Damp Balsa Core: Small Area Repair

Outside Surface

Outside Surface

This cockpit hatch cover (36″x16″), during a purchase survey, was found to have a high moisture reading in a triangular shaped area near the forward hinge.

The cover was removed and 4 one-inch diameter counterbores were cut through the inside glass reinforced polyester to expose the end grain balsa core material.

The balsa was found to be damp but still structurally sound. The damp balsa in the counterbore areas was removed.

Cored Holes With Damp Balsa

Cored Holes With Damp Balsa

Now that the damp balsa core was opened up, the cover was propped above a warm air heating register and remained there for about 10 days. This was sufficient time for the dampness to be driven from the balsa, and the new moisture readings approached dryness over the affected area.

The voids were now filled with polyester resin with some reinforcing fiber added to the surface to replicate some of the strength of the original lay-up.

After curing, the total inside surface of the cover was smoothed out somewhat by powersanding and then spray painted (hardware store spray can). New hinges were installed and bedded in place.

Repair complete

Repair complete

This repair procedure was not difficult especially when all work is completed on the inside of the hatch cover and the side that shows with the antislip pattern is not touched. The only messy part being the sanding as much foul dust is created – work to be completed outside and with breathing protection.

by Ed Sulis

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