Hi Fretz

The measurements were taken from the launching trolley of a commercial combination trailer/trolley.  I assume your “yard trolley” is its equivalent though it doesn’t read as though it gets wet!  The frame is of 30 mm hollow box section, I think it is 2.5 mm thick.  It consists of an “A” frame 4’3″ wide with sides of 5’9″ length.  The aft support is on a rectangular 10 & half inch rearward frame extension.  I believe this is to improve the weight distribution for towing and should not be necessary in your situation.  The commercial support cradles are of moulded fibreglass, the front one 5’9″ ahead of the axle.  A wooden support should be easier to make.  The handle rises 1’3″ from the front of the triangle at an angle of about 65 degrees. Wheels are pneumatic 8″ plastic trolley wheels.

Because it is designed as a combination unit it is balanced for towing, on its own the trolley with boat is very front-heavy, your swivel wheel will help.  Referring to an ancient measuring instruction to get cradle advice, the keel will be 5 3/4″ below the chine at a chine beam width of 4’3″.  Axle dimensions need to be added and the cradle needs to be raised sufficient to clear the wheels (sorry if I’m being too obvious).  I sail from a shallow beach so favour a lower loading height and large wheels but the above should be adequate for a good level surface.  Good luck with the project.

Norman