The use of air

[Frosty]

Immagine a 1inch PVC pipe fastened some how to the bow of a dinghy. You attach a 90 degree elbow facing back to the bottom of the pipe. The top is open and above the water line at all times. The elbow is approx 2 feet under.

Disregarding bending pipes and bow rise, the dinghy goes along at say 10KTS (not critical) will air flow from the elbow through the pipe being fed from the air above the water line?

It is my feeling that air will flow out of the elbow, (sucked out), a flared elbow if necessary.

It is this theory that I am expecting to produce airiation under the hulls.

[kach22i]

Originally Posted by jack frost

Immagine a 1inch PVC pipe

I think the intent is to engage as much surface area/plane area as possible. A simple point or nozzel of air will quickly detach from the hull's surface and the air supply will wander off useless.

[Frosty]

Yes I agree. The simple explanation above was to determin if the air would come out of the elbow.

My Idea is only based on this principle. If you accept that air would be drawn down the pipe, I would use a half pipe ie a pipe cut in half down its length and placed in front of the bow, this is what I refered to as the 'false bow'. This ofcourse would extend up and above the water line at all times.

This pipe would then as the speed increases cause depression behind it and draw a mass of air down from the surface. I am of the opinion that the reall bow and the bulbous bows would therefore be mostly in extruded air from this feeder 'false bow'

Is not the exhaust gasses from a through hub propeller encouraged from the engine by this method?

[kach22i]

Originally Posted by jack frost

My Idea is only based on this principle. If you accept that air would be drawn down the pipe..................'false bow'

Is not the exhaust gasses from a through hub propeller encouraged from the engine by this method?

1. I think the "principle" you are looking into is slightly off target, but very worth lookng into - a new one to me. However please don't give up on the concept of pumping air via mechanical means - and lots of it.

2. Your "false bow" is different than what I first thought you meant. I would call what you propose to be a leading edge treatment, like airplanes have on their wings.

3. I'm really not a true "boat guy" and have not seen or heard of a through hub exhaust, sounds interesting, very interesting. I know, hard to believe- I've never owned an outboard.


http://www.zenithair.com/stolch801/design-tail.html


http://www.nissanmarine.com/products/6_4_features.html

[Frosty]

Your very good at putting in pictures!! Wish i could do that.

Yes the outboard motor effect is exactly how I intend to feed the leading edge with air. As long as the top is always open and above water I feel that it will draw air down.

If it does not work and i have to start to design some high volume(and It would need high volume) pump then I will abandon the idea.

Oh sod it I will try it on the dinghy first thing in the morn.

[kach22i]

The outboard motor takes in air and exhausts air after the combustion cycle. In affect the outboard motor is acting as an air pump in the example above. It's not fair to compare it to "ram air" caused by foward motion.

I think your experiment will result in water being forced up and out of the pipe, be prepare to get wet.

In our grade school swimming pool we had this long aluminum tube which a cleaning tool could be attached. We would take the empty tube/pole and put one end in the water and while standing on the side of the pool pump up and down the pole in the water. We would then judge who was able to get water to shoot out the other end (top) the farthest. I suspect the action of the waves will have much the same affect.

PS: Google "image" search.
http://images.google.com/imghp?hl=en

[Frosty]

If the elbow on my PVC pipe were to face forward then yes ofcourse water will come out by the pressure of water trying to get into the elbow.

But the elbow is facing backwards and its trailing edge will have a depression there. If the depression is more than that of the water pressure on the elbow at 2 feet then we will have a flow.

[kach22i]

Originally Posted by jack frost

If the elbow on my PVC pipe were to face forward then yes ofcourse water will come out by the pressure of water trying to get into the elbow.

But the elbow is facing backwards and its trailing edge will have a depression there. If the depression is more than that of the water pressure on the elbow at 2 feet then we will have a flow.

Please video tape this and post it on Google or You-Tube.

[yipster]

water ventury, the more water flows true, the more air vacuum on the side
penalty is drag but at some speed it may work without motor for ventilating

[Quicksilver]

why not test this with a bendy straw in your bathtub, probably would prove or disprove this theory pretty quick. I don't have a straw on hand so I cant do it myself.

In my opinion, I don't think it would work, it may produce bubbles, but not near enough to use on a real boat. Pumps however I do believe would work. I had a question about that design on the first page. I see air curtains on the sides, but is there another curtain directly under the hull as well.

Another thought, due to the recurrent opinion that the ship would sink. I don't think it would sink, but couldn't one use lifting foils to counteract any tendency for the ship to lower in the water or would this just produce drag negating the positive effect of the bubbles.

[Frosty]

Quick silver I think you might be pulling my leg but Ille bite any way.

Straw in a bath tub!!! Any way I had a go last night running up and down the dock with a hose pipe bent to an angle of 90 degrees taped to a stick,it didnt work, I put a funnel on it-- i think it was trying to work.

The biggest problem was achieving speed enough to cause a big enough depression.( a funnel is hard work to push through the water on a 6 foot stick).

I dont think airited water will make you sink otherwise you would not be able to drive a boat over another speed boats wake.

I think it more likely that the boat would become more bouyant with the clinging air bubbles to the hull.

[kach22i]

Originally Posted by jack frost

Any way I had a go last night running up and down the dock with a hose pipe bent to an angle of 90 degrees taped to a stick

Sounds like you had more fun than me last night.

[Frosty]

kach
Well I thought there was no one around, but, the guy on the boat opposite was.

Korean I think, any way he just politely watched as I tried to look scientific,-- you know rubbing your chin and saying things like mmmm and ahhh!!


I saw some guys in white coats in that area later-- you dont think!!!!!

[kach22i]

Originally Posted by jack frost

I saw some guys in white coats in that area later-- you dont think!!!!!

Yes, they are watching you and stealing your secrets, they even told me so.