weighting with a 7 mil suit

[SkipperJohn]

6'3 205lbs. I dove with a vest, al80 & no wetsuit in salt and needed around 20 pounds. I had to add another 12 pounds when I dove a 7 mil still in salt.

I too am diving Cozumel this November with my dive club. I was advised to get a 3 mil full suit for the trip. I have a 3 mil shortie but was told that 2 dives per day for 5 days straight i'd get chilled. While I highly doubted it, I did consider the fire coral and jellies.

 

[D_B]

I dived a 3/2mm suit in 80f water and was fine, had to use 5mm gloves though on the 5 dives a day liveaboard .. I'm thinking that a 3mm and "reef gloves" would have been perfect at those temps

Your gonna need a very good suit 7mm suit for those cold waters where you live, I would only get one with Rubatex Neoprene (like wetwear ... http://www.wetwear.com/rubatex.htm)
Although, I would start saving for a drysuit

 

[tporritt]

Thank you all who posted.... I opted on a 7 mil 2 pc..... from Oceaner, dove in waters that were 50 degrees and I was toasty warm... I opted for the 2 pc so I can use the upper portion as a Shorty for warmer dives.

Thanks again everyone, I really appricate your input.

 

[Hoomi]

I think a little mathematics would help here. Fresh water is 8 pounds per gallon, while salt water is 10 pounds per gallon (I had a lot of fish aquariums as a kid, and learned real quick to make proper calculations for how much water weight I was going to be pouring in). Freshwater is 80% of the weight of saltwater, and saltwater is 125% of the weight of fresh.

I'm sure the more experienced folks will correct me if I'm wrong here, but thinking logically, it would seem the ratio would be 4/5 or 5/4, depending on which way you're going. I.E., 4/5 of the weight you need in saltwater for equal buoyancy in freshwater, or 5/4 of the weight you need in freshwater for equal buoyancy in salt.

For those of you who have been doing this for a while, does that ratio seem to correspond to what you find with the same basic set-up in fresh versus salt water? I know varying conditions are going to call for adjustments, so I know it's not going to be a hard-fast rule for every situation. However (again, thinking logically which may not be right), it seems to me that I'm going to displace the same volume of water whether fresh or salt, and since buoyancy is the equation of weight of the object versus the weight of the water being displaced, it should track fairly close.

 

[gcbryan]

I think a little mathematics would help here. Fresh water is 8 pounds per gallon, while salt water is 10 pounds per gallon (I had a lot of fish aquariums as a kid, and learned real quick to make proper calculations for how much water weight I was going to be pouring in). Freshwater is 80% of the weight of saltwater, and saltwater is 125% of the weight of fresh.

I'm sure the more experienced folks will correct me if I'm wrong here, but thinking logically, it would seem the ratio would be 4/5 or 5/4, depending on which way you're going. I.E., 4/5 of the weight you need in saltwater for equal buoyancy in freshwater, or 5/4 of the weight you need in freshwater for equal buoyancy in salt.

For those of you who have been doing this for a while, does that ratio seem to correspond to what you find with the same basic set-up in fresh versus salt water? I know varying conditions are going to call for adjustments, so I know it's not going to be a hard-fast rule for every situation. However (again, thinking logically which may not be right), it seems to me that I'm going to displace the same volume of water whether fresh or salt, and since buoyancy is the equation of weight of the object versus the weight of the water being displaced, it should track fairly close.

Salt water on average is 2.8% more dense than fresh. Take your body weight and gear weight and add 2.8% of that number when going from fresh water to salt water.

If you and your gear combined weigh 200 lb then you add 200x .028 = 5.6 lb

 

[Hoomi]

Interesting; so using the density factor of .028, the calculation would indicate that, with a combined weight of 200 pounds, if the diver needed 12 pounds of weight in freshwater, he would bump up to 17.6 pounds for seawater.

Am I understanding that correctly?

Again, though, a number of factors are going to affect it, including seemingly imperceptible day-to-day changes in our physiology, water temperature (another lesson from salt water aquariums), actual salinity of dive location, etc., but the 5.6 pounds would present an approximate start point, with adjustments made as necessary after a buoyancy check.

Thanks; I'm going to play around with that math this week, and see how well it corresponds from the the pool dives we've done recently to the ocean this coming weekend.

(That isn't an "I'm doubting you" statement. I just find most math makes more sense to me when I get to apply it in real-life situations, rather than hypothetical problems. I hated math when I was in school, which makes my choice of electronics for a career rather ironic...)

 

[fnfalman]

I just went and did some freshwater diving. The difference for me was 2-lbs.