This image shows the starboard material cut to fit just inside the stern rail (middle where stern ladder folds up) and notches cut in the aft edge for the ladders verticle rails to enter lock with the ladder. The notches allow for the starboard board to capture the ladder with the rail mount bolted to the underside and attached to the horizontal ladder step. You can see the rail mount clamps on the forward side of the seat base. I used two mounts in the front and one in the rear. (see their positions by looking for the bolt pattern on the top surface.

Starting with the basic seat

This shows the seat base attached to stern rail and ladder step with a loose cushion on it. This does not work well because the un-attached cushion does not stay in place and you feel like you are going to slide off. So, I decided to add another piece of starboard for the cushion backing. I used close cell foam and sunbrella material to cover the new piece. This worked well, no sewing, just staple the material to the backside of the starboard. The staples are hidden when this is in place on the base unit. This in turn was screwed in place by running the screws from the underside of the base into the new starboard backed cushion.

First test...

This shows the finished project with rounded corners and smoothed edges. The seat stays in this position year round unless someone needs to use the ladder, in which case, loosening one clamp, the one that attaches to the ladder step, and the seat folds down, out of the way and the ladder is deployed.

This is the finished helmsmans seat

Im sitting on the new seat in this image. It will stay in the set up position year round unless I need to use the ladder, in which case, loosening the one clamp that attaches to the ladder and the seat folds up or down out of the way and the ladder swings down into the water.

For this project you will need:

1 Starboard board 12 x 27 x 1 for the base unit.

1 starboard board 12 x 27 x 1/2 for the cushion backing board.

3 1railmount clamps

1 square yard of sunbrella material
1 closed-cell foam 12.25 x 27 x 1.25 (cut down from 38 length)

The back rest cushion is from another project, but you can design your own backrest cushion.

Time to go sailing.. so, Im outta here!

The seat in good use