Drysuit weight vs. undergarments?

[elmer fudd]

I recently bought a drysuit, (Mobby's Armor Shell, trilam), and am currently trying to get my weighting figured out. Prior to this I had been diving wet with a 7mm O'Neill J-suit here in the Puget Sound. I'm 6'1". 220 lbs and with my HP 119, Zeagle Ranger and an aluminum 19 ft pony bottle, I was perfectly weighted with 19 lbs of lead.

I'm not entirely inexperienced with drysuits. I used to have a Harveys, but it was a poor fit and I sold it and went back to diving wet.

Yesterday I did a couple of dives. To begin with I added 7 pounds of lead to bring my total up to 26 lbs. During an ascent at about 30' I started to become positively buoyant. I grabbed a log and my buddy helped me work the bubble out. As we got shallower though and my tank became lighter it became apparent that I was underweighted. At the end of the dive, (in very shallow water), I had to fin to get under the water and could only stay neutrally buoyant at 10' and about 1200 psi with all the air purged from my suit and BC and with a noticeable squeeze.

For the next dive I stripped off some of the undergarments I was wearing as I had been feeling overly constricted and I added 6 lbs of lead. No issues this time. With the fleece and nylon jacket I had been wearing underneath gone, I could move much more freely and the additional 6 lbs. easily kept me down.

So what I'm wondering is how much effect my undergarments will have on my weighting and am I having to add an abnormally large amount of weight compared to what I wear wet? I'm thinking that I could probably lose 2 lbs from that last dive, but still means I'm wearing 11 pounds more than when I dive a wetsuit. I was wearing a lot of fleece during those two dives and I'm thinking that if I stripped half of it off I might be able to reduce my weighting a few more pounds. I definitely was using a lot more air on those two dives than I usually do.

 

[sschlesi]

Undergarments have a dramatic effect on required weighting. Diving in our area, it is common for people to use 30-35lbs of lead along with steel tanks. Some need a little more, some a little less. Personally I use 34 lbs with HP100s, with 32lbs I get buoyant at around 700 psi.

Last year I was diving with 32 lbs and then I added a fleece jacket to my undergarments. After a couple dives where I needed to grab rocks to complete the safety stop, I added the 2lbs and everything is good again.

 

[elmer fudd]

So it looks like I'm not too far out of whack with my weighting then. I think I overdid it with the undergarments anyway, so I can probably strip off some of what I was wearing and hopefully shed a couple more pounds of lead too.

 

[gcbryan]

I think you are in the right ballpark. I'm 6' 1" 185 and have a HP119. I use a BP/W where the BP weights 5 lbs and I use 22 lbs on a weightbelt so in comparison to you I'm using 27 lbs.

Your BC probably is a pound or two positively buoyant just due to padding so that might compare to 29 lbs and you say that you can probably drop 2 lbs so that would bring you to 30 lbs.

Undergarments do effect your weighting greatly but you do what you have to do to stay warm!

 

[AfterDark]

Poly wicking undergarments is what you want. You can get away with a lot less and lighter undergarments with the wicking stuff. I use it on land. I haven't used it diving yet but it should work the same, wicking moisture away from your skin to keep you dry and warm. I used to use a cotton sweat suit years ago with my dry suit. I used 40lbs of lead, 20 lbs on my belt and 20 lbs on a harness that I made. Dropping the belt was enough for a fast trip to the surface.

 

[it_mike]

Last dry dive, freshwater, DUI ActionWear 300, AL80...

18lbs of lead, plus Oxy backplate and slightly overweighted. You're doing fine.

 

[TSandM]

Undergarments have a HUGE effect on weight requirements! When I switched to the White's MK3 I'm using now, I had to add four pounds compared with what I had been using before (but I'm much warmer).

I use 31 lbs of total ballast with a single 95 or 130 in Puget Sound (5'4", 120) so you aren't far off at all.

 

[spectrum]

elmer fudd

As others have said the influence of your garments is huge. The key to warmth in a drysuit or in building a house is trapped air spaces. That is what is behind all of the drysuit garments. The second key is moisture control. A home is built with vapor barriers and venting. A diver evades perspired moisture with a good wicking garment. Remember that you are diving in a suit that is in cold water and your perspiration will condense in the suit. The trick is having it condense away from your skin.

Back to weight....... A good drysuit garment will do a lot of things. First it will trap air effectively. That is to say it will resist compression. This helps limit how much air you need to inject. In any case the loft of the garment represents displacement and that must be counteracted with lead (or a cylinder swap etc).

There are some other things going on here I think. A good garment is designed to permit air management in the suit. It may have venting grommets for instance. It is also designed with fabrics that resist blocking or clogging your vent valve. The shell is also intended to slide freely in the suit to ease movement. Thinsulate and similar fillers will retain a good part of their thermal properties when wet. This important on repetitive dives and in the event of a flood. In really cold water a flooded wetsuit with the wrong garments could be dangerously cold.

It sounds like you may have been diving with some random winter outerwear and that will be very difficult to manage as an effective cold water undergarment in a shell suit.

Pete

 

[elmer fudd]

It sounds like you may have been diving with some random winter outerwear and that will be very difficult to manage as an effective cold water undergarment in a shell suit.

Pete

That wouldn't be too far off the mark. I didn't have enough money left over after buying the suit to get any dedicated drysuit undergarments.

I wore a thin layer of cotton and two thicker layers of fleece. It did keep me warm and dry and once I ditched the outer layer on my upper body I could move freely, so I don't think it worked too badly, but there's still some room for improvement there.

I still don't have the change needed for an actual undergarment, so I'm thinking that for my next dive I'll probably ditch the cotton and get some underarmor and combine that with one layer of fleece.

 

[gcbryan]

Definitely ditch the cotton.