Mar 29, 2008 at 6:12 am #1228046
I came across Bill's blogpost on his Poly Tube DAM a oouple of days back and I am impressed. It is amazing work.
Here is the link:
You will understand my idea better if you are accuainted with Bill's Poly Tube DAM idea.
He wanted ideas for multiple use of the down baffles used in poly-tube. That really got me thinking. He has some ideas like making the baffles in such a way that it could be turned into a pocho. He doesnt elaborate on how this can be done and I dont know how it can be done in an easy way.
My idea is make a quilt double the size and half the loft required of the sleeping pad. There has to be a resealable head opening in the middle. This quilt can be used during the day, rest stops, camp as a pocho jacket.
While sleeping it will folded in half and is to be placed in poly 'bag'. The poly bag will be sealed on three sides and the one bottom will be open. All one has to do is roll up the extra portion of the poly bag. Bill has used a clip for each of his poly tube -these clips should work good. I am still thinking of a ideas for the valve. I found Thermarest valve replacement kit. If it works it would be cool.
The theory is that when you lie on the down it compresses and the insulating property is lost. In a polybag down is surrounded by air which assert pressure back and down is not flattened. Now the key to my idea is that there should be just enough air to withstand the body weight and prevent the down form compressing. Any more air and it could get uncomfortable and you will slide off.
The quilt can be used in warmer weather where you wouldnt need the insulation of Down.
Bill has got some great ideas. He suggests use as a water bag. Another idea is to use light insulation like single layer 2.5oz xp.
The poly bag can also be used as backpack pad. My estimate is that poly bag shouldnt weight more then 2oz. Thats should be lighter then your original pack pad.
The poly bag DAM is used during the day as poncho jacket and a pack pad. Its secondary use will still lighter then the gear it replaces. Lets be fair. I would call this "0oz" sleeping pad.Mar 30, 2008 at 10:52 pm #1426303
Post removed: I had posted an interesting idea about how you can use your sleeping pad as a backpack/bivy bottom. But after calculation I find weight saving not good enough to compromise the ease of packing a backpack gives. If anyone wants to know about it, pm me.
Some more details: the poly will be heat sealed in such a way that a pillow is formed on the top side. There will be no insulation in the pillow as I expect to carry a down hood/balaclava anyways. It will be heat sealed twice or thrice so that there are splits resulting in multiple air chambers for greater comfort. I think it would be a good idea to have seperate valves for the pillow and matt since I would like pillow to be a bit higher the matt and so it need to be more inflated.
Also, I dont think it would be a nice feeling sleeping on plastic. So Im thinking of using a layer of momentum taffeta for ultimate comfort. Know of cheaper, lighter alternative? Let me know.Apr 2, 2008 at 11:36 am #1426759
guys, I would appreciate some feeback on this idea.Apr 3, 2008 at 11:40 am #1426918
Ross BleakneyBPL Member
In general, I like your ideas (even though much of it is out of my league). I very much like the idea of a pillow made with horizontal tubes. You get this "for free" as part of your overall design, but I think this is a good pillow shape. The cheap inflatable pillows tend to suffer from the same problem. They are essentially spheres. If you inflate them fully, it is like using a soccer ball as a pillow. If you don't inflate it fully, it squishes around every time you move your head. Using a set of tubes (next to each other) allows for a more solid, box shape. In fact, if you could make an inflatable pillow with one of those tubes (maybe create a spiral) then I would be interested in that by itself. So would a lot of other people. You might need a little more "fluff" on top, but in general, I think that would be a really good, lightweight pillow.Apr 3, 2008 at 1:17 pm #1426943
Rog TallblokeBPL Member
@tallblokeLocale: DON'T LOOK DOWN!!
If I understand you correctly, you plan to place the quilt in a single poly bag which will be inflated to prevent the down compressing. The problem is that you can't get the pressure right to take an unevenly distributed weight like your body. This is why Bill uses 6 or seven tubes. With a single air chamber, your backside will be on the floor while your legs and shoulders ride uncomfortably on a hard convex surface.Apr 3, 2008 at 9:53 pm #1427038
Ross, thank you for the nice comment. Such a pillow would be a very easy DIY project. All you need is heat sealable Nylon fabric (available at seattle fabrics and owfinc) and a thermerest valve kit. Cut the nylon to the size of the pillow you want and add the valve on the top. Then using a hot iron seal it on the sides and make mumber of horizontal seam (depending on the size of the pillow). Just be careful to leave a few mm space between seams and the top side so that air can pass to all chambers.
I better tell you this. I havent used thermarest valve myself. But I think it should work. Give it a try.
Rog, you are right. I think I have a way to get around this. My idea is to have two horizontal air chambers to give structure, one on each side with opening such that air freely move about. This may help to maintain a more uniform pressure.
Another idea, which is like going back to bill's, is to make the quilt with horizontal baffles such that each baffle can be zipped off to be separated -like a 2 person quilt- and then we can have a poly bag with multiple chambers (like I described for the pillow above). Each baffle can be inserted in a chamber and then the bag can be closed.Apr 3, 2008 at 11:19 pm #1427047
nanook ofthenorthBPL Member
good luck, having used some air mattresses in the past, I find most have 'baffles' every 4-5 inches running the length of the pad to stop the ballooning Rog talked about. I'm thinking one baffle may not be enough.
An idea might be to use two tall baffles about 4 inches wide, one on each edge of the pad with a larger lower one forming the sleeping surface proper. Still good luck. Rolling up the edge (?) is not going to be able to keep the air in, you'll need some type of airtight seal that can resist the pressure of your body weight and then some AND allow you to pressurize the pad high enough to support your weight.
I'd love to see your idea in practice, but I'm a bit of a cynic when you start to think about the technical challenges involved. Good luck and post what you come up with.Apr 3, 2008 at 11:32 pm #1427049
nanook ofthenorthBPL Member
how about buying a AirCore pad?
you have good ideas but once you start to talk about zippering or velcring apart a quilt into thin horizontal strips, I think your going to end up having a heavier system then just using a AirCore pad.
For your system to be competitive, the under quilt and pollybag would have to collectively weight less then 20 oz the aircore does. You could use lighter materials (like the bubble bed) but the Aircore design inherently uses less materials then your design.
You'll have to find a way to make up the lost weight, if your looking to produce something that is weight competitive.Apr 4, 2008 at 2:32 am #1427060
Robert, thanks for the comments. Your feedback has given me some new ideas.
I looked at various ways to reduce weight. Baffles made of silk like Bill uses will be lighter then those made of nanoseeum or 1.1 ripstop. Only way to go still lighter is put down directly into into chambers of the polybag. I dont know if this will affect the down.
Since there will be an split in the middle for use as poncho, making horizontal baffle is easier. Three side of every chamber will be fully heat sealed and on one long side each chamber will be heat sealed 95% and the remaining opening will be patched by momentum so that down doesnt come out. A valve will be inserted at one corner of the long side. So all chambers are inflated at once.
Momentum will be used as shell fabric for the poly. I have a momentum quilt and I love it.
Wamlite DAM & Bill's DAM both use 7oz of down. My estimate is that poly bag will weight about 2oz and momentum will weight not more then 2oz. I intend to have two #3 YKK zipper on three sides till the shoulder such that one or two quilt/top bags can be zipped on to the DAM. This DAM/top quilt design make the most efficient use of insulation.
I think the total weight of this would be about 12oz. That is much lighter then the 20oz Aircore pad and can also be used as poncho at rest stop/ camp.
update: polybag DAM give me terrific advantage. I can put on poncho over my shell -when taking a break or around the camp- without worring about down getting damp/wet.Apr 10, 2008 at 11:32 pm #1428096
Only way to go still lighter is put down directly into into chambers of the polybag. I dont know if this will affect the down.
I was thinking about this yesterday when I realised what if polybag accidently bursts? … I think using silk baffles is worth the very small weight penalty.
and the remaining opening will be patched by momentum so that down doesnt come out.
Patching the opening is not required now.Apr 11, 2008 at 12:52 pm #1428184
i dunno if this will help, but you could fold one long poly bag in a zig-zag or coil pattern filled with down so there would be very little sealing involved. A silk shell could keep it in placeApr 12, 2008 at 11:37 am #1428292
i dunno if this will help, but you could fold one long poly bag in a zig-zag or coil pattern filled with down so there would be very little sealing involved. A silk shell could keep it in place
David, thats a good idea. It should work while flat but I dont think the tube will stay in place while wearing it as a poncho. That could cause cold spots.
Right now, I am not too sure the polybag idea will work as I thought. The problem is that the heatseal would create cold spots since the baffles are not continuous. The only way to make baffles continuous is to use poly tubes. Inflated poly tubes can heatsealed/glued together.Apr 22, 2008 at 12:32 am #1429452
Thought I will post an update. I think I have solved cold spot problem. The idea is to use sheet of fabric to create a wall between baffles.
This prevent the pad from become a balloon when inflated. I think using cuben fiber eliminates need for both poly and the shell fabric. I wouldnt sleep directly on silnylon so the next cheaper alternative is 1.9oz coated ripstop. Either seam sealant or heat sealable tape can be used for to water proof the seams.Apr 29, 2008 at 9:51 am #1430699
@finallymeLocale: Utah desert
I see a few things that might go wrong.
Are you sewing the baffles or heat sealing them? It will be really hard to heat seal the baffles with an iron. You can try getting strips of fiberglass film coated with teflon. Use it under your seal area to prevent other parts from being sealed. If you are sewing them, it could also prove very difficult sealing your stitches. Seam sealant is waterproof, but is it air tight as well? I don't know. Something to test out before making the whole thing.
Do you know if you can heat seal cuben? It is made out of HDPE, so it probably can be heat sealed. Again, try it before hand.
Do you know if cuben is airtight? It might just be waterproof. Again, I don't know the answer to this, something to test out.
Before you ditch the poly, try sealing a small patch of cuben and filling it full of air. Put weight on the "pillow" you just made and see if it holds air for more than 8 hours.
Your design looks good, but I would also test out your construction techniques and materials first.Apr 29, 2008 at 11:27 am #1430718
This is an interesting project. You have good ideas. Last year I made a down-filled cuben sleeping bag with integral pad, so I thought I might contribute a couple of things I learned.
Cuben is UHMWPE fibers between layers of polyester film. It doesn't heat seal well, in my experience, because the fibers shrink and deform the material at a much lower temperature than that required to seal the polyester film. Also, although cuben is absolutely airtight and has good tensile strength, the resistance to puncture is poor. Thorns that can't get through 0.75 oz nylon will puncture the lightest cuben pretty readily.
Also, here in Oregon the relative humidity is often high, and I found that nighttime cooling would cause dew to condense and wet the down in the outer layers of my sleeping bag. Because the shell (inner and outer) was cuben, it was very hard to dry out. It just had a small valve, like an inflatable pad. New dew just formed each night, and the down got wetter and wetter. I don't know if the same might happen in a DAM.
The Cuben fiber staff recommends a Loctite two-part urethane adhesive called Hysol U-09fl for bonding cuben. I actually used the low viscosity version, U-09lv, and found that an extremely thin film of the adhesive produced a lightweight bond stronger than the cuben itself. Tape is simpler, but much heavier, and I've heard anecdotes about tape failure in very cold weather.Apr 29, 2008 at 7:26 pm #1430816
David, Collin thanks for the comments.
>Are you sewing the baffles or heat sealing them?
I am planning to sew/seal only the edges. For constructing baffles walls I am planning to use adhesive.
>Seam sealant is waterproof, but is it air tight as well?
I suspect anything that is waterproof is airtight unless the fabric is WPB. But that is something I need to test before I can say for sure.
>Do you know if you can heat seal cuben?
I dont. (Collin has answered the question.)
But Questoutfitters sell 'CUBEN TAPE'. Here the description from their website:
Double sided tape that works great with Cuben Fiber fabric. Just peel the celophane paper from each side and adhere it to the the Cuben fiber to form the seam. No sewing required for most projects. Extremely strong and very water resistant.
Since they are calling it water resistant I am not sure if it will be airtight.
>I found that nighttime cooling would cause dew to condense and wet the down in the outer layers of my sleeping bag.
Interesting. Since cuben is airtight it shouldnt have happened. What ever the outside humidity moisture could not have collected inside the bag unless:
1) The inflated air had a lot of moisture in it.
2) It didnt seam seal properly.
I guess even if you use a pump and outside air has a high relative humidity the bag will still get wet. One solution is to use dessicants. Molecular sieve is a very good dessicant. Only retail source I have found is this:
the sieve can absorb 25% of its weight in water. It is reusable. So you have to calulate the the weight of the air in the bag, % of vapour in it and then make a inflating tube with optimal amount of molecular sieve it it. I am feeling lazy right now so let me know the results when you are done.
Poly option is still under consideration. It is cheap and about as light as cuben and I can make a very light silk shell.Apr 30, 2008 at 10:55 am #1430901
Yes, it was the moisture in the outside air that condensed, I think. I used a bag pump for inflation. Nighttime temps often drop well below the dew point in my area, so cooling of the outer layers of the sleeping bag not only caused loss of baffle volume and compression of the down from gas contraction but also wetting of the down from condensation.
I actually did end up trying a dessicant and it helped but made the whole system too heavy. I pumped the air through a small aluminum tube full of silica gel and molecular sieve dessicants with indicator salts. I heated the tube over my little stove each day to regenerate the dessicant.
In the end it offered no weight benefit and was too complex, fragile, and fallible. It was a fun project, though, and might have been a success in more capable hands, I guess.Apr 30, 2008 at 11:49 pm #1431006
>I actually did end up trying a dessicant and it helped but made the whole system too heavy.
Collin, how much dessicant did you use?
Saturated air at 20 degrees C contains about 17.12 grams of water per cubic meter. Air at 50% RH contains 8.6 grams per cubic meter.
Even 50gms of molecular sieve would be enough.May 1, 2008 at 8:29 am #1431038
I don't remember the total mass of dessicant, but I obtained adsorption capacity curves with respect to temperature at a constant RH and RH at a constant temperature for the molecular sieve (which I obtained from a company called Sorbent Systems, I think) and for the silica gel. I found my dessicant mass based on a goal of a 40% RH atmosphere in the baffles after inflation with 100% RH outside air (realistic in my area) and subsequent nighttime drop from 20 degrees C to 5 degrees. In the calculations I assumed outside temps and no temperature gradient (no warm sleeping person) in the baffles for simplicity and to give me a little extra condensation protection. I used an aluminum cigar tube with silica gel at the outside end (better at high RH), and molecular sieve at the sleeping bag end (better at low RH). It just about filled up the cigar tube. I also had to carry extra fuel for heating the tube over my stove each day, and a patch kit for the cuben.
I didn't like the fallibility that came with the complexity. If my stove failed, for example, then my sleeping bag would get wet (that never happened). I still think it's kind of an interesting idea, especially for trips in extreme cold when down can turn to clumps of ice in conventional sleeping bags.May 1, 2008 at 10:44 am #1431069
Just checked out sorbent systems. Lot of good info. I think I have been to the site before but didnt realize that they sell dessicants. The coolest stuff is 1 lb can of indicating molecular sieve for $ 21.50!
>I also had to carry extra fuel for heating the tube over my stove each day, and a patch kit for the cuben.
why not use a propore or event/tyvek bag? simply heat it along with water or food you are heating.May 1, 2008 at 11:48 am #1431082
Tyvek has a very low melting point. It might not be easy to get the dessicant hot enough to regenerate in a tyvek bag. PTFE-coated nylon, like e-vent, would be better, but still nowhere near stove-exhaust temperatures. That's why I chose an aluminum tube. Also, the hotter the dessicant the less moisture it will take up from steam in the stove gasses (burning butane and propane produces water vapor).
Also, the tube made it easy to pump outside air, from a poly bag, through the dessicant and into the sleeping bag (I cut the tube so it was open at both ends).
A clever design could probably get around these minor obstacles, though. A fabric bag might work for your DAM.May 1, 2008 at 12:03 pm #1431087
Richard NisleyBPL Member
@richard295Locale: San Francisco Bay Area
What orientation to the stove, distance, and heating duration did you find best regenerated your desiccant?May 1, 2008 at 2:28 pm #1431122
I made a wire cradle that kept the dessicant tube out of the flame, in the path of the hot exhaust flowing up around the sides of my little aluminum pot (which I still use; It's one of my favorite pieces of gear. It's the bottom half of a 2-liter Japanese beer can). My windscreen had two holes for the ends of the tube, so the ends stuck out in the cool air. I left it there until the water in the pot boiled. Then I took the tube out, capped it, and put it away until it was time to pump up the sleeping bag.
I wasn't really happy with the way it looked or with the field utility in the end so I never took pictures and the materials got recycled (the down and the hardware, anyway). I still have the pencil sketches which I can scan and post if that's useful to anyone.May 1, 2008 at 6:12 pm #1431168
Oliver BudackBPL Member
With all the neccessary respect but did you ever finished one of your projects?
I'm reading a lot projects you have started, recently. Some sound pretty fanciful.
One the other hand you are planning a trip to the Everest, based on those projects. Due to the fact that i have never seen a finished myog-project i would strongly advice to finish and test it in "real" conditions, like the ones you will be faced with at the Everest. This will help you to learn more about fabrics and hiking itself. Then you will realize that thinks are sometimes different ;). It will also improve your myog-skills.
Ever made a good double lap seam with silnylon?
Just correct me if I'm wrong.
OliverMay 1, 2008 at 11:36 pm #1431212
Hi Oliver. You are right. I havent finished any of the projects yet.
All issues with DAM design are solved. But I am thinking of getting lightest silk directly from China or Thailand, when I go there next time(for business work). So the project is postponed because of that.
For other projects I am taking my time till the ideas develop into concrete designs. Take sub-2 lb tent idea for example, the plans were going fine. But I realised that it has to be pretty small and low profile in order to balance the lenght of fabric between two poles, keep the side at steep angle and shed wind. So I wasnt satisfied with the compromise. Then Mike's comments pushed me to consider a single pole design. I digged into hex, four side pyramids, alphamid, and two pole designs. So I cant order stuff until I have a design I am satisfied with and have finish all calculations.
You might be interested in the my two pole tent (based on MSR twin sisters) drawings:
Most of the people here are hiking since many years. They started with traditional heavy weight gear and slowly replaced their gear with light wight stuff. They have have bought and sold numbers of backpacks, sleeping bags, tents and other gear – In that process they have built a suitable system for themselves. Many are now converted to UL and some are even SUL.
I started hiking about 10 months back. Fortunately I found BPL very soon. I remember how excited I was when I learned about ultralight gear. I spent a lot of time trying to deciding what gear to buy. If I had money I would have spent it. But I am college student and my parents dont think much about hiking. And hiking here doesnt require anything more then water, food and a small pack. So I decided just to keep reading and keeping myself updated.
Take a look at my Everest base camp SUL gearlist in the gearlist forum. It is a result of brainstorming and not exprimentation. I know I have to test it to find out if it will work but I am really happy how it has turned out.
MYOG ideas give me great satisfaction and allow me to customize. Eg. if I buy shangri la 2 it may not fit with my trekking pole. MYOG allows me to make a tent that will fit perfectly with my trekking pole.
The dual WPB/VB jacket project which uses propore, cordura and silnylon is also postponed till I finish my tent design so that I can buy materials for both together from quest outfitters.
But yes I can practice sewing a nylon jacket in the meanwhile.
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