We designed and built a portable gantry to move the boat from its cradle to the trailer.  The 6" wide x 12' long I-beam is supported by jackposts which adjust from 7' to 9' in height.  The 3" C-channel base is supported by 8" steel casters.  (20-NOV-2008)

Time spent building the gantry was well worth it.  Any failure at this stage would be catastrophic !

The sling consists of 1/4" thick flat steel plates mounted to each side of the stringer.  The 1/4" plywood spacers prevent marring the finish.

The bolts mount in double shear e.g. the two parallel plates distribute the load across the whole bolt shank.   If the bolts were to shear, they'd be broken into three pieces as opposed to two pieces if bolted to a single plate.

The schedule 80 pipe bushings carry the load.  The 1/2" bolts keep the plates snugly against the stringer.