Thanks again for the nice welcome from everyone!
Rick, I'm always glad to share some cold water insulation tips because I was amazed by the improvement in comfort and dexterity I experienced. Let me know what works for you, too. You probably do most of what I do, but for what it's worth....
Essentially, what I do for really cold water, such as in the 30's, is to increase the layers of insulation in my drysuit and drygloves to increase the air and loft, but being careful to avoid constriction or tight areas.
In addition, an "ice cap" underhood makes a huge difference in reducing heat loss.
Plus, the use of a homemade "fleece chest pad" turned out to be quite important. Without it, the material on the chest would be compressed, especially when I was horizontal, and I would feel the cold slowly sapping my core heat there.
My experience was similar to yours, I think, that an hour would be about my limit because of hand and foot discomfort, but more importantly, because of the significant loss of dexterity, which can be a real hazard since I mostly dive solo. I didn't like coming close to the point of not being able to manipulate my drysuit inflator, etc.
The key for me was having a drysuit large enough to accomodate more layers of insulation, then using enough lead to get slightly beyond the minimum needed with an empty tank. That extra air improves loft of the materials besides being the prime insulator.
The other factor was choosing insulation that wouldn't create tight areas which might constrict blood flow to the extremities. Polartec and polypropylene worked well, since they will bend and crush pretty easily where needed.
Specifically, here's what I do.
For temps above 40 F, I usually mix and match layers of Polartec and polypropylene outdoor wear. (Purchased from Cabela's.) (The figures below are for gm/yd weights).
Example for above 40 F:
Polypropylene and Polartec layers on both legs and torso of 100 + 300, respectively.
PLUS a fleece chest pad, created by folding the sheet of fleece twice to make 4 layers, with a final size of about 12x18". This would be approximately equivalent to 400 wt. fleece when folded. This is justfleece blanket material from WalMart or elsewhere.
Two layers of heavy socks (mine happen to be a thick wool sock and a Weezle sock). Rockboots laced as loosely as possible. I'll raise my feet at the beginning of a dive to get more air into the feet. I'll replace that air as needed, but it stays as long as I fin in my usual bent-knee position.
I've also used Polartec socks, but they weren't quite as warm because they crush and breathe too easily, I think.
SI TECH ring system with PVC drygloves, one size oversize. I wear two sets of liners, a lightweight polypropylene set under the heavier original set. I buy sizes loose enough to avoid constriction of blood flow in my fingers.
Henderson 1/8" neoprene "ice cap" hood worn under my DUI hood.
I sometimes will add a couple 1/8" neoprene neck bands that I fashioned out of 2" wide strips. They help keep the cold water off the major arteries in front of my neck.
Lead (or other weight), for me in this set up with a single HP steel 120 and attached AL30 pony, will be around 44 to 47 lbs. It's not so much that would cause massive air shifting, but enough to create a half inch layer above my kidneys and shoulders when horizontal. This is about 5 lbs more than the minimum I would need. When I've used close to the minimum, I've been noticeably colder.
Anyway, for colder water I change things a bit.
Example for water temps in the 30's:
I had the good fortune of picking up, for a song, a brand-new Weezle Extreme Plus undergarment a few years ago. It's a little warmer per volume than the Polartec. It's actually too warm above 40 F. I'd guess it's probably right up there with the 400 weight Thinsulate undergarments.
I use the Weezle because it's a little warmer than the layered Polartec, even with a third layer of 200. It's also easier to put on then all those layers of Polartec and less likely to cause constriction points in the armpits and backs of knees.
With the Weezle, the first layer is 100 wt polypropylene, then the fleece chest pad, then the Weezle Extreme Plus.
Socks are the same.
Gloves are the same, although I've found it necessary for temps in the low 30's to go with an even larger glove and use two of the heavier yellow liners. The dexterity is still better than with 1/4" neoprene mitts. I can work all of my tiny little camera housing buttons. That has actually been effective for 110 minutes in 32 F saltwater once. For dives like that, although rare, I might add a fleece pad over my kidneys somehow.
I increase my lead to about 52 lbs with the Weezle setup.
By the way, I like the SI TECH gloves because extra PVC gloves can be purchased inexpensively at places like Seattle Marine for around $20. For use under the original yellow liners, lightweight white polypropylene glove liners are cheap. I purchased a bunch at a fishermen's supply house in Gloucester for $1.12 a pair retail.
I buy sizes that aren't too tight. My goal is to avoid restricting blood flow and my hands stay very warm as a result.
Also, the SI TECH ring system is nice because it's so easy to change the outer gloves and because it's a temporary attachment to the wrist seal. It also allows the wrist seal to remain functional with the system in place.
Anyway, I've gone on too long probably. Obviously, I enjoy talking about this subject.
Let me know what you've done to tweak your thermal protection so I can borrow some of your ideas.
Kindest regards,
Dave C
