jamesgrieco(at)yahoo.com
Guest
|
 Posted: Fri Apr 14, 2006 4:35 am Post subject: Cracks in aft fuselage stiffeners: My 2cents |
 |
|
Gary, I would reconsider doing much to stiffen that panel. From
what I have read on GG, the cause(s) are all speculation. The
basic description some gave of the purpose of those stiffeners
as a frame was completely wrong. They are nothing more than
panel breakers designed to stop the walls of the torque box from
buckling.
That area is bounded by the forward and aft vertical fin
attachment bulkheads and the upper web and lower skin. The ratio
of length to width is roughly 2.5:1 which is fairly typical of
beam webs. As our grummans are made as light weight as possible,
the webs probably fail in shear buckling when subjected to
ultimate loading (presumably torsion from the horizontal and
vertical). The simple and most weight efficient fix is to put
'panel breakers' at mid bay to stiffen the webs and prevent
buckling.
| Quote: | From all the pictures that I have seen the cracks occur where
the stiffeners overlap each other. This might have been done to
|
provide some stability to the vertical flange of the stiffeners,
but I suspect it was done simply to allow manufacturing to put
glue on all the surfaces, and it probably aids in fixturing the
stiffeners in place. That the crack would initiate there is not
a real surprise, but they do last many years.
In any event, it does not make those stiffeners act as any real
frame in my opinion, as a frame would require an inner cap. I
would bet that once the crack releases the ends of the two
stiffeners from each other, that is the end of the problem. This
would could be proven if the a/c that have had this problem have
had the condition for a long time (very probable) and they had
no further crack growth. The function of the stiffener as a
panel breaker is not at risk. From my experience on our
Grumman's very big brothers, this is not unusual.
| | - The Matronics TeamGrumman-List Email Forum - | | | Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:
http://www.matronics.com/Navigator?TeamGrumman-List |
|
|
|
Get Email Distribution Too!
FAQ
Search
Memberlist
Usergroups
Register
Profile
Log in to check your private messages
Log in
