weight question

[Strick]

Someone told me a while back to take your weight, divide it by 10 and you have your weight requirement when using a 5mm suit. Then add about 3-4 lbs for the empty tank.

120 lbs = 12 lbs weight + 4 lbs = 16 lbs
130 lbs = 13 lbs weight + 4 lbs = 17 lbs
140 lbs = 14 lbs weight + 4 lbs = 18 lbs
150 lbs = 15 lbs weight + 4 lbs = 19 lbs
etc...
etc...

Less weight would be required for dives with out a suit, skin or a 3mm suit.

Then again, Their advice could be all wrong. I use 18 lbs and it works good for me. I do however need to refine it since I have replaced some equipment with better quality stuff.

 

[roakey]

Originally posted by Strick
Someone told me a while back to take your weight, divide it by 10 and you have your weight requirement when using a 5mm suit. Then add about 3-4 lbs for the empty tank.

Though formulas such as this will get many folks in the ballpark, they fail to account for how innately buoyant the person is.

A 150-pound triathelete is going to require less weight than a 150-pound butterball, yet your formulae will yield the same amount of weight required for both people, and given these two extremes I bet it would be incorrect for both.

So what do you do? Well, after blasting your formula, if you’re of fairly normal build go ahead and use it as an initial guess and experiment. Turns out that your formula computes my weight requirements correctly (I guess I’m just an average guy ) though with a 7/5mm suit.

Roak

 

[Butch103]

another welcome and for what it is worht....I too used 40# when I first started diving. I am now downto 36# (a little heav) with a full 7mil suit. i find it best to split the weight with a wi BC. Some on the BC and some on a belt.........good luk and welcome to the club............Come on up to Kingston some time and a bunch of us will get together...........

 

[Ontario Diver]

Another welcome to the board! I'm just down the street (well in Toronto anyway ) I started in 40 lbs and now I'm down to 32. I also did the weight slip thing, except mine was as 80 ft. and it came right off - I managed to catch it before it went down and I went up.

Drop me a PM and let me know where you did your training. And by all means, join the group in Kingston and Brockville come this summer!

 

[sharkkbait]

Hello everyone. I have a question about my wieghting. I will be diving in saltwater in Cozumel in a week. I will be wearing a new 3/2 Mares full wetsuit.( first time for a 3 ml) wieght intigrated BC , no hood or beanie, a skin, no knife, no gloves, fins which are positively bouyant. I am 5' 6" at 155 lbs. I am a very bouyant person with a body mass inticator of 26. My question is...Am I correct in calculating about 16 lbs of wieght? Any corrections would be appreciated. Thanks

Cindy aka: mathwoos

:embarrass

 

[Ontario Diver]

Check out this link: http://www.scubadiving.com/training/instruction/buoycalc/buoycalc.shtml

It might help. I am guessing that you are pretty close, but I would try first by adding a couple of pounds. I dove with 16lbs in salt water with a AL80 and a 3mm shorty. I'm 6 ft even and my BMI is 27. You're 3/2 3mm will add more bouyancy than I had.

IMHO, You are better to be too heavy (Granted, you use more air and you'll be less streamlined when you inflate your BC) but you might find that you are more comfortable . (You'll submerge easier and you will have less chance of runaway ascent.) As you learn more about how you float in salt water, you can adjust the weights.

I'd also encourage you to try your gear in a pool with a DM or DI in Ottawa and do a real bouyancy check. You can then do a simple calculation to translate from the fresh water to the salt.

I'll think of you in Coz as I'm shoveling the driveway

 

[sharkkbait]

For the info OntarioDiver. I just looked at the site you posted and it looks like it will be very helpful to me. I have another short question. With regards to the Nitrox course. Would a "severely mathamaticly challenged" ( and spelling challenged it seems) person such as myself have a great deal of difficulty with the Nitrox course. I understand that there is a great deal of...equations to calculate?? I am really bad at math. Humourously so in fact. :hehe:

Regards....

Cindy

 

[Ontario Diver]

I did the Nitrox course in mid december up in Morrison Quarry over past Hull. - Durn cold. Did three dives (wet). two of them to 90'. I found the course pretty straight forward with the only difficult part being that I had to stay awake during the video (and if you want to do another specialty - I think that you can combine the dives with the check dives for the other spec course.)

So I can in fact recommend a good instructor. Why don't you PM me with which LDS you want to do it with.

You can pretty well do the PADI Nitrox course off of tables. If you are good with the rec tables, you should have no problem with the additional load for Nitrox (and if you aren't good with the tables....get good!)

Under Nitrox you manage your pressure groups just like you did in OW/AOW, but you have to track your Oxygen exposure as well.

There are three equations that you have to know, but they are pretty simple. The equations are the same that they used to build the tables. You can use them to get actual numbers rather than the round-offs that the tables give you. Of the three, I have found only 1 is really critical. (that one is the max Operating Depth for a specific O2 mix).

Other than that, there is not a lot of calculations beyond what you learned in OW. Just more of them.

Hope that this helps......if you want more data, just PM me.

Oh and my University degree is in Math - so you might not want to trust me on that one. :tease:

 

[FredT]

I am 5' 6" at 155 lbs. I am a very bouyant person with a body mass inticator of 26. My question is...Am I correct in calculating about 16 lbs of wieght?

The 3/2 should be between 4 and 6 pounds positive at the surface. At the depths common off coz you should be able to cut that a pound or two if you're willing to keep active control of your buoyancy on the way up. If you intend to haul your gear south instead of renting a quick pool check will fine tune it a bit.

As a rule women take more lead than men to get neutral. The basic rule is that fat floats, and women with NO body fat just don't look like women. :egrin: "Sinker" males are relatively common. In 32 years of diving I've only met one female that sank in salt water, but I know several men that do. Muscle and bone sink quite well. If you have exceptional thoractic buoyancy reserves a high trim weight can be used to offset the buoyancy stackup of both lungs and breasts being at the same place longitudinally. Alternately you could use a backplate system to get the same effect.

If you take your "swimsuit only" weight requirements (correcting for saltwater by multiplying your total weight _with_ freshwater ballast by 1.02) and add 5 pounds you should be in the right ballpark for the suit. Proper placement of the weight to get a horizontal trim in the water may decrease the total lead required by a couple of pounds though. Be aware you may trap a bit of air in the suit when you first get in the water, so taking care to ensure the suit is fully flooded before doing a final weight trim will give you a better answer. The trapped air will work out of your suit during the dive, partially offsetting the weight of the gas breathed and lost from the tank. Just jumping in adjusting ballast with an "empty" tank will yield a different answer than doing the ballst adjustment at the end of a much longer dive.

BTW The Nitrox course just has ONE equation, it's simply rewritten into 3 different forms. No (or minimal) skull sweat is required.

FT

 

[Arduous]

I agree with herman. Do a weight check in the water before each dive and note the results of your buoyancy. It should only take a few dives to get it right. Then keep a log of your weight requirements for that equipment configuration. As your equipment varies so will your weight requirements. Keep a log that you can refer back to and this will take the guess work out of your weighting needs. ( Of course that is once you have established what those needs are )

Dive Safe ………………Arduous