Testing my new BP/W

[sharpenu]

I ordered all the parts for my new BP/W last week. They came in yesterday and I assembled everything in a little over an hour. I took it to the pool today to do some testing. Aside from a minor trim issue, which was corrected by moving the wing up one hole on the hammerhead plate, all looked ok.

The odd part was the weight issue. I threw in the black diamond and the bp/w for some comparison. The Black diamond, it turns out, is 2 pounds positive. The BP/W setup is about 4 lbs negative. Is a 6 pound difference normal? That seems high.

Anyway, that means I can dive saltwater with no weight. In the pool, I was able to be neutral at 4 feet with an empty (300 psi) AL63. Since the AL63 is +1 and my steels are about -1, I should be good.

I will be testing it in the ocean on saturday.

 

[pdoege]

The beauty of the BP is that you don't need much weight. Even less so with steel tanks.

They rinse really easy too.

Peter

 

[ranger]

I have a black diamond and I am surprised it is only 2 pounds positive. I've also gone to a backplate and would almost give the black diamond away, because it will just hang in my garage unless I do a private class and a student uses it.

 

[halocline]

The BP/W setup is about 4 lbs negative. Is a 6 pound difference normal?

Just out of curiosity, how did you determine that it's 4 lbs negative? It's easy to test the positive buoyancy of a BC, just toss weights in the pocket until it's neutral. But what kind of test is there for something that's negative? I suppose if it were a regular shape, you could weigh it, calculate the volume of water it displaces, then subtract that. I guess if you had a large graduated cylinder, you could measure the displacement. But, are you just kind of "guessing" the actual negative buoyancy based on it's weight? Don't get me wrong, I'm not trying to nit-pick; I'm sure a guess could be pretty close, but I would be interested if there's a way that I'm not aware of.

 

[sharpenu]

Attach an empty 1 gallon jug to the setup you want to measure. Add weight until the entire thing is neutral. Since water weighs about 8 1/2 pounds per gallon, an empty 1 gal jug is +8.5.

If it takes 4 pounds to make the set neutral, then the remainder of the jug's bouyancy is offset by the negative weight of the wing, or 4.5 pounds.

 

[halocline]

Attach an empty 1 gallon jug to the setup you want to measure. Add weight until the entire thing is neutral. Since water weighs about 8 1/2 pounds per gallon, an empty 1 gal jug is +8.5.

If it takes 4 pounds to make the set neutral, then the remainder of the jug's bouyancy is offset by the negative weight of the wing, or 4.5 pounds.

Very nice trick, should have thought of it myself!