aft fuselage not lining up well

[tmbg]

two issues:

one is, when I drilled my tailspring mount, it wasn't perfectly aligned with the longitudinal centerline of the fuselage, so with the tailspring installed it's slightly cocked to the left. Is this going to cause me a problem, or is there enough adjustment and/or slop in the chains to compensate?


Second, in clecoing the aft fuselage together, the rear skin (the thick bit that the tailspring mount goes through) is a real bear to get in place. I've got the side skins on top, followed by the belly skin, and lastly the aft belly skin, so that all seams face down and aft for the best water rejection. It sorta fits ok like that, but it's a pain. Problem is, when I cleco in the aftmost bulkhead, it visibly twists the whole assembly. The aft fuse is pretty straight before that, but putting in that bulkhead really seems to deform things. How should I go about straightening that up?

[bullojm1]

one is, when I drilled my tailspring mount, it wasn't perfectly aligned with the longitudinal centerline of the fuselage, so with the tailspring installed it's slightly cocked to the left. Is this going to cause me a problem, or is there enough adjustment and/or slop in the chains to compensate?

Your plane will want to naturally turn all the time with the mount cocked. If you keep a little pressure on one of the pedals while taxiing, it will be fine. Mine isn't 100% straight either.

Second, in clecoing the aft fuselage together, the rear skin (the thick bit that the tailspring mount goes through) is a real bear to get in place. I've got the side skins on top, followed by the belly skin, and lastly the aft belly skin, so that all seams face down and aft for the best water rejection. It sorta fits ok like that, but it's a pain. Problem is, when I cleco in the aftmost bulkhead, it visibly twists the whole assembly. The aft fuse is pretty straight before that, but putting in that bulkhead really seems to deform things. How should I go about straightening that up?

Yeah, that rear skin is a real PITA. It never really looks proper until it gets riveted together. As far as the twist goes, I would call Van's on that one. I would be willing to say it's no big deal.

[cjensen]

I would agree with Mike on both points.

The twist can more than likely be removed by drilling the holes to 1/8, rather than 3/32. I did this on mine just to make the fit easier, but it could be used to straighten things up a bit by moving the holes in whatever direction necessary.

[tmbg]

I forgot to mention that I have not yet drilled any of this... so is there a method I could use to get it sorta halfway clecoed in but straight, and drill and cleco as I go to keep it straight?


Also, should I consider welding up the holes in the tailspring mount and redrilling it? I am confident that I could weld it back up to as-new, I even have 4130 filler, just wondering if it's worth the hassle.

[bullojm1]

I forgot to mention that I have not yet drilled any of this... so is there a method I could use to get it sorta halfway clecoed in but straight, and drill and cleco as I go to keep it straight?

With match drilled parts, I don't know of any other way of drilling things together other than clecoeing every couple of holes and drilling the other ones. You don't want to wing it too much or else you would have some pretty nasty misalignment. I would say just cleco and go for it. If the very very aft of the fuselage is a little twisted I don't think it would be a big deal. My bet is it will untwist itself once it is put together with the rest of the fuselage.

Also, should I consider welding up the holes in the tailspring mount and redrilling it? I am confident that I could weld it back up to as-new, I even have 4130 filler, just wondering if it's worth the hassle.

This is a call totally by you. If the tailspring is 1 degree off, it's probably not worth worrying about. If it's 10 degrees off, probably worth fixing. In the end, whatever makes you sleep at night. You are obviously worried about it because you have posted twice about it, so I would say fix it and make it right.

[tmbg]

well, I took the aft bulkhead out (cause I had to trim the stringers a bit to make them fit better in the front, and put it back together. This time I started with the bottom of the bulkhead, where I'd already drilled it to the aft bottom skin, and worked my way up, with the tailspring mount in place. Everything lined up MUCH better this time, and I had a level on it watching for it to twist after every cleco. I got the whole thing in pretty happy with no twist, so I went ahead and drilled it, and everything looks great. The tailspring mount isn't cocked nearly as much as I was imagining it to be, and I think I can probably shim it a little bit to tweak it on final assembly. The plans call out shims as necessary to fill gaps, and there's some slight gap.