View Full Version : shellback directions

09-05-2016, 10:56 PM
I have a question for anyone who has built a shellback dinghy. the midship frame and the stem are both made by laminating strips of wood over station molds. the directions from the companion paperback for building the shellback states for the midship frame "...from enough 1/8 x 1 1/8 fir or mahogany strips to laminate as shown. Finished siding to be 7/8" " I don't know what finished siding refers to. It can't be the width of the laminations, since the finished frame appears to be much wider that 7/8 of an inch. Similar direction exist for the stem, the 7/8" measurement for the "siding" is again referred to. Once again, the thickness of the stem is much larger than 7/8 of an inch.


david Posner

09-06-2016, 12:00 AM
David, hopefully I can clear up your query. When talking about the dimensions of boat parts The "moulded" dimension is taken as meaning the size from the inside of boat to outside and "sided" is the 'thickness' or usually the lesser dimension. So taking a frame that goes across the boat from port to starboard its "moulded" size is from inboard to outboard and its "siding" is from for to aft. the keel's "moulding" is from top to bottom ( which is inboard to outboard ) and "siding" is port to starboard. Clear???? I hope you can understand that.

So as for your frames and stems etc. they will be made up of lamination staves all glued together to make a component that gets its "moulded" dimension increased each time another stave is added. These staves in your case are 1/8" thick and 1 1/8" wide. The "sided" dimension of the component is gained from taking the glued up article from the jig then sanding or planing the glue and width down to get your finished "sided" dimension. Staves are usually cut a little wider than the "sided" dimension because they wont come off the jig entirely straight or flat and the staves wont behave by lining up 100% so you will need to plane each side of member down.

So for example, if your stem is 2'' moulded and 7/8" sided you will need to make it from 16 @ 1/8" x 1 1/8" staves allowing you to take 1/8" glue and misalignment from port and starboard.

Hope this helps


09-06-2016, 12:27 AM
that makes perfect sense, and that is what I thought siding meant, but the companion book gets confusing. for the stem, they ask you to cut the mold out of two pieces of 3/4 inch plywood and screw this together for a total of 1 1/2 inches in size. then the in one of the photos it shows a picture with the description " the rough stem has been surfaced in a thickness planer to 1 3/8"" yet the original description of the stem is that it was "finished siding to be 7/8 inches". I think there is a typographical error here. I was wondering if anyone every build the shellback, and also bought the companion book from the wooden boat store and ran into this and came to the same conclusion?


Peerie Maa
09-06-2016, 09:58 AM
I suspect that the inner stem, otherwise called the apron and stem knee, is sided 1 3/8, to give enough strength and meat to attach the planking to. Whilst the outer stem which covers the ends of the planking is 7/8" sideing.
Can you not measure from the plans to check this out?

09-06-2016, 10:41 AM
that is exactly what I was thinking. I'll go back to the plans and let you know. thanks for responding. By the way, you know that only builders of wooden boats use words such as "whilst" any longer.