Hull Core Repairs, Post Blister Repairs
I have just completed replacing approx 10 sq foot of balsa core in the bottom of a J36. I did the repair from the outside and started by removing the outer laminate and the rotted balsa core. The interior laminate showed holes from cabinetry screws, etc.
I did the repair as follows:
1. Wetted out the interior laminate and new balsa core with neat west system epoxy.
2. Prepared a mixture of resin and collodial silica to a thick consistency and then coated the interior laminate.
3. Allowed the squares of balsa core to open up over the edge of a table, and filled all of the joint lines (in both directions) with the thickened mixture.
4. Pressed the balsa core in place and was presently surprised in that it did not need any support even though it was a vertical surface.
5. Then proceeded to glass a new exterior laminate to the exterior of the balsa core.
By adding glass over the interior of your exterior laminate, i do not think your cores will line up properly and you run the risk of creating a hard spot. The thickened epoxy mixture will more than provide "insurance" against your exterior work as well as assure a good bond with the balsa core.