Thrust.

[kevbo]

Has anyone measured the static thrust of their ski? A local guy put a load cell on a trailer and let everyone try it out. None of the best running skis could make much over 600lbs of thrust no matter how deep we sank the trailer. All props were all impros modified concords and the engines ranged from ported 701s to a stock stroke lamey. Any ideas?

 

[snowxr]

A test is only as accurate as the testing method. How was the force being mesured? Fwd push of ski, or jet flow from nozzle?

 

[kevbo]

Srtapped to an open trailer sunk up to the hood pushing against a hydrolic load cell. Same test for all boats done back to back.

 

[ATS_Scott]

So were they all pretty close? Even though some had obviously more power?
Could you feel the more powerful ski's cavitating the pump? Usually you have a pressurized source of water (ski moving) but in this case you only have basically stagnant water that can only re-fill the pump so fast.

So get another ski and some 6" PVC pipe and build a pressurized source for the test ski. That should be fun. What are the odds that anything could go wrong? ;-)

 

[kevbo]

The skis were sunk as deep as possible, there was no unusual vibration or even bubbles in the slipstream. I suspect that there is some dynamic pressure recovery when the ski is moving allowing for more thrust . I thought the test was revelant because the most important aspect of performance now is at very low speeds. Nobody is publishing HP or thrust numbers, especially vendors. Im just trying to find some truth in this era of hype and BS.

 

[The Penguin]

would be interesting to see the relationship between the thrust graphed against engine RPM's

 

[restosud]

the static loading of the pump will not get you an accurate reading.
if you were to look at the intake you would see vortices that do not exist under real world loading.
even the best test tank if still somewhat innacurate.

 

[aussiemat]

if all the skis were spining the same revs with the same prop (theoretically) would it matter how much power they had ? i would think thrust would be the same. How much time it takes each ski to reach peak revs/thrust would be the number to see.

Matty

 

[Etheraldreamer]

if all the skis were spining the same revs with the same prop (theoretically) would it matter how much power they had ? i would think thrust would be the same. How much time it takes each ski to reach peak revs/thrust would be the number to see.

Matty

thats what i was thinking as well.
its how fast that ski gets to that thrust number that gives us the sudden BRAP feeling we all crave so much.

 

[kevbo]

would be interesting to see the relationship between the thrust graphed against engine RPM's

Thrust followed rpm directly until about 3/4 throttle, then the meter stopped while the engine revved a little more at WOT.

 

[madscientist]

bottomed out the metering device.

when hurricane ivan hit here the gauges all stopped at a cat 1 but the storm was a ca 4.

 

[kevbo]

It seemed like the meter had hit bottom so I pushed on the ski and it read the extra pressure perfectly. All this makes me wonder if a different pump geometry would be more benneficial than just throwing more power at what we have.