Mating spars

[Bryan Cotton]

I clamped my spars to the front fuselage attach angle before I drilled. No slack.

I piloted a 1/4" hole in my rear angles then finished up the drilling on a press. I had riveted the pieces together with flush aluminum Avex rivets I had, then drilled them out after. Came out great.

[Rynoth]

Just to be clear Kevin, I'm not saying that this has actually been a problem for anyone, just that the steps in the plans mean everything is set (angle of incidence, etc) prior to updrilling, while pre-mating the spars reverses those steps. In all likelihood it's not an issue, and based on the posts in this forum at least it seems that a lot of builders may have saved themselves some grief by pre-mating.

[Area 51%]

If you have your drill bushings (and alignment pins) in place while setting the incidence, you won't have any mismatch. There isn't a lot of room inside the spar tunnel for things to move around. That's how I knew something was up when I tried to fit the aft tunnel.

I guess I missed the part about everything going smoothly until I removed the wings after drilling the rear spar attachment and forward holes to deburr everything up to that point. It was during the re-insertion of the wings for the aft angle drilling that I noticed the spars having a small gap between them. I reality, I believe if the aft tunnel had been in place before inserting the wings, there wouldn't have been enough room for the two pieces to overlap and the spar would have just slid by the bolt. (Actually, I think it was caught on the edge of the washer)

None of this was meant to worry you. Just a heads-up, if down the road your spars have an unexplained gap between them. You can't actually see this happening without a mirror.

[sonex892.]

Just some food for thought (and to muddy the waters a bit I suppose), but the way the plans call for wing rigging (i.e. not pre-updrilling the spars) has you rig the rear spars to the fuselage prior to updrilling the main spar holes..

Kevin to put your mind at ease, I believe the B model plans instructions now call to updrill the clamped spars to 1/2", aligned using the 3 alignment holes prior to wing assembly. With the exception of fancy milled mount blocks, 1/2" instead of 3/8" holes and wing rigging alignment blocks, the A model wing mounting is effectively the same as the B.

As for the gap, when pinned with the 3 alignment holes, (not the wing mount holes). If you are building from a kit, the gap is what it is.
Steve
Sonex 892

[dbdevkc]

I clamped my spars to the front fuselage attach angle before I drilled. No slack.

I piloted a 1/4" hole in my rear angles then finished up the drilling on a press. I had riveted the pieces together with flush aluminum Avex rivets I had, then drilled them out after. Came out great.

I am trying to wrap my head around how that departs from the plans other than the initial up drilling of the mated spars to .3725, and using a drill bushing when rigging the wings. I assume you first did the steps below.

1) Mated the spars, drilled the three alignment holes to 1/4" using something to keep brill perpendicular to spar web (egg cup bushing holder or something else (and then bolted the spars together I assume)
2) Up drilled the wing mount blocks through the mated spars, then reamed to .3725 for nice snug fit to you an6 wing bolts (all un the drill press)
3) Finished wings
4) Rigging wings to fuselage, attached the rear spar to rear spar carry through

5) Using the .3725 to 1/4" drill bushing, drilled through RH forward attach angle, then did you up drill the forward attach angle to .3725?

[Area 51%]

Can't speak for Bryan, but that's what I did. Then pushed the drill bushings in from the front to drill the 1/4 hole in the rear attach angle.

I up-drilled the 1/4in hole in the front attach angle with the wings removed and using an alignment block. Very similar to what Bryan used. I can send you a picture.

[Rynoth]

Kevin, regarding the gap between the bottom of the spars, yours seems typical. I don't have a close-up pic like yours but here's what mine looked like.

[dbdevkc]

Can't speak for Bryan, but that's what I did. Then pushed the drill bushings in from the front to drill the 1/4 hole in the rear attach angle.

I up-drilled the 1/4in hole in the front attach angle with the wings removed and using an alignment block. Very similar to what Bryan used. I can send you a picture.

So, drill the 1/4" in the front attach angle, then up drill the front attach angle, then drill the 1/4" in the rear attach angle. But up drilling of the angles from 1/4" to 3/8" was not done through the spar attach blocks, but instead with wings removed?

[Bryan Cotton]

Kevin,
That is right. Drill the 1/4" pilot holes in the fuselage, remove wings, updrill fuselage. When I'm home again I'll forward you an email of the process. If anybody has my 90% done, 90% to go email please forward it to Kevin. My phone deletes the pictures when I forward and I can't figure out how to stop that.

[Area 51%]

Don't just free-hand the up-drilling. I'm sure you'll find Bryan made "up-drilling blocks" that basically take the place of the spar blocks so there is no danger of enlarging the already reamed spar holes. I made my own version, but they do the same job.

PM me your email and I'll send you pictures of our process as well if you wish.