Caution - Wing Attach Bolts
July 1987
We recently heard from a Cozy builder who had been chasing a minor but annoying vibration in his aircraft for some time. He finally traced it to the fact that his wing attach bolts were slightly loose allowing his wings to move a little in flight. After he tightened the three 1/2" bolts in each wing (the Cozy uses the Long-EZ wing and wing attach system) the vibration went away. He checked several Long-EZs in his area and found a couple of them with the same problem. We had not had anything like this reported to us before and we checked the two Long-EZs we have here at RAF, both were solid.
The way to check for this problem is to have someone put their hands on the joint between the centersection spar and the wing to feel for excess movement while you lift at the wing tip. A small amount of movement, less than 1/16" at the wing root leading edge, is normal. If excessive movement is detected, you must remove the wing bolt covers and torque the bolts. It is difficult to use a torque wrench in this area. We simply used two ratchet wrenches, each 6" long, and pulled about as hard as we could.
It takes two people to do it right. Since a person can pull with about 75lbs of force with one hand, we can calculate the torque - 75x5=375in/lbs or 31ft/lbs. Using this method, we have never had one of these bolts work loose. A 1/2-20 aircraft bolt can handle 600in/lbs (50ft/lbs) of torque. However, with the glass plies in between the aluminum hard points, we would recommend no more than 400in/lbs (33ft/lbs) of torque on these bolts.