air consumption curiosity

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air consumption curiosity

Post by JJHACK » Tue Oct 10, 2017 10:45 am

Hi guys, At the local dive shop today there was an interesting topic that I would like to share and also get other opinions and feedback.

I have just recently completed my drysuit classes and Drysuit certification with SSI. I now await my drysuit which is ordered and being built for me. One of the things that was mentioned by another customer or two was that Drysuit dives are more efficient with air consumption. Several of the shop folks and customers were then chatting about this and seemed to all fully agree that all else equal in the puget sound temperatures, the drysuit diver will have more air remaining than a wetsuit diver.

I asked if it mattered if the drysuit was neoprene or a laminate design. I assumed that the neoprene would be more close to a wetsuit for buoyancy. No the answer was that drysuits are warmer so breathing rates are lower. The other one that seemed a strong opinion was that the drysuit is not even close to as restrictive around your chest making breathing easier and less effort.

It was the first I had heard this advantage of a drysuit over a wetsuit. The opinions varied on just how much more time or what the percentage was.
Most agreed it would be a safety stop difference or thereabout. I think many of these guys have been mostly drysuit divers for a long time, and may not have fresh experience on this.

My experience with this is not good because I have only ever been a wetsuit diver. I can say for sure I get more dive time in my less snug wetsuit than my quite snug wetsuit. It's not a massive difference, but certainly noticeable.

Anyone thoughts on air consumption Dry VS Wet?
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Re: air consumption curiosity

Post by Norris » Tue Oct 10, 2017 11:27 am

In my opinion it all boils down to your breathing. If you have smooth controlled breathing I would wager to say that your consumption would be identical. It ALMOST sounds like some discussion to try and solidify your NEED to have a dry suit.
Some would argue that a dry suit would be less efficient in terms of air consumption due to charging your suit with back gas during dives? Of course this is assuming you are not using argon.

I am curious to see others views on this, but for me I would disagree with the statement "A dry suit allows you to be more efficient with air consumption as opposed to a wet suit.
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Re: air consumption curiosity

Post by Jeremy » Tue Oct 10, 2017 11:51 am

I dove in a wetsuit in the sound for three years every weekend. Then I switched to a dry suit. Zero difference in my case.

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Re: air consumption curiosity

Post by GearHead » Tue Oct 10, 2017 2:36 pm

Interesting question... Since I've never dove wet in the sound, I can't make a direct comparison. However, being streamlined in the water greatly reduces effort, and thereby reduces air consumption. Both of my suits are compressed neoprene, and fit me very well. I think the air added to a suit only amounts to a few breaths worth per dive, so that wouldn't be much of a factor.
Those of us who take trips to dive in warm water usually notice reduced air consumption during the trip. I'm sure being warmer has something to do with that, as well as not needing to climb into the equivalent of a space suit to have adequate exposure protection.

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Re: air consumption curiosity

Post by jmartel » Tue Oct 10, 2017 7:51 pm

My wife's air consumption went down when she switched to a drysuit. I'll know about mine in about a month or so when my drysuit arrives.

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Re: air consumption curiosity

Post by CaptnJack » Tue Oct 10, 2017 8:47 pm

Its going down in a drysuit because there's less shivering. For my last comparison (many years ago), go try diving Salt Creek in a wetsuit, you will never go through a tank faster. Its damn cold out there!
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Re: air consumption curiosity

Post by ohopdiver » Tue Oct 10, 2017 9:46 pm

It matters for four reasons. 1. You use less air in a dry suit because you use less energy staying warm until you get a leak. 2. You will use more air staying warm by inflating your dry suit. 3. your going to use more air in a dry suit adjusting buoyancy. 4. Wet suits are usually more streamlined so you would use less energy/air moving through the water. It's not worth the effort to try to quantify. Just buy the dang suit and you will use less air with experience.

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Re: air consumption curiosity

Post by fmerkel » Wed Oct 11, 2017 8:00 am

I can't answer wetsuit > drysuit for sure, too many variables, but suffice to say if you are freezing in a wetsuit, and warm in a drysuit your air consumption will probably be way better in the drysuit. If you aren't comfortable, the dive can be miserable.

But, you can freeze in a drysuit too. I've seen lots of that and either the increased air consumption or simply being cold cuts the dive short. Depends on the suit, the undergarment, and suit air management. When I went from my first drysuit to my 2nd (both shells) I got the thickest undergarment OS sold at the time. I needed 6# more weight but my bottom time went up >10 minutes immediately. Obviously the undergarment at work.

Years later my wife and I got top end custom fit 5mm compressed neoprene drysuits. We expected to need more weight. What we found is we both dropped 6# of lead, AND our bottom time instantly went up 10-15 minutes on dives with those suits. Some of that was streamlining, most was just warmth. In general we find we do better than people with shell suits, and we dive with a LOT of people with shells. Neoprene seems to have gone out of vogue. We are both small and thin, so we don't have size advantage.

Add a top end THICK good fitting hood to that and you improve it even more. Hoods that come with suits are often mediocre at best and some are awful.
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Re: air consumption curiosity

Post by Grateful Diver » Wed Oct 11, 2017 10:03 am

Yes, using a drysuit will help you reduce your air consumption ... but not for the reasons you might think. Ultimately you'll end up diving more often, because you'll be more comfortable. And the more you dive, the lower your air consumption becomes due to improvements in technique that come with experience and relaxation.

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Re: air consumption curiosity

Post by Steiger » Sun Oct 15, 2017 8:44 pm

My air consumption went down due to comfort, but it's really easy to also associate that with me getting more comfortable with the buoyancy characteristics of the drysuit and being more relaxed. More relaxed breathing = longer dive time.

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Re: air consumption curiosity

Post by H20doctor » Mon Oct 16, 2017 1:24 am

i did a dive with my son 3 weeks ago at EUP in my 7 mil wet suit ... i got 73 mins .. on a Alum 90 ..average depth 35 feet.. It makes no difference for me to be either dry , Or wet .. What it comes down to is being relaxed underwater , and having the ability to be comfortable , and relaxed.. did i say Relaxed ??? the more you dive , the better your air consumption gets ... every new diver sucks a tank down ..
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Re: air consumption curiosity

Post by 60south » Mon Oct 16, 2017 6:52 am

Get a drysuit, you'll be more comfortable in NW waters.

If you find your gas consumption goes up and your dives aren't long enough -- I doubt this will happen -- simply use a bigger tank.

For most dives, I am thermally limited (I get cold) or diuresis limited (I need to pee) long before my gas runs low. :)

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