Math has never been my strong skill, so work with me here. I've participated in various discussions about wetsuits and layering, and I'm concerned, as we in the mid-Atlantic get into the transition months where cold water protection is needed but drysuits might be overkill, that I don't get the math! Specifically, is it the opinion of members of the list that layering a two mil thick vest and a pair of rodeo shorts --- and let's use neoprene and not the new Malden fabrics for the sake of argument --- over a two mil longjohn yields the protection of a four mil wetsuit in the core body areas? I had always accepted the idea that it did --- but then I started thinking about the way these things work. When we swim, roll, low-brace, etc., water replaces the air between the suit and the body whenever and wherever it can inside the base layer longjohn. Physics is physics. The process continues until the air is fully replaced by the water --- let's say for a swimming kayaker --- and, unless the suit is loose or is exercised in to a significant degree, the water will not flush in and out of the suit a great deal, is warmed by the body, and a possibly degraded but relatively stable body temperature can be achieved, with the body continuing to produce heat to warm and hopefully stabilize the water inside the suit. The neoprene longjohn now acts (1) as an insulator from the outside colder water mass which would otherwise quickly suck all the heat from the body and (2) as a tight barrier, keeping a heat-stabilized water mass of a minimum size against the skin. But what about that second two mil vest and shorts over the longjohn. The ambient temperature (cold) water replaces the air between the neoprene layers but, unlike the layer next to the skin, there is no direct contact with the body to warm this water layer. If the baseline longjohn is thermally efficient, body heat should not be transferred through the neoprene's insulating layer; obviously, the insulating powers of two mil neoprene are limited, so some amount of heat will escape, potentially be captured by the water between the two layers of neoprene, and, in turn, be insulated from the outside water mass by the second layer of neoprene. But does this second layer have anything close to the same insulating capability as the first? Seems to me it's very unlikely that there could be any measurable increase in thermal efficiency from the vest and shorts over the thermal efficiency provided by the longjohn. Having always accepted that there <was> a value in layering neoprene, I'm now concerned that the idea was bogus all along. So, does two plus two really equal four? Or does it equal two point one five? Or three? I'm pretty sure it's not anywhere close to four! This isn't an idle question --- it's getting colder on the Chesapeake. I've been working with a premise that I now think is flawed. This isn't an idle how-many- angels-can-stand-on-a-pinhead question --- nor is it designed to fill the current information vacuum on PaddleWise. Any thermal engineers out there? Divers? Jack Martin *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
>But what about that second two mil vest and shorts over the longjohn. ...etc. You seem to be assuming so much effectiveness for the first layer of insulation that the second layer has nothing to insulate -- sort of like the situation you would have if you wrapped a blanket around a very well-made thermos bottle. We don't do the latter because the gain in heat retention would be negligible (relatively little heat leaks from the bottle) and the coffee wouldn't be noticeably hotter or stay that way much longer than without the blanket. The same logic could be used to "prove" that layering winter clothing isn't helpful. Part of the value of layering (in general) is that it offers the option of tailoring your level of insulation to the conditions (by adding or removing layers), thus avoiding overheating. That's probably not a consideration when immersed in cold water. A human body wrapped in any kind of clothing probably does NOT approximate a thermos bottle. There will be significant heat loss through a first thin layer of neoprene, else why would thicker neoprene insulate better? Whether 'tis better to make it thicker buy buying it thicker in the first place or by adding a second thin layer would seem to be an empirical question, i.e., begging for someone to go out and measure the difference with a thermometer. Hope that early morning rambling adds to the discussion... Ira Adams ************************************************************ I don't do .INI, .BAT, .CFG, or .SYS files. I don't assign apps to files. I don't configure peripherals or networks before using them. I don't manage IRQs and DMA channels, either. My computer works for me, not the other way around. I have a Macintosh. *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
Having a few thousand hours in the water (lots of it cold, some deep), I will present my ideas. There are three major factors to the warmth of wetsuits. 1. Coverage. Do you cover all skin or leave some exposed? Do you wear a hood? The head is your fastest place to loose heat, next are the groin and armpits. 2. Thickness. How thick is the wetsuit? It the suit the same thickness everywhere, or thicker in the most important areas. Thicker is warmer. 3. Water exchange. Does the water seep into the suit and not swish in and out, or is the suit loose and floppy so that water runs in and out all of the time? Less water exchange is warmer. This can often be te dominant factor. A poorly fitting suit that lets the water move a lot will usually be coolder than a thinner suit that fits and keeps the same water inside. My final thoughts. 1. The wetsuit must fit snuggly, like a second skin, but not so tight that it cuts off blood flow. 2. Additional layers that also fit snugly are very nearly as good as a single piece unit that is the new thickness. 3. If the added layers reduce the exchange of water, they will often be warmer than the simple added thickness. Examples of this are gloves, booties and hooded vests that do a lot to keep the inside water 'inside'. You are right. It is not a simple question. How your movement interacts with the suit also has a major influence on the exchange of water and thereby the warmth of your suit. It is a good idea to test a suit both for just waiting for help and also doing the kind of things you might be doing to recover. When you tuck under to reenter and roll, does the suit blast you with cold water? Can you do the movements at all? As suits get thick this can be a factor. Just when you thought something was simple...... :-))) michael JCMARTIN43_at_aol.com wrote: > When we swim, roll, low-brace, etc., water replaces the air between the suit > and the body whenever and wherever it can inside the base layer longjohn. > Physics is physics. The process continues until the air is fully replaced by > the water --- > So, does two plus two really equal four? Or does it equal two point one five? > Or three? I'm pretty sure it's not anywhere close to four! This isn't an > idle question --- it's getting colder on the Chesapeake. I've been working > with a premise that I now think is flawed. This isn't an idle how-many- > angels-can-stand-on-a-pinhead question --- nor is it designed to fill the > current information vacuum on PaddleWise. Any thermal engineers out there? > Divers? *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
On Thu, 29 Oct 1998, Michael Neverdosky wrote: > There are three major factors to the warmth of wetsuits. > > 1. Coverage. > 2. Thickness. > 3. Water exchange. >From my windsurfing experiences I would like to add the external material on the wetsuit. A skin coated wetsuit, is a lot warmer than a fabric coated wetsuit after you get wet and are exposed to the air. The skin coating of rubber basically waterproofs the exterior of the wetsuit so you stay warmer after you get out of the water but are still wet. The skin coating drastically cuts down on the evaporative cooling. kirk *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
JCMARTIN43_at_aol.com wrote: > >[snip] is it the opinion of members of the list that layering a two mil > thick vest and a pair of rodeo shorts --- and let's use neoprene and not the > new Malden fabrics for the sake of argument --- over a two mil longjohn yields > the protection of a four mil wetsuit in the core body areas? [snip] Others have already administered all the caveats, Joq. The bottom line is that thicker is always warmer. And, yes, 2 + 2 is pretty close to 4 in the warmth category. It may help to remember that the outer 2 mil layer keeps the outside of the inner 2 mil layer warmer, so the inner layer of the inner 2 mil layer will be warmer yet. [This logic is transparent only for those who are "innies" in the navel department, or those who have read a lot of Dr Seuss!] The other bottom line is that the "layer of warm water" in wetsuits is like Santa Claus and the tooth fairy. You have to really work at it to prevent water from circulating in/out of a wetsuit, *without cutting off your OWN circulation.* Add in the usual "variation" in body part size most of us experience from season to season, and that layer of water becomes a lake at times, unless you have a wetsuit for the "fat" season and different wetsuit for the "skinny" season. -- Dave Kruger Astoria, OR (most usually helping my wetsuit by maintaining at the "fat" season profile) *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
In a message dated 10/29/98 8:51:16 AM Pacific Standard Time, dkruger_at_pacifier.com writes: << The other bottom line is that the "layer of warm water" in wetsuits is like Santa Claus and the tooth fairy. >> Uh, Dave, I beg to differ on this one. As I recall from my diving days, I would hit the water first thing in the morning after several cups of coffee and soon find that that layer of warm water was most definitely there :-) Scott So.Cal. *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
I use 2 inch webbing and quick release buckles, all available at West marine. A perminent loop for the bow is attached to beam and the stern is held up by a larger loop that lifts the boat as it's tightened. cya *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
In a message dated 98-10-30 08:58:50 EST, gulfstream_at_flinet.com writes: << .....and the stern is held up by a larger loop that lifts the boat as it's tightened. >> Given the subject of the thread, doesn't that hurt just a little, Bob? Jack *************************************************************************** PaddleWise Paddling Mailing List Submissions: paddlewise_at_lists.intelenet.net Subscriptions: paddlewise-request_at_lists.intelenet.net Website: http://www.gasp-seakayak.net/paddlewise/ ***************************************************************************
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