Mistake in Slider plans

Problem with the plans!

One of my builders has discovered a flaw in the plans. It does not affect safety or comfort, and does not change the shape or function of the boat in any way, but will undoubtedly puzzle builders when they get to the point of installing the seat risers. I believe other builders have noticed this problem, but may have attributed it to an error on their part. However, the error is all mine. In Drawing #3 of the plans, the distance from seat riser to seat riser is given as 13.5 inches. This will prove impossible to achieve.

When drawing the plans, I took the offsets from the ply sheets on which I lofted the original design. This put the midstringer at the proper height for maximum strength– about halfway between chine and gunwale. However, when I built the prototype, I made an error and put the midstringer slightly above the position I used when lofting, but did not notice I had done so. Because of the flare of the hull, this raised midstringer height allowed for more distance between the seat risers than is available when the boat is built exactly to plan. The plans were drawn well after the boat was built, and I simply measured the distance between the seat risers and used that figure.

The best solution, I think, is the one devised by Frank Woolf, who drew the problem to my attention. He set the seat rails into the frames slightly, and was able to get a distance between them of 12.5 inches. This is still plenty of room for knees, for most folks. He dealt with the problem of extending the rail past the daggerboard case by gluing a triangular strip of timber to the face of the case, which will then have a surface for the seat to ride on that is continuous with the rest of the seat rail on the side of the hull. I would still use the reinforcing ply gussets, as shown in the plans, especially on either side of the daggerboard case, since the rail there is not a continuous timber..

Frank also drew to my attention the fact that I did not explicitly describe the seating that makes use of these rails in the plans, so I’ll correct that here.

It is very important to have the seat rails the same distance apart throughout the cockpit, and on both hulls, so that both seats can be placed anywhere along the rail, reversed, and/or used in the same hulls for sailing together. The seat rides on a pad of ply just wide enough to slightly overlap the rails– just enough that the pad can be moved freely from end to end. The pad is centered on the rails by the use of timber stiffeners that are glued underneath the pad, and reach from rail to rail, with a little margin for slop. In Frank’s case, these rails will be slightly less than 12.5 inches in length, so the pad will drop onto the rails and center itself. On top of this pad is a small box built to raise the seat to the proper height, and builders can vary this height to suit their own preference. Folks with short legs will want this box to raise the seat less than folks with long legs. The reason the seat must have this box to raise the height of the seat is twofold: comfort requires a certain height above the duckboards, and depending on the seat chosen or built, the seat may be too wide to fit between the hull sides (including the daggerboard case). I used inexpensive molded plastic bassboat seats from WalMart, but more expensive padded folding seats may have a different width. The seat is bolted or screwed to this box. Dean Pacetti installed very clever little drawers in his seat boxes.

Frank sent me a picture of his build, after he discovered the error and built the corrected seat rails. You can see the seat pads he cut, and on which he will build his seat boxes.

What a nice-looking build!

Anyway, my apologies for the error.

Ray Aldridge

October 22, 2010