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shawnwill36
01-21-2009, 07:08
i am about to do my first ocean dive. i will be going on a cruise and would like to get an idea of how much weight i will need before i get there. in fresh water and a 3 mil i use 4 lbs. how much should i try in salt water without the wet suit? and how much with a 2 mil shorty?

nrembis
01-21-2009, 07:38
bout 7-8.... I'd rather be 1-2 pounds over than under

DMWiz
01-21-2009, 08:43
All things being equal (Suit, Tank, etc.) you should add about 4 pounds of additional weight for salt water. Most likely they will have you perform a buoyancy check before you actually dive if you're diving with the cruise line tour.

WV Diver
01-21-2009, 08:56
Eight pounds sounds about right. You sound like your weight requirements are nearly the same as mine. I wear a 3mm full suit in freshwater and since I have a SS Back plate I wear 6lbs, but 4 is much closer to what I really need. When I dive warm ocean I switch from the 3mm full to a skin and add 2lbs.

If you are diving with 4 lbs in Freshwater with your limited experience that is very good. You must be a natural, most folks don't drop a lot of weight until they have had more experience. Are you closer to 25 dives or 50?

wheelman
01-21-2009, 10:17
I found this post a while back and keep it around for a quick reference...

Buoyancy Example
A 150 lbs diver wears a 10 lbs weight belt to become neutrally buoyant in fresh water.
How much more weight will they need in salt water ?
Diver Total Weight = 150 lbs + 10 lbs = 160 lbs
Since the diver is neutral the force of buoyancy matches the diver's weight = 160 lbs
The amount of displaced fresh water required to generate that buoyancy
= 160 lbs / (62.4 lbs/cu ft) = 2.564 cu ft
That volume will create a larger buoyancy force in salt water
= 2.564 cu ft x 64 lbs/cu ft = 164.1 lbs
This increase buoyancy force can be compensated by adding more weight to the weight belt
= 164.1 lbs - 160 lbs = 4.1 lbs added

bubbletrubble
01-21-2009, 10:24
i am about to do my first ocean dive. i will be going on a cruise and would like to get an idea of how much weight i will need before i get there. in fresh water and a 3 mil i use 4 lbs. how much should i try in salt water without the wet suit? and how much with a 2 mil shorty?

What kind of tank were you using in fresh water?
Do you plan to use the same kind of tank when you dive in salt water?
Tank type can make a significant difference in your weighting requirements.

It sounds like you'll be doing some diving in water warmer than you're used to. Consider wearing the 3mm wetsuit anyway. It'll provide more protection against abrasion and stings.

Due to the difference in density between salt and fresh water, you'll need to add enough lead to equal 2.5% times your total weight (person + rig). For instance, if you weigh 160 lbs. and your rig weighs 40 lbs., then you'll need to add 5 lbs. of lead going from fresh to salt water. Keep in mind that this calculation only works if you're using an identical rig in both situations. Changing gear may alter your weighting requirements. Refer to this link (http://forum.scubatoys.com/open-water-diver/14521-bouyancy-fresh-vs-salt-water.html#post191609) for a more detailed explanation.

For optimal weighting, there's no substitute for a proper weight check.

Hope this helps...

bubbletrubble
01-21-2009, 10:29
I found this post a while back and keep it around for a quick reference...

Buoyancy Example
A 150 lbs diver wears a 10 lbs weight belt to become neutrally buoyant in fresh water.
How much more weight will they need in salt water ?
Diver Total Weight = 150 lbs + 10 lbs = 160 lbs
Since the diver is neutral the force of buoyancy matches the diver's weight = 160 lbs
The amount of displaced fresh water required to generate that buoyancy
= 160 lbs / (62.4 lbs/cu ft) = 2.564 cu ft
That volume will create a larger buoyancy force in salt water
= 2.564 cu ft x 64 lbs/cu ft = 164.1 lbs
This increase buoyancy force can be compensated by adding more weight to the weight belt
= 164.1 lbs - 160 lbs = 4.1 lbs added

@wheelman: Nice example, but you're forgetting to consider buoyancy changes contributed by the diver's rig (BCD, reg, etc.).
The 1.6 lb. difference in density roughly translates to 2.5% (1.6/62.4).

shawnwill36
01-21-2009, 10:31
i was using an al 80 in fresh, i will be using the tank from the dive op. i have had 26 dives so i am still inexperienced. i am very excited about doing my first ocean dive. i guess i will know once i get there. thanks to everyone for your posts

wheelman
01-21-2009, 10:34
Agreed about the buoyancy changes for kit changes... but not a bad starting point if your going from fresh to salt with the same gear.

bubbletrubble
01-21-2009, 10:52
i was using an al 80 in fresh, i will be using the tank from the dive op. i have had 26 dives so i am still inexperienced. i am very excited about doing my first ocean dive. i guess i will know once i get there. thanks to everyone for your posts
The AL80 is the typical rental tank at warm water destinations, so 8 - 9 lbs. of lead should get you in the ballpark of proper weighting.

Have fun and dive safe.

heydn62
01-21-2009, 21:14
And don't forget, the original poster had a 3mil suit in the fresh water and asked about no wetsuit (or shorty) in saltwater, so there may not be that much more needed. Of course, you can compensate for too much, but if you don't have enough, your just snorkeling. :smiley20:

Keep in mind, I've still had less than 25 dives, so I don't know as much as most of you guys around here. :smiley13:



I found this post a while back and keep it around for a quick reference...

Buoyancy Example
A 150 lbs diver wears a 10 lbs weight belt to become neutrally buoyant in fresh water.
How much more weight will they need in salt water ?
Diver Total Weight = 150 lbs + 10 lbs = 160 lbs
Since the diver is neutral the force of buoyancy matches the diver's weight = 160 lbs
The amount of displaced fresh water required to generate that buoyancy
= 160 lbs / (62.4 lbs/cu ft) = 2.564 cu ft
That volume will create a larger buoyancy force in salt water
= 2.564 cu ft x 64 lbs/cu ft = 164.1 lbs
This increase buoyancy force can be compensated by adding more weight to the weight belt
= 164.1 lbs - 160 lbs = 4.1 lbs added

@wheelman: Nice example, but you're forgetting to consider buoyancy changes contributed by the diver's rig (BCD, reg, etc.).
The 1.6 lb. difference in density roughly translates to 2.5% (1.6/62.4).

5513
01-22-2009, 00:45
I found this post a while back and keep it around for a quick reference...

Buoyancy Example
A 150 lbs diver wears a 10 lbs weight belt to become neutrally buoyant in fresh water.
How much more weight will they need in salt water ?
Diver Total Weight = 150 lbs + 10 lbs = 160 lbs
Since the diver is neutral the force of buoyancy matches the diver's weight = 160 lbs
The amount of displaced fresh water required to generate that buoyancy
= 160 lbs / (62.4 lbs/cu ft) = 2.564 cu ft
That volume will create a larger buoyancy force in salt water
= 2.564 cu ft x 64 lbs/cu ft = 164.1 lbs
This increase buoyancy force can be compensated by adding more weight to the weight belt
= 164.1 lbs - 160 lbs = 4.1 lbs added

Loads of good information. I am 6'0" and 240 lbs. Mostly fat. I use 8 lbs in fresh water/no suit and 14 in salt water/no suit. Hope that helps.

chris in the socal
02-09-2009, 14:36
I would have to say about 7 to 8 lbs

mksmith713
03-30-2009, 09:00
Look it up in the Adventures in Diving book you used during AOW.
They have a chart in there with "Rule of Thumb" weight guides.
I found them to be pretty accurate.

navychop
04-25-2009, 09:58
I'm 180, with a 5mm suit, I add 4 lbs, moving up from 8 to 12 pounds. Since you are going on a cruise, the dive op will provide the weights and have spares to add as you need them. Be the first to do a bouyancy check when you splash in. We love diving on cruises. Did that in March, got to dive in Mahahual, Belize and Cozumel and don't have to worry about flying :o) the next day. Have a great trip.

Vlane
05-06-2009, 01:03
Here's PADI's table from their Peak Performance Buoyancy chapter, can't vouch for how accurate it is though.
http://img23.imageshack.us/img23/4594/scubaweighting.jpg

DiverDurf
05-24-2009, 00:23
You'll get a kick out of this lesson I recently learned. Like you, I went on my first ocean dive a couple of weeks ago with a charter. I wear a 3mm suit and jacket style BCD and 12lbs lead in the fresh water springs around FL (I'm 194lbs). I had someone tell me to try an additional 6lbs for the ocean so I did so with a weight belt and kept the 12lbs in my BCD. First dive had a somewhat slow decent but no problem and all was well (except for the 4-6' seas that I never care to dive in again). Second dive, in we go like cattle off the boat and I'm really struggling to descend. I finally exhale everything and hold my breath and eventually make my way down. Came up for our safety stop and had to use some serious breathing technique to stay at 15'. Back on the boat I make my way to my seat and "BAM!".......there my weight belt with my extra 6lbs sits from my 1st dive, LOL! No WONDER it was so hard to descend and make the safety stop. But......I did that entire dive with just 12lbs- the SAME weight I use for fresh water. Guess I didn't need that extra 6 after all. ;-)

larrymck
05-09-2010, 18:55
Wow, just found this. Now I understand what I already knew. Thanks for posting the details that I have listed below.
:smiley20:


I found this post a while back and keep it around for a quick reference...

Buoyancy Example
A 150 lbs diver wears a 10 lbs weight belt to become neutrally buoyant in fresh water.
How much more weight will they need in salt water ?
Diver Total Weight = 150 lbs + 10 lbs = 160 lbs
Since the diver is neutral the force of buoyancy matches the diver's weight = 160 lbs
The amount of displaced fresh water required to generate that buoyancy
= 160 lbs / (62.4 lbs/cu ft) = 2.564 cu ft
That volume will create a larger buoyancy force in salt water
= 2.564 cu ft x 64 lbs/cu ft = 164.1 lbs
This increase buoyancy force can be compensated by adding more weight to the weight belt
= 164.1 lbs - 160 lbs = 4.1 lbs added