Insulation feedback, WWBPLD?

[Anonymous]

First, non editable post.

[Anonymous]

While I’m waiting on some materials for a main, current project, I’d thought I do a little small, side project that some here might find interesting.

I’m making a lightweight, super insulated container.  The actual container itself will be made out of Balsa wood with a thin layer of food grade silicone covering it inside and out. Primary purpose: a combination of ultra energy efficient “slow cooker” as well as to keep beverages from freezing and/or more temporarily warm on trips where temps dip near or below 0* F for the low.

Approximate dimensions of the inner part cylinder will be 4.75″ diameter x 5″ height. Approximate thickness of the balsa will be 1″. Balsa is a fairly insulating, low thermal conductive (and lightweight) material in and of itself. I’ve yet to find a standard or agreed upon measurement of same though. I’ve seen it vary from .1 to as low as .048 (W/m°C). Either way, it’s at least slightly better than “solid” polypropylene, if not significantly more insulating. For a solid, non foam material it’s pretty decently insulating.

The question, and what I’m looking for feedback on, is what to use for the extra insulation?  Of two minds about this. One option (#1) that I’ve thought of is a “hollow” cozy made out of EVA foam, with a 1″ or so gap, to be filled with Aerogel particles. Since we’re talking so little volume, weight is not really an issue.  This option will be somewhat bulky though. Also, there is the slight possibility that the aerogel particles could get damaged even though they will be cushioned and fully contained between two layers of 1/4″ EVA foam.

Another option (#2) is to make a cozy out of a combination of highly waterproof inner fabric, goose down, and breathable outer fabric.  I can go “crazy” with this and make a very highly insulating cozy at low weight and low bulk.  I also already have 700 fp down and fabrics on hand, whereas I would need to order aerogel.  I could make a 4 to 5″ thick down cozy/”sleeping bag for it, or even thicker if I wanted to.

I’m also thinking of combining the options above somewhat (#3).  Make a single layer 1/4″ or 1/8″ foam cozy for the container to directly nestle in, and which it would stay in all the time to help protect the balsa from damage, and then still also have a outer down cozy to go around that.

I’m basically looking to get similar insulation as my stainless steel, vacuum insulated tumbler at a lower weight. The vacuum insulated gap looks to be around no more than .175″ or so. Should be easy to match at less weight.  Haven’t done any specific calculations, but I expect the container+extra insulation to weigh somewhere between 5 to 7 oz for a similar volume capacity as my 15 oz SS vacuum insulated tumbler (which would actually weigh a bit more because it would still need extra insulation on top of the lid to be more thermally efficient).

Option 1, 2, 3 or a completely different concept/idea?

 

[Anonymous]

“…but I expect the container+extra insulation to weigh somewhere between 5 to 7 oz for a similar volume capacity as my 15 oz SS vacuum insulated tumbler (which would actually weigh a bit more because it would still need extra insulation on top of the lid to be more thermally efficient).”

Did some calculations. The SS tumbler that weighs 15 oz, holds 30 oz of water. The one I’m making would hold about 49 oz of water. Similar might not be accurate–significantly more might be more applicable.

 

[Edward John M]

Old fashioned Hay-Boxes had 4 to 6 inches of good dry hay and while modern insulations are much better nothing beats low depth/thickness except a reflective vacuum layer.

But as you are using balsa why not ribs standing out to give a trapped air space and a good quality reflective paint? Talking theoretically this is, my own experience is that a good woollen blanketing material plus some reflective bubble wrap is good for a couple of hours.

On the thinking tho that every little bit helps I have a 1 litre SS water bottle and i had a 1.5litre water bottle parka so I wrapped the WB in a spare wool sock. the extra insulation was minimal but effective.

I like real oat porridge for breakfast and as that takes 4 hours to cook properly I’m interested in how this goes.

To answer the original query go with a secondary sack overfilled with goose down

 

[Anonymous]

Thank you Edward for the feedback.

I’m not sure what you mean about ribs.

In either case, I’ll let you know how it goes. I’ve received my other materials and since it’s warm and I’m more interested in the other, main projects, this one is going on the back-burner for now. I’ve also found that Balsa is not so easy to work with as far as hand carving and the like. It splinters and chips really easily.  When I get back to it, I’m going to invest in a decent jig saw and some dual cut, high teeth per inch blades, which should make it a much faster, easier, and neater to finish (I’ll need a jig saw for another project anyways).

I’ve made a couple of changes to the design. It won’t be quite so wide diameter (so it will be closer to the 30 oz capacity), and I’m contemplating fiberglassing the majority of the outside, minus a silicone lip area for mouth contact. This is because balsa seems to be a little more fragile than I initially thought. I want it to be able to take some impact without damage. Then again, an EVA foam cozy should provide plenty of protection, while boosting the insulation.

But yes, I’ve decided on goose down as the primary insulator either way.

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