I want to make the Barham with a glug glug outlet. having heard about them but never seen one..... here is what I would do. Is this correct? The easiest way would be to simply solder a tube onto the correct sized outlet that came with the pump? Is there a recommended length?
thanks, That is what I thought. Short piece was a left over. Didn't want to solder on a piece that was too short.
my understanding is that by putting a large diameter tube above the restricter, makes the water "glug" out rather than the 10+ foot stream of water.
What exactly is a glug glug outlet and who named it that? Better get a clear definition before you make something different and call it one. I have seen several good ideas ruined for the masses that way over the years. Anybody made one and care to define it?
It's got to be more than a large diameter tube around the restrictor, because that wouldn't change the water flow (the jet would shoot right up the middle ). I saw one of these on David Ranier's ship but dammit didn't look close enough to see how it worked. <kicking self now>
They were on a few competitive boats at NATS last year. If you have ever watched a ship that is pumping hard, you can see the boat is actually getting pushed down into the water (that whole opposite forces dark arts mumbo jumbo). For me it was having 3/16 of freeboard and then turning on the pump only to have the ship get pushed under. Look in the frankenship build and you can see the tube (next size up from the diameter of the restrictor). Some will claim 15% or so efficiency gain (I have not seen any test data), but the lack of force on the boat works for me.
It is just that, and something has to happen (tech guys will explain what) because the pump stream is just like a water hose. Try it yourself
That was my concern. It is why I posted the picture and asked questions. Seems like it would just shoot up the middle. I need to make a longer "exit tube" . My concern is that it may be less efficient "glugging". I think I will run a test before permanently installing it in the boat. Maye someone already has and would like to post results???? Keith
I'm thinking it's a venturi effect. You're putting a larger diameter pipe right after the restrictor, so low pressure (atmosphere) after the nozzle would tend to pull the stream apart. Not sure... my fluid dynamics class in Nuke school was almost 30 years ago.
3" is what I use for the larger tube over the outlet. You can cut the original outlet down too, like 1/2" total with 1/4" in the larger tube. I just CA glue the tub on, held up so far... The claim is it puts out 15% more water. That's nice, but the real benefit is not listing your ship when pumping hard. Also you no longer spray all the guys on shore.
So how does that design cause the pump stream to expand and slow down? Maybe the drawing is missing some critical element? I don't see it working as advertised unless the stream is pushing through water trapped in the open end of the nozzle, which will most likely clear once it starts pumping hard, and resume the 30 foot tall second and third law death jet you were trying to avoid. Pumping into sanding water will reduce the nozzle's output significantly.
It should be a converging - diverging nozzle. The converging part accelerates the water gently so that it travels faster through the throat of the nozzle (the orfice for rules compliance). Then the diverging part acts as a diffuser, decelerating the water while increasing pressure. Unfortunately I can't tell you how long or what shape the nozzle should have, since all my tables are for compressible flow and supersonic speeds.
It works don't ask me how but it does. I make mine tapered from the large hose down to 1/8" then tapered back out to the large tube.
