Zipper Modification

Scott Wrote:

Scott,

I am sure that you will find that overstuffing will increase the warmth of the sleeping bag. I also doubt that the temperature rating before and after will be performed in strict accordance with the modern European standards $$$.

What can be quantitatively measures is the increase in loft by use of cardboard and level and a ruler. You will find that the loft increases, and you can quantitatively express it.

Also, there will be a weight change which can also be quantified with either a scale weight of the down added, and/or a scale weight of the before and after weights.

If you want to confirm anything you only have two variable data points — before and after. Before/After weight and Before/After loft. You might be able to infer a resulting down density. You aren't gong to have a realistic "warmth rating" of much accuracy, because you aren't going to measure it or any other thermal performance parameter.

Maybe you have something in mind for concretely "confirming" that I fail to see.

A long time ago (actually 1977) I gathered the weight, loft and claimed temperature ratings for about 60 bags and plotted it up as well as ran the data through a statistical analysis package. There was a lot of scatter, but you could see the trend.

If I were to do this again, I would instead try to use the fill weight data and the claimed filling power of the down to eliminate confusion in the data scatter by adding a variable for down quality (claimed loft).

The point here is to have a graph from which to add your bag
before and after the overfill. then the change that you got from overfill can be looked at to see if it is significantly different from normal industrial filling of down bags.

Maybe Western Mountaineering could be talked to to learn a bit more of their advertised option of down overfill on most or all of their bags.

This thread is getting me down. What about fixing that zipper?

Thanks for the lesson in scientific methodology James. Full lab testing won't be performed; this is just for my own personal knowledge rather than any sort of objective quantitative database. Having a relatively controlled testing proceedure and a knowledge of my own personal experiences, the experiment should provide relevant information for me, but certainly wouldn't be relevant for anyone else. However, since the lessons learned will only be used to determine appropriate insulation levels for me, the data does have value, though quantification is not possible.

Back to that zipper now …

I would probably contact Tim Marshall first. He runs a cottage soft-goods company called eNlightened. He's a member here, and several members can attest to the quality of his work. Search BPL for "cuben quilt" to find some photos of Tim's quilts.

Well, to get back to the science for a bit…

I've had a think, and done some reading, and think I've managed to create mental models that I understand, and that explain the first order effects in fairly simple terms. When I've got my thoughts clear, I'll try to type them up and start a thread on the G-Spot. Hopefully, this might prove useful to others.