DePersia Bailer

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DePersia Bailer

Postby bilbo » Mon Mar 27, 2023 11:21 am

I know they've been talked about before, but are there any tricks to getting this bailer to work? It's never worked on my boat. I thought maybe it was just corroded, so while doing other repairs I took it out, descaled and cleaned it, and reinstalled. In the process I lost the little ball that was inside, and it let in 3 or 4 inches of water after launching because I forgot to close the drain. No big deal I thought, we can just open it up while underway and it will drain all the water out. No matter what speed we were going, motor or sail powered, flat or heeled, all it did was un-bail water. There's really no moving parts or adjustment on this thing, so I don't know what I can do with it. I have a mini bleach jug that takes care of the water but it really bothers me that I can't get this to work!
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Re: DePersia Bailer

Postby GreenLake » Wed Mar 29, 2023 1:35 am

The bailer is supposed to work based on Bernoulli's principle, that states that water flowing in a restricted pipe (or around an immersed object) speeds up and has lower pressure. And the way the scoop is oriented with the opening facing aft should only make that work even better.

So if you effectively have an "unbailer" then the cause must be that the water pressure is higher outside than inside.

When the boat is stationary, the "unbailing" should stop the minute the water level on the inside is the same as a the water level surrounding the boat. I would expect that level to be at or below the level of the level of the cockpit sole in a DSII, unless the boat is very heavily loaded. If you then start moving the boat, the level should drop. How far it drops would depend on the speed.

However, I could imagine a situation where the boat is so stern heavy that the drop in water level gets to be more than the pressure differential available from the movement of the boat. In such a situation I would expect the water level to drop some, but not all the way.

What I would not expect is the boat filling all the way. There's just too much enclosed air volume under the cockpit for that to happen. (It's probably worth making sure that the boat isn't taking on a lot of water between the hulls, because in that case, you are relying on the air above the cockpit floor - and below the coamings - to keep you afloat.)

Now, if you mount the scoop with the opening forward, you get positive pressure from the water pushing into the opening. Essentially, you turn your bailer into the kind of scoop used by fire fighting aircraft. I think you would know.

In summary, from afar, I have no definite conclusion, but if you observe a steady state: some water comes in but then it stops and the level changes (goes down with increased speed), then the bailer is fundamentally working and I would look at whether your boat is super stern heavy. If the flow doesn't stop, I'd suspect massive amounts of water in the bilge.

One test to perform would be to open the plug on a stationary, but empty boat. That should give you an idea what the level of the surrounding water corresponds to in terms of height above/below cockpit sole on a DSII. (I think it should be below, but it's been a while since I've seen a DSII in the water).
~ green ~ lake ~ ~
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Re: DePersia Bailer

Postby bilbo » Wed Mar 29, 2023 6:59 am

GreenLake wrote:
However, I could imagine a situation where the boat is so stern heavy that the drop in water level gets to be more than the pressure differential available from the movement of the boat. In such a situation I would expect the water level to drop some, but not all the way.



Thanks Greenlake, this may be the case. I was sitting at the stern so quite a bit of weight there. Next time we try this out I'll move up after opening the drain and see if that helps.
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