Originally published May 1997
Our speaker for the main program was Mark Grubb of Tehachapi. Mark is a CFI, power and glider, with over 17,000 hours experience. Mark's slide presentation centered around his restoration of a 60's vintage balsa core fiberglass racing glider, and the care and feeding of fiberglass structures in general.
Mark convinced us that fiberglass restorations should not be undertaken by anyone with any aversion or allergy to either sandpaper or elbow grease. His slides showed the results of the use of voluminous quantities of both. Like any other artistic endeavor, it is definitely a labor of love.
Mark gave several recommendations to forestall the necessity of restoration. Fiberglass should be finished in the lightest available colors (namely, white) (are you paying attention, Mr. Piavis?) to prevent damage from ultraviolet light. One of Mark's slides showed some deterioration of the structure under dark numbers painted on the bottom of a wing. Fiberglass structures should also be stored out of the sun. But since gliders are no fun indoors (they are indirectly solar powered after all), and thus have to go outside from time to time, Mark recommended a good coat of carnauba wax (more elbow grease) to prevent crazing. No silicone wax, please!
Two of the most effective performance improvements that can be accomplished on fiberglass aircraft are the addition of fillets in appropriate areas, and profiling to remove small irregularities from an airfoil. Several of Mark's slides depicted the use of tufting to visualize air flow and identify drag areas. In the area of profiling, Mark described the use of a dial indicator in a homemade fixture (poor man's spherometer) to detect slight discontinuities. Once detected, application of moderate amounts of filler and great quantities of (you guessed it!) sandpaper and elbow grease are required for repair. The results can be well worth the trouble, however, as Mark reported that a good job can result in several points improvement in the lift/drag ratio.
Thanks, Mark, for an enlightening presentation.
Contents of The Leading Edge and these web pages are the viewpoints of the authors. No claim is made and no liability is assumed, expressed or implied as to the technical accuracy or safety of the material presented. The viewpoints expressed are not necessarily those of Chapter 1000 or the Experimental Aircraft Association.
Revised -- 19 December 1997