Reply With QuoteI'll give you guys something to think about. This is why I quit doing it.
What if the nozzle bushing only came out 1/2 way and cocked crooked???????
We just had a pin hooked to a cable that let the nozzle out.
Yes, we tried retaining the ring. We put a cable on it and when it came out and hit the water, it sling shotted right past my head. That's when we decided to just let it go. So if you try this, make sure whatever retains the ring lifts it up away from dragging in the water and the jet thrust stream.
my forward reverse cable loops into the air pretty high so maybe if the insert was attached up high like that it would stay out of the water after its spit out of the nozzle. i'd like to find a way to keep the insert in place until just before half track before ejecting it. not sure if that would even be possible.
an adjustable nozzle would be nicer...
I'll give you guys something to think about. This is why I quit doing it.
What if the nozzle bushing only came out 1/2 way and cocked crooked???????
I'll give you guys something to think about. This is why I quit doing it.
What if the nozzle bushing only came out 1/2 way and cocked crooked???????
Cause you'll no longer have control which way the boat decides to go.:idea:
I had assumed small to take off so it just doesnt blow all the water out faster than it can draw it in and open it up for top end to let it flow. For whatever reason, reading forums suggested the opposite.
that's generally correct. at the hit for a boat going 0, increasing velocity slightly isn't as important as increasing mass, everything else being equal. but, you can only go so large, or you'll suck the intake so the pump partially cavitates (i know of one very successful retired racer that wanted to partially cavitate, because he felt he was right on the edge for max acceleration). conversely, with the boat at speed, the velocity need takes precedence.
the absolute fastest speed you can go is going to be limited by either mass or velocity (you can increase hp, but force will still be limited by one of these factors). one of those two factors will be maximized in the force equation. if you can get both to arrive at their limits simultaneously, you've optimized both acceleration and speed.
in duane's case (no offense here duane), he started off with an .06 and went to a .125. now, a .125 is a good medium performance diameter for any hp, and although duane didn't say, he usually raced with higher hp blower boats. in that case, a .06 will get you off the line without cavitating, with great velocitys, but is very restrictive for mass. with the change to the .125, a -significant- increase in mass flow instantly occurs (probably would have seen a reduction in bowl pressure at the same time with data), and velocity didn't reduce enough to negatively impact acceleration.
i am not necessarily suggesting that either small or large is "better" for launch, or top speed. i -am- saying that mass is more important than velocity at the hit, and both mass and velocity are needed for top speed. at different times during acceleration, one of these factors will take precedance in importance over the other.
i only have a little over 800hp in a very heavy boat. but i've made hundreds of 1/4 mile passes, testing everything from a 3.00 to a 3.23 insert. some might say that's only "seconds" of testing, but it's analysis and evaluation of data collected from each "test" that is time consuming. i don't mean to offend, but my view is that in higher hp applications, 1000hp or more, a 3.06 is way too restrictive. mass moves mass.
thinking about it, why are dual drives so effective in bigger boats (and they are, you just don't hear much about them). they don't "double" the velocity, but they do "double" the mass.
ill agree with you on the insert sizing for high hp applications bob. 3.06 only helped my boat holeshot and hurt it down the track. opening up the nozzle netted a better overall et and mph even though the holeshot suffered.
I'll give you guys something to think about. This is why I quit doing it.
What if the nozzle bushing only came out 1/2 way and cocked crooked???????
Well that's enough to keep me from trying it. dont think i'd make it through tech inspection with a set up like that anyway.
also raises the question of safety with some of the proposed adjustable nozzle designs. the "feathers" that old guy proposed could be dangerous if one "feather" didn't actuate and the others did. could send water to one side of the boat that could cause it to turn. hmm. maybe this whole thing isnt a good idea afterall.
ill agree with you on the insert sizing for high hp applications bob. 3.06 only helped my boat holeshot and hurt it down the track. opening up the nozzle netted a better overall et and mph even though the holeshot suffered.
When you say holeshot do mean just getting of the rope and rolled over or are you talking about when it comes off the launch control.
When you say holeshot do mean just getting of the rope and rolled over or are you talking about when it comes off the launch control.
idle to rolled over on plane. how's the new boat coming along?
Things are supposed to start moving along faster after the first of the year. Just getting the motor ready and making some of the rigging right now.
glad to hear it. yours should be incredibly light given how its being laid up.
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