Drysuit weighting - this seems crazy?

[stuartv]

I have read what I could find by searching here. It seems like the norm for a person in a drysuit is to be carrying at least as much weight as they would in a 7mm wetsuit, and usually more. I saw numbers that were ranging from 20 to 40 pounds of ballast for people in a drysuit.

I just got my first drysuit and have done 2 pool sessions in it. The suit is a Bare XCS2 Tech Dry, which is 2mm crushed neoprene. With my drysuit on, Hollis F-1 fins, an HP100 tank, and a 6 # SS back plate, I am actually overweighted!

The first pool session, I had on 2 pairs of thick socks, shorts and a t-shirt. I ran the tank down to 400 psi and, from the surface, with an almost empty tank, I could still dump the air in my BC and drop right to the bottom.

The second session, I was wearing 2 pairs of heavyweight wool socks, thick polyester warm-up pants, and a t-shirt, and it was basically the same.

I'm going to the quarry (38 degrees at the bottom - though I don't think I'll be going to the bottom) this weekend. I expect to add expedition weight polypro long john pants and shirt and a Merino wool top. I have the impression that's all I'll need? If I need more, I think the most I would need to add is my North Face Polartec (300, I think?) fleece. Even if I add ALL of that, it doesn't seem like THAT much. Not enough to warrant adding even 20 pounds of ballast, much less 40.

Is it? Am I, as some of you suspect, really that dense? Or will adding some polypro long johns, a midweight sweater or a thicker fleece really add THAT much buoyancy? Will the difference between pool temps and quarry temps have me adding that much extra air to the suit? Adding that much extra air, to require 20 # of ballast, sounds like it would make swimming in the suit and preserving horizontal trim a real PITA!

Is it just that most of what I read about the weight people need is based on people using tri-lam suits and they really do take that much more weight? Gads!

Thanks for any insights!

 

[tbone1004]

keep in mind that your system is already about 10lbs negative, but most importantly think of it this way

wetsuits have finite buoyancy characteristics, while they lose that at depth, they can only ever have so much at the surface.

drysuits change significantly. My trilam suit requires less ballast than my 5mm if I'm in the caves for short dives, but slightly more if I'm doing decompression. It requires a whole helluva lot more if I'm ice diving. Inherent buoyancy of the suit is essentially 0 because it is a bag suit, so the only buoyancy is the neoprene socks and collar which are basically 0. In a pool you probably had very little air in the suit, this is independent of your undergarments, in 38F water you will be adding air to the suit to help those undergarments bulk up and actually provide insulation. Many people doing the very cold water diving have their suits inflated quite a bit, those of us diving 70F caves generally leave them essentially squeezed to reduce drag and to prevent us overheating.

I have 3 different weighting scenarios for my drysuit as mentioned above, it's not like a wetsuit where you can only have 1 weighting scenario for that particular suit.

 

[stuartv]

keep in mind that your system is already about 10lbs negative, but most importantly think of it this way

wetsuits have finite buoyancy characteristics, while they lose that at depth, they can only ever have so much at the surface.

drysuits change significantly. My trilam suit requires less ballast than my 5mm if I'm in the caves for short dives, but slightly more if I'm doing decompression. It requires a whole helluva lot more if I'm ice diving. Inherent buoyancy of the suit is essentially 0 because it is a bag suit, so the only buoyancy is the neoprene socks and collar which are basically 0. In a pool you probably had very little air in the suit, this is independent of your undergarments, in 38F water you will be adding air to the suit to help those undergarments bulk up and actually provide insulation. Many people doing the very cold water diving have their suits inflated quite a bit, those of us diving 70F caves generally leave them essentially squeezed to reduce drag and to prevent us overheating.

I have 3 different weighting scenarios for my drysuit as mentioned above, it's not like a wetsuit where you can only have 1 weighting scenario for that particular suit.

Understood. Thanks, Tom. Clearly, I will just have to go try it and see what happens.

I have 12 pounds of ballast I can easily add. If I need more, I'll have to buy some more weights.

Based on what you said, am I correct in thinking that one way of looking at it is that the amount of ballast you have determines (to an extent) how much "insulation" you can "inflate" into you suit? Meaning, the consequence for me of not having enough ballast is that I will be cold because I can't inflate my suit enough?

In that case, I should be safe to go, only prepared to add 12 pounds. Worst case, I'll be cold and need to buy some more weight, so I can add more air to my suit next time. But, I'll be safe with that much - assuming, of course, I cut my dive(s) short as necessary to keep from getting TOO cold. It won't be unsafe in the way that diving underweight in a wetsuit would be (i.e. concerns about not being able to hold a safety stop).

 

[TSandM]

Lead IS warmth, but there is only so much that you can compress your insulation, as a practical matter. If you are carrying insufficient ballast, you will have difficulty staying down, no matter how hard you try to shrink-wrap the suit.

I have found that I have about a five pound area of flexibility (learned by forgetting to put my cambands weights in and diving anyway ). I can run my suit very tight and make up for the loss of that much ballast, but any more than that, and I'm unmanageably light. And diving with the suit that tight is both uncomfortable and cold.

I use 31 pounds of ballast (including the plate) with my undergarment alone, and I have to add at least 2 pounds if I put on the heating vest.

 

[tbone1004]

essentially correct. That is why I have my suit for comfort, wing for buoyancy. In a technical dive I will conduct the dive in a suit squeeze, and then inflate at deco. That can mean one of two things, hanging extra weight where I dropped my deco bottles, or just carrying it and using the wing to offset during the dive. For weighting now, you know that your rig allows you enough ballast in those conditions, so go for the dive, and drop a weight belt on a shallow platform with the weights only threaded through one end. At the end of the dive when your tank is 500psi or so, go down and hold onto the belt and deflate your wing 100% and inflate the drysuit to where you are comfortable temperature wise. Remove weight from the belt until you are neutral and that is your weight for those conditions.

 

[RJP]

I have read what I could find by searching here...

I just got my first drysuit and have done 2 pool sessions in it... I am actually overweighted!

The first pool session... drop right to the bottom.

The second session... it was basically the same.

I'm going to the quarry this weekend. I expect to...

I have the impression...?

If I need more...

I think the most I would need to add is...

Even if I add ALL of that... it doesn't seem like THAT much.

Not enough to warrant...

Is it?

Am I, as some of you suspect...

Will adding... add THAT much buoyancy?

Will the difference... have me adding that much extra air to the suit?

Adding that much extra air...!

Is it just that...?

Gads!

What advice did your instructor offer during these two sessions, or regarding suggested weighting at the quarry?

 

[stuartv]

What advice did your instructor offer during these two sessions, or regarding suggested weighting at the quarry?

My first session in the pool, I was not with an instructor. I took it upon myself to go get in the pool when my other LDS had it reserved for an OW class of their own (which I paid them for, and signed their Release). They only had 1 student, so it was her, her instructor, and me in the pool. I did tell the instructor I got a new drysuit the day before and I was there to try it out. I read the Drysuit Diver course book and filled out the Knowledge Review the night before, just to make sure there wasn't any info I didn't already know from prior research (there wasn't). I got my trim and buoyancy sorted out after a few minutes and then practiced things like hovering inverted and then righting myself.

My second pool session was with my drysuit course instructor, from my LDS where I've been doing my training and bought my drysuit. She knew that I had already been in the pool with it. She asked how much weight I was using and I told her that I was using none beyond my SS back plate and that I had confirmed it to be plenty of weight, even with my tank at 400 psi. She just said, "oh! Okay. Good!" There was no further discussion about what my weighting needs might be at the quarry.

We got in and knocked out the required skills quickly, except for the full suit flood. She suggested doing anything else I wanted to work on first and doing that at the end. I did a swim through of a suspended hula hoop without touching it at all (except for a fin tip, when I thought I was completely through). Then we spent the rest of the time with me swimming around practicing my buoyancy while doing things like mask remove/replace, and her helping me work on my back kick (which she really helped with - I went from Useless to Occasionally Effective!). Eventually, I got bored and we went ahead with the full suit flood drill and then got out. She said it was obvious I'd been doing some diving and practicing since my OW course and my buoyancy and trim were great. By that point, I really had no thought to ask her about suggestions for weighting at the quarry.

 

[Storker]

I use 31 pounds of ballast (including the plate) with my undergarment alone, and I have to add at least 2 pounds if I put on the heating vest.

Since I'm one of those who regularly hear "you're using that much???" (I use about the same amount as you; 14.5kg), I'd love to hear what type of tank(s) you use with those 31#.

 

[Imla]

As I never dive singles anymore, these numbers may seem squewed.. But just to show the difference in different configurations:

Me and my D12s in pool (freshwater) with just thin merino sports undies... grossly overweight.

D12s, summertime, shallows, hot salt water (18C)... just a couple of layers of merino sports undies and one pair of wool socks. I use a 4,5kg (9lbs ish) tailweight. Mainly to keep trim comfy.

D12s in the fall. temps around 12-15C. Skip the merino sports undies and put on my BARE Fleece Undergarment and 1-2 pairs of wool socks(Btw, TSandM, you should try this baby. We are a lot of girls swearing to this one in Norway!) Perfectly weighted with the 4,5kg tail weight.

D12s in the winter... Temps around 0C double merino layers. Possibly an extra layer of wool next to skin, BARE undergarment, 2-3 pairs of wool socks. and even a vest. 4,5 tailweight + 2,5kg P-weight + 2kg on the harness.

Now.. this is in steel doubles. However... Even choice of gas counts. Nitrox vs Trimix. 3 very empty S80 stages will be positive.

What I mean to show with this is that something as miniscule as an extra pair of thick socks, or a thin top, can cause quite a shift in the need for lead. Also, although you _can_ stay down with a squeezed drysuit... the cooling effect is a lot more noticeable if you have less air in your suit. (You can try this in the shower.... put your suit on with just a thin layer of garment, squeeze the suit. Step in the cold shower. Take the time. Now... just inflate the suit a slight bit. Step in shower again. Feel the difference)

 

[TSandM]

I use that ballast with essentially all our steel tanks. My standard is an HP100, but the same weighting is required for HP130s, if you consider 500 psi to be where you determine your weight, and our little HP80s are the same. IIRC, my LP95s were a bit heavier, but I didn't bother to change the weight. I don't mind a "fluffy" suit, but I sure mind a squeezed one. Except in MX, in the caves, where I dive shrink-wrapped so that I don't end up with the problem of having to go downhill and then not being able to find a place to drop my feet to get the air out of them. But the water there is 75 degrees, so getting cold in a dry suit is not really an issue.