How much more lead?

[SCUBA Chick]

Hi!

I feel a bit of a numpty posting this but as I am new to this UK diving lark I hope that you will bear with me!

Right I have got myself sorted with my cold water diving gear and before I did this I had already completed my drysuit course. When I did my course I was wearing a Northern Diver Vortex suit and one of their undersuits and gloves (can't remember the thickness I'm afraid!) with a 12l steel. I used 8kg of lead and had no problems descending.

So, I got myself an Otter Brittanic Membrane drysuit (with the telescopic middle) and a 200 undersuit with gloves and hood. But, when I went to try out the new kit, again with 8kg of lead and a 12l steel I was too floaty to descend. Luckily I had taken my fourth element long sleeved top which I swopped for the undersuit (as the water temp was a tropical 19 degrees) and then was able to sink without a problem.

The dives were done at Caperwray so we are talking freshwater rather than saltwater....

What concerns me now is how much extra lead to buy for both the ability to descend in fresh water but also for the sea water diving which we will be moving onto shortly once I have sorted my weight requirements out...

For the record I am around 10 stone in weight and am 5 feet inches tall....

Any advice would be greatly appreciated as drysuit diving is all new to me!!!!

Cheers

Scubachick

[Brian of Aquanauts]

Your 200 undersuit will make alot of difference... but it shouldn't be that much.

I'd guess that the reason you couldn't sink could be partly to do with your breathing. Your lungs probably hold about 5l of air, breath it out and you'll become 5 kg heavier... don't breath in again for a while and you'll go straight down - if not add a bit more lead till you do.

Breathing wrong is the biggest mistake i come across - that and putting your fins on the wrong foot

[richarddbarker]

I've also got the 200gram otter undersuit, they are very warm. Unfortuantely they do seem to add quite a bit to your bouyancy due to their thickness. I've found I use 9kg in fresh and 12kg in salt, with a similar config to what you've mentioned.

Quite a few members of my club use the RoHo thermocline thingy and they are much thinner = less bouyant = less lead. But they aren't cheap and a few still swap to a thicker suit for the winter season.

Chances are if your too floaty with a full tank at the start of the dive then your going to be looking at another couple of kg at least. This should then give you enough weight for the end of the dive, ensuring a controlled ascent. Guess you'll have to do some bouyancy checks with different amounts of air in your tanks and see how you get on.

You will probably find you can shed some weight as you get used to your new equipment, I know I did.

Hope this is useful.

[SCUBA Chick]

Originally Posted by Brian of Aquanauts

I'd guess that the reason you couldn't sink could be partly to do with your breathing. Your lungs probably hold about 5l of air, breath it out and you'll become 5 kg heavier... don't breath in again for a while and you'll go straight down - if not add a bit more lead till you do.

I breathed out until I had no air left and it still didn't work as I realise that air left in the lungs can be a problem during the initial descent.....

Guess I'll just have to get some more lead!!!!!

Scubachick

[KISSer]

I'd really advise that you don't just bolt on lead until you can sink - you'll probably end up overweighted, which just brings a host more problems.

When you first try to sink you've quite possibly still got loads of gas trapped in the suit, and that along with breathing (already covered I knw), unconscious leg movements etc. can make it harder for you to sink. It's probably best to do a shallow dive - only 4m or so, making sure that at the end you've only got about 50bar left in the cylinder. You should then be neutral with no gas in your BC/wing and only enough gas in your suit to take the squeeze off. Get your buddy to add/remove lead until you hit that point, though if you're already down there the chances are they will be removing some. Obviously you both need some sort of temporary way of carrying weight to do this!

Then you know that with a full cylinder at the start of a dive you will be a couple of K heavier and so will sink. Patience, relaxation and thinking heavy thoughts also help!

[richarddbarker]

I agree, best thing is obviously to fine tune the correct weight but it's not always easy when you've got new kit, depends on diving experience, etc.

Scubachick, if you dive at Capernwray as you've mentioned previously you could use one of the shallowish platforms (think 6m would be good). You can take/drop some extra weight down to the platform. It'll be easy to find on there and you can make adjustments and then do some fin pivots, platform circling to see how it feels. If you end up too light you can grab the platform/rope, etc and get the weight back. Worst case your only at 6m so not a major issue.

Just a thought.

[SCUBA Chick]

Originally Posted by richarddbarker

Quite a few members of my club use the RoHo thermocline thingy and they are much thinner = less bouyant = less lead. But they aren't cheap and a few still swap to a thicker suit for the winter season.

Chances are if your too floaty with a full tank at the start of the dive then your going to be looking at another couple of kg at least. This should then give you enough weight for the end of the dive, ensuring a controlled ascent. Guess you'll have to do some bouyancy checks with different amounts of air in your tanks and see how you get on.

You will probably find you can shed some weight as you get used to your new equipment, I know I did.

Hiya!

I got my fourth element top for a snip at 30 quid off ebay.....definately worth the investment!

Looks like I'll have to get another couple of kg's then...

I certainly hope that I'll be able to shed some weight after a while otherwise I'll end up having to carry enough weight to 'sink a battleship'.....Boom, Boom....

Thanks for you help....

Cheers

Scubachick

[SCUBA Chick]

Originally Posted by richarddbarker

Scubachick, if you dive at Capernwray as you've mentioned previously you could use one of the shallowish platforms (think 6m would be good). You can take/drop some extra weight down to the platform. It'll be easy to find on there and you can make adjustments and then do some fin pivots, platform circling to see how it feels. If you end up too light you can grab the platform/rope, etc and get the weight back. Worst case your only at 6m so not a major issue.

Just a thought.

Great idea Richard....

I'll give it a bash over the weekend when we are there....

Thanks

Scubachick

[Jen S]

Hi,

It seems your not far off with the 8kg. You said you got down OK when not using the 200g undersuit, so it must be this that is making the difference. It shouldn't be making that much of a difference, so I'd just try another kilo for now. If you go to Capernwray, I'm sure they'd let you borrow some weights for the day, so you can try out what works best, then buy lead when you've found out what works.
As the others have said, you will need to do you weight check when your cylinders are at around 50bar, to make sure you have enough lead to stay down at the end of the dive.
Different suits will "trap" air within them in different ways too. It could be that there is more air "trapped" in the Britannic than there was in the Vortex, making you that bit more buoyant. Before getting in, try pulling your neck seal away from your neck slightly, then squatting down on your knees. This will squeeze out a lot of the air from the suit. Once you've got off the surface you can then start adding the air to reduce the squeeze.

With regard to the sea, most people add about 1-2kgs. Again, you'll have to try it out to see what works best.

Don't worry about this, as everyone has trouble getting their weight right when starting or getting new kit. Most people I know (including myself) did tend to start out overweighted, without realising, as this is just what they thought they needed. Over time, you may find you can reduce the amount of lead you need.

Jen

[grigor]

I too have a relatively new Otter Brittanic and 200 undersuit, dive with a steel 12l and am fairly new to drysuits - I too piled on a bit of lead first time out. The good news is that I've been shedding it ever since.

I found that the positioning of the shoulder dump meant I had an air volume across my shoulders that I struggled to vent. As my trim and general position improved I found the problem cured itself - the dump wasn't in the wrong place, I was. Looking back, I realise that the thick undersuit and my poor trim meant I didn't free trapped air until well into the dive.

At the time I received some good advice: don't worry about adding a little extra lead to begin with, focus instead on removing some as you settle down and learn the suit. I now check my buoyancy at the end of easy dives after my safety stop - thankfully my buddy doesn't mind being passed bits of lead. I'm learning to hate lead (just ask my back) and take every opportunity to shed some.

A handy extra is that the difference between your fresh and salt weightings should be around 3% of your total weight. In rough terms: stand on the bathroom scales with all your gear and your correct lead for fresh water, multiply the number you get by 0.03 and that is the amount you should add for salt water. At say 100kg, 64kg (10 stone) + 14kg (ish) tank + 10kg (fresh water lead) + 12kg (other bits), would mean you need 3kg extra for salt water.

If you want to account for air in your tank when checking buoyancy: multiply the tank volume (litres) by the remaining pressure (bar) by 0.00125. So a 12l tank with a 200bar fill would have 3kg for which you need account.

Hope you manage to get things sorted - I'm very pleased with my Otter suit and the 200 keeps me well toasty.

Cheers - Grigor