Thickness of 6061-T6 Wing Ribs

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usmc35cc

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Greetings Builders,

I am building my own design, tailless, aircraft. Wingspan is 40’. I am going to use 6061-T6 for the wing ribs.However, I’m running into a little snag... What gauge should I use. What do most aircrafts call for? The only blueprints I have is for a Pietenpol and that’s all wood - no help there.
 

usmc35cc

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For the skin I’m looking at using 2024-T3 .040” thick so I can counter-sink the holes with 1/8” rivets.

What do you think about using .040” 1mm instead of .050”?
 

Pops

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4 seat Bearhawk uses .025 2024-T3 for the wing ribs except for the 2 closest to the wing root and these 2 ribs are .032 and the root rib is doubled. A .032 right and left rib riveted together. Wing skins are .032 on the first 2 ribs at the root and then .025 to the wing tip.
 

usmc35cc

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My Preceptor N3 rib is .020". As for flush riveted wing skins, you may consider dimpling the skin, and the rib flange. A 40ft span, with .040" skins all the way, is gonna get heavy, quick.
Good to know!!! Lighter is always better. Maybe I’ll go .025” .60mm for the ribs and skin.

I am looking at rib spacing and it seems that it ranges 25%-50% of the chord length. This sounds right, right?

Thanks in advance everyone for the help.
 

challenger_II

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Studying how other folks have done something is always a good idea. As an example, let's take the Vultee BT-13: at the root of the wing, the skins are .040", and the thickness reduces as the skin goes outboard, until you have .025" at the tip.
In all things Aviation, lightness is the quest, while obtaining enough structure to prevent you getting a permanent set of wings.
 

challenger_II

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Dimpling can be as difficult, or as easy, as One makes it. There are dimple dies you can use with a Harbor Freight pop rivet tool.
Oh! And, they will dimple .040": but I DO recommend the pneumatic rivet puller! :)
 

usmc35cc

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By chance, have you studied the Mitchell A-10? You could glean a good deal of information from that lay-out.
Very interesting flying machine. It’s a foam wing wrapped in aluminum. I wouldn’t mind getting a lot of this one just for fun!
 

cvairwerks

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6061T6 will not easily form ribs, unless you are looking at giant ones....like chord sections in the 6-10 foot range, and bend radii in area of a inch or more. 2024T3 is much easier to form and less prone to cracking during bending, compared to 6061. Any severe forming of 6061 has to be done in the T0 temper and hardened afterwards.
 

Marc W

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6061T6 will not easily form ribs, unless you are looking at giant ones....like chord sections in the 6-10 foot range, and bend radii in area of a inch or more. 2024T3 is much easier to form and less prone to cracking during bending, compared to 6061. Any severe forming of 6061 has to be done in the T0 temper and hardened afterwards.
That is exactly backwards. 6061T6 is more formable than 2024T3.
 

robertl

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6061T6 will not easily form ribs, unless you are looking at giant ones....like chord sections in the 6-10 foot range, and bend radii in area of a inch or more. 2024T3 is much easier to form and less prone to cracking during bending, compared to 6061. Any severe forming of 6061 has to be done in the T0 temper and hardened afterwards.
The ribs of a Zenith CH-701 are made of .016 or .025 6061-T6.
 

BoKu

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6061T6 will not easily form ribs ... 2024T3 is much easier to form...
When I talk with people about this misconception, I usually find that it stems from the mistaken idea that the T value stands for some measure of hardness. In fact, it's more like a recipe, a designator for the various tempering processes and their sequence. In practice, 2024-T3 is stronger and harder to form than 6061-T6.
 

BBerson

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Right. The T is a designation for Thermal Treatment. As opposed to H for the alloys that can't be heat treated.
I don't like the use of temper because the word means "make less strong". The word temper started with steel because steel needs another final oven treatment to make it "less strong" so it won't be brittle like a file.
No such oven tempering treatment is needed for 6061-T6 but the word temper is often used anyway.
It can be confusing.
 
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usmc35cc

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That is exactly backwards. 6061T6 is more formable than 2024T3.
Thank you for clearing that up. Almost everything I’ve researched says to use 6061-T6 for the wing ribs. Since my design uses a tapered wing the chord lengths vary from 90” - 21”...
 
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