Welcome, guest [login | register]

Posted by Bill S on November 29, 2007 at 8:11:33 pm EST
In reply to Re: Closed Cell Pads posted by cknipple on November 29, 2007 at 5:30:31 pm EST

Couple things to check. In theory (that is, manufacturers' instructions), all you have to do to inflate them is open the valve, let it sit for a while, and the pad will inflate to the proper firmness. In reality, you have to add a little air. Problem is, most people get impatient and start blowing in their hot air (it only cools slightly from the body temperature in your lungs as it goes through your mouth and through the valve into the pad). Overnight, the air in the pad cools (it's on the cold ground, or for some of us, on the glacier or at least snow), which means the air pressure drops. By morning the pad is quite soft. The remedy for this is to let the pad inflate by itself for a while (set up your tent when you arrive in camp and unroll the pad with the valve open). Make sure you haven't put anything on the pad that will keep it from fully inflating. Cook your supper, chat with your friends, watch the stars, etc. Then, just before you get ready for bed, blow enough air in to make the pad really firm, even hard, and while still blowing, screw the valve closed. This way, it will still cool during the night and get a bit softer, but it won't be as soft.

Using a blue foam under the pad in snow and ice conditions helps a lot (there is a huge debate when using double pads on the glacier whether to have the ensolite on top or under the inflatable - if it's on top, it insulates you from the cold air in the inflatable and keeps you warmer, but if it's on the bottom, the inflatable stays warmer and firmer, giving more insulation than the other way around - take your choice).

When I have been on expeditions where we stay in a single camp for a while (such as spending a week waiting out a storm), I add a little air each day when the pad has cooled, and after the 2nd or 3rd day, it stays just the right firmness).

Hey, that's another advantage of ensolite pads (ie, closed cell). They do not have the problem of the air in inflatables cooling and thus losing pressure.

By the way, take a look at what the interior of your inflatable is like (it's in the advertising literature). Some of the thicker "comfort" pads have hollow tubes running through the internal foam, and others have other shaped cutouts. These intentional voids make the inflatable lighter, fill faster, and compress smaller. But they also have lower R-values than a "solid" foam, and those voids allow the air to cool more and compress more as their pressure drops due to dropping temperature in the pad. For example, it turns out that the "classic" 1-1/2 inch Thermarest has a higher R-value than the "comfort" 2-inch version (I got this from Cascade's literature). The "classic" is also significantly lighter and compresses smaller. Some people find it too firm, but I would rather stay warm when out in -40 degree weather, sleeping on ice.

You might also check that you do not have any leaks. Sometimes the valve does not seat completely, and sometimes a leak can develop where the valve is cemented in place. You can also get a pinhole somewhere in the pad without realizing it. One of my buds on a Denali climb had a tiny leak that left him with only the blue foam keeping him off the ice each morning. Finding a leak in sub-zero weather is a real challenge! We did manage to find it on about the 4th or 5th day, put on a patch from the official kit, and he slept warm and in comfort the rest of the climb. You can check for leaks more easily at home. Fill the bathtub with water. Blow the pad up as hard as you can. Then stick the pad under water and carefully examine the whole pad, including the valve, for any bubbles. It only takes a tiny bubble, forming and breaking loose at 30 second intervals to deflate the pad overnight (sound familiar from your bike tire fixing days as a kid? Same idea!). Once you find the pinhole or leaky valve, use the official kit to patch it (the official kit includes a tube of glue that has to be heated in boiling water, but really makes a solid seal).

Replies

View: flat | threaded

• Re: Deflating inflatables - calamity 21:01:50 11/29/2007

Post a Reply

Before replying, please read the complete thread.