Sling Pilots Forum

I would like the community's take on my issue. Also, asking the official advice from #slingsupport.

My garage floor is rather uneven. I built my wing using two tables and setting up the jigs on top of them. Fine-tuning to set the jigs level is required, as expected. The final step to my wing assembly was installing the top skin. I made sure the digital level meter shows 0.00 degrees difference between the two jigs.

Confident in my set up, I started pulling top skin rivets starting from the wing root and working my way through to the wing tip. At approximately 75%-80% of the way and around where the leading-edge skin overlaps (where the landing lights are housed), I remeasured the jigs. This time it showed 0.15 degrees difference. I can only assume how this happened, perhaps I accidentally pushed the tables or the skin tension as I pulled the rivets caused the jigs to move over the tables. I am really not sure although I tried to be careful.

Without thinking too much, I readjusted the jigs back to 0.00 and finished up riveting the top skin. The wing tip rib and fiberglass are not installed yet.

I am now wondering whether the wing is level. I can't tell at which point the slight angle was introduced to the wing structure. I know that I started and finished installing the top skin level. I didn't have any issues with the bottom skin, during prior steps. Some final thoughts/questions:

- The wing tip is much lighter, so any distortion would appear close to that jig. By making sure it's completely level before pulling the final 20% rivets, perhaps I saved it?
- Is there a way I can assess my work and confirm the wing is level without having to fly?
- Is the wing structure solid after the wing jig level correction?

I appreciate your thoughts/advice.

#slingsupport

So this is my take on your situation. Take it for what it's worth. Sling support will be a better source of guidance.

Having built a couple of wings I feel like I have a good bead on the critical nature of the "levelness" of the table. I leveled out my table using a laser guide and I feel it stayed put pretty well during the build. The jigs that go on the end are meant to help to keep the main spar and rear spare square - that's going to be one part of the assembly. The holes in the skins are (again - my experience/guesswork here) very precise in their holes. If you were having problems with the skin hole alignment when you were putting the leading edge skin together then I would agree you may have an alignment issue. But if they leading edge skins go on smoothly and/or the holes lined up correctly with little effort in pulling the rivets, you're probably fine.

In other words - if the table was incorrect and you pulled the skins to their holes it would (or should) have lifted the wing into alignment. The holes wouldn't have fit otherwise.

Of course if you're talking about the fuel tank skins not lining up, then you may have committed the sin I did where the back part of the fuel tank (that locks the tank square) was put on in the stand/jig vs. on the wing itself. The jig pattern and stand isn't meant for assembly - it's just a stand and that's it. I put my rear fuel tank on in the jig which resulted in a twist in the fuel tank making it impossible to put onto the wing. The levelness of the table wouldn't have anything to do with that as the fuel tank rivets onto the wing spar and no amount of twist in the wing would be able to cause the spar to flex that much.

So - 99% chance you're totally fine, but I would still have technical chime in on it to get it over that last 1%.

Hi Brian. Thank you for the reply. I spoke with the factory and they mentioned that the introduced misalignment is too small to be material. They believe this won’t affect structural integrity, flight characteristics or performance.

I witnessed your fuel tank struggles over YouTube. You bounced back pretty nicely

Hi Brian, would you please share a link to the sealant eraser that you used during your fuel tank extravaganza? As you can imagine, I messed up...

Here ya go -

It works like a champ.

If you have any other questions on it definitely let me know.