The closer I get, the slower I go? After a couple days of dithering I finally got up the nerve to drill the first holes to mount the horizontal stabilizer. The tolerances are tight, as you are trying to put an AN3 at the intersection of two ?? angles to tie the HS front spar to the aft deck. The consequences of an error are great, as one of those angles is the longeron.
I nailed the intersection of the two angles, but came up short of edge distance on the F 710-B angle that lies under the aft deck. I?ve only drilled a pilot hole to #40 so far, but when I drill/ream for the bolt I?m going to be close to tearing out on the left side.
It is pretty much impossible to have a normal edge distance here, since the angle has to nest inside the longerons. But way back when I cut that angle, I didn?t have a clear idea of the tolerances here. It seems to be a common problem, and I?ve seen pictures of flying quick-builds that look worse than mine.
There is a lot of conflicting advice about how important the edge distance is. The joint is not usually experiencing much tension (down force on HS), and there is probably little lateral force acting to tear out the F 710-B. One solution is to stick some epoxy in there to give the washer/nut something to bear on, and to move on.
I emailed Van?s, and got this response:
?This happens when the 710B angle is trimmed too short. There's little remedy for it now, I'm afraid, short of replacing the angle with one that's long enough to accept the hole. We don't have any real engineering data on how close is too close. You're not far off, so maybe check with your inspector to see if he/she is happy with it. I must say the riveting work looks first-class.?
The compliment was nice, but I was hoping for some guidance from the engineers. I guess the response, and the fact that this is a frequent and long-standing issue, means that they are not too worried about it. I?ve not heard of a failure of this joint, but it seems important, as these four bolts anchor the front spar of both the HS and the VS.
Since I?m the final inspector, and it will be my butt in the seat, I?ll be drilling off the aft deck and fitting a new F-710B. Most of the rivets will be easy to drill out, and I am confident enough in my skills at this point to make the repair. It still sucks to take the aft section apart though.
The point of this post is to:
1. Alert folks still building to be wary of over-trimming F 710-B.
2. Encourage Van?s to emphasize this a bit more in the instructions.
3. Encourage discussion of a better engineering solution for this joint. Anybody have pictures of how the empennage is attached in other designs? Van?s kit is great, but it is still just a starting point, especially when the engineers do not provide specifications in this area.
I nailed the intersection of the two angles, but came up short of edge distance on the F 710-B angle that lies under the aft deck. I?ve only drilled a pilot hole to #40 so far, but when I drill/ream for the bolt I?m going to be close to tearing out on the left side.
It is pretty much impossible to have a normal edge distance here, since the angle has to nest inside the longerons. But way back when I cut that angle, I didn?t have a clear idea of the tolerances here. It seems to be a common problem, and I?ve seen pictures of flying quick-builds that look worse than mine.
There is a lot of conflicting advice about how important the edge distance is. The joint is not usually experiencing much tension (down force on HS), and there is probably little lateral force acting to tear out the F 710-B. One solution is to stick some epoxy in there to give the washer/nut something to bear on, and to move on.
I emailed Van?s, and got this response:
?This happens when the 710B angle is trimmed too short. There's little remedy for it now, I'm afraid, short of replacing the angle with one that's long enough to accept the hole. We don't have any real engineering data on how close is too close. You're not far off, so maybe check with your inspector to see if he/she is happy with it. I must say the riveting work looks first-class.?
The compliment was nice, but I was hoping for some guidance from the engineers. I guess the response, and the fact that this is a frequent and long-standing issue, means that they are not too worried about it. I?ve not heard of a failure of this joint, but it seems important, as these four bolts anchor the front spar of both the HS and the VS.
Since I?m the final inspector, and it will be my butt in the seat, I?ll be drilling off the aft deck and fitting a new F-710B. Most of the rivets will be easy to drill out, and I am confident enough in my skills at this point to make the repair. It still sucks to take the aft section apart though.
The point of this post is to:
1. Alert folks still building to be wary of over-trimming F 710-B.
2. Encourage Van?s to emphasize this a bit more in the instructions.
3. Encourage discussion of a better engineering solution for this joint. Anybody have pictures of how the empennage is attached in other designs? Van?s kit is great, but it is still just a starting point, especially when the engineers do not provide specifications in this area.
