SAC rate went down the tubes

[Henryville]

I have started diving a dry suit (DUI CF200 with 200g thinsulate) recently. After a very busy season of wetsuit diving, I had my SAC rate down to the .4 - .5 range. In the drysuit, my SAC rate has skyrocketed. I know that some of the gas is going to the drysuit, but I am thinking I am at double or more my usual rate.

I think what is going on is that my chest is getting squeezed and this is stimulating me to breathe faster and more shallowly. I am using my BC for buoyancy and adding just enough gas to the drysuit to keep the squeeze from being really unfomfortable.

Is my experience with an elevated SAC rate a normal aspect of learning drysuit diving? Any advice/commentary appreciated.

 

[Mo2vation]

I have started diving a dry suit (DUI CF200 with 200g thinsulate) recently. After a very busy season of wetsuit diving, I had my SAC rate down to the .4 - .5 range. In the drysuit, my SAC rate has skyrocketed. I know that some of the gas is going to the drysuit, but I am thinking I am at double or more my usual rate.

I think what is going on is that my chest is getting squeezed and this is stimulating me to breathe faster and more shallowly. I am using my BC for buoyancy and adding just enough gas to the drysuit to keep the squeeze from being really unfomfortable.

Is my experience with an elevated SAC rate a normal aspect of learning drysuit diving? Any advice/commentary appreciated.

You didn't specify diving experience with the DS - but I know when I look at my wife's, her SAC went thru the roof for her first 10 or 20 dives - she was struggling. Floaty Feet, under weighted, etc, etc. After she got in the groove, it came down and eventually passed her wet SAC.

The puffs you put in the suit shouldn't impact your SAC to that extent (doubling it...) so the only thing I can think of is you may have increased your weighting significantly.

Did you go to Ankle weights? Surely makes it harder to kick - that you kick it up a bit (har har...)

K

 

[Henryville]

You didn't specify diving experience with the DS - but I know when I look at my wife's, her SAC went thru the roof for her first 10 or 20 dives - she was struggling. Floaty Feet, under weighted, etc, etc. After she got in the groove, it came down and eventually passed her wet SAC.

The puffs you put in the suit shouldn't impact your SAC to that extent (doubling it...) so the only thing I can think of is you may have increased your weighting significantly.

Did you go to Ankle weights? Surely makes it harder to kick - that you kick it up a bit (har har...)

K

Literally just starting to dive the drysuit.

You are right, I increased my weight significantly. No ankle weights, diving a 12 lb steel plate (I also use this diving 5mm wetsuit, a little overweighted, but okay) and 14 lbs on the weight belt (usually diving wet I don't wear any weight belt.)

I am still able to achieve and maintain a horizontal swimming posture, but definitely not getting the same distance for propulsion effort so working harder. This is in saltwater diving a single AL 80 or 12 liter LP steel. I am in good shape.

 

[Mo2vation]

Literally just starting to dive the drysuit.

You are right, I increased my weight significantly. No ankle weights, diving a 12 lb steel plate (I also use this diving 5mm wetsuit, a little overweighted, but okay) and 14 lbs on the weight belt (usually diving wet I don't wear any weight belt.)

I am still able to achieve and maintain a horizontal swimming posture, but definitely not getting the same distance for propulsion effort so working harder. This is in saltwater diving a single AL 80 or 12 liter LP steel. I am in good shape.

I actually dropped weight when I went to the BP and DS. It takes awhile to get the DS dialed in. Most people load up on the weight and its just a cycle. Little by little you'll take the weight off. Everyone does. I went into DIR/F with what I though was a very modest 16# and came out diving 10#. I've since moved to 8#. It just takes time.

Aside from the SAC soaring, are you loving the DS?

K

 

[Henryville]

I actually dropped weight when I went to the BP and DS. It takes awhile to get the DS dialed in. Most people load up on the weight and its just a cycle. Little by little you'll take the weight off. Everyone does. I went into DIR/F with what I though was a very modest 16# and came out diving 10#. I've since moved to 8#. It just takes time.

Aside from the SAC soaring, are you loving the DS?

K

I have to honestly say, not yet. Getting through DIR-F in the 5mm wetsuit and diving doubles with that all summer and into the fall, I was feeling pretty dialed in with my diving. Now I feel like a total rookie (which, of course I am as far as the DS is concerned.) Mobility feels impaired and I think I see why GUE recommends the TLS or other laminate suits vs crushed neoprene. I also think I cut my wrist seals back a bit too far and have gotten wet arms every dive.

On the other hand, I am loving the prospect of extending the diving "season" to a permanent event and like the ability to stay nice and warm in water that would surely have been uncomfortable or even dangerous in a wetsuit.

Everything in good time, I guess I just have to accept the need for a bunch of dives before I get my weighting to a realistic number, get the new zip seals that are tighter at the wrist, and generally get to a comfort level comparable to what I have wet at this point.

Thanks for your thoughts and advice.

 

[Uncle Pug]

You will get your SAC back under control... don't even consider it right now... just work on getting comfortable with the drysuit and it will happen quicker than you think.

As for the CF200... great suit... that isn't the problem... in fact I understand that Andrew G. was seen wearing one recently. I personally don't like how heavy they are out of the water but the fit can be much better since they have a little stretch.

 

[Mo2vation]

On the other hand, I am loving the prospect of extending the diving "season" to a permanent event and like the ability to stay nice and warm in water that would surely have been uncomfortable or even dangerous in a wetsuit.

I'm a SoCal weenie, and my wife and I were only diving from April / May thru November. Its been the best thing ever, extending the season. Out here, winter diving (as in SoCal winter... hee hee) just rules. No crowds, extended viz, different stuff to see. You'll never regret going dry.

On the wrist seal thing, are you carrying anything? Camera, Goodman handle, etc? My seals are as dry as a bone, until I'm carrying my cam or my light. The wrist tendons let in water then. Yesterday I attached a buddy's DS hose (he forgot... like I often do) both wrists got soaked. If you're pretty rocked up, it can also be tough to seal.

K

 

[DA Aquamaster]

Fit is critical in a dry suit, but even a good fitting drysuit will not be as form fitting and low drag as a wet suit, so you end up losing some of the glide off your kick. If you try to maintain the same cruising speed under water, the SAC rate will go up as more O2 is required to develop the extra thrust to over come the extra drag.

Proper weighting is important as too much air in the suit will lead to that out of control feeling. If you are diving doubles, hauling stage/deco bottles etc, using the BC for bouyancy control is also critical as you otherwise end up with too much air in the suit.

 

[Henryville]

I'm a SoCal weenie, and my wife and I were only diving from April / May thru November. Its been the best thing ever, extending the season. Out here, winter diving (as in SoCal winter... hee hee) just rules. No crowds, extended viz, different stuff to see. You'll never regret going dry.

On the wrist seal thing, are you carrying anything? Camera, Goodman handle, etc? My seals are as dry as a bone, until I'm carrying my cam or my light. The wrist tendons let in water then. Yesterday I attached a buddy's DS hose (he forgot... like I often do) both wrists got soaked. If you're pretty rocked up, it can also be tough to seal.

K

Probably something like that is contributing to it. I tried to pay attention to when I felt water coming in, it seemed to be at the end of the dive when I was getting gear squared away (Goodman,) helping a student with something (like getting out of the surf without getting smashed on the rocks,) or working on some other manual task. It was also happening at shallower depths although I didn't expect this to be an issue as I am diving with the dump valve fully open.

I ordered new zip seals today, and will go with a really tight cut (three rings or so less than current) to see if that helps. My biggest fear is that the suit is not fitting right, maybe arms too short although this seems unlikely. I'd really hate to take the loss on reselling this thing for another with a different fit.

I appreciate the advice on this issue, right now I'm just going to get some more dives in, try to get more comfortable, maybe try tighter seals, and see what happens.