It’s a big day for the F1Rocket-Hanger because I finally have the both wings in the jigs, and I’m working on getting them leveled in preparation for skinning. I was a bit unsure of how to do this at first. The RV-4 wing assembly instructions want you to drill holes in the spars to determine that the wings are square. I opted for a bit of a different route after reading other build logs.
The first step of the process was to level the main wing spar both laterally (end to end) and level across the height of the spar (basically in the 2 axis of the main spar in its current orientation).
This wasn’t so bad to do, because I spent a lot of time leveling the jig stands when I installed them to the shop floor (spanwise). In the other axis, it was easy to get level, as the jig has a treaded rod and it was simply to move the nuts until the digital level showed 0 or 0.1 which is pretty darn level.
Next I added a plumb bob on each end of the wing, and I used this to get alignment of the rear spar. In this part of the process, you want to ensure that the chord of the rib is vertical. When you can get one side set, then use the plumb bobs to get the other side set. I did this by measuring from a point of the rear spar to the plumb bob. Then adjusted the other side to be the same.
Then I ran a taught string from end to end just up from the rear spar (as yoIu can see in the picture below). I used this as a point to measure up from the rear spar, and this is where you have a jack placed under the midpoint of the rear spar to take up the sag in the middle of the wing (until you can get the skins on). Measure from the spar up to the string, and adjust the jack in the middle until it is the same measurement, all the way across the spar.
Here’s a closer picture of how I set the level on the main spar when measuring level from end to end. I used the oak blocks because the oak is stable, and this allowed me to raise up the level so it’s not sitting on the rivet heads. To confirm what I was reading on the bubble level, I also put the digital level on top. When everything read level, that’s about the best I can do.
I should also add that in these pictures, you can see that I’m using some small bottle jacks. These didn’t work well for me at all. I actually ended up going out to the PrincessAero store and bought 2 screwjacks, and these worked so much better as they don’t bleed down.
That’s all for today folks! Please comment. I love to hear from my readers. Thanks again for coming along for this ride, you make my work worthwhile.