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Elevator mistakes

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datsclark

Active Member
I'm finishing up on the elevators, realized though I may have a problem that i need to fix. When drilling the counterweights, despite my best efforts with a drill press, the holes managed to intercept the counterbalance ribs not quite dead in the center. This in turn means the washer/nut won't lay completely on the flat part of the rib flange.

692196095_eZYqS-M.jpg


692196179_E4Ay6-M.jpg



Do i start over on these parts?

Another questionable situation is some slight bowing of the trailing edge skin where the stiffeners lay. I've tried to take a picture of it here. The actual bump is pretty small, but its noticeable. Again, what are the thoughts on this situation:

692202938_9SZDW-M.jpg


You can also see them on this huge picture: http://datsclark.smugmug.com/Airplanes/Elevator/IMG1749/692195616_zhCqg-X3.jpg

Hoping this doesn't mean I get to reorder parts! Thanks everyone.
 
My two cents worth.

Problem 1. Presuming that your bolt is actually perpendicular to the hole, you can simply grind off part of the washer to make it lay flat. Might require a second washer from what I see in the photo. If the bolt is not perpendicular, you could make a small wedge out of a piece of 1/8-inch Al scrap to allow the washer to sit flat against something. Overall, at least from what I see and what you describe, this is not a big issue as long as the weights don't interfere with elevator travel etc. and are not in danger of coming off.

Problem 2. I see the bump in the big photo. My trailing edges are built differently, but it seems to me that these slight imperfections are not cause for concern, at least in terms of the flying characteristics. If you are building a show plane, then you might consider some solution.

Again, my opinions only.

greg
 
Thanks guys. Greg, the bolt is nearly perpendicular to the hole, i think i may just go with a slightly motified washer. As you can see in the picture there, it isn't _too_ close to the bend.

Not going for a show plane--I was more worried about the bumps structurally. I guess worse case senario I have to rebuild that elevator down the line.
 
Build on...

Bumps like that aren't even on the radar structurally. Skins are fundamentally in shear, so bumps or even holes (i.e. inspection holes) are not an issue.
Sharp edged cuts or cracks are another issue - solved by making them rounded holes :cool:
If I rebuilt parts for every bump, I'd have ended up building 2 (maybe 3) planes :eek:
Your solution for the counterweight bolt is a good one.
 
About the bump near the trailing edge of the elevator:
Did you bend the trailing edge enough? I found it to be quite scary to bend until the shape resembled the sketch in the preview plans (Section 5, Fig 5-7). Since underbend trailing edges are supposed to be one reason for cracked skins at the last rivet of the stiffners this might be worth checking.
 
That could be Mario, the problem is near the end of the stiffeners. I will check the bend again and maybe bend it a little more.

Thanks!
 
I think you have got the counter weight issue resolved, the only suggestion about the counter weight I have is not to take too much off, specially if you are going to paint your plane. The added weight of the paint will be more then one thinks and you will end up having to add weight which is another topic by itself.

In regards to the trailing edge of the elevator, it may not be a bad thing to see what caused it. It is possible that you did not trim the stiffener enough or it is touching the bottom side (opposite) of the skin. This will not have any adverse affect in flying but it could cause cracks in the elevator skin if it is not done right. Also, don't forget to put some RTV or proseal in that area to dampen the vibration which also is another cause for cracks in the elevator skin.

Good luck
Mehrdad
RV-7A IO360M1B
 
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