bouyancy with dry suit

Question
I started using a drysuit and after diving with it for 6 dives I found the proper wieght needed. The only problem which I am encountering is that when ascending for the safety stop at 7-6mtrs I ascend to the surface because in the dry suit at the legs there is still air. I open all the exhaust valve during ascend and there is no air inside the suit (I think. Next dive I will use weights at my ankles to see the result. Can you help me as I cannot dive deep dives as until now I only dived at 26mtrs with the dry suit.

Thanks
Denis

Answer
Hi Denis,

I'm having a little difficulty trying to determine just what your problem may be.  If I assume correctly, you're telling me that you are becoming increasingly positively buoyant on ascent in your dry suit and you aren't able to vent any more air from the exhaust valves.  I'll base my answer on that assumption.

In order to vent the air from your suit, you must orient yourself so that air is directly behind the exhaust valve.  That means that your body orientation must be such that the air is forced into the proper area for venting.  Air will rise to the highest point available in your suit and that's where the exhaust valve should be.  For example, you can't vent air from the foot pockets if you're oriented so that you're head-down in the water.  All the air will run to the highest point (foot pocket) and there's no exhaust valve there.  I'm sure you already know that but it serves as an example of what I mean.  Air can also get trapped if you have compression rings on your lower legs so be sure that any air in your suit is free to move to the exhaust valves.  When making your ascent, be sure that you do so in a vertical head-up position.  Keep your arms down so air in your sleeves can move to an exhaust valve as well.  You've already determined the amount of weight you need so it's just a matter of redistributing it for the best positioning in the water.  Moving some of it to your ankles can help you achieve a head-up position for venting.

If you follow the suggestions I've given and if you remember to vent frequently as you ascend, you shouldn't have problems with the runaway buoyancy you mentioned in your letter.

One last thought to keep in mind.  Air will expand more quickly in the shallow water where you're doing your safety stop so you need to be especially vigilant in your buoyancy control in these shallow depths.

Denis, I hope this gives you the information you needed to prevent your unplanned ascents from your safety stops.

Happy Diving!!

Mike Giles
Mike's Dive Center
mikescuba.com