5mm wetsuits – balanced, or not?
Hello, I just recently purchased a
Z-System and I’m taking an Es-
sentials class with you guys. I
know that a balanced system us-
ing a dry suit is the best way to go
diving.
Based on what I’ve been taught
so far, a 7mm wetsuit is unbal-
anced because of the weight
swing at depth. A 3mm wet suit
does not really have much of a
weight swing so it is considered
balanced. If I were to dive a 5mm
wet suit, would this be consid-
ered balanced or is it going to be
like the 7mm and be unbalanced.
I’m trying to not have to buy a
dry suit if I can help it. But I want
to be able to take all three Rec
classes and be able to dive to
the required depths safely. My
thought is because the 5mm is
closer in thickness to the 3mm
I shouldn’t have that much of a
weight swing and if I had a failure
of the wing at depth I would be
able to swim up.
If money was not an option I
would purchase a dry suit but I
don’t want to compromise my
safety either. Just wondering if I
can save a little money buying a
wetsuit over a dry suit?
Please advise.
You are correct on all counts regarding the 3mm/7mm/
Dry Suit, and you are also correct that 5mm is some-
where in the middle. For a completely balanced rig us-
ing a wetsuit, I like to use as a guide this question: can
I manage the buoyancy swing of the suit with just my
lungs. In the case of my 3mm suit, which swings about
4lbs, the answer is yes. A 7mm suit might swing up to 10
or 12 lbs depending on the suit, more than your lungs
can compensate for.
So the next thing to look at is what happens if you have
a catastrophic wing failure at depth. In any wetsuit, you
would ditch weight equal to the weigh of the gas in your
tanks, then you are neutral minus the compression of the
wetsuit, which is why a 3mm suit is okay, because you
can offset the few lbs of the 3mm suit with your lungs. At
that point you can swim up using your lungs for buoy-
ancy.
As an exercise, I would try to test the buoyancy swing of
your 5mm suit at depth, maybe 60 feet, and see what it
is. At the end of a dive, when the wing should be empty
of the weight of the gas but still carrying the weight of
the wetsuit compression, slowly empty the wing and see
if you can maintain buoyancy with your lungs, or at
least be able to slowly swim up to 30 or 20 feet, where
the suit will expand and you should be close to neutral,
able to maintain your shallow stops. When doing this
exercise, be careful not to lose control of your buoyancy,
either going up or down. Be especially careful not to
hold your breath or keep your lungs completely full on
ascent...you must maintain an open airway while going
up! Which means fill your lungs and slowly breathe out
on ascent, then refill and breathe out, etc. This will give
you an idea of what you would be facing if you had a
wing failure in your 5mm suit.
If you had a wing failure while wearing a dry suit, you
would just use the suit for buoyancy compensation, or
visa versa if the suit fails.
Finally, a side effect of a wet suit compressing is that
is loses much of its insulating properties at depth. This
is true for all suits, but especially a 5mm suit, which is
not that warm to begin with. So be prepared to get cold,
and remember that cold is cumulative, so be sure to get
warmed up as fully as possible between dives. So the two
reasons we really like dry suits: the buoyancy swing is
eliminated, and insulating properties stay the same at
depth.
Hope this helps explain it.
Jeff Seckendorf
TM