Trim and Weighting question

[ScubaWulf]

Doing my first real dives in a couple of days. Spent about 5 days working in the LDS pool dialing in my new BC working on trim and buoyancy. In the end wearing my 3 mil full suit, boots, Oceanic Viper fins, and Zeagle ET I ended up with 3 pounds each for the side zip pockets and 2 pounds each for the upper tank band weight pockets I added. Scrawny chicken legs of mine just do not float!!

Question is, going to saltwater I figure about 6 lbs of added weight. Looking to put 5 pounds in each zip pocket and 3 pounds in each tank band pocket. Just wanted to ask experienced divers if my logic sounds good? I'm about 174 pounds, equipment is about 23 pounds, add a 31 pound Aluminum 80 and multiply by 2.5% gets me about to 6 pounds? Sound okay? Hopefully the weight distribution works out well too. Tried 2 pounds in each pocket all the way around and every now and then felt like I was going head down feet up.

Thanks,
Jeff

 

[Bubbletrubble]

Jeff,

Assuming that you were properly weighted for the pool and that your gear remains the same, I'd say that adding 6 lbs. would be appropriate when moving to saltwater. Do a proper weight check when you get to your destination. As you know, you can easily do this with a full tank...just compensate for the weight of the gas in the tank.

With regard to positioning of that weight so that it promotes good static horizontal trim, you need to determine that by trial and error. As you gain experience, you'll realize that body positioning is an important factor in horizontal trim.

Have fun on your dive trip...

 

[ScubaWulf]

Thanks for the reply. I ran a tank down to 500 pounds and could float at eye level and sink when I exhaled. For body position I worked and worked it but couldn't do it without the extra weight up higher. I'm one of those that could never float on their back cause my legs would always sink. I'm sure I looked silly in the pool stretching and arching trying to get my knees up. Would always drop right back down as soon as I stopped finning. Interesting thing is that if I went by My AOW book my freshwater weight would be about the same but moving to salt water would put me at 20 pounds which I'm sure would be too much.

 

[TSandM]

Well, the ballpark figures in the books are only that . . . people are quite different in their composition (muscle, fat and bone) and gear is different, too (some BCs are floatier than others).

Your guesstimate sounds reasonable to me. As BubbleTrubble says, getting the weight perfect for trim is a trial and error process -- and remember that aluminum tanks get butt-light when empty, so if you are perfectly trimmed out with an empty tank, you may be a little foot-heavy at the beginning of the dive. Posture will minimize the effects -- head up, body flat and knees up gives you the most stable platform.

 

[spectrum]

ScubaWulf

You have the process down.

Was the cylinder at ~ 500 PSI? If higher you need to add lead to hold you down at the end.

As mentioned different gear properties may throw it off a tad.

Pete

 

[Necklinsberg]

Have your LDS take pictures of you when you feel that you are properly & when trimmed out of balance. Compare how you actually 'look' vs. how you 'felt' you were oriented.

You probably shouldn't rely on 'feel' at this point. We spend most of our waking live upright. Being & moving horizontally requires changes in everything we think of as 'normal'

 

[MauiScubaSteve]

head up, body flat and knees up......

The image my mind comes up with from this description is a supine fetal position, or one of my ab workout positions

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I am of the opinion that this is something like what the vast majority of open water divers should be striving for when locomoting. When hovering, some divers might put "fins" up and move hands/arms out in front.

A person with "lead legs" might also have "lead arms" so under locomotion the first adjustment might be "arms in front" similar to below...

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[LakeCountyDiver]

6 pounds is good to start with. You may want to take in to consideration that in the ocean your exertion level may be up a little from say the pool where you probably were at your very calmest. With your exertion lever higher you may be breathing deeper therefor having more air in your lungs thus making you more buoyant.

With a 3mm suite you are not going to lose a lot of +buoyancy due to compression since there is what 6lb+ to start.

What I am saying is don't be discouraged if you need more weight cause hey you may need less.

 

[MauiScubaSteve]

....Interesting thing is that if I went by My AOW book my freshwater weight would be about the same but moving to salt water would put me at 20 pounds which I'm sure would be too much.

Has the Adventures in Diving book changed?

The Basic Weight Guidelines box on page 213 of my Adventures' book shows 5% of body weight for 3 mm wet suit (8.7 lbs) and then the saltwater change is add 6 lbs for your "body weight" (14.7 lbs).

 

[dkktsunami]

Yes, six pounds additional for an average sized diver is about correct.