Freestyle Rider Weight Vs. Impeller pitch?

[munki63]

When somebody asks the question what pitch do I run with my set-up, typical response is x/x hooker bore you nozzle and use a stubby... I do know lighter skis are pitched differently but I've never seen the how much do you weigh question, and there is no way IMO an impeller pitch should be the same for a 200lb rider vs 100lb rider or am I wrong? If I'm right the heaver you are the less aggressive you would want to be?

Make sense or am I out to lunch

 

[1fastsedan]

i think you would want the heavier rider with the more aggressive pitch. more weight is going to make the ski harder to get moving. but i dont think weight matters here. the pitch of your blade should be for your style of riding or to get the most juice out of your pump. some guys like more punch/bottom end. others need top end for racing. we play with different pitches in our V-drive to squeeze more top speed. and of course the lighter the faster. we lose about 5mph for every person in the boat. but i could be completely wrong.

 

[munki63]

If you have a 255 rtr hull with a 200lb rider vs a 100lb rider thats 22% lighter(Ski+Rider), which would also be harder to move.... a more aggressive would also be harder to move, so to make up the difference wouldn't you want a less aggressive impeller for a heaver rider... nothing crazy more aggressive just a little...

 

[1fastsedan]

here's what skat recommends: [FONT=Arial,Helvetica,Geneva,Swiss,SunSans-Regular][FONT=Arial,Helvetica,Geneva,Swiss,SunSans-Regular]"Each watercraft is unique in hull design and horsepower. Some watercraft are designed to carry 1 person, and others up to 3 people. With a varying amount of riders, weight being carried on some craft can fluctuate up to 500 pounds. The more weight being carried, the more bottom end you will need to get up on plane quicker. Another example of low end thrust needed would be pulling a water skier or knee boarder. The desired performance is usually more bottom end, which will be achieved by choosing 1 pitch combination lower than our general recommendation listed. We do not suggest choosing a pitch combination higher than our chart suggests for light weight riders.[/FONT][/FONT]"

 

[kevbo]

When somebody asks the question what pitch do I run with my set-up, typical response is x/x hooker bore you nozzle and use a stubby... I do know lighter skis are pitched differently but I've never seen the how much do you weigh question, and there is no way IMO an impeller pitch should be the same for a 200lb rider vs 100lb rider or am I wrong? If I'm right the heaver you are the less aggressive you would want to be?

Make sense or am I out to lunch

You want to set the pump load for maximum static thrust. That requires the engine to reach peak HP rpm in a tail stand. The best top speed/rough water load will be about 100-200rpm below this.

 

[munki63]

You want to set the pump load for maximum static thrust. That requires the engine to reach peak HP rpm in a tail stand. The best top speed/rough water load will be about 100-200rpm below this.

And in doing so rider weight is a not factor? do you have a process to figure out if your pitched properly?

 

[kevbo]

And in doing so rider weight is a not factor? do you have a process to figure out if your pitched properly?

Rider weight wont infuence the thrust that an engine/pump is producing. Ideally, you need an RPM target and a tach. A seat of the pants method is noting how quickly the pipe hits from idle. Any lag indicates too much load. Even a pump gas 62T cylinder can go from idle to full thrust in less than 1/2 second. A lean pilot/popoff can have the same effect so make sure it sputters a little at steady 1/4 throttle.