In thanks to all who gave input on ways of towing my kayak behind my bike, here is the final solution I devised. It used a number of ideas received here along with some innovations of my own.

You can see the pictures here: http://home.pacbell.net/endoboy/kayak/Kayak_1.gif http://home.pacbell.net/endoboy/kayak/Kayak_3.gif http://home.pacbell.net/endoboy/kayak/Kayak_4.gif

I started with a golf bag cart as suggested here. Thats strapped on just below the coaming, with the coaming keeping the straps from migrating. On my first test run, one of the cheap plastic wheels flew off 3 blocks from home, ending that test, but proving the stability of the rig, which did not flip over. I upgraded it to 8" lawnmower wheels with bearings.

On the front of the kayak, I attached a boom through the front handle to the back of the bicycle seat. The boom is part of a carbon fiber windsurfing mast that snapped in half and washed up on the beach a year or two ago. On the kayak end, I attached a wooden crossbeam with an inverted V that matches the angle of the deck. It gets strapped tight to the deck.

The front of the boom has a really secure mount made from various bought and found objects. I started by putting a foam plug down into the front boom end and filling it with epoxy, several inches thick. Into the wet epoxy I placed a large machine eye screw--the kind with a socket inside the eye with a ball in it. The ball has a half inch hole through it, and swivels freely but with very little play. On the seat post of the bike I have a wooden spacer with two convex grooves that fit the post and another small tube of 1/2" carbon fiber from some old prototype bicycle work. I slid some 1/2" ID PVC pipe over the CF shaft to give a ggod surface to clamp to. Hose-clamps hold the CF shaft and the wooden spacer to the seat post. In the CF shaft is more epoxy, with the threaded part of a bolt sticking out. The ball joint of the boom slips snugly over the CF tube and a nut holds it from slipping off.

It all sounds very complicated now as I look over this, but the pictures will probably do it more justice than my description. The second test ride with upgraded wheels went splendidly. Even dropping down the steep hill at the beach posed no problems for control (of course, using a high-end mountain bike made all this much easier). On the way back, my son held onto the back on his skateboard, getting a free ride home. I'm sure it looked pretty amusing to the passing car drivers ;-)

Thanks again for all your suggestions. I'm looking forward to my next big project late this winter, a skin-on-frame kayak from Putz' book.