I posted a design i made for a twin bike sailer here a few months back but it seems the thread is deleted?
anyway, there was some support and some hate, but i went ahead and built it for burning man it anyway figuring, at least it would be a two person bike. It actually worked really well and was a ton of fun, heres the story:
I built it in the dark on the playa after a week of building something much bigger, with an angle grinder and small MIG, so far from perfect, but certainly good enough.
The cut of the sail was terrible, but functional. I cut down an I14 jib, but there was a big bag at the foot. The clew was too high for the traveler bar as well. I just guessed where the traveler bar should be, in retrospect should have mounted the sail first The Mast was a windsurfing fiberglass pole about 16'. It was unstayed so it would rotate and furl/reef the sail, and didnt have a boom to hit you. worked pretty well.
Anyway, i cut the mast down a foot to lower the clew, and found by reefing the sail a little i could actually get a good shape, which gave me pretty good upwind for a loose footed bike sailer!
Broad reach was always great (thing flew) but once i improved the sail shape i was able to fly a hull upwind and down, improving angles in both directions.
Best part was just flying across the desert at dusk, very comfortable, and felt like a martian explorer. biking from party to party at the burn. I would say i reached 25 mph on a beam reach single rider.
As a conglomeration of many things, i was apprehensive that it wouldn't perform. i didn't want to do a recumbent bike, because i wanted people to have a similar experience to regular bicycling. so automatically the CG and CE was much higher. I also didn't want to spend a lot of time making a custom drive train so the bikes simply bolted on and off. I ended up having to weld a lot anyway for the frame, so probably doing a more comfortable reclining recumbent set up would be more efficient and aerodynamic, and lower CG/E anyway, so i guess ill go that route next time. Better sail shape too would be very helpful, so a sail that clears your head with a supported boom would be great.
I realized that there had to be a traveler to be able to get any decent reaching, and since that was my best hope for power, i added the bar and continuos traveler, which stuck out pretty far, but actually worked pretty well. Since i was apparent wind sailing a lot, having the flatter sail was really important.
All in all id say it was a success, had a lot of fun sailing it. Additionally being able to bike around when there wasn't any wind, or furl and bike directly into the wind (though usually not necessary unless confined to a street) was easy enough and done often enough that having the bike option was totally worth it. I didn't have gears, and it was still fine throw a ten speed on it next time and it would be even easier. Never needed a hand brake either, just sailed like a boat and used the kick back brake on the beach cruisers for bicycling.
I did find that biking to help generate the initial apparent wind help a great deal to accelerate quickly.
If people are interested i have a short go pro vid that i'll post and a few more technical photos of the frame and rigging. I will probably be posting an Instructables for it as well in the near future.