Once I had this idea, I just knew I had to build one. A tensegrity launch trolley will turn some heads, and make my boat look lighter than it is.

In short, a tensegrity structure consists of a bunch of sticks, being held together by many strings/wires/ropes, such that the sticks a) do not touch each other, and b) are not subjected to bending. (I cheat a little with respect to the second requirement, since the wheel crossbeam must take some bending due to the placement of the wheels.)

Supplies

The wheels are normal wheelbarrow wheels. Large diameter wheels will help keep the lower ends of the aluminium tubes off the ground.
Thick-walled aluminium tubes, the kind used for boat awnings, were used for X:es near the wheels.
Some stainless steel tube I picked up from a gutter, just happened to have the right diameter to serve as the wheel axes.
The wheel crossbeam is a wooden stick, thicker than a broom handle.
It was protected with liberal amounts of tar.
The strings are 3 mm ultra-high-molecular-weight polyethylene rope. I did not need that for strength, but wanted it for low stretch and a skinny look. (3 mm instead of, say, 2mm, made it much easier to tie the knots.)
Near the end of the aluminium tubes I installed short, 5 mm diameter, stainless steel studs.
Some webbing was used instead of rope in some places, in order to spoil the boat.
They were held in place with some polyurethane sealant-glue-rubber.

Step 1: Plan or Play

I guess it boils down to what kind of person you are. You could either design this ahead, or simply start building it. I did the former. The construction is highly modular, so mistakes will not cost a fortune.

Those of you who have a PDF-reader/viewer which supports embedded 3D documents, should be able to rotate and zoom the "picture" of my design in the supplied PDF-file. (Adobe used to have a Linux-version of their Acrobat Reader, but sadly enough, now they don't.)

The proportions is for a coastal rowing single, and you will have to tweak the proportions for other types of boats, other use cases.