Need input on my DIY canopy design...

[tang_man]

I'm going to be putting in 2 x 250w MH's very soon. Because of this, my current canopy will no longer do. It only has an outer height of 8".


- The new canopy will be 16" in height.
- I'm using 1/2" Pine, Outside will be stained black
- inside will be weatherproofed, and then coated with reflective Mylar (using spray-on glue)
- The back will be half-open.
- 4" Fans on each end of the canopy.
- Front 5" of Canopy will swing open onto itself (for major access), using a piano hinge
- Front will also have 2 cupboard style doors for quick access for feeding/etc... (not yet on design)

I designed a schematic yesterday morning, and now I need input on anything I may have forgotten.

My Design (http://myhost.no-ip.com/my-tank/canopy.gif)

Thanks!

[tang_man]

I've been told that Pine is a soft wood that will warp with humidity.

I wanted to have a real nice outer finish on the canopy. Am I stuck going with plywood? And if so, 1/2" or 3/4"?

Thanks!

[johnfish]

Hi Tang_man,

Yeah, I think the pine will warp unless it is coverd with several coats of oil paint. Don't use latex, the humidity goes right through it. I don't know about stain. They use it on decks and fences, so it might work. Clear verithane might be a good choice if you want to see the wood grain.

Weight is another consideration. Are you using the tank to support the canopy or will it be suspended from the ceiling or something?

The other thing about wood is that is is flamable. With 500w of metal halides under that big wooden box, you are going to get a lot of heat build-up. I would consider the ventilation carefully. A fan is probably mandatory as is a good reflector on the inside.

I build a DIY canopy out of aluminum sheet, angle stock and pop rivets. It is fairly light, flame-proof and actually helps to dissipate the heat by re-radiating it. Aluminum is a conductor of heat, whereas wood is an insulator. Carefully planning of the air flow and a kick-a$$ fan resulted in very little extra water heating despite running two 400w bulbs about an inch apart.

Just some thoughts. Good luck!

John

[tang_man]

Thanks for the quick reply! Going through your message, I have some questions:



Originally posted by johnfish
[B]Hi Tang_man,

Yeah, I think the pine will warp unless it is coverd with several coats of oil paint. Don't use latex, the humidity goes right through it. I don't know about stain. They use it on decks and fences, so it might work. Clear verithane might be a good choice if you want to see the wood grain.


:( ok, so much for Pine... Should I then go with plywood?
1/2" or 3/4"?



Weight is another consideration. Are you using the tank to support the canopy or will it be suspended from the ceiling or something?


I've considered the weight, which is why I was going with 1/2" thick wood. The canopy will be supported by the tank.




The other thing about wood is that is is flamable. With 500w of metal halides under that big wooden box, you are going to get a lot of heat build-up. I would consider the ventilation carefully. A fan is probably mandatory as is a good reflector on the inside.


In terms of fans, what is the suggestion here? Mounting 'em on top, or on the sides? As outlined in my design, I'm going to be using 4" fans. I'm getting these MH's used from a friend, who had them in a wooden canopy. As far as a reflector goes, I was going to suspend the MH's about half-way down in the canopy (which means ~ 5" between the actual bulb and the top of the canopy, and ~6" between the bulb and water)... I was going to use mylar throughout the interior of the canopy to reflect the light. The previous owner had these MH's with mylar in his canopy as well, and has since upgraded to 400w radiums, and is still using Mylar to reflect the light. No spider reflectors, nothing.



I build a DIY canopy out of aluminum sheet, angle stock and pop rivets. It is fairly light, flame-proof and actually helps to dissipate the heat by re-radiating it. Aluminum is a conductor of heat, whereas wood is an insulator. Carefully planning of the air flow and a kick-a$$ fan resulted in very little extra water heating despite running two 400w bulbs about an inch apart.


Thanks for all the input..
How does everyone get away with building wooden canopies then? There must be a trick to it...

[Dman]

Tang,
See if AJ can send you some pics of the hood I built, sounds almost the same as what you would like to build, just a foot shorter.
AJ?
Dman
:spin:

[tang_man]

Dman,

Thanks for the lead... I'll ask him about his canopy..

Out of curiosity, I'm now at a loss as to what wood to build my canopy out of. What wood had you selected?

[johnfish]

The pine might be fine if you weatherproof it. Plywood won't warp the same way because the grains are laminated. Plywood is actually stronger I believe and won't split. Not as pretty if you want natural wood grain. I built a flourescent canopy once out of 1/4" plywood and 1"x2" bracing. Looked a bit rough, but worked. Oak would be lovely.

I would try surfing the net and looking at various canopy designs. Lots of people use wood quite successfully. Careful attention to thermal design is needed for safety, however.

I just think aluminum is a superior material for this application. It can get pretty darn hot without burning and works as a heat sink to radiate the heat. It also gives you electrical grounding. Looks like a piece off an aircraft though.

You might be more comfortable working with wood. I have built a lot of high powered radio transmitters using alumimum with pop rivets and I am familiar with this method. It was quite a metal work project with a ton of drilling and sawing.

I would go for an aluminum reflector between the bulbs and the wood with several inches of air space above the reflector. Most of the radiant heat will be reflected away from the wood and air flow from the fans will cool the air space. Some vent holes above the reflector might be a good idea. You don't want it to burst into flames of the fans pack it in.

Mylar can burn if it is too close to the bulbs. Might be okay for the front and back surfaces if the spacing is sufficient.

I mounted the two bulbs vertically about 1" apart. Vertical burning is supposed to give you longer life and a slightly higher colour temperature. My canopy is 12" high. If you mount the bulbs horizontally, you can get a lower profile.

I used one big fan in the centre of the back panel blowing right on the bulbs with banks of air holes at the sides for the exiting air. I made the total area of all the holes about twice the area of the fan intake to allow for the expansion of the air after heating.

The wooden canopies I have seen on the net put the fan(s) on one end and a grill or lots of holes at the other end. This give a strong linear air flow from one end to the other. Put the sockets towards the fan as most of the thermal mass is in the sockets.

Check out the DIY articles on the net. Be carefull. It is quite possible to burn down your house and/or electrocute yourself.

Cheers:)
John

[Duce]

Just want to jump in since I am planning my 2nd tank (30G)
I want to get a 175W MH retro kit for it...and since I do not have a canopy for it now I would need some research...
Looking at the posts...am I correct that my light should at least 8-10" off the surface.....and 1/4" plywood would be a good material.....and I should put a spacer between the reflector and the hood.
Would I need a fan?

[johnfish]

Tang_man,

The thicker the better, but you have to also consider the weight. You can't run screws into the edges of plywood or the layers will split apart. If you use plywood you have to use some kind of bracing anyways (like 1"x 2" pine). With the bracing, 1/4" ply is plenty ridgid enough.

One side finish plywood doesn't look too bad if you can pick a nice piece without joins. Hardwood veneer might be a good option if you want a nice piece of furniture.

Duce,

I don't think you need 8" - 10" spacing from the water. 4" or 5" should be plenty. You just don't want water splashing right on the hot bulb or it will break the envelope. A bit of spray is okay, you just have to wipe the bulb once in a while.

The power delivered by the bulb decreases by the square of the distance (i.e.- double the distance equals one quarter the power) so you want it as close to the water as safety permits.

A reflector between the hood amd fan is a good idea. Radiant heat from the bulb could bring the surface of the wood to flash point. An aluminum reflector will reflect most of this heat and dissipate the rest.

You definately need an air space between the reflector and the wood.

A fan is a really good idea too. Most people use those nice quiet little fans from Radio Shack. I got a real electronic equipment fan. I think it is lke 200 CFM of something. Keeps everything nice and cool, but it is pretty noisy. My set-up is pretty industrial though.

Here's some links to DIY canopies:

http://www.saltreef.com/projects/aqcanopy.htm

http://saltaquarium.about.com/gi/dynamic/offsite.htm?site=http%3A%2F%2Fusers.rcn.com%2Freef 101%2Fdiyhood.html

http://w3page.com/fishline/gif/hood.gif?

http://defcon200.bizland.com/aquariust/id12.html

Cheers,
John

[Ocean Images]

Tang_Man, I just finished a cabinet for my 180...I used 1/2" ply with a oak veneer, it turned out great! You can buy plywood with a pine veneer, it will look just like a solid pine canopy :)
1/2" thick is more than enough for what you are doing, its very easy to work with....someone was saying you have to watch the screws don't split the wood, that was a good point! I would use 2"x2" pine as an inner frame for your canopy, this will give you something to screw your ply into.

I paid $54 for a 4x8 sheet of the plywood (oak) so its a little expensive, measure twice cut once!

Good luck
:cheers:

[tang_man]

Thanks for the great info everyone!!

I will soon be building this thing, and will take pictures along the way!

1/2" ply, with internal bracing will be the nature of the beast....

[mouse6196]

Your canopy is almost exact to mine. I'm running a 400 Watt MH in mine and the heat is not a problem. A few add-on's I've done since I finished. On the top piece, right above the lights, I found the wood to get too hot. I took 2 ceramic wall tiles, and placed spacers between them . I spaced them with stainless steel washers and construction adhesive. This is like washers sandwiched between tiles. This made a heat barrier between the wood top, and the bulb. I attached these using stainless clips, used to hold mirrors on a wall. Total cost, about $3.00. Now the wood near my bulbs is not hot. I used glossy white tiles. (home depot .65 cents each). I did not use Mylar as it did not hold up to the heat of the MH bulb over time. I simply painted the inside of the whole canopy Glossy White. I have stonys and other SPS corals all doing fine int he tank. Another thing, with the fans on each end, have one blowing in, and one out. This cools the area around the bulb. My MH is on 9-10 hours a day, and the tank temp doesn't budge. Email me if you want pictures etc. They're getting developed as we speak.

Oh yeah, there is only 3" clearance between my MH bulb and the new tile heat deflectors....it can be done.

:cheers: