Straightened the Crooked Tail

I discovered a serious problem with my Bede BD-4C airplane as I was getting ready to install the top fuselage skin: the horizontal part of the tail was crooked. Specifically, the copilot’s side of the tail was about three inches higher (above the floor) than the pilot’s side. I did some careful measuring and figured out that the weldment that holds the horizontal stabilator was attached crooked to the end of the fuselage.

I rebuilt the gusset which forms the back of the fuselage, and one of the angles to which it attaches, reassembled everything, installed the tail, and found that the copilot’s side of the stabilator was still about 1.5 inches higher than the pilot’s side. I was thoroughly frustrated and completely flummoxed. By my measurements and calculations, the two ends of the stabilator should have been within 0.7 inches and the error was more than twice that amount. The shear amount of work involved in rebuilding the gusset again compounded my frustration.

This week, Steve from BedeCorp came to my “factory” to evaluate the problem and fix it. Many thanks to Jim Bede, Jr. for sending Steve. And many more thanks to Steve for figuring out what was wrong and actually getting it resolved!

Steve figured out that the weldment which attaches to the stabilator was sitting crooked on the plane. I had successfully fixed the problem that I had discovered; the weldment attached to the plane was straight. Here is a photo showing the problem. You can see the black weldment bolted to the fuselage; that one is straight. The curved weldment being held at an exaggerated angle holds the horizontal stabilator.

With the weldment off of the plane, Steve determined that it has been incorrectly fabricated. There are two ears which hold the “hinge pin.” They should have been aligned and they were not. Here is a photo illustrating the situation. The hinge pin is a 3/8 inch rod running between the ears along the yellow line. Before the part was repaired, the ear in the red box was improperly attached so that the hinge pin ran along the green line instead of the yellow line.

Steve cut the weld and removed the ear on the copilot’s side of the weldment. Under his direction, I built a jig to hold the weldment for repair. Steve then made a spacer so that the ear on the copilot’s side would be properly aligned with the one on the pilot’s side. A quick trip to S. S. Radiator & Welding Service in St. Peters got things fixed up properly. Here is a photo of the weldment, straight as it should be.

I have been grinning like a fool, now that this problem is fixed and I can finally make progress on my plane again. Pretty much everything I needed to do was blocked by what looked like the need to rebuild the tail end of the fuselage again.

I celebrated by bonding the top skin on the fuselage and attaching the vertical stabilizer.

If it seems like a long time since my last post, you’re right; it has been. I bonded the skins onto the bottom of the fuselage way back on April 7.