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After about 200 hours, some thimble wear was showing where they contact the tangs on the upper set of cables. No significant wear was found on the lower cable set. I suspect this is because these cables carry little load as the horizontal tail surfaces carry down load to maintain the FireFly in level flight.
As can be seen at top of the photo, the cables are strumming like a base viola string. This motion causes the thimble to rock from side to side in the tang, and the stainless steel surface slowly wears away the thimble. The thimbles showing the greatest wear were those high up on the vertical stabilizer. These thimbles and the upper cable are located in the propeller blast area. Increasing cable tension will reduce movement, but also it adds additional load to vertical stabilizer tail post. |
To let wear continue could lead to cable damage, and so I elected to repair the thimbles. This was done by cutting an 0.016 inch thick strip of brass, 3/16 of an inch wide and 3/4 of an inch long and, wrapping it around the thimble and cable. Then JB Weld was applied to the area of wear and the brass wrap slid over it. Then additional JB Weld was applied on each side of the wrap and the thimble. To ensure no cable restrictions, adhesive was not applied to the cable.
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 Here is the final product. Upon installing the cables, I may increase tension a little. I will have to keep watching them to see if they hold up another 200 hours.
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