How much weight can I drop going 7mm to 5mm

Well I am going fron a Parkway 7mm one pc. to a Henderson 5mm Instadry. Right now my current setup is Parkway 7mm one pc. Halcyon SS backplate (6lbs) 36 lb wing, Steel 100 HP Tank, and 10 lbs weight on the weightbelt and I have my Buoyancy on the money now(still slightly neg). I was told I might be able to drop the belt altogether once I switch to the Instadry. I have also hear that the 5mil Instadry is a warm as 7mil reg suite, is this true?? Thansk Ed
PS I add 4lbs to this for salt

Order of magnitude, a full 7 to a full 5, is likely about 4 pounds, keeping everything else the same. That's the transition I see going from full 5 to full 3 -- a 2mm wetsuit delta.

A quick pool check is always good -- jump in, make sure you're fully wet, no air pockets, BCD empty. Weight until you're just neutral, sink when you fully exhale. Check your SPG and add 1 lb for every 400 PSI showing on the HP100.

(A 100 is truly 100 ft3 at nominal pressure, which is just under 8 lb of air at 3442 psi. Think of it as 3200 psi, and you have 3200/8 = 400 psi per pound of air.)

The salt change, normally, would be a bit higher, again if everything else stays equal for a given person, unless you're really on the small side or perhaps a couple of lbs of spare weight when in fresh water (you did mention that, and a few lb is no big deal -- I prefer slight overweighting, makes it easier to help others sometimes). It's about 1 pound in 40 of the total dry weight of the diver and all gear.
-Step on the scale with wet suit and BCD on
-Add your fresh water weight (how much lead you need)
-Add 40 lb for the tank

Add 1 lb for every 40 of the total.

Me: 190 lb in gear
10 lb of lead in fresh
40 lb tank (when empty)
---------
240 lb total land dry weight

240/40 = 6 = I need to add 6 lb of lead to switch to salt in the same config.

Enjoy!

Ed66:

Well I am going fron a Parkway 7mm one pc. to a Henderson 5mm Instadry. Right now my current setup is Parkway 7mm one pc. Halcyon SS backplate (6lbs) 36 lb wing, Steel 100 HP Tank, and 10 lbs weight on the weightbelt and I have my Buoyancy on the money now(still slightly neg). I was told I might be able to drop the belt altogether once I switch to the Instadry. I have also hear that the 5mil Instadry is a warm as 7mil reg suite, is this true?? Thansk Ed
PS I add 4lbs to this for salt

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It's hard to beat this method:

Do your usual dive, have several small weights making up an abundance for your dive.

At your safety stop, suck the air down to 500 psi. Totally relax your body (stop all finning) Then ditch little by little of your lead until you are able to maintain your depth with the least lead possible.

Rationale: you will have squeezed all of the captive air out of your gear; you will have the least possible weight to contend with; You will have targeted your lead load to the critical phase of your dive when your tank will be its most buoyant, and when you NEED to stay at safety stop depth.

Most divers are overweighted.

The one piece of information needed for the answer is missing from your post.
What area (sq ft or m2) of your body is covered in neoprene.
If you Google around you will find various formulae for body superficial area.
In my case I wear 1,96m2 of neoprene which makes it very easy to figure out how much water is displaced by each mm of thickness. That is, at the surface before compression comes in to play as you descend.
At depth it depends on the compressibility of the neoprene.

The age of the 7mm may also play a factor --if it is old, it may have lost some of its buoyancy and, therefore, they weight difference may not be much at all.

Jeff

miketsp:

I wear 1,96m2 of neoprene which makes it very easy to figure out how much water is displaced by each mm of thickness. That is, at the surface before compression comes in to play as you descend.

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That just sets an upper bound of 4.4lbs per mm (for a wetsuit with zero weight). You need to subtract out the weight of the neoprene to get the actual buoyancy per mm --- which will be in the range of 2 to 3 pounds per mm of thickness.


4 pounds is a good starting point for adjusting from 7mm to 5mm.