Oversize wing spar rivet holes

Thermos · #1 09-18-2005, 06:51 PM

Hello all,

While countersinking my wing spar reinforcement plates (the "waffle" plates) for platenut rivets, I found that the prepunched #40 holes for these rivets were actually almost #30. I did a little more checking, and the #30 rivet holes for the rib rivets are almost 5/32". That makes for a lot of oversize rivet holes in this part.

I still consider myself a 'newbie' builder, and perhaps these holes are really ok. But everything I learned building the tail kit tells me that these holes are a problem - oversize holes lead to weak riveted joints.

Has anyone else noted this on their wing spars?

Thanks,

Dave

Jamie · #2 09-19-2005, 05:13 AM

I'm not sure what the rivets on the 'wing spar reinforcement plates' are you mention...(maybe my memory is already getting hazy w/ regard to the wings

), but the rib rivets should definately be AN470AD4 rivets. My pilot holes were fine. I would just give Van's a hollar.

Just curious. Are you SURE the pilot holes are 5/32? If so, you should be able to put a #8 scew through the holes. If you can put an AD4 rivet in those holes without enlarging them there is definately something fishy.

Thermos · #3 09-19-2005, 02:03 PM

Thanks, Jamie.

Here's an example of the rivet holes in question. This is a #30 rivet in one of the wing spar reinforcement plate holes, not quite 5/32" but close.

The odd part is that the the holes appear to be "coned", for lack of a better word - the diameter is smaller on the opposite side of the plate. And if this really is wrong, then my rear spar reinforcement plates are messed up too. The holes on one side are too big for a #30, and too small (or perhaps just right) on the other.

Spoke with Ken Scott at Van's late last week, he'd never heard of anything like it. Emailed some pics also, no response yet.

Anyone else receive a wing kit in mid-August? If so, I'd be interested to know if your spars look the same.

Dave

TShort · #4 09-19-2005, 02:50 PM

I'm not 100% clear on what you mean by "wing spar reinforcement plate holes" - could you post another pic to clarify?

Thomas
-8 wings

Thermos · #5 09-19-2005, 03:30 PM

The wing spar reinforcement plates are those plates with rectangular cutouts that Van's rivets to the aft side of the main spar web.

Dave

Bob Collins · #6 09-19-2005, 04:11 PM

I'm confused too. As I recall, the ribs don't rivet to the doubler plates. But it's been over a year.

CFI1513840 · #7 09-20-2005, 05:21 PM

Dave,

After reading this thread, I checked my spars, which were shipped in July. I have the exact same problem on my right spar, although the left one looks ok, I'll be interested in knowing what Van's has to say. I think I'll drop them a line. Thanks for the heads-up.

Ken Howell
Glenwood Maryland
RV-7 Wings

CFI1513840 · #8 09-20-2005, 05:54 PM

Dave,

I did a little further checking on my right spar. The holes are cone-shaped like you mentioned. I found that a #26 drill will just fit into the large end of the hole. Thats .147 compared to .128 for a #30, so the hole is about 19 thousandths oversized on the large end. I would expect that if you made the shop end of the rivet on the largest side, it would fill in ok, as it only needs a few thousandths and only on the large end. The other option would be to go with 5/32 rivets. It will be interesting to see what Vans says. I wonder if this was a tooling problem? Possibly a dull bit in the punch press?

Ken

Mark Burns · #9 09-20-2005, 07:54 PM

Quote:

Originally Posted by CFI1513840

Dave,

After reading this thread, I checked my spars, which were shipped in July. I have the exact same problem on my right spar, although the left one looks ok, I'll be interested in knowing what Van's has to say. I think I'll drop them a line. Thanks for the heads-up.

Ken Howell
Glenwood Maryland
RV-7 Wings

Ken and Dave,
I've checked my right spar and I have the same thing, although not as bad.
I've got the main ribs already riveted on but the nose rib rivet holes are cone shaped as mentioned earlier. I think this is just the nature of punching holes.
A dull punch would make worse I'm sure.

My nose rib holes are .138 on the large end, and .126 on the small end.

Military Specifications MIL-R-47196A say that the max hole diameter for a 1/8" rivet is .135 (The range is .125-.135)
If you average the small end and the large end I'm still ok I suppose.
The taper doesn't seem to be linear either. It's more of a bell shape than a cone.

http://home.flash.net/~gila/rivet_spec/rivet_a.htm

My right spar is S/N 71768R
We should start looking at these S/N's to see if there is a pattern of the punch getting dull.

My left spar has all of the holes in question filled with rivets already, and I didn't notice anything unusual.

All these rivets do is hold the ribs onto the spar anyway

I'm not going to loose any sleep over this one.

Mark

Thermos · #10 09-20-2005, 08:09 PM

Ken and Mark (and anyone else!),

I exchanged emails with Scott Risan at Van's on this topic, and also talked with him today on the phone.

According to Scott, the "coned" holes are a byproduct of the die used to punch these holes in the spar reinforcement plate (and other parts too), as the die for a #30 hole is 0.018" to 0.028" oversize to accomodate the punch. So, the hole enlarges as the punch presses through the material.

He also discussed this with Ken Krueger and the engineering staff. They indicated that holes 0.015" to 0.020" oversize would be ok, since a driven rivet would still expand to fill the hole.

By the way, I was really impressed with the response I got from Scott and the Van's folks. I tend to get wrapped up in obsessive little details like this, but Scott pulled other parts, measured them, talked to the folks who run the punches, and consulted Engineering just to answer my questions. There aren't too many other companies where you get customer service like that from the general manager.

Anyway, that's what I found out and for now, I'm pressing on with my spars as they are. Ken, if you do contact Van's could you share what you learn?

Dave