[thedink9]

Unless the Inboards stringer system was constructed differently, the mushy stuff you were touching was most likely polyurethane closed cell foam. It comes in various densities and in two parts. You mix equal amounts of the two parts together and pour it into a hole at the top of the stringer.

A few questions: Was the foam wet? If so you may want to add an additional hole of two and try drying with a fan. I did and it took a few weeks to dry out. I also had a number of voids where the foam should of been. I added foam in those places and now have solid stringers. You can test for voids by taping with a rubber hammer. Hope this helps. Rich