# Thread: Speed and efficency Calculator ?

1. ## Speed and efficency Calculator ?

Hi,

I was wondering if there was any such thing as a theoretical speed calculator ?

i.e. if my 13/22 prop is spinning at 7750 rpm then my speed would be blah blah blah.

I am fully aware that a Kawahadoo ski with an ABC ride plate with Daves mods and 2 shims plus salt water and the Coriolis effect is going to have a different result as some other blokes setup BUT at the end of the day its still just simple maths with some mechanical losses.

Any thoughts or ideas ?

2. I have very similar mods as yours in your sig. I would say you should be at 72 +/- 1. You can check my build thread for more detailed info if you like.

3. I am aware of the speeds and mods data base. I guess I was getting at the maths involved in spinning a paticular prop pitch at a particular rpm, much like a gear box or diff ratio.

Are prop pitch numbers just numbers or do they actually give an indication distance moved ? i.e. with a 13/23 prop does this mean for every one rev the prop will move forward 23 inches ?

4. Originally Posted by Dan_FZR
I am aware of the speeds and mods data base. I guess I was getting at the maths involved in spinning a paticular prop pitch at a particular rpm, much like a gear box or diff ratio.

Are prop pitch numbers just numbers or do they actually give an indication distance moved ? i.e. with a 13/23 prop does this mean for every one rev the prop will move forward 23 inches ?
our props are based on degrees of angle and not inches of travel like boat props are. So you can't come up with formuls like the boat people use that will end up giving you the % of prop slip. Tommy Jordan

5. Originally Posted by 2fast4u
our props are based on degrees of angle and not inches of travel like boat props are. So you can't come up with formuls like the boat people use that will end up giving you the % of prop slip. Tommy Jordan
+1