SNX-W12 (Counterbalance hole in rear spar)

[NWade]

All -

"Completed" my right wing last night by finishing up the aileron; but when I attempted to mount it on the wing I got a nasty surprise: The hole in the rear spar is too small to fit the counterbalance assembly! Specifically, I found that the AN3-14 bolts that the plans specify are longer (1 & 7/8") than the width of the hole (1 & 5/8"). I thought I recalled a tech note or plans-revision stating its OK to make the hole a little bigger - but now I can't find it.

Has anyone else run into this problem, or do you recall where Sonex said this hole was OK to enlarge? ...Since the rest of the wing is complete & riveted, I don't want to just hack open the hole and risk ruining the rear spar until I know its OK to do so. :roll:

Thanks,

--Noel
Sonex #1339

[gammaxy]

I had the same problem and carefully used a dremel cut-off wheel to make the hole large enough for the bolts. I'm not aware of any tech note or revision.

[Rynoth]

I used a half-round file to make 2 small half-moons to clear the bolts. Here are some pics, with a link to my full blog post below.





http://www.rynoth.com/wordpress/waiex/2 ... aerobatic/

[peter anson]

Just to put your mind to rest, I don't know of anyone who has not had to open up the holes a bit. I think I may have shortened the bolts slightly as well as enlarging the hole, but in the end the weight has to go through that hole. Sonex seem most reluctant to revise drawings. If you contact Kerry he will probably just tell you to file the holes out, but his email will have the following:
"Sonex Aircraft, LLC Technical Support Disclaimer: Any tech support provided in this e-mail is supplied for your consideration/evaluation only. Only airframes built strictly to the plans have been thoroughly engineered and tested by Sonex Aircraft LLC. Any deviations from the Sonex, Waiex, or Xenos plans are accomplished at the builder's own risk."

Peter
Sonex 894

[SonexN76ET]

The important thing with the counterbalance hole is to make sure there is no interference with the movement of the aileron. You also need to make sure your ailerons are balanced to prevent flutter as per the plans. If you paint your ailerons you will need to remove them and balance them again after the paint is dry. I had to put file clearance notches similar to the pictures shown you by Ryan to get my ailerons on and off. Take pictures of your ailerons when balanced to show your DAR or FAA FSDO inspector.

Jake

[DCASonex]

Do not have my plane handy to confirm and it was a couple of years ago, but think I converted to flat head bolts for a bit more clearance to ribs as well.

David A.

[fjdoug]

yes me too;
on one wing only (can't remember which), I used countersunk MS screws because the bolt heads brushed the flange on the rib as they moved.
Doug.

[fjdoug]

and hello AP BTW!

[NWade]

Thanks, all! I suspected it was pretty common; as the drawings seem to scale up to my assembly with no obvious signs of a mis-measurement or improper dimension (for once). ;)

--Noel
Sonex #1339
Center-stick, TD, Turbo
https://picasaweb.google.com/103964152364205921975/SonexBuild

[rizzz]

If you paint your ailerons you will need to remove them and balance them again after the paint is dry.

Not sure if it is required to be that accurate on a Sonex, but it doesn’t hurt off course.
A number of years ago when Sonex first came out with the acro aileron option someone questioned (I believe during a webinar) if the counterweights shouldn’t be made heavier to compensate for the longer/heavier ailerons.
The response that came back from Sonex was that the flutter speed was still well past VNE.
There was a discussion on this topic on the yahoo groups as well which I’m trying to find, I’ll post a link if I do.

edit: could not find the discussion but there is a revision on the Sonex website from 1.6.09 that instructs to delete the counterbalance procedure from drawing SNX-W25 for the acro ailerons: http://www.sonexaircraft.com/support/sonex_revs.html (at the bottom of the page).