I wanted to share a recent modification I made to my NE Dory to add a sliding seat. I didn't want to dish out the $ for a new Piantedosi, and I though: Why complicate things with a fancy rigger when the Dory is already wide. The oarlocks only need to mount 4" outboard of the rails for proper spacing. I found a relatively inexpensive used Little River Marine Monorail sliding seat with footrests on the web. In lieu of the riggers, I built rail-mounted supports for the oarlocks.

The "rigger" is cut so that they sit level with the horizontal. I used some surplus 3/4" oak plywood for the plates -- epoxied of course.

Threaded inserts (1/4-20 in stainless) are screwed into the rails. Since the bolts lie perpendicular to the plates, they enter the rails at an angle. I had to make special jigs out of 2x4 to make sure the drilling and screwing in the inserts was stress-free. (Well, as much as possible...)

The forward end of the rail perfectly straddles the centerboard trunk. The bolt threads into a 1/4-20 insert in the thwart. Note the trunk slot cover, hastily built after getting soaked the first time.

The aft end of the rail bolts into another threaded insert in the frame.

To get the proper height above the water, I had to add a 3/4" spacer under the seat.

Here's one for the photo of the month contest... :)