Down pants convertible to elephant foot

REI used to make and sell these

For ease of use in cold conditions I would not go smaller than a #5 coil

Thinking about it for a while tho and taking into consideration modern UL fabrics I would no longer go down that road myself; I would simply take a half bag bivvy cover in an UL fabric like the 0.7Robic.

I am an advocate of half bags I have made several and currently own 4 of them. When I compare the simplicity and low weight against the complexity and minimal if any weight saving I would not bother except as a demonstration of my skills and I’m not sure I have the skills combined with the patience to do so.

I would find that either the pants would be too large or the elephant foot too small.

This is just visualising it, I haven’t tried that idea.

To me a big advantage of having puffy pants inside a sleeping bag is that it makes it so much easier to get out for a pee and much better in keeping me warm from camp to bed because I don’t need to strip off to get inside the sb. (I’m already wearing the night layers at camp that way)

Actually with the zippers at night in camp you can unzip only the bottom making it a long kilt.

I already started making it. It’s all cut and sewn. I just need to find the right zippers now. I didn’t want to spent a whole lot of time and money on this so I repurposed a Costco down throw.

If I understand what you’re trying to do you’re wanting to use two sets of separating zips, one set to form the legs and another shorter one for the fly, all meeting at the crotch. If the zip is going to be on the inside of your legs I’d want a #3 coil zip for the smaller bulk as well as weight. I’ve only ever seen one way #3 separating zips, but this should be ok if you make them attach at the crotch and zip down to the ankle.

Zipperstop and Quest Outfitters stock #3 separating zips.

I’ve thought about this from the opposite direction: putting an extra zipper in the lower portion of a bag/quilt to turn it in to pants so it can be worn in camp at night before bed.

I’d go w/ a #3 and not worry about the double pull.

I’m very much looking forward to seeing how these turn out!

Here’s a couple links to a similar project, even though it sounds like you’re mostly done at this point. Check page 2 in the first link for photos of the REI version Edward mentioned: https://backpackinglight.com/forums/topic/4455/page/2/#comments

And here’s Just Jeff’s MYOG prototype: http://www.tothewoods.net/HomemadeGearHalfBagPants.html

I’m wondering if the down kilt idea is better for around camp?

From a purely clothing perspective I prefer my zips on the outside

I had forgotten how klunky those REI pants were but I did own the matching parka and windsuit

Working prototype: https://imgur.com/gallery/ylBYH

I made it short and didnt make any provisions to close the bottom. I wear my apex sleeves on my feet and my puffy when needed. I just needed something for fhe mid section.

Looks great!  Crazy looking pattern when opened up flat.

I don’t have much merit on the pattern. I used a pair of full zip pants to trace each quarter pannel on paper and just taped the pattern to have my zips on the inseam.

Total cost is a Costco down throw, two 24″ and one 14″ zippers as well as some scraps.

Thanks for sharing.  I like the idea of the product itself and the use of Costco down throw.  I may give it a try.

Looking great!!!