What's wrong with the Affordaplane?

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Tiger Tim

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Or, more correctly, how would you fix it?

Like so many others, I'm intrigued by this simple-looking airplane and interested in building something like it some day. I don't know if it's the in-your-face simplicity of the airplane, the excitement of flying so exposed (while still in a normal-looking plane), the idea that it could be the modern descendant of the primary glider or just the cost-effectiveness implied by its name. Point is, it's alluring.

The trouble is, they don't seem to work. I've read about how they're basically guaranteed overweight and I too can see the somewhat questionable load paths. I've never seen a picture of one flying higher than ground effect and even those are hard to find. It doesn't seem like there's a shortage of A-Planes being built but even then no two are alike.

So fundamentally what's wrong with the A-Plane? Are they victims of builders making them 'better' without really knowing what they're doing? Is it just an overweight ultralight that would be better off re-branded as an LSA with maybe a little more wing? Is the whole concept just fundamentally flawed? Is it a wildly under-engineered scam? A zillion plans at just ten bucks a pop adds up, you know.

Let's say it can be fixed. How would you do it? What are the most glaring problems with the Affordaplane's design? What would someone need to keep in mind when designing something similar?

Here's what I have in mind: a flat-fuselage version of some classic lightplane. It can be a Cub, Champ, Stinson, Rearwin, Cabin Waco or whatever but I like planes with character and this is the lazy way to achieve that. Ideally I'd like the rear fuselage covered but since you apparently can't do that on the A-Plane maybe there's a good reason not to do it on any plane (why is that, anyways?).

Other points to tick off:
-Part 103 eligible
-Simple construction (I have riveted tube in mind for the majority of the structure)
-Materials for large parts should be obtainable in just about every major city, small specialty stuff can be mail ordered, of course
-Four stroke engine like a half VW or something (this would of course limit the weight of the rest of the plane)
-Capable of hauling a 230lb, 6' 5" guy into the air

I'm not looking for anyone to do the work for me, just a reality check to see if this is even something attainable.

-Tim
 

Turd Ferguson

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Oh, there's some out there that actually fly. Some have crashed so they get airborne somehow. Some have n-numbers. It may be a challenge to build one under 254 pounds.

Start running the numbers on one and it should become apparent where the problems are......
 

TFF

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If you can make 254lb your a success, if not your a failure; it is that simple. A friend is building a Legal Eagle XL and I have seen one fly. Climbs out initially at a 45 degree angle with the 1/2 VW so it climbs pretty good. Making it 254 will require diligence. If you start adding gadgets and fancy paint or thicker materials it will be overweight. ULs are not super strong like a certified airplane, you cant over fly one and expect the wings to stay on. Fly in its designed range and safe as can be. It takes training.
 

WonderousMountain

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My posts do not always register, I meant that I would replace the 2D fuselage with a tailboom. Since this makes it a pod and boom of which the market has dozens some better some worse, I don't see any point in designing one. Not much help, but that's what I would do.
 

Turd Ferguson

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-Part 103 eligible
-Simple construction (I have riveted tube in mind for the majority of the structure)
-Materials for large parts should be obtainable in just about every major city, small specialty stuff can be mail ordered, of course
-Four stroke engine like a half VW or something (this would of course limit the weight of the rest of the plane)
-Capable of hauling a 230lb, 6' 5" guy into the air

I'm not looking for anyone to do the work for me, just a reality check to see if this is even something attainable.
I think an ultralight with a profile fuselage is entirely doable. I'd start from scratch before I'd try to "fix" an affordaplane because I think it would be less work.
 

Tiger Tim

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I'd start from scratch before I'd try to "fix" an affordaplane because I think it would be less work.
I thought I had communicated it much better than I had but that's the intent. I was just wondering if there were any 'traps' in the design of the A-Plane that seem like a good idea but aren't.

Assuming I was starting with a clean sheet, where would I start?

-Tim
 

nerobro

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Traps? yeah. the way the rear cabin pillar is setup. The landing gear, if they fail, fail through the pilot. The arrangement of struts holding the engine mount, is not a good layout either.
 

Tiger Tim

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With the fuse or entire airplane?
Whole plane.

Off the top of my head, I suppose I need to start with the wing. I imagine I need to size it and pick an airfoil based on my target weight and stall speed, sort out the forces it will see in flight, and pick out appropriate materials. My gut says the tail is next as it needs to be sized appropriately(tail volume). Last of all would be the fuselage to tie it all together and the whole time I'd need to keep careful track of projected component weights to stay on target.

Am I close?

-Tim
 

rtfm

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Hi
Another way to do it would be to draw your favoured design till you're happy with it, and then do the wing. That would be the more aesthetically pleasing way to go.

Duncan
 

Tiger Tim

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You boom guys keep losing me. Ambiguous one word replies tell me you don't want me here. If that's the case just come out and say it, or PM if you don't want your opinion to be public.

-Tim
 
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WonderousMountain

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The configuration is known as pod and boom. Imagine a 6 inch tube going from the lowermost part of the cabin straight on to the tail. Sometimes the tube can go from a high wing straight to the tail. Figure 3 eighth inch walled 2 inch square tubes are equivalent in weight to a 6 inch square tube of equal thickness or a round one that is very stiff but doesn't tolerate dents which can happen from ground handling. It is a very strong way to make a tail, and simple which is why they are common enough. Some favor the profile fuselage, it certainly looks interesting. If leaving the profile fuse in tact the most obvious loadpath is bottom as it is, and the top tube raised all the way to the wing. The disadvantage of that is truss web is about twice as long so buckling will have to be looked at. That still leaves the shrouded cabin as an unbraced trapezoid held together by oversized gussets and hopefully solid aviation or military grade rivets. Oh, loadpath on landing gear, which is designed to add damper/spring? The biggest problem however, is that I would not want to tell another pilot or designer that I actually thought this was a sound choice. Now if you're giving me one, then sure I think it's a wonderful aircraft. We here at HBA love question, and this is a legitimate topic given the volume of interest in the plane. Start with a clean sheet, I guarantee you it will outperform the afford a plane with the same engine. Or at least be safer, more conscientious.
 
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autoreply

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Or, more correctly, how would you fix it?
Start from scratch. It's hard to get a FAR103 UL that's light and strong enough, but by no means does it take very complex calculations.

This is one of those "designs" where you could show a couple of pictures to an engineer and then ask "what's wrong with this aircraft". If they can't name at least 10 items; don't hire them...

Like so many designs, notably FAR103 UL's, it doesn't seem "underengineered", but non-engineered. I would bet a good bottle of Scotch that it will never even survive half the ultimate load (3G). just imagine what 1500 lbs of compression on that cockpit section would do...
 

Turd Ferguson

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Whole plane.

Off the top of my head, I suppose I need to start with the wing. I imagine I need to size it and pick an airfoil based on my target weight and stall speed, sort out the forces it will see in flight, and pick out appropriate materials. My gut says the tail is next as it needs to be sized appropriately(tail volume). Last of all would be the fuselage to tie it all together and the whole time I'd need to keep careful track of projected component weights to stay on target.

Am I close?

-Tim
Yea, you can re-invent the wheel or just "borrow" what is already successful. The parameters for an ultralight are mostly defined by the rules. The weight and speed sort out the forces it will see in flight. Just copy a wing that is already in use, something like what's on the minimax. It's light, adequate strength and fits the performance parameters. And it's easy to build.
Get your fuselage profiled out and when you start looking at loads and stiffness, keep in mind a 2 longeron truss like the a-plane might not be the best option. In fact it probably isn't the best option. The boom option isn't too bad - you'd have to add your profile shape to it via other means. The boom would probably be my second choice.
 
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