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What is the optimal design width for Deep Water Raft Construction? My concerns are ability to reach the plants; cost of construction; water issues.

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Hi Mark,

I am planning to build a raft system soon so I have some thoughts I would like to throw out and maybe they will be addressed along with your question. As for the length and width my plan (as of now) is to build the trough just bigger than a sheet of foam (4'x8'). Then cut the foam into 2'x4' pieces to make them more manageable. I figure I could lift that size and turn it around to work on plants on the far side. 

The question that I have right now is should the net pot extend beyond the foam sheet and if so how much?

Hi Mark,

We use Dow Blue Board 2" for our rafts, it comes 4'X8'...so 2'X4' works out nicely.

We use 6' Duraskrim in our rafts which fits perfectly in a 54" (exterior measurement) width DWC...subtract actual width of each 2"X4", 2 layers of 1/2" BlueBoard sides and you get about 50 inches of width....with a one inch airline along one side, it leaves about 49" for the rafts...just about right.

Make sure you save the holes that you cut out for your nets pots to use later to plug unfilled holes to prevent too much algae growth and you can email me at brokerned@gmail.com for a hot tip on how to cut the holes.

I also have netpots at a really cheap price.

Hi mark,

The average Raft has and internal width(I like to keep it within the 49-50 inch range)  to accommodate the 4 foot wide foam(4' W x 8' L sheets ). However you can make them smaller or even larger depending on your design.

Great idea on the boards. Did not realize the foam becomes water logged. Also I like wood better than foam for durability. What about optimal depth of the water? I think UVI people recommend 16" minimum. Also wonder about sloping the rafts vs. making them perfectly level ?

I like 4 foot wide beds all around at 4 feet most people can reach the center from either side. here are some new beds i Just built

Dow blue board has not gotten waterlogged in my system...at all.  I think the idea of using plywood in a very moist environment is asking fr trouble even if painted.  Plus what food safe paint would you use?

Use "ISO" polyester resin (fiberglass resin) around food production. NO polyester resins are actually water proof.  If it is above water as Bob suggests ISO polyester resin would perform well.  It is cost effective as well, ISO resin is just a few dollars more than latex paint when purchased in 5 gallon containers.   My buddy Marvin at Sticky Stuff will be happy to ship.

I also agree that the "suspended shelf" method is superior to the floating raft method in most applications.  If you are in a very large production facility it would be convenient to push the crop along the water channel.  However in home or small farm situations the constant height above the water with the accompanying root aeration makes good sense.

Jim,

In the "suspended shelf" method can you give me some general guidelines for the size of the air gap between the shelf and the water? Does it need to be adjusted during the growing cycle since plant roots start out small and then get bigger?  Also, I'm still trying to decide if the beds should have any pitch on the bottom floor?

Jim Troyer said:

Use "ISO" polyester resin (fiberglass resin) around food production. NO polyester resins are actually water proof.  If it is above water as Bob suggests ISO polyester resin would perform well.  It is cost effective as well, ISO resin is just a few dollars more than latex paint when purchased in 5 gallon containers.   My buddy Marvin at Sticky Stuff will be happy to ship.

I also agree that the "suspended shelf" method is superior to the floating raft method in most applications.  If you are in a very large production facility it would be convenient to push the crop along the water channel.  However in home or small farm situations the constant height above the water with the accompanying root aeration makes good sense.

Pitch on the bottom floor?  Not sure if I understand but since water will be exactly level if your beds are not then you will have one end of the bed with deep water and the other with shallow...this seems like a bad idea to me.  Has someone used the "suspended shelf" design on a large scale?

The pitch might be useful for draining and cleaning. Do raft systems ever get drained? For Maintenance?

Mark,

Believe me you want a level DWC. Yes, they are cleaned. We do it right about now since our weather is too hot to grow lettuce/greens in late August/early Sept.

We "move" the water to barrels and clean out the built up cocnut coir mixture from the net pots that have been deposited on the DWC bottom throughout the last year.

Actually use a swimming pool skimmer net with fine hole to get most of it before we "move" the water.

BTW, my net pots just barely extend beyond the bottom of the blueboard unlike the picture above. 

Where are you located?

Texas...near SAn Antonio

Ned Berndt said:

Mark,

Believe me you want a level DWC. Yes, they are cleaned. We do it right about now since our weather is too hot to grow lettuce/greens in late August/early Sept.

We "move" the water to barrels and clean out the built up cocnut coir mixture from the net pots that have been deposited on the DWC bottom throughout the last year.

Actually use a swimming pool skimmer net with fine hole to get most of it before we "move" the water.

BTW, my net pots just barely extend beyond the bottom of the blueboard unlike the picture above. 

Where are you located?

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