There are many designs of wheels for canoes on the internet made from PVC tubes and this is what I did for my Perception Prodigy 10 and the design can be adapted for most kayak styles. The wheels are small and at towards the rear so you still need to support some weight when pulling on the front toggle but is one of the smaller compact design which is better than dragging or carrying it to and from the car to launch site or on portages.
Step 1: Tools Materials and Frame Instructions.
A selection of PVC pipe and fittings and joint glue. This design uses 1/2 schedule 40 pipe, 4 tees, 2 elbows and 4 end caps. A pair of wheels from an old lawnmower or child's toy. 1 rod threaded both ends, 2 washers/nuts and some thin cord or rope.
Saw or pipe cutter, drill.
Measure your kayak and cut tubes roughly to length and slip them into the fittings. Position and adjust to conform to your kayaks hull shape. Once the pieces are the right length and are adjusted to cradle the hull, remove and dismantle. Prep and glue the fittings. Start with the 2 elbows and 3 tubes gluing them against a flat suface for alignment. Next glue the 2 tees and 3 tubes between the wheels again against a flat surface for alignment. Assemble the glues assemblies with the remaining 2 tees and 2 tubes and end caps. Mark the angled tee fitting and the tubes with a sharpie to ensure the same angle is achieved when you glue it. Dismantle and glue the angle supports pushing together with the sharpie marks aligned. You should have the frame assembly completed except for 2 end caps where the wheels go.
Installing the wheels will depend on your wheels. If they have a bolt or stub axle then drill a a hole to suit in the end caps, bolt the wheels into the end cap and glue the end cap to the frame. If you simply have a pair of wheels locate a rod that fits the wheels and drill the end caps to suit. Bolt the wheels to the end caps and glue to the frame or glue the end caps to the frame and insert the rod through the frame and tighten a nylock nut and washers both ends to retain the wheels.
Note, instead of end caps inboard of your wheels you can use a pipe reducing fittings in the end of the tubes which might already suit your bolt/rod size and offers more support to the axle.
Set the frame and wheels on your upside down kayak and tie two loops of rope through the frame. Loop the first shorter one over the end of the kayak looping it around the carry toggle or use a carabiner to latch to a feature. This holds the frame up against the hull. Then loop a longer piece through the frame and around both sides of the kayak. Turn the kayak over and tighten this second loop around the front of the cockpit to tension and hold the wheels in place. So as to not have as long a loop and less stretch in the rope I threaded an old bungie cord hook on to the rope and hooked this onto the rear of the cock pit instead. A carabiner hooked into the cockpit or other deck feature would also work.
Step 2: Cart Complete.
You have a compact light weight set of wheels that are easy to fit or to stow in your kayak. Enjoy creating your own version to suit your kayak based on what wheels you can find lying around.