Trailing edge c-sink depth

Hi,
I am wondering what depth of c-sink should I use on trailing edges E-01423L-R. So far I set depth to about .007" below the surface and it doesn't seem like it's enough for dimple to fit properly. The reason I used 0.007" is that on a wedge style trailing edge such as rudder any deeper than 0.007" seems to start making pilot hole larger and making it oval.

Any advice will be appreciated

When a countersink is called for in thin material, match drill to a piece of thick scrap, like a angle or something like that. Then countersink the whole shebang to the required depth. You can avoid making oval holes in the thin material that way.

Not sure about how deep to go other than wanting the dimple to sit pretty flat.

You're going to want to cleco the entire trailing edge to a piece of aluminum angle to keep it straight while the adhesive sets up, otherwise it'll be impossible to get a straight TE. I used a piece of 1/8" x 1.5" x 1.5" angle (get a piece long enough for the flaps and it'll work for all the other control surfaces too) and then match drilled every hole through the skin and wedge into the angle, clecoing as I went. Then I countersunk the wedge keeping the angle underneath it to serve as a guide to keep the countersink bit centered. This is especially important when countersinking the second side of the wedge as it will start to auger out the hole where the two countersunk holes intersect. Can't tell you how deep it is, I just dimpled a piece of .025 scrap aluminum and adjusted the countersink until the dimple fit perfectly into the countersunk hole.

As a side note, I'm at a loss as to why Vans switched from bent trailing edges to the riveted design. Compared to the bent trailing edges on my -8A, the -14 flaps and ailerons took almost twice as long to build. They're way more time consuming to construct, harder to get good results, require using adhesives, add weight, add cost, increase control forces, and can't be tweaked to correct a heavy wing (you need to add a trim tab instead). Any gap between the wedge and skins is an area likely to wick in moisture and invite corrosion over the long run, especially because you're not supposed to prime that area. I'm sure there's some advantage to the riveted TE's, I just can't think of one...

Czechsix said:

"I'm sure there's some advantage to the riveted TE's, I just can't think of one..."

Kutta Condition?

and (sometimes, but not necessarily here - minimum bend radius)

mjb

czechsix said:

As a side note, I'm at a loss as to why Vans switched from bent trailing edges to the riveted design. Compared to the bent trailing edges on my -8A, the -14 flaps and ailerons took almost twice as long to build. They're way more time consuming to construct, harder to get good results, require using adhesives, add weight, add cost, increase control forces, and can't be tweaked to correct a heavy wing (you need to add a trim tab instead). Any gap between the wedge and skins is an area likely to wick in moisture and invite corrosion over the long run, especially because you're not supposed to prime that area. I'm sure there's some advantage to the riveted TE's, I just can't think of one...

Click to expand...

Glad to hear you had an easy time with the bent trailing edge, but I assure you that is not universal with the average builder.
Builders not properly finishing the T.E. bend is a large factor in skin cracking at the aft rivets.
It is also a big factor in handling qualities and pitch stability.... there is probably hundreds (maybe thousands?) of RV's flying with trailing edges that have not been finished properly. The degree of influence this has depends on the severity, but it is never the less quite common.
The riveted T.E. solves these issues by providing for a much more consistent finish from one airplane to another. I will admit that it requires a little more work, but if you factor in the time required to make a bending tool to properly finish the T.E. I don't think it is a very big difference.