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In reading through the Section V Finishing Specifications in the L-4 Erection & Maintenance manual, it appears that silver (aluminum) dope was eliminated from the covering process. The L-4A's & B's had silver dope and then it was eliminated, and as specifically stated "Aluminum dope not used on model L-4H." While this is a military manual, it strongly indicates that Piper also stopped using silver dope on L-4's. They went straight from clear dope to the final OD top coat (one cross coat).
Makes sense from a production standpoint, faster & cheaper. Saves a little weight. Maybe the aluminum paste became difficult to obtain with rationing, but more likely it was the realization that L-4's were on a one-way trip to foreign lands with a short expected service life before they were destroyed or required major repair & recover, so why bother with UV protection.
Of course none of this has any practical relevance today, just a historical tidbit.
Makes sense from a production standpoint, faster & cheaper. Saves a little weight. Maybe the aluminum paste became difficult to obtain with rationing, but more likely it was the realization that L-4's were on a one-way trip to foreign lands with a short expected service life before they were destroyed or required major repair & recover, so why bother with UV protection.
Of course none of this has any practical relevance today, just a historical tidbit.
