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Wing Don't Fit

Tacco

Well Known Member
Hi guys,

I’m sure I’m not the first. I can’t seem to get my wing pins in. They’re not tight, they just plain don’t fit. After some investigation and fiddling around, I thought it might be because my kit came with oversized rear stub spars, 1207B-25. I was unaware of the difference and installed them. No problem, I figured I just file to fit when I installed the wing. However after taking a little material off the circumference , I’m not convinced this is the issue. The wings seems to “bottom out” in the vicinity of the main spar. With the wing in as far as it will go, I can "wobble" the wing fore and aft, pivoting around the main spar. I certainly don’t what to take too much off the stub spar and risk replacing. Skins are not in contact with anything nor can I see any other interference.

Any ideas?
 
are you trying both wings at the same time ? if so try just one and verify that you can get that in. Also the white nylon blocks can be installed in a way that prevents the wing seating properly, check that out as well.
 
I fought that on mine, finally found out it was the upper spar to fuselage lack of clearance. It is hard to see the interference when you are outside, it is the inner skin that needed to be cut out a bit. Very baffling.
 
Have you checked the spar pinhole to see where the misalignment is? My wing skins had to be trimmed about 1/8? to get mine all the way in.
 
I assume the pins fit through all bushings prior to wing assembly. I experienced difficulties on my first wing install attempt. Work slowly and carefully to observe where the problem is. For me, the first issue was the slots in the side skins. After checking and measuring, I needed to open the top about 1/4 of an inch, and file a little from the front of the slot to clear a couple of slightly proud rivet heads on the spar. That let the wing slide almost home. Then I found the small nylon block an the opposite side was pushing the spar slightly downwards, forcing the pin holes into misalignment. Removed the blocks, touched them up on a scotchbrite wheel a little at a time until everything lined up. Once you have eliminated the points of interference, the pins will push in easily.
Hope this helps.
Cheers,
DaveH
120485
 
I initially had a problem with mine and it turned out I had one of the black rollers the wings slide in on backwards. Sometj=hing to check ...
 
Thanks guys, here is what i've done/know based on your suggestions:

-The rollers are correct
-I checked for clearance of the inner support bracket - it clears
-Skins clear, but I will have to trim when I put on the seal.
-The pins insert fine without the wings inserted.
-Slot clearance is OK top, bottom and sides, all rivets clear

There is a definite "clunk" when I forcefully push the wing in, indicating something solid...possible aft stub spar?

Both wings have issue although very slightly better on right one...again, stub spar?

If it works, here is pic of the amount of misalignment.

AF1QipM3_qCItDe4iLeBgXoRM90zOrWkwTAYL-BmX1Gj
 
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Tacco - I had a similar experience which turned out to be mainly caused by the added F-1270A & F1270D doublers on the outside of the fuselage interfering with the inboard edge of the bottom wing skin. Of course one can't see this unless you have a friend hold the wing in position while your taking a good look from underneath.

Also remember removing just a little material from one of the F-1204R retainer blocks and the lower edge of a F-1204H bulkhead cap so the spar would clear nicely.
 
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Wing Fit,NOT

The fwd wing tabs that I installed were on the wrong wing. There is a left and a right. I had to remove 600 rivets and open up the inboard and center upper wing skins. I ordered new forward spars (3 ft long) very cheap from Vans. Grind down a drift pin to drive in the center rivet pin so the drill won't catch and cause the drill to go off center. The wings now go in without any problems:eek:
 
Thanks guys, here is what i've done/know based on your suggestions:

-The rollers are correct
-I checked for clearance of the inner support bracket - it clears
-Skins clear, but I will have to trim when I put on the seal.
-The pins insert fine without the wings inserted.
-Slot clearance is OK top, bottom and sides, all rivets clear

There is a definite "clunk" when I forcefully push the wing in, indicating something solid...possible aft stub spar?

Both wings have issue although very slightly better on right one...again, stub spar?

If it works, here is pic of the amount of misalignment.

AF1QipM3_qCItDe4iLeBgXoRM90zOrWkwTAYL-BmX1Gj

I don't see "grease the pins" - The KIA says to grease the pins (pg 30-03) After filing the skins, making sure there was no interference from anything my pins wouldn't go in until I greased them.
 
Thanks guys. Have looked at all of these suggestions plus some. No joy. Van's did confirm that the 1207B-25 rear stub spar is the standard issue part, I presume oversize to account for filing and fitting.

For those of you that had skin interference, particularly on the bottom wing skin, did it leave a mark on the fuselage when you were fitting the wing the first time? Mine is close, but not contacting when I stop pushing and get under the wing to look at it. Again, I pushed it pretty hard (audible "clunk) and you'd think it would leave a mark. I'm thinking I might shave off a 16th inch from the shin just to be certain. Will have to do that before I put the seal on anyway.

Thoughts?
 
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One technique to use as an indicator of spar stub length

On our student-built RV-12 completed last spring, we force-fit (don't force it, get a bigger hammer :D) the spar pins and had a painful time removing them. One method we found for determining whether the REAR spar stubs need trimming was to remove the sloping seat pan and then check the spar pin fit. As you tap the pins in, if the vertical bulkhead (where the 12-volt jack is) starts buckling, its a good indication of the spar pins being too long. We marked the edges of the pins with a marker pen, inserted and wiggled a bit, and kept filing the high points off until the pins could be inserted with minimal distortion of that bulkhead. If the FRONT spar stubs are too long, I suspect you would not see the distortion of the bulkhead, so I would start filing the front stubs first in that case. We measured progress by putting a straightedge across the bulkhead and measured the amount of distortion with calipers to verify progress in getting the proper fit.
 
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Thanks guys. Have looked at all of these suggestions plus some. No joy. Van's did confirm that the 1207B-25 rear stub spar is the standard issue part, I presume oversize to account for filing and fitting.

For those of you that had skin interference, particularly on the bottom wing skin, did it leave a mark on the fuselage when you were fitting the wing the first time? Mine is close, but not contacting when I stop pushing and get under the wing to look at it. Again, I pushed it pretty hard (audible "clunk) and you'd think it would leave a mark. I'm thinking I might shave off a 16th inch from the shin just to be certain. Will have to do that before I put the seal on anyway.

Thoughts?

If your alignment is very close and you are not hitting anywhere go get a tailpipe expander from Harbor Freight and slowly line-it up by expand it slowly. Slide the other pin in

https://www.harborfreight.com/medium-tail-pipe-expander-69548.html

No need to pound the pin in :D
 
If your alignment is very close and you are not hitting anywhere go get a tailpipe expander from Harbor Freight and slowly line-it up by expand it slowly. Slide the other pin in

https://www.harborfreight.com/medium-tail-pipe-expander-69548.html

No need to pound the pin in :D

I was just going to mention this when I saw this post. The expander works great. One other thing that threw me initially was that I wasn't raising the wing tip high enough to get good pin alignment. Once I figured out I needed to raise it more than I initially thought necessary, it pretty much fixed my problem ... although I still use a mallet to tap the pins in :)
 
Another method - -

If you clamp a 2" screw clamp on each spar and use a tie-down or such to draw them together it works well and no pounding on pins.
 
When I first fitted mine there was no way to get the pins in. Each wing wasn't in enough making the overlap in the center of the spars about 2-3mm offset (felt with both wings in place and ratchet straps used to snug them up).

It was obvious on mine that the spar stubs were slightly too long stopping the wing seating properly/fully.

To fix this I used the old method of 'painting' the ends with a marker pen (should have ideally used engineers blue but didn't have any).
I then pushed each wing from the tip and gently wiggled up and down so I could see the high point where the ink wore off.
This was then filed lightly and the whole process repeated until the holes lined up.
This was before any root seals were fitted.

It took quite a few hours doing this, I didn't want to risk removing too much material in one go so I basically spent two days doing shallow squats while pushing the wing in with my back :rolleyes:

In the end I left it where the pins are still tight to get in (straps and rubber mallet required) and one pin is slightly harder to get in than the other.

As I don't plan on removing the wings other than inspections I decided I would leave it tight until I have the first inspection, to give them time to bed in if needed.
At the first inspection I may need to do a bit more adjusting to get an easier fit but I'd rather they are tight than lose :D

The hardest part is working out what is stopping them going in. Adding some marking to the stubs and simply pushing them in and wiggling up and down (not too much up down) will show if the stubs are butting up against the carriers or not (no shiny metal where the marker is rubbed off means they aren't touching so something else is fouling)

Just make sure you are 100% convinced that you have the correct point of fouling before getting out the files/snips and go slow with removing material.
I had a similar issue. Check where I have circled in the image in the post at the link below.

http://www.vansairforce.com/community/showpost.php?p=990911&postcount=2

When you put the first wing in can you put your finger in the hole that the pin goes into? How far out of alignment are you?

Just a note that the later kits (mine anyway) had an extra bit of paper with it saying to remove the material you mentioned. It wasn't in the plans if I remember correctly but a sheet of A4 with the part itself. I guess a lot of people had issues with the fitting at that point.
 
Notwithstanding the problems the OP is having, every time I have to remove the wings I'm still amazed that Vans can fabricate and kit wing spars and fuselage with holes that line up so accurately that you can slide (OK, maybe with some persuasion) two pins through four bushings with practically zero tolerance. Very impressive.
 
Definition of sloping seat pan

What part do you mean with the "sloping seat pan" ?
I was using the wrong name--the proper name is seat ramp cover--this is the inspection plate with an aggravatingly large number of screws between the
F-1226-R and -L seat ramp floor parts. I couldn't find the part number. The part you are checking for buckling is the F-1203A bulkhead. The center portion of the bulkhead exposed when you remove the seat ramp cover is what will be buckling
 
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I work on the student built 12's mentioned above in addition to my 12 and a friend's.

We have pretty well established that after gross errors like skin trimming, wrong parts in the spar channel, etc, the stub spar(s) fit is behind tight pin fit.

And as Rob described, removing the seat pan allows the front bulkhead to clearly show the stub spar misfit (bulkhead deforms to unload the stud spar stub misfit by being too wide) is behind the tight pins.

And as mentioned by earlier posters, taking a slow process as described by Madmaveric works.
 
I was using the wrong name--the proper name is seat ramp cover--this is the inspection plate with an aggravatingly large number of screws between the
F-1226-R and -L seat ramp floor parts. I couldn't find the part number. The part you are checking for buckling is the F-1203A bulkhead. The center portion of the bulkhead exposed when you remove the seat ramp cover is what will be buckling

Hi Rob
Thank you for clarification. This helps :)
 
Just to add to the earlier fix for mine. There is a benefit to having a tight spar stub as you can make the fit be more uniformly, meaning more wear would be needed to make it a lose fit.

When I first started marking my stubs, there was only one or two small points that it was touching in the socket.

As I gently removed a bit of the high points each time, the high spots became wider, until I was pretty much having to skim a small amount off the complete radius.
It made it more difficult to 'rub' the ink off as I got further into it as it was now more like a ball and socket, meaning more rubbing was needed to show where it was touching.

In some ways I'm glad it happened as it means the spars are secured with more of a mating surface now, rather than a couple of high spots.

So if you do have to do the procedure, think of it along the lines that you are making a better fit rather than correcting a mistake, it a makes the extra work a bit easier.

In some ways I'm surprised this isn't the standard method of getting these to mate fully (i.e. the stubs start out all oversized) but I guess VAN's has enough data to show it isn't going to cause issues later, and it is a bit of a tedious job on your own.

A correctly fitted wing with high spots would need less wear to become a lose fit as you only need to wear off the high spots, so having to do this gives more wear tolerance in future. whether the extra tolerance is needed or not is a different question.
 
An update. It was indeed the over-sized rear spar stub. Pretty much used the procedure Madmaverick mentioned above. Built a wheeled cart for my saw horses to make the wing removal and refitting a one man operation to facilitate the multiple times I had to do this. Used a dry erase marker to "paint" the ends of the spar to highlight the high spots. I ended up having to remove a fair bit of material - about .025 (not surprisingly). Left the fit a bit tight as I expect things to loosen up after a few landings.

Thanks to all for the help. Every input was valuable.
 
https://www.harborfreight.com/medium-tail-pipe-expander-69548.html

Good advice on the Muffler Expander .....

Our spar pins were VERY stubborn going in. This is what we suggest....

1. Grind down/smooth the ridge on the end of the pins to make it more of a bullet shape.
2. Grease the pins liberally using lithium grease or similar.
3. Insert the muffler expander in one spar hole and use a socket wrench to expand the radius of the muffler expander. That will produce a PERFECT alignment on that side.
4. Now move the wing tips up and down to bring the opposite bushings into alignment (feel the inside with your fingers).
5. Fabricate a shim and wedge it between the spars and the white plastic block in order to bring it into alignment. Ours required a .064 shim.
6. Twist and turn your greased pin into the bushing hole, tapping it with a plastic tipped mallet to until the pin is in place. It gets easier each time.
7. Remove the muffler expander..... and twist/turn/tap the pin into place on that side. Wear shop gloves so you don't slice your hands on the sides.

After inserting/removing the pins a few dozen times, it actually become easy. We use a banquet table with the legs sitting on Harbor Freight moving casters to support a wing when removing it from the fuselage. We fit two RV-12s in one T-hangar.... That requires one wing to be removed from one airplane. Easy enough to do with one person.

I hope this helps.....
 
On our student-built RV-12 completed last spring, we force-fit (don't force it, get a bigger hammer :D) the spar pins and had a painful time removing them. One method we found for determining whether the REAR spar stubs need trimming was to remove the sloping seat pan and then check the spar pin fit. As you tap the pins in, if the vertical bulkhead (where the 12-volt jack is) starts buckling, its a good indication of the spar pins being too long. We marked the edges of the pins with a marker pen, inserted and wiggled a bit, and kept filing the high points off until the pins could be inserted with minimal distortion of that bulkhead. If the FRONT spar stubs are too long, I suspect you would not see the distortion of the bulkhead, so I would start filing the front stubs first in that case. We measured progress by putting a straightedge across the bulkhead and measured the amount of distortion with calipers to verify progress in getting the proper fit.

Rob, I thought this problem was solved, it isn't. I'm seeing exactly what you describe above. Question is: how did you decide which stubs to file down. Did you actually end up filing the front spar stubs?
 
Mine needed skin trimming. About a year later I noticed a click when climbing on the wing to enter the cockpit. I also noticed a slight fore-aft play at the wingtip and ended up using 0.025? shim plates on the spar tongues to eliminate the problem. My shims were shaped like the tongues and wrapped around the bottom edge of the tongues so on end they looked like ?L?s.
 
On both of ours (2016 kits) the fitting of the wings required some gentle effort. We used contact crayon on sub spars, filed the stubs where touching, then had a minor skin issue and then - thunk - the pins fit.

It is a high precision assembly really with some variability due to size and construction. The instructions should include a work through for issues so that guys don't end up grabbing the larger mallet and potentially doing damage.

#1 aeroplane is just waiting for paperwork so we can test fly, #2 had it's first ships power up last night - smoke stayed inside the wires which was a bonus :D

Both first flights will end up on YouTube as per normal on my Trent772 channel.
 
Both of them needed a touch - really not much but you know how little it takes to cause interference.

One was bottoming on the end of the stub, the other was touching on the sloping part but a few careful passes with a vixen and then polish with 320 sorted it out. They are now snug.

There was also a little on the bottom skin which was easily sorted.

We were lucky to be able to assemble on the front lawn on a warm day, so no time pressure - just frustrating on/off/on/off.

When you are doing that - make sure there is no forward motion on the wing as you remove it as the skin of the slot at the front of the spar opening is unsupported and can easily get marked or damaged.
 
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