Cob Solar cooker: Making the form

[Sonuchka4]

I don't know much about cob/clay. Could you also make it out of muddy clay/sand and fire it? Would that be stronger/more weatherproof/more smooth? Kind of like making an upside down wood-fired cob oven? Thanks!

[gaiatechnician]

@Sonuchka4 There is not too much involved in making cob. But I don't think firing it will work. You could limewash (whitewash) it (hydrated lime) instead or use linseed oil to waterproof it.

[gaiatechnician]

@Sonuchka4 If you are going to do something for frying, I suggest something different. Attach your alu foil to 1 ft by 1ft tiles and then put them on some sort of a backing. Alu foil automatically wrinkles when you try to curve it for a parabolic dish.

It simply cannot be laid without wrinkles on a dish. (you can lay it flat on a trough) Email me or check out the Dolios and Petisos Solar Cookers. They are the closest things in the real world to the concepts I try to develop.

[Sonuchka4]

(beginning of text below). First of all, how heavy is your cob solar oven? Is it easy to move? Second, how resistant is it to rain/weathering? How long will it last? It is likely to break if dropped? Third, how can you make it smoother? Paper Mache? Clay? Thanks!

[gaiatechnician]

@Sonuchka4 Hi, I took it apart. I just do these things as proof of concept.

As far as i know nobody else ever made a solar cooker this way.

I couldn't afford to do more than a few days putting the concept together and then making the thing. I work at stonemasonry during the summer so I have very few test results. I come home at about 5.30 pm and check the temperature of something that cooked at about 3 pm. Not much else I can do. Check the clam shaped solar cookers too Brian

[Sonuchka4]

Thanks for all your videos gaiatechnician. You're the only one I've seen who thinks about how to make them for people in the developing world (who are the most likely to need them). They don't have satellite dishes lying around! I'm going to Haiti soon and would like to try this cob method, but if I want a dish that can fry foods, I need a perfect paraboloid with a precise focal point, and a very smooth finish so that the aluminum foil doesn't have wrinkles.

[gaiatechnician]

@Sonuchka4 I know it might be a pain (because I have many videos) but you might check out some of my newer video's, The clam shaped solar cooker ones, etc. Maybe bring a laser level with you to Haiti and you might be able to do the clam shaped thing. The Haitians should be experts in using clay for building, etc. I have a friend in Haiti who is also enthusiastic about solar cooking.

Brian

[Twomidgetsonahorse]

hey, invest in a tripod for your cam. I got motion sick just watching this

[fergawdsache]

Why did`nt you just drag a template of the right shape attached to the end of your arm ?

[gaiatechnician]

It is kind of like a lathe. A lathe takes off a tiny amount of wood or metal at a time. It would not be capable of taking an entire strip at a time. I would not be strong enough to move your template.

Also, I would not know where the focus and sun direction is with a template. Lately, I have been making off centre parabolic dishes (More appropriate in many cases) and in these cases, a template is even more impractical.

Brian

[fergawdsache]

Ok thanks for the prompt response, one thing im not sure of is, what`s the difference between an elipse and a parabola as regards shape,  and could a section of a sphere not work as a solar concentrater.

[gaiatechnician]

elipse has 2 focal points, and is like an elongated circle. It might work, a section of a sphere might work too. I havn't time to test everything. If you point a parabolic dish at the sun, it concentrates to a smaller point.

This point means a smaller area for heat loss from my experiments. This is why i use a parabolic dish.

[fergawdsache]

I guess what im trying to say is, Is a parabola a specific shape, Ie, if you drew an arc, must it be of a certain length to depth ratio, or is a parabola any arc that would in the case of a mirrored face, create a single focal point.?

[gaiatechnician]

A parabola is a specific shape like a circle or square. Every parabola has the exact same shape but can be big or small. So i guess in your words, "a parabola would be the only arc that produces a single focal point!"

Elipses are like rectangles in that regard. They come in a variety of shapes from almost circle to very elongated. Hope this helps.

[fergawdsache]

Yes thanks, by the way when i said elipse i meant one half of an elipse,ie a bisected elipse along its longest length.

[gaiatechnician]

I am doing a compound parabolic dome mold at the moment and I am using a template attached to the center of it and it works! I do not think this type of template will work with a dish but it worked better than i expected with a dome. (So I tried your idea).

Video will appear soon. I will make the dishes on top of the dome. Dishes good for 3 hours of solar cooking without moving. Hopefully!

[gaiatechnician]

@fergawdsache The string and "mechanical mathematician" method is really easily adjustable. (So if you make your cob holder a little wrong, you can adjust things so that less cob is used.  And you know the focus right away. There are also times when you do not make a full parabolic dish or you make one longer on one side than another. Again, this can more easily be obtained with this method. Thanks Brian

[alanmcrae1]

Very cool! Please continue videoing your project as it progresses and let us see what happens when you start it up. QUESTION: Will you be able to measure the temperature at the focus, perhaps with a meat thermometer? Again, thanks for sharing your creativity with all of us.

[gaiatechnician]

I have used solar funnel cookers for almost a year to steralize all the soil for my seedlings this year and I use a thermometer.

I boiled water. This one has much bigger surface area and much smaller focus so I am sure there will be not problem! (As long as the disk of cob does not break when i move it!)

The really cool thing is my little gadget for making a parabola. More videos will come!

Brian

[gaiatechnician]

I have 2 new videos now. one abour applying the foil and one showing the "mechanical mathematician" which makes it easy to make any parabola you want! This was my best solar cooker so far.

I used it to steralize a lot of soil for seedlings.