Construction of the DWC rafts

Well, spring is in the air, and you know what that means....it's time to expand the system and add the Deep Water Culture rafts to the grow beds. So I have purchased most of the materials at my local building supply chains, along with the 12mil B/W Poly Scrim liner material on-line from Americover.com. I based part of my design on the UVI systems, while also making it scalable using off the shelf plumbing parts bought locally.  For the raft side walls, I went with Hardie fiber cement plank 12"W x 12'L. This is very water resistant, and rot/termite proof, so it should be long lasting and it was comparable in price to ACX plywood. ACX plywood would have to be cut into 1ft strips while the Hardie plank is already the correct width. I went with PT 2"x4"x8' for the side rails for durability and weather resistance, with a 1"x 2" furring strip top rails to negate wear on the liner. The assembly process was pretty straightforward and I was able to complete construction of each raft, less the liner installation, in a couple of hours. I measured off an area that was 25ft x 25ft and placed woven weed block down prior to raft construction. I laid this in a cross hatch pattern, double layer which was approximately 1100 sq ft of material and attached it with ground pins. I will be adding edging material later and filling in the area with expanded shale or gravel.

Here are a few pics of the raft construction process, note that I used all galvanized fasteners for construction.

 1"x2"x24" PT stakes were added as side support and to negate any shifting, these were attached with 1/4"x3-1/2" galv. carriage bolts w/nuts and washers.

Since I have two aquaponics systems, I am building two rafts per system for a total of 4 rafts. Each raft is 4'W(actual is 51")x16'L, this provides me with 256sq ft of growing space, with a an average of 30 plants per 1sq meter (10sqft), I should be able to have approx. 768 plants along with those in the grow beds. I also intend to add additional  4'x4' DWC rafts inside the greenhouse. This should up the count to approx. 1000 plants between both system. Of course, once the rafts were finished I had to paint them to match the greenhouse and our home.

Based on my previous design, I am using 2" PVC to connect the beds on the far end using 2" DWV 90deg EL's and 2" non caulking floor drains. The floor drains have an internal rubber busing which can be tightened down on the 2" PVC pipe and if necessary loosened later for removal or expansion.

The floor drains require a 3-1/4 hole saw which is a perfect fit. The only problem I ran into was that the concrete board pretty much destroyed the hole saw after 4 holes...so I will have to buy another one when constructing the second set of rafts..which are kind of pricey at $17 a pop, but hey, it for a good cause, so enough about that. In the pics above I used a scrap piece of board to test the size and fit of the drain...can you say perfect.

Now on to drilling the holes in the raft beds.

 These holes were placed at 5" from the bottom and 25-1/2" on center of the Hardie plank. Remember, I build the rafts 51" wide.

And with that, I end this post as it has now been raining for several days, and I will need to continue this after I have progressed further on my installation of the DWC rafts, hope you find this helpful.