RV-7 Rudder Stiffeners

[DougH]

Hi,

I cut all of the R-915 rudder stiffeners and went to match the holes in the R-915's to the rudder skins (R-901R and R-901L). The holes don't match up, it seems that each hole center is off by about .040" so the error stacks up and if I cleco the fore hole the aft is at least .25" or so off!!! Seems like it might be a CNC error? I just received the kit in December. Does anyone have any ideas of why this might be? The temperature difference of the parts when they were drilled? Maybe it was a bad day for the CNC machine, hopefully its the stiffener holes that are off, not the skin.

Any help would be greatly appreciated!

 

[jcoloccia]

Make sure you didn't cut the stiffeners "backwards". Flip them around and see if they fit better the other way. I think that would cause what your seeing although my memory is a little foggy now.

edit: Duh...nevermind. You can't really flip them around because a lot of them are already cut...it'll obviously still be off by 1/4". I still think it could cause this problem, though.

 

[jcoloccia]

BTW, I assumed you meant "off" forward and back. If you're talking left and right, the stiffeners have a slight curve to them. Vans said I could COULD flute the stiffeners slightly to make them lay nice and flat. I don't remember but I think I ended up doing that. As always, though, don't take my word for it. Check with Vans or your EAA tech (or someone else you trust) if this is your problem and you think fluting might fix it.

 

[hydroguy2]

Hi,

I cut all of the R-915 rudder stiffeners and went to match the holes in the R-915's to the rudder skins (R-901R and R-901L). The holes don't match up, it seems that each hole center is off by about .040" so the error stacks up and if I cleco the fore hole the aft is at least .25" or so off!!! Seems like it might be a CNC error? I just received the kit in December. Does anyone have any ideas of why this might be? The temperature difference of the parts when they were drilled? Maybe it was a bad day for the CNC machine, hopefully its the stiffener holes that are off, not the skin.

Any help would be greatly appreciated!

Got my tail in November. But am doing the rudder now and yes I notice the same hole stack also. BUT I was fortunate enough to cleco the stiffeners to the skins prior to cutting them. I had to shift each rib until the holes lined up, then mark each one for cutting specific to its spot. Hope this helps

 

[lostpilot28]

The stiffener holes are like that so that half of them fit on the left skin and the other half on the right. They are not interchangeable. I had to look at the plans and drawings back and forth about 3 or 4 times before I figured out what was going on.

The reason for this is that the stiffeners on one side of the rudder have the flange on the top and the other side of the rudder they are on the bottom (unless you're doing the elevators, then it's the left or right). Make sense?

 

[osxuser]

I did the same thing I think your did. Note the plans say to trim off the fwd side of the stiffiners, I did that on the first one. The next skin I brain-farted and cut the aft side off. That doesn't work, the last aft hole sets the alignment for the whole stiffener, and I cut them off. Four new R-915 stiffiners need to be ordered...

 

[jcoloccia]

Thank you, Stephen! This is exactly what I was trying to describe and my brain was just not working right at the time

 

[andrew phillips]

make new stiffeners

I did the same thing too. I had somebody here bend up some 3/4 x3/4 angle out of .025 aluminum and I just made new ones and used the skin as a drilling guide. the stiffeners for left and right are exactly the same the only difference is that you flip them over depending on which side you are installing them on.

Andrew

 

[osxuser]

Before I'd make new ones, I'd just drill new holes in the old ones... I'm pretty sure an extra set of holes wouldn't hurt a darn thing, but I'll be ordering the parts from Van's anyway...