Weight calculations

[Chalkbrd]

I'd like to know if my weight calculations are sound (based on US units).  I'm trying to determine how much weight my system will be so I can make sure I have sufficient support for that weight where I want to put it.

If I have a 2' x 8' x 1' grow bed, that would be 16 cubic feet, which would mean approximately 120 gallons.  I read somewhere that a 50 liter bag of Hydroton weighs about 65 pounds.  120 gallons would be about 454 liters (I'm rounding numbers).  If 50 liters weighs 65 pounds, then 454 liters should weigh 590 pounds, is that correct?

Here's where I'm a bit uncertain.  A gallon of water weighs 8.33 pounds so if the 120 gallon GB was completely filled with water, it would weigh 1000 pounds, but filled completely with Hydroton, it's only 590 pounds.

Does Hydroton weigh that much less than water?  If so, why doesn't it float, because it's porous?  Is it possible that the weight I found for that amount of Hydroton isn't accurate?

Then, in reality, how much weight will a GB filled with both Hydroton and water be?

Obviously it doesn't have to be perfect, but I'm kind of a numbers person and was wondering if I'm figuring these things correctly.  I do need to have a close approximation, though, to make sure my container will be sound as well as the support it will rest on.

Thanks in advance!

[Brad]

Right, Hydroton=Clay, Look at the shipping weight. Light weight.

Drop it from your calculation because there is little holes so they fill up. Or float.

[Chalkbrd]

So essentially just go with the weight of the water and ignore any weight from the Hydroton?

Brad said:

Right, Hydroton=Clay, Look at the shipping weight. Light weight.

Drop it from your calculation because there is little holes so they fill up. Or float.

[Brad]

Right if you want to be more specific, you can subtract the shipping weight. Water - Fired clay = Weight. But if you are worried about that much, then water is 8.328676 at 60 degree F at sea level LOL. Sweat the details. But seriously we are talking serious weight here.

[Chalkbrd]

Okay, thanks.  I'm working on a kind of different type of material for a grow bed so I needed to plan for what kind of weight it was going to need to contain.  I'm going to plan on about 1000 pounds for a bed that size.

Thanks!

[Brad]

Here is a fun with excel for AP

 

[Adam McMillin]

There is an issue in the math for cell D22.   The forumula should be =(A22*((B22/2)*(B22/2)))*C22 volume = area x depth and area = pi x r^2 not pi x d^2.  I know its been almost 3 years since this was uploaded and I did find it useful.  Just found the one error.

Brad said:

Here is a fun with excel for AP