Thread: Making large reflector

Originally Posted by peapea

Hi all,

Hope it is OK to ask you even if this is not about cars...

I would like to make a (24" diameter) ringflash for my SLR camera, much like: http://www.makeshiftphoto.com/budget/ringflash.html
My challenge is making the reflector, since I can't get the kind of trays they use on the website here in Norway.

The only thing I can think of making it from, is either paper mache or fiberglass. I would like to make it nice and rounded, with the inside shaped like a "U".

I don't know a thing about fiberglass (maybe I should stick with paper mache, he-he). On TV I saw a designer making something for a car. He first made the shape out of some foam, cutting and sanding it to shape. Then he used some fiberglass mat looking much like what they use at hospitals now (on rolls though, instead of plaster). As I remember, he dipped the mat in water before quickly molding it on top of the foam shape/mold. It dried hard. Something like that sounds real easy to use, but I doubt I can get mats like that. Ordinary fiberglass might be easier, should be able to get something at an auto accessory store.

Could I make a mold out of e.g. the foam stuff they use for dry flower arrangements, expandable building foam or maybe a huge styrofoam "O" made for (Christmas) ornaments? Then cover it with plastic, and apply the fiberglass directly on top? Would I need to cut the fiberglass into strips in order to be able to shape it nicely? If so, maybe I could just get a few rolls meant for medical use, apply it around the mold and spray it wet? Then maybe apply resin to make it nice and smooth (many layers)? Then finally sand it before painting the outside and lining the inside with aluminium foil or something like that? Are there different kinds of fiberglass mats, would the choice make a big difference (durability/looks)?

Would the fiberglass be strong enough to carry quite a bit of weight (camera/tripod), or would some reinforcement be needed? If I use mats, would I need to apply several layers?

Hope this makes sense, not all that easy to explain when I have no clue...

Thanks a lot for any input, it is truly appreciated!

PP

Check this out

http://www.rcgroups.com/links/index.php?id=3550

Michael

Originally Posted by peapea

Thanks a lot, Michael! That was really useful! There's a store in town that I think is used a lot by people into model planes. Maybe they have this foam. If not, maybe I'll buy a tube of expanding foam to make the mold from. The advantage would be that I quite easily could spray it on top of a sketch. I just came to think about fiber glass wallpaper. That is real easy to find. I wonder if I could use strips of that. If not, I think that I could always find some rolls of casting tape (just found out what it's called). I saw some things on eBay too, amongst others an auction with a mat and microballoons, as is mentioned on that website you referred to. As long as it isn't too heavy, it might even pay off to get it on eBay and have it shipped here...

Again, thanks a lot, it is really appreciated!

PP

No problem. Good luck with the project. I have no experience with FG, model planes, or anything like that. But I have THOUGHT about it before.

Again, good luck.
Michael