Earlier, Andrew wrote:

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?

This question comes up regularly. I'm starting to think we need an FAQ
page on it somewhere.

The short answer is, it depends.

The slightly longer answer is that not all pop rivets are created
equal.

For example, the Emhart MK- and MP-series Monel pop rivets and their
Cherry commercial MSC and MSP equivalents have shear strength values
on a par with equivalently sized MS20470AD and MS20426AD solid rivets.
They're also about a hundred times more expensive than the solid
rivets, but still only about 1/5 the price of CherryMax and CherryLock
aerospace rivets.

The aside to the slightly longer answer is that Chris Heintz was wrong
when he referred to Monel as a type of stainless steel. There is no
iron at all to it; Monel is an alloy of nickel and copper. It is more
galvanically neutral than stainless steel. Monel pop rivets have a
long and well-proven service history in several aircraft designs, of
which I'm most familiar with Dick Schreder's HP/RS series kit
sailplanes.

The somewhat longer answer is that, aside aside, Chris Heintz is a
smart guy and a capable designer and engineer, and that the Zenith
aircraft are specifically designed around the strength values
available from the specified rivets. They are also generally designed
around the lower strength values of 6061-T6 aluminum sheet instead of
the more expensive 2024-T3 aluminum more common in production
airplanes. There are some compromises required, but in general the
result is better economy in a perfectly servicable airplane.

I'm an amateur, don't try this at work.

Thanks, and best regards to all

Bob K.
http://www.hpaircraft.com/hp-24