This is my 3rd prototype of the canoe cart. #1 used EMT conduit for forks, and a sheet of 2'x4' plywood as a base. I worked great until the EMT fatigued and couldn't hold the wheels straight. #2 used a length of threaded rod and some cheapie hardware store lawnmower wheels. No good except for pushing short distances by hand. #3 on the other hand, ROCKS! I went to the best LBS for spare/scrap parts, College Cyclery, told them what I was up to, and the guy dug around to find 2 closely matching forks for 20" wheels. I tried for a while to get a welder interested in putting a cross bar across the forks, but no one was interested...So, went back to good old hardware store and grabbed a stick of slotted angle iron. Ran a bolt through the hole in the center of each fork at the crown and two cuts of the angle iron. The angle iron is then screwed to a heavy piece of 2x6, which in turn mounts 2 slats of scrap wood that the canoe lays on. The tie downs go around the canoe and tighten against the 2 slats. I tie the boat to my rear rack such that it can't push forward into my tailbone, or fall off the back or to either side.
The point of all this is to eliminate the car shuttle. I live about 12 blocks from a free place to access the American River, and use this rig to go about 5 miles upstream where I put in, toss the cart and bikes in, and float down to our local spot. Then, it gets slapped back onto the cart, pushed up the levee to rideable ground, the bikes get put back together, and we ride home.
I'm sure I've put at least $150 worth of parts and time into these, but really prefer my homemade version to any of the commercial ones.
17' Michicraft Aluminum Canoe, about 80 lbs
97' Cannondale M500
1970 Skinny White Guy