It is also interesting to note that even though the Ercoupe wing has less ribs it is also cantiliver "it don't need no stinking struts"
Bill To: [email protected] From: [email protected] Date: Thu, 10 Sep 2009 16:16:54 -0400 Subject: Fwd: {Disarmed} [ercoupe-tech] Metal Wings are stronger..... [1 Attachment] [Attachment(s) from [email protected] included below] 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 -- 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--’ _________________________________________________________________ Windows Live: Keep your friends up to date with what you do online. http://windowslive.com/Campaign/SocialNetworking?ocid=PID23285::T:WLMTAGL:ON:WL:en-US:SI_SB_online:082009
