Differential underquilt vs. Non-differential UQ

**MondayHopscotch** · 03-25-2010, 19:35

just for clarification, what does 'differential' mean? I have some educated guesses based on reading around, but none of them have been confirmed yet.

**Trooper** · 03-25-2010, 20:07

Originally Posted by MondayHopscotch

just for clarification, what does 'differential' mean? I have some educated guesses based on reading around, but none of them have been confirmed yet.

...and perhaps an example of each?

**SlowBro** · 03-25-2010, 20:31

Originally Posted by MondayHopscotch

just for clarification, what does 'differential' mean? I have some educated guesses based on reading around, but none of them have been confirmed yet.

A differential quilt is one that is fitted in 3 dimensions. The inside will be snug and generally smaller to fit right up against the hammock and the outside fabric will be bigger and have room to expand. If you make a non differential quilt the both sides are the same size. This is easier to cut out and maybe even to sew, but then when you strap it to the quilt it will compress the insulation whereas a the differential quilt won't have much if any compression.

**slowhike** · 03-25-2010, 21:52

I voted maybe just because on those really warm trips you might need something by morn, but not much.
But for colder weather, I think the differential cut is the way to go!

**slowhike** · 03-25-2010, 21:57

Originally Posted by MondayHopscotch

just for clarification, what does 'differential' mean? I have some educated guesses based on reading around, but none of them have been confirmed yet.

Here's a drawing I did while designing a differential cut underquilt I never got around to making

Note, this was drawn before the first underquilt was introduced.

You can see the difference in the measurements of the shell & the lining.

**Just Jeff** · 03-25-2010, 22:37

That's a good drawing by slowhike. Also, look at the picture on the JRB MWUQ4 page of them stretching the quilt out tight...and there's still no compression of the down. That's the advantage of a differential quilt...you can snug it up tight to the hammock and none of the down will be compressed. Warbonnet Yetis are also differentially cut. KAQs are differential synthetic versions.

A non-diff quilt is generally a flat quilt...it's two pieces of the same size of shell material sewn together. Like the Nest and no Sniveler.

Differential quilts usually have shaped baffles as well, whereas a flat quilt's baffles will generally be rectangles of mesh. The diff's baffles might be shaped like a flattened-out "U", with wider U's at the shoulders and narrower U's at the knees.

**MondayHopscotch** · 03-25-2010, 23:45

Thanks for confirming

And I was planning on doing that for my UQ anyhow, just didn't know what it was called.

It doesn't seem too much more complicated to sew especially in the case of synthetic stuff such as insultex (which is what i'm going to be using)

**HappyCamper** · 03-26-2010, 06:46

Great info from Slowhike and Jeff. I think the differential cut is very important for an UQ and might be something easily overlooked by someone new making or buying an UQ. I know I'm much warmer since I went to the d. cut because now I just snug it up tight against the bottom of the hammock and forget about it.

I wanted to do a poll to get a visual on what others thought so it would give new people an instant impression on what they should be thinking about before they make an expensive purchase or DIY underquilt. The poll bears out what I have always felt about the d-cut. That it's important. And the fact that I think all the cottage makers offer a d-cut now. But JustJeff and Grizz make an important point about dual use and that's something to consider too.

As far as my own dual use experience . . . I started out with the NoSniv as an underquilt, but I wasn't very consistent in how I hung it and some nights I would be cold when it just didn't make sense that I was cold. Later I got my first d-cut uq and I find that I get a more consistent temp due to the fact that I'm not worried about snugging it up too tight. I now use the NoSniv as a topquilt and am very satisfied using it that way. So dual use for me for a non d-cut quilt means a top quilt that I can wear. I still make sure my UQ is differential.

**Peter_pan** · 03-26-2010, 08:38

Originally Posted by Just Jeff

That's a good drawing by slowhike. Also, look at the picture on the JRB MWUQ4 page of them stretching the quilt out tight...and there's still no compression of the down. That's the advantage of a differential quilt...you can snug it up tight to the hammock and none of the down will be compressed. Warbonnet Yetis are also differentially cut. KAQs are differential synthetic versions.

A non-diff quilt is generally a flat quilt...it's two pieces of the same size of shell material sewn together. Like the Nest and no Sniveler.

Differential quilts usually have shaped baffles as well, whereas a flat quilt's baffles will generally be rectangles of mesh. The diff's baffles might be shaped like a flattened-out "U", with wider U's at the shoulders and narrower U's at the knees.

JJ, et al,

The real benefit is not the differential cut, though that is important, it is the body contouring radial baffles... The only UQs with radial or contoured baffles are the JRB Mt Washinton Series and the Speer Snugfits...All the other differentially cut UQ have staight baffles...If another has added curved baffles they may want add a comment, but I've not seen this detail preveously posted anywhere.

It is also fair to note that three season flat quilts are excptional performers as TQ and above 30* are also more than adequate as UQ... Thus for those seeking the multifunctionality of TQ or UQ they offer excellent capability often at lower cost and thus may be the value alternative.

The true value of Differential Design AND Shaped Baffles is in increased constancy of loft for temps below freezing and this value increases as the temperature drops... FWIW, this is the reason that the JRB Mt Washington 4, a true zero degree UQ, was introduced before the three season Mt Washington 3. This is also why the JRB Mt Washinton 3 and the Speer Snugfit both perform well at 20* for three season UQs, which is a good 10* below the previous 30* range of three season flat UQs.

Pan

**wisenber** · 03-28-2010, 12:47

I've got a No Sniveler and an Old Rag Mtn and use gathered end hammocks. I like the flexibility of rectangular quilts with draw stings, omni tape and tie offs. I can use them as a TQ or UQ (and of course the No Sniveler can be worn). When I expect temps well below 20F, either of those quilts makes an awesome booster for my Peapod.

I've got a "fractional quilt" as well. I like it fine when it's not terribly cold, but I do like the 48 inches of width for shoulder coverage.

A differential cut UQ is fine, but it only works well as an UQ. The one thing I don't like about a rectangular flat quilt is that it gives me to many choices to make before I pack my gear.