Cooltube & loss of light ?

[bilgeweed]

I am thinking of making a cooltube for a 150W HSP lamp and trying to
figure out of this is a good investment or not. I recall reading a thread on the properties of glass and how it affects light/lumens but I can not recall the amount of loss.

My grow area is very challenged for height, so a reflector will be designed
as the major portion of the top. If one has a reflector above the tube- some of the reflected light will go through the glass several times and with each pass a slight loss of lumens occurs. Should this loss be a major concern ?

I have seen a couple of cooltubes with a reflector placed inside the tube.
Might anyone have a report on this style ? Does it focus the light too much ?
Could this style be incorporated with a reflector above ???

Thx
bilgeweed

 

[Vern Equinox]

What are the grow specs and dimensions of the space? A small vertical grow may be just what the Dr. ordered...

 

[Sauce]

From what I've read, 6% is what the glass will cut down on. However you make up for that space easily with how close the light can be placed to the plants.

If you can, get the glass on the inside of the glass. I'm currently using a cool tube with no relfector but I plan on cutting off a piece of a reflector I'm not using and put it in the cool tube.

 

[Vern Equinox]

If you can, get the glass on the inside of the glass. I'm currently using a cool tube with no relfector but I plan on cutting off a piece of a reflector I'm not using and put it in the cool tube.

Hey Sauce, can you elaborate please? Thanks.

 

[bilgeweed]

Vern- I have admired your vertical grows for some time now.
You surely make the best use of space - very impressive !
As much as I would like to try a vertical grow my space would
not allow it. I truly grow in the bilge -- and only have a total
of 31" for the cab. In my case I found that a 25 gal galvanized
garbage can fix perfectly.( pretty much fireproof as well)
I mounted one of the Home depot 150 hps security lights 1/2 the
way into the top. (this keep much of the heat from the ballast/case out)
I then cut a large door w/hinges in the side. Mounted a 4" axial fan
on the top sucking hot air and a similar fan pushing fresh air in from
the side of the can. This gives me only 26" of vertical space to the
glass. Because of this limitation I pretty much must grow in soil. Using
a pot that is 7-8" high the plants can not be any taller than 16".
This make the tops a couple/three inches from the glass. My ambient
temps are from 62-75 depending on time of year and water temps.
Most of the can stays a few degrees above ambient but I have a
significant amount of radiant heat from the lamp. I was thinking
and hoping a cooltube may help with this radiant heat- will it ???
(my present setup has worked for years-I'm just trying to make it better)

So- if a 6% loss is experienced on each path through the glass,
some of the light may pass through three times - correct ?
That may lead to a significant loss of 18% on THAT light. But
what percentage of total light will be effected in that manner?
Just a wild guess of maybe 25-30% - does that sound close ?
I'd still like to hear from someone that is using a reflector inside
a tube. How is the footprint of light? and is the radiant heat
lowered using a cooltube ? This is especially of interest to me.

THX
bilgeweed

This was my first grow using bottled nutes (F.F.) rather than mixing
a complete soil. Unfortunately I over did it a little but they are getting
nice an frosty as we speak.

 

[Sauce]

I actually don't know how to get a reflector inside the glass. The best way I can think of would be to attach a piece of wire to the reflector and bend it around to hold on to the glass. On the side with the ducting you would need to put the wire piece on before you put the ducting on, otherwise there wouldn't be a way to pull the wire through around the glass.

That is correct that the light would be cut down 3x if the reflector is on the outside of the glass. However it is not 18% of the light. For one thing the relfector is only going to be on one side, so here's how I calculate it:

100% light / 2 = 50% = half light emitted from light (light that would hit reflector)
50% - 6% - 6% - 6% = ~41.5% of 50% possible.

But if reflector is on the inside:
50% - 6% = 47% of 50% possible.

But what percentage of total light will be effected in that manner?

What do you mean? With air loss included?

And the cool tube will help radiant heat a lot. I can touch my 250w hps bulb. Not just the end of the bulb either.

Btw if you're interested there's also tempered polycarbonate tubes. They are harder to find (must be ordered from plastic companies) and more expensive but only cut down on 4% of the light. Personally not worth the trouble for such a small difference. Both the 6% and 4% numbers I found in a OG thread where some one was interested in buying poly tubes.

Also awesome setup Vern!

 

[bilgeweed]

THX Sauce-

"100% light / 2 = 50% = half light emitted from light (light that would hit reflector)
50% - 6% - 6% - 6% = ~41.5% of 50% possible.

I think you may be close with these calculations. But I'd guess that
50% of the light does not go through the glass 3X . No matter how
you cut it there is a pretty good reduction of lumens. I may have to
rethink this---- with a 150 w I can't afford to loose much.

"But if reflector is on the inside:
50% - 6% = 47% of 50% possible."

The inside reflector I have seen is something like this-
http://www.4hydroponics.com/lighting/rhyvct.asp
I would think the reflector is on the inside - No ???
If not it should be---------------
The above unit is 6" dia. where a "bake a round" is close to 4"
So- I'm trying to imagine how a 4" dia tube w/inside reflector
would dispurse the light------ I need a "flood" not a "spot" beam.

I was also thinking of taking a large dia. (about 13") stainless
steel mixing bowl. You know the real shiny ones- Cut a couple
3" holes for ducting/light mount. Adhire a piece of glass on the bottom
of this bowl and mount it to the top of the cab. This parabolic shape
may through off a better light footprint for me --- ??????

Glad to hear the tube had greatly reduced you radiant heat - just
what I'm after.

bilgeweed

 

[Sauce]

By that pic it looks like that reflector is on the inside, however I've seen some that are not, so be sure to check if you plan to buy one.

I've seen many people who have used a bake a round and they work very well. I uesd a candle holder from Target for mine ($6). It works well but the glass is not very thick.

The metal bowl idea would probably work, but making it could be a little difficult and the reflectivity is probably not the best. The best shape of reflector depends on your footprint.