A motor that makes a hard hit at the launch to build a good ET will require a pump that can absorb the hit to make the HP reach the track. This must occur immediatly at launch. A lake boat setup for top speed does not need the immediate hit for the launch, it can sacrafice some of that hit for top speed later on down the lake. I will try to figure a better way to explain it , but thats the gist of it. Trade some launch for some speed. Power where you want it. TIMINATOR
I there a White Water guy on here with good pressure readings? That would ve very helpful because we run long with minimal acceleration and would be a good comparison. It would also be nice to see some numbers from a spoon loaded pump with no shoe/loader. I'm betting the pressures are lower but the water has to be there, there are plenty of guys running over 100-Aluminum Squirt
thats interesting.
myself and the rest of the guys i go to the river and race with look for a good hole shot along with big top end. not one or the other. If I had to pick one or the other id look for a strong 1/8 mile, thats what wins a race.
dont come to big river with that set up, you wont win a single race.
A motor that makes a hard hit at the launch to build a good ET will require a pump that can absorb the hit to make the HP reach the track. This must occur immediatly at launch. A lake boat setup for top speed does not need the immediate hit for the launch, it can sacrafice some of that hit for top speed later on down the lake. I will try to figure a better way to explain it , but thats the gist of it. Trade some launch for some speed. Power where you want it. TIMINATOR
this rationale makes no sense to me either, so i think we'd all like to hear more about how this is supposed to work? how long does it take to get the boat planed with this "lake boat hi speed" setup? how far do you have to go to get to top speed? 113 is no big number, so how far did it take to get up to, say 100?
if i saw 12psig, my bowl pressure would be in the tank. i don't care how shallow the shoe is, how much ramp is cut back from the loader, or how fast the boat is going; if it's down to 12, the boat's slowing down..
goes to what i said before; different tap points, and different gauges/recorders record different pressures.
During my boat build and the first outings the whole boat about shook my teeth out and sounded like major detonation. On another forum several of years ago bp illuded that my pump is probably cavitating. Further research revealed that the top of the pump is the area that cavitation will start as this area has the least NPSH (net pump suction head). Well as it turns out this is the very reason that pressure taps are located towards the top of the inlet housing.
After installing the pressure tap I found that pressure would build then drop to virtually zero then be all over the range. I changed loaders and tried different shoe configurations until I got a balance of speed and stable pressures. My optimum maximum pressure is around 35 psig.
With this said the pressure data is only a tool that each individual has to tune the pump, engine, and hull; nothing more. To compare pressures with other boats would be of little use except to get into a general pressure range. Every combination will net diffenent pressures at different power settings and hull angle of attack.
Unless you are running a serious competition venue I really don't see the need to instrument the pump discharge because changes on this end for a lake boat are unreasonable for cost vs. gain.
Timinator - I ran some quick numbers for nozzle velosity, mass flow, and NPSH to achieve the speeds your boat is going and there doesn't seem any way 12 psig works. With out a doubt your pump is taking water to the vapor state on the inlet side. the differential is simply too great. Are you running a standard PD nozzle or inserts?
Tom
Jak,Originally Posted by UBFJ #454
When you guys ran those numbers, did you have any issues with the suction peices breaking, cracks??
Willis
Last edited by shaun; 03-30-2010 at 06:51 PM.
We run lakes Pleasant and Bartlett here in central AZ. and have probably only run from a dead stop about 5 or 6 times in 3+ years. Usually someone comes alongside when I'm cruising at 35-40 mph and we hit it from there. If it went any other way here, I would set up for that. I also set up for what my customers ask for, and midrange roll-on is what they ask for. TIMINATOR
113 is no big number to you dragrace types, but for a regular 87 octane pumpgas fueled, 21' boat with the wife, cooler, and cruising around junk its not too bad. You see, my wife goes pretty much everywhere with me, she actually LIKES me, when we radar, we radar with her in the boat too, shes allways there anyway, and I fill the tanks on the way to the lake too (50 gal). I run the boat that way, I radar it that way. Its realistic. I know it would run faster with 5 gal of fuel and nothing else, but I don't run it that way. What good would it be to say it runs 118+, but then kick the wife out with the cooler, bimini top, etc. before I race? If thats how you race on the big river so be it. Now lets get back on topic. P.S. the wife is kinda chunky and that extra 40 gal of gas weighs 270 lbs too. How fast would it be by your standards? This is why I said to post what type of boat you are running along with the pressures. TIMINATOR
113 is no big number to you dragrace types, but for a regular 87 octane pumpgas fueled, 21' boat with the wife, cooler, and cruising around junk its not too bad. You see, my wife goes pretty much everywhere with me, she actually LIKES me, when we radar, we radar with her in the boat too, shes allways there anyway, and I fill the tanks on the way to the lake too (50 gal). I run the boat that way, I radar it that way. Its realistic. I know it would run faster with 5 gal of fuel and nothing else, but I don't run it that way. What good would it be to say it runs 118+, but then kick the wife out with the cooler, bimini top, etc. before I race? If thats how you race on the big river so be it. Now lets get back on topic. P.S. the wife is kinda chunky and that extra 40 gal of gas weighs 270 lbs too. How fast would it be by your standards? This is why I said to post what type of boat you are running along with the pressures. TIMINATOR
The fuel yes, The cooler mabey, But if the wife reads this you're a dead man!
Talk about pressure!
we race in "river trim" sounds like its tottally different than "lake pleasant trim".
you should come join us some time and see how 118 holds up, lake havi isnt far from big river.
btw, did you notice you had a cheerleader the other day? that njba donut club guy said he liked your work.
Posting Permissions
Reply With Quote