Friday, 4 October 2013

MYOG Synthetic Quilt

Awhile ago I built a down quilt with a central zip that allowed the user access to the filling. The idea was that the user could replace the filling quickly and without any sewing. I suggested that a quilt built this way would also allow alternative fillings to be used for each specific trip. Perhaps a down filling for a lightweight summer hike or more water resistant synthetic filling for a kayaking trip. This idea was fine except that for the filling to be quickly swappable it would have to be contained in some kind of additional skin that could be inserted and removed from the shell. This added extra weight that I'm not prepared to carry so I inserted my filling directly into the shell and decided to build a second, fully synthetic, quilt with swappable fillings. As most synthetic fill comes as a continuous sheet then no container would be needed. Imagine, 1 shell with 2 or 3 different fillings that could cover all conditions. Sound useful? I thought so!

Finished quilt with 8oz Apex insulation

Features of my new synthetic quilt are exactly the same as the down original with the only difference being the insulation and the way the drawcord assembly is fitted. It would be useful to read that piece too.

Construction notes

Building a quilt like this is remarkably simple and certainly much easier than the previously mentioned down quilt. Synthetic quilts don’t need baffles to hold the filling in place and this saves a lot of time. Anybody with basic sewing shills could easily build a synthetic quilt.

It is normal for the synthetic insulation to be sewn directly to the shell fabric, around its edges, for support which is not possible if want to make it swappable. What I've done is to sew loops of webbing at 30cm intervals around the shell seam and onto this webbing I attached one side of a press-stud. The other side of the press-stud is then added to the insulation and this allows the insulation to then be clipped/un-clipped to the shell. The insulation is too fragile to directly take a press-stud so the whole edge of the insulation has been stabilised with bug netting.

Webbing loops at 30cm intervals with press-studs to attach the insulation

The draw cord for the neck and foot needs to be attached directly to the insulation and NOT to the shell. If you attach it to the shell instead then the insulation will bunch up around the neck/foot seal which will be uncomfortable and drafty.

Drawcord in tube on insulation (foot & neck)
Drawcord passes through a slit in the outer shell (foot & neck)

A central zip allows easy access to the insulation. I chose black for the inner material so that the zip is less noticeable. Unless you look hard the quilt looks like any other synthetic quilt.

Inner shell zip opened up showing access to insulation

More press-studs are added to the shell to allow it to be closed up tightly when it's cold. Most commercial bags focus on weight and are often too short and much narrower than my quilt. This is false economy, stay warm and make your quilt long and wide enough!
The quilt is wide enough to be fully closed up

I used a very light M50 fabric for the shell which is a 10D fabric. It will not be as strong as the Pertex Quantum 20D fabric that I used for the down quilt. M50 has a very thin coating on one side that I presume is to either add extra water resistance or increase its wind resistance, but is likely to be less breathable than an uncoated fabric like Pertex Quantum. The upshot of M50 is that it offers around a 25% weight saving on the shell which is important when even the very best synthetic quilts will be around 1/3rd heavier than an equivalent down filled quilt due to the inferior nature of synthetic insulation.

Opened out in blanket configuration

ClimaShield Apex filling is the king of synthetic fills at the moment. It's biggest advantage is that it doesn't need quilting, for support, which creates cold spots. I only had 4oz Apex easily available to me so built two inners, 1 with a single layer of 4oz Apex, and a second with 2 layers of 4oz Apex. Cut the insulation the same size as the outer so that, when fitted, it is slightly too big. This is done so that it is not possible to stress the insulation when moving around as easily. Let the shell take the strain and not the insulation. Temperature ratings are very subjective but looking at other, reliable, manufactures using this filling a single layer (4oz) should be good for around 5C (40F) and the double layer (8oz) to around -6C (20F). As a cold sleeper I would take a few C off this.

8oz and 4oz ClimaShield Apex insulation edged with bug netting
Reliable clips for attaching the insulation to the shell are essential and I use press-studs spaced approximately every 30cm. The edge of the insulation was reinforced with 0.7oz bug netting which is simply wrapped around the edge and sewn in place. For the foot/neck draw cords I chose 2mm shock cord and tiny cord-locks.

Apex edged with bug netting. Foot/neck fitted with 2mm Shockcord and tiny cord-lock 
Weights of the finished synthetic quilt 

Quilt with 4oz Apex insulation (5C/40F) 620g
Quilt with 8oz Apex insulation (-6C/20F) 962g