NavyS3BNFO
Well Known Member
I hope this is helpful for anyone else with this issue in the future. I searched the forums but only came up with sporadic information so I thought I’d document my steps to fix it.
I finished mounting both flaps to my wings and noticed there was approximately a ¼” gap between the upper wing skin and the flaps. Looking at several other build logs that didn’t seem right. The upper wing skin on most other builder’s pages seem to be touching he leading edge of the flap skin. Vans doesn't address it - at least in the wing construction.
Before:
So after searching the forums it seems that this problem has come up a few times in the past. Although there isn’t much info based on the few posts I found it seems that the culprit is the flange on the rear spar isn’t bent enough and needs further bending. I’m not sure if the flange on my rear wing spar came under bent from the factory or in the process of dimpling the spar, the flange became slightly unbent. I’m leaning toward the latter.
Several posts referenced a special tool that Vans has to bend the spar to the correct angle so I reached out to Sterling at Vans who put me in touch with Dale who then shipped me out the special tool. The tool is a loaner so you pay shipping and a deposit and send it back when you’re done.
As you can see the tool clamps onto the flange of the rear spar. The skin side of the clamp is slightly convex to you can make the bend and the spar side has a relief machined into it to accommodate the shop heads of the rivets. There is a hex screw to tighten it once you have it positioned. I suppose you could make up your own tool to fix this but I doubt it’s do as good a job.
I started out with my left wing since it seemed to be slightly worse than the right. I clamped the tool to the spar flange and made small bends as I went down the spar. I was VERY hesitant to wrench on the spar for fear of cracking something so I went slow and probably took the flap on and off a dozen times to check the fit. I wanted the wing skin to just kiss the flap through its range of movement.
The problem I kept having was I could get the skin to touch the flap when the flap was up but as I moved the flap through its range of motion, the gap would open up again. I wasn’t comfortable bending the flange any further and set it aside hoping for divine intervention. This process occurred over several work sessions since it took a while for me to get comfortable bending my precious wing.
I decided to move onto the right wing to see if I would have better luck. As with most things in the build what took several days and works sessions on the first wing took about 15 mins on the second wing. I started at one end of the flap and worked my way down clamping and unclamping and bending as I went. Of course the flap has to come off while you’re doing this. When I put the right flap back on and checked for fit it was almost perfect. Plus the gap didn’t open up as I moved the flap through its range of motion. That got me wondering what the difference between the left and right flaps was.
When I took a close look at the left flap I noticed the radius of the leading edge bend was smaller than the right. That was what was causing the gap to open up as I moved the flap through its range of motion. So I took the left flap back off the wing and gently adjusted the radius of the leading edge bend to match more closely the right flap. It’s possible the flap skin came bent that way from the factory or I somehow added some additional bend when I riveted it to the spar. I’m betting on the latter here also.
Once I put the left flap back on it was just about perfect and the gap didn’t open up as I moved the flap through its total range of motion. I actually had to go back and unbend the spar flange a bit since I had bent it too far trying to close the gap as I lowered the flap. I had bent it so far that it was almost binding when it was close to being in the fully up position. Now that the spar flange was bent correctly and the flap skin radius corrected it moved with little to no effort and the gap didn’t open like before and the skin stayed in contact with the flap during the entire range of motion. I still had to tweak a couple places along the spar to get them spot on but they were very little tweaks.
So as I said in the beginning, I hope this is helpful for anyone else who encounters this issue.
After:
I finished mounting both flaps to my wings and noticed there was approximately a ¼” gap between the upper wing skin and the flaps. Looking at several other build logs that didn’t seem right. The upper wing skin on most other builder’s pages seem to be touching he leading edge of the flap skin. Vans doesn't address it - at least in the wing construction.
Before:
So after searching the forums it seems that this problem has come up a few times in the past. Although there isn’t much info based on the few posts I found it seems that the culprit is the flange on the rear spar isn’t bent enough and needs further bending. I’m not sure if the flange on my rear wing spar came under bent from the factory or in the process of dimpling the spar, the flange became slightly unbent. I’m leaning toward the latter.
Several posts referenced a special tool that Vans has to bend the spar to the correct angle so I reached out to Sterling at Vans who put me in touch with Dale who then shipped me out the special tool. The tool is a loaner so you pay shipping and a deposit and send it back when you’re done.
As you can see the tool clamps onto the flange of the rear spar. The skin side of the clamp is slightly convex to you can make the bend and the spar side has a relief machined into it to accommodate the shop heads of the rivets. There is a hex screw to tighten it once you have it positioned. I suppose you could make up your own tool to fix this but I doubt it’s do as good a job.
I started out with my left wing since it seemed to be slightly worse than the right. I clamped the tool to the spar flange and made small bends as I went down the spar. I was VERY hesitant to wrench on the spar for fear of cracking something so I went slow and probably took the flap on and off a dozen times to check the fit. I wanted the wing skin to just kiss the flap through its range of movement.
The problem I kept having was I could get the skin to touch the flap when the flap was up but as I moved the flap through its range of motion, the gap would open up again. I wasn’t comfortable bending the flange any further and set it aside hoping for divine intervention. This process occurred over several work sessions since it took a while for me to get comfortable bending my precious wing.
I decided to move onto the right wing to see if I would have better luck. As with most things in the build what took several days and works sessions on the first wing took about 15 mins on the second wing. I started at one end of the flap and worked my way down clamping and unclamping and bending as I went. Of course the flap has to come off while you’re doing this. When I put the right flap back on and checked for fit it was almost perfect. Plus the gap didn’t open up as I moved the flap through its range of motion. That got me wondering what the difference between the left and right flaps was.
When I took a close look at the left flap I noticed the radius of the leading edge bend was smaller than the right. That was what was causing the gap to open up as I moved the flap through its range of motion. So I took the left flap back off the wing and gently adjusted the radius of the leading edge bend to match more closely the right flap. It’s possible the flap skin came bent that way from the factory or I somehow added some additional bend when I riveted it to the spar. I’m betting on the latter here also.
Once I put the left flap back on it was just about perfect and the gap didn’t open up as I moved the flap through its total range of motion. I actually had to go back and unbend the spar flange a bit since I had bent it too far trying to close the gap as I lowered the flap. I had bent it so far that it was almost binding when it was close to being in the fully up position. Now that the spar flange was bent correctly and the flap skin radius corrected it moved with little to no effort and the gap didn’t open like before and the skin stayed in contact with the flap during the entire range of motion. I still had to tweak a couple places along the spar to get them spot on but they were very little tweaks.
So as I said in the beginning, I hope this is helpful for anyone else who encounters this issue.
After:
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