Ross's Video on Dark Aero

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berridos

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Would be interesting to open up a thread on their sparless structural wingdesign. Wonder what are the advantages of such a wing . Looks to me like the ribs suffer an enourmous stress in a shearplane they are not designed for..
 

rv6ejguy

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Wing was static tested for both positive and negative loading and seems reasonably light. Lots of ways to design a wing that works. Lots of bonding area and support to maintain shape. All seems reasonable to me.

Now the aluminum engine mount won't withstand fire very well so that part may be changed for production.
 

Lendo

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I am most interested in responses to this question. I notice the G-loads tested are +3.8/-1.5, not as high as one might expect and certainly not Aerobatic 6G. So maybe there are limitations to this design approach. I just can't see how the usual carry through (the Fuselage) main spar is accomplished. I can see how the Skins are well supported, but how the loads are transferred to main mount points is lost to me.
George
 

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berridos

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I am not sure that we have continous little spars. If we focus on the last two sections between the three last ribs, the longitudinal elements are discontinous. I still think the ribs are continous and the longitudinal elements are inserted at each station.
I wonder if the logic of this contruction is to avoid sandwich in the outer skin and only sandwich internal elements.
 
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bhooper360

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I notice the G-loads tested are +3.8/-1.5, not as high as one might expect and certainly not Aerobatic 6G.
There are many metrics of strength. John Roncz says he won't get into your homebuilt unless it's been designed to +12 Gs. Rutan's minions have gotten decades of safe pleasure out of misconstructed, bubble-filled spar layups. Some Pitts S-2 has a load limit of +6/-3, and it even says so right on the dash.

Maybe wing spars are a holdover from legacy construction methods. Maybe they just became entrenched in the homebuilder psyche because it's easier to run the calculations, even though the composites are strong enough without them.

One time I stayed up late and put my spar-less wing in Ansys student version, with some fancy parametrized constraints: number of layers, density of foam. When I checked the results the entire top surface of the wing was always in failure! I didn't have whole plethora of spars running through my spar-less wing.

The DarkAero looks like a toasty fish, they're obviously passionate about engineering. Also, I learned some stuff just by watching their videos. I hope they do well at Reno, then everybody can throw away their stupid glasairs and embrace Technology.
 
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BJC

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John Roncz says he won't get into your homebuilt unless it's been designed to +12 Gs.
That is a good policy for people as big as John.
Some Pitts S-2 has a load limit of +6/-3, and it even says so right on the dash.
The TC Pitts S-1S and S-2A and B were certificated to the FAA criteria for aerobatics, i.e., +6 and -3. The airplanes are much stronger than that. When I was younger, I routinely flew my S-1S to +7.5 and -6 g. I knew pilots who routinely flew harder.
I hope they do well at Reno, because then everybody can throw away their stupid glasairs.
What makes a Glasair at Reno stupid?


BJC
 

Rhino

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...What makes a Glasair at Reno stupid?
Apparently they don't embrace technology, whatever that means. The DarkAero looks a lot like a Glasair to me. Similar airframe and similar engine. Maybe the DarkAero has a new glass panel he likes. When you face it, avionics are about the only true new technology in small aircraft. Most everything else is just incremental improvements in old technology. And if old technology is so bad, I guess he wants to get rid of P-51s at Reno too. I think they're still about as awesome as you can get in piston aircraft. Maybe I'm just old school.
 

bhooper360

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That is a good policy for people as big as John.
I have a persistent, nagging fear that I'll run into John Roncz IRL and he'll ask me about my tail incidence calculations. I've had this fear ever since I started designing my homebuilt.

When I was younger, I routinely flew my S-1S to +7.5 and -6 g. I knew pilots who routinely flew harder.
Things are different now. All of our booger-flicking, childish giggling food fights and related antics are completed in full accordance with the published limitations, insurance requirements, the local and state ordinance, and additionally all applicable wishes of our mothers as well as the Holy Spirit as we understood them (and as they were communicated to us at that time), in order to further the image of the sport, the country and the Holy Father. Amen.

And if old technology is so bad, I guess he wants to get rid of P-51s at Reno too.
That's right, I'm coming for your P-51s next, right after I get rid of all the aluminum baseball bats and cupholders.
 
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bhooper360

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Not wrt how Pitts are being flown in competition and airshows.
In the 80s every other airline pie-luht had an S-1 stashed away in a corner of their garage. These days they're rotting away, and there's a community of ardent middle-aged men encouraging the rebuild and restoration of these antiques. They're worth any price, supposedly. And after you buy one, you can spend a week with Budd Davisson at his bed-n-breakfast halfway across the country, just to learn to land in one.

The S-1 is a very compact, small and simple airplane. I don't know how they flew them in the 80s and you can watch the footage from Nationals last year. They're bobbling up and down gently on the level lines. They won't fly them fast, they won't snap them on downlines, because they don't want to replace any parts.

There is a local community of serious competitors who fly the Pitts, with the WolfPitts wings and fancy engine components, and this is what they didn't say to me: "If I were in your situation I would look into a used Pitts."

I fixed the quote accreditation.

I just can't see how the usual carry through (the Fuselage) main spar is accomplished. I can see how the Skins are well supported, but how the loads are transferred to main mount points is lost to me.
Note the giant box of not-spars which is was omitted in your photo. If you had a bunch of shiny endmills and a few sheets of composite sandwiches you really wanted to use, you could benefit from designing your wings this way as well.
 

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TFF

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I think the only people who fly the Pitts G limits are the Europeans. Several people had asked Pitts about the G limit and he said that’s minimum spec for certification so that’s what I wrote down. Not the answer you want. It is known that from first on, he had numbers checked or run on the planes. They are also known for not breaking up in the air. It’s now not the preferred weapon but the few who try unlimited can get through with 7s and 8s on the G meter. Many people have done there own analysis on them just like Stardusters, Tailwinds and Skybolts with enough searching, you can find them. I don’t think any one of them have come up with a deficiency. The Pitts experts are on the Biplane Forum. They are experts.
 

Pops

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I never had any thing to really get wild in. Maybe that's a good thing. The Falconar F-12 was rated at +9 and -6 at 1600 lb GW. Normal GW was 1800 lbs. So I would play around a little and have fun, but getting beat up where when you land, it feels like you just got body slammed by Hulk Hogan is where it stops being fun for me.
Now at 81 years old, 2 g's is a lot. :)
The F-12 loved to spin. Either way, right or left, easy in and easy out. Very predictable in everything . Great airplane.
IF I was a young thing again , a Pitts would be fun. For Sure.
 

Victor Bravo

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The engineers here can correct me, but I don't think there is any such thing as a "spar-less wing". There are wings without traditional vertical shear webs, but no wings without some sort of spar cap, even if it is built into the skins. The SZD-56 "Diana" racing sailplane comes to mind.
 
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