Theoretical question; designing a sleeping bag

[Moondog55]

Starting from the ground up:
What design features and in what order would you rank the importance??
What and why would you choose?/
I'll post my answers in a little while and I'd really like to hear what Blacksheep has to say on this one.

This question is not directly related to temperature rating although that will have design results

[photohiker]

Easy.

It should weigh next to nothing, be as warm as you need on any particular situation, waterproof and self drying should it get wet, and of course pack small.

I'll have one please.

Assuming we're talking about down, I think the primary constraints are bulk when packed and weight of shell materials. Choice of high quality down will minimise down weight for loft, and adequate baffle design should minimise cold spots.

While it might be fun, if you value your time, I have my doubts that you can make cheaper than buy - unless you cannot buy what you need...

[blacksheep]

Starting from the ground up:
What design features and in what order would you rank the importance??
What and why would you choose?/
I'll post my answers in a little while and I'd really like to hear what Blacksheep has to say on this one.

This question is not directly related to temperature rating although that will have design results

Who is the customer, what are their needs? There is a reason we make 6 ranges, each with multiple options.

[Moondog55]

OK here is what I have at the top of my design criteria.
A foot box that I can actually use, I have size 13 feet, I was going to buy a sleeping bag from the PHD sale until peter let me know my feet just would not fit, same problem with Western Mountaineering and the bags I just tried at Paddys.

Blacksheep I was asking for you to respond as this has always been my biggest issue with bags from Macpac, especially the older "downside-up" range. I have big feet but not unusually so and as people get taller the foot size is increasing on average across the whole population.
I still have my "Marathon" just it is now a halfbag with a Thinsulate bottom ( pix on request )
Next I want modularity, so that I can use a system if I cannot afford a different bag for each season.
Next I want the zipper over the chest and not on the side.
Everything else; such as down loft and fabric weight are secondary to these prime considerations

[photohiker]

A foot box that I can actually use, I have size 13 feet, I was going to buy a sleeping bag from the PHD sale until peter let me know my feet just would not fit

Did you ask about custom? PHD will design around your duck stompers if you ask them.

[Moondog55]

No they won't, I asked, I was told to simply buy a bigger bag than the lightweight one I wanted and then order a lower fill.
I can see why tho; it is all about the pattern and getting the maximum return, I think that is one of the reasons that round 300mm foot-boxes were sort of standard for years, that size would allow the full width of the nylon to be used with minimum cutting.
I want a foot box 400/ 450 high by 300/350 wide, that would need piecing and add to the cost,

[Tony]

OK here is what I have at the top of my design criteria.
A foot box that I can actually use, I have size 13 feet, I was going to buy a sleeping bag from the PHD sale until peter let me know my feet just would not fit, same problem with Western Mountaineering and the bags I just tried at Paddys.

I also have size UK 13 feet and I use a 6' Western Mountaineering Summerlite bag, I have not noticed the foot box on my bag being too small for me.

Tony

[Moondog55]

Lately I have developed extremely sensitive feet ( a side effect of medication ) and I just cannot bear the bag touching me, i have had to go up a size in boots too, but it is worse at night.

[cdg]

I made a sleeping bag out of polar fleece. i bought two different types from spotlight, measured, cut and convinced the minister for war and finance to sew it. Much swearing later, I had a very light easily washed sleeping bag. My dilemma was/is that im very tall, and barely fit in commercial sleeping bags. Its OK for anything except winter in the snow. I dont go camping then, so Im good. It doesnt have a a zip, i used velcro half way down the side.