Leading Edge Check

[esco]

You might want to get an EAA tech counselor to take a look.

For now, don't drill out every less-than-perfect rivet. (see below from Alcoa Aluminum Rivet Book, 1984):

?The standards to which driven rivets should conform are frequently uncertain. In addition to dimensions and perfection of shape, inspection is concerned with whether the drive head is coaxial with the shank (not ?clinched?) and whether there is excessive cracking of the heads. It has been determined that even badly cracked heads are satisfactory from the standpoint of static strength, fatigue strength and resistance to corrosion...
(Poorly set and cracked) rivet heads were tested in tension to determine how well formed a head has to be in order to develop full strength. The tensile strengths of all the rivets were within five per cent of the strongest.

The test indicated that minor deviations from the theoretically desired shape of head are not cause for concern or replacement. The second rivet that is driven in any one hole likely to be more defective than the first because the hole is enlarged and rivet will be more likely to buckle and form an imperfect head...?

[JonJay]

Originally Posted by bkervaski

The goal here is to make sure the skin doesn't pull on the part underneath and develop a stress point. You want it to go out a bit and then start the curve. It took me more than a few attempts to get it just right.

What are you using to do the "roll"?

This is correct. The proper technique is to insure your Spar is being held down securely then press down hard on the skin with the bar and pull away as you roll. Try to keep the bar flat on the table while you roll it. We used to have a custom solid steel bar, very heavy compared to EMT. This helped to keep the skin flat on the table as the “roll” was being executed. This is hard to do solo.
It looks like you allowed the bar to rise off the table causing the skin to bend at the Spar. You don’t need the skin to match the bar radius. The bar is just helping to form the curve until you can join the two halves without induced stress.
It’s not too late. Carefully bend the skins back so they lay flat near the Spar, then roll it as above.

[Mickrat]

I think they look much better in person. They do fit the gauge perfectly. I do plan on having an experienced builder look at it. If it's not acceptable, I won't be the first to build another rudder.
Thanks for all the input.

[edbooth]

It may be the picture, but it appears that the edges of the parts have not been deburred or smoothed. Debuting wheel from Van's does a great job here.

[bkervaski]

It's not that there is anything wrong per-se (the airplane isn't going to fall out of the sky) just note that you don't want the "roll" pulling down across the spar or you may end up with cracks later.

You can get away with a few attempts without worrying about fatigue. I used a PVC pipe with clecos with enough pipe length to get a good grip.

Also, I had to go back and redo a bunch of those pop rivets, some of them ended up loose after the fact. I ended up developing a technique of flattening where the roll touches with my fingers before installing the rivet, seemed to help.

An easy way to drill them out is with this tool (worth every penny): http://www.cleavelandtool.com/Rivet-...ductinfo/RRT4/

[jacoby]

Originally Posted by Mickrat

I think they look much better in person. They do fit the gauge perfectly. I do plan on having an experienced builder look at it. If it's not acceptable, I won't be the first to build another rudder.
Thanks for all the input.

Which end of the gauge are you using? The hole is deceiving at best. The slot is much more reliable.

Take a look at the MIL spec, specifically pages 10 and figure 1 pages 13-17. Basically there is a min/max height and a min diameter. The gauges are nominally 1.5d on the hole (the min is 1.3d) and the height gauge is set right in the middle of the range (0.060" for a -4 or about 1/2d)

https://www.vansaircraft.com/faq/mil...n-and-install/

A cheap set of digital calipers (even the $10 ones from HF) are useful for double checking that you're within spec.

[bkervaski]

By the way don't let all the constructive criticism discourage you, nobody builds a perfect airplane. The empennage is everybody's training ground.

[flyabq]

Hello,
Those 4 center rivets are all needing to get redone. I would also recommend that you get a tech counselor to look at them before you button it up. The more you drive rivets the easier it is to tell from a glance the ones that should be redone. This is not a slight on your work, just experience talking. Most of your rivets look good.