Thermal Protection, over estimate the need?

[JohnnyC]

Active heating is really the best way. What you're really trying to avoid is on-gassing when you're warm, and off-gassing when you're cold. In recreational diving it's not a huge deal, but repetitive days of diving to your NDL's could cause an issue, albeit hopefully minor.

What you want to do if you don't have the ability to actively heat your suit end your dive warm, is relax on the surface for a bit, in the water, prior to starting your dive so that your temperature stabilizes before you start dumping inert gas into your tissues. Again, single or a couple recreational dives, probably not a problem, but people still get bent when they shouldn't. And nothing says you can't swim around during your safety stop to warm up. Richard Pyle does that on every dive, and while I'm convinced that he's only alive because he's the luckiest SOB on the planet, I'd rather be lucky than smart any day, warming yourself up does have merit.

 

[Schwob]

Good to know... thanks...

...When diving with hoods, you MUST flush the hood on the beginning of your descent. If it is a high quality hood and fits well, it will seal your external ear canal and when you equalize you can blow your ear drum out. ...

 

[Beau640]

Echoing the above, it is ideal to be cold in the bottom so vasoconstriction lessens your ongassing, and warm at deco so you offgas more efficiently. The active heating is one way to do it. In the Great Lakes up here in cold country it happens naturally. Year round our bottom temps are 40 degrees. In the summer though your deco stop will be 70 degrees because of all the thermoclines.

The other way to do it is with LIGHT exertion during the deco stop. Heavy exertion is very bad but gentle finning in a circle rather than staying completely still can help. This is a little controversial but multiple sources I’ve read recommend very gentle exertion (see mark Powell deco for divers)

 

[txgoose]

I do love all of the extra information. And if it is presented for others reading along, more. But just to clarify, we had an avg depth of 22 ffw with a max of 41 ffw (for less than a minute). The second dive had no safety stop as my youngest and I slowly worked our way up the slope to the shore. No deco or even remotely pushing NDL.

 

[JohnnyC]

I do love all of the extra information. And if it is presented for others reading along, more. But just to clarify, we had an avg depth of 22 ffw with a max of 41 ffw (for less than a minute). The second dive had no safety stop as my youngest and I slowly worked our way up the slope to the shore. No deco or even remotely pushing NDL.

Sure, but that doesn't change the physiology. You want to start the dive cold, and end it warm. If that means you sit on the surface for a bit before you start your dive, then do a little light exercise at the end, that's what you do within the framework of the capabilities you have at your disposal.

Your original post has already been covered pretty well. Get a good hood. Use it. Make sure you're using it correctly. Enjoy your diving!

 

[sea_otter]

I can sympathize with not wanting to put on a lot of clothes when it is 90 degrees on land, but you are absolutely right! I made a similar mistake a couple summers ago. Did a dive in Lake Tahoe on a hot summer day. Surface water temperature was about 78F (air above 90F), but I was told to expect it to be 48 degrees at 100 ft. I dressed for 48 degree water temperature, in warm fleece and a drysuit and a 10 mm hood. The lowest temperature we reached was 57F, and due to the altitude, we spent less than 20 minutes at depth. Most of the dive was spent in shallower water where it was toasty warm.

I decided that sucked, our second dive was intended to be a shallow one to collect crawdads for dinner, so I took off my heavy undergarments and hood, and I changed into a wool shirt and a pair of yoga pants. No hood. Well, we got underwater, and we realized that the crawdads were not at 30 ft as we planned, but they were down over a short drop off around 50 ft. That was below the first thermocline. We spent most of an hour chasing them. The water temperature was 61F. I wasn't wearing any insulation. God... I froze. Really should have called the dive or insisted we stay shallower as we planned, but I didn't. When I surfaced my lips were blue. Buddies still give me (well earned) **** about it.

 

[Tom_Ivan]

Active heating is really the best way. What you're really trying to avoid is on-gassing when you're warm, and off-gassing when you're cold. In recreational diving it's not a huge deal, but repetitive days of diving to your NDL's could cause an issue, albeit hopefully minor.

What you want to do if you don't have the ability to actively heat your suit end your dive warm, is relax on the surface for a bit, in the water, prior to starting your dive so that your temperature stabilizes before you start dumping inert gas into your tissues. Again, single or a couple recreational dives, probably not a problem, but people still get bent when they shouldn't. And nothing says you can't swim around during your safety stop to warm up. Richard Pyle does that on every dive, and while I'm convinced that he's only alive because he's the luckiest SOB on the planet, I'd rather be lucky than smart any day, warming yourself up does have merit.

I showed that to the missus and she replied that her active heating was saving the pee until the safety stop

 

[Marie13]

Something that can also help are neoprene socks. My feet get cold before any other body part. The neoprene socks do the trick.