Rebel/Super Rebel/Moose: Proseal between main & rear spar doublers?
Posted: Sun Feb 19, 2012 4:51 pm
The manual calls for proseal between several main spar sections as well as
between the rear spar and one of the rear spar doublers.
First allow me to digress a bit. I know, as I'm sure you do as well, that
there are terrible, so-so, good and even a few excellent A&P's out there.
I'm sure you know a few that you wouldn't trust putting a new windshield
wiper on your car let alone a part on your plane. Likewise there are those
few whose work is simply outstanding and whose advice is to be listened to.
We have a couple in the latter category at our airport. In fact there are
at least 3 that have built at least several experimental planes each as well
as worked on countless certified planes.
We were scratching our heads about using proseal between doublers on the
main and rear spar. We asked the opinion of one of our friends who is an
outstanding A&P. His comment/advice is to NOT put proseal between doublers
in these locations. Why? Because the doublers are designed to be as close
to each other as possible-in fact they are engineered with the idea that by
being sandwiched TOGETHER they are able to then effectively dissipate stress
across each other (or across multiple layers as in several instances on the
main spar). He commented that if they are apart any more than even a bit of
primer they lose some of this stress transfer ability. Furthermore, he
commented that by being even slightly apart (due to even a slight bit of
proseal) they would then be free to move against each other and act in a
shear fashion against the rivets holding them (close) together.
Anyone have any engineering experience with this? I emailed the above to
Jeff McMurrer at the factory to get his (and perhaps Darryl's) input.
Thank you,
Ted Waltman
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between the rear spar and one of the rear spar doublers.
First allow me to digress a bit. I know, as I'm sure you do as well, that
there are terrible, so-so, good and even a few excellent A&P's out there.
I'm sure you know a few that you wouldn't trust putting a new windshield
wiper on your car let alone a part on your plane. Likewise there are those
few whose work is simply outstanding and whose advice is to be listened to.
We have a couple in the latter category at our airport. In fact there are
at least 3 that have built at least several experimental planes each as well
as worked on countless certified planes.
We were scratching our heads about using proseal between doublers on the
main and rear spar. We asked the opinion of one of our friends who is an
outstanding A&P. His comment/advice is to NOT put proseal between doublers
in these locations. Why? Because the doublers are designed to be as close
to each other as possible-in fact they are engineered with the idea that by
being sandwiched TOGETHER they are able to then effectively dissipate stress
across each other (or across multiple layers as in several instances on the
main spar). He commented that if they are apart any more than even a bit of
primer they lose some of this stress transfer ability. Furthermore, he
commented that by being even slightly apart (due to even a slight bit of
proseal) they would then be free to move against each other and act in a
shear fashion against the rivets holding them (close) together.
Anyone have any engineering experience with this? I emailed the above to
Jeff McMurrer at the factory to get his (and perhaps Darryl's) input.
Thank you,
Ted Waltman
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