David:
I see that I have developed a crack about an inch long running up from the stabilator cut-out in the top half of the tail cone plastic. Can this be stop-drilled and repaired or am I going to have to locate a $replacement$?
Bob Steward, A&P IA (with slight expansion by the Editor):
This is an easy repair. The Beech repair manual states that the correct method of repairing the ABS plastic fairings (wing tips, tail cone, dorsal fin, etc.) is to solvent weld them with MEK. Paint the inside of the cracked area with MEK solvent and a small brush until the ABS begins to melt at the edges of the crack. Press together and let it sit until solvent has completely flashed off. Sand the outside of the crack smooth where the softened edge oozed out, paint if needed, and you are ready to re-install.
There are places, such as around cut-outs, where a doubler is probably worthwhile. If a doubler is desired, there are two methods that are about equally good. I’ve found that repairs with a doubler are easy and quite strong. If you don’t have access to some old ABS sheet (discarded interior trim, old wing tip, etc), you can buy it from some hobby stores. Buy a can of ABS cement at Lowes or Home Depot. It is the can that says the ingredients are MEK and ground ABS (about $3 at the local Lowes).
Method #1: After you have painted the inside of the area around the crack with MEK solvent (about 1″ out from the crack in all directions), wait 30 seconds and paint a second coat of MEK on, such that you see the color of the plastic starting to show in the liquid the brush is pushing around. Once you see that the MEK is successfully mixing with the base ABS plastic, you can paint a coat of the ABS cement on the INSIDE where it won’t be visible, and let the solvent flash out. It takes longer than the solvent flash from the MEK crack repair, since the ABS cement is a mix of plastic and solvent. Used in this fashion, it is basically a liquid plastic patch.
Method #2: The second method is to cut out a doubler of ABS with about the same dimensions (across and to one inch away from the crack in all directions). Let the patch soften in a small glass or metal dish of MEK while you are painting the inside of the cracked area with MEK. Place the doubler over the crack and if it is softened enough, it will conform to the contour and bond as the solvent flashes and the two plastic pieces fuse together.
Please note that the link to the trim tab/anti-servo tab on the Stabilator is a PRIMARY FLIGHT CONTROL, and as such may not be removed and re-installed without A&P supervision. Loss of control of the anti-servo tab (sometimes called the “trim tab”) is almost certain to result in loss of control of the airplane. This is a well known situation with all stabilator equipped planes. Be extremely careful when removing and replacing the one-piece tailcone. One of those Globe Fiberglass 2 piece replacements avoids this problem in the future. If you are installing a new two-piece unit, and your old one is in bad shape, just cut the old one off. That avoids the need to disconnect any linkage. Save the old tailcone pieces for use as future ABS repair plastic.