[Simon Leach]

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Another daft question from your local neighbourhood novice.
When I qualified I used a membrane suit.  Didn't care for it too much and after trying different suits I got a NDiver - Divemaster crushed neoprene with a NDiver 'bulky' thermal undersuit.  First time I tried it I had to use extra weight to get below the surface.  Then went off to Tenerife and got more experience.  When I got back I went to Capernwray, it was a hot day so didn't use the thermal - just t-shirt and shorts.  Still warm as toast, and because I had dumped a couple of kilos of weight in Tenerife I dived with the dry-suit with the same weight as in Tenerife.  As I say, warm as toast, no hood or gloves either, and NO problems with weight - 2 really good dives. Two days ago a friend from work and I go up to Capernwray - again.  It's a bit chilly and wet and windy, so I use the thermal undersuit, only for the second time.  On the first dive I had real problems getting down below the surface with the same weight when without the thermal suit.  Once I reached 6 metres on the descent I was fine and to be honest only put air into the drysuit once - most comfortable dive I'd had and the best bouyancy - however, on reflection I now reckon I should have aborted and put more weight on when I realised I was not getting neg. bouyancy easily enough on the descent.  It dawned on me as we came up - everyhting was fine to about 7 metres and then between 7m - 5m the phrase 'polaris' sets in.  I had to force my head to face the bottom and fin to keep at 6 metres.  We had done a very gradual ascent simply because of the nature of the dive but I knew this wasn't right.  There was no panic on my part and I did the 6m stop, but inverted and having to fin a little.  I can hear to ooohs' and the aaarghs! as I type - but I'd rather own up and learn.  My Buddy - who is more expereinced - said I'm probably near to getting my weight just right as I didn't need to touch the inflator valve on the suit apart from one short burst once below 6 metres.  I put on 4Lbs extra on the second dive and literally fell like a stone, having to mess around with bouyancy control the whole dive - Why does the thermal make so much difference? - this does seem to be the common denominator - should I just dive with much more weight than I need or persevere until I get it just right.  Then, of course there's salt water to contend with.  Go easy on me - pleeeeeease!!!!   No doubt there will be NO TAKERS for the offer to dive this Thursday 12th?

 

 

[andy2tanx]

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thermals make alot of difference because they trap more air than shorts and shirt. when i put themarls on i add 4kg which seems to work.

 

[Davey Willo]

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No Oooh's and Aaarghs from me my friend, it sounds like you coped admirably with a situation that you were presented with, yes it appears that you may have been underweighted if you had a struggle to get down at first, but also be aware that its very easy to have air trapped in either your drysuit, your BC or both, what appears to be next to nothing at depth can very quickly expand and off you go..

I would agree though, that you do appear to a bit light if you were struggling to get down in the first place, does your drysuit have a manual cuff dump or an upper arm mounted auto dump? If it has an auto dump, then make sure that it is open at all times until you become well practised with it, in fact I run mine open all of the time anyway.

Without knowing the size of your tank it would be impossible for me to calculate how much positive bouyancy you gain as the tank becomes empty, but it wont be a lot so don't don't go berserk adding weight. The correct way to calculate your weight would be to get into the water dressed as you normally would (so I would suggest full thermal protection i.e. undersuit etc) have your tank at about 50bar and then adjust your weight so that fully exhaling you would sink and full inhalation you would hold position at about eye level, then add a couple of pounds because your still learning, you 'should' be somewhere near at this point, after that Simon its just get in the water and test as often as possible adjusting as you go.

For salt water (if you were to do the above test in freshwater) would be to add 3% of your overall weight, so if for example you and your kit weight 200lbs then you would add 6lbs for saltwater.

Best regards
Dave.

 

[Simon Leach]

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Andy - thanks mate.
Dave - manual cuff dump and I used a 12L dumpy.  Will try the exercise you've suggested asap.

 

[parahandy]

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Reading Simons experience and transition from membrane to neoprene suit, having just had the reverse experience understand where he's coming from.

Until recently spent the last 20years diving in a neoprene drysuit. On the face of it agree it looks like Simon is/was underweighted.  

A few personal observations when using my neoprene I've always tried to be weighted to allow for a safety stop without having to "fight" to stay down. I've found in practice swimming around in anything less than 5m in a neoprene suit a real bind.

The obvious solution to this is bang on a bit more weight,I've found that this solves the problem but is offset by the disadvantage of leaving me slightly overweighted a depth. I like to carry as least weight as possible, so in my case its a compromise,I prefer being slightly bouyant in shallow water.

Andy pointed out the problem with a thicker undersuit ie more air trapped. With a neoprene suit giving a bit more thermal protection you should be able to get away with a slightly thinner undersuit. Weezle do an undersuit think it the "compact" model ideally suited for the neoprene suits.

Pointed out earlier, especially with a new suit, we can all over look getting all the air our. Make sure the manual dump is up in the highest point before the descent, ie if need be lift your arm up. If it looks like you cuff dump isn't working, hold you cuff above the water and pull the seal back to vent the air.

Make sure the undersuit material is not blocking the cuff dump sometimes a problem with the thicker undersuits,hence the suits with the netting cuffs.

You'll get there in the end

 

 

[Davey Willo]

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Simon...

Parahandy has been diving since Noah was cutting trees for a very large boat, so he knows what he's on about...
Although having a huuugge belly has messed with his bouyancy control just lately  

 

[Billy the Kangaroo]

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Hi Simon,

Sorry if this sounds too obvious - your undersuit traps more air to keep you warmer.  If it's trapped more air - you need more weight to counter it.  
However, you may wish to "squish" any excess out before you get in the water.  One way to do this when you kit up is to put on your suit and before weights, BCD etc. squat as tight as possible and bring your arms in close.  Let all the excess air fart out around your neck - pulling the seal away from your throat may help.

When you do your buddy checks later,put as little air as possible back into the suit.
Similarly, when you are doing a walk-in or when you are on the surface, let as much excess air as possible out of your suit dump.

The above should reduce the amount of lead you need to carry.

( When you are under water, use your SUIT only as bouyancy control, dump all the air out of your BCD and only put any back in when you are back on the surface. )

I would suggest you try again somewhere like Capernwray, where you can use platforms and/or shot lines and/or buddy to fine-tune your weighting especially on ascent - when you may well be 5 pounds or so lighter with an empty cylinder.  If you get to the stage where you have to fin to stay down, then there is no way you will be able to vent from your suit as your dump will be lower than the air in there.
At Capernwray, you are also less likely to be deep enough do any real harm to yourself if you do do a UFFA - uncontrolled feet first accent.
If you want a buddy to practice with, pls gizza buzz.

 

[Davey Willo]

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Hmmmm, Sorry to disagree with you Billy but I think it might not be the best advice telling a fairly new diver to ONLY use his suit for bouyancy, especially while he is still trying to attain a correct amount of weight.

If he were to use only his suit for bouyancy control and happens to be carrying too much weight then there is a very great danger that the body of air needed to gain neutral bouyancy could be such that it ends up migrating all over the place, especially to the feet creating the very thing we least want... A Feet First Ascent or at least a feet high trim where his inexperience might not allow him to rotate in the water and release the air.

Although I personally 'do' tend to use my drysuit for bouyancy on shallower dives, (as no doubt you do too from your comments) I do this because it not only feels comfortable for me to do this and I also feel it helps me maintian a more horizontal trim in the water, but mainly because my weighting is such, that once I've taken the squeeze off I'm nearly neutral anyway.

But for a novice, and a novice still struggling with his weights it may be safer to keep his control in his BC for a while and only put enough air in the suit to remove the squeeze, thereby reducing not only the risk of FFA's but of fins being forced 'off' the feet through too much air moving into the boots (I saw this happen just very recently) theres also the fact that a drysuit dumps air much more slowly than a BC and can only dump from one location and Simon would have to raise his arm above his head to do that as he's using a cuff dump and therefore doesn't even have an Autodump working in his favour. At least with a BC he can dump air from it quickly and in any orientation.

Best regards
Dave.

 

[parahandy]

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Contrary to Dave's rumour I didn't learn the giant stride entry off the bows of the Ark.
I take on board Dave's suggestions of using the BCD for bouyancy control rather than just using the dry suit.
Certainly at a Novice stage using both I feel will only complicate matters. As experienced divers we tend to overlook the fact that "driving" a dry suit does take some getting used to. What becomes second nature on a dive, putting air in and dumping air out initially with something youre not used to requires some care.

The argument of whether to use the BCD or the suit for bouyancy or a combination of both seems to boil down to personal choice. Admittedly people do seem to get themselves in one #### of a state with a new suit till they get it sussed out. Run away ascents can happen all to easily if you don't apply yourself to regularly venting are on a ascent. Agree wholeheartedly better to get familiar with it in the confined shallow open water with a dry suit experienced buddy.

Like most of us I've experimented with bouyancy control techniques,  As Daves mentioned putting sufficient air in the suit taking the squeeze off, then using the BCD for bouyancy control works fine for me and many people.

Some prefer to use only the Dry suit for bouyancy.
I can well remember early drysuited divers with the first neoprene drysuits to arrive in the UK in the 1980's who had the misguided attitude not to wear any bouyancy devices, now that's scary.:nonono:

 

[PaulC]

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I read that Dave :rofl: ...the whole buoyancy thing is more complicated than one might think. Very minor changes to your rig can wreak havoc with your trim...I think on reflection the main thing is to be careful when wearing new kit, and use trial and error to get weighting right. Dave is quite right (and polite not to mention names) to say I found myself feet up on a recent dive - when I had been fine for the 15 or so dives previously. Mysterious, certainly, although there were a few minor differences to my rig that time out. On the next dive I dropped a K on Dave's advice and had a much better dive next time. Conclusions? My main conclusion is that we are all learning from every dive. Never feel downheartened if you have a problem on a dive - instead try to work out what went wrong and see if you can sort it for the next time! It's be boring if it was too easy, no?

 

[Dr Stevil]

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All personal opinion only but here's my "my 2 cents worth":
I've always taught new divers to use their suit only for buoyancy because a) they are goining to want to dive that way eventually so might as well start now, b) air in the suit keeps you warm and buoyant whereas air in the BCD only does the latter, c) trainees tend to get colder more quickly in my experience therefore the air is better in suit, d)sharing the buoyancy control between between suit and BCD adds to task loading which for a trainee is undesirable.
Re dumping air from suit, I find that "pumping" your arm helps to dislodge trapped air (amuses the other divers too as you look like you're celebrating coming back from a dive!)
I was taught (on my Adv Nitrox course) to wear exactly the same clothes for a given situation and log the weight required for each variation of kit/clothing.
In my instucting experience its better for trainees to be a little overweighted as nothing ruins a training dive more than not being able to sink and we all know what the dangers of a rapid ascent such as described above.
PS, having said all this if anyone sees me at "Divesite X" this weekend I'm probably not going to be the most "buoyantly controlled" diver as I've turned into a fat b****** over the summer and don't know how much weight I need because of that plus i've got a new kit config (twins), I'll be the one with a twinset pootling around in the shallows like a novice! :babycrawl:

(Edited by Steve W at 1:39 pm on Sep. 17, 2002)