I determined the dimensions and shape of mine by pinning lengths of
tape to the underside of the bench with drawing pins. I used two
pieces of tape; one left to right, and one back to front. I first
adjusted the left/right one to give the correct “sag” then pinned
the front/back one to the underside of the bench, adjusted the "sag"
and then pinned the front to the middle of the left/right tape. I
wanted the “middle” of the skin to be lower than the front.
I then assumed that the final shape of the skin would be basically
semi-circular, with a width equal to the length of the left/right
tape, and a radius equal the the front/back tape. I added a bit to
the dimensions to allow for the method of fastening.
The following photo shows the skin I made…
As you can see, it’s almost semi-circular with the sides cut off.
I screwed 9 cup hooks to the underside of the bench, which you can
see in this photo…
and put brass reinforcing rings into the skin, its then a simple
matter to hook the skin onto the cup-hooks.
Here is a picture of the skin in place.
I hope this makes sense.
Regards, Gary Wooding