY, PATIENCE, PLAY A ROLE IN YOUR PROP CHOICE?
YES......? JUST SAYIN. YOUR COMMENT MAY APPLY TO YOUR SITUATION BUT CERTAINLY NOT EVERYONE.

[wired247]

I dont think slip numbers matter all that much. Say I run a 28 pitch prop that slips 15% at 7000 RPM and I go 84 MPH. Then I try a 25 pitch prop that slips 5% and goes 84 MPH at 7000 RPM but is a dog out of the hole because it doesnt spool up fast enough I havent really gained anything by slipping less. Ive used props that on paper were negative slip props because their maker produced bogus pitch numbers. Unless you compare apples to apples and oranges to oranges and measure pitch yourself you cant trust slip numbers much when comparing props.

[pyro]

Pitch numbers aren't necessarily "bogus", but they're based on physical measurements of the prop blades, and the resulting "pitch" measurement may not reflect how the prop runs in the real world.

Slip should only be used as a baseline constant in calculations when you want to try out another prop of the same model in a different pitch, so you can get an idea of what RPM or speed the new prop would run.

[cptunnel]

so it is possible to run 1-2% ? cause what im seeing thats what its calculating..

[native2]

I usually seem to run in the 10-15 percent range according to the numbers... The guys that run the 5% numbers probably have lots of prop work done. Most times prop work includes tip cup, if cup is added you have increased the pitch potentially lower your slip numbers... After I add cup to a prop i usually add one inch in picth when running the numbers. Pitch is calculated on average across the blade. a 28 picth prop may have a leading edge pitch of 25 inches and have a trailing edge pitch of 30+... It all depends on prop ad whats been done to it. JMO.

[cptunnel]

gotcha. well guess my mazco is done up a lil more than i thought

[Motv18]

so it is possible to run 1-2% ? cause what im seeing thats what its calculating..

Yep you can turn 86 on a theory of 85. More or less showing effective thrust cup opposed to grip cornering cup. Also could indicate severe tach error.

[LaveyT]

efficiency and prop slip are two different things.