Cause of high consumption rate

Went for a dive trip recently and noticed that I'm sucking air faster than most everyone else on board the boat. I go down later, and have to surface earlier.

Granted I try to get back in the boat with 30-50 bar in my tank while the others only started surfacing at 50 bar.

It's diving in 30 degree C waters, so other divers were wearing either 3mm wetsuits, or just rash guards with shorts. Typically divers like this carry anything from 0 to 4 pounds of weights, some 6 pounds.

I was in a drysuit and carrying 12 pounds.

In the past my consumption was considered good. Have not calculated my SAC but my consumption was equivalent to small sized ladies in the dive group when i was wearing a wetsuit with 4lbs.

Am wondering if my increased consumption was due to the drysuit and extra weights? Or my shorter/fatter UTD fins?

Why were you using a drysuit and carrying 12 pounds when everyone else was in 3mm or rashies?????

No expert but id look at that first.....

WhiteSands:

30 degree C waters, so other divers were wearing either 3mm wetsuits, or just rash guards with shorts....I was in a drysuit

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Whitesands,

I'd guess that the drysuit is a contributory factor.

First of all there will be some drag from the drysuit.

Secondly, if memory serves me right you have a E-Motion ?
Have you done a weight check in warm water?

Thirdly, you are probably less relaxed in your drysuit than you think a) because the suit is new b) because you are getting used to it and c) because using the suit is different to how you would normally dive in warm water.

Practice, relax and enjoy your dives - it'll come down when you feel more relaxed and are not thinking about your SAC rate.

Wingy:

Why were you using a drysuit and carrying 12 pounds when everyone else was in 3mm or rashies?????

No expert but id look at that first.....

Click to expand...

For practice. Have a trip in 2015 and I want to log as many dives in a drysuit as I can before then.

---------- Post added December 21st, 2013 at 06:42 PM ----------

dbulmer:

Whitesands,

I'd guess that the drysuit is a contributory factor.

First of all there will be some drag from the drysuit.

Secondly, if memory serves me right you have a E-Motion ?
Have you done a weight check in warm water?

Thirdly, you are probably less relaxed in your drysuit than you think a) because the suit is new b) because you are getting used to it and c) because using the suit is different to how you would normally dive in warm water.

Practice, relax and enjoy your dives - it'll come down when you feel more relaxed and are not thinking about your SAC rate.

Click to expand...

Yes 12lbs is just right for me. 2lbs more would probably make it more comfortable during safety stops. With 12lbs I really have to make sure the wing is empty and the drysuit has very little air.

I've done about 20 dives in the suit now and am starting to "not think about it". But perhaps you're right about more practice.

I am suspecting my breathing rate is up because I need to move 8 extra pounds with each kick.

Simple experiment. Leave drysuit at home. Jump in in bathers. See how it goes.

Wingy:

Why were you using a drysuit and carrying 12 pounds when everyone else was in 3mm or rashies?????

No expert but id look at that first.....

Click to expand...

Yeah…that had me scratching my head too.

even with a dry suit once you are comfortable in it you should not have that much of a higher consumption rate than without.

There are many possibilities why people can breath faster than others and I think a good area to start on is buoyancy. Think of your tank as having an amount of air in it, the faster you breath the faster it runs out. Now imagine being in a park, if you were to sprint around the park imagine what your breathing would be like after the sprint versus if you casually walk around the park, obviously you are going to breath a lot more if you are sprinting as opposed to casually walking. One point where buoyancy comes in is ensuring your BCD/drysuit has enough air in it so you are neutrally buoyant at each stage of your dive. If you have not put enough air in your BCD/drysuit then without noticing you will be constantly fining upwards in order to stay ff the floor or to maintain your depth, all the energy you are using to fin upwards is wasted and that energy costs air. Try spending time ensuring your buoyancy is set by periodically stopping moving, stop kicking and put your hands in, what happens? if you go up then you need to let some air out, if you go down then you need to put some air in. once you are hanging in the water gently rising and falling with your breathing then you are set. Your buoyancy will need adjusting as your depth changes, as you go deeper you will need to put air in and as you go shallower you will need to let air out. Even if you spend the whole dive at the same depth towards the end you will need to release air as your tank weight starts reducing (if using aluminium). the goal here is to be nice and horiontal so that when you do kick it moves you forward gently. If your body is in a diagonal position then you will be wasting energy.

Another issue with wasting air with buoyancy is over inflating and therefore dumping air. I often see people putting in or letting out too much air which then results in them having to over compensate the ther way. This causes them to fight their gear and the laws of physics which means they breath faster and lose air through constantly dumping. Depending on the dive I use the inlate/deflate buttons very few times and inflate and deflate with short bursts.

Think about depth too. The deeper you go the more air you will consume. If you are diving on a wall and you are the one in the group that is the deepest then it stands to reason that you will consume air faster, if the dive site allows it (like a wall) then why not situate yourself in a shallower position than the rest of the group?

You could also think about your fin kicks, are they economical? Nice positive kicks from the hip without much bending of the knee is good, doing something that resembles peddling an invisible bike or climbing an invisible ladder underwater is again a waste of energy.

Dive slowly, nice and slowly, you'll see more, less likely to get split up, easier to navigate and you'll use less air.

WhiteSands:

Went for a dive trip recently and noticed that I'm sucking air faster than most everyone else on board the boat. I go down later, and have to surface earlier.

Granted I try to get back in the boat with 30-50 bar in my tank while the others only started surfacing at 50 bar.

It's diving in 30 degree C waters, so other divers were wearing either 3mm wetsuits, or just rash guards with shorts. Typically divers like this carry anything from 0 to 4 pounds of weights, some 6 pounds.

I was in a drysuit and carrying 12 pounds.

In the past my consumption was considered good. Have not calculated my SAC but my consumption was equivalent to small sized ladies in the dive group when i was wearing a wetsuit with 4lbs.

Am wondering if my increased consumption was due to the drysuit and extra weights? Or my shorter/fatter UTD fins?

Click to expand...

Well, we recently finished a thread about how I think that Drysuits are such high drag that they are bad for recreational divers in tropical waters....bad for things like air consumption due to having to push so much more drag than a wetsuit( which is MUCH Slicker)..and bad for skills issues( which does not seem to be your problem at all).

Beyond the drag issue....fin choice with Drysuit can compromise efficiency, as this might have you in jets or Hollis fins, neither of which is efficient at flutter --which you will need to use to keep up with wet suit divers ( most will flutter kick, and this is a faster kick than frog kick)--so this would make you waste more air, trying to push jet fins to the point that they get extremely inefficient for you...

And...one other thing to check...make sure you are breathing from your diaphragm, not from high in your chest....If you breathe from low in your diaphragm, you will ventilate far more effectively, so you "need" much less air volume pulled through your lungs--you don't need to breathe as frequently..if you breathe high in your chest/shallow breathing, this is more like the exaggeration on a diver that hyperventilates...but from high up in your chest, the ventilation is poor at getting the needed Oxygen exchange, so even with lots of breathing, you still feel like you are not getting enough air--and it would be hard to slow your breathing. This take lots of practice on land--learning to breathe from your diaphragm all the time.

danvolker:

I think that Drysuits are such high drag that they are bad for recreational divers in tropical waters....bad for things like air consumption due to having to push so much more drag than a wetsuit( which is MUCH Slicker)..and bad for skills issues

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Which specific skills would you say drysuits are bad for?