Ditch that weight..

Hi there divers.

I have another question along the lines of weighting. How much weight (as a % of your total equipment) should we allow for ditching. My backplate and wings are due to arrive anytime soon so i will have to think about how i distribute my weight. My backplate and the BC keel weight weight 12 lbs (none ditch'able) so i will be taking that off my weightbelt. My tank is neutrally buoyant with 50 bar (without valve and regs) I ususally carry 10 to 12 kg's of weight but i will only be planning on having approximately 5 kg's in my weightbelt. Will this provide me with enough weight to ditch in an emergency? Im waiting in anticipation of your replies. Cheers

Frog,

better perhaps is to think of the buoyancy provided by your jacket/suit and the ammount negative you would be if you lost these two. - this then allows you to be certain that you are positive when you drop your weightbelt.

For me, to be neutral with a nearly empty 300bar 12L in my neoprene drysuit I require 28 or so Lbs. At the start of a dive I am probably 8 Lbs negative, which at depth (suit compression = loss of buoyancy) with a low on air tank (buoyancy change 4Lbs or so less negative) and with air in the suit to prevent suit squeeze (probably 6 - 8 Lbs of buoyancy) would have me bang on neutral.

Loss of the air in the drysuit at depth would leave me needing to jettison a minimum of 6-8 Lbs to become +ve-ly buoyant, and to float at the surface I probably need 8 Lbs of buoyancy to be neutral, add a couple to be positive. - QED I need 10Lbs of ditchable weight minimum. - Since you are going to ditch as a last resort - it is probably best if you allow a bit more than 2Lbs for you to be positive, perhaps add a bit more.

Don't go by any general rule for this type of thing, work out how things play for your setup, and then try it from 3m (12ft) or so (better - try it in a relatively deep swiming pool). How much you need to ditch also depends on how much air you have in your drysuit (as you are in the UK I assume you are diving dry). If you have a membrane suit you need to ditch far more weight, as your suit has no intrinsic buoyancy (at depth I can rely on a minimum of 10Lbs buoyancy from my drysuit if it floods, and I only loose a small percentage of my buoyancy from the air that is no longer there, whereas with a membrane suit, which will be using air, for all the buoyancy will have a greater buoyancy change if it floods)

If you are diving with a membrane dry, I suspect 5Kg's is not enough to ditch, it is far better to ditch too much, than not enough.

HTH

Jon T

If you're diving dry it doesn't matter. First, properly balance your rig and you'll be able to swim it up if needed. Second, your dry suit will get you up if needed. Third, it's a good idea to carry a lift bag and reel which can get you up. Fourth, you're buddy can get you up.
I would prefer to not even have a weight belt with a dry suit, but for the time being I have 10lbs on a belt with double LP 95's. I hope to get a v-weight someday and get rid of the belt all together. Just put the crotch strap over the weight belt just in case the belt accidently comes off (just happened to me last weekend). Crotch strap caught the belt, so I didn't lose the belt and screw up my buoyancy.

Mike

Here in Fla,diving with only a polartec or skin I need no keel weight or any ditchable weight.I am nuetral with an empty tank (al 80)I use a Halcyon 18# wing.When diving wet I use up to 12#.When using doubles & stages out come the bigger bladders.Fine tuning takes a few dives.Better heavy than light.

hmmmm...interesting question.

I've seen sources that say 60% or 40% should be ditchable. I think that the best bet is to set your rig up and practice on a shallow dive. Now I'm not condoning a rapid ascent here, you need some control in the environment. I know that if I'm diving dry and am neutral, I can ditch a couple of 2# weights and I'm on my way to the surface. that is a small fraction of my weight in the pouches (maybe 10%). Something to keep in mind.

Cheers!