blind rivets

prkaye · #1 11-15-2006, 07:43 AM

A few questions about blind rivets:

1) I've read that in most places on the RV, one can use Cherrymax blind rivets instead of universal head hard rivets. What is the official "code" for these Cherrymax rivets, and where are they available? Didn't see them on Vans Web Store, and Avery no longer sells hardware (too bad, I really wanted one of their "hole-saver" sets of oops rivets).

2) How do I determine the proper size (length) of blind rivet to use in a given location? Do I use the same gauge as for hard rivets, to check the required length of a blind rivet?

3) How should blind rivets be inspected after setting them? Is there an accepted standard to determine if they have set properly?

Thanks!

Phil

Paul Eastham · #2 11-15-2006, 08:02 AM

Hi Phil,
You will have trouble getting anyone to commit to clear "rules" for substituting any fastener for another, whether it be blind rivets, bolts, camloks, hinges, whatever. The consensus seems to be that each substitution is an engineering decision with inherent tradeoffs. If in doubt, please ask Van's.

Also note that for rib flanges and less-structural things like that, Van's has often specified and told people to use weaker pop rivets like LP4-4 or the monel rivet that I forget the part number for. If you're lucky, Van's will tell you when a cherrymax is overkill.

As for sources, Aircraft Spruce sells them. Van's sells a limited selection as well, search for parts starting with "CCR". They are not cheap from either supplier.

Avery (and spruce?) sell a depth gauge that goes inside the hole, so you can tell what part you need. There's a table in the Spruce catalog that will translate the hole depth ("grip") to the part number, or you can buy a gauge that has the part numbers stamped on it for you. Note that some of the gauges are labelled in 16ths or metric, so be careful with the translations.

As for inspection standards, I would check the CherryMax documentation on the Textron website. They have copious documentation.

Paul

Paul Eastham · #3 11-15-2006, 08:13 AM

You got me curious, here is some more info:
http://www.textronfasteningsystems.c...42-5M-1003.pdf

Page 17 has acceptance criteria

Page 4 for part numbers

keen9a · #4 11-15-2006, 08:25 AM

Quote:

Originally Posted by prkaye

I really wanted one of their "hole-saver" sets of oops rivets

You can get "oops" rivets from lots of sources including Van's. Look for NAS1097AD4 rivets.

Quote:

Originally Posted by prkaye

How should blind rivets be inspected after setting them? Is there an accepted standard to determine if they have set properly?

In most applications of blind rivets, you can't inspect them since there's no access. If the stem breaks, its set.

prkaye · #5 11-15-2006, 08:35 AM

thanks for that info guys.

Quote:

for rib flanges and less-structural things like that

Do you mean where ribs join skins? Or where ribs join the spar? How do I know what's generally "Structural" and what's not?

In one spot I had a lot of trouble with two rivets where the elevator tip rib joins the flange of the elevator spar. These were supposed to be AD4-4 rivets, but I just couldn't get them set straight, and the holes ended up slightly oblong, which made it impossible to get the rivets set nicely. So I put a couple of LP4-3 rivets instead, and emailed vans to ask if that's ok. Waiting to hear back. I could drill a couple more holes between those two rivets and put a couple more rivets in for added strength, but I'll wait and see what Vans says.

skidmk · #6 11-15-2006, 08:40 AM

I have lots of oops rivets... I'll try to remember to bring them Sat.

M

Paul Eastham · #7 11-15-2006, 08:47 AM

Quote:

Originally Posted by prkaye

thanks for that info guys.

Do you mean where ribs join skins? Or where ribs join the spar? How do I know what's generally "Structural" and what's not?

rib-to-spar flanges is where Van's has had me use non-cherrymax when I've gotten into trouble with bad solid rivets and such. You don't have any way of knowing for sure what's structural besides asking the engineers, though you may develop an intuition over time and after asking lots of questions about specific cases.

briand · #8 11-15-2006, 09:35 AM

Don't Cherrymax require special (expensive) Cherrymax pullers?

prkaye · #9 11-15-2006, 10:03 AM

Vans confirmed that it was OK for me to put those LP4-3 blind rivets for elevator spar to tip rib. (they did hint that in the future I should probably ask before I go ahead and make a substitution like that... again my impatience got the better of me).

The design of these aircraft must be incredibly robust to be so forgiving of substitutions like this!