Materials Specs for Repair Parts

[Chappy]

Dale,

I've been on this list for less than two years, and this critical question keeps coming up: "What alloy was used for such and such part by the factory when they made my (broken, bent or corroded) part?"

When Ultraflight was still in business, we could purchase factory, authentic replacement parts made to spec. With the demise of the factory, the fabrication of repair parts has fallen to owners. Most have been quite skilled in fabricating replacement parts, or have found others to make parts for them.

The BIG PROBLEM is that we don't always know exactly what material was used in the original part, or what material is suitable for these parts!

I've seen suggestions on various forums to use alloys that are most probably not suitable for the parts in question (a recent example: 6061-T6 for the F6 gussets/attachment plates). I'm afraid that some of these suggestions will be repeated until they are considered proper. Dale, now that you are looking in on the forums from time to time, could you please give us some guidance on this important issue, especially pertaining to critical components such as wing attachment fittings, lift struts and attachments, tail fittings, etc.?

Chappy in Virginia

PS. Guys, PLEASE give Dale a chance to comment on this before beginning any general discussions on this issue.

[Dale Kramer]

Bob,

I'm just getting back to this forum after a couple weeks, I will post on other topics needing my reply over the next few days. This is definitely a topic I can provide good info on.

Easy things first, all tubing is seamless 6061-T6. All sheet less than 0.0625 thick is 2024-T3 ALCLAD.

All other sheet aluminum is either 7075-T6 bare or 5052 H34(maybe H32, not much diff).

It is very easy to tell the difference between 7075 and 5052. 7075 is like spring steel and 5052 bends tightly. There are some 7075 bent items, like the fuselage mounted rear wing mount fittings (0.0625 and about a 3/8 radius bend).

I believe all 0.0625 aluminum is 7075-T6 bare and all 0.080 is 5052-H34.

We did use 0.125 thick in both grades but very little 0.125 in 5052-H34. These pieces are quite obvious due to their small bend radius. I don't think we ever made a flat 0.125 thick part in 5052-H34. The only reason we used 5052-H34 was when a part needed a tight bend and strength was not the major design factor.

The only bent 0.125 7075-T6 fitting that I recall are the fittings for the gear and struts on the Series III fuselage where the fittings wrap around the tubes. These are very critically 7075-T6 and don't worry about bending them around the tubes if you make replacements (do not make these out of other material).

If there is any doubt about whether a part is 7075 or 5052, a simple file test will tell you (just make sure that you don't leave any knicks in a part after you test it with a file, use the file like you were bevelling a sharp corner). With the same pressure and file, you will easily take about 5 times the metal away with a stroke on the 5052.

Dale

[Dale Kramer]

Just a couple pointers on 7075-T6:

If you do bend 7075-T6 you need a large bend radius (I think at LEAST 6 times the thickness).

There is a grain to the material and it bends more easily across the grain. Bending along the grain is a recipe for disaster (the big CRACKING noise when 7075-T6 decides to give up). It is the only aluminum that I've used with such a telltale sign of when it reaches its limit. It is also my favorite aluminum grade.

Also, I like to polish and chamfer the edges of the part before I bend it as there will be less failures during bending if the bend is tight.

I also takes a lot of force to bend it.

Dale

[russell]

Dale,
I'm sure you are going to be flooded with questions on this topic: however, it is a topic of considerable concern to me so I just have to ask.

Concerning the bending of 7075 you wrote "Bending along the grain is a recipe for disaster". On my series one I made the fittings that attach the lower wing strut to the axle from this material and made the slight (approx. 5 deg.) bend without the knowledge of which way the grain ran. Did your statement infer that I have made a disasterous mistake in doing so?

The strut tubes you write are 6061. How about the solid plugs in the ends?

Thanks for any guidance you can offer,
Russell Rewis

[russell]

I think I may have answered my own question because after thinking about it, Dale you said "The only bent 0.125 7075-T6 fitting that I recall are the fittings for the gear and struts on the Series III fuselage where the fittings wrap around the tubes. These are very critically 7075-T6 and don't worry about bending them around the tubes if you make replacements (do not make these out of other material)". I noticed that these fittings are bent in two directions perpendicular to one another which indicates that one bend is parallel to the grain.

I also asked the question about the material that the strut plugs are made from prior to reading your earlier post which discussed this.

Thanks for taking the time to supply us with all the information. It has eased my mind and made it possible to do replacement work (not modifications) to my Lazair.

Russell

[Chappy]

Dale,

Thanks for taking the time to post the specifications for the various parts and fittings here! These questions have been showing up in various Ultralight web groups for the ten years I've been checking in on them. Many times I've seen suggestions for incorrect materials for repair parts. I think I've been the only person telling people that the wing attach fittings were fabricated from the 7075-T6 alloy, and without anyone to confirm that, and back me up, I'm not sure my input has always been heeded. Heck, after twenty two years, I'm not sure I was even all that confident in my recollections anymore.

I very much hope that everyone that owns a Lazair prints out the information you have given here and pastes it into their manuals!

Chappy

PS. I remember the engine mounts you designed and built for the KFM's that used 7075-T6 "springs" in place of rubber mounts. Because the fatigue life of aluminum is so finite, that design really freaked me out. I've always wondered how they work out in the long run.

[lazairiii]

Dale,

What material exactly was used to manufacture the solid rod that runs up to the mixer from the rudder pedals? Do you happen to recall?

Thank you,
George Curtis

[Dale Kramer]

Just to have it all in one place I'll say it here too.

All solid round aluminum parts were 2011-T3.

If you can't get that, 6061-T6, 2024-T3 or 7075-T6 would be suitable (and perhaps better) replacements. 2011-T3 just machines so nicely.

[art]

Does anyone know the wall thickness of the ruddervator pushrods? Thanks Art

[lazairiii]

6061-T6 1/2" OD x .035 wall with a .430 7075-T6 plug (drilled and tapped) for the rod end. 2024-T3 would work for the plug material also.

I personally used SS rivets instead of the Aluminum rivets to attach the plugs into the push-rods on this application.

George Curtis