goatflieg
Well Known Member
This is old news to some, but I didn't see anything when I searched, so I'll share my experience.
I was working on mounting my vertical stabilizer onto my QB fuselage. I had questions about squaring up my VS for Van's builder support, and got good advice. While I had them on the phone I asked them if the pilot hole near the bottom of the tail bulkhead could be used as a pilot hole for the lowest of the three bottom bolts that attach the rear spar to the fuselage; it looked about right on the plans. They said that should work fine; that hole isn't as critical as the two holes above that need to be drilled through the hinge bracket, spar, bulkhead and tail spring mount. So I drilled a #40 hole through the tail spring mount in the center of the existing pilot hole in the aft bulkhead, which was about #12 in size. Got my vertical stabilizer mounted, clamped square and centered and used the #40 hole to mark the location on the back of the rear spar with the drill punch. I drilled the #40 hole through the back of the rear spar, remounted it with a cleco, and everything was lining up and centering well... but when I began calculating where the upper two bolts were supposed to go, the vertical distance didn't match the plans at all. The plans called for the vertical spacing between centers of the upper holes to be 7/8"... but the actual distance I needed from my existing bottom hole was almost 1-3/4"! I called Van's back, and they said yeah, that's something that they've known about awhile; the actual vertical spacing is 1-23/32". I breathed a big sigh of relief; that would work very well with my existing hole. After a careful layout, the upper holes were drilled accurately, all three holes were sized out to 1/4" per plans, and placed just where I wanted them. But I thought I'd put this out for other builders.
To recap: DWG 73, View A-A gives an incorrect vertical spacing of 7/8" between the centers of the one lower and two upper mounting bolts on the bottom of the vertical stabilizer rear spar. The correct vertical spacing is 1-23/32".
I was working on mounting my vertical stabilizer onto my QB fuselage. I had questions about squaring up my VS for Van's builder support, and got good advice. While I had them on the phone I asked them if the pilot hole near the bottom of the tail bulkhead could be used as a pilot hole for the lowest of the three bottom bolts that attach the rear spar to the fuselage; it looked about right on the plans. They said that should work fine; that hole isn't as critical as the two holes above that need to be drilled through the hinge bracket, spar, bulkhead and tail spring mount. So I drilled a #40 hole through the tail spring mount in the center of the existing pilot hole in the aft bulkhead, which was about #12 in size. Got my vertical stabilizer mounted, clamped square and centered and used the #40 hole to mark the location on the back of the rear spar with the drill punch. I drilled the #40 hole through the back of the rear spar, remounted it with a cleco, and everything was lining up and centering well... but when I began calculating where the upper two bolts were supposed to go, the vertical distance didn't match the plans at all. The plans called for the vertical spacing between centers of the upper holes to be 7/8"... but the actual distance I needed from my existing bottom hole was almost 1-3/4"! I called Van's back, and they said yeah, that's something that they've known about awhile; the actual vertical spacing is 1-23/32". I breathed a big sigh of relief; that would work very well with my existing hole. After a careful layout, the upper holes were drilled accurately, all three holes were sized out to 1/4" per plans, and placed just where I wanted them. But I thought I'd put this out for other builders.
To recap: DWG 73, View A-A gives an incorrect vertical spacing of 7/8" between the centers of the one lower and two upper mounting bolts on the bottom of the vertical stabilizer rear spar. The correct vertical spacing is 1-23/32".
