3/4 Uq

[Kanguru]

I think this design qualifies as a low tech snugfit.

[hangnout]

Great looking quilt! The differential cut makes attaching and adjusting a breeze.

[GrizzlyAdams]

We've got at least 3 down-filled short underquilt designs floating around now, that differ in the way the chambers are formed.

Figuring out fabric usage is more fun than searching through shoeboxes of receipts (what I should really be doing), so I did some back-of-the-envelope on how much material is used for the different designs.

I'll assume the quilt is 36" wide and 48" long, with a nominal height of 1.5". This makes for 2592 cubic inches. One 3.1 oz bag of Speers 900 fill down fills 2790 cubic inches, which is about 7% over-fill.

"top" here will refer to next to the hammock, "bottom" to the exposed side.

The geometry of all three designs assumes 36x48 for the top piece. Extra fabric for hems on the edges is assumed to be the same for all 3 three designs. If we assume 1" on the long edges, and 1.5" on the head and foot (which take a little more to fold in the chamber ends) we have 420 square inches of fabric that is not involved in chambers, on all designs.

All designs assume 6 chambers running head to foot.

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Design #1

I'll assume the quilt is a rectangular slab 36 x 48 x 1.5.
There are 5 baffles, after sewing 1.5" high, I'll assume using Schneiderlein's hemming foot trick we can attach the edge of a baffle using 0.125 inches, so each baffle is 48 x 1.75 , there are five of them, for a baffle material requirement of 420 sq inches. It is pure coincidence that this figure is the same as for the hemming...I double-checked both figures.

top piece : 36x48 = 1728 sq inches
bottom piece : (2 x 1.5 + 36 ) x 48 = 1872 square inches.
The extra 1.5 on each side forms one side of a chamber wall.

Total :
outside hemming : 420 sq inches
top+bottom : 3600 sq inches
baffles : 420 sq inches

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Design #2

This is the sew-thru version I made. To get 2592/6 = 432 cubic inches / chamber, I need a chamber cross-section of 432/48 = 9 square inches. Assuming a 36/6 = 6" at the top, and a radial model of the bottom side fabric, I need 7.75 inches width per chamber. That makes for 2232 square inches for the bottom piece. The top piece is 36x48= 1728 square inches.

Total:
outside hemming : 420 sq inches
top + bottom : 3960 sq inches

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Design #3

This is Dutch's design. My model for this is a slab 36 x 48 x (5/8)", with the rest of the bottom fabric being radial on top of the slab.

Like the others the top piece is 1728 square inches. Each chamber uses 2 x 0.75" to form the sides, plus the radial bit. I know from my design that the area cross-section of a chamber is 9 square inches. I subtract the slab cross-sectional area of 6" x (5/8)" to get a requirement for the radial part to have area 5.25 square inches. Doing the figuring means the radial width needs to be 6.7 inches.

There are four interior chambers, each uses 0.75+6.7+0.75 = 8.2 inches of width. There are two side chambers, both take 0.75+6.7+(5/8) = 8.075 inches. The width of the bottom piece is thus 4x8.2 + 2x8.075 = 48.95 inches, for a bottom side area of 2349.6 square inches

Total
outside hemming : 420 sq inches
top + bottom : 4077.6 sq inches


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From these numbers one can work out weights, depending on the assumptions made about the fabric used and its weight. On the aggressive side, if I assume 1 oz sq yd for the material (e.g. for momentum-90) and 0.7 sq yard for the baffles (thru-hiker no-seeum), and 3.1 oz of down, and massless thread we have

Design #1 : 6.42 oz
Design #2 : 6.48 oz
Design #3 : 6.57 oz


If instead we're using 1.3 oz DWR we have
Design #1 : 7.36 oz
Design #2 : 7.45 oz
Design #3 : 7.61 oz

Not a lot of difference between designs, and only about 1 oz difference between using 1 oz momentum-90 and 1.3 oz DWR.

The take-home message is that we can make really lightweight summer UQs. Guess we knew that already. What we didn't know was how much impact the various chamber construction methods have on weight.


ok, enough already, back to the shoeboxes

Grizz

[hangnout]

So for every 6 inches on the top there is 7 inches on the bottom.

Should that have been 8" instead of 7"? 5/8+5/8+7? or was it a total of 7"?

[Dutch]

I should have know you would math this all up . I knew there would be a nominal amount of weight with 2 pieces of 1.1 instead of no see um. The actual dimensions of the two pieces of fabric are top- 40 x 52 and the bottom is 54.5 x 52 with hemming included. That makes 4914 sq inches, and that is to make a quilt with 1 inch thick. You had 6.7 between the baffles and Hang out is right with 7. I know you did all kinds of calculations to come up with just the right dimensions for the bottom distance. All I did was make it out of gross grain and hold it around me to make sure the chamber didn't collapse when it had to go around my "radius". My radius use to be tighter but that is another story. So that is really 5/8 + 7 + 3/4 X 2 for the outside baffles and 3/4 + 7 + 3/4 x 4 for the inside baffles. 2" seam allowance for hems all the way around.

What I really took away from it was that to make the baffles the way I did really didn't save me any work. Either you sew the 5 hems or you sew the 5 pieces of bug netting. Although it is pretty cool that you don't see thread on the outside. But only another quilting nut would notice. And because I am anal about my seams I had to iron and pin every baffle before I sewed them at 3/4.

Grizz this brings me to a question that I had for you. I think your quilt is 30 x 48 and it has 3.1 oz of down. I would think that would be about 4 ounces or less for the shell giving you a total of 7.1. Yet you said it came in at 10 ounces. So that means you spandex suspension is about 3 ounces. That seams a little heavy for a piece of spandex that looks 4 x 48 x 2 or 384 sq inches or .296 sq yards. What gives, did you accidentally sew a slide ruler into one of your baffles? I haven't weighed my quilt yet but I expected to come in at least 2 ounces more than yours considering the difference in size.

I did learn that you can get by with a narrower UQ for a bridge than a traditional Speer type. 36" is the bare minimum when the hammock wraps around you. Yet on my bridgeskin it almost goes from edge to edge. Ever since I made my zhammock I have fallen back in love with the traditional Speer type. Don't tell my bridgeskin.

[hangnout]

What I really took away from it was that to make the baffles the way I did really didn't save me any work. Either you sew the 5 hems or you sew the 5 pieces of bug netting. Although it is pretty cool that you don't see thread on the outside. But only another quilting nut would notice

I have had the material to make a summer quilt but have not got around to it. I started planning it out one night and came to the same conclusion you did. Thanks for doing the testing!

I did learn that you can get by with a narrower UQ for a bridge than a traditional Speer type. 36" is the bare minimum when the hammock wraps around you. Yet on my bridgeskin it almost goes from edge to edge. Ever since I made my zhammock I have fallen back in love with the traditional Speer type. Don't tell my bridgeskin

I can relate to this. I made my secound 1/2 UQ for this reason. I needed something bigger than the 36x36 I made for my bridge.

Now to get motivated to make the summer 1/2 UQ!

[GrizzlyAdams]

I should have know you would math this all up .

I am so predictable.

What I really took away from it was that to make the baffles the way I did really didn't save me any work. Either you sew the 5 hems or you sew the 5 pieces of bug netting.

Well you do have to cut the bug netting pieces. But yeah, in the non-sew through designs you end up making two hems to define the edge of a chamber.

Grizz this brings me to a question that I had for you. I think your quilt is 30 x 48 and it has 3.1 oz of down.

Cut 51" long and 35" or 36" wide (I forgit) owing to a) aiming for a usable 32" width and b) extra to roll up into a flat-fell seam with the spandex.

I would think that would be about 4 ounces or less for the shell giving you a total of 7.1. Yet you said it came in at 10 ounces. So that means you spandex suspension is about 3 ounces. That seams a little heavy for a piece of spandex that looks 4 x 48 x 2 or 384 sq inches or .296 sq yards. What gives, did you accidentally sew a slide ruler into one of your baffles?

I was wondering where my slide-rule tie clip got off too...

The DWR I'm using feels heavy compared with some untreated stuff. I'd make it 1.5 oz maybe. The spandex is 6 x 48 x 2, at 2.5 oz / sq yard. That gets us to 9.2 oz. Then there is 48 x 2 inches of bias tape. And thread.

did learn that you can get by with a narrower UQ for a bridge than a traditional Speer type. 36" is the bare minimum when the hammock wraps around you. Yet on my bridgeskin it almost goes from edge to edge.

yep.

Ever since I made my zhammock I have fallen back in love with the traditional Speer type. Don't tell my bridgeskin.

oh how quickly the glory fades....

Grizz

[TiredFeet]

.... I'll assume using Schneiderlein's hemming foot trick .........

Grizz

What is this trick??

[GrizzlyAdams]

What is this trick??

normally when you use a hemming foot to hem an edge there is only one piece of fabric involved.

This very nice trick is to roll-hem the bafflewall piece, aligned with one of the quilt body pieces immediately below the rolled hem that is formed. With one stitch you hem the bafflewall piece and attach it to the one of the quilt body pieces.

if you can use the hemming foot reliably, a feat that escapes me still.

Grizz

[Schneiderlein]

What is this trick??

As Grizz explained, I roll hem the noseeum and attach it to the ripstop in a single pass. I draw a line on the ripstop that is offset such that by keeping this line aligned with the outer edge of the hemming foot, the baffle is attached in the right place. This method requires only a single pin at the start of the seam and makes attaching baffles quick and easy. Here is a picture.

I'll assume using Schneiderlein's hemming foot trick we can attach the edge of a baffle using 0.125 inches

Grizz, it takes a little over 11mm per side with my hemming foot. I just figure 1/2".

if you can use the hemming foot reliably, a feat that escapes me still.

I think I know why you are having a hard time and it is really easy to me. Your rolled hem foot must be for a 1mm seam. I can see where with a narrower seam, you would have a lot more trouble keeping the fabric feeding correctly. I have about 2mm of wiggle room before the needle would only catch one layer of fabric. For you it must be closer to 0.5mm!!! For my machine, there are 2mm, 3mm and 4mm rolled hem feet available from the manufacturer. I have seen generic rolled hem feet for 1/4" (6mm) seams. That's the size I would have preferred, but I ended up buying the 4mm Pfaff foot so it would work with the IDT. Of course, there is a little weight penalty with a wider foot, but I think the ease of operation is worth the fraction of an ounce that one would save.

If you are going to try this method, use noseeum for your practice runs. Sil or 1.1oz DWR are much harder to keep feeding correctly in my experience.