Reply With QuoteYup, crazy idea.
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 ?
Yup, crazy idea.
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
I didn't know LSD was still popular. Just kidding.
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.
Hydrofoil with a vertically adjustable intake...like a four inch hose or something...imagine the rooster tail
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.
I knew it! Jroos, you are smart, huh?
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.
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.
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