paddler3d:
Has anyone out there had any in water experience using [GOOGLE]sodium-acetate[/GOOGLE] heat pads?
How did you use them? Where did you use them? How long did they last in the water? What size pad did you use? Would you or would you not recomend them?
Imperically I get it and they make sense. I'm just wondering if in a wet environment if they would last long enough to make a difference or just ask complication to the dive.
I'm toying with the idea of getting a couple of the 8x8 pads, making some sort of neoprene belt for them that would hold them on the kidneys. They would be used in a semi-dry wetsuit in waters down to 40degrees farenheight.
Cheers,
Chris
Sodium Acetate pads totally rock in a drysuit. On a whim a few months ago I bought a pair of them to experiement with an here's what I've discovered.
1) You can put them on under a drysuit. To do this you'll need something to position them properly. In my case I had an old shirt laying around with two breast pockets that were perfectly positioned to keep the pads high up on my chest. This, I think, is the ideal position for them. The main issue is core temperature. Don't waste your time putting them in your dry-gloves or whatever. In fact, I'd say if your hands are getting cold that dealing with your core temperature will probably help that more than hand warmers will....
2) They get *MUCH* hotter than you think they will when you play with them in your living-room. The sodium acetate gets to about 55C (130+F) so if you put them right against your skin then you're going to get burned. Don't be stupid, make sure that you put them on *LAST* over top of *ALL* of your undergarments. Believe me if you don't you'll regret it.
3) Suit squeeze is an issue. Not so much because of any danger of the pads being damaged but suit squeeze pushes the pads forcefully against your body. This makes them seem hotter than they are. Once again, the warning is that they can easily be *too* hot if you put them too close to your skin.
4) The burning sensation can be suppressed by a number of factors including friction of your undergarment on your skin, the feeling the suit sqeeze and the acclimation of your skin to the heat..... so if you're not in touch with your body then you probably don't want to try this.
The pads I bought have a 45 min "burn" time. For the dives I make in the winter (usually just short of an hour) they're ok. If you make longer dives, there are pads out there that I know of with 90 minute burn times. The pads I have are just a shade bigger than the palm of your hand. I use them 2 at a time.
To give you an idea of how they work, I'll describe tonight's dive:
My buddy and I decided to go to the local lake to just get wet. The idea was to puddlestomp around at a maximum of 90ft. We didn't agree on a maximum dive time.
Just before zipping up my drysuit I activated the pads. We zipped up and grabbed our stuff and the elapsed time between activating the pad and descending for the dive was about 10 minutes. Water temperatures in January are usually about 2-3C but today we had 6-7C, positively tropical for this time of year. Usually you ahve to wait until April for these kinds of temperatures but that's what global warming buys us I guess....
Our dive took us to 83ft. The pads are liquid filled without any air spaces so there isn't any chance, the way I see it, of them rupturing. In a few weeks I'll be taking them down to 60-odd metres so I'll get back to you about that assumption... If they survive 68 metres I'll be declaring them the invention of the century.
In terms of warmth generation, the pads were much warmer in my drysuit than I expected them to be. At 5 metres under water I wondered if they were warming up more than they should be--I was concerned about how the sodium-acetate would react under high pressure--but at 10 metres I decided that it had more to do with suit squeeze than with acceleration of the chemical processes.....At 25 metres my theory was, in my mind, proven. They don't get hotter but they do get crushed up close to your body because of the suit sqeeze, which makes them seem hotter than they are.
In my case, after about 35 minutes I could feel them starting to cool off. Up until that point they seemed to be generating more heat that I was losing. In any case, I was feeling warm at 35 minutes, which I had never had on a winter dive before....
At 45 minutes they were definitely burned out and I could feel the cooling process starting. In comparison, normally the cooling process starts as soon as your big-toe hits the water. By using the pads I was able to delay the *onset* of the cooling process by about 1/2 hour. At 46 minutes my buddy was fighting the cold and I was still feeling good.... That's the difference. Instead of wanting to stop after 45 minutes, I was feeling like we had just gotten started. I could have dove another 30 minutes without fighting the cold.... In contrast, a year ago, without the pads i would have been shivering at 40 minutes.....
At 50 min we surfaced. I was still feeling like I used to feel at the start of a dive and my buddy was saying "Muhmuhmuhmyyy hh-hh-hhhands hu-hu-hurrt"
Conclusion:
1) They are fit for purpose
2) There is a risk of burns that you can not ignore. Begin small and build up. Wear them as far away from bare skin as you can
3) it doesn't eliminate hypothermia, it just delays the onset
4) They don't need to burn for the whole dive to keep you comfortable for the whole dive....
5) They are a huge improvement over "do nothing".
R..
