Affordaplane wing and tail design

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Cunning_Runt

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Are the Affordaplane wing and tail safe designs? From what I've read here, the AP fuselage is poorly engineered and my gut tells me the whole airplane is probably flawed. But I'm intrigued by the simplicity of the wing and tail construction. Are they examples of good engineering, or should they be avoided?

Thanks!
 

Victor Bravo

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Not an engineer, no ability to technically validate the design. Others here are highly qualified to do so.

That said... Reputation for simplicity: good. Reputation for structural engineering: poor. Probability of not passing a detailed engineering review: high. Number of fatalities from in flight failure: low.
 
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Cunning_Runt

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Thanks, VB. I'm attracted by the simplicity of the wing and tail. But they might be too simple. Maybe some of the engineers here could weigh in on the topic.
 

mcrae0104

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Are the Affordaplane wing and tail safe designs? From what I've read here, the AP fuselage is poorly engineered and my gut tells me the whole airplane is probably flawed. But I'm intrigued by the simplicity of the wing and tail construction. Are they examples of good engineering, or should they be avoided?

Thanks!
Do you have a set of plans?
 

Cunning_Runt

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Do you have a set of plans?
Yes. I don't want to show the wing plan here because of copyright issues, but the wing frame consists of a 2" X .058" wall 6061-T6 tubing leading edge, a 1 1/2" X .058" tubing trailing edge, 1" OD compression ribs, and ribs of 1/2" bent tubing, all held together with bolts and gussets.

The tail surfaces are simple outlines of 1" OD tubing, with no ribs and no external bracing.

I don't intend to build this airplane, but am reviewing it for design ideas. It appears to be elegantly simple. But if it turns out to be an example of bad design, I can learn from that too.

Thanks
 
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BBerson

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The question: "is it safe" cannot be answered without a detailed study of every issue. Such as intended gross weight, flight speed etc.
 

Rockiedog2

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didn't we have a big discussion a while back about the AP and there were a lotta professional sorts that slammed it? seems like it may have been buried in some other topic
 

Cunning_Runt

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The question: "is it safe" cannot be answered without a detailed study of every issue. Such as intended gross weight, flight speed etc.
As the AP is a UL design, the intended gross weight would be about 450#, max speed 55 kt. The fuselage design is suspect, I just wondered about the wing and tail construction.
 

BBerson

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As the AP is a UL design, the intended gross weight would be about 450#, max speed 55 kt. The fuselage design is suspect, I just wondered about the wing and tail construction.
If you are building to the plans, then check other ultralights designs to compare the tube sizes and thickness and length of overhang etc. for the wing.
For the unusual unbraced tail, a load test might be needed.
 

Aviator168

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As the AP is a UL design, the intended gross weight would be about 450#, max speed 55 kt. The fuselage design is suspect, I just wondered about the wing and tail construction.
You didn't mention that there are two tension wires supporting the tail from strut attach point on the wing, but the tail looks weak in torsion.
 

Topaz

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Unfortunately, as Orion would say (and frequently did), asking "is this safe?" is like asking, "is this tall?" Safe relative to what? How tall is tall?

I'm not fond of the Affordaplane, mostly because, even as an ultralight, it's not really the sort of airplane I'd personally want (I'd go for this, myself: Airdrome Aeroplanes ~ Holden, MO).

The real problem with the Affordaplane is that, while thousands of plans sets have been sold, very few have been completed and flown. That's more a function of the impulse-purchase price point on the plans than it is any specific deficiency in the plans or airplane themselves, but it does mean we have very little data on how the airplane flies or what the potential accident rate is, to compare to other, competing, designs.

Even if a qualified engineer were to do a complete analysis of the design, both aerodynamically and structurally, he/she would want specific criteria against which to judge the design, and even then could only tell you "meets the criteria" or "doesn't meet the criteria", rather than, "this is safe."

Nobody can really answer your question in the way you want.
 

Victor Bravo

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They just don't exist for the texas parasol.
Nnnnoooooo.... the Texas Parasol is brilliant in some respects and unfortunately it may well be marginal in others. There was a group in Canada that did an analysis and found some weaknesses that didn't need to be there.

The fuselage design, using extruded angle and squeeze rivets, is a great idea. Being able to use AN squeeze rivets is a rare example of the strongest and most robust also being the cheapest and longest lasting. But angle is less stable when loaded off-axis than tube (as used in the tube and gusset method), so there is a compromise and balance between the advantages of the tube versus the disadvantages of the pop rivets. But the time and cost to build a "good enough" fuselage using angles and a rivet squeezer is very low. And the angle fuselage fasteners can be inspected easily in the future.

The wing ribs, cabane structure, and landing gear on the Texas Parasol have always looked very marginal to me. Apparently it looked marginal to other people who probably had higher qualifications than me. There is a huge discussion thread and debate about this subject (the Canadian modifications) that I found on a Google search. An epic battle between Mr. Lamb and the people who called the structure into question.

For the record, I really like the TP. But if I did get involved in building one I would use a different wing structure, Carlson Sparrow or Kolb or something more robust.

Wow... a cheap and sufficient angle fuselage and Kolb wings, using the ~!(#*$ brilliant Kolb wing fold method, and an off the shelf fiberglass leaf spring from a large truck or trailer for a main gear. There goes my head for a few days.... hey where did this huge rabbit hole come from...Fritz... Matthew... heeeelp!
 

nerobro

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Fair enough. There are at least a lot more documented builds. More that are actually ultralight. And the designer isn't going to call your work and complain about you when you criticize the design.

Edit: And to add, "looking marginal" is how a lot of airplane parts look. Hah!
 

kirbylee

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Yes. I don't want to show the wing plan here because of copyright issues, but the wing frame consists of a 2" X .058" wall 6061-T6 tubing leading edge, a 1 1/2" X .058" tubing trailing edge, 1" OD compression ribs, and ribs of 1/2" bent tubing, all held together with bolts and gussets.

The tail surfaces are simple outlines of 1" OD tubing, with no ribs and no external bracing.

I don't intend to build this airplane, but am reviewing it for design ideas. It appears to be elegantly simple. But if it turns out to be an example of bad design, I can learn from that too.

Thanks
What did you finally decide on the affordaplane? The wing design has been successfully used for years, decades actually.
 
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