What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

A couple of rudder construction questions

UnPossible

Well Known Member
Hey ? I?ve got a couple of quick questions on the building rudder. I?ve searched, but did not find a clear answer to my questions.

1. On drawing 7, there is a note to ?locally bevel outside edge (of R-913 counterbalance skin) to smooth transition of R-901 as it runs off the edge of the counterbalance skin??..

?.I?m not sure what needs to be done here. It seems to me that any beveling should be done to the edges of the rudder skin as the counterbalance skin looks like it should tuck in underneath. Additionally, what is the best way to do this (file, scotchbrite wheel???)?

2. Countersinking the trailing edge wedge. I thought I had this all set up, but now I?m having some issues. I found some scrap AL the same thickness as the rudder skin. I drilled a #40 hole and dimpled the scrap. I then set up my countersink cages so that the dimple just sits flat in the countersunk hole? (note a rivet sits a fair bit below the surface of the countersunk hole.

I tilted the table on my drill press so that the wedge was perpendicular to the countersink tool. The first side went great. However, when countersinking the other side, I?m running into issues. It appears that once I hit bottom on the second side, I?m enlarging the hole in the wedge, which causes the tool to wobble a bit leaving a ?rough? countersink.

Now I?m wondering if I set the depth too deep?. However, I went a couple of thousandths a time setting up the cage until the samples just sat flush. At this point I don?t know if this is normal, or if I should just order another trailing edge wedge and start from scratch.


Thanks again for all your help,
Jason
 
Hi Jason -

Beveling the edge of the counterbalance skin will decrease the boxy protrusion that might otherwise appear on the skins. If I remember correctly, I only beveled where it crossed the rib. I did it with a scotchbrite wheel, but a file would probably do just fine.

With regard to your trailing edge wedge, could the wedge have been pushed too far into the skin, making the holes too close to the edge? On mine, the countersinks did intersect, but only on the thinnest half of the wedge. Even with this minor intersection, care was still required. I found the best method of holding the cage in place was to clamp my drill to the side of the workbench(aiming up) and press the wedge onto the cage holding it in place with both hands(the drill has an "always on" lock). My thumbs were sore, but it seemed to produce good results. I've had bad luck using my cage on the drill press.
 
Jason,

In contrast to Andy, I put the counterbalance skins on the outside of the main rudder skin - made more sense to me from a fluid flow point of view. If you do it this way, it is worth putting a bit of an edge roll on the counterbalance skin to make it pull up tight against the main skin when riveted together.

Countersinking the AEX wedge is tricky. One suggestion I have to minimize or eliminated the "hole overlap enlargement problem" is making a small jig that keeps the wedge in place, plus has a pilot hole (under the AEX) that will keep the CS bit from wandering. Even if you have some "hole enlargement" unless it is a lot, the rivet will expand to fill the space available when it is driven. (and be careful not to overdrive these rivets or you will end up with a bow in your trailing edge)

cheers,
greg
 
use a drill top on your work bench

cut a sacrificial table top for drilling out of 3/4 inch particle board and drill the holes in the wedge directly into the top, then use clecos to hold the wedge to the top and the drilled holes into the wood will pilot the countersink.
 
I found a method for countersinking the trailing edge that worked well for me. I drilled a #41 hole in a piece of flat steel barstock I had laying around (Note I used a drill press and rotated the table so that the hole would be at an angle which would make holes in the wedge perpendicular to the wedge). Using the #41 drill bit as a guide, I then clamped the AL wedge over the hole. Now when countersinking the tip of the countersink tool goes into the steel, prventing it from wobbling... it was slow but worked really well. I have a couple of holes from my orgional method that are slightly too deep, but I figure that when I proseal it together, any extra proseal should fill that small gap.

Thanks for all your help,
Jason
 
Back
Top