Design Requirements
A primary design requirement was that the Land Sailor operate in wind speeds below 10 mph. Down to as low as 6 or 7 mph if possible. This meant that it must carry a large sail. I checked Windance at Hood River for a large reasonably priced large sail and was able to come up with an 8.8 m^2 used windsurfer sail in good condition at a good price. Another primary design requirement was that the system be easily portable, not easy for a yacht that must carry a large sail.
Design Implementation
I next went seeking the materials to construct the yacht with. I found some 6061-T6 Aluminium tube with a 2.375 in. I.D. Since I wanted the unit to break down into small sections so it could be easily transported, I looked for some smaller tube to fit inside to act as a ferrule. I first tried some PVC schedule 80 pipe that had an O.D. of 2.375. With just a touch of sanding it made a perfect fit. Alas it seemed to flexible to me so I went to some Aluminium pipe of the same dimensions and though a little heavier it was stiff enough. I then conducted so load tests to see what a good width for the rear axle should be. I settled for a width of 9 ft. 8 in. rear tire tread center to center. I allocated 26 in. to the center "T" section for width. The axle tubes are then 42 in long on each side. With the seat mounted right on the rear axle I looked for a mast location that would allow the bottom of the sail to clear my head. This resulted in the mast being located 81 in. in front of the rear axle. I also selected a mast location for a 6.7 m^2 sail that I also picked up at a bargain price. It is located at 60 in. in front of the rear axle. The steering bar was located at a place I could comfortably reach, 43 in. in front of the rear axle. I then looked at a lot of different yacht designs and found length/width ratios of from 1.1 to 1.5. I settled on 13 feet based on the amount of flex I got in the forward frame. It turns out to have a L/W of 1.34. The center "T" section was allocated 26 in. The next two sections that contain the steering bar and the mast base plates were each allocated 42 in. The front section was then made 46 in. from the front axle to the ferruled joint. Each of the ferrules were made to extend 10 inches into the connecting tube. To hold the system together I used 1/4-28 bolts, one one each side of the joint. By removing only 5 of the 1/4-28 bolts the main structure can be disassembled into sections no longer than 46 inches. By removing 4 more bolts the seat can be removed. I originally was going to support the mast with steel wire, but decided against such a scheme because the mast flex would be more in keeping with a windsurfer sail if I put the support lower on the mast, and I felt it would be easier to setup and disassemble with tubular braces. This means four more small bolts must be removed to breakdown the mast support tubes. Finally two more bolts must be removed to separate the steering tube.
The picture on the left is of the "T" or center section of the yacht. Aluminium plate 3/16 in. thick is bolted to both the top and bottom to provide structural stifness. The picture on the right is of the rear axel tubes. They have a plate welded on the end to which a steel plate is bolted. The steel plate has a 5/8 in. bolt with the head welded to its back side.
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