When I put only the left wing in both right and left pins fit fairly easily. When I put only the right wing in both pins fit snugly. When I put both wings in the pins fit snugly through the spar holes of the left wing, but the holes are out of alignment for the right wing and neither pin will fit. Does anyone have any ideas about what the hang up could be?
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RV-12 iS wings don't quite fit
- Thread starter Jknamwob
- Start date
My favorite tool for this is an Exhaust Pipe Expander. They're on Amazon for $20-30. I can't recall the size of the pins & bushings in the RV-12, so you'll have to get that measurement to select the right size of expander. Put the wings in "loosely" and insert the expander where the pin would go, then gently tighten the expander to cause its outer diameter to increase. That will snug the wing spars into alignment with the bushings. I typically use the expander on one side, insert the opposite pin, then remove the expander and slide the 2nd pin in without force.
there is another thread on this that covered several ways to handle this. https://vansairforce.net/members/wilsonrv12.43234/
( or search "trouble installing wings")
( or search "trouble installing wings")
Piper J3
Well Known Member
The guy is new here. Let's not scare him off. Best to help someone so they understand and build a safe machine...
OK - the issue is not really the tight or loose fit of the pins in the holes in the aircraft and the wing spars. The spar pins and the bushings in the holes are machined to quite tight tolerances & if they get too loose - you replace the bushings. the issue is that because they are a tight fit, the alignment is critical to get the pins in. When the wings are inserted, but the pins are out, the near side of the spar rests on a roller and the far side is hooked under a catch-block that keeps the wing from falling down. The position of those 2 items for each wing determine how well the 4 bushings on each side line up. (one bushing in each wing spar and the 2 bushings on each side in the fuselage). The pins have a 45 degree chamfer which will only pull in a slight mis-alignment.
if the mis-alignment is too large for the pins to pull in, using the exhaust pipe expander will force the holes on one side into alignment - which may change the alignment on the other side enough to allow that pin to be inserted. (don't tighten the expander enough toactually expand the bushings). A helper wiggling one wing up and down may also do the same thing.
If the misalignment is in the "correct"direction, filing the catch block may also help, but make sure its going to help & not hurt. Feeling in the holes to determine the direction the wings have to go to does a lot to help you understand what needs to happen to get the holes lined up
I don't know of any way to adjust the roller up or down.
I also don't know what determines the left-right alignment but that usually is not a problem.
I only take wings off at annual, so I just feel the misalignment in the holes & use a sawhorse to lift one wing to get the first pin in place. If I trailered the aircraft, I would put some more work into getting them to align without external support.
Hope this helps.
if the mis-alignment is too large for the pins to pull in, using the exhaust pipe expander will force the holes on one side into alignment - which may change the alignment on the other side enough to allow that pin to be inserted. (don't tighten the expander enough toactually expand the bushings). A helper wiggling one wing up and down may also do the same thing.
If the misalignment is in the "correct"direction, filing the catch block may also help, but make sure its going to help & not hurt. Feeling in the holes to determine the direction the wings have to go to does a lot to help you understand what needs to happen to get the holes lined up
I don't know of any way to adjust the roller up or down.
I also don't know what determines the left-right alignment but that usually is not a problem.
I only take wings off at annual, so I just feel the misalignment in the holes & use a sawhorse to lift one wing to get the first pin in place. If I trailered the aircraft, I would put some more work into getting them to align without external support.
Hope this helps.
Another RV12 builder and I helped a new builder get his wings installed. The goal should be pins that only require a firm push by hand to get them in - no hammers. One wing fit but was tight, and the other the pin wouldn't go in.
First, check for interference from the wing skins to the fuselage typically underneath the wings. Then, check the slot; the bottom of the slot can catch and push the wing up. Check the white blocks - sand them down so they are not pushing the spar down. You can also remove the blocks if you have enough helpers and check if they are causing an issue.
To fine-tune the fit, very lightly sand the stub spar with 120-grit sandpaper - amazing how a few thousand changed it from hard to get the pin in to a nice firm push. It took a while but ended up with a nice fit. I find having one person on the wing tip gently moving the wing up and down while the pin is pushed in is really helpful.
I will go out on a limb here
and say too tight is not good. If the pins slide cleanly into the spar and the fuselage separately then when the wing is in fuselage they should do the same. If they are tight that means something is pulling the two holes out of alignment. So by forcing the pin in you or using an exhaust expander you are probably crushing the stub spar against the slot or pushing the spar against the white blocks creating tension somewhere else in the system. Or damaging the brass inserts as you hammer an unaligned steel pin into them
Robert
First, check for interference from the wing skins to the fuselage typically underneath the wings. Then, check the slot; the bottom of the slot can catch and push the wing up. Check the white blocks - sand them down so they are not pushing the spar down. You can also remove the blocks if you have enough helpers and check if they are causing an issue.
To fine-tune the fit, very lightly sand the stub spar with 120-grit sandpaper - amazing how a few thousand changed it from hard to get the pin in to a nice firm push. It took a while but ended up with a nice fit. I find having one person on the wing tip gently moving the wing up and down while the pin is pushed in is really helpful.
I will go out on a limb here
Robert
WJaviation
Well Known Member
My wings fit absolutely perfectly snugly on first installation with the pins. It was only after i installed the rubber/foam gasket wing root seal that the fitment became very difficult and I had to use the exhaust pipe expander and use grease on the pins and bushings.
My 2 cents (or less) are that you should sand or otherwise file very gently each of the components the folks in this thread already mentioned. The rear spar stubs, the catch blocks, etc. (never ever the bushings or spar pins themselves) until you can comfortably achieve the snug fitment without any wobbling or loose play anywhere. Then you know definitely you have good metal to metal contact in all axis. Then when you install the wing root seal (I didn't install mine until a few test flights later), and it becomes a PITA, you know its only the compressible root seal that's causing the difficulty.
It took me a lot of on and off with the wings to trim, cut, or bend my root seal to allow the wings to fit better but still seal the root and I still need to use the pipe expander to get them to align.
Again, just my opinion, but I'm all for the "slightly too tight" vote.
My 2 cents (or less) are that you should sand or otherwise file very gently each of the components the folks in this thread already mentioned. The rear spar stubs, the catch blocks, etc. (never ever the bushings or spar pins themselves) until you can comfortably achieve the snug fitment without any wobbling or loose play anywhere. Then you know definitely you have good metal to metal contact in all axis. Then when you install the wing root seal (I didn't install mine until a few test flights later), and it becomes a PITA, you know its only the compressible root seal that's causing the difficulty.
It took me a lot of on and off with the wings to trim, cut, or bend my root seal to allow the wings to fit better but still seal the root and I still need to use the pipe expander to get them to align.
Again, just my opinion, but I'm all for the "slightly too tight" vote.
scottmillhouse
Well Known Member
On both of the legacy RV-12s I built I had to relieve a little metal from the little fill in piece (not structural) from the inside for the fuselage spar box. It interfered with the spar. Probably filed about 1/16 an inch. Instead the rough top of spar could have been smoothed but this was easier.
As we are discussing this topic again, it makes me wonder what the guys at the factory are doing when they install the wings there? Do they never see this issue, or do they have a technique they could share with the rest of us that might be helpful? Seems like it might be worth making a video if they do have any tips.
What I've done to help get the pins in is (after the wings are on which in my case as others have commented is not very easy but do able) is to make alignment marks in a few places that give me a visible target to shoot for when I'm jiggling the wings trying to get the pins in. I have actually gotten then in solo by using padded support stands that are adjustable.
When we went through the initial wing fit, the pieces that prevented pin alignment were the aluminum tabs in the ring root that fit into matching sockets. The front ones were slightly too wide and too deep. Some work with a file let the tabs seat properly into those sockets. Then, the wing pins aligned with their holes correctly. The need for work on these tabs is mentioned in the instructions. As robust as the spar structure is, I doubt anything is off in the spars or carry through. I would resist any temptation to force them into alignment with tooling.
