BDU sleeve roll up

[TexasBEAST]

It's a practical exercise in thermodynamics, to help the cadets (and SMs?) with their aerospace studies.

Sleeves down reflects solar radiation in order to reduce absorption thereof. But it also causes retention of internal body heat & humidity, by carrying around a layer of heated air just above the skin. Open cuffs can help mitigate that, and pit vents would help even further.

Sleeves up allows for some limited release of body heat & humidity (depending on how tightly they're rolled), while also allowing for some cooling via convection as wind blows over the exposed skin. But that same exposed skin is also vulnerable to absorption of solar radiation.

Generally speaking, it's supposed to be a whole lot more effective to minimize exposure to heat, than to allow oneself to be heated and then to try to reduce that excess heat (i.e., cool back off). Stay ahead of the problem, instead of playing catch-up. Be proactive, rather than reactive.

[Luis R. Ramos]

Texas,

If that is the case, why do we teach that in a survival situation in a desert to dig a hole in the sand, place a cover above us, then place another cover over that?

With your reasoning, those two covers retain heated air. And the best solution for cooling in the desert is not to have any cover at all!

[LSThiker]

Texas,

If that is the case, why do we teach that in a survival situation in a desert to dig a hole in the sand, place a cover above us, then place another cover over that?

With your reasoning, those two covers retain heated air. And the best solution for cooling in the desert is not to have any cover at all!

Who teaches that?  You should not be digging any holes in the desert as it has been found that you waste a tremendous amount of water in that exercise. This also includes digging a hole for a solar still. Also by digging a hole you not only waste water, but also reduce the airflow around you, which is vital in the body's ability to cool itself 

All Texas is saying is that it is better to keep the sun off of direct skin due to solar radiation heating you up. It is also to keep away sunburn, which can also dehydrate you.  One of the most important things to do in the desert is to find shade or at least create it.

Edit:  I wanted to mention that the solar still in the desert is a survival myth that has been told so many times that even some survival experts believe it.  However, the process of building a solar still (or simply digging a hole in the desert) wastes more water than what you will get back from it.  Therefore, it is a total waste.  This myth falls into the same category as moss on the North side of trees, drinking from cactus, sucking snake venom out, drinking pee will save you from dehydration, boiling water for 10 minutes, etc.

[LSThiker]

Can you post a link to that AMEDD statement?

I was unable to find the document that I wanted. Just unofficial documents and statements published by AMEDD.

[sarmed1]

...
Sleeves up allows for some limited release of body heat & humidity (depending on how tightly they're rolled), while also allowing for some cooling via convection as wind blows over the exposed skin. But that same exposed skin is also vulnerable to absorption of solar radiation....

actually sleeves down works more effectively for convection than sleeves up, perspiration evaporates quicker from the skin than from the moistened material of the BDU's, thus the effect time of convection lasts longer than from that of bare skin. 

This is one of my most annoyed summer CAP issues.  The thermometer hits 85 and people are throwing off the BDU blouse as a heat injury prevention tool.  (first its supposed to be based on WBGT, but whatever) secondly that "protection" is geared more toward strenous activity; sitting around in classroom or marching from point a to point b is not strenuous activity.  Maybe in an ES related environment I can see the argument, but you are countered easily on the other safety issue as far as abrasion and tick prevention issues vs just maintiang adequate hydration to decrease the heat injury potential.

mk

[Luis R. Ramos]

LST,

The US Army teaches it!

Page 51 of the US Army FM 21-76. Called the Below-Ground Desert Shelter. Also they teach the Open Desert Shelter.

These have been re-published with the same names in their publication FM 3-05.70, Survival, with a date of 2002. Which the US Army Directorate of Publications still has online. Not rescinded, which means it is still valid for them...

[LSThiker]

LST,

The US Army teaches it!

Not rescinded, which means it is still valid for them...

There are your key words "for them".  The Army has to be concerned about tactics as well:

Surviving and evading the enemy in an arid area depends
on what you know and how prepared you are for the
environmental conditions you will face. Determine what
equipment you will need, the tactics you will use, and the
environment's impact on them and you.

Last I checked, we are not surviving AND evading the enemy.

What I would do in a civilian situation is far different than what I would in a combat situation.  Since we are not evading an enemy, digging a hole is a waste of water.  Even in the manual it states "ration sweat, not water".  The open desert shelter, which is what I stating earlier, is the route that is most applicable to CAP and the US.   

[THRAWN]

...
Sleeves up allows for some limited release of body heat & humidity (depending on how tightly they're rolled), while also allowing for some cooling via convection as wind blows over the exposed skin. But that same exposed skin is also vulnerable to absorption of solar radiation....

actually sleeves down works more effectively for convection than sleeves up, perspiration evaporates quicker from the skin than from the moistened material of the BDU's, thus the effect time of convection lasts longer than from that of bare skin. 

This is one of my most annoyed summer CAP issues.  The thermometer hits 85 and people are throwing off the BDU blouse as a heat injury prevention tool.  (first its supposed to be based on WBGT, but whatever) secondly that "protection" is geared more toward strenous activity; sitting around in classroom or marching from point a to point b is not strenuous activity.  Maybe in an ES related environment I can see the argument, but you are countered easily on the other safety issue as far as abrasion and tick prevention issues vs just maintiang adequate hydration to decrease the heat injury potential.

mk

Even in an ES situation the AETC guidance doesnt support it. Keep the shirt on and the sleeves down. Prevents sunburn and environmental injuries.

[THRAWN]

LST,

The US Army teaches it!

Page 51 of the US Army FM 21-76. Called the Below-Ground Desert Shelter. Also they teach the Open Desert Shelter.

These have been re-published with the same names in their publication FM 3-05.70, Survival, with a date of 2002. Which the US Army Directorate of Publications still has online. Not rescinded, which means it is still valid for them...

21-76...Army humor. I may be wrong, but doesnt CAP have guidance on "survival"? Pretty sure diging a fighting/evasion position isnt in it...

[sarmed1]

In this case it isnt about  fighting position, the theory is that the sand in the pit is cooler than the sand outside the pit, the double covering is supposed to help keep the inside pit temp cool with some magic combination of reflection on the outer layer, and air movement cooling off the middle layer (im an not sure I buy this one, but whatever).  On the converse side it can get very cold at night, so the shelter then also functions to keep you warm in the overnight via body heat.

mk

[LSThiker]

In this case it isnt about  fighting position, the theory is that the sand in the pit is cooler than the sand outside the pit, the double covering is supposed to help keep the inside pit temp cool with some magic combination of reflection on the outer layer, and air movement cooling off the middle layer (im an not sure I buy this one, but whatever).  On the converse side it can get very cold at night, so the shelter then also functions to keep you warm in the overnight via body heat.

mk

It is not about a fighting position, but it is about an evasion position as well as a shelter position.  I have experience building this position and can tell you that I don't believe the stated temperatures in cooling.  The materials that I had at hand turned the thing into an oven for a daytime shelter.  The amount of work that goes into digging into hard desert/rocky terrain is not worth the effort (wasted water) or the savings (temperature).

[PHall]

In this case it isnt about  fighting position, the theory is that the sand in the pit is cooler than the sand outside the pit, the double covering is supposed to help keep the inside pit temp cool with some magic combination of reflection on the outer layer, and air movement cooling off the middle layer (im an not sure I buy this one, but whatever).  On the converse side it can get very cold at night, so the shelter then also functions to keep you warm in the overnight via body heat.

mk

It is not about a fighting position, but it is about an evasion position as well as a shelter position.  I have experience building this position and can tell you that I don't believe the stated temperatures in cooling.  The materials that I had at hand turned the thing into an oven for a daytime shelter.  The amount of work that goes into digging into hard desert/rocky terrain is not worth the effort (wasted water) or the savings (temperature).

The main thing you want to do is get out of the sun. And the less energy and water you consume in doing that, the better.

[TexasBEAST]

Texas,

If that is the case, why do we teach that in a survival situation in a desert to dig a hole in the sand, place a cover above us, then place another cover over that?

I believe that the "cover" they're talking about is some sort of poncho, parachute, or tarp material. That is large-surface-area stuff. The large-surface area is supposed to provide shade over your entire person, which serves to REFLECT SOLAR RADIATION. (Think my blaze orange boonie on a much, MUCH larger scale!)

And it's not right up against your skin like clothing, such as the BDU blouse, so you can potentially get some wind current in between that material and your skin, and between the two layers of material, which provides for convective heat loss.

With your reasoning, those two covers retain heated air. And the best solution for cooling in the desert is not to have any cover at all!

No sir, with my reasoning, tight-fitting clothing (such as tightly-rolled sleeves or the fabric that's buched up underneath one's LBE or LBV) is what retains heat and humidity.

The best solution is to block solar radiation. Go sleeves down, and unbutton the front and the cuffs. Dump or loosen your belt. Don a boonie. And pitch a tarp shelter overhead, too. Block that sun!

[TexasBEAST]

Edit:  I wanted to mention that the solar still in the desert is a survival myth that has been told so many times that even some survival experts believe it.  However, the process of building a solar still (or simply digging a hole in the desert) wastes more water than what you will get back from it.  Therefore, it is a total waste.

Do you mean that when you dig a hole in the desert floor, water doesn't just magically appear out of thin (hot) air? 

I've gotten some solar stills to work before, but not in the desert. They were in humid temperate forest regions (Boy Scout Camps). The ground and air were both moist.

But they still didn't produce much. We're talking a desperation measure, for sure.

[TexasBEAST]

actually sleeves down works more effectively for convection than sleeves up, perspiration evaporates quicker from the skin than from the moistened material of the BDU's, thus the effect time of convection lasts longer than from that of bare skin.

I guess it depends on how we define "more effectively". That rapid evaporation means rapid, dynamic transportation of both heat and humidity away from the skin. I'd call that pretty darn effective!

Wearing sweaty, wet clothes around will slow the rate of evaporation of body moisture, as well as slow the rate of convection of body heat away, because the soaking wet clothes serve as a warm, wet blanket. Only the outermost moisture and heat can actually be convected away. Meanwhile, all of the rest of that heat and humidity against the skin stays right where it is. (Hello, skin rash.) Yes, the rate of evaporation is slowed, which mean the rate of convection is slowed, but you also retain the heat and humidity from your perspiration much longer. Dragging out the process of releasing heat and humidity from your clothes is not gonna help you to release heat and humidity from your body. It's gonna work against you, won't it?

I know that when I run in SE TX, with 85 degrees and 70% humidity, I cool off better going shirtless than I do with wet UnderArmour. Yes, I have to time my runs so that I've got shade by the trees from the direct sunlight. But dumping the soaking wet layer of fabric and letting the sweaty skin directly vent into atmosphere is the best way for me to beat the heat while working out.

[sarmed1]

I believe the process is somewhat dependent on the current humidity.....lower humidity and high air temp with slight breeze the ideal for the concept.....NM and AZ good.....TX, LA, FL...maybe not so much

MK

[SarDragon]

If you want to reflect the "solar radiation", you need to use light colored, or silvered materials. Dark stuff retains the heat, and just makes things warmer. A camo poncho makes a less than satisfactory shade in still air.

As for "solar radiation", you need to remember that we're dealing with two types here - ultraviolet, which gives you a sunburn, and infrared, which makes things warm/hot. Each has different effects on the body, and should be treated specifically.

[Luis R. Ramos]

Oh my God! Texas, you will bring the CAP Inquisition! You mentioned the b____e word!

...Don a boonie..

[AlphaSigOU]

Oh my God! Texas, you will bring the CAP Inquisition! You mentioned the b____e word!

...Don a boonie..

That is the word that will curve your spine, grow hair on your palms, and bring us - God forbid - peace without honor! 

[TexasBEAST]

I believe the process is somewhat dependent on the current humidity.....lower humidity and high air temp with slight breeze the ideal for the concept.....NM and AZ good.....TX, LA, FL...maybe not so much

MK

Yep. That's the part that UnderArmour, et al, fail to include in the fine print. Their garments are really only effective for specific climates, even though the companies market to pretty much all of them.

In more extreme climes, it's best to avoid overexposure in the first place, rather than depending on some reactive tricks or products or materials to bail you out, after the fact.

Oh my God! Texas, you will bring the CAP Inquisition! You mentioned the b____e word!

...Don a boonie..

That is the word that will curve your spine, grow hair on your palms, and bring us - God forbid - peace without honor! 

Boonie, boonie, BOOOOOOO-NIEEEEEE....

Or that old Billy Idol standby, "Boonie Boonie!"

Or like the creepy little Budweiser penguin from the '90s might say, "Boonie...boonie-boo..."