Ditchable weights...are they needed and is there a minimum?

[JeffG]

Scuba Cylinder Specification Chart from Huron Scuba, Ann Arbor Michigan

LOL


Heiser 190

Dry land weight (empty) 87lbs
Buoyancy Empty, lbs -46.86


It is a monster. Why would anyone use these things?

 

[Charlie99]

Scuba Cylinder Specification Chart from Huron Scuba, Ann Arbor Michigan

Although there are several Heiser tanks listed on that site (which happens to be my favorite for tank info), it doesn't have any info for the Heiser 95 that the original poster is using. Nor does http://www.tdl.divebiz.net/pub/tanks.html

 

[BlueDevil]

Neg 46.86lbs when empty!! I think we have definitely found the source of the problem. Unfortunately the solution is to get rid of this tank you have just bought and get a Faber instead if you want to dive a steel.

As far as thick wetsuits go the air environment can be a factor in choosing a wetsuit over a drysuit. Where I dive it is possible to have reasonably cool water but very hot air temperatures. For example the water temp could be in the 18C (65F) range, with air temps of around 35C to 40C (95F - 104F). The water temp requires a reasonable amount of thermal protection, but the air temp makes it very uncomfortable in a dry suit. Even if you wait until the last minute to put the drysuit on by the time you have got all your other gear on and are ready to jump in you will be sweating like a pig and just about to collapse from the heat. At least with a wetsuit if you are getting overheated you have the option of jumping in, letting some water in and cooling off for a few minutes - in a drysuit jumping in for a few minutes will barely cool you at all (and you sure don't want to be letting some water in!).

 

[Teamcasa]

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[Clammy]

Yes, something is definately wrong here...and I'm confused myself...

I normally do bob on the surface with the AL80s [or steel 80s and 85s for that matter], 14lb on weight with 10 on backplate. But not today with the new tank.

I purchase a used tank last night - steel 95 Heiser Beuchat - was short and squat just as I like it as I'm only 5'3. Buddies and I were in the water trying to surface swim out to buoy this morning. I started swimming out, otter-styled, and noticed that despite having a fully inflated bc, I only my face was on the surface. The rest of me was underwater. Yelled out to buddies that something was wrong. We came back to about 5ft of water. We all thought I was overweighted and my fully inflated bc was not able to "lift me" to the normal head and shoulder out of water position. So we started taking out weight off my belt and tried to see if my head and shoulder could get in the normal out of water position. We ditched all of my ditchable weight and I was still only to get my face on the surface, though my body was higher up towards the surface. Ended up swapping tanks with a buddy who could handle the weight on his wing.

So for clarification:
I have 30lbs of lift on wing. It is a DSS 30 LCD.
BP is about 5lbs.
BP has another 5lbs screwed in.
My weight belt has 14lbs.
I weigh 120 and wear 2 piece wetsuit.
No other neg buoyant equipment.

When we ditched all weights on belt- result- only face was on surface with a fully inflated bc.

So does this mean I need to take the 5lb screwed plates on backplate? If so, it will probably just get me to the normal head and shoulder out of the water position. And leaves me with no extra weights.

Or does this mean that I just can't dive this tank because it is too heavy for my wing?? It seems that if I dive this tank I'll have to do it without ditchable weights. Is this even recommended or advised?

Diving the AL80 is a completely different issue- as it seems that I keep on whittling down the amount of ditchable weights I have [and have been overweighted]. Though I'm at 10lbs now, but can ditch perhaps another 2. Which leaves me at 8lbs. At 8lbs- and if I get a canister light [-2 or -3] and jet fins [-1], I'm at 4-5lbs of ditchable weights - provided that I don't shed more weight.....is 4-5lbs sufficent amount of ditchable weights?

To answer your question some what more directly, your tank is I think roughly -7lbs EMPTY. This is why you are grossly over weighted. Heiser and Faber Tanks are very negative when empty which is nice if you want to take weight off your waist.

With your rig, you have 24lbs (10 on your back and 14 on your waste) and then an additional 7lbs on the tank and that's only if it's completely empty! That puts you at -31lbs!! Some of this is offset by your 14mm wetsuit but you are now very close to the 30lbs of lift that your wing provides.

If you remove the weight belt completely, you are still at -17lbs with that tank and actually more considering you won't be breathing it down to nothing... hopefully...
The Heiser 104 is over -15lbs when full. I'm guessing your tank isn't THAT much different.

Anyways, there are some things that haven't been taken into consideration in my quick number slinging up there (like wetsuit and your body buoyancy) BUT the point is, you're really over weighted. On a 7mil with a steel 100 that's -2 empty, I dive with 16lbs total to be neutral and I'm 170lbs. But that's me. I would seriously consider removing that bolt on weight from DSS, drop like 8lbs off that belt and start your weight checks from there!

 

[Clammy]

Neg 46.86lbs when empty!! I think we have definitely found the source of the problem. Unfortunately the solution is to get rid of this tank you have just bought and get a Faber instead if you want to dive a steel.

As far as thick wetsuits go the air environment can be a factor in choosing a wetsuit over a drysuit. Where I dive it is possible to have reasonably cool water but very hot air temperatures. For example the water temp could be in the 18C (65F) range, with air temps of around 35C to 40C (95F - 104F). The water temp requires a reasonable amount of thermal protection, but the air temp makes it very uncomfortable in a dry suit. Even if you wait until the last minute to put the drysuit on by the time you have got all your other gear on and are ready to jump in you will be sweating like a pig and just about to collapse from the heat. At least with a wetsuit if you are getting overheated you have the option of jumping in, letting some water in and cooling off for a few minutes - in a drysuit jumping in for a few minutes will barely cool you at all (and you sure don't want to be letting some water in!).

That's for the 190!!!! at 4400 PSI!!

 

[Bill_PNW_Diver]

Although there are several Heiser tanks listed on that site (which happens to be my favorite for tank info), it doesn't have any info for the Heiser 95 that the original poster is using. Nor does Scuba Cylinder Specifications from Tech Diving Limited - 928-855-9400

Heiser 104 2400 +10% 104 8 27.36 47.4 -7.46 -15.26

The 104 is a 95 with the "+" raiting

Doing the math you can see where the problem lies.

One of my buddies who is a commercial diver had a Hesier 120 he used for work. Probably not a good choice for the OP.

EDIT:
Hey Diverchk, I just noticed you are in my neck of the woods. If you would like try out different tanks to see what works for you, I could set you up with an Faber LP95, HP119, HP100, or an HP80, just shoot me a PM.

 

[BlueDevil]

That's for the 190!!!! at 4400 PSI!!

OOps...sorry. I thought that the figure quoted was for the tank in question that was being used in this case. I should have checked my facts when the value quoted seemed so extreme. I shouldn't have made assumptions!

 

[Mr Carcharodon]

divechk

Have you done a weight check lately? I suspect you are significantly over weighted if you can not get to the surface with a fully inflated wing. I suspect you will need somewhere in the range of 10-16 pounds total and you have 23 pounds now. Try taking 2 or 3 pounds off per dive and do a weight check at 15 fsw with a near empty tank on every dive you can. It is better to be slightly overweighted than underweighted but if you are 10 pounds overweighted that is a real problem that if you fix will make your diving much better.

To answer your original question it is a good idea to have enough ditchable weight to get the surface at the heavist point in your dive. Assuming you have your weighting figured out that means you should have about 6 or 7 pounds of ditchable weight to offset the weight of the air in your tank. Since you already have a 6 pound backplate that would give you 12-13 pounds total which is probably close to what you need based on your body weight. There is some indivigual variation so you weighting maybe 3 or 4 pounds higher or lower.

You probably do not need the 5 pound weight for use with a wetsuit. But hang onto it in case you move to a drysuit someday.

 

[divechk]

Some drysuits have come down in price. (Like the Bare Next Gen).

Yes. Sad but true.

Drysuits are particular on sizing. I've been looking for one since August. Have not found something that would fit me. As a lady's small is still large on me. Its a work in progress if I don't want something custom or too spendy.