What extra weight? Are you talking about the extra weight of the comfort gas in the drysuit? That shouldn't be too many pounds. Other than that I can't think of anything, unless you're overweighted to begin with. Yes, a flooded drysuit will lose some buoyancy of the gas trapped, but it doesn't drastically change the buoyancy.
Question My Wife's Rig is No Longer Balanced. How Do I Add More Ditchable Weight?
- Thread starter Ryan Neely
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Without other gear, my suit (and me) with Arctic underlayers at minimal loft is +24 lb (measured in a pool). I've never measured what it would be if flooded, but I'm skeptical that it would not be significantly less. If it is only +10 lb when flooded that's 14 lb in addition to gas weight to swim up (assuming the wing dies).
I'd be extremely interested if you have a concrete basis for your position that suit buoyancy is largely unchanged by a flood.
Sorry, pure conjecture on my part. I think I have seen a video of someone test flooding their drysuit in a pool. Don't remember if they gauged the change in buoyancy with any precision, but as I recall it was to dispel the myth that a flooded suit gets negative, so they at least showed it was no problem to manage the buoyancy and ascend either a complete flood.
Edit:
Theoretically I think the only mechanic that would change buoyancy is the displacement of air, so I guess the question is how much air would be displaced from the undergarments...
Sooo, I was curious about that residual suit buoyancy claim and tested it. The short answer is nope, it all goes away when flooded. (At least it did for me.) This post describes it (and some additional stuff that may be of interest to the audience of this thread).
OP
Ryan Neely
Contributor
You guys are awesome!
Thanks for helping me understand this and for not allowing it to devolve into the usual ScubaVoard bickering.
I love it.
Thanks for helping me understand this and for not allowing it to devolve into the usual ScubaVoard bickering.
I love it.
tmassey
Contributor
One other thing to consider:
It’s obvious you’re worried about the additional lead you add pushing her over to an “unbalanced” configuration. What I don’t understand is: why isn’t that lead you plan on adding ditchable? I mean, if you were adding lead bolted to your back plate, or selecting unusually heavy scuba tanks (like stupid spun tanks) to add that ballast, yeah, you would have a problem. But you’re not: you’re adding it in additional lead weights.
Why not simply buy a good quality weight harness and call it a day?
www.divedui.com
40 pounds of lead. All ditchable.
I swear I’m not going to go on my usual “make sure you actually need all that lead“ rant. And as picky as you’re being about this entire process, I assume you are being equally picky on the process of figuring out exactly how much weight you/she needs. But if by chance you are not, I just want to throw that out there: so, so many divers are diving with way, way more lead than they actually need. Doing a proper weight check with empty tanks at the surface is essential. If you can just barely sink in that configuration, you have enough lead. And make sure you do it at the end of a dive where you have moved your body around extensively, up and down through the water column. That gives you a chance to get all of the air squeezed out of your suit. If you do it at the beginning, your suit will have way too much air in it and you’ll never sink. Of course, that’s why many divers think they need more lead: they can’t sink in the beginning. But that’s a problem of getting the air out of their suit, not adding more lead. (OK, I’m stopping now: I promised this wouldn’t be a rant.
)
Anyway, consider a good weight harness. It will probably solve all of your worries.
It’s obvious you’re worried about the additional lead you add pushing her over to an “unbalanced” configuration. What I don’t understand is: why isn’t that lead you plan on adding ditchable? I mean, if you were adding lead bolted to your back plate, or selecting unusually heavy scuba tanks (like stupid spun tanks) to add that ballast, yeah, you would have a problem. But you’re not: you’re adding it in additional lead weights.
Why not simply buy a good quality weight harness and call it a day?
DUI | Drysuits & Diving Equipment from Diving Unlimited International
Drysuits & Diving Equipment Diving Unlimited International | DUI - leader in drysuits for recreational, military, public safety, technical & commercial diving.
www.divedui.com
40 pounds of lead. All ditchable.
I swear I’m not going to go on my usual “make sure you actually need all that lead“ rant. And as picky as you’re being about this entire process, I assume you are being equally picky on the process of figuring out exactly how much weight you/she needs. But if by chance you are not, I just want to throw that out there: so, so many divers are diving with way, way more lead than they actually need. Doing a proper weight check with empty tanks at the surface is essential. If you can just barely sink in that configuration, you have enough lead. And make sure you do it at the end of a dive where you have moved your body around extensively, up and down through the water column. That gives you a chance to get all of the air squeezed out of your suit. If you do it at the beginning, your suit will have way too much air in it and you’ll never sink. Of course, that’s why many divers think they need more lead: they can’t sink in the beginning. But that’s a problem of getting the air out of their suit, not adding more lead. (OK, I’m stopping now: I promised this wouldn’t be a rant.
)Anyway, consider a good weight harness. It will probably solve all of your worries.
Yup. I'm aware of the mechanics. My mistake was underestimating how much air would be displaced from the undergarments when soaked. I was under the impression that if you normally dive with just enough gas to avoid squeeze, the buoyancy swing would not be substantial. This was supported by my false assumption that undergarments like wool holds air even when soaked, but I just read the warming effect of wool when wet comes not (only) from insulation but from a chemical reaction. Not sure what the deal with Thinsulate is. It stands to reason that if thick undergarments holds a lot of air to insulate, they would also lose a lot of buoyancy if all that air is displaced.
From the DUI website:
"Thinsulate insulation absorbs less than 1% of its weight in water, so it keeps you warm even in damp conditions."
I don't pretend to understand the finer point of how these materials work, but if a 500g Thinsulate undergarment can only absorb 5g of water, shouldn't it still be very buoyant? A big suit like that must displace more than 5g of water?
Key word in the quote is "damp" - Think humid or wetted, but not filled.
Flooded will be a completely different circumstances. The fibers are really small, and themselves absorb minimal water, but they are still a relatively small portion of the volume of the batt. Most of it is still interstitial space filled with the gas or liquid from its surroundings.
You are still going to lose most of the buoyancy of even a dry, marginally-inflated suit when it floods.
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