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« on: August 22, 2010, 04:05:14 PM »
From CP 52 page 5
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.
Regards
Steve
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