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prkaye

Well Known Member
Note to moderator - please leave this in the general discussion section, as the area I'm inquiring about is identical on the RV7/7A and the RV-9/9A.

In preparing my center fuse I didn't double-check the plans carefully enough, and forgot where it said not to dimple the 4 locations at the interesection of the 904A bulkhead and the stiffeners.
What I did was to countersink *all* the holes along the lower flanges of the 904A and 904B bulkheads, where the 976 bottom skin will be rivited (and I dimpled all the corresponding holes in the 976). The note about not dimpling those 4 locations mentioned above leads me to wonder whether the intent was that I should have *dimpled* all the other holes in the lower flanges of the 904A and 904B, rather than countersink as i did (the thickness of the material suggested to me that I countersink all thes holes, but the note about those 4 locations confuses me).
One concern I have is those double-flush rivets in the outboard 5 rivets on each side of the 927-904A joint. Because I have already countersunk these holes in the 904A from the bottom, when I countersink the other side for the double-flush rivet, this will leave minimal material in the 904A around those holes and enlarge the holes somewhat.
Do I have a problem, and if so, what should I do to correct it?
 
No input from anyone on this??
I talked to Bruce at Vans about this... in case anyone else is interested or has a similar problem, here's the verdict -
it's OK to countersink the flange, although they prefer dimpling because it's stronger.
As for those double-flush rivets, apparently it's OK not to do them double-flush, you just have to drill clearance holes in the landing gear weldment to go over the shop heads of the rivets.
Alternatively, I'm wondering about doing those double-flush rivets using NAS 1097 rivets there, with the shop head point down (on the lower outside skin). That way I only have to countersink the upper side of the bulkhead flange a tiny bit and it won't enlarge the hole much (recall I already countersunk the lower side of the flange in those spots, by mistake).
 
Phil, for those outer 5 rivets on each side you countersink the forward bottom skin from the bottom up and that gets the manufactured head. The forward bottom skin is thick enough to countersink by itself. The bottom center section skin is not countersunk or dimpled at those 10 rivets and remains a #40 hole. The outer five holes in the spar flange get countersunk from the top side thereby creating the double flush. Hope this helps. Having re read the thread I just realized you already countersunk the outer 5 rivet holes from the bottom. I still think you will be ok. I just installed my weldments and also looking at others I think there will be enough clearance for the shop head between the flange and weldment even without the double flush.
 
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No need for double flush

I had enough clearance between the gear mounts and the rivet shop heads to allow for a standard set rivet. Another local builder had very minor bit of interference there. He said 2 rivets scratched the powder coating on the gear mount. A bit of work with the Dremel tool added clearance.

working the -9A cowl,
Steve
 
OK good to know... thanks guys. Bruce also advised me not to use the NAS1097s here (this area needs the full strength of a full-size rivet head), so I'll go ahead and do it non double flush, and later take steps to obtain the required clearance as required.
 
change needed

this is something vans should omit from the plans. there is plenty of room in there. no need to double flush the rivets....

for what its worth i countersunk through the skin into the flange of the spar and dimpled the front lower skin. someone mentioned this was what orndorf did..i dont know about that. mine was and over sight :eek:
 
Cool... that's good to know about the non-issue with clearance. I just got my tungsten bucking-bar from Webster, and really looking forward to trying it out... that little thing is HEAVY!!!
 
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