Left & right, plus hole alignment

[Bryan Cotton]

Hi all,

Working on my tail, I am pretty sure the left and right forward stab spars had the wrong stickers on them. Same for the -05L and -05R clips. Am I crazy or is this a common labeling mistake?

I piloted up my laser drilled hockey stick holes to #40. If I cleco in the root first, I have to flex the fingers of the hockey stick to get the holes to line up. This is way different than scratch building, where all the holes are perfect. My former 1946 C140 restoration project also had holes that lined up perfectly, even swapping in used parts from other airframes.

One final question, it looked like the callouts for the rivet holes were 1/8" rather than #30. Am I understanding that right?

Thanks in advance!

[kmacht]

I can't comment on the labeling issue but if the fingers of the hockey sticks aren't lining up is it possible that the bends are slightly off putting a slight angle on the part at the bend line? A quick e-mail to Kerry would probaby be a good idea just to make sure flexing them isn't going to be a problem.

You have to remember that those piper parts were mass produced in a factory with thousands of them made. The replacement parts you buy have had many years of engineering go into the tooling and processes that make them perfect. Sonex is just starting to get into the laser cut and matched hole business. There are going to be some teething pains while they get everything perfectly tuned and aligned in the programs and tooling making these parts. It is not as simple as just dropping a CAD drawing into a CNC laser cutter or router and having perfect parts pop out. Just because the parts are drawn accuratly doesn't mean that they are always machined perfectly. There are a ton of variables in the machines and the setup of the parts that can affect exactly where the holes end up.

I don't have my set of plans in front of me but every 1/8" rivet I set in the sonex took #30 holes. Using a 1/8" drill bit instead of a #30 in all practicality won't matter that much. The #30 drill bit is only about .003 bigger than a 1/8" drill bit. I can guarantee that you aren't drilling holes to that close of a tolerance if using store bought drill bits and a hand drill. If the rivet fits go ahead and pull it. To quote John Monett "you aren't building a swiss watch"

Keith
#554

[Bryan Cotton]

Thanks for the reply Keith! The bend in the hockey stick is away from all the holes, so there is no way it can affect the alignment out at the fingers. I suspect there is thermal expansion at play when the holes are piloted, and when it cools the fingers warp. More likely to be an issue in .25 than in .025.
I do have a note into Kerry, have not heard back yet.
PS out of loyalty to the Cessna taildragger clan, C140 is a Cessna not a Cherokee 140!

[Bryan Cotton]

Kerry says it is OK to flex the fingers over and updrill/rivet it that way. I may look at sliding the hockey stick slightly to share the misalignment so I can get it cleaned up with the #30 bit.

[Bryan Cotton]

All,
A happy ending. Clecoing in from the root to tip, I realized it was only the last 4 or 5 holes that were poorly aligned. I clamped the hockey stick in a vise (between two pieces of pine) and gave it a tweak, and the holes lined up well at #40 and cleaned up at #30. I clamped the hockey stick flatwise with the last 4 or 5 holes hanging over and did a couple gentle taps with the mallet.