After removing 2 outboard stringers for replacement, I think I got a little heavy handed with the grinder. The picture shows a rut of about 3/8" that follows the path (base) of the removed stringer. I did grind through a few layers of woven roving, but luckily not through to the botom. What would be the best material to build up a level base for the new stringers to sit upon?

Hopefully, I know Dave will chime in.....knowing how crucial this step could be, I'll wait for an expert opinion.

Thats the keel or chine of the boat, you can see the stringer was placed right above it. When I cut out the stringers in mine those areas 'that needed it' were leveled up with a green putty which I assume was dynaglass to make everythig flush. From the looks of it you dont have to do anything with it and can replace that stringer and your tabbing will reinforce that area

Are you sure its not two high spots and not one low spot? It looks like the leftover tabbing from the old stringer and its just humped up there. As PA said, theres really not much ya need to do to level it its not really not necessary unless you go into the surface laminate. You should e able to set the stringer like normal, if anything maybe lay down a few layers in the hollow to bring it up but it does not need to be linear for any reason. And also like PA said its common for that to be out of true over a chine.

I did grind abit more out in the track of the old stringer then the surounding tabbing.......the broarder image does show that, good illustration of that with the arrows there Dave! ....One more question if you don't mind, does the stringer have to float in a bed of hull & deck putty -or- do you sqeeze it down tight to the hull surface? ...I intend to use polyester hull & deck putty for the fillet also... Vinylester resin & 1708 for the rest of the coverage.......any tips would be great........thank you both.

I set stringers a little differently, I usually fit them pretty close but treat the stringer as sort of a big T joint or half an I beam and I put one layer down and bed the stringer on top of that and i do the gap (what little there is) and fillet with CoreBond or similar. Its also a timing thing thats done as that first bottom piece starts to kick. With this method the new stringer is 100% encapsulated and no chance of water getting through any old laminate build flaws.

I bed stringers down with cabisol and 1/32 milled fibers mixed with polyester resin