Sorry Ercouper's, I hit reply instead of reply all.
Lynn
____________________________________
From: IFLYSMODEL
To: [email protected]
Sent: 9/10/2009 4:09:12 P.M. Eastern Daylight Time
Subj: Re: {Disarmed} [ercoupe-tech] Metal Wings are stronger.....
No, Dave: I have worked on several Ercoupe and Aircoupe wings and they all
follow the same design whether they have been converted to aluminum cover
or have the fabric. The only significant difference I have seen is that the
Aircoupe wings, which were metal covered to start with, have ribs that do
not have the edges turned down. I suspect this is because the metal covering
does not need the protection from the possible rubbing of the fabric and
rib faying surface. I would also think that the ribs with the edges turned
down are stronger than those that do not have that feature. Oh yes, the 1450
pound airplanes have a slightly different attach fitting where it attaches
to the center section. I suspect this was changed on purpose also.
I am attempting to enclose a picture of a complete wing with the nose
rib metal covering removed. I am not sure this will work as I seem to
remember that you have to do something different to attach a picture when
using
the yahoo site. You can see from the picture that the Ercoupe wing has many
fewer ribs than those of other type aircraft. The Ercoupe wing ribs are
attached at an angle which makes the structure much stronger. Also, when the
fabric is put on the Ercoupe wing, it is attached with several (five I
believe) screws to each rib with a strip on the top to ensure strength and
rigidity. This attachment is different on the other fabric wings, where the
fabric must be rib stitched to each rib.
Lynn Nelsen
In a message dated 9/10/2009 3:28:01 P.M. Eastern Daylight Time,
[email protected] writes:
As I understand the conversion, Ercoupe wings that are metalized are
actually converted to a "semi-monocoque" structure, same as the old T-28.
Ribs
are actually removed in favor of the structural strength contributed by the
aluminum skin.
Anybody out there to confirm this?
Dave W
=========]-(§)-[==========
// \\
From: [email protected] [mailto:[email protected]]
On Behalf Of William R. Bayne
Sent: Thursday, 10 September, 2009 13:54 PM
To: Ercoupe Tech List
Subject: Re: {Disarmed} [ercoupe-tech] Metal Wings are stronger.....
I would suggest that any engineering evaluation use the correct approach
in evaluating "stronger".
Adding thin sheets to a wing structure already designed and capable of
coping with the normal stresses of flight (plus a considerable safety
factor)would add little, if any, to the overall load carrying capacity of an
Ercoupe wing in terms of the additional stress said could carry before it
failed
under load. The materials and procedures utilized by the various STCs
presently installed or available does not transform the Ercoupe wing designed
for grade A cotton covering into a monocoque structure as would seem to have
been inferred.
"Monocoque" construction is defined as "an aircraft structure in which the
outer covering skin carries all or a major portion of the stresses".
The internal structural components, metal skin thickness, rivet type,
size, and spacing of a stressed skin wing design would be quite different, and
likely lighter.
Consider also these questions:
1. What practical purpose is served by increasing wing strength beyond
regulatory design requirements?
2. How much has the load capability of Ercoupe wing design increased when
covered with modern synthetic fabrics of higher tensional strength abd
durability than the original grade A cotton?
Regards,
WRB
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On Sep 10, 2009, at 13:05, Art Langston wrote:
Chris, could you please share the engineering data with us and cite the
documentation where we can read it?
When finished, I believe the Polyfiber may actually be stronger than the
aluminum. I've de-skinned Ercoupe wings, and the metal is very thin.
Polyfiber is tough.
Thanks
Art N2666H
Chris wrote:A metal wing is stronger than a fabric one. The metal
distributes the loads over the surface. Would anyone want to consider a
fabric
covered fuselage?
Chris
Santa Cruz
99674
‘--o-O-o--’
