How can u mount one thousand 1 sq inch mirrors on a 3 feet diameter parabolic dish?

Question

It's for a project, and we have a $200 budget, not including the mirrors, and i'm having logistic problems...i've thought about distributing them in a flat surface and adjusting the angles, but my teacher (for the heat transfer class) wants a perfect parabola so that all the light focuses on exactly one point, capturing the most radiation in the area of the 3ft diameter circle. The other method could be spinning a newtonian liquid (it forms a real parabol) and letting it solidify while it's spinning, then use it as a mold, then i could use that mold, fiber glass and resin to make a parabol then cover it with a reflective surface. Parafin could work but i dont know if it will keep the parabolic shape when it's cooling, although the spinning liquid behaves like a solid (when speaking about inertia)

well i how u can help me xP

Answer 1

this previous poster is correct

the hanging string is called a caternary

you might be able to google that and find some helpful discussions

Answer 2

The simplest answer is to shop for a surplus radio antenna in which has a parabolic form.  

  If you want to try the spinning thing, I would consider plaster of paris, although a 3' disk would be fairly heavy, thus you might have to use a motorized pottery turning table to handle the weight.  You would be doing it in a round pan and while deep pans in smaller diameters (oil drain pans I have used), all the larger ones I have seen are shallow for catching water under hot water heaters.   You might pop rivet a collar/wall, around the larger shallow pan to avoid having to work up a curved seam.  Of course, the plaster could stay in the pan after to support the large disk.  You could mold fiberglass on the plaster or dry the plaster and glue directly to it.  E6000 would probably be a good glue in either case.

  

Answer 3

I'm not sure how close it is to a perfect parabola but a string hanging between two points form an arc that happens to be a perfect curve for use in building arches (and it probably is a parabola).  A loose surface might form a reasonable parabola if hung inside a circular hole.  You could try making a superstructure by hanging strings inside a 3 ft diameter circle, spraying the string with somethign that will stiffen it (or coating them with epoxy), might make a good starting shape.  Interesting problem.  good luck