Drysuit use and buoyancy

[lexvil]

Ok, when works for you?
Early December is when I’ll have the most free time, although we could schedule for early November as well.

That’s usually a good time for viz and unless a storm is brewing it can be great diving.

 

[jlcnuke]

Those diving drysuit, do you use it like a bcd or just adjust for squeeze and use bcd? Tried both ways myself. PADI try’s to tell you to use drysuit. Thankx in advance.

Use it for warmth only, avoid squeeze, but keep your buoyancy control in your buoyancy control device.

 

[Cdncoldwater]

Those diving drysuit, do you use it like a bcd or just adjust for squeeze and use bcd? Tried both ways myself. PADI try’s to tell you to use drysuit. Thankx in advance.

I primarily use my BCD for buoyancy, drysuit enough for squeeze and warmth (compressed neoprene). I will tweak my buoyancy occasionally with drysuit but I do that rarely. I've read using it as buoyancy control in my PADI manual but was also taught wing as primary, drysuit as back up on my drysuit and solo courses.

 

[jlcnuke]

In theory you should use your BCD for buoyancy control but in practice a correctly adjusted drysuit means you do not have to touch your bcd. At the surface fully deflate your bcd, you should not yet sink. Then fully open your drysuit shoulder valve and exhale, you should then sink slowly assuming you are correctly weighted. When submerged about 2 to 3 meters partially close your shoulder valve (usually about 3/8 or 1/2 torn on APEKS). At this point you should be neutrally buoyant and as a result have found your neutrally buoyant displacement. If not add a little air to the suit. You should be feeling a hint of suit squeeze but not uncomfortable. You should rise and fall as you breathe. As you descend add more air to your suit to keep the squeeze and displacement constant. At your chosen depth and with your left shoulder well above your feet open your shoulder valve until a few bubbles emerge then turn it back a click or two. Your buoyancy / displacement should now be correct, suit pinch minimal and your shoulder valve set so it will vent as you ascend, preventing excess ascend rate. You only need to re inflate your bcd at the surface. If you try to control buoyancy using both bcd and suit inflation whilst at same time as trying to control squeeze it is more complex and a mistake more likely to be made, particularly if you are trying to vent both suit and bcd at same time to control ascent.

Yeah, PADI teaches this method. It works "kinda well", right until you're diving doubles and have a valve failure that you have to send your left arm up to deal with the failure behind your head. At that point, you have a valve failure AND your buoyancy has just gone to absolute hell as you vent the buoyancy out of your rig when your arm goes up to close that valve. So you have a valve failure, down one reg, and you're descending uncontrolled until you can find a way to re-establish buoyancy again.

What works well always is venting/inflating your drysuit to just avoid squeeze throughout the dive and using your Buoyancy Compensating Device to Compensate for Buoyancy changes during your dive. Learning to do it well at the start, while a tiny sliver more complicated, prevents having to completely re-learn buoyancy management if you change your style of diving in the future.

 

[Wibble]

Does also depend upon the type of drysuit; neoprene or membrane/trilaminate.

Trilaminate is way more sensitive and easier to use for fine buoyancy control than a neoprene drysuit which is stretchy. For neoprene it’s more about relieving squeeze than buoyancy.

 

[drk5036]

Does also depend upon the type of drysuit; neoprene or membrane/trilaminate.

Trilaminate is way more sensitive and easier to use for fine buoyancy control than a neoprene drysuit which is stretchy. For neoprene it’s more about relieving squeeze than buoyancy.

I don't really understand this. Adding a little bit of gas provides the same amount of buoyancy either way. Due to their designs, tri-lams generally require more finesse, and neoprene suits generally dive more like a wetsuit. The squeeze in neoprene suits also isn't very bad; it's rarely painful and just feels "tight".

I think in a neoprene suit, using just the suit for both buoyancy and warmth is easy, especially during single tank diving. However I tend to use both now.

 

[Wibble]

My experience with different drysuits is that trilaminate/membrane suits are far more responsive than neoprene because the material does not stretch and is very thin. A small injection of gas into a membrane suit is immediately felt and changes one’s buoyancy.

A neoprene suit — especially a cheaper one— seems to be far less responsive, probably due to the thickness of the material and its natural stretch. Maybe this isn’t so much the case with a "hyper" compressed material.

 

[inquis]

At the surface fully deflate your bcd, you should not yet sink. Then fully open your drysuit shoulder valve and exhale, you should then sink slowly assuming you are correctly weighted.

When correctly weighted, you will be heavy at the start of the dive by the amount of air you haven't yet consumed. Even at 5 lbs of air for an AL80, I wouldn't say I'm sinking "slowly" (yes, even while still avoiding squeeze). Or to put it differently, it's typically too fast for the visibilities where I dive a drysuit.

The fact is we all have to compensate for that weight somehow. Trying to do that with the drysuit just vents unless I adjust the valve more closed or adjust body position to keep the valve lower than normal. However, I would rather keep that extra 2+ liters of bubble contained/localized in my wing. I can hold the wing inflator in the same hand that I use to (frequently) blip the suit for squeeze and just tighten my fist (occasionally) to slow the descent with the wing inflator.

 

[TuckerIdaho]

a drysuit should not be used as a primary source of buoyancy control. i am surprised padi would say otherwise.

A couple of the "big" schools were teaching this way until recently. SSI just switched last year.

 

[Wibble]

A couple of the "big" schools were teaching this way until recently. SSI just switched last year.

It's subtle and really depends upon the diver, the drysuit, their equipment and the environment.