M_Boats: M15 Keel repair

I finally gathered enough courage to do surgery on the Pelican. Check out the pic at http://picasaweb.google.com/jascopacific/M15KeelRepair I discovered the steel punching are rusted at the top. It looks like water entered from above probably the interior of the cabin. Interesting is the vein of fiberglass that runs horizontally though the punchings. Any ideas about what this vein is for? This repair isn't very fun. I would rather be pushing to weather in a parting sea! Any opinions would be appreciated. Captain Jim Sailing vessel Pelican