Brodhead Pietenpol Association

Original Posted By: Ray Krause
I've just ordered some strut material from Carlson and I've been surfing the archiveson how the fittings are being made. It appears most folks are using 7075aluminum inserts for the strut ends. I'm wondering why 7075. I understandthe strength is better but really the struts are 6061 so if the fittings aretwice as strong by using 7075, doesn't that just move the failure point to thestrut rather than the fitting? Plus the strut material material area that isin contact with the bolts is much smaller than the area of the insert itself.Is my logic flawed here?I thought I read that the corrosion resistance is better in 6061 but I might bemistaken as I've read a lot on the different alloys today and might have it confusedwith another.Thanks, Tom BrantSent from my iPad________________________________________________________________________________

Original Posted By: Gmail
The wing spar of an aircraft is generally the heaviest single member of the structure.To substantially reduce the weight for this fighter, a newly developedaluminum alloy of exceptional strength was used. This was Super Ultra Duralumin,sometimes called Extra Super Duralumin (ESD). Pioneered and developed by SumitomoMetals Company, this lightweight material was in itself a landmark developmentin Japanese aviation technology. The alloy was rich in zinc and chromeand was similar to to modern-day 7075 aluminum material. Compared to previouslyused alloys, ESD had a 30-40% greater tensile strength and 70-80% higher yieldpoint.The correct designation is AA 7075 T6 DIN# 3.4365.The key to AA7075 T65.1-6.1% Zn2.1-2.9% Mn1.2-2.0% Cu0.2% Ti<0.5" othersyield point 510-550N/mm2. (that's higher than most average quality steal with around400N/mm2.)This material ages badly and can be scoped out with eg a screwdriver on survivingZeros.--------Read this topic online here:http://forums.matronics.com/viewtopic.p ... ___Subject: Re: Pietenpol-List: Carlson aircraft strut fittings

Original Posted By: Michael Perez
Tom,I'm using 6061T6. It has a yield strength of at least 35,000 psi. With 3/4 inby 3/4 in stock and the 5/16 in bolt hole, you are left with 0.33 sq in holdingyour strut. Theoretically, that 0.33 sq in piece would fail under a load ofapproximately 11,500 lbs. Yes, 7075 is stronger but certainly not necessary.That's probably why Carlson sells the 6061T6 stock only.Greg BaconMtn. Piet, NX114DOn Jul 31, 2013, at 8:49 PM, TOM MICHELLE BRANT wrote:> > I've just ordered some strut material from Carlson and I've been surfing thearchives on how the fittings are being made. It appears most folks are using7075 aluminum inserts for the strut ends. I'm wondering why 7075. I understandthe strength is better but really the struts are 6061 so if the fittings aretwice as strong by using 7075, doesn't that just move the failure point to thestrut rather than the fitting? Plus the strut material material area thatis in contact with the bolts is much smaller than the area of the insert itself.Is my logic flawed here?> > I thought I read that the corrosion resistance is better in 6061 but I mightbe mistaken as I've read a lot on the different alloys today and might have itconfused with another.> > Thanks,> > Tom Brant> > Sent from my iPad> > > > ________________________________________________________________________________Date: Thu, 1 Aug 2013 09:24:21 -0700 (PDT)