Re: Stringer replacement wood.
Lots of issues posted on this forum and elsewhere about the PL type adhesives giving way, once the tabbing is applied.
My 2 cents on the subject of the stringer bonding and tabbing to the hull. . .
The stringer itself represents a 'hard spot' where it contacts the hull. During the hull's impact with water the hull will tend to 'bend' around any hard spots. The 'bend' areas can result in surface cracks (crazing) of the gelcoat on the outside of the hull.
So, the various methods associated with stringer bonding and tabbing are designed to spread the 'hard spot' over a wider area, resulting in less bending, as well as giving the fiberglass tabbing material a radius bend as it meets the hull.
Offsetting the stringer from the hull tends to spread the forces over a wider area, because the forces between stringer and hull would have to go through the tabbing and any bedding material.
Hulls with foam-filled chambers have an advantage over non-foamed hulls in that the foam provides support and rigidity to the areas between the stringers (and cross members) . . . so less 'bending' of the hull during impact.
On both of my Formula boats, the stringers, bulkheads and cross-members are offset from the hull about 3/8" prior to tabbing them to the hull, and the contact for these components to the hull is purely through the tabbing. When I did some structural repairs on my F-242, I made the same 3/8" offset, but put some urethane foam in the gap between the hull and structural member rather than leaving it open as an air gap.
So, if you did use a foam adhesive for the stringer-hull bonding, you could probably do it, realizing that the forces will be going more directly through the tabbing material.
. . . Just my 2 cents.
EDIT/UPDATE: I found one of Dave Pascoe's articles that talks about the effect of stringers on the hull and what he refers to as the 'hinge' effect when the stringers are slightly suspended above the hull.
http://www.yachtsurvey.com/HullFailP2.htm
