"Venturi Effect" (Using the Laws of Physical Phonemes Instead of Sinking)

[Deep_Blue]

Venturi Effect, definition:
A tube mounted in the water line so as to cause a restriction of flow. The constriction causes a change in velocity of water flow through the tube, resulting in a pressure drop at the suction port that is proportional to the flow rate. This negative pressure or vacuum can be used to pull water out of solutions tanks.

The Venturi effect is used in a carburetor’s jet. As high velocity air passes over the jet, liquid fuel is pulled out of the jet via the lowered pressure.

Well... my findings are that if your vessel is taking on water. And your bilge pump can’t push enough water to counter the taking on of water. you can (and only when you are moving at high rates of speed while trimmed correctly) remove the drain plug in your bilge and water will be sucked out of the bilge by the lowered pressure of the moving water around the outside of the transom.

Agreed?

 

[bjcsc]

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While that is true, I think if you pull your drain plug on plane, the drain hole is above the water's surface and the only physics you really need are those of gravity...what you describe is how scuppers work in small boats like Sunfish, etc...not sure what you're driving at...

 

[tmcalavy]

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Don't know about doing this with the plug pulled, but my 73 Ebbtide trihull had a tube device that laid one end (inlet) in the bilge and routed water out the back by the whale tale using what looked like surgical hose. Was very handy, every time we moved at speed the bilge sucked itself dry. And we didn't pull the plug.

 

[Silvertip]

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If the bilge pump can't keep up with the incoming water, you'd best be reading a book on "how to swim". A device operated by engine vacuum would soon be inoperable since the engine would also be under water.

 

[bassboy1]

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bjcsc, I dont think the drain plug is above the water on plane. that would mean that you are only running on the OB skeg. The boat is moving so fast that the water that it displaces cannot reach the transom fast enough. therefor the water in the bilge is sucked out to fill the space.

 

[Bondo]

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Up until the time I bought a I/O,............ That's the Accepted way to Drain a Boat.........

Ever since my 1st rowboat that had a motor,.... I've Drained the Boat by Pulling the Plug,.......
At Speeds of course,.....
2 or 3mph Won't do it,........ But,.....6 or 7mph Most Certainly Will..........

 

[xtraham]

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yep thats how we used to drain the water out of old leaky wooden scows, pull the plug while under way

 

[Prin]

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In the old days we used to run our wood boat with the plug out all the time when we were water skiing. It leaked so bad that it was necessary to drain it by pulling the plug while underway. When a skier was finished someone else jumped in we took off again. The water that had come it then drained out (Of course we had to be pretty quick). Just remember to put the plug back in before you stop or slow too much. The process does work quite well.

 

[studlymandingo]

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Several old ski boats used a scupper instead of a drain plug; closed when at rest, open and draining while underway.

 

[Tail_Gunner]

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Umm maybe gravity feed?...................:}

 

[Deep_Blue]

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Umm yea, gravity feed with the assisted negative pressure of water flowing around the drain = much added GPM flow rate.

 

[Deep_Blue]

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Sorry if this post seemed a little odd, but it saved my azz the other day and I thought I would share it with you guys but seems its a little more popular that I thought.

 

[tashasdaddy]

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i boats sells a self bailer, which works on this principle, it basicly is a thru hull fitting that has a plug that moves in and out, when the boat is at speed it opens and drains the boat, back in the 60's and 70's they were very popular with the water ski croud.

 

[bjcsc]

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bjcsc, I dont think the drain plug is above the water on plane. that would mean that you are only running on the OB skeg. The boat is moving so fast that the water that it displaces cannot reach the transom fast enough. therefor the water in the bilge is sucked out to fill the space.

I think we're saying the same thing in a different way. I didn't mean above the waterline, just above the water that's there as you described. I think gravity plays a bigger role.

 

[Texasmark]

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Man, I agree with Silvertip. If you are taking on water like that on a regular basis I think I would stay on land.

On physics. The water in the boat and the drain plug, on a conventional drain plug located in the transom at the lowest point, are at equilibrium; both traveling at the same speed. Hence there is no physical activity, other than gravity caused pressure on the transom caused by the height of the water ( about 0.5# per foot of depth).

Removing the drain plug, while underway on plane, on a planing hull, provides a gravity exit for the trapped water and the water will exit at the same rate as it would under identical conditions while sitting on the trailer. But when it hits the water coming out from under the boat it hits it at the boat's velocity; but that is a mute point.

Mark