Designing the perfect Icebox...?

[DMcCam]

I've integrated some of the great ideas into this current design. It has the recessed seal, and now sports a drawer with a magnetic freezer seal.



Those freezer doors are pretty tough to open by themselves. With a 1/2" magnetic seal, do you think it would require some sort of door latch too?

On with the quest...

[Engineer Guy]

I wrote some Tech Notes below to myself after some Web Surfing last weekend between new House finishing chores. Good fun!

Your new Design looks really sharp! I thought my Notes might help with some tweaks now if you decide anything below is worth making changes for functional integration.

When writing for Patent Applications, one term, say, for an older, non-super-Insulated Cooler Brand 'x', is 'prior art'. Besides 'prior art' Coolers, there's 'prior art' beliefs and 'best practices' [best back then] that I've reviewed to update my thinking. One best practice is to precool the Cooler; something not done even in fairly recent Cooler Reviews below published in Magazines.

Folks seeing Reality differently can read Websites linked below for themselves; that's the point of citing them. Another sound practice is to sample a larger population of Users than one-off Opinions in Forums.
---------------------------------------------------------------

Introductory Overview

While looking for objective information on Cooler types and best practices, one Forum Website kept leading me to another. Buried in the predictable staunch, unscientific opinions on Forums, here's what I found and filed away for my own future Cooler enhancements. I focused on super-Insulated Coolers because Ice and fresh Food lasts longest in them. Forum Posts below mention prices ranging from $200- to $900-. High Insulation values can be replicated at much lower cost. Coolers under discussion are state-of-the-art designs with construction details, and suggested usage practices, to guide any Designer.

There are variations in external construction and latches, but all use Polyurethane Foam, or equal, rated at Insulation value R-7 or R-8/inch [Wikipedia citation below]. There's no 'magic bullet' in Insulation, only widely-varying Cooler usage patterns; Test conditions; and Testimonials.

I started reading on Yeti Coolers - the de facto, high-end Outdoor standard - since I see so many of them around being used by River Runners and Hunters for icing down [Snowing down] Field-dressed Game. Pro Boaters and Fishing types, both Tournament folks and Guides who want happy repeat Customers taking home prized catches, post Testimonials for Yetis. They have the highest value Insulation: 2" construction with a 3" Lid to resist Solar-induced heat. The widely-varying 'Ice lifetime' comments jumped out at me and fueled further curiousity.

1. Testimonials and Forum Opinions

Yeti Cooler Testimonials. Note that when comparing Applies-to-Apples in cooling performance, Yetis claim Cooler Liner tolerance to Dry Ice. Some Forum comments refer to Dry Ice use which extends Cooler performance.

Yeti Coolers

This Boater's Blog re: Cooler use was interesting because it gave tips, like using wetted Towels, to extend Ice life. Impractical, perhaps, but while we're theorizing about it, these folks are out actually doing it.

The Boater Ed Forum

The Bass Barn Forum

Florida Sportfishing Magazine

2. To Keep Or Not To Keep Ice Water?

Results and/or Methodology of my simple Water 'bath' vs. Air test posted prior being disregarded for a moment, Manufacturers uniformly suggest maintaining Ice Water for best performance. These Manufacturer's comments apply to their non-super-Insulated Coolers as well. From Coleman:

'Don’t drain cold water. Recently melted ice keeps food and drinks cold. Melted ice water preserves ice better than empty air space.'

The Outdoor World

'Do not drain the water from the cooler – the cold water icemelt helps keep the items inside colder longer'.

Engel Coolers & Refrigerators

Yeti assumes there will be Water in their Coolers and offers this:

'And, they come with a rubber-coated dry-goods rack, to keep smaller perishables [like Sandwiches] out of the water and off the bottom of the cooler.' See this Yeti Basket pictured in the Engel Cooler comparison on their Website linked below.

Yeti Coolers - Wildly Stronger

'Don’t drain the cold water from freshly melted ice out of the cooler, as the cold water helps keeps the items in the cooler cold. Drain the water only when necessary to create more space in the cooler or when adding more ice.' A sidebar tip here is to 'keep the Cooler full of Ice and Water [minimizing less efficient Air] unless more space in the Cooler is needed'. Note here the picture of that suggested technique; old news. Additional Insulation in the form of Reflectix, or Astrofoil, was recommended as a Cooler performance enhancement.

Desert USA

'Frigid Rigid' Coolers ran 3rd Party tests and poured out Ice Water 1x/day solely as a volumetric measure of Cooler efficiency. Note the initial conditions of adding 40 lbs. of Ice. Not too TD-friendly. No Food - a heat load over time even if all Food was pre-chilled - was ever added. As I learned over the decades, Test conditions have to reflect intended use conditions. So, this Test 'proved' this Cooler can chill an empty metal Tray. Water was expected 'simulating normal use of the liquid storage container'. Their Freezer model uses 3" Foam construction throughout; the minimum I would build with R-8/inch Thermax not having TD Cooler size criteria to meet. I had been thinking long ago of a scrap Aluminum Plate on a Conventional Cooler bottom to conduct 'cool' from Ice were Water not used, and Frigid Rigid uses Aluminum as their inner Test Box. Perhaps cold-conductive Cooler innards - vs. Plastic - would help in Water-free Cooling. Weren't antique Iceboxes made this way? Or, were they Thermoplastic? ;-0

Frigid Rigid Coolers

On the Forum cited below, the usual spate of one-off anecdotal opinions ends with this 2004 Icey-Tek Website reference from Poster 'afishinado'. Yeti makes the same point separately in the Engel Test .pdf below: Coolers retain ambient heat until cooled with 'sacrificial' Ice.

'The Icey-Tek® line of coolers are the most insulated coolers on the market today.

Due to the amount of insulation used in this product it will retain heat as well as cold.

If you have stored your cooler in direct sunlight and in temperatures above 72°F (22°C) your cooler will have the same heat retaining characteristics as a preheated oven. If you load the cooler with ice in this respect, you will not realize the cooler’s full potential in ice retention.

Firstly, we recommend the use of larger-sized cubed ice or block ice. Small-sized cubed ice and crushed ice have a larger surface area on which heat can adversely affect it.

If your cooler has had the opportunity to build up heat you must place a small sacrificial amount of ice (10 LB or 5kg) inside the cooler (Cooler Size Pending) three (3) hours before loading it with the intended contents. This reduces the heat within the walls and the lid of the cooler allowing it to retain ice in the manner it was designed. Since the ice will melt to initially cool the cooler, you will need to empty the water to allow room for more ice. The longer the cooling down period, the lower the temperature will be before use and the better ice retention will result.

Also you should load the cooler with as much ice as possible. Air spaces in the voids where ice could have been placed will also increase the loss of ice due to cooling of the air within that void. Pre-cooling the intended contents drinks, food, etc. will also help in maximizing ice retention.

Once the cooler is in use, we recommend that you do NOT empty the cold water. More energy is required to cool air than to maintain the cold water.

If using your cooler to store or transport cold food, for food safety reasons please ensure that the temperature remains below 40°F or 4°C. The danger zone for heated food is between 40°F or (4°C) and 140°F or (60°C).

The Hull Truth

Engel makes both very efficient Refrigerators and Coolers, and states this Test and usage condition in the .pdf linked below:

'Had we been trying to determine the maximum time each cooler would keep its cool, we would have used more ice and would not have drained the melt water'.

Engel Cooler Usage Recommendations

Engel Cooler Comparison Test

Also, see the front-opening Engels linked above for standard TT Fridge form factors.

3. Conditions of Cooler Use

This topic arose repeatedly. How often is the Lid opened [pertinent to adding Drawers]; what are the ambient temps and Solar ingress; how full of Ice is the Cooler kept; and so on. Given such wide variability of usage conditions in the Real World, my hunch is that this is why folks report such varied results on new or 50-year-old Coolers. I'm seeing zero Front Door Coolers on the Coleman Website. They've reintroduced the old Metal Coolers, but make this point: 'We also beefed up the insulation to further enhance the performance'. Perhaps the old Insulation performance levels were deemed insufficient for today's Market?

So, having never seen folks toss one another an Air-cooled Beer in a TV Ad, or been handed one at a BBQ, I'm sticking with Ice Water cooling that the Boating/Outdoor Pros above use, while limiting the inconsequential [to us] Water 'mess'. The positive tradeoff: longer Boondocking times. We'll use el cheapo Baskets. Add Ice frozen in a rectangular Plastic Container to chill Water to the ~33 F temps noted in the Frigid Rigid tests to last ~1 week by integrating the Blog tips above. Maintain chilled Water to suit. Set the Tray back in cold Ice Water after obtaining Food. Or, Food can be plucked out of Baskets left stationary. Food types can be grouped [frozen for use later vs. fresh]. Ice/Water ratio vs. Food storage space can be tweaked over time. The Chilled Air stratification problem Posted above earlier becomes irrelevant. Any 'excess' Ice Water will go to our Dog. One Blogger suggests a separate small Cooler for frozen Bread and things desired dry. This skips the soggy Food issue endemic to attempting all Food storage in one Cooler.

4. New Cooler Design Considerations

For the TD 'air-cooled' Cooler, keep Ice at the top; the preferred positioning. Sounds like the Krown Cooler, and others, had upper Ice placement figured out. Water Drains can be used, or not, as folks want while establishing through they own usage patterns what works best for them. Drains in Coolers above for maintaining Water level are included for Marketing reasons and convenience; not because cold Water shouldn't be used. Coleman, Yeti, Engel and my Grandpa have weighed in on that preference to my analytical satisfaction. One future TD Cooler design thus fits all: Air or Water cooling. Boondocking concerns aside, greater Cooler efficiency allows less Ice to do the job over a typical weekend. This allows for more Food storage in a given volume.

Perhaps Magnets on the TD Cooler Drawers could pull closed tightly to ferrous plates, compressing a good Gasket[s] to minimize 'cold' loss. Tradeoff: it would take a good 'yank' to pull open the Drawer. Whatever idea[s] would keep the Drawers hermetically snug... To promote 'cold' conduction, perhaps all Food should be in 1 or 2 Aluminum Boxes - recycled from some other use? - that pull out on Drawer Slides [or lift out in a top Lid design]... Build Galleries on this Forum show some nice Slides. See these Slides also:

Engel Cooler Slides

5. Cooler Usage Considerations Whether Old or New Technology

Pre-cooling the Cooler with 'sacrificial' Ice discarded before travel is as essential as pre-cooling Food [the internal heat load]. We'll start doing that, just as we all perform other pre-Camping check list items. This clearly leads to better Cooler performance over time; a plus for Boondocking.

My thinking some time ago was to make additional Ice on the go while Towing [via +12 VDC Fridge operation]. For now, I'll retrofit maximum Thermax and/or Astrofoil Insulation to the Dometic Refrigerator in our TT. Transfer Ice from this small TT Fridge to an 'ordinary' pre-chilled, Ice-packed Cooler nestled within a Thermax R-24 'Box' w/R-24 Lid under a Dinette Seat or wherever. Extend Boondocking Propane and Battery reserves for other uses by using an R-24-encased Cooler as a cold 'Thermal Flywheel'. Minimize Genny run time while Boondocking until I can afford a fabulous 'bdosborn' Solar Array running a high-performance Fridge!

We have plenty of 'Blue Ice' Packs around, since my Jockette Avatar injures Knees and other Body Parts regularly. Blue Ice flexes some even when at 0 F degrees, or can be lowered to temps below 0, as noted above. Salt Water-filled Ice Containers are an option.

6. Future Test Conditions Improvements

My conclusion on Test conditions reviewed: an accurate, real Test - either not yet done or found - would be to ice/water down the Cooler interior for the >3 hours recommended above. Dump water for air test only. For Water test, leave chilled water in. For all Tests, add new Ice, per above recommendation. Add only pre-chilled Food and Beverages. Whether Water or Air cooled, measure Cooler internal temp and a Beverage temp over time in a stable, ambient temp environment not in Sunlight. This Test would characterize Insulation and Lid Seal effectiveness of a given Cooler design, and water vs. air cooling efficacy. It would quantify Real World results that Users could expect on weekend trips, or while Boondocking. Tweak Test Cooler to meet design criteria posted earlier by DMcCam.

Adding a trapped Cooler Drain in any proposed design is a simple enough solution for both 'Customer' preferences.

The proposed ~7 day Cooler performance spec = 168 hours. The 3 hour Cooler/Ice chilldown period is ~1.7% of a 7 day week. An 8 hour overnight Cooler chilldown period is ~4.7% of a 7 day week. I have concerned myself with Cooler performance after chilldown periods. What happens with Water vs. Ice during chilldown is irrelevant to meeting the more-important, long term Design spec of improved Cooler performance over longer Camping times.


Other References

Icey-Tek Coolers 35 mm construction ~1.4" Insulation

SSI Coolers 1.5" Insulation

River Marine Supply

Wikipedia - Spray Foam Insulation

Icynene Insulation

Thermax Rigid Insulation

Laws of Thermodynamics

[Photoman33770]

So there I was.......
I was out and about today and stopped in a local Publix store. Walking the aisles I did a sudden stop and had a flash back. There before me was a brand new display of...... ( drumroll here )........
Dry Ice !
If using dry ice instead of water ice, all you need is a tiny vent hole to allow expanding gas to escape. ( could even use a thin hose connected to leak it out to the ground. If the sleep compartment is sealed well from the kitchen area fear of CO2 build up is not an issue.
I doubt there are many stores that carry it, but dry ice should be avail somewhere in every area.

[Catherine+twins]

Ah, dry ice, yes, I remember my dad thinking the same thing. The sparkling carbonated oranges from the ice chest were...interesting. The carbonated milk was just bad.

Dry ice is good for keeping frozen stuff, like meat, frozen. It is not good for simply keeping cold stuff cold.

Hey, here's something I have been doing this year. First of all, I buy box wine, have been for years. The second piece of the story is that I have a food saver that I can use to seal plastic bags. So I had the bright idea of cutting a corner off of an empty wine bag, washing it out and filling it with water, sealing it again with the food saver, then freezing it solid in my freezer on the back porch. (This was partly done so I had ice in the freezer when we have our lightning-triggered power outages at home). The frozen bag then goes in my ice chest (a nice block of ice), and as it melts it becomes water to drink. The bag even has a nice spigot to dispense from.

Catherine

[Photoman33770]

Perhaps an upper area for the dry ice above a freezer section. Below that the refer part divided from the freezer by an insulation barrier. A slide vent between the two, to limit cold air exchange to the lower refer section. Much like old fridges did for many years.

[martha24]

dakotamouse created an icebox in their teardrop. I think it is very ingenious and looks fabulous. In fact their whole teardrop is fabulous.

Ice is put in on the top box made out of a tupperware box and has a drip hose for melted ice. Icebox is made out of water container if I remember right. It has 1 1/2 inches of insulation and front is trimmed out in aluminum. They were just at IRG and I got to see it there.

Here is a link to some of the photos in their album.
http://www.tnttt.com/gallery/album.php?album_id=1946&sk=t&sd=d&st=0&start=84

[jstrubberg]

Thanks for the links Catherine and E-Guy, very interesting tech. The ammonia water system is amazing. I can see its attraction for off-grid applications. The British girls story reminded me about a 1970's British icebox company that used evaporative cooling panels in their design. If memory serves, the unit used a wicking material that dipped into water trays. Why not use the ice melt to feed such a system? The idea has merit for sure. No moving parts and powered by heat; boy is that turning a disadvantage into an asset.

Amazing stuff here.

Fascinating topic. This touches on so many aspects of teardrop camping. Energy conservation, space issues, etc.

One thing to watch on evaporative cooling....it doesn't work worth a darn when ambient humidity rises. As air gets closer to saturation, not enough evaporation occurs and you end up warm and clammy instead of cool and comfortable. Not an issue in your part of the world, but something to keep in mind should you do much travelling to the midwest and south.

[rowerwet]

I can't remember where now, but I remember reading about a week or two long expedition type boating trip where there was no ice around and little contact with people until the end was reached. they packed each meal in order (steaks on the very bottom for the last night) a little dry ice in a cardboard box on the bottom and everything pre-frozen that needed to be. Only going into the cooler as little as possible, taking the whole meal out at once, (pre bagged together) kept the cooler the way they wanted for the whole trip. takes more work to set up though.

[cheri832]

Has anyone tried insulating with aerogel? It's what NASA uses to insulate spacesuits. Several companies make an insulation "blanket" that is thin, flexible, and somewhere around $5 a sq ft. For the cost of an inexpensive cooler, it might save some space and really work. Curious about whether anyone else has thought about trying it....
Cheri

[DMcCam]

Hello Teardroppers! It has been far too long to check in with all of you on this thread. We have been having too much fun camping with our trailer since 2013, can you believe it, this will be our 10th year. After camping with our little Travelear for so many years, we have made only a couple of additions and no real changes. The trailer performs exactly as designed.

We finally got her icebox installed in the galley. The Icebox was included in the original design for the galley. However, I lacked the skills and tools to make it. I finally found Jim with his full shop and fabricated the little devil out of sheet metal. It took quite a few hours and several re-dos but it was worth it. Last year we camped in about 85 degree weather dropping to the mid 60’s at night. The Icebox cooled things down to about 36 degrees during the night and only got up to around 42 degrees during the day. The concept seems to work pretty well.




Here is how our gallery looks today with the installed Icebox.


It pulls out to keep as much cold air in as possible. This shows how far it opens.


These are very strong drawer slides that auto close when you push the drawer back in.


Here you can see the ice tray in place and that the drawer pulls out plenty far.


Looking down into the drawer. We can actually store more food in here than our large ice chest.



The ice tray must be angled to lift out if the drawer is in place.


The ice tray holds 3 – 10 LB blocks of ice and is secured by a screw when we’re on the road.



Here’s the drawer with its double magnetic seals. I ordered these to fit online.


The ice tray showing the interior grill for drainage.


This shows the construction of the upper area of the icebox.


The lower drawer slide installation.


To keep the drawer from moving while traveling, we installed some serious Velcro strips.


Here it is all ready to travel.

I place a sacrificial bag in the ice tray the night before we go. The departure morning, we place the 3 10lb blocks of ice in the upper tray, then everything that's frozen in the bottom of the drawer then everything else fits on and around it. When we are ready to move the trailer, we drain the ice tray. So far, it looks like we can go 5 days without adding new ice if daytime temperatures are below 85 degrees, 4 days if they are above 100.

All the Best,
Dave

[nevadatear]

Hey Dave, looks great! Hope to see you guys out camping soon, if the fires ever stop.