Valley Engineering's new ultralight

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BBerson

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Stress corrosion ( whatever that is) isn't the issue. Bare 7075 and 2024 can corrode easily without stress and needs an Alclad layer or extensive paint coating.
Tube can't be Alclad.
Ultralights need bendable tubes, that are cheap, and anti corrosive, and available. None of that applies to 7075.
 

kennyrayandersen

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Stress corrosion ( whatever that is) isn't the issue. Bare 7075 and 2024 can corrode easily without stress and needs an Alclad layer or extensive paint coating.
Tube can't be Alclad.
Ultralights need bendable tubes, that are cheap, and anti corrosive, and available. None of that applies to 7075.
I hate when I type something on the mobile and it's lost and I get to do it again. 6061 is perfectly suitable for ultrlights and lighter-weight home-built aircraft.

With regard to using clad material, I haven't analyzed a clad part in my entire 30 year career. I guess the thinking is that it's just extra weight and he plane will be out of service before the corrosion becomes an issue.

It's also the case that stability is a function of E (Young's modulus) which is nearly the same for all aluminums. Note thiugh that many things like struts arw also sized by handling loads which can easily be strength driven. Still I wouldn't hesitate to use 6061 in a homebuilt or other ultralight. It has it's place...
 

Matt G.

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OK. The stress corrosion cracking issues I recall were on Navy ground support equipment about 30 years ago, so it's not surprising that the metallurgy has improved. Still, I haven't seen 7075 readily available in tubing form (can it even be extruded?). But as I said, when buckling (either column buckling or local crippling due to bending) is the primary failure mode, the higher strength gives no advantage, so even 2024 tubing (which is available, though not in as many sizes) isn't used as much as 6061, which is considerably less expensive.

Dana

Support bacteria. They're the only culture most people have.
7075 extrusions are used extensively in commercial aircraft. I've never seen it in tubing form, either though.
 

BBerson

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7075 extrusions are used extensively in commercial aircraft. I've never seen it in tubing form, either though.
Exactly. That is one reason we don't use it.
The same is true with foil. You can't buy .002" 7075 foil. Because ordinary aluminum (1100 full hard) works as well for a fraction of the cost.
 

danmoser

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7075 extrusions are used extensively in commercial aircraft. I've never seen it in tubing form, either though.
7075 tubing is available, but not commonly here in the USA.
It's made in Switzerland, I think .. and has been used regularly by hang glider manufacturers worldwide for a couple of decades.
They have a special process for making it... not the common extruded and drawn seamless tubing processes used to make 6061 and 2024 tubing.
It is rather pricey, but pretty good quality.. 7075 HG frames can be made a few pounds lighter than those made with 6061.

IIRC, it's made in metric OD sizes.. typically 48mm, 50mm, 52mm, etc. with a wall thickness of 0.9mm (~0.035") .. so one size slides snugly into the next bigger size .. meaning you can easily sleeve it to reinforce certain areas.
I've heard the makers of this tubing require a large minimum order and tend to shy away from homebuilders.

If you want to buy some of this 7075 tubing in the US, your best bet might be to contact Wills Wing or their dealers.. they use a ton of the stuff and have a sort of monopoly on the US supply of it.
 

BBerson

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Thanks for the info.
Even if it was available, it isn't weld-able. So Valley couldn't sell an affordable product with it.
 

danmoser

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Thanks for the info.
Even if it was available, it isn't weld-able. So Valley couldn't sell an affordable product with it.
FYI, 7005 alloy is weldable .. certain other 7000-series alloys are as well, but none of them as common as 7005.
Bicycle frame makers use welded 7005 all the time.. a source here: http://bit.ly/1ixO2Jg
Longer tubing section may be available from Easton Aluminum.

The problem is, it must be heat-treated after welding to regain the strength that is lost in the welding process.. no problem for something small, like a bike frame.. but on something as large as an entire airplane framework.. forget it!

I don't think Valley is postweld heat-treating anything, and they're (supposedly) not using welds in highly stressed areas.
 

BBerson

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Until I see a welded aluminum airframe that is 70 years old, my plan is to use welded steel tube.
( for both my airplanes and bikes).

I just wish I could find cheap thinwall steel tube ( like .012" wall).
I know the ultralight bikes use this thin stuff.
 

akwrencher

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Ok, this is bad, but I can't help it. If anyone ever makes an ultralight out of broomhandles, you know you are going to have to give it some kind of crazy name, right? (think flying broomstick.....) :roll:
 

Bill Ladd

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Wilmington, NC, USA
Until I see a welded aluminum airframe that is 70 years old, my plan is to use welded steel tube.
( for both my airplanes and bikes).

I just wish I could find cheap thinwall steel tube ( like .012" wall).
I know the ultralight bikes use this thin stuff.
I hand-braze lugged steel bike frames. What do you need?
 

Bill Ladd

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Mostly 1/2" . Is it available in say .012 or .016" wall?
Let me check my sources. The smallest wall I've ever had my hands on were some Mountain Bike tubesets which internally butted .8/.4/.8. The .4mm is close to what you need, but the OD of the tubes are too large. The straightwall stuff tends to be a bit thicker than that. I'll do some digging and see if what you need is out there in the bike building world.

Will report back here...
 

PTAirco

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To continue this long running thread: This shows the spar construction of the Backyard Flyer. Which I was curious about and hadn't seen close up.

http://old.sportpilot.org/magazine/feature
/2008%20-%2011%20November%20-%20Home-grown%20Ingenuity.pdf



Let's just say my reluctance to strap my warm, pink flesh into this aircraft has reached new heights. And let me repeat, I have always been cautious criticizing another man's design. But this looks unsafe if used as scaffolding 4ft off the ground. Those welds....

Curtiss used a similar spar design using dural and steel tube, but that is where the similarity ends.

by_flyer_spar.jpg
 

kennyrayandersen

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Ft. Worth TX
To continue this long running thread: This shows the spar construction of the Backyard Flyer. Which I was curious about and hadn't seen close up.

http://old.sportpilot.org/magazine/feature
/2008 - 11 November - Home-grown Ingenuity.pdf



Let's just say my reluctance to strap my warm, pink flesh into this aircraft has reached new heights. And let me repeat, I have always been cautious criticizing another man's design. But this looks unsafe if used as scaffolding 4ft off the ground. Those welds....

Curtiss used a similar spar design using dural and steel tube, but that is where the similarity ends.

View attachment 46824
There's not really a good angle you can look at that! It hurts my eye from EVERY angle!:shock:
 

mmatt

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Apr 13, 2015
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315
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Canada
To continue this long running thread: This shows the spar construction of the Backyard Flyer. Which I was curious about and hadn't seen close up.

http://old.sportpilot.org/magazine/feature
/2008%20-%2011%20November%20-%20Home-grown%20Ingenuity.pdf



Let's just say my reluctance to strap my warm, pink flesh into this aircraft has reached new heights. And let me repeat, I have always been cautious criticizing another man's design. But this looks unsafe if used as scaffolding 4ft off the ground. Those welds....

Curtiss used a similar spar design using dural and steel tube, but that is where the similarity ends.

View attachment 46824
Is it just the welds that bother you? To me (but bear in mind that I'm no engineer) that looks like a pretty strong yet lightweight structure.
 
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