Lazair.com

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

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