Prop Slip Explanation

[Cricket Too]

Hey all, can somebody explain the basic theory of prop slip to me, I have read some things but can't get a clear description of exactly what it is and how it affects performance. Thanks. Mike.

 

[Dhadley]

Re: Prop Slip Explanation

Its theory vs. actual. Pitch is measured in inches of forward motion. A 19" pitch prop will -- theoretically -- travel forward 19" in one revolution. In reality it slips some and does not make it to 19". The difference is expressed in %.<br /><br />Hope that helps!

 

[JB]

Re: Prop Slip Explanation

Howdy, MMCPeck.<br /><br />If you have a 20" pitch prop and you are turning it at 3,000rpm, you can calculate that it "should" be moving the boat at 56.8mph.<br /><br />It doesn't. It probably moves the boat at about 50mph. That missing 6.8mph is because the prop is in water and it is moving water back as well as the boat forward. The 6.8mph is "slip". It is usually expressed as a percentage of the theoretical speed.<br /><br />In this case the prop has 6.8/56.8, or 11.97% (call it 12%) slip.<br /><br />Hope that helps.

 

[JB]

Re: Prop Slip Explanation

Apologies, DHadley.<br /><br />You posted while I was typing.

 

[Dhadley]

Re: Prop Slip Explanation

Its a tie!<br /><br />Does the tie still go to the runner? Or are we going on a time vs distance thing? Or do we have to re-run it? Or was it a photo finish?<br /><br />Never mind -- see what happens when theres no NASCAR?

 

[steam_mill]

Re: Prop Slip Explanation

Moderator:<br /><br />This is an excellent explanation of Prop Slip. I think this should be moved to the General Outboard discussions......<br /><br />Just a suggestion...

 

[JB]

Re: Prop Slip Explanation

Good idea, Steam_Mill.<br /><br />Consider it done.