Zenith Aircraft and Pull Type Rivets

"J.Kahn" wrote in message news:U5JYh.120163

My beef with the steel mandrel Avex rivets Zenith uses is the fact that
contrary to their claim that the fracture surface of the stem, which has
no zinc plate, won't rust, they do in fact rust as a look at any older
Zenith that's been parked outside will confirm. I would recommend filling
a syringe with epoxy zinc chromate and adding a drop to each mandrel hole
on all the top surface rivets.


I filled mine with structural epoxy before painting, levelled each hole and
it looks like solid rivets. It's not necessary but it looks nicer.

I have been using these rivets, with the modified gun nose, on a
homebuilt project of my own.

Just a simple Harbor Freight Air/Oil Gun, $24.

Rivets are about .04 to .06 cents each.

Very reasonable!

I did quite a bit of research on the process, as well some testing
before making that decision.

Personally, I'm very comfortable with the avex rivet procedure.

Colin
A&P I/A

http://www.jumprunenterprises.com

"Richard Riley" wrote in message
...
On 27 Apr 2007 17:35:33 -0700, stol wrote:

The Zenith line of experimental aircraft are designed around the Avex
pulled rivets. Gigs statement about 4=3=1 is a good way to look at the
fastener concept. So far my Zenith 801 with the V-8 Ford in it has
shown no signs of failing at any joint. Yet. G I can tell ya it has
14,210 pulled rivets in it. :-)

The best money I ever spent was $20 for a Harbor Freight air powered
puller. It's done about 4000 rivets so far and shows no sign of
failing.

Compared to hand pulliing all those rivets, it would still be worth while at
10 times the price!

Peter

The question at hand has been well covered by the answers so far, you may be
interested in the 'reverse' of the pop vs. solid rivet question.
When I built my Zenith, CH200 from plans I decided, or maybe was talked into
doing the skins in solid flush rivets. In consulting with Chris, he said,
'use one dash smaller in solid rivets", therefore my skins are done in -3
and -4 solid rather than -4 and -5 Avex 'Pop' rivets. It doesn't make the
plane any stronger, or weaker, just different.
When I built the prototype CH801 I used all Avex Pop rivets everywhere
except the structure that called for solid rivets. All hand pulled by the
way and I never found hand pulling to be a particular chore. If the whole
plane was ready to rivet at once I can see where the power puller would be a
godsend but who has that many clecos?

Stew



"Andrew" wrote in message
ups.com...
CC: Zenith Aircraft Company

I have an aeronautical engineer friend retired from McDonnell
Douglas who once was in charge of the Harrier project for the U.S.
team. I respect his opinion which is that pull type, "pop" rivets are
only used on aircraft where a bucked rivet could not possibly be used
or on non-critical, low stress applications.

It is my understanding that the bucked rivet, which has been
used over the years in aluminum aircraft, is stronger than the pull-
type pop rivet. In consideration of the Zenith Aircraft 601 and 701,
how is it that they are using a Textron Brand pull-type rivet? Has
there been some breakthrough in material or design in theses Textron
pop rivets making them comparable to the old style "bucked" rivets?


Thanks,
Andrew

Richard Riley wrote:
On Sun, 29 Apr 2007 15:18:20 GMT, "Stew Hicks"
wrote:

The question at hand has been well covered by the answers so far, you may be
interested in the 'reverse' of the pop vs. solid rivet question.
When I built my Zenith, CH200 from plans I decided, or maybe was talked into
doing the skins in solid flush rivets. In consulting with Chris, he said,
'use one dash smaller in solid rivets", therefore my skins are done in -3
and -4 solid rather than -4 and -5 Avex 'Pop' rivets. It doesn't make the
plane any stronger, or weaker, just different.
When I built the prototype CH801 I used all Avex Pop rivets everywhere
except the structure that called for solid rivets. All hand pulled by the
way and I never found hand pulling to be a particular chore. If the whole
plane was ready to rivet at once I can see where the power puller would be a
godsend but who has that many clecos?

There's no such thing as too many clecos. My wife bought me 500 of
each color a few years ago for my birthday.

If she feels the need to make another such gift point her my way.
I'm not proud, I'll accept the gift.

Dan, U.S. Air Force, retired

"Andrew" wrote in message
ups.com...
CC: Zenith Aircraft Company

I have an aeronautical engineer friend retired from McDonnell
Douglas who once was in charge of the Harrier project for the U.S.
team. I respect his opinion which is that pull type, "pop" rivets are
only used on aircraft where a bucked rivet could not possibly be used
or on non-critical, low stress applications.

It is my understanding that the bucked rivet, which has been
used over the years in aluminum aircraft, is stronger than the pull-
type pop rivet. In consideration of the Zenith Aircraft 601 and 701,
how is it that they are using a Textron Brand pull-type rivet? Has
there been some breakthrough in material or design in theses Textron
pop rivets making them comparable to the old style "bucked" rivets?


Thanks,
Andrew


Chris Heintz designed his aircraft to use 6000 series aluminum and Avex pop
rivets. The aluminum he uses is not quite as strong at 2400 series aircraft
aluminum but it is not anywhere near as susceptible to various modes of
corrosion that eat airplanes.

When you design a riveted joint you have to consider both the shear strength
of the rivet and the shear strength of the metal being riveted. Most
airplanes are designed and the rivet number and spacing is determined for
2400 series aluminum with driven rivets. The shear strength of a driven
rivet is slightly greater than that of an Avex pop rivet. The Avex pop
rivet is far stronger than the hardware store aluminum pop rivet. If the
joint is designed for the lower shear strength rivet there will be a few
more rivets but the strength will be as good as you can expect to get with
any riveted joint.

Your engineer friend is correct though with working with existing designs.
If a joint was designed for an aircraft type driven rivet, replacing those
rivets with pop rivets without redesigning the joint to attain the original
strength will probably cause a catastrophic failure.

There is one type of "pop" rivet that develops a shear strength that is
comparable to the driven rivet. This is the "Cherry" rivet, which is a pull
set rivet that does not drop the inside out when it is set and develops the
same shear strength as a driven rivet. These rivets can be used to replace
driven rivets with no problems. However, they are generally used only where
a driven rivet cannot be used. That is because of the cost difference. A
typical driven rivet costs less than a penny. A "Cherry" pull set rivet
costs $.50 to $.60 each. With something like 15000 rivets in a small
airplane, that cost difference adds up. Even the weaker Avex rivets that
Heintz uses cost about a dime each, and you can save a lot of money by
driving rivets where you can do so. I have noticed that most of the
designs that are designed for Avex type rivets use driven rivets in their
factory assembled "quick build" kits. Saves many bucks. Of course, it
does take a little bit of practice to learn how to properly drive and buck
rivets. Nothing you can learn though. :-)

Highflyer
Highflight Aviation Services
Pinckneyville Airport ( PJY )

"Capt. Geoffrey Thorpe" The Sea Hawk at wow way d0t com wrote in message
...
"Andrew" wrote in message
ups.com...
CC: Zenith Aircraft Company

I have an aeronautical engineer friend retired from McDonnell
Douglas who once was in charge of the Harrier project for the U.S.
team. I respect his opinion which is that pull type, "pop" rivets are
only used on aircraft where a bucked rivet could not possibly be used
or on non-critical, low stress applications.

That opinion is not shared by everyone. Now, you can't willy nilly replace
bucked rivets with pop rivets, but there are examples of aircraft designed
for pop rivets. The T-18 is an example. It would be hard to argue that
John Thorpe didn'd know what he was doing, eh?


OOPS. - that's John Thorp without the "e". I guess I "improved" the
spelling....

--
Geoff
The Sea Hawk at Wow Way d0t Com
remove spaces and make the obvious substitutions to reply by mail
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