Quote:
Originally Posted by BobFromAccounts
So how does a liquid that is warmer than your external skin temperature cool you down? Evaporation, as the sweat evaporates it leeches energy and thus cools you.
OK, so now the thermals, If they are made of modern technical material they will absorb the sweat and distribute it more evenly than the globules of sweat that appear on your naked skin and enhance the whole evaporation process.
|
Yes, and then cooling is enhanced if there is enough AIR FLOW over the sweat soaked fabric contacting skin.
This was why Fenn's post puzzled me. Seems they were wearing Synthetic Winter Grade Jacket and Pants .. any bets it was BLACK? (no venting mentioned) with WINTER Thermals worn under. WRONG, perhaps dangerous?
You need some air flow to allow sweat induced cooling to happen. Right? And when you're stuck in traffic in 40C ... there IS no cooling. For this ... my riding jacket comes OFF and I'm wearing dirt bike desert racing set up only.
(Long sleeve synthetic shirt, elbow guards, back protector) Proven to work. Once moving, jacket should go back on ... Keep the Sweat inside! Keep drinking!
But TOO MUCH air flow (like with NO cover of bare skin) can lead to serious dehydration. We see this here a lot with the our more intelligent Harley guys ... riding in Tank tops and beany helmets on 40C days. They end up in the emergency room ... needing four or five IV bags of Saline.
So you need SOME air flow, but keeping sweat flowing is important also for cooling and of course in heat, constant drinking required. I learned this from Tri-Althelete friend. In 118F (47C) crossing Death Valley (which I've done dozens of times) I drink constant sips, two to three minutes apart. DO NOT run out of WATER!
Quote:
Originally Posted by BobFromAccounts
Andrew Fenn's theory holds water, get it a little pun there , until you reach the leathers which do not breath
|
Leather does breath. Not a lot, but does breath. It's the "original" breathable material. Also, some leather is perforated or has venting (like mine). So helps with cooling evap in HOT temps.
In cold, if I'm sweating inside, it's not very cold outside. If cold, air flow will evap sweat quickly, then it's time to close vents, add a layer to two. Like going from Death Valley (below Sea Level) up into Sierra and 3000 meters, which happens in 30 minutes of riding in California/Nevada.
Perhaps with hikers or Skiers, this can be a problem ... and IS after all why Gore invented GoreTex! To keep guys from freezing after exerting in super cold weather ... being frozen from there own sweat. We experienced this exact thing in Antarctica ... and GoreTex DID help us when it was brand new. (two years there)
Quote:
Originally Posted by BobFromAccounts
I hope I've explained this correctly because I had a huge problem getting my head around this when I sat through the lectures.
|
Me too. My lectures came from British Antarctic Survey guys and Navy Seals. The BAS guys had us doing Crevasse rescue ... so we were actually out in it, doing it "on location". Seals was a different situation, very useful too.
Quote:
Originally Posted by BobFromAccounts
I think the proof of this theory is our friends in the road racing fraternity, they can happily race in Malaysia at temperatures in excess of 40ºC but if the race directors hold them on the start line too long they start passing out.
|
Sexy umbrella girls and perforated leathers usually help in this situation!
Actually, it's the motors they are more worried about. Overheating, especially back in old days with 2 Strokes.