[McFly]

I am considering taking on a HS reskin project (right side) for a flying RV-4.
The HS has a small crease on the upper surface an inch or two from the leading edge. The damage is not bad to my eye, some would consider it cosmetic.

It seems to me that I will have to re-jig the HS. Is this correct? Any other words of wisdom are always appreciated. Thanks for your help.

 

[Bob Kuykendall]

I am considering taking on a HS reskin project (right side) for a flying RV-4.
The HS has a small crease on the upper surface an inch or two from the leading edge. The damage is not bad to my eye, some would consider it cosmetic.

It seems to me that I will have to re-jig the HS. Is this correct? Any other words of wisdom are always appreciated. Thanks for your help.

Yes, I think that's true. The skeleton has little inherent stiffness of its own, and you'd need to hold it in alignment while you drilled the skin to match it.

I'd consider just making a whole new HS, and then selling the old one after it's done. That minimizes downtime, reduces (and hopefully eliminates) having to drill out rivets, and in my opinion is a more relaxing building experience.

Not that I'd necessarily do it that way, just that I'd carefully consider it as an option before drilling a bunch of rivets out of a flying airplane.

Thanks, Bob K.

 

[Andy Hill]

Hugh...

Another problem is that the RV-4 is not match drilled. The plans build would have you drill through the skin into the skeleton - but in this case, the skeleton holes are already there i.e. you will have to find another way to drill from the inside out through the skeleton holes.. possible, but am sure some interesting problems will arise

I would echo rebuild the whole HS, if a bit of filler / sanding or even cut and patch cannot sort the problem

Andy

 

[131RB]

Hugh,
A couple of things you can do without having to jig. You can take the old skin once you have drilled it off and split it at the leading edge into an upper and lower half. Line up the trailing edges on the new skin and transfer the holes. Another method would be to take a piece of thin plexi glass lay it over the the old skin make reference marks and transfer the holes that way. If done carefully either way should give good results. P.S. assuming the old skin is dimpled you can lay it on a flat surface once split and use a hammer and a backrivet plate with a light tap to flatten the dimples. The holes will line up.
Ryan

 

[McFly]

Thanks everyone.

Fantastic idea Ryan, I think that is the method I will use.

Hugh

 

[rocketbob]

Ryan's suggestion might not work. You have to consider that RV-4 skins were bent by hand and that there may have been some trimming done on the trailing edge of the skins by the builder. Since the original skins were sheared before the era of CNC turret presses its likely that things are off. The best way would be to lay the old skin inside the new one, and accept that the leading edge will be off by the thickness of the .032" skin which is a pretty small error. Then you can just drill thru the old holes. I would also flatten the dimples out to get better accuracy for backdrilling.

 

[Mel]

I was just going to say...

rocketbob types faster than I do. All trailing edges are NOT created equal!

Also want to emphasize; make sure to not lay the old skin on the "outside" as that would make the leading edge too short.

 

[131RB]

rocketbob types faster than I do. All trailing edges are NOT created equal!

Also want to emphasize; make sure to not lay the old skin on the "outside" as that would make the leading edge too short.

I feel like I need to defend my position a little here. Not taking anything the wrong way. The reason for spliting at the leading edge is to compensate for thickness and the bend in the metal if the trailing edge is maintained it wont matter if the skin is drilled from the inside or outside. I think we can all agree that the old stabilizer skin is junk so spliting it should be of no consequence. You should be able to get a pretty good idea of how close the new skin is by laying the two halves on respectivly. I think you will find it is very close. You should be able to trim the new skin using the old skin a guide. My guess is that your old skin is flush with the inside rib on top and bottom. You should be able to trim to align the root, trailing edge, and tip. Once thats complete you should be able to pick up the holes as described before. Any differences will be at the leading edge. It will not be noticeable physicaly or aerodynamicly. I have used this technique twice with no problems.
Ryan

 

[penguin]

I think Hugh would be in the same position if he built from a kit - just that the pilot holes he would have drilled in the ribs are now full size? To get the skin to fit right I think I would clamp the skin on around the edges as tightly as I could, and use ratchet straps in the middle. Then back drill all the holes I could access and mark the te and the ends for cutting. Cleco one side on and back drill the fwd spar and center rib holes (might have to secure the center rib with all-thread bar?), then repeat for the other side. I think that was the way I built my first tailplane many years ago. Some builders at that time were using the perspex technique to get the hole positions - and it worked well - but it seemed like a lot of hard work to me. Drilling the first few holes was the most difficult/nerve wracking, trying to make sure the skin was clamped in the right place over the floppy skeleton. A good solid jig would probably be a great help.

Pete