Stringers and wales

Stringers and wales

Hog, keel, keelson, stringer, inwale, outwale, gunwale, cap rail, rub rail, these are all longitudinal frame members which add to the stiffness of the hull. These must all be laid out in your construction drawing. The builder will then either follow your plan or do what he knows is better than what you've drawn.

In out last discussion we had laid out the frames and the stem and transom. We will now draw in the longitudinals.

Here's our salmon boat as we left it,

So first we'll draw in the chine log, this is the longitudinal that goes along the chine of our boat. Our scantling calculation tells us that this should be sided 15/16 ths and molded 1”5/16 ths so we'll round up to 1x1 3/4 and draw it in,

Now this is an internal chine log so it looks like this,

Once you've drawn in the planking you can add an external chine log to protect the plywood edge or you can specify fiberglas tape. Me, being a belt and suspenders kind of guy, I go for both.

Moving up to the head of the frame we can draw in the inner and outer wales which, with the rubbing strake and the cap rail make up the gunwale. The scantlings calculation calls for just short of 1x2 so that's what we'll use.

This just the out wale,

and is shown on the construction profile as,

The completed gunwale would look like this, What is not shown here is the planking which would be between the rubbing strake and the outwale.

It's my practice however to add a second rubbing strake so that the final gunwale would look like this, 

The little over hang acts as a drip rail and gives an edge to fasten clips for capsize lines.

The next longitudinal is the stringer. You can have internal stringers for fitting seats or just use cleats which are shorter pieces between two or three frames and you can have external stringers for nailing your plywood to. In either case I like to draw the stringer parallel to the waterline half way up the center frame and then add more if required.

This design would probably be OK as is, although I am tempted to add a second stringer above the current one to provide more strength in the bow.

Next week we'll deal with the hog and keel and planking.