Weighting with a Drysuit

[RMur]

I had my first experience with a drysuit at the recent DUI Dog days in Mermet last weekend and have some questions for you drysuit regulars.

I dove with an experienced drysuit diver (Doug, if you are out there - thanks for the help) who I met for the first time at the event and he was kind enough to babysit me. As we were gearing up he suggested that I would need a substantial increase in weight over my wetsuit diving. I dive with steel tanks and generally dive with 4-6 lbs with my 7mm wetsuit in freshwater (this seems to be on the low side for most people, but my cement-like brain may play a part). I took his advice and dove the drysuit with everything I had (18 lbs).

I expected to have some problems with buoyancy and wanted to avoid the embarassing (and dangerous) uncontrolled ascent so I was very judicious about making large changes in the volume of air in the suit.

But - the suit did seem to be pretty well squeezed against my body almost constantly. How much squeeze is normal? Maybe I was just being stingy with the air in the suit?

Was I still underweighted and therefore could not put enough air in the suit AND maintain buoyuancy? I tried to keep my BC bladder empty except on the surface (although I must admit there were some times when I resorted to a few puffs in the BC to keep me off the bottom so as not cause a silt-out).

I understand that compressing the undergarment in a squeezed suit is going to provide little insulation, but I don't have a good feel for what the balance should be? BTW, I was very confortable with respect to temperature. We dove to the 100' platform, temp probably 48-52F.

Also regarding the purge valve on the arm (is that what it is called?), I experimented with where to set the valve and got nowhere I felt confident about. I ended up closing the valve completely and opening it all the way to purge then closing it back down.

What do you think - does drysuit diving generally require substantial amounts of additional weight compared to a similar wetsuit dive? (ie. same diver, rig, water temp, etc.)

[skdvr]

The extra weight required is directly related to the undergarments that you use. I use different amounts of weight if I go from my warm water undergarment to the cold water one. That difference can be quite big. The only way to tell is to do a weight check. Some people do not like to bother with these because they tank time, but to me it is worth it to get it figured out and then maybe play with adding a pound or taking off a pound, rather than taking a guess and realizing that you are overweighted and then having to take weight out each time until you get close. Or the worse problem of being underweighted and taking a ride to the surface when you tank starts to get lite. If I get a new undergarment I like to get into so shallow water with just the undergarment and DS on (No Rig) and see how much weight it takes to sink me. Then add or subtract accordingly depending on what rig I am going to dive with. Then I will double check at the end of the dive by purging my tank almost empty, if it is not already there from the dive just so I can make sure I can hold a stop at 15 ft without a bunch of air in my BC or DS to keep me there.

As far as squeeze goes, that is a personal prefernece. I like just enough air in my suit to keep me comfortable. I do not want a big bubble floating around in there. It is OK to use you BC, that is what it is there for (Buoyancy Control). Just add enough air to your DS to keep the squeeze off and keep you warm. Some people like to use only their DS for buoyancy which is fine if you want to do that, like I said I just do not like that much air in my suit.

Welcome to the dark side of diving dry....

later
Phil

[RoyN]

I also use part BC and drysuit because I dive in double tanks that way my body isn't the marshmello man.

[beperkins]

Definitely start off diving dry by using bc for bouyancy and suit to reduce squeeze. I know the Padi speciality tells you to use the suit for buoyancy but if yu ever go tech you have to unlearn that which is harder than just learning it the tech way in the first place.

[snagel]

As Skdvr stated, the undergarmet is really the issue. I was at Mermet also and my goal was to try on their undergarmets. I have the Pinnacle Evo 2 and like it very much, so I tried the various undergarmets with my suit.

I tend to like to be a little over weighted regardless, but I noticed a huge range in weight needed/not needed depending on the undergarmet I tried. In fact, I did have a rapid ascent on one dive and had to grab the side of the wall to keep me down. I was wearing the DUI 400 undergarmet and didn't add a few pounds of weight. I knew I was a little underweighted to begin with, but went ahead anyway to avoid getting in and out due to all the congestion at the docks, thinking I would pick up a couple rocks if needed later in the dive (new divers close your ears because that is not what you are suppose to do). I was fine during the dive until my tank got lighter and then all of a sudden I headed North, purging and almost pulled a seal, but grabbed the side of the wall to stay down and level out a minute before inching my way up.

I've played with using the suit or the Bc for bouyancy control. Either way works, but I like to "just take the squeeze off" and use the BC. The problem with this method is 1) you are trying to control two bubbles; and 2) it works fine if you level off, but if your dive profile is going deeper and shallower it get's a little tricky.

I find most drysuit divers do need a little extra weight compared to wetsuit diving simply because they are adding more variables - air in the suit and thicker undergarmets. Some will argue, but then they are the ones also substituting weight for steel tanks and heavy backplates. It doesn't matter, as Skdvr outlined, figure out the proper weight needed for the various configurations you will have with equipment and undergarmets. If you do a proper weight check, you will be fine.

Purge Valve - I tend to keep this all the way open and control the bubble by leaning when I want to purge. This also allows for automatic purging as you ascend and the air expands. I just don't feel comfortable enough yet, to close it and want it open to avoid a rapid ascent. I definately would not recommend closing is completely - you are asking for a rapid ascent.

Most will tell you that entering into the drysuit world is like learning to dive all over again. I find this to be true because you are learning to control bouyancy with air in the suit. I've spent the summer diving dry just to gain confidence so that I can dive this winter dry.

S. Nagel

[in_cavediver]

I dive my suits such that I have just enough air to remove the squeeze and be comfortable and use the BC for everything else. I also dive double tanks almost exclusively so I don't normally carry more than a 6lb plate or 6lbs on my SM harness.

As for how much you need - its really just the question of how much you need to be comfortable how you dive. Experience is the only good way to get this nailed down. It also can change from suit to suit. My current Dive Rite takes less than my old whites suit.

[CompuDude]

The answer I was taught (and agree with, after experimenting a bit) is you should dive with just enough air in the drysuit to (a) take the squeeze off, and (b) allow the undergarments to loft enough to do their job. Some undergarments need a little more breathing room than others to properly insulate... polartech can work pretty squeezed, but Weezle needs a bit more room to loft. And between various undergarments, weighting needs can vary a LOT.

Personally, with my drysuit and a layer (or two) of polartech undergarments, I only need a couple more pounds with my drysuit than with my 7mm wetsuit. As a result, I tend to just dive my wetsuit a little heavy, then I don't need to change a thing, even switching wet to dry, for the vast majority of my diving.

[RMur]

Thanks for the responses. I think given what I have read that I was likely overweighted.