Pietenpol-List: cabane struts and braces

matronics · Post by **matronics** » Mon Mar 27, 2006 7:55 am

Original Posted By: "Rick Holland"
Howdy, low 'n' slow fliers;Thought I'd pitch in my two cents on the matter of the cabane struts and their braces. NX41CC has the brace tubing forward to the motor mount attach points (no X-brace wiring between cabanes), parallel cabanes, slightly canted (aft) wing. I believe one of the advantages to having the cabanes parallel to each other is the ability to cant them forward or aft to tweak the CG relative to the wing chord (or center of lift, if you will), despite the cautions from everyone that you should NOT rely on this to correct lousy construction or CG calculation.You should try to get the geometry as close as possible by building your engine mount to balance the CG, or maybe move things that can be moved, but as a last resort the cabanes can be angled to tweak the wing and improve CG location if the tail is heavy. 41CC has its cabanes that way and I would encourage you to study the possibility of mounting your cabanes in a parallelogram, rather than a trapezoid, fashion for this advantage. For more on this subject, Doc Mosher posted an excellent and clear email that is in the archives and is worth reading if you're working on your CG or cabanes.As far as strength, 41CC went over on its nose and flipped onto its back in the landing gear collapse. The forward cabanes failed in compression buckling, and the forward cabane brace tubes were damaged as a result. You can make the cabanes stiffer to form a "roll cage", but I believe they are plenty strong as they are and they did their job in this case. Certainly the rear cabanes held up until the tip of the vertical stabilizer hit the ground and the dust stopped. You can see photos of the cabane damage at http://www.flysquirrel.net/piets/incident/incident.html .Oscar ZunigaSan Antonio, TXmailto: taildrags(at)hotmail.comwebsite at http://www.flysquirrel.net________________________________________________________________________________Date: Mon, 27 Mar 2006 07:08:58 -0700

matronics · Post by **matronics** » Tue Mar 28, 2006 8:11 am

Original Posted By: Greg Bacon
Rick asks->What size were these cabane brace tubes?I'll have to check next time I'm out at the hangar. From the pictures, they are at least 1/2" OD and probably more than that. I checked my plans and manual and all they say is that a brace tube is used to replace the x-brace wiring. The plans just say "strut to wing".Oscar ZunigaSan Antonio, TXmailto: taildrags(at)hotmail.comwebsite at http://www.flysquirrel.net________________________________________________________________________________Date: Tue, 28 Mar 2006 09:02:56 -0600

matronics · Post by **matronics** » Tue Mar 28, 2006 9:20 am

Original Posted By: Greg Bacon
My address book shows him at lnawms(at)msn.com Carl Vought ----- Original Message -----

matronics · Post by **matronics** » Tue Mar 28, 2006 10:56 am

Original Posted By: Michael D Cuy

Brodhead Pietenpol Association