While I was away at work, our replacement R-710 arrived, and Dad took over the task of re-trimming and fitting that part to the existing understructure.
On our first attempt, we trimmed the horn brace on the inside of the guide hole which is pre-punched in the center of the part.
As you can see in the photo above, Dad has drawn the new trim line well to the outside of the guide hole this time. Any shorter than this, and you’ll have the same rivet edge-distance problems we did with our first R-710.
When the old and the new part are placed side by side, you can clearly see how much we over-trimmed the first horn brace.
After the cut, Dad fit the horn brace into the rudder understructure assembly, to verify that the rivets would have adequate edge distance.
As you can see, he marked the rivet hole locations on the 710, just to make sure everything was copacetic before drilling.
Here’s a side view of the two parts – the new R-710 is on the right, after drilling, and you can see the difference the correct trimming method makes. The “notch” in the center of the edge is from filing out the guide hole, which should be left in your part if you’ve trimmed correctly.
Finally, here is the new, finished R-710, primed and ready for installation.