Problem with Fusion drysuit: poor venting

[JanK]

Hi all, I need some advice on the Fusion drysuit.

Some background: I passed the CMAS P1 three years ago PADI AOWD two years ago.
I have 70 dives, of which 40 were done last year. I feel very comfortable in the water. Most of my diving is done in the Adriatic, where the
temperatures on the surface in summer reach around 25°C, but below 20
metres they drop to around 15°C and the coldest I have been in was 8°C.

Usually after the first 15 minutes I would get goosebumps (I presume, I
didn't peel back the suit to check ) and after another 15 minutes I
would start looking for warmer water, sometimes floating above the group so
as to be above the thermocline. At first I tried a custom made 6.5mm two
piece wetsuit with hood and no zippers (an interesting exercise in
flexibility putting it on ). This only delayed the onset of symptoms for
maybe 5 minutes.

So in September last year I asked my oldest friend, who's also been an
active instructor for the last 10 years, to give me a drysuit course. In
the two dives required for the course I dived both neoprene and trilaminate
drysuits. I had absolutely no problems with buoyancy, venting of air
(except for a detail that will be explained later), recovering from a feet
up position even at shallow depths,... in fact they were two of the most
comfortable dives I've ever made. I loved the fact that the trim was
depth-independent (with the heavy neoprene wetsuit the center of lift
shifts forward at depth, so my feet are higher in shallow water than in
deep water). His verdict was that I was a natural and that I should have no
problems handling any suit.

So, this year I purchased a Fusion (Scubapro, licensed from Whites) drysuit
and a Seemann Subtech Pro 490 undersuit
Diving Planet

I decided that I would try out the suit during the current vacation in
Egypt, since the conditions here are almost ideal. It's a bay with a sandy
bottom with coral reefs on either side. At the point where you jump in from
the jetty there's a large sandy plateau at about 3-4m depth, which then
gently drops off towards the open sea. On the plateau there are several
weight boxes and quite a few ropes anchored into the bottom. And the water
is warm, so no problem if I flooded the suit. Well, the last concern turned
out to be the least of problems...

I usually dive with 10kg of lead, during the drysuit course I had IIRC
12kg. For this dive I wanted to be on the safe side, so I took 14kg of
lead. It turned out not to be enough - I had to pull myself down to a
weight box and add another 2 kg to stay down (in retrospect I should have
taken more to account for the breathed gas on the way back). I then checked
that the vent valve was fully open, that bubbles came out when I pressed
it, did a few somersaults and rolls to check stability and mobility and,
when I was satisfied that everything was OK, my buddy and I started
descending.

At about 6 metres I added some air to suit to counteract squeeze. The
second time was at around 10 metres and that's when the "fun" began. I held
the suit inflation button for a bit too long, but I thought: no problem, it
will vent. Not!!!!

From that point on the dive was reduced to trying to keep myself from
rocketing up: venting all air from BCD, grabbing the only rock around (damn
sandy bottom! ), twisting and shaking to try and move air around and get
it to the shoulder area, swimming downwards,... Luckily my buddy had the
presence of mind to empty his BCD, jump on top of me, grab my tank, and
help me stay down until we reached the first anchored rope, because I am
not sure I could have made it on my own without breaching.

Needless to say I was quite exhausted when I finally reached the surface -
safely thanks to my buddy and the ropes. As an aside: my SAC on dives up to
now was between 16 l/min and 24 l/min with median at 18 l/min, for this
whole dive it was 42 l/min and I suspect that, since the first third of the
dive went well, my actual SAC under high workload is around 50 l/min - a
very sobering thought and a figure I need to remember when planning dives.
On the other hand I now know that my regulators can easily provide these
sorts of flows without getting harder to breathe.

I tried to analyse the problem, but I haven't come to any conclusions and
that's where some help from the people on this board would be appreciated.

The vent valve looks OK as far as my untrained eye sees. It did vent air,
but then I remembered that the vent valves on the two drysuits I used
during the course performed very differently. The first suit had a very
sensitive valve, and it burped on the slightest ascent. The second had a
lazy valve that relased air relatively slowly. We looked at both of them
and saw that the lazy one had an anti-lint filter behind the openings
facing the interior of the suit. We speculated that that might be a
reason, but we didn't investigate further. The SI Tech vent valve on my
suit has that filter.

The other difference from the training dives is the undersuit - during the
course I used a relatively thin, soft and compresible undersuit, while my
current one is relatively thick and poorly compressible - the bulk of the
insultation is provided by fleece.

I started wondering if there was a problem with compatibility between the
undersuit and the drysuit. When I put on the drysuit, the material on legs
and arms is nicely compressed, but along the torso I get a big bundle of
relatively thick fabric that gets folded onto itself. Perhaps this is where
the pockets of air accumulate?

I do like to keep my BCD tighly strapped to me, including a crotch strap,
as I hate it when the tank flops around, and the tightness of the straps
could possibly cut off the flow of air. But then I had the exactly same
setup during the course and had no problems.

Well, while writing this post I realised a simple way to check the
compatibility: try the drysuit without the undersuit.

But in any case, any information/hints would be much appreciated.

Cheers,
Jan

 

[Bubbletrubble]

There's probably nothing wrong with your gear.

You need to do a proper weight check in your drysuit (while wearing the undergarment) with all of your other gear. An important element of this weight check is making sure that you have a comfortable amount of air in your drysuit. A proper weight check takes into account the amount of remaining gas in your tank and the influence this will have on your buoyancy at the end of the dive. If you weighted yourself in the method you describe, it's no wonder that you were 3-4 kg light at the end of the dive. That occurred due to the change in tank buoyancy from full to empty, you know.

If you change the drysuit in your gear configuration, do another weight check.
If you change the undergarment in your gear configuration, do another weight check.
If you change the tank (which has different buoyancy characteristics than the one you normally use), do another weight check.
If you change anything that affects your buoyancy at all, do another weight check.

It's probably not very helpful to extrapolate your weighting needs from one drysuit to another. The drysuit shell composition and the thickness/composition of the undergarment can make a HUGE difference in how much ballast is needed.

One of the most important things that can be taught in a drysuit class is how to be properly weighted. You probably didn't have enough ballast. Simple as that.

In order to properly vent, the drysuit exhaust needs to be placed at the highest point of the suit. An easy way to get air out of the drysuit legs is to orient yourself vertically. You should be able to feel a squeeze in the lower legs/lower part of the drysuit when you do this. This will force air up and out the exhaust valve located on your upper arm. With the Fusion (and many other drysuits), all a diver in good horizontal trim usually has to do is dip the right shoulder down a little to vent air from the left upper arm exhaust valve. You shouldn't have to contort your body into an awkward position to vent. I have only done a demo dive in a Fusion, but I found it very easy to vent from the exhaust valve. My gf has put well over 100+ dives on her Fusion and she has always found it easy to vent the suit.

Bear in mind that I'm assuming that you have a properly functioning exhaust valve.

All of this should have been covered in your drysuit course.

 

[Diver0001]

What kind of an undergarment were you wearing when this happened? Was it one made for use in a drysuit or were you improvising something?

Also, are you sure the outlet valve was open? I'm sure you know that you can open and close them by screwing them open/shut.... Are you sure about the position of the valve during this dive?

Ordinarily when things like this happen one of three things has happened.

- the undergarment is sealing around the valve and the air can't escape
- the diver closed the valve but thought it was open
- sometimes the suit has a neoprene flap that is supposed to be under the zipper to protect it from jamming in the undergarment, but the flap got folded the other way and is causing a seal by the outlet valve.

Incorrect position can be a problem too but it sounds like you tried every position you could think of...

R..

 

[Bubbletrubble]

What kind of an undergarment were you wearing when this happened? Was it one made for use in a drysuit or were you improvising something?

The OP inserted a link of the undergarment that was being used.

Ordinarily when things like this happen one of three things has happened.

- the undergarment is sealing around the valve and the air can't escape
- the diver closed the valve but thought it was open
- sometimes the suit has a neoprene flap that is supposed to be under the zipper to protect it from jamming in the undergarment, but the flap got folded the other way and is causing a seal by the outlet valve.

Given the design of the drysuit undergarment being used, I don't think #1 is an issue.
#2 is possible, but the OP does recognize the difference in setting an exhaust valve to be open or closed. I would think that the OP tried to vent by pressing down on the exhaust valve as well. As you know, Si-tech exhaust valves are designed to vent when pressed down regardless of the automatic setting (open/closed).
The Fusion doesn't have a wide flap that goes under the zipper, so #3 is impossible.

I hope that the OP will update us on his progress with this issue.

 

[TSandM]

It's been my experience with several suits with SiTech valves that they vent quite easily.

I use a Fusion, and I have a lot of extra fabric bunched up around my waist. I also use a 20 lb weight belt, and strap it on quite tightly. I have not had any problems with inability to move air from the lower half of my body to the upper half to vent it, so I don't think that's the problem.

You can check the function of the valve by putting something in the wrist and neck seals to block them, and inflate the suit with the valve closed. Open the valve, and air should rush out.

Blockage of the exhaust valve, to my knowledge, is limited to certain undergarments with a slick, nylon outer covering that can get sucked up into the valve. I don't believe this happens with fleece.

If I had to guess, I'd guess you were underweighted to a significant degree, and when you put a little air in the suit, you were extremely light, but the suit still wasn't inflated to the degree that gas would be easy to move to the valve and vent. I actually tend to dive about 2 lbs overweighted, just so that even with an empty tank, it doesn't require gyrations to get the last few molecules of gas out of the suit to remain neutral in the shallows.

Do a formal weight check and see what you come up with, and let us know.

 

[ERP]

I then checked
that the vent valve was fully open, that bubbles came out when I pressed
it.

I noticed this in your account, if the valve was open it should vent without having to press it.
You only have to press it if it's closed.

 

[HenrikBP]

I've been having a bit of "fun" venting my Fusion and have think I've found a couple of reasons:

- I have the Fusion Tech LE skin, which supposedly takes a bit more to stretch, and therefore keeps me a bit tighter "shrink wrapped" than the lycra skins. That has made it a bit tricky to run as much air in the suit as I need to easily vent.

- I found that if I run the suit very tight with very little air, it takes a significant amount of time for air to vent from feet/legs to the valve. My undergarment is a 4th Element Arctic - a quite dense double layer fleece.

- so in order to make it easier for myself to dive the suit, I have to add a few more lbs of lead, so I can run the suit with a bit more air in it => making it easier to vent. It really should just take a slight lift of your left shoulder to make it vent.

- as everyone else, I think you need more weight. I follow Tobin's advice and do a "suit weight check": I got into my suit with undies and get in shallow water with a bunch of weight and see how much it takes to sink me holding a normal breath. That gives you a base-line for weighting with that suit/undies combination. For me it takes ~24 lbs to sink me.

Then you add and subtract the rest of your gear and should be close. For instance in approximate numbers:

Backplate (SS): -6 lbs
2 regs (doubles): - 4 lbs
AL80 tanks: +8 lbs at the end of the dive
Manifold + tank bands: - 2 lbs
V-weight: -11 lbs
Tail weight: -5 lbs
etc. etc.

Henrik

 

[JanK]

First of all thanks for all the responses! I wanted to try with more weights before reporting back on (hopefully) progress, but in the last few days we've had relatively high currents, waves and lower visibility - not conditions for experimenting, given the previous experience. Perhaps I'm overcautious, but if I've learnt anything on this board, it is to keep the number of unknowns in the equation ALARA.

@Bubbletrouble: problems started 5 minutes into the dive when I've consumed only 10bar from 15l bottle at 200bar, so the decreased weight could not have prompted problems.

I am certain that exhaust valve was fully open. And even if it weren't, the first two things I did when the problems started was to recheck if it is completely open and then try to manually vent air.

Thanks again to all, and I will certainly come back with a report as soon as I actually have something to report.

 

[Bubbletrubble]

@Bubbletrouble: problems started 5 minutes into the dive when I've consumed only 10bar from 15l bottle at 200bar, so the decreased weight could not have prompted problems.

Well, if you weighted yourself with just enough lead to stay down at the beginning of the dive, it's not surprising that your issues started shortly thereafter. I'll concede that with only a tiny amount of air in the drysuit it can be more difficult to vent that little air.

The solution is pretty clear. More lead will help. Do a proper weight check at the surface with a generous amount of air in your drysuit. You can do the weight check with a full or empty tank...just compensate for buoyancy swing of the tank in your final weighting.

 

[JanK]

Here's me, with joy... The waves and the currents died off, I took the suit for another try and it worked perfectly, no balooning or rocketing up in sight

I had a bit of luck: I spoke with the chief of the diving centre, who told me that one of the next guided dives on the reef would be with a guide that dives dry back at her home country - Switzerland. I spoke to her, explained the situation, she agreed to watch out for me during the dive. I signed up and, half an hour before the dive, the other person cancelled, so effectively it was a private lesson in handling a drysuit. Before taking the suit into water I verified functioning of the exhaust valve by plugging the hand and neck seals, pumping it with air and checking that from the closed position it vented when I pressed it an vented quickly when it was open.

It turned out that HenrikBP was the closest to the reason for my problems: what threw me was my inexperience with the great differences between different drysuits. As I've explained, there were no problems with the suits used in the course. In the conversation with the guide it occurred to me that the my friend is over 20cm taller that me and wider across the shoulders and that two suits were much looser on me than the Fusion. And the undersuit was thinner. The trilaminate was the easiest to vent. The neoprene was harder, but we speculated that the antilint filter might be causing the slow venting. Now I'm thinking that it was just a bit more tight and that that was the cause of the slower venting. But in both cases the suit was oversized and as soon as there was too much air, it had no difficulty finding its way to the exhaust valve.

With the Fusion and the thick fleece undersuit, compressed not only by water pressure, but also by the neoprene, the time it takes to clear air out is significantly longer than with either of the other ones. When she saw the suit (and, BTW, she loved it and said she will certainly try one out, especially when I showed her how mobile one is inside it), she warned me that it might be slow to vent and that that is the first thing I needed to realise.

Before going into the water I did the crouch and hug to vent excess air and made sure the valve was open. I started off with 16kg and she took extra 3kg if there were a problem along the way and if I needed it at the end. The 16kg wasn't enough to sink me and keep me down, so I added another 2kg from the weight box. With that I was able to hover nicely at 4m with a smidgin of air in the BCD. So after demonstrating the recovery from feet up position, we started the actual dive to 25m. And once I'd absorbed the fact that I need to be careful in adding the air to the suit, as the rate of inflow is much higher than the rate of outflow, the dive went completely smoothly (apart from the fact that the trim was off and I was feet heavy).

I was amazed that, upon returning to the shallow water, I had no problems floating at 4m. Even better, when I released all air from the BCD, I sank to the bottom. So in spite of having lost 3kg of air (170bar from an 15l bottle) I was still negatively buoyant, apparently having vented more than 3l of air from the suit. I suspect that, once I get the hang of the suit, 16kg may be enough - to be determined and, of course, depending on how much air I will run in the suit after I get used to it. The ascent from 5m to the surface was uneventful and completely controlled.

So, the lessons learnt are:

- The problem started with the assumption that the outflow of air would be equal to the inflow of air. Based on that assumption, during the gyrations and contortions I did to release air, I simply didn't wait enough for the air to percolate around the suit.

- Never extrapolate blindly from knowledge of previous pieces of equipment, always expect problems with new equipment and try planning for them. It's an unpleasant thought that, based on previous experience, I might have skipped the test under easy conditions, have gone straight into more difficult dives and
had problems there.

- While the Internet, including this board, is an excellent resource, there is no substitute for a person-to-person lessons. I got some other tips about venting that will come useful. That is not to say that the answers here have not been informative or useful!

As for the suit itself, I like it so far. I now know where the potential problems lie and anticipate may happy dives with it.

Cheers!