Poly Tube Down Air Mattress (DAM) First Generation

"I kept a silk tube of Down hanging over a bedroom door and would play with it several times a week to see if I could get the Down to leak through the silk tube. I never had a problem with losing the Down…I hand pack my Down into the tubes so I got to see up close what the Down looked like. I touched most of it as I packed my silk tubes."

Bill, I used Thru-Hiker 800 FP down, hand-packed, and like yours it was exceptional quality, no pinfeathers, what I call "dandelion puff." Given that I also used 8mm silk, but experienced significant leakage, I have to assume that:
1) Our silks were of completely different weaves or densities or 2) You weren't stuffing the tubes as tightly as you could in your hands. Given your very high quality of work, I suspect that the difference is in the quality or type of silk.

Do you think that is a fair conclusion? What type of 8mm silk did you use?

Thanks for setting up this thread. I had read the earlier post with interest, look forward to hearing more.

Hi Brad,

I was using 8mm Habotai # 026L-000 from Thai-Silks and unless the quality changes over time should have been the same as yours.

I just got off the phone with Thai-Silks. Asked about any differences in the 8mm over the last few years. Was told that there should have been no difference in what I bought back in 2003 or any that I have bought since to include yours. Yours should be the same as mine was.

I have bought both dyed and white silk in 8mm. The white is washed and then dyed in a hot water dye bath. The person I was talking to said that if you had the pre-dyed it is also washed and dyed in a similar way as I do it. If you used white silk and it was not washed first it might not be as tight a weave as the washing and dying will cause the material to shrink a bit.

I think my Down silk tubes were about 78 inches long and had 1 ounce of Down in each. This gave me a loft of about 4 inches per silk Down tube.

Hi Bill. good to see you and thanks for starting this thread.

>I need to find my pictures that didn't make it to the Blog and re-write the whole Poly Tube DAM Thread.

Looking forward to it.

Bill, please could you tell me the thickness of the plastic tube? You said "2 mil" but I wonder what this equates to. Over here in the UK I can get "250" and "500" guage polythene, which I think is 0.25 and 0.5mm. In our eclectic mix of units. it comes in 4" and 6" flat tube, but not 5" as you used. Should I go narrower or wider than 5" in your opinion?

Huzefa said on his other thread that he found the tubes burst when he sat on them, and you asked if he'd overheated the sealing process. I was wondering if he meant the side seams because he tested them without constraining them in a cloth tube first.

I have some 1.1oz parachute nylon. Is this suitable do you think?

Rog, what I was using was actually a double sheet -in other words it was 3 feet wide tube. I dont remember what guage it was but when I asked for 2 mil sheet they didnt understand.

I cut the sheet into 1 feet lenght and I sealed the two open (3feet long) side with iron. It just didnt seal properly. I could see lot of air pockets in the seam. When I sat on it didnt burst. The seams just opened as if I was using glue!

Hi Rog and Huzefa,

2 mil is equal to 0.002″ or 0.0508 mm. I would guess that the 3 mil tubing I have is then equal to 0.003″ etc.

Conversion Utility

When this material is made it is extruded as one long continuous piece and has no seams. That way the only seam is the one you put on the ends of the tube. I tied a knot in the ends and that worked Ok but the knot was hard to take out after laying on the tube all night.

Poly Tube Link

I have some 4″ poly Tubing and believe it was to small. I would go to 6″. My 3 mil is 6″ but I haven’t tried any of it yet.

Rog, Are you asking about the 1.1oz parachute nylon for shell material. The shell material I used was just some $1 a yard “on-sale” material from my local Wal Mart. For the shell I would expect it would do fine. Do some test sewing first to make sure the seams hold. Try a long stitch lenght so you don’t have a perforated line that could pull apart easy.

My guess is if you can identify what is sold in the UK with the stuff from the web site someone will have it.

I think Huzefa explained why or what happened with his “home-made” tubes. The Poly Tubes I use are very strong. I did many bounce tests and never popped a tube.

Thanks for the clarifications Bill. I'll cast around and see what I can find. I'm amazed at 0.002" though, you sure it's not .020" i.e. 0.5mm ?

Rog,

I called the company this morning and that is what they told me.

It looks to be about as thick as a piece of cheap printer paper.

Poly/Nylon tubes may work better. You can get various widths. This can be dual purpose for you also if the design doesn't work since this is what food vacuum bags are made from.

The nylon is a oxygen barrier and its going to give you both better durability and less stretch. In theory the nylon is going to feel like it gives up less air over time partially because its not… due to the barrier and also because its not going to stretch under weight as much.

Like the poly stuff you can seal it with a foodsaver or the like. I use an impulse sealer from Harbor Freight.

You can probably use bike presto stems to fill. I make various vacuum related tools using normal auto valve stems and caps.

Hi Bill and all-
I'm truly and completely stumped on the silk tube bit. The silk I used was the exact same stuff, 8mm Habotai from Thai Silks. What I was doing to establish down-proofness was taking my little "pillows," making a fist with one hand, and stuffing the pillows into my fist with my free hand. After 10+ iterations of that, I'd find roughly five teeny puffs poking out… and I do mean teeny. The stuff coming through was the finest, fluffiest bits of down, jutting out anywhere from 1/16" to an inch. Realistically speaking, pulling down back in on such a regular basis wouldn't work for me.

For the DAM-ish project here, I can see where perhaps the down-proofness isn't as significant of a concern, since the tubes are ensconced in a non-porous tube. But what if they were used in a stand-alone fashion, such as doubling as insulation tubes in a silk-shelled down jacket?

Admitting my ignorance, I don't understand the silk "mm" designation very well. How does or could that relate to, say, thread count?

I do really like the DAM concept; been thinking about buying an Exped one, but if I could make it… As I've confessed elsewhere, I'm no SULer, and I do enjoy my comfort, especially in bed. I'd love to make one of these DAMs at about 4.5->5 feet long and 26 inches wide…

Pictures

1. Plastic Clips

2. Popsicle Stick Clips

3. Shell for Poly Tubes

4. Warmlite DAM

5. Making and filling the Silk Tubes with Down.
pg 25

Bill

Have you thought of turning this into an MYOG article for BPL? I can help if needed.

Cheers
Roger Caffin

> I don't understand the silk "mm" designation very well.

mm = 'momme' for silk. Google definition.

Momme
" A Japanese weight equal to 3.75 grams which is applied to a piece of fabric measuring 25 yards by 1.49 inches, an area of 1.035 square yards: thus a 1-momme silk weighs 3.62 grams per square yard." (Howitt). Or, an 8-momme silk would weigh about 1 ounce per square yard. Habutai for example, is woven from 2.5 to 60 momme, with the China Silk class commonly in 8 to 14 momme range. Abbreviated as mm.

* Howitt, F.O. "Bibliography of the Technical Literature on Silk", New York: Hutchinson's Scientific and Technical Publication, 1946. (Discusses research published in magazines articles and books.)

All the above was taken from my copy of the book – "A Silk Workers Notebook" by Cheryl Kolander, Aurora Silk, Portland, Oregon 97217.

Hi Bill,

I think I had mixed up the 0.57 oz weight you posted for 4.5mm silk with the weight of 8mm silk. So I was under the impression that silk you were using was much lighter.

Now I dont see any significant weight saving over momentum baffles.. I guess the advantage is in the cost. silk is much cheaper compared to momentum.

Huzefa,

Back in 2003 / 2004 there was no Momentum 90 being sold and I had no contact to buy anything except stuff that was heavier than the 8 mm silk.

The world has moved on since back then and if I was to start over with a Version Two, today, I would have a completely different set of materials to work with. I expect I would also go with a synthetic insulation such as the new 0.92 CLO Primaloft One insulation and may not even use Down.

Bill,

Using the new primaloft one is a good idea. I had completely forgotten about it.

Synthetic air pad would be easier to make. But it wouldnt be as warm or thick as DAM. I think so because synthetic doesnt loft as much as down so you if you have a pad as thick as DAM you will need a lot more insulation to fill the space.

btw, any news on when the new primaloft will be shipping to the retailers?

Looks like I'll probably buy that book Bill cited. In the iterim, I do and have understood the bit about 8mm weighing about an ounce per yard. What I don't know is if that in any way translates to the actual density of the weave, or "thread count," if there's a way to correlate… Understanding that much synthetic fabric used now, such as the Momentum, weighs about an ounce per yard and is downproof, that synthetic fabric is also callenderized, no? I've said it before, and I'll say it again (please pardon the cliche)– the BPL community is truly awesome. The vast amounts of knowledge pooled here… wow.

Regarding the DAM–Bill, thanks for the pics, my computer seems to be taking all day to download right now?– I'm slightly confused about the poly tubes. I mean, they're cylindrical tubes, right? So when combined/added to their baffled "containment device," is there not still a sewn-thru jacket reduction in insulation between tubes? If so, is that a practical concern? And if it is, is there a way around it? Has anyone looked at playing with a laminating machine and just some single-layer poly? (I ask having read all the preceding, including Hufeza's experimentation…)

-Photos finally came up, computer was just acting up. That looks great! (And partially answered my above questions.)
Cheers, all!

I did some calculations and the numbers are very exciting.

Assuming the new pl1 will also come in 6 oz weight, it will have a total clo value 0.92 x 6 = 5.52

Rvalue = clo value/1.136 = 4.86

I think that should be warm pass 0F.

Now the weight of the pad:
pl1 – 6oz sqyd
two layer of momentum – 2.1oz sqyd (1.05 x 2)
two layer of 2mil poly – 2.8oz sqyd (1.4oz x 2)

Total 10.9oz sqyd

A 20" x 48" will weight about 8 oz, not counting the weight of valve, thread, adhesive, seam allowance etc.

Thats really cool!

The idea is basically to quilt pl1 sandwiched between two layers of momentum. Then glue a sheet of poly on each side of the quilted pl1. Allow it to loft fully and heat seal the sides and add a valve.

I think the construction idea in my above post could also be used in DAM. Glue a sheet of poly on each side of a 20"x 40" Down quilt and heat seal the sides. The strenght of the stiched seams, especially those of baffle walls will keep the pad from ballooning. What do you think, Bill?

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Cool Bill, you decided to post it all up in one place. I like it. This project has always intrigued me, mainly because it shows how to make something that I had previously deemed must be purchased from a manufacturer. One of my goals is to make everything on my backpacking gear list. So, this helps a lot.

Rog, aren’t these crazy yankee units confusing? When I started working as an engineer out of college, everyone was throwing around this “mil” stuff. I originally thought they meant millimeters. No, I was wrong, 1 mil is 1 thousandth of an inch. It is usually how they classify plastic sheeting thicknesses. What is really confusing is when people (like my boss) throw around and interchange measurements. For example..”Let’s make that 3 mil, no, on second thought, how about 4 thousandths.” And then, instead of saying a hundredth of an inch, it is 10 thousandths, or 10 mil. So, sometimes, I have to clarify and say, “so you want it .01 inches, right”. I will get used to it someday, and confuse the new guys as well.

Huzefa, your sealing description sounds like you didn’t apply enough heat and pressure. When I use the impulse sealer at work to seal any plastic, I usually have to mess around with the heat setting until I get it right. The impulse sealer also requires me to apply pressure. Our automated heat sealer uses a pneumatic ram to apply even pressure for a good seal. Also, what do you use to separate the metal on the iron from the plastic, and the plastic from the surface you are pushing on? Impulse sealers have a layer of fiberglass tape coated with Teflon between the heating element and the plastic. They also have a piece of silicon foam on the other side to apply even pressure.

Eric, have you tried sealing presto valves to LDPE? I am sure you can, I am just interested in how you did it?