A bit of additional information to ruin everyone's suggestions now

The Rhino Rack Kayak lifter could be on the right track, but the setup comes with a bunch of stuff for mounting the Kayak itself too, not just the slider arms. $850 for the lot which is too much and wasting half of it anyway. I'll look around for something that would work as just the arms.
No winch to do with.
No shed rafters to hang it off of. Will be stored on the floor and have to be lifted.
Have to have a method for doing it truly by myself, a 'little help' from the wife doesn't work.