Another "help me with my weight" thread

[Jake]

Hi all-

After many years of not using a dry suit I am getting back into using one in order to start down the tech path. Last time I used twins and dry suit together was probably 10 years ago when I was 40 pounds lighter. And, as it's tough for me to get into a pool I want to try to approximate rough weighting and just head to the ocean. So...thoughts?

I'm about 230 pounds. In a full 7mm setup with steel backplate (~6lbs) and steel 100 I can get away with 16 pounds total (including the backplate).

Since I'm a little rusty on the dry suit I had to jump to 24 pounds total with the ST100. Hopefully that'll come down eventually, but let's assume it won't.

If I were to use my doubles, which are the same steel 100, what can I expect to drop in lead? 8ish pounds?

The tanks are Sherwood 100s, purchased probably around 2008ish. I haven't been able to find their buoyancy characteristics online so am just guessing at the -8 buoyancy characteristic.

Any thoughts are welcome. Thank you.

 

[decompression]

SCUBA Cylinder Specifications – Huron Scuba, Snorkel & Adventure Travel Inc. PADI 5 star IDC in Ann Arbor, MI


I don’t see the Sherwood’s on the chart but it’s likely they are neutral to 2 lbs neg when empty.

So, the neg weight won’t change significantly, really just manifold/bands etc. I’d try 24 lbs and do a weight check at 10’ with 500 PSI......that will get you in the ball park.

 

[Jake]

So, the neg weight won’t change significantly, really just manifold/bands etc. I’d try 24 lbs and do a weight check at 10’ with 500 PSI......that will get you in the ball park.

Jeez, I'm glad I asked. I would have been doing a surface swim the whole way back.

Edit: Looks like I was calculating a full tank. Not sure how I got that stuck in my head.

 

[swimlikethefish]

Using the 24 reference number. I'd say probably 20 lbs total depending on undergarments. You have the weight of the additional first stage, isolator, and bands. I'd take 22lbs and then start dialing it back to see where you should be.

For reference: a 100cuft tank holds about 7.5lbs of air full. Roughly every 500 psi is 1 pound. X2 tanks would be 15lbs of air. So you could do a weight check at the beginning of the dive. Get neutral, make sure all the air is out of the drysuit then add 14 to 16 lbs of weight. If done correctly you should be weighted appropriately.

Just giving you another way of doing it instead of wasting 2 tank fills or being drastically over/under weighted.

 

[Saboteur]

There is a great, extremely detailed spreadsheet for buoyancy calculations here on SB created by @rsingler that should be able to give you a very good estimate of how much weight you need no matter your setup.

 

[rsingler]

Optimal Buoyancy Computer

 

[W W Meixner]

Hi all-

After many years of not using a dry suit I am getting back into using one in order to start down the tech path. Last time I used twins and dry suit together was probably 10 years ago when I was 40 pounds lighter. And, as it's tough for me to get into a pool I want to try to approximate rough weighting and just head to the ocean. So...thoughts?

I'm about 230 pounds. In a full 7mm setup with steel backplate (~6lbs) and steel 100 I can get away with 16 pounds total (including the backplate).

Since I'm a little rusty on the dry suit I had to jump to 24 pounds total with the ST100. Hopefully that'll come down eventually, but let's assume it won't.

If I were to use my doubles, which are the same steel 100, what can I expect to drop in lead? 8ish pounds?

The tanks are Sherwood 100s, purchased probably around 2008ish. I haven't been able to find their buoyancy characteristics online so am just guessing at the -8 buoyancy characteristic.

Any thoughts are welcome. Thank you.

Hey Jake...

Dove tec configured HP steel 100's/80's recreational doubles for years...with dry-suit...I'm approx 180/185...no ballast...went for years without ever owning any...

Forget the calculations...too many variables...with a buddy...get in the shallows and perform a standard buoyancy check...start off with the lightest ballast first...

If your dry-suit fits properly and you've completely evacuated all the air...you should be dialed in within five minutes...

A properly fitting dry-suit/under-garment combo should be no more buoyant than a typical 7 mm wet suit...if it's too large...and the over-bulk is trapping air...that's where your problems are coming from and additional ballast to neutralize the trapped air does not solve the problem...it only adds to it...

Best...

Warren