building a system 8x4 feet

[GpsFrontier]

Hello animus_divinus,
You mention your looking to go as simple as you can, but from what I here your plans are overly complicated to me. I think it's mostly because you are trying to grow everything in one system. As I mentioned in the other forum, I would definitely use different systems for different plants for various reasons. Here is some examples of simple setups that I have built for both small as well as large plants.

Here's a simple water culture system I built for growing lettuce,
http://www.hydroponicsonline.com/for...th-system.html
A water culture system is just about the simplest systems you can build, and this one cost me all of about $20-$25 to build. It's easily expandable to accommodate as many plants as you want too (as long as you provide enough air bubbles). But you can use a lot of different materials to build a slimier water culture system setup.

Here is a simple drip system that I built for growing large plants,
http://www.hydroponicsonline.com/for...w-systems.html
A drip system is the second easiest type of system you can build, and I simply wouldn't grow tomato's with anything less than 5 gallons of root space. This system only cost about $80 to build, and that includes everything (even the pump and growing medium). It is also easily expandable to accommodate many more plants even with the same pump, although I would use a larger reservoir.

Here is another simple drip system that I built as a makeshift system to hold some Mellon plants
until I was able to build their permanent home, but I didn't have the money to build it in time before they got to big to transplant. It would have cost about $150 complete with two 6 foot troughs and growing medium, a "A" frame trellis for the vines to grow on, and an in ground reservoir and pump to keep the nutrients cool.
http://www.hydroponicsonline.com/for...26-melons.html
I built this make shift system with all left over parts, but you could easily build the same thing with new parts for about $50 including a pump reservoir anf growing medium. You could also easily expand it to more than one growing container using the same pump for multiple growing containers. I use nothing more than regular tubing that I poke holes in with a hot paperclip to make the drip holes with. Not much simpler or cheaper than that. And you don't need to worry about clogged dippers or spraying heads.

Here is a drip system I built for growing root veggies using sand and perlits similar to what you want to use.
http://www.hydroponicsonline.com/for...en-onions.html
No mater what you use as a growing medium you will run into a problem if you want to use this type of a system to everything at once in. One of the biggest issues id harvesting the plants like lettuce that don't take long to grow. As much as you try you wont be able to get the entire root system out, and the roots will intertwine with the other plants, making pulling them up much harder also. But the roots that break off and are left in the growing medium will die and begin to decay. These decaying roots will feed pathogens and fungi that can cause root rot, and plant diseases for the plants left in the system. This type of thing is what I am referring to when I mentioned plant and system maintenance being much more difficult when you try to grow everything in the same system.

Here is another simple flood and drain system I built for growing medium sized plants, but can be used for smaller plants as well.
http://www.hydroponicsonline.com/for...rd-system.html
Again this system was inexpensive and yet easily expandable, even using the same pump. I would just increase the size of the reservoir depending on the type of plants used if growing in more than one tube. The larger the plants the more water they will drink up daily.

I prefer to use coco chips for a growing medium most of the time. It retains water real well, and is fairly inexpensive running about $10 for 2 cubic feet (assuming you don't need to have it shipped to you). That also makes it about half the price of perlite or vermiculite I can get locally that runs about $20 for a 2 cubic foot bag. As I do with my drip systems I like to use rock on the bottom of the growing chamber for weight, and to aid in good drainage. That also takes up space so I don't need as much growing medium.

P.S.
Anytime you use wood in an area where it will be subject to getting wet, you run the risk of mold and rot. So if you do so make sure it's completely 100% waterproof. Also from reading the posts in both forums, I think your underestimating the size of the plants. That will cause problems for you. But we all learn from experience, and that experience just helps us in the future.