Phil

Phil

Well Known Member
I asked this question to Vans and they didn't have any objections to it, but I thought I'd draw on everyone elses experience too.

It's a long story, but I messed up the holes on the middle nose rib and the skin. The plans call for dimpling 3/32" and installed and AD3 flush rivet, but these holes are too large for AD3's now.

I'm considering drilling out to 1/8", dimpling, and installing AD4's instead.

There are a total of 12 holes on the middle nose rib. (6 on each side)

Thoughts?

Thanks,
Phil
 
The only "restriction" I've ever read about using a larger diameter rivet, is the spacing requirements. There is a minimum distance between rivets that is recommended for maximum strength.
 
Watch the Pitch

doctornigel said:
There is a minimum distance between rivets that is recommended for maximum strength.
Click to expand...

Quite right; the center-to-center distance is called "pitch". In my day job, we use 4 X rivet diameter as a minimum. In a case of different-sized rivets, the larger rivet diameter is the factor used. An AD4 being 1/8" diameter, the minimum pitch then becomes a half inch. I've never seen an RV-10, so I don't know what your rivet spacing is, but I'd bet you can put the AD4 in there without any issues.
 
Minimum spacing varies...

Red Voodoo said:
Quite right; the center-to-center distance is called "pitch". In my day job, we use 4 X rivet diameter as a minimum. In a case of different-sized rivets, the larger rivet diameter is the factor used. An AD4 being 1/8" diameter, the minimum pitch then becomes a half inch. I've never seen an RV-10, so I don't know what your rivet spacing is, but I'd bet you can put the AD4 in there without any issues.
Click to expand...

For 1/8 diameter rivets, The 4x min. spacing number is only for universal head rivets according to the Mil Specs.

Countersunk rivets in a dimpled sheet have a min. spacing of 5x at 1/8 diameter. Machine countersunk rivets have an in-between spacing.

As the rivet diameter gets larger, the spacing multiplier actually decreases...

Sometimes rules of thumb should be cross referenced to the specifications...:)

....available here on my web site.... See Table VII.

http://home.earthlink.net/~gilalex/rivet_spec/rivet_a.htm#TABLE VII

gil in Tucson
 
Great link, Gil!

Before I left the house this morning, I measured the pitch of the rivets. They're roughly 1.25" on center or approximately 10X spacing for 1/8". So we're good on spacing.

I did check the edge clearances too. The edge clearance is fine.

The only hole(s) in question are the holes on the very tip of the nose rib.

Because you have to grind the nose rib down a bit to conform to the shape of the skin, those two holes are very close to the minimum edge clearance (tip-to-hole). For these two holes, I don't think it will be that big of a deal if they're just a hair below the minimum. But I am going to measure them again for peace of mind. I believe I need just over 1/4" clearance.

Phil
 
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az_gila said:
For 1/8 diameter rivets, The 4x min. spacing number is only for universal head rivets according to the Mil Specs.

Countersunk rivets in a dimpled sheet have a min. spacing of 5x at 1/8 diameter. Machine countersunk rivets have an in-between spacing.

As the rivet diameter gets larger, the spacing multiplier actually decreases...

Sometimes rules of thumb should be cross referenced to the specifications...:)

....available here on my web site.... See Table VII.

http://home.earthlink.net/~gilalex/rivet_spec/rivet_a.htm#TABLE VII

gil in Tucson
Click to expand...

Unless company policy dictates otherwise. I'm sure you are correct for aircraft in general; I'm just used to a particular design manual, which my company inherited from Grumman, carved into a couple stone tablets. As hard as some of the heads of the old-timers who mentored me.:)
 
Gil,

I read the document a bit more and I came across this in section 3.4.3.

3.4.3 Repair limitations. The combined oversize rivet hole repairs and oversize countersink repairs shall be limited to a maximum of 20 percent of the rivets, or 10 rivets in a single rivet pattern, whichever is less. Repairs to more than two adjacent oversize rivets, or replacing more than half the rivets with oversize rivets in any 10 inch length of pattern is prohibited.
Click to expand...

I would be replacing 100% of the rivets in the middle nose rib, but probably 2-3% of the rivets in the completed VS. How would you suggest reading that section?
 
I just checked the edge spacing on the two forward holes. They are 3/16" edge-to-center. That is 1/16th" short.

However, I don't think these two holes would be subjected to too much force. I would think the bend of the VS skin would take on the majority of the forces?

Phil
 
I went ahead and assembled the VS last night. Drove rivets, made mistakes, and learned the entire way through.

At the end of the day, I had a fully assembled VS. It may not have been perfect, but it was functional.

As I went through the process, my ability to drive rivets got much better. By the end, I was lining them up and knocking them down like a pro. It's too bad I've got all of those irreversable mistakes up front.

I hate to say it, but I just ordered a completly new VS from Vans. The old one served it's purpose as a training piece. It's too bad that it took me destroying a VS for training purposes. But I clearly wasn't ready to build when I started.

I'm $300 lighter in the wallet now and I've aquired the skills to do it right.
 
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Aah, the nose ribs - hours of endless fun for the beginner!

VANS seem to have some obsession with NOT using blind rivets unless absolutely necessary. Given the choice, I would use MK319 rivets on the nose ribs. (Bit late now, of course, for you). However, in UK we are strictly controlled - EXACTLY as per the plan unless you get modification/concession approval. With the US Experimental category, I believe you can make minor re-designs provided you comply with the FAA regs -seems like a great area for some "discretion". After all, you get the option in the plans with those difficult-to-buck elevator rivets - joy!

I stuffed the nose ribs on one HS skin - imagine the expense of crating and shipping a new one from US - add tax as well and it more than doubled the price! :eek:

If you decide to go ahead, make sure you properly beburr the enlarged holes and check for any cracks where they were damaged. It's very easy after making a mistake to rush into redo-ing the rivet without all the normal care and attention - (ask me how I know.....). Also, if it's not too bad, consider using a longer 3/32 rivet ( -4 or -4.5) and gently pre-squeeze it to fill the hole so you can then buck it without clinching. Bit like a home-made "oops" rivet.

Don't get down-hearted about it either. Apart from the HS skin, I did the VS spar 3x before I got it right! It gets easier - just done the elevator and it went together like a dream. :D
 
I've had good days and bad days. I've really enjoyed he process, but I will get cross-eyed PO'd sometimes too.

I've got a couple of parts that I've screwed up twice and I will be doing them for the 3rd time. If I screw up once, then it's inexperience. If I screw up twice, then the second time is completely my fault. Those are the ones that hurt the most....

Now I'm just waiting on the replacement parts to show up from Vans. I've learned not to get in a hurry waiting on Vans. It usually take 2-3 weeks. That hurts even more than the mistake.

Phil
 
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MK319BS rivet use

paul330 said:
Aah, the nose ribs - hours of endless fun for the beginner!

VANS seem to have some obsession with NOT using blind rivets unless absolutely necessary. Given the choice, I would use MK319 rivets on the nose ribs. (Bit late now, of course, for you). However, in UK we are strictly controlled - EXACTLY as per the plan unless you get modification/concession approval.
.............
Click to expand...

Paul... is this true on the new plans from Vans?

My old RV-6 instructions actually allow the entire lower wing skins to be attached (as an optional method) with the MK319BS rivets.
It is also mentioned in several other areas of the instructions as an option for hard to rivet areas.

Is this an actual change, or an interpretation of a perceived obsession?

gil in Tucson
 
Don't know - haven't got the wings yet. I think one of the flap skins is MK319s. On the empennage, there is the odd rivet which is impossible to buck which is designated blind. Other than that, the only option is the second row on the elevator rear spar (top or bottom depending on hand). I chose that because I HATE bucking difficult rivets! I understand the cost/strength/weight implications but to me, it makes no sense not to use the blind rivets in those sort of areas. I would have used them on the nose ribs if I were permitted by our regs.

I understand the lower wing skin is a bit of a pig so I will certainly spend the $$$ on a few hundred MK319s if I get the option!
 
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