venturi effect, nozzle design

[455maveric]

I think fire fighting nozzle would be the ticket it can go i think from dumping large amount of water to a fine spray. you wouldnt nedd it to go to the fine spray but just to the highest velocity

[speedboats]

unfortunately a variable orifice nozzle would reqiure alot of moving parts, and would be subject to alot of debris possibly fouling the function of it. Not to dishearten you, but you would severly limit your target market if you fail to address this problem. The top river race guys (like the baked bean can shown above) would be all over it like white on rice, but if the part was prone to fail everytime you run aground then it would be left on the shelf.

When I read venturi, the tool used by Airbus to fill their emergency escape slides came to mind, where a high pressure stream is thrust through the centre, then due to the venturi effect more air is dragged through the nozzle further increasing thrust.

The SR71 Blackbird had a cone in the inlet to vary the amount of air available to the engines at sub-sonic low altitude speeds versus super-sonic high altitude speeds...

Something else to think about...

[boatermike]

thanks oldsleekolds for the rr link, i read all 25 pages and was suprised that they were saying large nozzle for top speed small nazzle for hole shot. i wonder what the ftnozzle people feel about that? is it correct?

[OldSleekOlds]

thanks oldsleekolds for the rr link, i read all 25 pages and was suprised that they were saying large nozzle for top speed small nazzle for hole shot. i wonder what the ftnozzle people feel about that? is it correct?

There are at least a couple guys that have been there and done that....Duane being one of them. I certainly would have no reason to doubt what they are saying.

I think the guys running light boats and more that 500 hp are going to see the most gain with a nozzle that can be adjusted on the fly. The rest of us are probably not going to gain a lot no matter which nozzle insert.

I've been tinkering and reading for a long time. I have a machine shop so I can make whatever I want. If you wonder why jet boats are not efficient consider what needs to happen to make it go.

Water must be made to go up into the pump through a rectangular hole
The water is forced through a round hole that has an impeller in it
The impeller forces the water through the bowl which is kind of like a funnel
The water leaves the bowl and goes through a steering nozzle and/or diverter

Nothing new here....right? Think about how many gallons per minute your pump will put out at WOT. Now think about the weight of that water. That's what makes the boat go.

Now think about the weight of the water going through the pump PER SECOND. Now think about how much power it is using to change the direction of the water as it moves through the pump.....from rectangular to round......to smaller round (bowl).....to still smaller round (nozzle).

The only thing I can think of that could make a significant improvement in efficiency is to aerate the water going through the pump. Introduce air bubbles via venturi at the point where the water leaves the impeller if possible. Everything downstream of the impeller would need to be redesigned of course. The closer to the impeller the air enters, the greater the gain. The objective is to get a lot more water through the pump with the same hp. The boat will then go a lot faster with the same hp.

old

[show u one time]

Because the Government isn't paying millions of $$$ for someone to do it, and because of the numbers game. I, (as others I'm sure), have developed a nozzle that is an improvement over what's available out there today. But the cost of producing is is too high to be able to ever recover the initial investment. Simply put; there are not enough people who would pay the price that the product would cost to ever make anything above the development cost. It's just like the Jetaway, it took me nine (9) years of sales just to recover the cost of developing and producing the Jetaway. If there were three million people out there that would buy the nozzle once produced, and you could spread the cost out over that number, I'd do it tomorrow. In actuality, I doubt that there would be more than three hundred people that would ever buy one. This makes the price per piece unreasonable. I am working on trying to figure out a less expensive way to produce them, but at the present, it looks the cost would be somewhere around $1,200.00 or more per unit. And that's just cost, it includes no profit to recover the investment. I've already invested over $7,000.00 in materials, machine work, designing costs and that's not counting anything for my two years of time making the parts and testing the prototypes. If the economy had not turned sour, I'd probably be a little more likely to gamble. But with our new leaders paying people to destroy the big engines and over taxiing our fossil fuels out of existence, we may all very well have to learn how to run our jet boats on hydrogen and electricity. You think $1200.00 is high for a nozzle housing, think of the price of an extension cord long enough to run the 1/4 mile. (smile). Who knows, maybe Boatermike is on to something big here. A $69.95 bondo/epoxy/whatever do it-your-self nozzle kit would sell like hot cakes on these forum boards, (if it worked). I say; "Boatermike, pursue your dreams."

the day i win the lottery, thats the day ill call ya duane, lol, then well get down and busy and spend some cash reinventing the nozzel, all in fun of course!

[boatermike]

i guess with that kind of funding you will also work on a variable intake to work in conjunction with your variable nozzle and variable impeller

[Duane HTP]

I'm with Ya on that one. If I win first, I'll already be on it. I love this S***!
Hmmmm, the board won't let me spell out Stuff??
Duane HTP

[boatermike]

might as well throw in a 2 speed transmission also

[show u one time]

the sky will be the limit boys!!!then,,,, we will hafta go testing in a tropical enviroment! and while were at it,,we could also???,,,,

[boatermike]

go to a all u can eat buffet? ha ha

[sleekcrafter]

Back in the day, they ran chokes in the nozzle, on the launch.... The chokes were then spit out for the big end. Then they figured that was kinda exspensive, and settled on a selected insert.

[Duane HTP]

I remember those days. We used to do it. I was always afraid of hitting a v-drive behind me with one of the released inserts. Ha Ha, Just having fun.

[455maveric]

now i am totaly confused i thought large was hole shot and small top end more velocity high speed ,volume hole shot

[Duane HTP]

It is confusing. Lighter boats with very high HP react opposite of heavier boats with lower HP. There's a crossover in the equation somewhere. Your job is to find the right one for your boat and Yes, it can be confusing. It's not like going to a chart and reading which nozzle your boat should use.

[455maveric]

Ok i started to think about this . would it be best to have a larger pump to move more water and then you could have a larger nozzle to keep the back pressure down but just large enough to get the best water velocity out the nozzle