Lest problem

[Bretagne]

I am still struggling with my lest adjustment.
The problem I have is the following: either I am way too heavy at the beginning of the dive (just need to purge the air from BC and I go down-slowly, but way too easily), or i am way too light at the end of the dive and I cannot make my safety stops... if I use more than half my air. (hopefully, I always was well into security limits when it has arisen)

I would interpret it as a problem of wet suit compression: my wet suit is not compressed enough when I dive, or does not stay compressed when I go up, thus cannot compensate the weight loss due to air consumming. If I dive deeper (100ft) I do not have this problem, may be because the suit is more compressed?

My wet suit is a Cressi Lontra 7+5mm, problem arise wether I use the shorty or not.

My questions: do you think my diagnostic is correct? Do you know people who have had the same problem? Will it improve when my wet suit get older (I used it only for 15 dives)?

 

[Blowin Da Bubbl]

Always weight for the end of the dive dont be concerned with beggining. Being able to easily drop feet first is a good thing. I cannot stress how important it is to have enough weight.

B.D.B

 

[NEWreckDiver]

I think you understand your problem. Wet suits compress the deeper you go. Yes by all means, you do weight yourself for the end of the dive and not the begining.

You may want to consider a dry suit at some point, you have much less of this type of problem.

DSAO

 

[turnerjd]

ceinture de lest = weightbelt
lestage = weight (or more correctly ballast)

Your problem is not due to the neoprene compressing at all. If you are doing your stops at 5m then your suit will be pretty much uncompressed at this point. As you descend the suit compresses. As you ascent, the suit will uncompress at the same time.

The problem is the weight change in your tank as you use the air. A full tank weight (depending upon tank size and pressure) will change by over 1Kg from full to empty. Now, as the tank size doesn't change, this will change your buoyancy.

You have to start every dive overweighted, by the amount that the tank weight will change over the dive. OK?

Don't worry about being overweight at the start..... its the end that is important. You don't want to be so weighted that at the end you are overweighted either. There is a fine balance to find here.

If your weighting was OK on some deeper dives, I suggest that you look at exactly what size tanks you used (12L, 15L 18L?) what pressure they were filled to, and how much weight you used. This is where you will find the explanation for your acceptable buoyancy on these dives. (if you used 2 first stages instead of 1, there is also an extra 1/2 kg of weight there that needs to be counted)


J'espère que je vous ai aidé (HTH for the rest of you)

Jon T

PS et oui..... une combi étanche sera bien utile dans l'atlantique!

 

[DA Aquamaster]

Ideally you would weight yourself so that at the end of the dive with very little remaining air (500 psi or 30 bar) and no air in the BC, you will float at eyeball level in the water with full lungs. You should then sink when you exhale.

Weighted this way you will always be 3-5 lbs heavy at the beginning of the dive (depending on tank size). Wet suit compression will also alwyas be a factor at depth but the BC is designed to compensate for these effects during the dive.

 

[Arnaud]

Ideally you would weight yourself so that at the end of the dive with very little remaining air (500 psi or 30 bar) and no air in the BC, you will float at eyeball level in the water with full lungs. You should then sink when you exhale...

You should be neutral with an empty BC at your last stop before surfacing, slightly ascending when you inhale, and slightly decending when you exhale.

Question though, how old is your wetsuit?

 

[Bretagne]

Almost new (15 dives with it).
turnerjd, I know that it is a matter of air quantity in the bottle. 12l x150 bars X1,3 gl -> 2,34 kg , difference between 200 bars and 50 bars.
Now what i had been told was that this was usually corrected by compression of wet suit, which does not regain its volume very fast, and is still partially cmpressed on return. It seems that in my case it is false, but I wanted to be sure. Because there was no difference of material between deeper dives and more shallow ones (same model of tank, same pressure, same regulator, same suit, same BC...)

PS: Pour l'instant, monopièce 7mm , +shorty 5mm à Pâques, ça me convient... Peut-être que si je me déplace de 20 km pour passer de la Manche à l' Atlantique çca n' ira plus

 

[Arnaud]

Neoprene, when new, tends to be a lot more buoyant. You should do a weight check often and you'll probably find out that you need less weight as time goes by.

 

[Bretagne]

Thanks. It will be nice to remove some weight.