Buoyancy of USD backpack

[aquaregia]

I'm about to go diving with my USD backpack. Usually I use an aluminium plate and I'm wondering what I should add for the plastic backpack. My buddy will have a wing, so I'll probably overweight him to give me options, but I'd like to get close. Any ideas?

 

[DaleC]

Perhaps only a pound or two

I dive an ABS bacpac and don't notice weighting to be an issue.

 

[elmer fudd]

It should be just about neutral. Some plastic sinks and some floats, but it doesn't sink very quickly or float very well.

 

[Paladin]

Toss the thing in the bath tub (without a tank) and see if it floats. If it does, give it a chance to fill with water, then add weight until it sinks.

 

[aquaregia]

Man, my Walter Kidde tank is significantly lighter than my USD tank.

I've used 6lbs with an Al BP with LP95s and LP108s for 30' or so. I stuck on 10lbs with this backpack and the WK tank and was fine down until the mid 50'ish, and was able to hold a 10' stop on the way up. At 60' I could barely stay off the bottom. For the second dive, I switched to my USD tank and was having trouble staying off the bottom at 30'.

Thanks for the help!

 

[Paladin]

Man, my Walter Kidde tank is significantly lighter than my USD tank.

I've used 6lbs with an Al BP with LP95s and LP108s for 30' or so. I stuck on 10lbs with this backpack and the WK tank and was fine down until the mid 50'ish, and was able to hold a 10' stop on the way up. At 60' I could barely stay off the bottom. For the second dive, I switched to my USD tank and was having trouble staying off the bottom at 30'.

Thanks for the help!

I have three of those old WK tanks. Yeah, they are lighter than my other steel tanks and have a tendency to float and this means adding more weight to compensate. My other steels, mated to my USD back pack, will drop straight to the bottom, even at low pressure. The same back pack with a WK and I have to add a couple pounds to get it to act right.

 

[aquaregia]

Glad it wasn't my imagination.

 

[knowone]

8oz negative is buz. Unless you swim fast and the water comes out.