Flying wing as cheap and simple option for basic fun flying.

[Hephaestus]

From my experimental models the improvement in performance that tip fins, endplates and winglets make is related to the aspect ratio. Aspect ratios > about 2.5, effective span is probably increased and so is performance - for lower aspect ratios the tip fins seem to interfere with the formation of a stable vortex at high alpha and the craft becomes less stable and likely looses lift.

Now here's the question... It's totally applicable to the LAR in facetmobile and delta designs, but does that transfer to aircraft that aren't going to hit those kinds of AOA...

 

[Norman]

Now here's the question... It's totally applicable to the LAR in facetmobile and delta designs, but does that transfer to aircraft that aren't going to hit those kinds of AOA...

Are you saying that slowing down to land isn't important to you? Because for a tailless low AR airplane needs vortex lift to reach high CL for a slow landing.

 

[Hephaestus]

Going by sockmonkeys sketch, no I wouldn't expect he's planning to use a high AOA approach, flatter like a b2/fauvel/etc.

He's got it drawn with a fair bit of wing area, keep it light and it's not going to be needing vortex lift to make a reasonable approach or landing speed.

 

[henryk]

for a tailless low AR airplane needs vortex lift to reach high CL for a slow landing.

=freewing.,hang gliders...

 

[rotax618]

Sockmonkey’s Possum is a short span plank so it will probably behave more like a conventional platform and have a alpha max of more like 12-15deg rather than a deltoid or obloid planform which would be still be providing lift up to 45deg.

 

[Victor Bravo]

For two separate reasons, this discussion is a poster child for R/C model testing.

Reason 1 - I know model testing works really well on large configuration choices and major layout change experiments... R/C models may not give you any usable results for fine-tuning an airfoil (because of Re and scale effect) but it will immediately give you useful information on gross "big picture" design elements like the major configuration and shapes is being discussed here.

Reason 2 - See reason 1 above

 

[rotax618]

Just as an example look at the performance of David Rowe’s UFO on youtube, and consider a “Possum” with the same 12’ span and a chord of 9.4’ (equivalent area), without any hard data I predict the low speed and climb performance of the rectangular planform will certainly be inferior.

 

[Aerowerx]

With a big enough engine you can make anything fly.

Are these RC models you are discussing overpowered? Or is the horsepower also scaled appropriately?

 

[TFF]

RC gives you non theoretical language.

Once you know the language, you understand how far out a concept can be from your normal. It’s one reason I like steal tube and wood wings. It Is like a model airplane in concept.

Although I have some composite models, foam and fiberglass in the model world, they are way above practical just like the real ones when it comes to design. You have to be into them to want to design them.

With the language, you can see the design. I see the design. I look at an airplane and back build it. Take it apart in my head. When I see a plane I either know the language right away or know it’s out there beyond what I know.

1/4 scale Sopwith Swallow. Monoplane Sopwith Camel. Just needed to whittle it out.

 

[Victor Bravo]

You would over-power it, then collect data at various power settings to see whether there really needs to be X power-to-weight ratio.

 

[Hephaestus]

You would over-power it, then collect data at various power settings to see whether there really needs to be X power-to-weight ratio.

And then repeat it with increasing weight until you can't get airborne.

 

[Sockmonkey]

Going by sockmonkeys sketch, no I wouldn't expect he's planning to use a high AOA approach, flatter like a b2/fauvel/etc.

He's got it drawn with a fair bit of wing area, keep it light and it's not going to be needing vortex lift to make a reasonable approach or landing speed.

18 square meters of wing area on a single-seater. Granted, being a LAR means it's not gettimg the full benefit of that area, but that's still a good bit of wing.

 

[rotax618]

I’m sure that the Possum concept is sound and with careful design it could accomplish the aims of the thread, could be more useful if it had folding wing Tips like the Flea.

 

[Victor Bravo]

But... but... the question is not whether something strange can be made to fly. That's been proven a thousand times. It's even quite a noble pursuit in many cases (Tacit Blue, F-117, B-2 et al).

The question is what do you get in return after you have made something strange fly. Lockheed and Northrop got billions of dollars and my Uncle got some interesting military capability.

But what would average fun flyers like you and I get for succeeding with something really out of the box?

If we built a man-carrying Lazy Bee or Stringless Wonder, it would be cool enough to do, just to have done it. Like the "flying stop sign" and "flying lawnmower" R/C models. But then what?

I'm NOT trying to rain on anyone's parade here, or throw a wrench into any one's creativity. All I'm thinking is that it becomes a very slippery slope to pursue something, get all tunnel-vision on it, and give up way too much in order to achieve it.

Don't ask me how I know this in aviation !

 

[cluttonfred]

Sometimes building something different just to learn something new is good enough in terms of goals, but I do get VB's point that if you want to create a design that will be built by others (setting aside any business aspirations here) then there needs to be a selling point. For me, the appeal of planks and low AR tailless designs is the potential for building and storage in a small space. Low-speed handling advantages can also be part of the low AR appeal.

 

[Sockmonkey]

For me, the appeal of planks and low AR tailless designs is the potential for building and storage in a small space. Low-speed handling advantages can also be part of the low AR appeal.

Yep. Plus the wing is a simple build with only a handful of identical ribs. Doing the wing ribs is the bit that gets on everyone's nerves.

 

[Hephaestus]

All I'm thinking is that it becomes a very slippery slope to pursue something, get all tunnel-vision on it, and give up way too much in order to achieve it.

So we should all just be happy with RVs and cubs and Cessnas? Maybe we'll get the design bureau to approve a Rutan here or there just for something different?



Sorry betting VBs had a rough day.

 

[Victor Bravo]

Again I'm not actually trying to spoil any one's ideas or pursuit of something new. I have plenty of weird things I'd like to do, just like everyone else.

My main point was that we can all easily work way too hard to solve a set of problems with some strange configuration... and victoriously make something fly... and then realize later the resulting airplane was not worthwhile.

I wound up almost completely re-designing the Cessna landing gear structure a few years ago. I had taken over an STC approval for converting the Cessna 172 back to the tailwheel configuration. The OEM parts were prohibitively expensive, and I figured I could create an approved parts kit for this conversion. With a lot of help from a structural engineer, I came up with something that would have worked perfectly well, and improved several things to make a more robust system for bush pilots. It would have been less expensive and easier to convert than using Cessna parts. In the end, the cost of completing the FAA testing and certification was too high for my budget. So I set it aside until I could afford it.

Then one day after I had taken a step back from it, I realized I had lost a fair chunk of my sanity, three years of no flying, about fifty grand, my wife almost left, and all I had to show for it was that I had come up with something clever that woulda-shoulda-coulda worked.

They say failure is the best teacher, and I'm offering the cap, gown, diploma, and degree to you all... but you get to use the tuition I already paid

 

[jedi]

..............
They say failure is the best teacher, and I'm offering the cap, gown, diploma, and degree to you all... but you get to use the tuition I already paid

VB - I think I am enrolled in your class professor.

Does this aircraft have any use?

We seem to all agree the above is not worthwhile but I keep coming back to it.

This reminds me of a example from engineering school. A classmate was visited by a traveling salesman trying to keep afloat a home insulation business.

The newly married student had recently purchased a turn of the (20th) century uninsulated home. He pulled out heating oil receipts and did the math showing that it would take nearly fifty years to pay for the insulation the salesman was selling and he sent the sales man packing.

However, in his engineering mind he knew that the improved comfort and economy was a good thing, he just could not prove nor justify it.

Within two years the cost of heating oil was rising and soon was well above the ten cents a gallon used in the example. It is very likely that the house survived the Detroit riots and it may be still standing this day.

Conclusion: If the results are questionable so are the engineering assumptions and vice versa.

PS: I think there may be a market for a tail wheel conversion on a C-172. There is one available for my sons 175 but as you say it’s cost benefit numbers do not work out.

 

[Sockmonkey]

Insulation would also help boost the place's resale value and reduce how often repairs have to be done, so he really wasn't factoring in all the benefits. Plus, it makes the AC more effective in the summer so you save money there too.