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Compound parabolic solar cooker from petal template. Want to try one?

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Posted by brian white on December 30, 2008, 11:48 pm
I made a compound parabolic solar cooker in September 2008 and it worked
well. Most people would lot like to repeat my method (I made a Dome and
used it as a mold) and they asked for a template instead.
The first link shows how to make a mold for a compound parabolic solar
cooker (using technical drawing to design the "petals" to stick together
to make the reflective dish).
and the bottom link has more details about what they are and how they
work. Perhaps some of you would like to try? I have no good sun till
about march because my lot slopes to the north.

Thank you
Brian White

Posted by Father Haskell on December 31, 2008, 1:50 am

dish).http://www.instructables.com/id/Compound_parabolic_dish_making_a_temp ...

Is this the same idea as used to design Direct TV dishes?
I see these things on the curb awaiting the trash company.

Posted by brian white on December 31, 2008, 10:19 pm
 No it has a different curve to it. Thanks
Father Haskell wrote:

Posted by Father Haskell on December 31, 2008, 10:27 pm
Multiple focal points?

Posted by brian white on January 3, 2009, 5:20 am
 Nope, it has a focal area. A parabolic dish has a focal point but only
when it points DIRECTLY at the sun. Get a concave mirror or a magnifying
glass and  make a focus with a light in your room or with the sun. Now
twist the glass or mirror a bit to model the sun as it moved for an hour
or 2. No more point of light! It spreads into a focal streak! The idea
with a compound parabolic dish is to start off with a focal "ball"
(Perhaps as big as a soccer ball) and 2 hours later still have the same
focal "ball"! Place a cooking pot the same size as the ball in the focal
ball area and you are in business.
  Although you do not get the same concentration as a dish, you get
something much more usable. Now you set up the dish, stick on you food
and come back to a cooked meal! This is not possible with a parabolic
dish because you have to move it so often.
I do not know the exact shape of the "Ball" because I cannot do the math
but I am pretty sure how big the area that contains the "ball" is. It is
called a "Caustic curve" and very complicated to model exactly.
Father Haskell wrote:

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