Diameter of Single Bulb Vertical ScrOG calculations

C

Can of Bliss

Member

• Dec 11, 2016

• #1

Greetings,
We have all heard the 50 watt per square foot rule, but when you conform your plants to the light rather than conforming your light to the plant things get more complex.

Just calculating the watts per square foot of screen on hexagonal v scrog grows posted here, it would seem 35-45 watts per foot works great.

BUT, that's not the full picture. Light doesn't come out of a bulb in an even cylinder. If you map out a specific light intensity from an HPS it looks almost apple shaped, a slightly stretched sphere with dimples as light doesn't come out of the electrode ended of the arc tube.

Anyway, I was hoping to put together a formula to calculate screen size for various lights. What light/screen combination have you used and how did it work? What logic did you use in design sizing?

 

Q

Qqqqqqqqqqqqq

New member

• Dec 11, 2016

• #2

Hopefully someone chimes in. I'm working on something and have the same question.

 

C

Can of Bliss

Member

• Dec 12, 2016

• #3

So I tried to break this down mathematically they way I've been mentally picturing it. There are undoubtedly flaws in my model and math. Please ask questions so we can get this to something useful.

This is how I modeled the output of an HPS bulb

Numbers for a 400 HPS (because that's what I have around)

And work that out:

So a diameter of about 18 to 23 inches seems viable. But let us remember the more sphere like shape this is based on. Not a tube diameter, but the widest point of a screen ball.

 

C

Can of Bliss

Member

• Dec 12, 2016

• #4

And I already spotted an error in my math. The .3 should have been multiplied not divided the radios. I'll have to redo that.

Under further consideration the double bulb design sure makes a better cylinder grow than one. It would be nice to figure out the optimum spacing. For my personal applications I'm thinking of rounding the top an bottom (though this may be foolhardy).

 

W

watts

ohms

Veteran

• Dec 12, 2016

• #5

bruh

 

Q

Qqqqqqqqqqqqq

New member

• Dec 12, 2016

• #6

The formula must include ambient temp, variable for wattage, a standard for heat dissipation, and a standard for light emission. Lost cause.

You'd better off comparing notes from vert people across the various boards.

 

M

Miraculous Meds

Well-known member

• Dec 12, 2016

• #7

I use 600w hps bulbs. Ive found that about 20 to 22" from back of plant to the light, and about 8" from the front of the plant to the light works best for me. Also I shape the canopy so that the buds directly in front of the bulb are the furthest away, while the buds above n below the bulb can angle in a few more inches.


I use 2' x 4' screens. 4 plants/screens around 2 600w bulbs stacked about 1' apart.


Id recommend ichabods dimensions for 1ks stacked. I believe its 27" from back of plant/screen to bulb for 6 screens, at 2' x 5'. Hes got a great thread to help u get started, if this is ur choice for style of grow.


https://www.icmag.com/ic/showthread.php?t=242646

 

K

king oscar

Member

• Dec 12, 2016

• #8

While the math is really cool, just do what you feel man. Do what your experience tells you.

There are going to be unknown variables differing light requirements etc.

 

C

Can of Bliss

Member

• Dec 13, 2016

• #9

Miraculous Meds said:

I use 600w hps bulbs. Ive found that about 20 to 22" from back of plant to the light, and about 8" from the front of the plant to the light works best for me. Also I shape the canopy so that the buds directly in front of the bulb are the furthest away, while the buds above n below the bulb can angle in a few more inches.


I use 2' x 4' screens. 4 plants/screens around 2 600w bulbs stacked about 1' apart.


Id recommend ichabods dimensions for 1ks stacked. I believe its 27" from back of plant/screen to bulb for 6 screens, at 2' x 5'. Hes got a great thread to help u get started, if this is ur choice for style of grow.


https://www.icmag.com/ic/showthread.php?t=242646

Click to expand...

Thanks so much! That's very helpful, I look forward to analyzing your setup. Sound like you really let your plants lean in. When you say your bulbs are 1 ft apart, is that from bulb tip to bulb tip, or arc tub center to arc tube center? Above and below the bulbs, can you give me any measurements (or rough estimates) of where the light goes from "happy useful" to "not so great"?

Ichabods thread is really great. I've at least skimmed every post in it. It's why I joined this community.

 

C

Can of Bliss

Member

• Dec 13, 2016

• #10

king oscar said:

While the math is really cool, just do what you feel man. Do what your experience tells you.

There are going to be unknown variables differing light requirements etc.

Click to expand...

I get what you're saying, but there are few things I enjoy more than puff c99 then some math. It's not going to be perfect, and any calculation you do, you should always do with an understanding of how accurate it is while at the same time understanding how accurate you need to be for the application. I'm fishing with dynamite.

But I feel like it would be beneficial for the vertical community if we had a better measure of what works. In horizontal land everyone knows you multiply your square footage by 50 and then put that much light over it (+ or - 30% if you want arguments).

I hope from our combined experience we can put together a "rule of thumb" to make vert growing less of an advanced thing.

I've pushed the math for one vert scrog, but didn't have the plant mass to properly cover the screen (a problem that seems common, though mine was extremely pathetic). I have yet to see it but I suspect that this grow method is the best known if applied property (maybe impossible).

So anyway, if you grow vert, what is your setup and what is the line between useful and not so great light in all directions using arc tube(s) center as a reference point?

 

W

watts

ohms

Veteran

• Dec 13, 2016

• #11

In the near future I plan to do a vert scrog like Ichabod and MM. It is the best way to get maximum yield per plant with the circled "doughnut" method. Ichabod says to fill your screens about 75% with "branch tips" when going into flower mode.

 

C

Can of Bliss

Member

• Dec 13, 2016

• #12

I'm going to put together an experiment with a bare bulb (and then 2) and a light sensor. With all the great info here, I hope to map out the shape of the best light off a bare bulb. Then design a screen around that. Then comes the real test (and my crappy growing skills).

I really should be working on my veg box right now, I'll be needing that sooner.

 

gr866

Active member

Veteran

• Dec 13, 2016

• #13

With this setup I can position the screens from 14" to 21". Will be running a 315W CMH on the top and a 400W HPS as the lower light.
Still awaiting seeds.



GR

 

M

Miraculous Meds

Well-known member

• Dec 15, 2016

• #14

Iput the bottom bulb on the floor, so bulb tip up, and hang the top bulb down. So both bulb tops are facing each other. I don't think their orientation matters as much as putting the bulb where it can be utilized to fill the canopy the best. In this grow design, I try to keep the thread side of the bulb a few inches below plant foliage. So the mogul is level with the edge of foliage. This keeps the bulk of light going towards the maximum amount of growth shoots.

 

G

God_Speed

Member

• Dec 28, 2016

• #15

So I'm trying a sort of micro Scrog. I'm using a 250W HPS with a "cage" of 60cm in height and diameter. I've got a lux meter and my readings are almost the same all over, but gonna do some further experiments.

 

M

Me2

Member

• Feb 8, 2017

• #16

I recall all this being tested in great depth on Overgrow many moons ago when the coliseums first came out. There were a few good micro growers using V-scrogs with low wattage bulbs around at that time too. If you`re lucky someone may have kept the info.

 

G

ganjourno

Member

• Feb 8, 2017

• #17

So 40-45W per square foot of canopy is pretty much the goldilocks zone for vert. My setup is very similar to Ichabod Crane's. I end up with an inner canopy cylinder approx 42" diameter and 72" high, for a total canopy surface area around 66 square feet. I use 3000W of HPS down the middle so that works out to 45W per square foot. Not sure if you need a metric other than 45W per square foot.

 

Boyd Crowder

Teem MiCr0B35

• Feb 12, 2017

• #18

Ill just leave these here:

two 600s in a cooltube with venting from outside the room = cool to touch its literally about 106-110F at the glass surface , im estimating im getting 100k lumens at the first buds in the donut