Friday, 13 May 2011
MYOG, Cheap Hammock Under Quilt Experiment
MYOG Under Quilt
You don’t have to spend long on hammock related websites to realise that regular sleeping pads aren’t the preferred choice when it comes to insulation, likewise you don’t have to spend too long in a hammock trying to use a regular sleeping mat to understand why.
It seems that under quilts (UQ’s) are the preferred choice and as it didn’t seem as if it would be too difficult to cobble up something together I fitted a couple of expansion bolts in my garage so that I could hang the hammock to try a few ideas. I couldn’t resist trying the hammock to see how comfortable it would be over a longer (more than a few minutes) period of time so decided to sleep in it in the garage. Having tried a full length CCF mat briefly when I got the hammock and decided against it I decided to try an Alpkit Wee Airic ¾ length self inflate which was better and to provide some insulation for my feet I just pinned my Montane Flux to the edges on the hammock letting it hang underneath like a UQ (The Ever Versatile Montane Flux ;-)).
What I discovered was that a hammock is very comfortable in spite of the Wee Airic slipping around, lying diagonally in the hammock you lie really flat, not curled up like you’d expect. The Montane Flux seemed to work just fine so I decided the easiest way to make a cheap and cheerful UQ was to convert a rectangular sleeping bag.
Coleman Pacific Kid's Sleeping Bag
In the end the only one I could get locally that was even remotely light was a kid’s Coleman Pacific. At 150cm wide when opened out and 190cm long it looked like it would just about fit. I picked one up in Argos for £14.99 but when I got it home I realised that even if I could convert it into a UQ it wouldn’t really be suitable outdoors thanks to a brushed/flock type lining. Still it was better than nothing so I set about converting it.
I reasoned that as the hammock itself is rectangular until it’s cinched at the ends then the UQ could also be a rectangle so the 1st thing was to remove the zip. Fortunately the zip was sewn onto the side and end seams rather than sewn into them so it was only a matter of unstitching it. I needed 2 drawcord tunnels 1 at each end and while the bottom was easy only needing the fabric folded over and sewn the top end need a little work. The inner brushed fabric extended out of the sleeping bag and down the outside for about 10cm so I simply cut 10cm off the sleeping bag to remove it. With that done I trimmed back the fibre filling by about 10cm and then formed the drawcord tunnel by making a hem on the raw edge before rolling it and sewing it down. I made the drawcord tunnels much wider than I normally would as I thought the brushed inner might stop the shock cords from running smoothly which turned out to be the case.
I wasn’t sure how to go about attaching it to the hammock and tried a few things before settling on a heavy shock cord on each end running through the tunnels I’d sewn. At first I had cord locks fitted to allow me to loosen/tighten the ends to seal against the hammock but I discovered that if I cut the shock cord to the required length and then knotted the ends I didn’t need the adjustability. What I ended up with was about a 35cm shockcord that could stretch out to 70cm at the foot end and 50cm stretching out to 100cm or so at the shoulders. To attach it to the hammock I ended up sewing on webbing loops at all four corners to attach shock cords.
Foot End Attachment
At the foot I simply took a length of shock cord and tied one end to the bottom left webbing loop and the other to the bottom right webbing loop, I then put the doubled up shock cord through a glove hook and then through a cord lock before tying a loop in the end to keep it from pulling back out of the cord lock. To attach the UQ to the foot of the hammock I hook the glove hook over the suspension rope (whoopie sling) and to tension it I simply pull the shock cord through the cord lock.
Head End Attachment
At the head/shoulder end I fitted cord locks to the webbing tapes, placed a glove hook on the shock cord allowing it to run freely and then put the shock cord through the cord locks. I tied the running ends of the shock cord together so that when I’m lying in the hammock I can get hold of the opposite side shock cord (I only have zipped access on one side of the hammock) by 1st reaching out and grabbing the nearside cord. I suspect that as the shock cord runs freely through the glove hook that the UQ will be self centering anyway even if I make all the adjustment on one side.
With the suspension sorted it’s really easy to attach the UQ, I just place it in the hammock to start with, then attach the UQ to the foot end of the hammock and tension it a little. I then take the head/shoulder cords and again attach the glove hook to the hammock suspension whoopie sling at the head end. Once the UQ is attached I lift it out of the hammock, open it out and place the hammock inside it. With that done it’s a simple matter to adjust the tension to get the UQ where I want.
Under Quilt Laid In Hammock Prior to Being Attached
Foot End, Glove Hook Attached to Whoopie Sling Suspension
Head End, Glove Hook again Attached to Whoopie Sling Suspension
Under Quilt Attached Prior to Tensioning
Under Quilt Fitted and Tensioned.
I have to say the difference is amazing considering it’s only a cheap kids sleeping bag, it feels warmer immediately and the hammock is even more comfortable thanks to not having a sleeping mat slipping around. I can move around in the hammock, lie on my back or switch to my side which is how I sleep without constantly trying to rearrange the sleeping mat. As for insulation well I taped a thermometer to the bottom of the hammock with the UQ in place, with my wife laying in the hammock I waited until the temperature stabilised before removing the UQ, within 5 minutes the temperature had dropped by 5°c and according to my wife the difference was noticeable as soon as I removed the UQ, swapping around I found the same. I tried it using my summer weight synthetic bag as a top quilt by just zipping it closed at the foot end and again it’s much easier to use than a sleeping bag and when combined with a UQ it’s like levitating in a sleeping bag as the insulation on the bottom is lofted just like the insulation on the top.
Unfortunately although it works in principal the fabric used for the inner makes it unsuitable for use in the field and of course it’s heavy at almost 1kg considering how little insulation there actually is. What I’d like to do now is make one from scratch using better fabrics and insulation, I’d like to go for something like Primaloft Sport 60g which should be enough for summer use but I’m having difficulty finding out exactly what type of fabric to use as according to the information on Extreme Textile, Primaloft Sport requires you to use a down proof fabric. In the meantime maybe I could replace the brushed cotton type fabric with plain nylon or something. Although that would mean pulling the quilt apart and starting again I wouldn’t really mind as it would give me a bit more sewing experience before I start working with more expensive fabrics.
Under Quilt Pulled Up Around the 'Footbox'
Lying diagonally with feet to the right and head to the left or vice versa results in a flatter lay. The 'Footbox' is created by the looseness of the hammock fabric once it's been cinched at the ends, the fabric under tension from the suspension lines causes a ridge to form (creased section just left of my knee) at both ends, pockets of looser fabric are formed at both ends left and right of the ridge.