Material Question

[bpaynebearhawk]

Hi, I was sourcing some 6061-T6 aluminum locally for the wing spar spacer bars, and I was quoted 6061-T6511. My question, is 6061-T6511 an allowable substitute for 6061-T6?
Thanks,

[marcusofcotton]

I'd say very acceptable, actually better. Google is helpful...

https://www.quora.com/What-s-the-dif...-T651-aluminum

[Chewie]

I actually had a similar question comparing 2024-T3 to 2024-T81, the latter having come from Boeing Surplus.

[bpaynebearhawk]

Thanks for the responses, and I had seen the page link referenced.

I was looking for someone who had possibly already contacted Bob and had a more "official" answer.

I cannot be the only one who has asked this question before, but I haven't yet found it answered on the Bearhawk forum. I did find some aluminum suppliers that list 6061-T6 & T6511 together with the same Ksi, but I was hoping to find a Bearhawk specific allowance for T6511.
Thanks!

[Archer39J]

-T6511 is just stress relieved. If you get material certs it will have the specific properties for that material batch, which for the few I've gotten have been higher than published values we use for design.

On my 4-place plans everything wing related is 2024. I'm not sure what's used on other plans or even what parts you're referring to, but if -T6 is called out you're fine using -T6511.

[Scout]

My patrol plans call for 6061-t6 on aft wing spar attach doublers as well. I was wondering about using 2024t3 instead myself?

[Archer39J]

My patrol plans call for 6061-t6 on aft wing spar attach doublers as well. I was wondering about using 2024t3 instead myself?

Generally you can substitute stronger alloys, 2024-T3 being stronger than 6061-T6. Though again I'm not positive about the use case or why Bob uses 2024 on the 4-place and 6061 on others, probably just doesn't need to be as strong. If you're not comfortable making that decision yourself checking with the designer would be the way to go.

[johwiltb]

Generally you can substitute stronger alloys, 2024-T3 being stronger than 6061-T6. Though again I'm not positive about the use case or why Bob uses 2024 on the 4-place and 6061 on others, probably just doesn't need to be as strong. If you're not comfortable making that decision yourself checking with the designer would be the way to go.

Just for reference, the Model B 4-place also uses 6061 for the rear spar cap strips.

[Archer39J]

Oh it's those little strips this is about, thanks for pointing that out.

[Scout]

Patrol Rear spar attach fitting where the bolt attaches to fuselage also is 6061. I’m going to change to 2024t3

[Mark Goldberg]

Either is acceptable. At the factory we use 2024 because we don't like to have 6061 laying around that might get confused with 2024. Kind of like how repair shops do not like to keep soft rivets in inventory to avoid them being used in the wrong place. Mark

[Scout]

Thanks Mark, I can tell you place safety first having policies like that I’m sure 6061 is cheaper but little things like that can save from having big problems.

[svyolo]

I am not sure that substituting a stronger alloy is a good idea on something like a wing spar. It might seem intuitive that something that is stronger is OK/better, but it might also cause an uneven stress distribution, which can concentrate stress in a few small areas. I might ask the designer-in-chief.

[Archer39J]

I am not sure that substituting a stronger alloy is a good idea on something like a wing spar. It might seem intuitive that something that is stronger is OK/better, but it might also cause an uneven stress distribution, which can concentrate stress in a few small areas. I might ask the designer-in-chief.

Given these alloys have similar moduli of elasticity and yield strengths going up in strength is a pretty safe bet, not the other way though. Corrosion concerns with 2024 should not be ignored either. But yeah, ask Bob if you're in any way unsure.