Best material & shape for a reflector

[Mr. Fosi]

I never did it because the guy at exoticfish.com never got back to me.

 

He told me that he had some 24"x24" pieces, but when I asked him about price with shipping to my zip he never replied. I emailed him two more times because I know that emails sometimes get buried, but he just never responded.

 

Also, the Chevy dealership that I was working at had no metal brake, so I would have been stuck doing it with 2x4s and a protractor.

 

I would still like to do it, but 1) I am too busy (grad school + wife + new baby = no time) to dig up another supplier and 2)my wife & I are so strapped for cash that I can't justify spending the $$ on it.

 

Great info on the ciritical angles, though.

 

Where did you get that info?

[mybuickskill6979]

dude congrats on the new baby man.

 

yeah i have abuddy who has 2 kids one years apart. work and his wife to take care of poor dude has no time. i'm like man thats crazy!!

[reefman23]

I never did it because the guy at exoticfish.com never got back to me.

 

He told me that he had some 24"x24" pieces, but when I asked him about price with shipping to my zip he never replied. I emailed him two more times because I know that emails sometimes get buried, but he just never responded.

 

That sucks... i dont shop there any more.

 

Jesse

 

Oh and that critical angle info is false... it doesnt reflect off the surface of the water, it bends down into the water... there was a scientific site that was posted somewhere... Ill have to find it.

 

Jesse

[Hekim]

McMasterCarr Supply carries mirror finished aluminum sheets.

http://www.mcmaster.com/

 

Its avaialble in a bunch of thicknesses for 12" x 12", 12" x 24" and 24" x 24" sheets.

[Robster]

Great info on the ciritical angles, though.

 

Where did you get that info?

 

Mr. Fosi-

 

I was picked up that data off a some paper it sounded about right, though a small margin of error is somewhat expected I have found a few different from 49 - 53. I'm not sure of which ones were, if any were performed/calculated in saltwater. Here's one of the links that calculated at 49:

 

http://www.glenbrook.k12.il.us/GBSSCI/PHYS...frn/u14l3c.html

 

 

 

That sucks... i dont shop there any more.

 

Jesse

 

Oh and that critical angle info is false... it doesnt reflect off the surface of the water, it bends down into the water... there was a scientific site that was posted somewhere... Ill have to find it.

 

Jesse

 

 

Jesse-

I have to disagree with your statement. The critical angle is the maximum angle at which light striking the surface from one material to a differing material will penetrate or refract into the material which will then change the speed and angle of the incident ray as dictated by the nature of how the material interacts with light. this has to do the refractive index of the material (refractive index= ability to slow down and bend light). Water has something like 1.33 R.I. So, Therefore any angle from 0 upto 48-53 depending on reference source, will allow the light to pass from the air into water. (refracted which WILL change the angle and speed of the light in the new material When the incident ray (incoming) is past (greater than) the "critical angle", the ray is reflected like the glare off the ocean as the sun is setting.

 

A perfect example of the phenomenon is demonstrated in a swiming pool. when the water is a still, you can see the bottom of the pool without any shadows to speak of (sun at high noon). When you drop a ball or some other object into the water, it will make a radiating ripples outward from the point the object hit the water. when you look at the bottom of the pool you see the shadow of the ripples on the bottom of the pool. This is because the ripples (tiny waves) have a nice arch to them. thus creating several different angles that the incident ray (the sun) is striking. on all points greater than the critical angle, the light is reflected off, and thus you see the shadow on the bottom of the pool.

 

Now there are many factors that can effect the critical angle like say a oily film on the surface of the water would change the critical angle.

 

I hope that gives a better definition of Critical Angle and Refraction/Reflection of light.

 

Cheers

-R

[Mr. Fosi]

Intro optics lesson.

 

I didn't check it for correctness because I have ~40 biology quizes to grade, but I did check out that McMaster-Carr link.

 

The cheapest 24"x24" polished ("mirror-like") aluminum that I found on that site was 0.032" thick. It comes in two varieties, each with different properties/tolerances:

 

Corrosion-Resistant Marine-Grade Aluminum (Alloy 5052)

Thickness Tolerance ±.002"

Length Tolerance ±1/32"

Width Tolerance ±1/32"

Part # 8202K51

$28.95/each

 

Multipurpose Aluminum (Alloy 6061)

Thickness Tolerance ±.0015"

Length Tolerance ±1/16"

Width Tolerance ±1/16"

Part # 1655T13

$41.53/each

 

A 12"x12" piece of "marine grade" of the same thickness drops to $8.08.

 

I can't visualize 0.032", but it would be easy cut and bend (maybe too easy).

 

Tin snips, a ruler, a sharpie, & a protractor would probably be the only things needed to bend proper parabilic-approximating relectors with this stuff.

 

They have an office in Atlanta, GA which would be good for me. I sent them an email asking for a price quote of the "marine grade", including shipping. I still don't have the $$ to get it right now, but it'll help me plan a future purchase.

 

I'm still not sure if that thickness is too thin... You don't want it to be too easy to bend because you may drop it on the floor or accidentally bend it out of shape during an install.

[Mr. Fosi]

Damn, they're quick! I already got a response:

 

atl.sales@mcmaster.com to me

 

McMaster-Carr Part Number: 8202K51

 

Item: Alloy 5052 aluminum sheet with #8 mirror finish, .032” thickness, 24” X 24”

 

Price: $28.95/each

 

Ships: today

 

 

 

Estimated shipping charge for this order is $5.

 

 

 

 

 

Catherine Egan

[Hekim]

If you use the .032" mat'l I would bend approx. 1/2" down the long sides back flat on its self, that tin of a mat'l is very sharp. The other bends that you make to form the reflector will stiffen the mat't quite a bit, I think it will work fine.

 

Please let us all know how it works.

[Mr. Fosi]

Good suggestion regarding sharp edges!

 

If I can find a way to fund the project, I will certainly post the results here. I wouldn't hold my breath, though since it could easily be after Christmas befor I have the $$ + time.

[Robster]

Good suggestion regarding sharp edges!

 

If I can find a way to fund the project, I will certainly post the results here. I wouldn't hold my breath, though since it could easily be after Christmas befor I have the $$ + time.

 

 

I know what ya mean dollars...few...free time....few......bills....many....work....too much!

 

So my visions of making sweet little reflector fizzled. since I'm stuffing 4 36watt biaxial tubes in my BC29 hood.....hhmmm...took up every sq.cm. of space cannot fit desired.....ringus! so not being happy with the less than super reflective surface from the nano-customs heat shield, I got a mylar silver mirror ballon from Party City! slice/dice....foam mounting tape then basically gift wrapped the heat shield with a layer of the mylar. much more reflective, though not my dream. Though I just finished cuttin and bendin' one of the original little pieces from the hood asembly to give a better reflection of the CCFL's I picked up for moon light and for a little splash in the UV range could prove interesting. Don't have my LUX meter yet so I couldn't do any before after measurements. What can I say getting a bit anxious had the tank now for little over a month....no water or rock, or sand etc..... It sits there taunting me....mocking my lack of time. Oh cruel tank that you are!

 

anyway enough drama. One day I'll be able to get the sucker up

Cheers

-R