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Old 07-27-2011, 10:10 AM   #91
cliffy109
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I'm going to cut and paste another member's explanation for this. The reply was to a similar question in this thread in the equipment forum by der_saeufer. This is the first time this concept has been explained to me in a way that made sense. It is making me re-examine my views on mesh.

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You're right on the money.... here comes the science

The reason sweating works to cool the body is not simply because sweat is warm but because evaporating water uses a large amount of heat to change phase. If this weren't the case, people would die of heatstroke just standing around any time the temperature got much over 100.

To raise one gram of liquid water from 0C to 100C takes 100 calories (small c, the heat unit, i.e. 1cal=4.18J). To evaporate that same gram of water, turning it from 100C liquid water into 100C water vapor takes 539cal, and you haven't changed the temperature a bit.

If that water is touching your skin when it becomes water vapor, it absorbs a fair amount of that heat from the skin, helping your body stay cool. If liquid water/sweat gets blown off your body as a mist, it absorbs all the energy for the phase change from the atmosphere and does essentially nothing to cool your body.

When you wear a "rapid wicking" t-shirt on a very hot day (say 105F/40C) while riding, especially in a dry climate, your sweat gets wicked and then blown off your skin to evaporate on the shirt or in the breeze. Same goes for that t-shirt under a mesh jacket as the wind flows freely through. Put a vented, solid jacket on with a heavier but tightly-fitting cotton t-shirt (extra points for long sleeves) and you get soaked in sweat, but all that water is evaporating while touching your skin, and it cools your body far more than it would just getting blown away.

If all that sweat is blowing away without cooling your body, the body's natural reaction is to sweat more. All that extra sweat still blows away and now you're really farked: you can't keep your temperature down and you're blasting precious water into the atmosphere.

That's why riding on a really hot day in just a t-shirt feels awesome as your clothes dry out after sitting at a stoplight, but at 70mph on the slab (once your clothes are dry) it feels like you're a loaf of bread in an oven and you get thirsty in no time flat.
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Old 07-27-2011, 10:14 AM   #92
klaviator
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I recently picked up a cooling vest at Cycle Gear for $9.95. It works great under a mesh jacket. Soak it in water and it will keep you cool for much longer than a wet T- shirt. I rode for an hour in 90+ temps/100+ heat index. It was still pretty wet after an hour. I'll be trying it on a longer ride this weekend.
If it drys out, just stop and soak it again.
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Old 07-27-2011, 03:05 PM   #93
garandman
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Originally Posted by klaviator View Post
I recently picked up a cooling vest at Cycle Gear for $9.95. It works great under a mesh jacket. Soak it in water and it will keep you cool for much longer than a wet T- shirt. I rode for an hour in 90+ temps/100+ heat index. It was still pretty wet after an hour. I'll be trying it on a longer ride this weekend.
If it drys out, just stop and soak it again.
The ones I found there were $40?
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Old 07-27-2011, 07:42 PM   #94
klaviator
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The ones I found there were $40?
The Cycle Gear house brand used to be MotoBoss, now it's Bilt. They were clearing out the MotoBoss vests for $9.95. Best I could tell they were identical to the $40 Bilt vests which are now on sale for $30. The $9.95 vests are probably all gone.
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Old 07-27-2011, 07:50 PM   #95
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Quote:
Originally Posted by cliffy109 View Post
I'm going to cut and paste another member's explanation for this. The reply was to a similar question in this thread in the equipment forum by der_saeufer. This is the first time this concept has been explained to me in a way that made sense. It is making me re-examine my views on mesh.
Pasted from my followup in the other thread:

After re-reading my post today I do feel compelled to point out that mesh is NOT always a bad thing. If you're riding in town or doing some lower-speed riding (e.g. slow forest roads), that added airflow helps your sweat evaporate, especially where it's humid. When you're riding the slab across Arizona, though, too much of a good thing can literally kill you from heatstroke and dehydration. Mesh also helps evaporative cooling vests work better--you're trying to evaporate a hell of a lot more water with one of those than a sweaty t-shirt.
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Old 07-27-2011, 08:17 PM   #96
eskimo
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Good info. in this thread. Only thing I can add is a nice starting point to the day: Stick helmet in your home freezer before heading out. Adds a cold start to a hot day. Don't tell my wife.
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Old 07-28-2011, 11:48 AM   #97
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Thanks Cliffy - and everyone else. This DOES make sense.

So the DriFit shirt should be reserved for rainy weather when I need to dry out quickly and the long-sleved Merino wool shirt is what I want for a sunny day.

Yay! I can't wait to see how disappointed my riding partner are when I stop wearing wet t-shirts. ; )
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Old 07-28-2011, 12:45 PM   #98
MotoTex
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I understand why mesh is a bad idea in extreme heat. But if I'm on a long trip with variable weather in July or August, is there a way to make the mesh work?
If you have a windshield, mesh will work for you. Otherwise, as DAKEZ indicated, do something to block the direct airflow at the front of the jacket. Place some sort of wind-blocking layer between the jacket and your shirt. I wouldn't cover the back, as that is a good place for cooling evaporation from low-speed airflow.

My gear is mesh top and bottom, and I ride year round in it.

Last weekend it touched 110 on the way home from a 300+ mile lunch run. Under the jacket I was wearing an REI wool T-shirt, cotton skivvies, and Smartwool socks. That's it for under layers in the Texas heat for me.

Behind the windshield I think that only parts of my arms and legs are in any direct airflow and this seemed to be supported by the fact that at gas stops when I unzipped my jacket the T-shirt was patchy with sweat spots, neither soaked nor dry. I imagine that my core temp remains more constant as the body is adjusting blood flow to the extremities being used as radiators and swamp coolers out in the breeze. But then, I do have a vivid imagination.

After the ride it seemed that I stayed as comfortable as one likely could in this environment, drinking lots of water and unsweetened tea throughout the day. Probably something like a gallon and a half of total fluids consumed, though I was still a little dehydrated.

My gal, riding her own bike and being considerably smaller, seemed to suffer more from heat build-up and fatigue wearing her mesh gear behind a windshield. The mesh was supplemented with one of Frog Togs' triangle thingies that you soak in water and wear around the neck and drape down the body in front or back. That thing would dry to a hard chamois state in less than an hour.

I don't think she consumed more than a half gallon of fluids, and some of that was soda rather than water. When we got home her skin was still hot to the touch after laying exposed to the A/C for ten minutes. Not a good sign. Gonna have to emphasize/encourage drinking more water, Gatorade, etc. on future trips in the heat.

Another difference between she and I is that I mountain bike, and my body is accustomed to shedding heat. She spends most of her time indoors and doesn't follow any athletic pursuits. This may play as big of a part as anything in preparedness for managing temperature extremes.

The body will adjust the internal systems and plumbing to manage the environment it usually spends time in. A sedentary life has little call for high blood flow, sweat production, etc., and those public utilities may not be up to the task of dealing with suddenly imposed extremes.

Physical fitness may be another aspect of temperature management that doesn't get as much attention, yet could be helpful as well.
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Old 07-28-2011, 12:49 PM   #99
DireWolf
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Not sure if it's been posted in here, but this just got rave reviews from someone riding in 115* weather/125*-ish heat index. He didn't break a sweat.

http://www.veskimo.com/
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Old 09-03-2013, 07:47 AM   #100
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Originally Posted by DireWolf View Post
Not sure if it's been posted in here, but this just got rave reviews from someone riding in 115* weather/125*-ish heat index. He didn't break a sweat.

http://www.veskimo.com/
I have a VEskimo...I love it...but I can't get my riding buddies to fork over the $500 investment, so I don't do much long distance riding when the temps get over 95F+...I've done over 12+ hours over 2 days(all super slab)...with temperatures averaging 98F with the VEskimo...and froze my butt off...I recommend getting the adjustable cooling controller . It will also allow the ice to last longer...

I have the 9qt cooler...think I'm going to get the backpack so I can do some dirt bike riding when it gets hot...
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Old 09-03-2013, 11:40 AM   #101
MotoTex
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Did a little lunch run to celebrate the Labor Day holiday. It was well over 93F (skin temp) for most of the ride.

I left the house with no particular destination in mind. By the end of the day I had ridden 400 miles in eight hours. Most of it was on back roads. Even counting the time spent at all the stops, the average speed was 50 mph, which surprised me as I wasn't pushing it all that fast.

Over the course of the ride there was a sit-down lunch with copious amounts of iced tea, next I wandered around Luckenbach for a few minutes at another stop, then over the ride had a couple of stops at gas stations to top up the tank, and one more stop under a shade tree to eat a bag of peanuts and down a quart of Gatorade.

Overall, there were probably a gallon of fluids consumed on the ride and another three pints when I got home.

Wearing 100% mesh gear that includes foam armor at the shin/knee, thigh, hips, ribs, back, forearm/elbow, and shoulder that did a good job of reducing the airflow reaching the skin. This provided moderate evaporation while riding behind the 800XC windshield. I wore a cotton T-shirt and bike shorts under the suit. They remained on the drier side of lightly damp most of the day.

Hot temps can be comfortably managed when you are able to remain hydrated and provide a moderate airflow under the gear.

It was a great ride. I had no idea it had been 400 miles until I goggle-mapped the route. Another typical Texas Summer day ride.
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