I have read just about every post on Richie Sowa's spiral island and I want to do something similar in the Pacific. My goal is to float out to the great pacific garbage patch and establish a solar waste processing island to begin to clean up the debris.
Instead of using plastic beverage bottles we would like to use sealed 55 gallon drums to provide the buoyancy, and much of the frame for the island.
Six plastic 55 gallon drums can be used to make a floating platform 3 feet wide, by 6 feet long. Said platform can float 800 pounds of soil, plants, machinery, people, whatever. Two of the barrels will provide the 800 pounds of buoyant lift. Four of them provide the framing structure [by cutting each barrel along the ribs to create three six foot strips that will be folded in on themselves and welded up to create triangular beams, then those welded together to create the frame. These floating frames can be attached together using non corrosive chain, and have the island built atop of that. New frames can be partially sunk to make them easier to maneuver, then have air pumped into them to displace the water, capped, and sealed once they are in position.
We are most likely to use injection welding as we can build a parabolic trough mirror to create plastic welding sticks from the scraps of the barrels. Build a hot air gun to superheat the material to be welded and prep it. Then use the extruded plastic rods through what is basically a ramped up hot glue gun to reinforce the seam.
Another option for welding would be to build a gas torch and to build an electrolysis unit for producing the hydrogen to power it using salt water. This method would only want to be used for repairs or expansion as the electrolysis of salt water would produce chlorine gas as opposed to oxygen. [Unless we can build a massive solar array to generate enough electricity to split distilled water] A benefit to using this method is that the sodium hydroxide [lye] produced in the electrolysis could be used to make soap to cover personal hygiene while aboard the island.
I like the idea of plastic drums over steel ones because over time, steel corrodes and eventually, they would leak and fall free to the ocean floor. The only reason the plastic in the great pacific garbage patch is so invisible, is because the UV rays from the sun breaks down the plastic to this point. Without the UV radiation, the plastic would never decompose. [or at least take an archaicly long time to do so] We would block the radiation using the island itself as cover. Without the penetrating rays, the island could stay floating for 2000 years without maintenance. [assuming a massive hurricane didn't come through and try to tear it apart.]
In the event of a hurricane:
The buoyant drums would be contained in a framed box, preventing them from being washed out from under and away from the island in high wake. The idea is to make the island large enough to not lift up and over the wake like a boat, but rather to have the wake break on the shores and wash back off. Having the barrels in the cage is still a good idea, in the event that part of the island was to be broken off. It could be recovered through the use of shortwave beacons and be towed back to the main island using a tugboat.
The part we haven't figured out is what to use to build the frame of the island itself. If anyone has any ideas, they would be greatly appreciated.