Thread: 3 blade vs. 4 blade impellers
11-07-2005, 09:33 PM #1
3 blade vs. 4 blade impellers
Are higher speeds achievable with 3 blades vs. 4 blades?
11-07-2005, 10:25 PM #2
I think everyone that is running fast is using 3 blades. I just cant see that 4th blade bringing much to top end performance. I bet a 4 bladed prop is great for holeshot and acceleration. My 2 cents is to stick with 3
11-07-2005, 10:34 PM #3
I have to change out my driveshaft to run a 3 blade skat, but it may be worthwhile
11-07-2005, 10:36 PM #4
There is only one way to find out. You can bet the bank the fercho is running 3 blades on his 80 mph ski!
11-07-2005, 11:48 PM #5
The 4 blade was designed to be quieter (believe it or not) and to help the pump more more effecient with lower rpm machines. They will kill top-end speed because of the blade surface area inside the pump. You want less blade spinning in there for top-end speeds. Thats why a Swirl prop is slower than a R-cut prop from Skat Trak. There is a happy medium depending on what you are trying to do.
There has'nt been a faster prop design made, only less surface area engaged in the pump. Just like some skis will run better on a Nu-jet prop because the blade surface is smaller to allow more water to be process at higher rpm's. I hope that makes sense.
Just like an 800 grate reduces incoming force of water into the pump area at higher rpm's, and it translates into top-end gains. There is a balance to be found but you can go to one side of the spectrum for all out top-end set-up, but lose your bottom end. Just like trading off handling for speed..same thing.
3 blades are the best to date for what we are trying to do.
I wish we had a prop that would "morph" from a big leading edge (grabbing water) into a small trailing edge (letting more water through) when going to higher rpm's, sort of like a F-15 jet.
11-08-2005, 09:09 AM #6
..... think i may try a 3 blade
11-08-2005, 10:43 AM #7
What is the pump diameter on an RXP?
11-08-2005, 11:21 AM #8
11-08-2005, 12:33 PM #9
Are there not anyone that has already tried the 3 blade on the RXP?
11-08-2005, 12:38 PM #10
Not any that i know of. You have to buy the Rotax Racing two piece coupled driveshaft ($1900) to be able to run the 3 blade.
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