CaptJulian, Sand is not a commodity in these parts, so we have little to no experience with it, which I know is bugging the hell out of all the beach launchers.

Captain Dave, One last shot and then I'm done. I say, "Hubs?...we don't need no stinking Hubs!" Not unless your planning on speeds in excess of 20 mph. How about using schedule 80 PVC between the wheels and PVC connectors (2 1/2" electrical size will fit your wheels) and a length of galvanized conduit inside, pinned in place with S/S bolts. With a little paint or inhibitor here and there will be relatively rust free.