another weighting question

[TMHeimer]

I'm going South intending to use my shorty. I know the only way to get weighting correct is the buoyancy check, but am trying to decide whether to bring weights or rent. Here is my set up:
--Diving salt water with 7 mil and AL80 I need 40 pounds (I know, it seems like a lot-with my steels I need 34).
--In the pool (fw) with my shorty I wear the 12 pound belt (it's that or the 8 pounder provided by the LDS-which is way too little).
--PADI manual says for my body weight (approx.200) add 7 lbs. going to sw. So that's 12 + 7=19).
It says for a 7 mil I should add 10% (20 lbs.) which I do. It says for a shorty I should add 5%--so that would be 10 lbs. instead of 20. That means my total in sw with a shorty should be 10 lbs. less that the 40 I use with the 7 mil= 30 lbs.

There's a big difference between 19 and 30 pounds.. Did I get my figures mixed up or leave something out?

 

[divinginn]

A shorty and a steel tank I would use 4-6 lbs. I use 6lbs with a full 3 mill.

 

[Jorgy]

If flying south rent weights...

If driving bring them...

Not 100% sure where you are going but most places I have been tanks and weights are included with the dive charter.......

M

 

[TMHeimer]

Yeah, renting is probably the thing to do, as we are flying. We're hopefully going to S. Padre I., TX. Hope to do a couple of oil rig dives, but hopefully a shore dive or 2 first when I could do a weight check. Any other comments on my figures?

 

[JohnB47]

Something doesn't sound right in your buoyancy calculations. Is your 7mm suit a full suit, or is it a farmer john and jacket? What size is it, L/XL/XXL? Unless your suit is a farmer john and jacket, I can't figure out how you could need 40 pounds. If you wear a 7mm XXL full suit, that should be about 22 pounds in fresh water. Add 5 pounds for your buoyancy in salt water, and another 4.5 for the buoyancy of the AL80 when empty. That should be about 31.5 pounds. I'm 5'10" and weigh about 230 pounds. Wearing an XXL 7/6mm full suit and a steel HP 100, I need about 26 pounds in salt water. Since the steel tank is -2.5 pounds empty, I would add 7 pounds for an AL80. For a full 7mm suit, maybe add another 2 pounds for a total of 35 pounds.

As for your shorty... (I don't know why your manual says 7 pounds for salt water... salt water weighs 64 pounds, and fresh water weighs 62.4 pounds per cubic foot. You calculate the difference by multiplying your weight by (64/62.4 - 1 = 0.0256) ) If you are around neutral buoyancy in fresh water without a wetsuit, you should need about 5 pounds (200 x .0256 = 5.12) more in salt water. So, if your buoyancy is right with the shorty in freshwater with 12 pounds, you should need about 17 pounds in salt water. That still seems like a lot, but it could be right. I am sure you will not need more than 20 pounds with the shorty. My best guess would be 18 pounds.

 

[Bubbletrubble]

--In the pool (fw) with my shorty I wear the 12 pound belt (it's that or the 8 pounder provided by the LDS-which is way too little).
--PADI manual says for my body weight (approx.200) add 7 lbs. going to sw. So that's 12 + 7=19).
It says for a 7 mil I should add 10% (20 lbs.) which I do. It says for a shorty I should add 5%--so that would be 10 lbs. instead of 20. That means my total in sw with a shorty should be 10 lbs. less that the 40 I use with the 7 mil= 30 lbs.

There's a big difference between 19 and 30 pounds.. Did I get my figures mixed up or leave something out?

You've already gone to the trouble of doing a "weight check" in the pool with all of the gear that you'll be bringing to Texas. Personally, I would have borrowed some other weights to determine whether 10 lbs. might have been the correct amount of weight.

OK, let's assume that you are properly weighted in a pool with 12 lbs. of lead with all of the gear you'll be using in Texas. Great. Calculate 2.5% of your total weight (yourself + all gear). This is about how much extra lead you'll need. For example, if your total weight (yourself + all gear) is 240 lbs., then you should add 6 extra lbs. when moving to salt water. That should get you very close to how much lead you'll need in the Gulf of Mexico. Of course, there's no substitute for doing a proper weight check once you get to your destination.

Just another comment. You have 100+ dives now. Stop paying attention to the ridiculous "rules of thumb" printed in the PADI manual. You know better. People have different body types. Wetsuits have different amounts of buoyancy. With use, neoprene wetsuits become more compressed, and you'll find that over time your weighting requirements will decrease.

Have fun on your trip...

 

[TMHeimer]

Thanks guys. I have a farmer john/jacket XL 7 mil, thus the 40 pounds needed, I guess. I was checking the manual because I've never dived with a thinner exposure suit. Actually, I was assisting with an OW class in the pool last Fall. Would've done an exact weight check, but we had no plans for Texas. So my wearing the 12 pound weight belt was not very exact as to what I needed. I know everyone's different, and will do a proper check if the LDS books the pool before we go (it's 50 miles away). Anyway, appreciate the help. I must've miscalculated something in my data. Oh, the Adventures in Diving book says "add going to sw: if body weight is 187-217 add 3.2 kg/7 lb".