What a timely thread, since I am currently considering expanding into the world of raft aquaponics very soon. I am doing my homework and reading all I can about folks different techniques and approaches.
My wife and I are hooked on Aquaponics and want to do more growing like this. I really appreciate this forum and all of you who contribute such awesome ideas, remedies and guidance to thos of us who are new to this.
I'm sure glad this topic got resurrected. I missed it the first time, and so happens that I'm making some wood rafts right now. I have commercial lettuce rafts that float, made of 3 lb EPS foam, 2' x 4' x 1" thick, and 18 molded holes on 8" centers, made by Beaver Plastics in Canada. They cost $6 each, which is cheaper than the blue board I was quoted (cheap 1 lb density), and an unsung benefit is that the holes are molded, and resist root penetration. But, plastic is still plastic.
So, I made some experimental wooden rafts from redwood 1 x 12's, because I have both redwood and a sawmill on my property. You can't get more local and sustainable than that. They are only 2' long to fit my application. I clamped 5 together and drilled them all at once with a thread drive auger bit, very easy, took about 15 minutes to drill a total of 150 holes. They will not rest on water, but on ledgers, and I'm hedging on doing a partial flood and drain under the rafts from a bell siphon set to break half way down. To seal the wood, I'm going to try half of them dipped in hot wax. The other half I'll dip in epoxy. I start my seeds in spongy plugs made from Douglas Fir bark and a polymer, similar to Rapid Rooters, but much cheaper. The plugs (about 3/4" square) fit just snug enough in a round 1" hole to stay put and not completely seal the air flow. I'll shoot some pics soon.