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Break trailing edge of elevator skins

Michael Burbidge

Well Known Member
Somehow I missed the step instructing to put a slight break in the trailing edge of the elevator skin. I've already dimpled. Here are my options:

1) Rivet the trailing edge without the slight break.
2) Undimple, break and redimple the trailing edge.
3) Try to break with the dimple in place.

Any suggestions?

Michael-
 
I would break it slightly from the edge of the dimple hole to the edge of the material with a hand seamer.

When it comes time to rivet the top skin to the tail cone they have you check the fit just before install and suggest additional breaking if required. This is after dimpling and after the initial break so it is not uncommon to do.

See section 10-32 for clarification:

it says: Step 1: Cleco the F-01475 Top Skin to the Aft Fuselage as shown in Figure 1. Check that the skin fits well over the F-01474 Aft Side Skins. If necessary, break the edges of the skins further with a hand seamer as described in Section 5.16.
 
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Hi Michael, I had this issue as well once and just went ahead and used my tool on the dimpled edge and it came out just fine. However, I'm not convinced that breaking the skins is really necessary for a good finish, maybe due to improve manufacturing processes for making the skins. It's easy to overdue the break which creates new problems.
 
Nice tool

Hi Darin,

That tool looks great. I already put a slight break, aft of the dimples using my hand seamer. I think it will work out fine.

Michael-
 
Zuldarin - I have the snazzy vice-grip steel roller device from another company and recommend a fair amount of practice on non-critical material before using it. I managed to put bends in a rudder skin bad enough to make me reorder the part. :(
 
I'd like to share the technique taught to me by Aircraft Sheet Metal Pros working in Lockheed's and North American's prototype shops in WW-2 through the 70's. You want to put a slight bend to the trailing edge because while riveting the skin will stretch and will pull away from the trailing edge piece. Likewise with the flange on the ribs, they'll open up the angle of the flange and sometimes "print" a line after a number of flight hours.

Best approach they opined on the rib flanges was a 50-50 solder bar over a form block with a slight radius and "slap" or trap the edge down.
 
Somehow I missed the step instructing to put a slight break in the trailing edge of the elevator skin. I've already dimpled. Here are my options:

1) Rivet the trailing edge without the slight break.
2) Undimple, break and redimple the trailing edge.
3) Try to break with the dimple in place.

Any suggestions?

Michael-

Skip the break. Not needed, IMHO. I did the break, but prolly didn't need to.
 
The break is designed.

I see the break as a designed element of the airplane. If you don't break the edge the plane probably won't perform as well as if it is done.

This response to an inquiry by me asking for an explanation for the reason for the reverse wedge and break in the elevator trailing edge from Van's Scott McDaniels on 3/15/2015:
The trailing edge shape of the RV-14 elevators was selected for a number of reasons but none of them were to do with "dampening some sort of flutter, air flow efficiency, maybe easier to fabricate than a folded edge, something unique to get folks talking or scratching their heads, . . .";)

The RV-14 has been flight tested to a high level of detail.
This includes test flights by a lot of different pilots doing a lot of different types of tests. Some of which even included use of stick force measurements acquired using pound scales and a custom control stick with strain gauges.

During the course of this testing, a couple of subtle differences in handing qualities when compared to some of the other RV's, were noted.

As a result, design effort was invested to make adjustment to these by making a change to the trailing edge shape of the elevators.

This removed a very minor dead band in the elevator control circuit (which by the way, only a very few test pilots who flew the airplane with the original elevators ever made any mention about), and it improved the stick force per G gradient.

There is no down side to the shape (no measured speed difference) other than speculation that it was to resolve a strange "problem".
We look at it more as putting out the effort to make the airplane fly and handle as well as possible.

BTW, an added benefit in designing the RV-14 to this level of detail, is another design change that was made to the control system. The one system link that has always been a challenge to build free of play in side by side RV's is the roll hinge point on the control stick. The bronze bushing. Even if the best fit possible was attained between the bushing and the reamed hole in the stick weldment, there is always some level of slop.
The RV-14 is using sealed bearings for this pivot point on the control column.
The elevator control is silky smooth with no discernible play.
 
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Give Mike at Cleaveland Tools a call. He modified his break tool for me and it worked ok for me. He has it on the shelf in his shop. I got in a rush and made the same mistake on one of my side skins.
 
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