Crazy Ideas

[Unchained]

To start a new thread other than the worthless one that has been going on for days I had a crazy jet boat engineering idea. Did anyone other than me notice the rescue boat at the drags that uses a fire hose hooked to the jet pump bowl? Even at idle that hose put out incredible pressure and volume.
Now if someone hooked four hoses of maybe 1" ID from the bowl down through the bottom of the hull on either side of the jet intake, it should provide a lot of lift at speed. Of course it would reduce bowl pressure but maybe the additional lift would more than compensate. Hey, I said it was a crazy idea, but anything is better than EM & D.
Any other crazy engineering ideas ?

[Hallett of a Dream]

Yup, crazy idea.

[LVjetboy]

Don't think it's so crazy. Although, as you mentioned, the pump losses may cancel the benefits. Here's an idea I floated on the other board:
A grid of fairly small holes in the bottom, then inject pressurized air through to reduce hull friction losses. These holes could be stategically placed on either side of the pump inlet and possibly angled in the direction of flow. Air pressure could be supplied by compressed gas cylinder or possibly engine driven air pump if it turns out that gains from hull friction reduction outweight air pump hp required.
Seems a fairly easy concept to try, just find a cheap used boat and experiment away. If it works, the market would be all boats not just jets. Hey, if anyone becomes a millionaire off this idea, cut me in ok?
http://free.***boat.net/ubb/smile.gif
jer

[Jungle Boy]

I didn't know LSD was still popular. Just kidding.

[Unchained]

LV thanks for the input. I considered that one too but didn't think that the air would provide as much lift as the water pressure. My earlier idea was to provide lift to replace the lift you get by over pressure in the intake when you shim the shoe down. From my experience shimming the shoe down gives you intake pressure and lift but also parasitic losses from the shoe dragging in the water stream and possible loss of control at high speed. A major trade off but the best way to get lift so far. I feel that there must be a better way, just no one has discovered it yet.

[Joker]

Hydrofoil with a vertically adjustable intake...like a four inch hose or something...imagine the rooster tail

[jroos]

Navy has a boat with experimental intake. It has a door on it. For a mine sweeper. Textron was toying with it and if I`m not mistaken has one built. to 100+ in just 6 seconds! A professor at UNO was on the team that developed it in the 70`s. I will find more about it this week. A friend of mine worked on plans for the pump and intake for it while going for his mech. eng. degree.

[froggystyle]

I knew it! Jroos, you are smart, huh?

[Hallett of a Dream]

What about having your exhaust come through several ports on the bottom to not only help lift, but "aerate" (SP?) the water in which the rear of the boat rides? Of course this would have to be behind the intake.

[gstark]

LVjetboy, your idea is neither crazy nor drug induced. If I am not mistaken, the MD F-4 Phantom uses a similar concept, and it is used in a flight control system called the Boundary Control Layer (BCL). Air bled from the compressor section is used to control the wing's characteristics, specifically the location of where the boundary layer exists and its thickness. I believe this system augments the BL in various flight regimes, particularily low speed high power settings.
We used to manufacture some of the high pressure pneumatic ducts for this system.
I haven't given much thought to the applicability of a system like this on a hull, on a wing undisturbed air flow with the proper characteristics is rather important.
The system you describe is the antitheses of Jim Hall's ground effects Chapparal of the late 60's early 70's during the McLaren-Hulme Can-Am years. I watched that car suck the ground and gain ground in turns. In a boat, the opposite effect would be desired.
Obviously, this is a pretty specific science, one that is probably best left to the wind tunnel folks. I do know a couple of them from B-2/F-18 and JSF, and I could discuss with them.

[jroos]

http://free.***boat.net/ubb/mad.gif Damn froggy, why`d ya go tellin` evryone?

[hot_rod]

Wouldn't this also cause aeration which would help in decreasing the wetted surface??
http://www.geocities.com/hot_rod20603/Hotrods_Jetboat_Page.html
http://www.bearshobbies.com/hotrods_signature.gif

[jroos]

Hot rod, when urinating into a prop, you better get a rain suit. And a face shield. Just a neighborly tip.
Nice boat! Who`s offshore rig called Attitude?
[This message has been edited by jroos (edited September 23, 2001).]

[FastDave]

It's a solid concept. Think of an air-hockey puck floating over the table; it glides effortlessly (or even a hovercraft). At speed, the water behaves more like a solid surface that you may think. The concept is dissimilar from the artificial-lift that can be created on aircraft wings to prevent a stall, but has its roots in the same thinking arena. You would definitely have to worry about cavitation, though. Unless... Picture a vertical-moving intake grate. It could 'push' down into the water by 6 inches or so when using full airflow beneath the boat. Small, computer-controlled airflow-control surfaces could be used to keep the attitude of the boat in-line with surviving the run.
Hmmmm... Where are my drill bits? Seems like it might work.
Still, maybe I should get another manual intake control like this one on my boat.
http://www.dpgdigital.com/LaborDay2/Im000090.jpg
FassssssstDave...
[This message has been edited by FastDave (edited September 23, 2001).]
[This message has been edited by FastDave (edited September 23, 2001).]

[skeepwerkzaz]

Maybe make the bottom of the boat like a golf ball. Same principal as the boundary layer theory. Vortex Generators? JATO? Variable pitch impeller ( actuated w/ oil pressure) Outriggers? Oars? Sled dogs with flippers? Very Small Rocks? Bread?
Duck feathers covering the entire boat?......

[spectras only]

Intrestingly, Campion Boats in Kelowna was[British Columbia]featured in an article a couple of years ago, to make their boats faster by putting holes http://free.***boat.net/ubb/eek.gifin the bottom and use a compressor to aerate the water.Wondered why haven't heard more about the project, I guess they figured putting steps,notches was more feasable.The less holes to pour money in the water ,is for the better http://free.***boat.net/ubb/biggrin.gif http://free.***boat.net/ubb/biggrin.gif http://free.***boat.net/ubb/biggrin.gif

[riverlover]

A few months ago we tossed around some thoughts about a variable vane pump that closes the nozzle a little bit at speed. Sort of like an after burner nozzle on a fighter jet (real big to get outta the hole then closes up a little for top end). I remember someone saying they saw a prototype but it never made it to production. Another one, that someone provided a link for, is in production. I e-mailed the guy that makes it but he never replied. Who knows?
Thinking about jets, this guy named Walt seems to know how to get a lot of proficiency out of a pump set-up. I heard he picked Greg Shoemakers brain for a few years back in the day. Here's a link to his site. He talks about getting more bang outta your pump. http://www.netfeed.com/~waltshbs/
[This message has been edited by riverlover (edited September 24, 2001).]

[LVjetboy]

Unchained, sounds like we're thinking the same direction, just different approaches. I'd love to see some innovation in this area...could be done with a low budget?
GStark, since we're both on the West Coast, maybe we could hook up some time...sounds like we have some common aircraft backgrounds and engineering interests.
FastDave, love the manual intake control! In fact, I need one for my next trip out to play with the secondaries...how 'bout a loaner? Just kidding...sort of :) The hockey puck idea is right on. Friction losses from water contact with the hull at speed is THE single reason why boats go so much slower than cars with the same hp. Reduce this loss and big time speed gain.
Spectras only, Thanks for the tip. Would love to see those results! I did a patent search and didn't come up with much. The step is ok but introduces a vacuum with the resulting cavitation losses that tend to cancel some (possibly most) of the gains. So seems like pressurized air would be the best friction reducer. Enough pressure introduced at the right location could cut friction losses in half. Imagine gaining 10+ mph with no increase in hp or cost in fuel. Could design a retro fit kit to put on existing boats or (probably best) build right into the hull during manufacturing. Just some thoughts.
jer

[custom-cruiser]

Here is the link again for the new pump technology. Variable intake grate and nozzle.
We need to bug this guy to put a trim device on this thing and he might have something http://free.***boat.net/ubb/biggrin.gif http://www.marinejettech.com/

[SB]

I had a 96 Kawasaki 1100 Zxi, jet ski that had a system that put air (bubbles) under the hull. I have no idea how much good it did. Top speed on that unit was probably 58 mph with 120hp.

[flat broke]

Sorry Hallet,
Using exhaust to blow your bubbles wouldn't do the trick. Talk to an I/O guy about running exhaust thru the prop to hear some stories about backpressure related hp losses(and thats with the vortex created by the prop rotation to aid in evacuation). Even if the exhaust pulse was strong enough to break the surface tension of the water and keep ya afloat, your motor would probably breathe like a 90 year old emphasema patient.
Chris

[FastDave]

This is getting interesting. How about a small jet turbine engine whose only job is lowering friction by streaming the pressurized air through many small golf-ball type dimples on the bottom of the boat? With the right design, the dimples should actually trap the pressurized air and 'push' against the water with the downforce of the boat.
Somehow I don't think just glueing a couple protable bathtub jacuzzi mats to the bottom of the boat is gonna do it. lol
FassssssstDave...
They'll say "Why is he so fast" and the answer will be "Cuz he's got dem dimples"!

[froggystyle]

Not to encourage you wackos, but a simple air conditioning compressor, drawing about 7HP with no load would bolt right to the front, and the only worry is to ensure that it stays oiled. An in-line air hose oiler on the intake works great. I used a rig like this to produce HP air in my Scout back in off roading days. Cheap and easy. All we need now is a hydrodynamics expert instead of aerodynamics to tell me where to drill the holes, and I will build a fiberglass manifold under my floorboards to plumb into. It would actually be pretty easy. Except then we will really catch s@#t from Barney about Hot Tub Car Boats. We would even have a bubbler!

[Unchained]

I think that the air bubbler would reduce surface friction and there is some merit to that idea, but it wouldn't provide any lift. I still think tapping into the bowl and using that water pressure blowing under the hull in a couple strategic places would provide lift. I know with my boat if I have it 1/2 way into reverse and rev up the engine it will lift the back of the boat up a couple inches at a stand still.

[fat rat]

I think tapping off the bowl....same principal as an aircraft tapping off for bleed air to operate sub systems would greatly reduce thrust at W.O.T., since we are only single stage and not multiple, unless you have a way of manually reducing your nozzle size to great more velocity.
What about a second pump (pwc) with its own power plant.....just a thought.

[skeepwerkzaz]

Bleed air eh, someone knows which side of the compressor the fuel control is on. Is it time to re-trim? Better get me 50 feet of flightline and a bucket of prop wash. I think we need a "constant speed" impeller. And fifty million dollars!!!!