Hi Jimmy,
Nice job! Human powered from home to destination! And no more worries of whether there is parking, for how long, parking costs, having someone keep an eye on your gear while you drive off to park, save the time it takes to walk to the car and back… Plus save on the cost of owning a car!
To improve the cart I would:
– triangulate the 2 supports and add a cross brace between the two supports.
– get larger wheels (hard to find). If the wheels are big enough and spaced far enough apart the axle can be right against the boat and you can eliminate the 2 supports.
– for better bike stability / safety tow from one side of the bike’s rear axle, similar to most kids trailers. The tow bar should ideally run from along the center of the kayak and connect directly to the cart. And the front of the kayak is secured to this bar.
– add skid guard to the tail of the boat, and a flag for better visibility.
If I were to tow a kayak I would buy a used (or new) kids trailer w/ wheels spaced wide enough for the kayak to sit between the wheels. Then remove the kids seat and upper frame, have the kayak sit on foam cradles directly on the frame. Extend the tow arm with a metal bar, add a platform w/ foam for the front of the kayak.
Old folks like me would also add and electric motor to the bike…
Here are two trailers in good condition. You can get cheaper ones w/ the fabric in poor condition as that will all be removed.
https://vancouver.craigslist.org/bnc/spo/d/burnaby-mec-bike-trailer/7728524310.html
This one has aluminum frame (less rust from salt water) adjustable suspension which is a major plus, especially if the kayak is loaded w/ camping gear: https://vancouver.craigslist.org/nvn/bab/d/north-vancouver-thule-chariot-cougar/7732175473.html
Good luck!