: I have been told that laminating with epoxy will result in a very stiff beam
: as the glue is much harder than the wood it is bonding, and that a single
: pack polyurethane adhesive will give more flexibility while still
: maintaining a joint strength greater than the timber (hoop pine).

It doesn't make a difference whether you use epoxy or polyurethane - the resulting laminate will be stiff. It has nothing to do with the glue - it is the restriction on the movement of the wood. Take two thin pieces of wood the same length, hold them together so both ends are even, and bend. You will notice the ends are no longer even - the inner piece is "longer". When you glue the pieces together, they cannot move independently. The best solution is to bend the gunwale into shape and then add the other strip on the outside. This will stiffen the gunwales in their desired shape. You can use epoxy or polyurethane glue - both will work well.