[mdredmond]

I'm just getting back to building after a long child-induced break.

I bought my tail and wing kits from a guy here that had started on the tail. I just noticed an issue with the rear horizontal stabilizer spar...

Horizontal stabilizer, rear spar web and doubler. There are two 'lone' rivet holes (in the middle of the spar web) that are located between the HS-911 Inboard Hinge Brackets and the Inboard HS-904 Ribs (one hole each side, L & R). This hole is supposed to be countersunk on the forward side of the doubler for a flush rivet. The guy I bought the kit from countersunk both the front side of the doubler and the rear of the spar - on both L&R sides. One side is already riveted but I can tell the shop head is sitting over (not in) a countersink.

Show stopper?

 

[Greg Arehart]

Matt,

I don't have my plans in front of me, but I would suggest drilling these out if there really is a shop head over top of a countersink to determine the quality of the rivet job and whether it might compromise something. On the trailing edge of the rudder, you will have to dimple both sides and essentially create a shop head that fits into the countersink, so this may be what your previous owner has done (or tried to do). In my opinion (again without looking at exactly where these are located), you could drill an additional hole or two offset somewhat from the holes in question, and add a proper set of rivets.

On the other hand, if the part(s) are easy to replace, then I might consider doing so if that is what it takes to give you peace of mind that it is done right. My larger concern would be that if you find "less than quality" workmanship at this location, you should inspect the rest of the work very carefully. It would give me pause to find an error that appears to have been "covered up" (at least from your description) and not know what other, perhaps more significant errors lurk hidden in the structure.

greg

 

[mdredmond]

Thanks, Greg, for your reply.

I know on some trailing edges we have to do the "acorn in a dimple" but this is a spar - not a bit of control surface skin. Granted, it's one of many rivets in this area and frankly, is probably superfluous. Still, aside from a midair, structural failure is #1 on my nightmare list. I need to know this is really okay - or buy new spars. Spars are cheap: My 2 year old would concur.

As for the rest of the kit - it's all very visible. Nothing had been finally assembled and to be honest, his workmanship is outstanding. He put PERFECT countersinks (rivet heads flush +/- 0.002) where they don't belong!

 

[flion]

I'd call Van's to check before I'd trust a double-flush rivet there. However, this is one of those locations where I'd fill the spar-side countersink with a structural adhesive (I use the Hysol that Lancair sells to assemble their kits; it's blue but I don't have the number with me), flush it to the surface and re-drill and then set the rivet. That will create a 'washer' that will bear against both the countersink and the rivet and should be fine.

 

[mdredmond]

Got word back from Van's. They said it's okay but that I could drill and place another rivet if it made me feel better about it. I'll probably do both - fill with adhesive and put another rivet in there.