Bam marines prop slip calculations aren't right

[blackhawk]

Anyone notice that Bam marine's website has the wrong prop slip formula? And their calculator is wrong if you plug in your actual speed and hit the calculate button under slip.

I don't know if it's always been like that or something got screwed up. But I started playing with the numbers and noticed it. Both the formula and the calculator will give you higher slip readings than what you actually have.

[mattyboy]

in your case I hope your dividing that number by 2 ;)

[RvR]

The Theoretical Speed equation is correct and the calculator works correctly. I don’t know why they define slip as a percent change rather than a direct percent, I would simple define it as:

Slip=Actual Speed/Theo Speed

But either way their calculator handles the Actual Speed calculation incorrectly. In fact it looks like they are calculating the Actual Speed as if they were using the above definition for Slip rather than the one they list.

[blackhawk]

The theor speed equation is correct. The slip equation is wrong. Slip is determined by theo sp - actual speed then divided by theo sp(not actual speed). That is where their formula and the calculator is incorrect.

[blackhawk]

in your case I hope your dividing that number by 2 ;)

Matty, took me a minute to get that. Haven't had my coffee yet! ;)

[blackhawk]

Marc from Bam saw my post on OSO and fixed both the formula and the calculator. That drove me nuts for a few minutes until I figured out what was wrong!

[RvR]

That definition for slip makes more sense and yup the calculator is working now.