stringer at chine???

Thanks For Sharing

 

This conversation become very helpfull to me. Thanks everybody for sharing experiences and comments.

 

Circular stringers are sometimes used in skin-on-frame boats. As Michael pointed out it would require additional epoxy which you seem to be trying to avoid.

A chine log joins two pieces of sheet material like plywood along a chine, which is a longitudinal edge in the hull shape. I prefer to use the term “stringer” for a length of wood (or other material) applied between the top and bottom edges of the sheet to add strength and stiffness. Both types are shown in the design you attached to post #3.

The strength and stiffness of a properly made chine joint between two pieces of plywood far exceed the strength and stiffness of a chine log, whether the joint is made using a chine log or by using the taped seam method. So the chine log only functions to connect the two sheets, it does not add much strength and stiffness.

As Par explains, it’s either one way or the other. About the only way to mix the two would be to have a chine log on the inside and apply glass tape and epoxy to the outside. This is sometimes done, but mainly to protect the outside surface of the chine from damage. Again, it does not add much strength and stiffness.

Moving on to the example you provide in post #13, case 1: chine log. The strength of this joint lies in the width of the glue joint. As DC points out the joint width shown, taped or logged, is inadequate. The depth of the chine log makes it rigid to prevent deformation while the plywood sheets are attached. Once the joint is complete the chine log does the same job as the tape in case 2, joining the sheets together. To a large extent chine logs used in this manner are essentially ballast on the finished boat.

Of course, the chine log can resist torsional loads across the joint in the plane of the diagram, that function is performed on a taped seam by a fillet of thickened epoxy, which is usually applied to the inside curve of the tape not between the ply sheets as you have shown. It is difficult to obtain a good joint on the edge of plywood and epoxy used in this area would be more for sealing than for strength.

In small boats such as the canoes that I build, chine logs can be glued to the sheer planks while they are flat. Flat joints are easiest to make and take least glue. When dealing with long, thin plywood panels this practice makes them easier to handle without damage. When the sheer planks are bent to their final shape the chine logs must twist and bend with the plank. It is then easy to plane the bevel for a bottom or bilge plank. However this method is limited to small boats because the chine log/plywood combination soon become too stiff to bend without cracking as plank thickness and the chine log width and thickness increase.