Well, the topic of down sleeping quilts is a bit polarizing. If you want to indulge yourself, there are tons of forum threads discussing it in all detail. In the end it's down to a question of preference. However, I will very briefly explain what it is.
Basically a down quilt is a sleeping bag that is missing the floor section and the hood. The design used most often has a foot box, is open on the side that faces the sleeping pad and has a draw string on top to snuggle it around your neck. With the rise of the ultralight hiking community it got quite a boost in fame. The down feathers only isolate your warmth when they are not compressed. However, the part of your sleeping bag that is underneath you is compressed and thus quite useless. All the isolation provided on this side comes from the sleeping pad. So why not ditch it.
The down side here is that if you toss around and accidentally open a gap, you will loose some of the stored warmth. That's why some of the quilts have attachments, that lock your down quilt to your sleeping pad.
Frankly I wasn't interested because of the weight savings. That's nice too. But I really hate sleeping bags. I like to turn often from side to side. And If it's too hot, I like to let a leg dangle out. Turning in a sleeping bag makes you feel like a spastic maggot jumping around on a sleeping pad. And here comes the real genius of the down quilt. If it's too hot just open a side. You want to turn? Just do it. It won't turn with you, because it's attached to the pad and roomy enough. Too cold? Wear a hat, close all gaps and pull the draw string tight. Short story I really love it.
But... but I already had a down sleeping bag. A good and light one. And I just couldn't justify buying a quilt without ever having the opportunity to try one (nowhere in Switzerland). And I didn't want to throw away my bag. So I thought I could just convert my sleeping bag to a quilt. Planning is easy. But the moment when your scissors rest on the high-tech material of your expensive down bag for the first cut... Priceless!
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(I apologize beforehand for most of the pictures. The sleeping bag is black and looks like a trash bag. This makes it really hard to take meaningful pictures in low light conditions...)
I was heavily inspired by the down quilts of manufacturers like Katabatic Gear, Jacks ‘R’ Better and other DIY enthusiasts that make their own bags. However, I adapted the ideas to my own needs. If you don't want to build one yourself, these are fantastic quilts.
Step 1: Prepare the Sleeping Bag... and Yourself!
First of all: The thin down fibres can be dangerous to your lungs. Wear a dust mask at all times. Work in one room with closed doors and closed windows. Your new best friend is your vacuum cleaner. You can't imagine the power of dissipation of down. It will be everywhere! However, there are technics to limit the disaster to a minimum. You bought a down bag, so why not keep all the down and make your bag even warmer. Since you will cut away the zipper, start at this side and hold the bag with both hands on the zipper. Shake it vigorously so all the down travels to the opposite side. It depends a bit on the construction of your sleeping bag. Mine had down chambers that make the bag look like a maggot. This makes it very easy.
Now you just need:
- Your bag
- A closed room
- Sewing machine
- Dust mask
- Vacuum cleaner
- A lot of needles
- Masking tape
- Optional: Amused girlfriend
Step 2: Time for Scissors
Since your room is prepared for the down apocalypse and all the down is away from the zipper, it's time to start. Mark where you will cut the fabric. Use a lot of needles to join the fabric layers where you will cut. Take out your sewing machine and sew along this line. You will still have some down flying around but much less than if you cut it first and sew it later. Since your sleeping bag is already destroyed, don't be shy to take the scissors. Cut away the material that you sealed with your seam (green part). Now you have the basic form of your quilt that looks as if it's bleeding down feathers. The part that you cut away (green part) you can seal with the masking tape (if you want to keep it) or throw it away directly. I kept the hood to make a down hat later.
Use again a lot of needles to turn your messy seams in and sew them clean. Alternatively you can use an edge band folded over the seam to seal it. I built a small triangle with the fabric that i cut off earlier to make a reinforcement for the place where the foot box ends and the gap begins. If you wriggle around, this place will start to tear apart the soonest.
The seam that will rest against your neck is a bit different. Clean the seams nicely and then fold it again, making a tunnel. Later on you will place a bungee cord through this tunnel.
Step 3: Add Attachment Points
Since I newer had a quilt before and didn't know what I will like, I wanted my quilt to be modular. I sewed 4 velcro patches (furry side) to the sleeping bag. If I won't like the attachments I can simply tear them off. Make sure that you place the attachment points slightly of the seam. Think about how it will lie on the mat (with you inside) when it's attached to the elastic cord. If it's too close to the seams you will have a gap. If it's off a bit, the excess fabric will close this gap.
If it's really cold, you want to be able to close the quilt around your head. You can do this by knotting together the string in the tunnel, or you add two velcro patches or a snap button. If you decide for the velcro, place the furry patch to the outside flap and the hook patch to the inside flap. Like this it won't scratch your neck if left open. Test it before sewing!
To get the elastic cord into the tunnel, just cut off the heads of an ear scoop and attach it to a string. Attach the string again to the elastic cord. Like this you will first fit in the string and later you'll pull the elastic cord with the string. Of course a blunt needle is also an option...
Step 4: Build the Attachment System
Basically you can just as well buy 4 tiny plastic carabiners/snap buckles etc. and attach your quilt with them to the elastic cord on your sleeping pad. I really liked the idea of Katabatic Gear. They use a plastic piece that has two holes - one slightly smaller than the other one - and a slot through them. You can clip the elastic cord into the bigger hole and your quilt is secured to the sleeping pad. However, you can still slide it around on the cord. If you want to fix it in place just, put the elastic cord into the next notch.
I used some scrap kydex (2.5mm thickness) I had from another project, drilled some holes and cut the shape with a saw. Any sturdy plastic will do the trick but it helps if it's slightly flexible. Then I attached the plastic pieces to the velcro hook pads (drilled tiny holes and sewed it tight).
Step 5: Put It All Together... and Use It Often
Take some elastic cord and make two loops that you place around your sleeping pad at the height of your attachment points. It should be a snug fit but not so tight that it deforms your pad. Take your brand new quilt and clip one side to the cord. Step in, lie down and close the other two (if necessary).
This quilt has been with me through New Zealand, South Africa in winter and the desert of Abu Dhabi. And believe it or not, I never ever regretted putting my scissors to it.