How do I connect a windsurfer mast to a board without a universal joint?

If you have an old board, the best solution is to take the deck plate (or the board if you don't have a detachable deck plate) and the mast extension to your local windsurf shop and properly outfit the rig with a brand new universal joint. Streamlined make excellent universal joints, and provide entire units, the deck plate, the tendon, and the cup which matches your particular extension. http://streamlined.us/bases.html If required, your shop can adapt that unit to your particular mast extension and/or the board if it's an older piece of equipment. The universal joint is probably the most important piece of equipment for getting back safely. You can break a lot of other equipment on a windsurfer and get back to the beach in one piece (broken mast, broken boom, lost fin, etc) but a broken universal is serious business if you are out on your own and can't otherwise get the rig upright to make headway back to shore. The current mast base and universal joints also come with an integral rope which keeps the unit together, even in the event of a complete tendon failure. If you're asking "how do I connect them after a failure", the basic answer is not to get into that situation in the first place by having the above. If you do experience a tendon failure, the current generation of bases will stay intact and you should be able to carefully sail it back without puncturing the skin of your windsurf board. The tendon itself wears over time, with exposure to the sun, and general use. They probably last a year if you are sailing nearly daily. If you sail only a few times a year, they should last quite a few years. Check them at the beginning of each season to ensure they aren't worn, cracked, or loose in the fittings. If you do experience a total universal joint failure while out on the water, depending on your distance from shore, you can either side-stroke the gear back, or de-rig in the water: roll up your sail, mast, and lay everything on deck, with yourself on top of your rig, and paddle the board back. It's a good idea to practice that if you are not proficient rigging and de-rigging on land. It's a different ball game doing it in water and waves. A new universal also one of the least expensive pieces of the setup, so worth spending the money on. Always stay with your board in the event of a failure and the situation is serious. It is your flotation device.