I have a wide 17' canoe and a sharpie sailing dinghy I need to move. I bought a Winchester brand child's bike trailer at a 2nd hand store for $25 USD, but Burley or other brands would convert the same way. The pink and yellow nylon fabric covering was rotten so I cut it off, dismantled and cleaned the trailer frame and looked at pictures of boat dollies on the web. Next I cut off the longitudinal hoops at about 6", reinstalled the resulting vertical stub uprights and reconnected the cross-members. I measured and cut wooden dowels (old rake handles) and inserted them in blue foam "pool noodles" to form the boat bunks or padding. I drilled holes through the posts and into the dowels and pinned them with wood screws. To hold the boat to the dolly I used a combination of salvaged nylon ski-rack straps and a child's automotive safety seat webbing. Finally I pumped up the tires to 35 lbs psi, greased the axles and reinstalled the wheels. I left off the tow bar for this application because it is not needed or wanted. I kept all the components though as I could easily put a floor on the trailer frame, put the tow bar back on and use it for a cargo trailer with my bicycle. Total cost was $25 as I already had all the other parts on hand.