I have a hyrdoflask vacuum insulated bottle, and it’s nice, but it’s heavy being made out of stainless steel. I can’t afford a titanium vacuum insulated bottle (and they’re still on the heavyish side), so i’ve been thinking of ways to make an alternative that may be even lighter. I don’t have the capabilities for vacuum insulation unfortunately, but in any case, while nothing can beat vacuum insulation–it always has a weakness, the top, not well insulated part.
There are two main ideas, one is more expensive and complex, and the other easier and cheaper. Feel free to vote.
Both ideas center around using a silicone bottle for the part that will hold water. Silicone because it’s fairly lightweight, relatively inexpensive, fairly low thermally conductive, probably the least reactive and most inert of the plastics commonly being used for food/beverage products, and it handles heat very well (and boiling water no problem). Also, when not being used, in one of the iterations below, it can be squashed down to conserve space if need be. Initially i was looking at Al bottles, but it seems they all have some kind of either epoxy or resin liner, which probably has chemicals with estrogenic type effects. I wanted to get a plain old brushed Al bottle and anodize it myself, but it’s surprisingly hard to fine pure Al bottles. In any case, the silicone bottle seems better all around for this purpose.
1st, the more expensive and complex concept: Buy a larger PP (polypropylene #5), cheap, wide mouth bottle–into same will go the silicone bottle, as well as insulation and Al foil. First build a cozy out of bumpy foam, smooth side will wrap around the silicone bottle w/ a bit of space. Around the bumpy part, i will wrap some heavy duty Al foil or heat sheet material. Into the various spaces between the two bottles will go hydrophobic silica aerogel particles (roughly 1 mm in size), which i can buy 4 cups of for 45 dollars and for the amount i use, won’t register on my scale by itself. The silicone bottle will fit through the lid of the PP bottle (cut a hole), and i will seal it up with an epoxy, hot glue or what not.
Then make a top, simple “sleeve” to go over the top of both bottles, out of a combo of silpoly membrane and breathable .66 oz/yd2 membrane and stuff with some left over 600 fp down i have. The silpoly will go on the inside to block moisture, the .66 oz nylon will be on the outside to let the Down breathe and loft. Since it will be a simple sleeve, and won’t have enough insulation at the seams at the very top, so into the sleeve i will stuff some left over Apex (probably with some fabric sewn around it to protect it some).
I figure the above will have some pretty serious insulating capacity at not much weight. The silicone bottle is a 20 oz one, and i’m estimating it (the total system) to weigh total around 7 to 9 oz dry. That’s about the same weight as a non insulated, single wall SS bottle of similar size.
Ok, the more simple and less expensive version: Basically just make the foam cozy that goes up most of the way of the bottle, wrap with Al foil or heat sheet, and make two separate sleeves using the above fabrics mentioned and the Down. One goes over the bottom and the foam cozy and the other, thicker and wider, goes over the top (again with Apex pushed into the top). This version won’t cost me any extra money besides the silicone bottle i’m waiting on, is easier, and more convenient to clean, and will take up less space in the pack. Also probably will be a bit lighter since it’s sans the PP bottle.
WWBPLD? And thermally speaking, do you think either version can compete with a traditional vacuum insulated bottle for keeping water warm? I suspect concept 1 will have the thermal edge due to the aerogel material, which is the next best thing to vacuum insulation weight and thermally wise. But do i want to spent 45 dollars on 4 cups of this stuff… not so sure. Perhaps if someone was interested in buying the same kind of bottle insulation system off me for around 25 dollars, i’d might consider it. (I’m actually receiving two 20 oz silicone bottles at the same time anyways).
