Jeff Chan gave an interesting presentation at the recent conference about Seadrome, an ocean platform design created back in the 30′s as an airplane refueling stop. It was never built due to increased aircraft range, but the design still serves as a good example of how to build a spar platform for the open ocean.
Check out the [wiki page on Seadrome](http://wiki.seasteading.org/index.php/User:Jeff_Chan/Seadrome), and the [PDF of his conference talk](http://www.jeffchan.com/seasteading/conference/2009/seadrome/Spar_buoys_Clubstead_Semi_submersible_oil_pl.pdf). He focused on the common elements between Seadrome, ClubStead, and other designs, as an indication of how best to approach the spar platform portion of the design space. As with other talks, we’ll be putting this talk online later this year once the slides have been edited into the video.