After discussions with Van’s regarding this subject, I developed a plan of action. The first step is to snap a chalk line for the aircraft centerline. To determine the A/C centerline, I attached two plum bobs, one that dropped from the center rivet on the bottom of the firewall
(I also measured to double-check that this was indeed the center of the fuselage), and another at the aft fuselage tie down.
Now before you snap that chalk line, double check something…with the fuselage where it is, do you have enough room to put the wing on? If the answer was yes, then you’re ready for that first chalk line now! Once you have your centerline, then it is time to put the wing on. (You can do this first, but it’s a whole lot easier to move the fuselage with the wing off!
For instructions for putting the wing on, I will refer you back to your builders’ manual. Their directions worked just fine for me.
Once the wing is on, it is about time to snap the chalk line for setting the wing sweep. To do this you need to snap a line that is 90° (perpendicular!) to the A/C Centerline. A “T” square at the A/C Centerline helps to get everything perpendicular, but I figured that I might as well use my college education for something, so I took it one step further! To make sure that the wing line was perpendicular to the A/C Centerline, I marked a point 12 feet down the Fuselage Centerline (from where I wanted to wing line to start), and then made a line parallel to the Fuselage C/L at you guessed it 12 feet! Using the following picture, and a little math, I measured from the 12 ft point on the Fuselage C/L 16.97 feet (16’ 11.64”) to the 12 ft wing line. Where the 16.97 ft line intersected the 12 ft wing line is the endpoint for the wing line. Mark this point and re-measure the wing line to make sure that it is indeed 12 feet from the Fuselage C/L. Once you have double checked, you can snap the wing chalk line and you are ready to set the wing sweep!
To set the wing sweep drop two plum bobs from the wing, one at the root and one at the tip. If you have to cannibalize one (like I did…the hardware store only had 3) or two of your counterweights from the fuselage, you can make some crude counterweights from some string and a relatively heavy fishing weight (preferably not the crush type that I always attached to the line with my teeth when I was a kid). Once you’ve got the plum bobs in place, get the fuselage re-centered, and line the wing root plum bob up to the wing line. With the fuselage securely in place (have someone hold the tail unless you’ve got it really secured well) move the tip of the wing until the plum bob is over the wing line. Once you’ve done this, double check the rest of the plum bobs to make sure none of them have moved. If they haven’t then you are done setting the sweep, and it is time to move onto the wing incidence.
For instructions for putting setting the incidence, I will refer you back to your builders’ manual. One tidbit I got from the guy’s at Van’s with regards to incidence and sweep was that if it isn’t perfect, (plus or minus a little) make sure that both wings are the same, as that is the most important thing.
Hopefully with this information anyone who (like me) is building in a confined area will be able to set their wing sweep and incidence without any problems!
Happy Building!
