Breathable Drysuits
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I've been pretty curious about how a breathable laminate suit works. A traditional tri laminate has the outer protective layer (cordura, kevlar, nylon). Then the middle layer is butyl rubber, which provides the waterproofing and the side benefit of being self-sealing with small holes. Then the inner layer so that your not rubbing against the butyl rubber. So obviously rubber is not gas permeable.
So in a breathable suit I'm assuming that the waterproof layer is not butyl rubber? Then what is it? And does it still have the self sealing capabilities as butyl rubber? And to my experience over the years with a variety of gas permeable materials like gore-tex, they have all leaked over time.
That said if a breathable suit makes a noticable difference I would be interested. I sweat like a pig on the surface in my current tri-lam.
So in a breathable suit I'm assuming that the waterproof layer is not butyl rubber? Then what is it? And does it still have the self sealing capabilities as butyl rubber? And to my experience over the years with a variety of gas permeable materials like gore-tex, they have all leaked over time.
That said if a breathable suit makes a noticable difference I would be interested. I sweat like a pig on the surface in my current tri-lam.
I have been in contact with Rofas regarding their breathable drysuit (RS 350) and how lasting the material is.
The answer was:
"The breathable material of RS350 TR is a wonderful material, very light, but it is not so lasting. At first, the problem is only of “look”, the inner coat begins to detach from the other coats and the suit looks ruined, and then it begins leakage. We consider its life not more than 400 hours of dives. So 40/50 recreational dives per year guarantee almost 10 years life, but if you have technical dives (3/4 hours per dive, 100 dives per year…) it will probably wear out after one year only."
That was one reason that i decided not to take this suit.
The answer was:
"The breathable material of RS350 TR is a wonderful material, very light, but it is not so lasting. At first, the problem is only of “look”, the inner coat begins to detach from the other coats and the suit looks ruined, and then it begins leakage. We consider its life not more than 400 hours of dives. So 40/50 recreational dives per year guarantee almost 10 years life, but if you have technical dives (3/4 hours per dive, 100 dives per year…) it will probably wear out after one year only."
That was one reason that i decided not to take this suit.
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@Uhweh got a correct report from Rofos directly.
The waterproofing layer is basically GoreTex so if you want to know how it works, read up on GoreTex because it's the same thing. May or may not be made by WL Gore, but a lot of it is. They are semi-permeable membranes and are very fragile. Heat, UV, abrasion, etc will all cause them to rapidly degrade. Rofos seems to be one of the few manufacturers that freely admits to the limited lifespan of the material as opposed to the others that make no mention of it. I'll take butyl rubber and just take the top half of the suit off...
The waterproofing layer is basically GoreTex so if you want to know how it works, read up on GoreTex because it's the same thing. May or may not be made by WL Gore, but a lot of it is. They are semi-permeable membranes and are very fragile. Heat, UV, abrasion, etc will all cause them to rapidly degrade. Rofos seems to be one of the few manufacturers that freely admits to the limited lifespan of the material as opposed to the others that make no mention of it. I'll take butyl rubber and just take the top half of the suit off...
Jack Hammer
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I used the Rofos and found it more comfortable when gearing up. I decided to go a different direction because I dive a lot and my dives tend to be 2-3 hours so delamination is a concern. Same with the Argonaut.
I'm not trying to argue with you. I know you do this stuff for a living, so this is a genuine question.
I have a 1 piece motorcycle suit. Cordura and Gore-tex. I've had it for over 10 years. I have spent MANY hours in it, riding and walking around in it off the bike. It shows no signs of delamination or leaking. The manufacturer says that it may start to let water in if it gets dirty enough. Something about the micro-pores getting clogged and wicking water, I guess? In which case, the solution is to wash it with Nikwax or similar and then re-treat it with a DWR. But, they don't say anything about the inside ever starting to delaminate - and mine shows no signs of it.
Why is my motorcycle suit so different (in terms of Gore-tex longevity) than a drysuit? Is it just that this stuff lasts longer than (for example) Rofos might suggest? I.e. Rofos is trying to set a worst-case expectation? So, my m/c suit will eventually start to delaminate. And a breathable drysuit will do the same. But, maybe 400 hours of diving is somewhere towards the worst-case end of the spectrum, so you could reasonably hope to get more than that - especially if you take good care of it?
Regardless, a 10 year life expectancy seems like a long time, to me. That would not sway me away from buying one. That one year estimate for tech divers... well 100 dives per year that are all 3 - 4 hours? Yeah, I suppose if I were doing that, I might want a more durable suit. But, as long as I'm diving OC, 3 - 4 hour dives are a pipe dream and, really, 100 dives per year - of any length - is something I fantasize about. If I could get 75 hours of dive time, per year, I would be ecstatic. Even then, it would almost certainly be a mix of wet and dry. A drysuit that needed to be replaced every 6 to 8 years still isn't something that would sway me away from buying it. If I were diving a lot - and dry all the time - I would still figure I'd probably want to replace my drysuit at least every 5 years anyway. I am sure there are people diving drysuits where their primary suit is over 5 years old. But, how many people dive dry a LOT and have a drysuit over 5 years old as their main drysuit?
KevinNM
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Motorcycle suits are not pressurized with air on one side and surrounded by water on the other.
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@KevinNM and @stuartv
So the real issue here is the forces on either side of the fabrics and what they have to do to stop flow. On outdoor clothing, very few of them are really waterproof. They have coatings on the outside of the fabric that prevent the fibers from absorbing water which causes the water to bead up and get shed, but they will almost always absorb some water. I.e. your motorcycle vest can probably be out in the rain with you just wearing it for an hour, come in and snap it out and it's mostly dry on the outside. Go for a ride at 80mph in the rain, and the force from the speed will cause the water to get into the jacket. The Goretex then has the job of trying to prevent that water from going past the membrane and it's a fairly easy job to do.
You have two different forces in membranes, one is the vapor pressure differential, the other is the air pressure differential. The vapor pressure is the one that matters because you get humid inside of a suit and it wants to get out to equalize the vapor pressure with the air. The membranes in drysuits have smaller holes because they also have to withstand the pressure differential of the air trying to escape out of the suit when you're in the water.
Same type of membranes, however the drysuit membranes are going to be much more sensitive to any type of movement due to porosity and if those pores open, they will start to leak. Your motorcycle vest will experience the same type of degradation, but because it doesn't have to create a seal, it doesn't really matter. Combine that with the amount of material in terms of layers, the air barriers between those layers, and the WR nature of the external fabrics, if a drop or two gets in, you aren't likely to notice.
The biggest thing for me is how much am I getting vs. how much I have to sacrifice. For the breathable suits, I get a suit that will release some vapor when at the surface which may lead to a slight increase in comfort, but I have to pay for it with dollars, and then the total cost of ownership goes up because the suit won't last as long. For me? I'd rather just crack the zipper
So the real issue here is the forces on either side of the fabrics and what they have to do to stop flow. On outdoor clothing, very few of them are really waterproof. They have coatings on the outside of the fabric that prevent the fibers from absorbing water which causes the water to bead up and get shed, but they will almost always absorb some water. I.e. your motorcycle vest can probably be out in the rain with you just wearing it for an hour, come in and snap it out and it's mostly dry on the outside. Go for a ride at 80mph in the rain, and the force from the speed will cause the water to get into the jacket. The Goretex then has the job of trying to prevent that water from going past the membrane and it's a fairly easy job to do.
You have two different forces in membranes, one is the vapor pressure differential, the other is the air pressure differential. The vapor pressure is the one that matters because you get humid inside of a suit and it wants to get out to equalize the vapor pressure with the air. The membranes in drysuits have smaller holes because they also have to withstand the pressure differential of the air trying to escape out of the suit when you're in the water.
Same type of membranes, however the drysuit membranes are going to be much more sensitive to any type of movement due to porosity and if those pores open, they will start to leak. Your motorcycle vest will experience the same type of degradation, but because it doesn't have to create a seal, it doesn't really matter. Combine that with the amount of material in terms of layers, the air barriers between those layers, and the WR nature of the external fabrics, if a drop or two gets in, you aren't likely to notice.
The biggest thing for me is how much am I getting vs. how much I have to sacrifice. For the breathable suits, I get a suit that will release some vapor when at the surface which may lead to a slight increase in comfort, but I have to pay for it with dollars, and then the total cost of ownership goes up because the suit won't last as long. For me? I'd rather just crack the zipper
I think the smaller holes thing is probably the explanation I was looking for.
But I don't understand about the pressure differential. Pressure inside the suit is the same as outside, the suit, right? in fact, it seems like that would be a case more in favor of the m/c suit leaking because an 80 MPH raindrop has a big pressure differential when it hits the suit, compared to the suit's inside pressure. But, a drysuit should have the same pressure inside and out, right?
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