David Paule
Well Known Member
The lack of clearance for the RV-4 elevator horns which are supplied by Van's is well documented. I took some photos as I worked through the down elevator deflection clearance.
I started with both elevator rod ends adjusted per the plans to 3/4". Then I trimmed the horizontal stabilizer spar lower flange to provide clearance since it limited the horn to about 1 or 2 degrees down travel. That opened it up to about 17 degrees, with the elevator horn then hitting the lower stabilizer hinge mounting bolt.
By the way, you don't need to trim the spar flange as much as I did....
I still needed more travel, and there was plenty of clearance between the elevator and the aft edge of the horizontal stabilizer skin, so I adjusted the outboard rod end in one turn. And I adjusted the inboard rod end out two turns. This gave sufficient clearance at the horn to allow up to 26 degrees travel. Each full turn is 1/24 inch or .0417". Three full turns on one rod end would give 1/8".
Since the plans say to have between 20 and 25 degrees down elevator and no control stop was attached yet, I felt that was satisfactory.
Incidentally, I used a laser level, an inexpensive torpedo level, to give me a rough idea of when the elevator was straight with the stabilizer. It's not in the photo but you'll get the idea.
Finally, now that the elevator horn had proper clearance, I used a transfer punch to dimple the horn. One of these, from Cleaveland. It's a common tool, worth having.
I hadn't heard of anyone else using these but it seemed a simple way to do it and it worked well. I tapped the punch three or four times and only got one dimple:
You can see it down in the lower left area of the horn. Due to the angle of the photo, there's a lot more edge distance than it looks like there is.
Dave
I started with both elevator rod ends adjusted per the plans to 3/4". Then I trimmed the horizontal stabilizer spar lower flange to provide clearance since it limited the horn to about 1 or 2 degrees down travel. That opened it up to about 17 degrees, with the elevator horn then hitting the lower stabilizer hinge mounting bolt.
By the way, you don't need to trim the spar flange as much as I did....
I still needed more travel, and there was plenty of clearance between the elevator and the aft edge of the horizontal stabilizer skin, so I adjusted the outboard rod end in one turn. And I adjusted the inboard rod end out two turns. This gave sufficient clearance at the horn to allow up to 26 degrees travel. Each full turn is 1/24 inch or .0417". Three full turns on one rod end would give 1/8".
Since the plans say to have between 20 and 25 degrees down elevator and no control stop was attached yet, I felt that was satisfactory.
Incidentally, I used a laser level, an inexpensive torpedo level, to give me a rough idea of when the elevator was straight with the stabilizer. It's not in the photo but you'll get the idea.
Finally, now that the elevator horn had proper clearance, I used a transfer punch to dimple the horn. One of these, from Cleaveland. It's a common tool, worth having.
I hadn't heard of anyone else using these but it seemed a simple way to do it and it worked well. I tapped the punch three or four times and only got one dimple:
You can see it down in the lower left area of the horn. Due to the angle of the photo, there's a lot more edge distance than it looks like there is.
Dave
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