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Wing spar replacement

acam37

acam37

Well Known Member
While stabbing the wings on our "never ending" project we discovered a major malfunction on our right wing spar where it stabs into the fuse. It appears that during the original construction of the spar, someone took it upon their self to grind a piece off of two of the lower leaf sections that make up the lower portion of the spar thus compromising the critical bolt edge distance. We contacted Vans and they said plain and simply "not airworthy"
Now, what is the best approach to replacing the spar and salvaging the wing? Who has had to take a wing back apart. And no, we are not in a position to buy a new wing kit. The engine overhaul made sure of that.
 
Couple questions

I'm trying to fully understand your dilemma. The spar has an upper and lower laminated "cap" made of bars with a web in between.There are actually two separate webs on the inboard half of the spar running out past the tanks, with space in between them. The holes are factory drilled, and you are speaking of edge distance issues,so I have to assume you are looking at replacing a couple of the capstrip laminations because they were trimmed? The RV-4 spar would not easily be removable, however it may be possible to remove a single lamination, but in all likelihood you will need to have the tanks removed and partially remove the lower skin. The rivets that are installed through the spar build-up are 3/16" diameter and fairly long. this will need done very carefully, and re-installing will be no joy. There are bolts in there also at rib attach points. You may want to post some pictures. Either way, a new spar isn't likely needed if you only have a couple pieces of it damaged...just going to be more disassembly than you had planned on.
 
Advice

Once you drill out the wing spar, a lot of the river holes will be oversize in the skin and ribs because of the thin metal used and because it's impossible to get them all out without some hole growth. If a wing kit is out of the question, plan on dealing with oversize holes. I would hate to have to step up a hole in a new spar because I couldn't afford to buy or make new ribs and skins. Just a thought.
 
Bolts

Check with Vans to see if engineering would allow bolts in lieu of rivets on this repair. That would make it much easier
 
Only the two outer leafs are effected. I also thought about just replacing the two. After looking at the plans I don't see a reason why not? This plane has become my personal nightmare. After this screwup is fixed there's nothing left. Practically everything else has either been repaired or replaced.
 
Hang in there Arlie.
This isn't as bad as you think. If you have not removed any of these large rivets before, there are some challenges, but frankly, they are easier than smaller rivets on sheet.
I can guide you, having removed literally hundreds, on Spar Caps.
Access is going to be your biggest challenge to remove and then set the new rivets, but it is not hopeless.
Plan on using a drill guide when you match drill your holes. You can turn them out easily on a lathe and many sizes are available commercially for not a lot of dough. You should be able to avoid too many oversized holes.

Let us know how we can help.
 
Look deeper!

Hi Arlie

I don't want to add to your problems but the only reason someone would do this is because the spar would not fit into the spar box. Before you go any further check the dimensions of the spar box to make sure a normal spar would fit in.

The next issue is that the new spar would need to be really carefully drilled to match the existing holes in the spar box, so dont buy one that is already drilled it probably wont match your existing holes. When I bought a project that needed a spar replaced I cut off the inboard end and sent it to Phlosigon who build Vans spars to have it match drilled.
 
Here is a picture of the spar laminates in question. There is no reason as to why they were cut. It appears this was done before they were riveted together by the way they are different lengths and height.
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[/URL][/IMG] I am still weighing my options on how to go about fixing the problem.
 
Sorry

I am sorry to hear that and I hope you find an easy and cheap resolution soon! When I look at some of your posts it makes me believe that whoever built your plane was also talking to my builder too. I don't think I have the spar issue like you do but believe me I have found enough issues along the way similar to yours, rear spar for example. You have done a beautiful job and keep pressing on!!!! When you fly it for the first time you will realize it has all been worth it.
 
Sorry I can not help with your specific question, but I did look at your photos. WOW, you are a brave man taking on that job. With the things you already found, surely this was not a surprise. Excellent work, though, you should have a nice plane when done.

You certainly have the skills to do what ever is needed to finish those wings. Hang in there, It looks like you are close to completion!
 
True to having to remove rivets and bolts, that's the easy part. But the skins are installed from in to outboard, and the ribs face outboard as well. This requires both skins to be removed to access that far inboard to be able to remove the bolts, buck the massive 3/16" rivets and the 3/32" skin rivets back on. If you're removing the rivets correctly... drill the head, punch out the stem, oversize holes shouldn't be a problem. Then use the original to dill out the new.
All together, I'd say you've got a better chance at ruining your ribs by re-skinning, than it's worth, as they're not very forgiving and replacement skins from vans don't come pre-drilled. And of course Vans is going to say it's unairworthy, but with the steel plates on either side, other than unsightly I can't see how this would ever be an issue in flight.
 
It has begun

Because I have a partner in this project, sometimes we are not in agreement as to what direction to go. After more debate than congress, we decided to go ahead and replace the two pieces that were cut. So we removed the bottom skin and leading edge. No problems at all. I've got really good at drilling out rivets. On to the spar cap. First we knocked off all the shop heads with a sharp air chisel. Then we removed one piece of flat bar at a time. After the first piece was off we sheared off the protruding rivet the same way we did the rivet head. With a Sharp chisel this is effortless. After the two bad pieces were removed, the rest of the spar can be taken out in one piece. We then used a hydraulic press with a slightly less than 3/16" drift punch and pressed the rest of the rivets out. No drill needed, so all the holes are still perfect. All this in 8 hours.
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Holy *\%#??\!

Arlie, from someone who just finished their wings......when I started reading this thread, I thought.....how bad could the damage be from the previous builder. When I saw those damaged bars, I bout lost it. It's heartbreaking and SO de motivating to have to tear that deep back into something like that. That said, well done. Tedious work to keep those big holes round. Smashing new 6's in there though will be noisy, but fun. I loved doing my spars. (My neighbor didn't share my joy)

Now you KNOW what the inside of the wing looks like, at least. Here's to just another bump in the road.

Cheers my friend,

Gregg
 
I did not see how many hours were on this plane or how it was flown (aero?), but if any spar was going to crack, that corner notch would have been the place. Surprising it has not already begun.

These spars must have some very good margin when built properly.
 
BillL said:
I did not see how many hours were on this plane or how it was flown (aero?), but if any spar was going to crack, that corner notch would have been the place. Surprising it has not already begun.

These spars must have some very good margin when built properly.
Click to expand...

No kidding! Can you say "stress riser?" Yikes.
 
Just like so many other parts of this hobby, the hard part is the head scratching and getting started. Great work and a much bigger challenge than just building as you are in uncharted waters. Now should have a good safe airplane and after this not much is going to intimidate you!
 
Good work

Arlie,
I can't imagine how you felt when you first saw that but good job on the repair! I would love to see your chisel method on removing the rivets. Could you post some pictures of it. I still have to do my rear spar and might want to use that method of removing the rivets. Sounds safer than drilling rivets.
 
I hope you double-checked to make sure that there's enough room inside the fuselage bulkhead to get the new spar in and the holes drilled with proper edge distance. It would be a shame to have issues there after all this much work.

Dave
 
Arlin,
My heart aches for the work you have had to do, I do not post on everything but have kept up with your project...
As you already know One project at a time and stay focused and you will be victorious.
Smilin Jack
 
Parts are on order, so when we get ready to re-attach the bottom skin, do we need a wing jig or should everything go back straight because the skin and leading edge is already match drilled. I see where others lay the wing down flat after all the ribs are installed and the top skin is riveted. So basically that is where we are at this point.
 
I'm sure Scott will chime in but since you are reusing the bottom skin and ribs, you are basically at the same point as anyone building a -7 or higher is at when they are ready to start riveting. Meaning, no jigging is required.

The techniques you have employed in your rebuild are impressive. I look forward to reading about your upcoming first post-rebuild flight!
 
We got our new flat bar and the lower spar leafs are match drilled and ready to be riveted back on. The problem now is that my rivet gun is not up to the task. I've got to find someone local with either a pneumatic squeezer or a bigger rivet gun and bucking bar. Until I get those 3/16 rivets bucked we are at a stand still.
Any suggestions?
 
Persistence persistence persistence

Argie, you take the award for sheer persistence and not knowing the word "quit"!! And also being the Master of Rivet Removal!

Really impressive work, and surely there cannot be much left now?? You've made me feel like a wimp for giving up on my own rebuild but I just don't have your skills.

After all this work you will have a safe plane that you can have confidence in when you start to throw it around.

Airborne soon, then the fun starts.

Chris
 
I'm not sure a CP 214 squeezer will manage that, worth a try, crank up the pressure. Or you could get a 4x or bigger gun and do it.

Dave
 
acam37 said:
We got our new flat bar and the lower spar leafs are match drilled and ready to be riveted back on. The problem now is that my rivet gun is not up to the task. I've got to find someone local with either a pneumatic squeezer or a bigger rivet gun and bucking bar. Until I get those 3/16 rivets bucked we are at a stand still.
Any suggestions?
Click to expand...

A C-Frame and big hammer will do the trick if you can figure out how to manuever the wing so the C-Frame can sit on a solid surface like the floor.
 
Here in East Tx. my access to specialized tools are limited to non-existant. There are a few builders and A&P guys but they are not too happy to loan tools. I do have a C-Frame that I built. It has worked great for dimpling and back riveting small items. I guess I could give it a shot on a test piece to see if it will hold up to a big hammer.
The rest of the plane is finished except for a little fiberglassing and a few trim items that can be done later. But the major airframe repairs are done. The engine is still in pieces, but we have everything to put it back together.
As for the wing, all that's left is pounding (75) 3/16 rivets and about(500) 3/32. Since the bottom skin was off I also rebuilt the rear spar attach bracket so we have a clean slate to drill the rear spar holes without having to match drill existing holes.
 
rent one

Vans used to rent out or loan out a big squeezer to guys to use when building the spar. Not sure now that probably nobody builds the spar anymore.

cm
 
Rivet gun

Who would have thought how difficult it is to find a 6x rivet gun? A local A&P who is also an RV-4 owner had a big rivet gun but could not find it. I struck out everywhere else also. I don't want to buy a gun to drive just a few rivets, but I may not have a choice. I tried my home built C-frame on a test piece but it won't work. So I guess I am dead in the water until I can get those rivets pounded. I did locate a 4x gun, but not sure if it is strong enough.
People don't build their own spars anymore.
 
acam37 said:
Who would have thought how difficult it is to find a 6x rivet gun? A local A&P who is also an RV-4 owner had a big rivet gun but could not find it. I struck out everywhere else also. I don't want to buy a gun to drive just a few rivets, but I may not have a choice. I tried my home built C-frame on a test piece but it won't work. So I guess I am dead in the water until I can get those rivets pounded. I did locate a 4x gun, but not sure if it is strong enough.
People don't build their own spars anymore.
Click to expand...

I sent you a PM via email. Did you get it?
 
Should work

Try shooting the normal way, if that doesn't work, shoot them backwards (gun on the shop side). When a gun is "marginal" for power, momentum of the bar bouncing is just as important as it's mass. You will be able to hear the gun hit twice and the bar once if you listen for it (holding to loose).
If you shoot them backwards, the rivet set should be backed up on a concrete slab so it doesn't move at all. Holding the set in a block of wood works well. A back rivet set will help maintain control.
Good luck!
 
You might look into the process of of annealing the rivets before installation. In this case, it might be worth the effort doing the research.
 
I don't think annealing or heating the rivets would be wise in a spar application. I would be afraid it would drastically change the shear properties of the rivet thus compromise the integrity of the spar. I think I will go ahead and try the 4x gun that a friend has offered to lend me. Im not going to let 65 rivets shut me down. Thanks for all the advice and words of encouragement.
 
Dang Arlie.....

If I had a gun that would work for you, I'd ship it to you tomorrow. I borrowed a 10x gun when I built mine. That thing was like a jack hammer....

Wish I could help.

I have family in Ft worth. Next time I go see them, I might have to detour your way.

Take care and good luck.

Gregg
 
I'll call Vans and speak to someone there. I heard they no longer lent tools, but never personally checked into it.
 
If there is a precision sheet metal shop nearby with a press brake you might get them to rivet it up for you at reasonable cost. If it were me I'd want to help to make sure they did it right but depending on their clientele they may already be familiar with aerospace quality standards....
 
3lb Hammer

When I built my spars in 2008 I used Avery's C-channel tool and a 3lb hammer. Find a nice flat spot on the floor and protect the spar from accidental strike with plywood. Oh yeah, earplugs!
 
Arlie,
One of the methods used in the old RV days was an arbor press and big hammer. Modify the arbor press (cheap HF is fine) to hold the set, set on a concrete floor with proper supports for the spar, put the ram on the shop head side, one person applies pressure with the handle while the other person whacks the top of the ram with a big hammer. Was reported to work well. I know there was an article on it in the RVaitor.
Good luck!
 
Loaner tool

Ok, I called Vans and for anyone interested they still rent out a rivet squeezer that will do the job. The cost is a $400.00 deposit plus shipping and $10.00 a week. Problem solved and it only took 46 posts for me to figure this out. So maybe in a week or so I can post a picture of a repaired wing spar.
 
acam37 said:
Ok, I called Vans and for anyone interested they still rent out a rivet squeezer that will do the job. The cost is a $400.00 deposit plus shipping and $10.00 a week. Problem solved and it only took 46 posts for me to figure this out. So maybe in a week or so I can post a picture of a repaired wing spar.
Click to expand...

I hope you paid for the express shipping. I've been getting bored, waiting to see your progress. :D
 
acam37 said:
...I tried my home built C-frame on a test piece but it won't work. ...
Click to expand...

Did you build a hammer-operated C-frame like this one, or a DRDT2-style. I had no problem riveting up my HR2 (clipped RV-4) spars with Avery's C-frame and a 2 or 3 lb hammer. The DRDT2 will not even come close generating the force required to set a #6 rivet.
 
longranger said:
Did you build a hammer-operated C-frame like this one, or a DRDT2-style. I had no problem riveting up my HR2 (clipped RV-4) spars with Avery's C-frame and a 2 or 3 lb hammer. The DRDT2 will not even come close generating the force required to set a #6 rivet.
Click to expand...

Me too Miles. Beat them into submission. The ram mushroomed a bit on the head but that just added character and a slightly larger strike area. Been using this one for 18 years or so.
dyrb61.jpg


If I want to get really serious, I pull out the jaws of death, but it takes two strong men and a mule to use.
iz6vsk.jpg
 
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