3/4 UQ questions

[Schneiderlein]

After finishing my first down quilt, I think I should move the 3/4 under quilt I was planning to the top of my project list instead of the mosquito net hammock (http://www.hammockforums.net/forum/showthread.php?t=3119) that I was going to make next.

My hammock is a simple Speer type hammock with whipped ends. Since I used an under quilt for the first time last night, I have a lot of questions. Any advice would be greatly appreciated.


How wide should I make the quilt?
Should the baffles run length-wise, or accross?
For a quilt about 54"-60" long, will the ends have to be cinched up to make it conform to the hammock?
Should there be a channel for a drawcord suspension along the length of the quilt, so the quilt can be slid into position along the length of the hammock?
Or, would it be better to add loops on the side of the hammock from which to suspend the quilt?
For length-wise baffles, would it be a good idea to put less down on the sides and more in the center chambers?
Has any ultra-lighter figured out a second purpose for a 1/2 or 3/4 UQ aside from a kilt?

I am hoping to come in at around 12-14oz for the quilt with a 3" loft. I use a small 20"x20" sit pad anyway as a pack frame, and I am planning to use it for my feet. Of course, it's always a bit of a compromise between comfort and weight, but I am leaning more towards comfort and plan to make it at least 54" long. The quilt will replace a Thermarest Prolite-4, so between it and the SPE wings I have got 19oz at the moment. Anything under that for the same warmth and more comfort and I'll be happy.

[Just Jeff]

1 - 45-48" wide
2 - Either way works
3 - Yes
4-5 - Either way works. Shockcord running thru the channel probably weighs a bit more than grosgrain loops, if that matters to you.
6 - Yes
7 - Put a headhole and armholes so it'll slip over your front while you're resting, or when you first start hiking in the morning. Your backpack will insulate your back. When you get hot, just take it off w/o removing your backpack and stuff it in a sack. (Probably more trouble than it's worth, though...) Or just use it as a pillow. And maybe a super hero cape (http://www.tothewoods.net/HomemadeGearKidsHammock.html#Quilts).

[warbonnetguy]

1. 40" or wider.

2. people argue for baffells in both directions, so either will work.

3. any conforming to the hammock should be done by the cut of the quilt, simply cinching the edge with shockcord only makes the edge conform to the hammock. this is what creates air gaps between the quilt and hammock and will make it much less efficient and less warm

4. mine is like that, it does a good job of keeping the long edge snug to the hammock, and the ability to slide the quilt towards either end is a big plus.

6. yes, if you are that concerned about weight.

7. it should be plenty long and wide enough to wrap around your upper torso like an indian blanket.

mine come to about 6" past my crotch, i find whatever i put under my knees adds alot of insul, and i use an 1/8"x60" pad doubled over under my legs as well.

good luck with the uq.

[warbonnetguy]

i see me and jeff posted simultaneously.

i found i was able to get a tighter fit having nothing at the ends, i cut them the correct width to begin with so there was no extra fabric to cinch or hang loose. this does seem to be a big factor in avoiding air gaps in the interior of the quilt, but i did end up putting a small (diameter of a nickel) draft tube running across either end to seal it off completely tight. i made them removeable via velcro, but since they weigh practly nothing, i can see leaving them on always for their added effiency they cause.

[Schneiderlein]

JJ and WBG,

your simultaneous posts now have me utterly confused. Maybe there are just so many different ways to do it that all work equally well that finding "the best way" to make a 3/4 UQ is inherently impossible.

My biggest question at the moment is the width. I was thinking an underquilt could be significantly narrower than a top or dual-purpose quilt. WBG's answer seems to indicate that, but JJ says make it pretty much the same width? I am currently using a 20" pad with two 5" wings in an SPE, so I only have 30" of insulated width under me at the moment. Do I really need an extra 15-18", or will an extra 10" suffice? Maybe I should just split the difference and make it 43 1/4".

The second thing I am wondering about is what WBG said about the quilt conforming to the hammock.

3. any conforming to the hammock should be done by the cut of the quilt, simply cinching the edge with shockcord only makes the edge conform to the hammock. this is what creates air gaps between the quilt and hammock and will make it much less efficient and less warm

I assume by "cut of the quilt" you do not simply mean to cut the fabric in a tapered shape, but to actually cut tapered panels to give it a 3D shape? This is an intriguing idea, and since I have a bit of cheap fabric left, I think it might be worth a try. What panel shape did you use on yours? Did you make the bottom of the quilt wider than the top?

JJ, I like the super hero cape idea. My daughter and I had a lot of fun with the down quilt I made yesterday. She likes poking her head through the head hole and then hiding under the quilt saying "You can't find me"...

[Just Jeff]

Yep - part of it is just that there are different ways to do the same thing. The extreme of this (at this point, at least) is the Speer SnugFit - it has a BUNCH of darts so you can't really NOT get a good fit. The JRB has no darts. The Kickass is somewhere in between - not really darts in the bottom, but it's shaped to the hammock b/c there are darts taken out of the sides. That's what WBG is talking about - if you shape it right, you don't need the JRB-style drawcords in the ends.

Re: width, I'd go more than 30". My half-underquilt is 39" wide...it's fine if I'm centered on it and on my back, but if I move around I have to reposition it. So you CAN make it more narrow and it'll work...just a matter of your personal style and how much weight you want to save. My next one will be ~45" wide.

[warbonnetguy]

i meant 40" for a minimum width, like if you are trying to save weight.

by cut, i just mean tapered shape, rather than rectangular/square. for instance, if the shock cord would cinch the end of the quilt to 24" wide, just make your shape 24" wide at that end, otherwise you will end up with a big air pocket right behind the shockcord.

the only darts i use are in the outer shell, this is so the outer shell can be larger as to not compress the insulation. since the uq will have thickness and be curved over the radius of the hammock (mainly side to side/width wise) the outer shell piece needs to be wider to account for this, if not, tensioning it will compress your loft. supposedly, the snug fit has darts on the inside piece as well so it will loft upward filling any air spaces in between the hammock and the uq (maybe youngblood can tell us). i found i could get a flat shape pretty darn snug if it was just the right shape, but like i said, i did add some thin draft tubes at the ends to seal it off completely.

[Youngblood]

i meant 40" for a minimum width, like if you are trying to save weight.

by cut, i just mean tapered shape, rather than rectangular/square. for instance, if the shock cord would cinch the end of the quilt to 24" wide, just make your shape 24" wide at that end, otherwise you will end up with a big air pocket right behind the shockcord.

the only darts i use are in the outer shell, this is so the outer shell can be larger as to not compress the insulation. since the uq will have thickness and be curved over the radius of the hammock (mainly side to side/width wise) the outer shell piece needs to be wider to account for this, if not, tensioning it will compress your loft. supposedly, the snug fit has darts on the inside piece as well so it will loft upward filling any air spaces in between the hammock and the uq (maybe youngblood can tell us). i found i could get a flat shape pretty darn snug if it was just the right shape, but like i said, i did add some thin draft tubes at the ends to seal it off completely.

There is some magic to differential shaping for an underquilt application. When you talk about differential shaping on a curve, or radius, you can have several classes of differential shaping. Most of us are familiar with an exact differential on a radius as shown in the first attached sketch. But there are some interesting properties one can obtain with various types of differential shaping. I have tried to demonstrate some of those that I could define in the second sketch. The SnugFit uses exaggerated differential shaping to allow it to be held snug against the underside of a hammock with minimum sensitivity to compression caused by that contact. That differential shaping is achieved fundamentally by curved baffles along the length of the underquilt and by radially spacing them along the width of the underquilt. To better fit in the crucial tush area and to get more uniform insulation, there are compound curves along both the length and the width as well as variable thickness in the baffles. All this calls for darts to make all that fit together. It gets rather complicated, but that is the general jest of the shaping.

Of course shaping is just part of it, because you still need to hold it up against the bottom of the hammock along as much of the surface as you can. That is where the full width suspension system comes into play.

[skar578]

excuse me, i have to find my rain remnants after youngblood's post.


yea, i have been planning a 1/2 length uq for quite some time, and still sketching plans i hope will be better then the last.

[warbonnetguy]

so, are their darts on the inside shell or is it flat?

ever notice the "negative curve" in a loaded hammock, basically under the knees, the hammock fabric tends to curve upward from the horizontal plane rather than downward like everywhere else. seems like it can curve upward by a couple inches, and can extend quite a ways up toward the suspension. does the snug fit still leave an air pocket under that spot or does it loft inward to fill the void? i felt like this was always the hardest spot to fit the uq to.

i agree about the suspension, never seemed like pull tabs on the corners would do an adequate job of doing that. (i saw the sf at td's, but can't remember the suspension)

[Youngblood]

There are darts on the inside shell but those particular darts are a result of compound differential curves which could have been achieved without darts on the inside shell if I had chosen to put two darts on the outside shell for every one of those darts on the inside shell. If I understand what you are asking, the inside shell is taut and smooth, like the exaggerated differential curve on the sketches I posted as opposed to a reverse differential curve. Your draft stoppers you talked about on one of your underquilts are kind of like a reverse differential curve. Reverse differential curves are good for filling in gaps and are used in the hoods of some sleeping bags.

The "negative curve" can still leave an air pocket with the SnugFit but the full width suspension system helps minimize that and it isn't very noticeable. If the suspension system doesn't pull along the center area of the underquilt, that "negative curve" will be more problematic, particularly if you lay a certain way. I used a net hammock to easily test for that for gathered end hammocks when I was testing the suspension system. When I was testing asymmetrical hammocks I just had to feel around with someone laying in the hammock and it seemed to work fine on them also.

[Youngblood]

Brandon,

When you are using loose fill insulation compared to sheet insulation there are some fundamental differences in what you can do where shaping is concerned. In some ways it is like comparing apples to oranges. They are both fruits... but you can't make orange juice with apples and you can't make apple sauce with oranges.

[hangnout]

ever notice the "negative curve" in a loaded hammock, basically under the knees, the hammock fabric tends to curve upward from the horizontal plane rather than downward like everywhere else. seems like it can curve upward by a couple inches, and can extend quite a ways up toward the suspension. does the snug fit still leave an air pocket under that spot or does it loft inward to fill the void? i felt like this was always the hardest spot to fit the uq to.


Don't you think this is the advantage to the 1/2 UQ? I think it is very easy to get a 1/2 UQ to fit without air pockets and let the pad take care of the legs. Wonder when someone will start selling them?

[warbonnetguy]

Don't you think this is the advantage to the 1/2 UQ? I think it is very easy to get a 1/2 UQ to fit without air pockets and let the pad take care of the legs. Wonder when someone will start selling them?


yes, that along with overall reduced weight (even with a sit pad).

[warbonnetguy]

Brandon,

When you are using loose fill insulation compared to sheet insulation there are some fundamental differences in what you can do where shaping is concerned. In some ways it is like comparing apples to oranges. They are both fruits... but you can't make orange juice with apples and you can't make apple sauce with oranges.

oh, i'm sure, i'm looking forward to making the down version.

[warbonnetguy]

When I was testing asymmetrical hammocks I just had to feel around with someone laying in the hammock and it seemed to work fine on them also.

tell me about it, my fiancee is getting so tired of being my test subject.

[Youngblood]

Don't you think this is the advantage to the 1/2 UQ? I think it is very easy to get a 1/2 UQ to fit without air pockets and let the pad take care of the legs. Wonder when someone will start selling them?

There are all kinds of combinations available to help stay warm over a variety of conditions and it is wise to consider all of those. I have used 3/4 ccf pads in a SPE and used the 10x20 inch pad that I use in my GoLite Breeze backpack in the footpocket on my sleeping bag. That is a very light, inexpensive, and flexible setup for moderate conditions.

Using ccf pads with breathable underquilts extends the range of breathable underquilts dramatically. The ccf pad is also a vapor barrier. A vapor barrier by itself extends the range of a breathable underquilt so you get quite a 'push' when you add a ccf pad that brings its on insulation to the mix along with its vapor barrier.

There are a lot of variables with all of this-- cost, weight, bulk, flexibility, comfort, reliability, easy of setup, durability etc.

[Take-a-knee]

You guys have convinced me to shorten my JRB Nest. I plan to remove two baffles from the slit end. That way, I can tighten up the UQ by moving the velcro if need be without leaving the hammock. I will also be able to mate half of the hennessy slit velcro with the Nest installed. I can use the down from the two baffles to overstuff the torso section. It'll be warmer and weigh less.

[Schneiderlein]

There is some magic to differential shaping for an underquilt application. When you talk about differential shaping on a curve, or radius, you can have several classes of differential shaping. Most of us are familiar with an exact differential on a radius as shown in the first attached sketch. But there are some interesting properties one can obtain with various types of differential shaping. I have tried to demonstrate some of those that I could define in the second sketch. The SnugFit uses exaggerated differential shaping to allow it to be held snug against the underside of a hammock with minimum sensitivity to compression caused by that contact. That differential shaping is achieved fundamentally by curved baffles along the length of the underquilt and by radially spacing them along the width of the underquilt. To better fit in the crucial tush area and to get more uniform insulation, there are compound curves along both the length and the width as well as variable thickness in the baffles. All this calls for darts to make all that fit together. It gets rather complicated, but that is the general jest of the shaping.

Of course shaping is just part of it, because you still need to hold it up against the bottom of the hammock along as much of the surface as you can. That is where the full width suspension system comes into play.

Thanks, Youngblood. The idea of exaggerated differential shaping as you call it had not occurred to me. I will try that.

The problem of designing darts in a quilt to give it a certain shape is extremely complex, and I cannot quite wrap my head around it.

I now have this crazy idea that I want to make a 3/4 length underquilt with exaggerated differential shaping and varying width so I would have 45" of width in the torso section and 24" at the foot and head end. I was thinking I could use six fabric panels that are shaped roughly like an elongated old west coffin to accomplish that.

But trying to imagine the shape of the quilt makes my head explode. Anyway, I'm off to New Mexico to do something easier for the rest of the week, rocket science.

[warbonnetguy]

darts aren't so hard to understand. basically if the shells are different sizes, they will not fit together, there will be extra length on the larger one. the darts make it so the edge of the larger shell will fit onto the edge of the smaller one, they take up the slack.

[Schneiderlein]

darts aren't so hard to understand. basically if the shells are different sizes, they will not fit together, there will be extra length on the larger one. the darts make it so the edge of the larger shell will fit onto the edge of the smaller one, they take up the slack.

The problem I have with darts is that they make things 3D - the fabric does not want to be flat anymore after putting in a dart. It is somewhat hard to visualize that for me.

Part of the problem is that I do not really know what exactly the shape is that I am trying to make the quilt conform to. If it were just a half cylinder, the problem would be easy and no darts would be needed. But there is a roughly conical section at each end. That's why rectangular quilts need to be cinched up. If you put darts in, you can make the quilt conform better to the ends, and it would not have to be cinched up. This should have the additional advantage of the sides in the middle section having less of a tendency to fall away from the hammock.

I was thinking that instead of using darts, one could use a separate fabric panel for each chamber of the quilt. Sort of like an old-style soccer ball or a beach ball. If you have a good idea what the shape you are trying to make is, the panel shape is still pretty easy to work out.

Where I get lost is trying to figure out how the panels would have to be cut for a quilt with different coverage along the length. One cannot simply taper the panels because the quilt will become conical, or at least I think that's what would happen. And that's where my head starts spinning every time I think about it.

I guess Grizz is the math guru here. Maybe he can come up with an equation and a program (hopefully not in perl) to compute the optimal panel design for a given hammock shape. But then again, he doesn't need much of a program to figure it out for his hammock...

Oh, btw, I just arrived in Albuquerque and went to Walmart across from the hotel to pick up some snacks. Of course, I had to stop by the fabric department. Got 10 yards of olive 1.1 ripstop with DWR. There are about 30 yards left, in case anybody is interested. It is the Walmart on Menaul.

[warbonnetguy]

if you want to make a really good one, don't assume it will happen on the first try. you may have to play around with some of those ideas a bit to get them to do what you want.

[GrizzlyAdams]

The problem I have with darts is that they make things 3D - the fabric does not want to be flat anymore after putting in a dart. It is somewhat hard to visualize that for me.

Part of the problem is that I do not really know what exactly the shape is that I am trying to make the quilt conform to. If it were just a half cylinder, the problem would be easy and no darts would be needed. But there is a roughly conical section at each end. That's why rectangular quilts need to be cinched up. If you put darts in, you can make the quilt conform better to the ends, and it would not have to be cinched up. This should have the additional advantage of the sides in the middle section having less of a tendency to fall away from the hammock.

I was thinking that instead of using darts, one could use a separate fabric panel for each chamber of the quilt. Sort of like an old-style soccer ball or a beach ball. If you have a good idea what the shape you are trying to make is, the panel shape is still pretty easy to work out.

Where I get lost is trying to figure out how the panels would have to be cut for a quilt with different coverage along the length. One cannot simply taper the panels because the quilt will become conical, or at least I think that's what would happen. And that's where my head starts spinning every time I think about it.

I guess Grizz is the math guru here. Maybe he can come up with an equation and a program (hopefully not in perl) to compute the optimal panel design for a given hammock shape. But then again, he doesn't need much of a program to figure it out for his hammock...

Oh, btw, I just arrived in Albuquerque and went to Walmart across from the hotel to pick up some snacks. Of course, I had to stop by the fabric department. Got 10 yards of olive 1.1 ripstop with DWR. There are about 30 yards left, in case anybody is interested. It is the Walmart on Menaul.

The separate panels you're thinking of, run across the narrow width of the quilt?

Thinking out loud here, last night I stumbled this old post (http://ultraliteskunkworks.blogspot.com/2007/01/cuben-pertex-quantum-down-quilt.html) by the uberlight guy gardenville, where he made an overquilt of separate chambers and slipped that into a cover. Maybe there's something in that approach to be learned/tried here....if one can figure a way to have the inside hanging from top side of the cover rather than being held up (and compressesd) by the bottom side.

time for more coffee.



darn it. I was in ABQ just 2 weeks ago. I don't normally go cruising Walmarts though when I'm on the road. Usually too busy.

Part of the conforming to a hammock shape thing is solved with the snugfit by using micromesh spandex on the underside. It's a place to start anyway, before diving into the details of differentially cut baffles.

Grizz

[Schneiderlein]

if you want to make a really good one, don't assume it will happen on the first try. you may have to play around with some of those ideas a bit to get them to do what you want.

That's what the $1 fabric is for. Now all I need is time.

[Schneiderlein]

The separate panels you're thinking of, run across the narrow width of the quilt?

Thinking out loud here, last night I stumbled this old post (http://ultraliteskunkworks.blogspot.com/2007/01/cuben-pertex-quantum-down-quilt.html) by the uberlight guy gardenville, where he made an overquilt of separate chambers and slipped that into a cover. Maybe there's something in that approach to be learned/tried here....if one can figure a way to have the inside hanging from top side of the cover rather than being held up (and compressesd) by the bottom side.

time for more coffee.



darn it. I was in ABQ just 2 weeks ago. I don't normally go cruising Walmarts though when I'm on the road. Usually too busy.

Part of the conforming to a hammock shape thing is solved with the snugfit by using micromesh spandex on the underside. It's a place to start anyway, before diving into the details of differentially cut baffles.

Grizz

The panels are supposed to run along the length of a quilt, like a snugfit. Imagine the panels on a beach ball that has a cylinder section inserted at the equator and is cut in half the other way. Only more panels. The problem I have is reducing the width while keeping the radius on the cylinder the same. I think that's only possible if every panel has a different shape, clearly not what I want to do.

The cutting would already be a bit of a pain with all panels the same for each side of the quilt. Anybody have a suggestion for a hot cutting rig that works? I have seen mention of using soldering irons, but no specifics.

Does the micromesh gather the fabric, or do the darts reduce the radius at the end such that no more gathering is needed?

I don't normally go to Walmarts, either, it was pure coincidence. I needed bottled water and a bite to eat, and the Walmart was right there. I may have been to a Walmart twice in the last 3 months. Both times I found fabric.

[GrizzlyAdams]

I can visualize the beach ball, and can imagine the sections being defined as the interiors bounded by vertically oriented planes that contain the straight line between the north and south pole of the beach ball.

So then the cylinder models the human body? With, for example, the longitudinal axis lying in the plane that contains the beach ball's equator? No wait. If the cylinder is the body, then it is oriented the other way, with its longitudinal axis passing through the ball's north and south poles.

And so, (getting to the point at last), the business about changing the radius of the cylinder is really meaning that the geometric solid used to model the human body is not a proper cylinder which one describes with two parameters (radius and height), but is something else. One possible something else you might mean is that along the length of this solid the cross-section is always half a cylinder, but the radius changes with position. Or you might mean that the object isn't actually a cylinder, but something whose surface at any point along the length is described by a radial function r(theta).

makes rocket science look easy :)

my business in ABQ was at Sandia. Far as I know they don't do rocket science, so maybe you were visiting Kirkland. Don't tell, I know, it's a secret.

Grizz

[Schneiderlein]

I can visualize the beach ball, and can imagine the sections being defined as the interiors bounded by vertically oriented planes that contain the straight line between the north and south pole of the beach ball.

So then the cylinder models the human body? With, for example, the longitudinal axis lying in the plane that contains the beach ball's equator? No wait. If the cylinder is the body, then it is oriented the other way, with its longitudinal axis passing through the ball's north and south poles.

And so, (getting to the point at last), the business about changing the radius of the cylinder is really meaning that the geometric solid used to model the human body is not a proper cylinder which one describes with two parameters (radius and height), but is something else. One possible something else you might mean is that along the length of this solid the cross-section is always half a cylinder, but the radius changes with position. Or you might mean that the object isn't actually a cylinder, but something whose surface at any point along the length is described by a radial function r(theta).

makes rocket science look easy :)

my business in ABQ was at Sandia. Far as I know they don't do rocket science, so maybe you were visiting Kirkland. Don't tell, I know, it's a secret.

Grizz

The cylinder model is of course, a very crude approximation using simple geometric primitives. The cross section in not a circle anywhere along the length of the hammock. What I was trying to say is that using several panels of an identical tapered shape will result in a cone, which is probably not really what I want.

Rocket science has many aspects. Sandia has a lot of nice facilities like sled tracks and centrifuges that can be used in the study of rockets. But I guess the common connotation of the term "rocket science" might be rockets that go into space, and not those that are meant to hit an object with great precision.

The beauty of this place is stunning. We worked late outside today, and the sunset colored the mountains in a spectacular red. Makes you think about hiking up those mountains, until you realize there are no trees to hang your hammock from...

[Schneiderlein]

I did a backyard test last night to figure out how a 3/4 UQ would work for me. I took the top quilt (http://www.hammockforums.net/forum/showpost.php?p=50699&postcount=23) I made and doubled it over like Grizz did in his test (http://www.hammockforums.net/forum/showpost.php?p=43251&postcount=31). This gave me a rectangle of nominally 40"x50", but I measured 38"x49". I attached the quilt at the ends using shock cord. The shock cord was attached to the ridgeline using a Prusik knot, then looped through the quilt pull tabs and secured with a taut line hitch for adjustment. I attached the quilt so the baffles ran the long way, i.e., I had 49" of quilt going the long way, and ~38" across.

It was in the mid 40s when I got in the hammock and I didn't really think it was going to be a real test. I was wearing a cotton T, light weight fleece top and pants. When I got in the hammock, I was immediately warm. Not warm like with a pad, I was surrounded by warmth, and I had not even put the top quilt over me! I was thinking that I might not even need the sit pad for the feet, but after about 10 minutes I was proven wrong in that regard.

I felt all around the bottom to see how well the quilt fit and if the down was compressed. There was slight compression under my butt, and a very poor fit at the head end. I think I probably lost 6-8" of insulated length due to the poor fit at the head end. But I was warm so I did not bother making any adjustments. I put my 5osy Climashield XP top quilt over me and fell asleep. The birds woke me up at 5:45am, and I was warm, but had a bit of a cool spot on my right shoulder. I felt outside the hammock and noticed that my shoulder was right at the edge of the under quilt. I noticed a lot of condensation on top of my top quilt, but I felt no condensation on the bottom quilt. I got out of the hammock and it was coooold. The temperature had dropped to 34 degrees, and the humidity was at 90%.

Lessons learned:

3.5" of down loft under you keep you very warm in near freezing temps.
50" length appears to be sufficient, particularly when considering the ill fit at the top.
38" width would work for the ultra-light crowd, but I will add a little more width.
I definitely need a pad for the legs, but I carry a sit pad anyway.

I am now convinced that the 3/4 length UQ is definitely worth pursuing. As soon as I find some time and a hot knife I will make a prototype. The quilt will be tapered at the head and foot end with baffles running the long way. I will try the exaggerated differential shaping design suggested by Youngblood.

[Schneiderlein]

I have started construction of a 3/4 UQ based on some of the ideas Youngblood and warbonnetguy put in my head. My hope is that the quilt will conform to the hammock much better than a rectangular quilt. To accomplish this, I have constructed both the inner and outer shell from seven panels each that are joined with French seams. For those counting grams, the weight penalty for doing this is roughly 0.8oz vs. using a single piece of fabric.

To make the pattern for the panels, I started out by drawing the width distribution that I wanted: 28" at the head end, 45" at the shoulders and 30" at the foot end, and essentially divided this distribution by 7 to arrive at the shape for each panel. I figured joining panels shaped like that should give me somewhat of a canoe shape. I wrote a little program to fit a B-spline to the panel shape. The program then extended the inner panel along its normal direction to add a 3/4" seam allowance for the French seams and also computed the shape of the panels for the outer shell. The quilt was supposed to have 3" loft, and I figured to split the nominal down volume between a baffle height of 1.9" and additional fabric width to accomplish the exaggerated differential shaping suggested by Youngblood. So the program computed the extra width required for the outer panels to achieve a volume equivalent to 3" loft. The program then matched the seam lengths of the inner and outer panels to the baffle. Throughout the program, I made extensive use of various approximations based the work of a famous 18th century Taylor. I won't bore you with all the details. To make a long story short, the program wrote a file that I took to Kinko's to get a print out of the template. I have attached an image of the template to this message. I will make the original pdf file available if this quilt actually works and there is interest.

So far, I have cut the panels and baffles with a hot knife. This took about 2h including setup and cleanup. I have joined the inner and outer panels with French seams, which took about 45min each. I am encouraged by the shape the fabric takes on if you hold on to the four corners. It actually does resemble the shape of a hammock. Unfortunately, I have had the flu for the past few days and have not been able to do much. I am feeling a little better today, but not well enough to go to work. With nothing else to do, I thought I'd post about my quilt.

[Schneiderlein]

I have finished the 3/4 underquilt aside from the pull tabs. The first photo shows the side of the quilt that goes against the hammock, the second one the underside.
http://www.hammockforums.net/gallery/files/1/0/6/9/uq_top_side.jpghttp://www.hammockforums.net/gallery/files/1/0/6/9/uq_bottom_side.jpg
The quilt has 26.5" insulated width at the top end and 43.5" insulated width at the widest point. The quilt is 51" insulated length. It is filled with 7.5oz of Speer down. I have not weighed it, but it should come in at about 14.5oz if my calculations are not too far off.

In the pictures, the quilt looks narrower than it really is because it is flat. As soon as you pick up the ends of the quilt, it takes on a hammock shape. Pulling on the sides only tightens the fabric layer that goes against the hammock, and does not compress the down at all. I am pretty excited about it and I think it will conform to the hammock very well.

My initial idea for the suspension system was to put four or five tabs along each of the long sides and run shock cord through them, sort of like warbonnetguy does with his quilt. I am now thinking that that may not be necessary and I can get away with just four corner tabs. I will start with that and hopefully get it under my hammock for a first test tonight. Unfortunately, the forecast low is 48 F, and there might be some thunderstorms coming our way. I'll try to get some pictures of the quilt under the hammock if it doesn't rain. My wife has agreed to help with this, but I am sure she does not want to get wet in the process.

[slowhike]

hey, that looks great! keep us filled in on how she preforms.

[Dutch]

Looks great. How much loft do you get? It looks like it it sewn through rather than have baffles. I'm planning on starting some quilting projects soon and a 1/2 or 3/4 is definately on the menu. Again really good work.

[Schneiderlein]

Looks great. How much loft do you get? It looks like it it sewn through rather than have baffles. I'm planning on starting some quilting projects soon and a 1/2 or 3/4 is definately on the menu. Again really good work.

Thanks for the compliments. The quilt only looks sewn through when you look at the under side. I made the panels for the underside larger so that the down would not get compressed when pulling on the sides of the quilt. It is based on a drawing by Youngblood earlier in this thread, and is what he used for the Speer Snugfit.

The quilt is baffled to 1.9". Half an inch of that comes from the French seams that the panels are joined with. The rest is noseeum netting which is attached to the inside of the French seams. I wanted to have a quilt with 3" loft. I figured I would split that between the baffles and having wider panels at the bottom. The width of each down chamber varies along the length of the quilt. So, for a given width W, I knew I wanted to have an area of A=3"xW, and I already had 1.9"xW from the baffle. I then computed the additional width of the bottom panel that would be required to make up for the missing 1.1"xW assuming a parabolic shape of the panel. It turns out that the narrower the panel, the more extra width is required. I thought I could use this to my advantage and simply widened the bottom panels by the average widening required to get to the 3" loft. This would put more cross-sectional area in the wider parts of the panels and less at the ends.

I think my theories worked out pretty well, except that the quilt seems to be overstuffed by much more than I calculated. I had figured the 7.5oz down would be only 11.5% more than required. I think I made too many approximations or bad assumptions, and could have easily saved 1oz or more of down.

I guess if it doesn't get any colder, the first thing I will be testing is how well the quilt can be vented. :)

[Cannibal]

That does look sweet! I've been going through some rough weather (cold/wet/windy) and have been thrilled with the torso UQ concept. Stayed warm in a cloud last night. Really, I was sleeping in a cloud. :eek:

Heaven is a lot colder than I thought it would be. :D

[Dutch]

That is some incredible loft for 7.5 oz of down. Speer's down must be incredable. You understood youngblood much better than I did. I have to go back and look at that.

[slowhike]

That does look sweet! I've been going through some rough weather (cold/wet/windy) and have been thrilled with the torso UQ concept. Stayed warm in a cloud last night. Really, I was sleeping in a cloud. :eek:

Heaven is a lot colder than I thought it would be. :D

good to see you checking in on us<g>.
i was wondering how you guys were making out w/ some of the storm systems that have been moving through the south east.
guess i better catch up on reading your trail journals.

[Schneiderlein]

That is some incredible loft for 7.5 oz of down. Speer's down must be incredable. You understood youngblood much better than I did. I have to go back and look at that.

I am really happy with the Speer down. The loft is not really all that incredible if you consider the size of the quilt. It would be about equivalent to a full-size quilt with 15oz of down.

[Schneiderlein]

Quick update: I have used the quilt for the first time. I was wearing lightweight fleece pants, cotton T-shirt and lightweight fleece top. I hung the quilt from four corner pull tabs using shockcord over the ridgeline. I got in the hammock and was immediately hot. First, the pants came off, then the socks, fleece top and finally the T-shirt. I was still hot. I finally adjusted the quilt to create an air gap and was comfortable for the rest of the night. The temperature was about 50 F.

The coverage of the quilt is really great. It comes up over my shoulders by a good amount on each side and it is plenty long with the addition of the sit pad. The suspension, however, is something I need to work on. I currently have a piece of shockcord with a Prusik knot on the ridgeline. The ends of the shockcord are looped through the pull-tabs and secured with a tautline hitch. The tautline hitches let me adjust how tightly the quilt is held against the hammock, and the Prusik knots adjust how much longitudinal tension the quilt has.

The good news is that I can hang the quilt very loosely before getting air gaps at the ends. The quilt conforms very nicely to the hammock at the ends with minimal tension.

The bad news is that the sides of the quilt will fall away from the hammock unless I put a bit of longitudinal tension on the quilt. However, doing so leads to some down compression under my butt.

I did hang the quilt with no longitudinal tension and then grabbed both sides of the quilt in my left hand at about chest level while feeling for down compression with my right hand. I did not notice any compression in this configuration, even though the sides of the quilt were pulled very tightly since I essentially closed the quilt around me. So, one additional pull tab at chest level should be all that's needed to pull the sides of the quilt against the hammock while avoiding all compression. But I don't want to have another piece of cord over the ridgeline.

So, I think I will try the original plan of adding two more pull tabs on each side and running cord through the tabs on each side like warbonnetguy.

Unfortunately, no pictures yet. It was already dark when I set up, and my wife left too early in the morning to take pictures.

[warbonnetguy]

cool, sounds like a pretty good fit, you know it's a good design when it makes you hot. what i recommended was to sew a drawcord sleeve/channel on the sides and run the sc through that, just running it through pull tabs might not have the same effect. if it's not too big of an opening, it might work , but a drawcord sleeve is not much if any heavier, and would probably perform better as it would pull the whole side snug, rather than just at the pull tab points.

lets see some pics of it in action.

[froldt]

I was wearing lightweight fleece pants, cotton T-shirt and lightweight fleece top. ... First, the pants came off, then the socks, fleece top and finally the T-shirt.

Unfortunately, no pictures yet.

I have to admit that I'm glad there are no pictures yet! I dunno that I want to see someone (besides my fiance) naked in their hammock! :eek:

However, I'm glad that it worked so well for you and especially that you've figured out a possible solution to your problem! :D

[Schneiderlein]

cool, sounds like a pretty good fit, you know it's a good design when it makes you hot. what i recommended was to sew a drawcord sleeve/channel on the sides and run the sc through that, just running it through pull tabs might not have the same effect. if it's not too big of an opening, it might work , but a drawcord sleeve is not much if any heavier, and would probably perform better as it would pull the whole side snug, rather than just at the pull tab points.

lets see some pics of it in action.

Yeah, the friction in the channel would also keep it in place, while the pull tabs might not. I will have to play with it for a bit to figure out the best way. I think I might fix one end and put a cord lock on the other, or something... I might end up sewing a separate shock cord channel to the side of the quilt.

I have to order some more shockcord. I also want to try the linelocs from quest to see if they work with the thin shockcord for an easier adjustment.

[GrizzlyAdams]

nice quilt. Once I'm done with my light-weight bridge hammock I'll be working on a light weight 1/2 UQ for it, something to take me to about 50 degrees. Glad I don't have to mess with warped geometry.



I have to order some more shockcord. I also want to try the linelocs from quest to see if they work with the thin shockcord for an easier adjustment.

answer : yes. Both the big ones and little ones work swimmingly. Nice strong springs inside 'em.

Grizz

[Schneiderlein]

answer : yes. Both the big ones and little ones work swimmingly. Nice strong springs inside 'em.

Grizz

I was thinking about the Tent Guy Line Adjusters - Lineloc 3 at the bottom of this page (http://www.questoutfitters.com/tent_poles.htm). I don't think they have any springs. Are you talking about the same ones?

[GrizzlyAdams]

I was thinking about the Tent Guy Line Adjusters - Lineloc 3 at the bottom of this page (http://www.questoutfitters.com/tent_poles.htm). I don't think they have any springs. Are you talking about the same ones?

No I was thinking of something else. Not called linelocs at all, called toggles.

The 70's weren't good to me.... ;)

Grizz

[Schneiderlein]

I have not had a lot of time for fun things lately, so no pics yet. When the weatherman predicted freezing temperatures for last night, I had to do a back yard test with the new 3/4 UQ. I was wearing smartwool and light weight fleece, both top and bottom, and a wool hat. I used my summer quilt with about 1.75" loft on top, 3/4 UQ and sit pad for bottom insulation. Around 1am, I woke up sweating a little bit. I did not remove any clothing though, because it was already below freezing and I thought I would get cold. I vented a little bit and fell asleep again. I woke up at 7am and it was 28F but I was warm, particularly on the bottom. I did not want to get out of the hammock.

I did manage to adjust the suspension to get rid of the down compression at the bottom while keeping the sides of the quilt close to the hammock. I guess it just takes a little while to get it just right.

I am pretty thrilled about this result. 28F is not bad at all for a 14.5oz underquilt, and I think I can go quite a bit lower (with a different top quilt).

One curious thing: The last two times out in the hammock, I have noticed moisture on the outside of the foot box of the top quilt. One time with the synthetic, and last night with the down quilt. The first time I thought I brushed the quilt against the tarp which had a lot of condensation on it. Last night, the tarp stayed dry, and now I don't know what to make of it. Anybody experience condensation in the foot box area of their top quilts?

[GrizzlyAdams]

really sweaty feet (?)

GRizz

[angrysparrow]

really sweaty feet (?)

I have a set of the Really Sweaty Feet™ that I take with me on occasion (a matched pair, actually), but I've never experienced condensation when using them submerged in a quilt environment. ;)

[Schneiderlein]

I thought about that, but the condensation is on the outside. The only explanation I have left is that it was a mean squirrel peeing in my hammock. I can picture him walking along the suspension, doing his business and taking off with a grin...

[warbonnetguy]

i've had condensation on my entire down sleeping bag before, seems like it's always below freezing, maybe since you were hot, and it was cold out, you were putting off more water vapor than the cold air could absorb, so it condensed on the shell of the quilt.

[Schneiderlein]

There was actually a little bit of condensation at the head end of the quilt as well. I figured that was from my breath, and it was only a very slight dampness. The footbox had much more moisture on it. The first night this happened was not below freezing, but it was foggy. The second time it was cold but not humid at all. I'm still puzzled. Could it have anything to do with the CCF pad under my feet?

[Cannibal]

I get a light sheen of condensation on my topquilt every night it dips below freezing (which is every night!). I figured it was due to the bug netting restricting airflow. I've started leaving the zipper open about 9 or 10" and haven't had any problems since.