Видео

Thank you, found all the materials at Walmart!

Nice vedio, but I have some questions about the explaination for the reason about low drag. As model airplane in such size, the uploader said the viscous drag was the most part of drag, I would say, maybe not. This was a very comman model airplane with 7~8 aspect ratio(roughly from the vedio), and the flying speed should not larger than 10 m/s, hence, the thin airfoil theory and lift line theory are valid. That is, the lift line slope is about 2pi, and the induced drag is about Cl**2/(PI*e*AR), and the viscous drag is related to the surface area. The biggest differents about step wing are 1. it changed the wing-tip vortex character and the flow over the surface is transitted to turbulence forcely, which brought a more stable flow pattern; 2. the effcient factor e is changed. So I think we should give more precision way to conlude the reason why step wing is better.

Love the videos. And I do have 3d printers. I've printed some parts for model aircraft before, as well as a couple small slot gliders for the kids. But this video makes me wonder. When you print with a typical FDM 3d printer, there are a series of lines produced on components due to the item being printed in layers. Due to this, there's basically 3 ways you could print a given airfoil, and thus leaving those lines in different directions. EG you could print the airfoil flat, and with a large layer thickness, it may almost appear as though it was made with a stepped design (though the leading edge will also be stepped). You could print the wing on the leading edge... you'd still have lines running the length of it, but they'd be closer together and smoother than the first option... but still bumpy esp in the direction airflow will travel during flight. But this may also end up acting like "dimpling" on a golfball perhaps. 3rd option is to stand the wing on its tip and print it the long way. This would pose the most problems with printing... as well as have the most structural issues, but I wonder if on a final aircraft/glider if it'd be the most effective with regards to lift/drag. None of my printers are big enough to do a whole wing at once, but I can (and have) do them in sections about 8in wide, and then pin them together (either with a printed pin.. or with the wings I made for a plane before, I used some fiberglass rod to make full length spars)

*Smile,,,,,*

Yes, they should be better

Try golf ball pattern, it reduces both friction on both speeds.

Thanks so much for this! I like how you explain the engineering and physics. Question: would a longer wing with a higher aspect ratio be better for longer flights?

I really have to compliment you on your hand-gesture game. Top notch. Idea for explaining missions to military pilots or speaking to italians.

? Increasing reynolds number does increase the sectional lift coefficient and hence the overall lift coefficient is also enhanced.

Are the planes all the same weight? I doubt that ....

You’ve conducted the experiment in the best way possible and still maintaining interest along all the video, very good! Thanks now I can’t wait for the next

I’m ngl, you look like Michael Cera if he made less money

Congratulations I reached your shop!

Thanks so much 😊

Step-airfoil principle used for Fowler flaps.

Nice methodology. I like the launcher. I want to see testing under power

Great video! I have an idea that you could test. What would it look like if you designed the steps in such a way that there was a pocket underneath each one? By that I mean that a horizontal U-shape, or more precisely a C-shape, would be formed under the steps.

Bro, awesome content and very educational while being concise, but loosen your shoulders, and be casual with the voice, you look stiff and tensed

As a percentage of total airfoil weight to surface area the KFM3 was at a disadvantage due to the increased weight of its wider center spar. I guess if you matched the weight of all three planes as a completed plane it might not make a big difference.

I have built a bunch of flying wing rc planes using the KFm4 and versions of the same wing using a an actual symmetrical airfoil. These were relatively heavy fast planes. The "real" airfoil wings tended to be more efficient and faster. The KFm4 planes were very stable in the air they had much less pitch instability and over all flew better. I mostly flew FPV and I liked the smooth flying of the stepped airfoil. I have a bunch of flight videos on my channel from a few years back. Great work on your experiment you got a new subscriber.

Thank you

Dimple surface more effective. It ceates small vertex in each dimple even at high speed. That's why golf ball move far than smooth one.😊

great video

cool! also see my new design airplane ruclips.net/video/yxrxiBRYljE/видео.html

I seem to recall something about "dynamic similitude". Meaning, you cannot linearly scale (your small plane scaled 2x) to get twice the performance - or something like this.

Isn't the introduction of induced vortices on the KF M airfoil functionally the same as the dimple on a golf ball? If so, then why not dimple the wing surface to reduce pressure drag? - Just asking for a friend -

It may ( does) reduce flow ( drag) over the surface. But it doesn't provide more lift. ( speed) When other shapes for the same weight could use surfaces that do. ? Is it about lift? Or drag? Design, or a better form ( wing) . Then realize this is all very slow air speed testing. Drastically changed as it increases. Instead. Use a wing that can sustain thrust. Not a gliding wing. Use steps near the edges that create vortices. Not the whole wing. Use steps on control surfaces for less drag? It's a good topic. Geared to the hobby. Or full scale?

Amazing Work !! Loved It ❤

I really enjoy your scientific approach to this. looking forwards to the next episode

Excellent vid. I'm no engineer, and didn't view all the comments, but here was my first thought. What if you were to make the step smaller, but add many more? I would try milling or forming the top/aft surface of the wing, to have a series of small, parallel, U shaped channels, running from wingtip to wingtip. You could experiment with the size, shape, spacing, and number of channels. Wouldn't be too difficult with a small router with a rounded bit, using a template. This might create an area where, given enough velocity to create a vortex within the channels, the airflow wouldn't have a chance to get between the channels, and contact the surface, creating drag. A bit like the dimpled surface of a golfball, only much more tuned. At slow speeds, there would probably be more drag because of the increased surface area, but once a strong vortex develops in all those channels, the airflow would basically ride across the top of the small parallel vortexes, I would think. The same technique might even work on other areas to help reduce drag, who knows. I'm sure I'm not the first to think of this (there's probably papers from the 1950's discussing all this in depth lol), I'm not sure if it's practical or feasible, and again, have NO idea what I'm talking about, but there ya go ;) Good luck with your projects. 🤘

I don’t believe these are pitch trimmed equally.

These comments are like an encyclopedia. I'm saving them.

This case is only true when your Reynolds number is high enough that there is turbulent boundary layer over the wing. For low reynolds number the laminar boundary layer will separate quickly and the Cd will increase.

This is the kind of content i love. The scientific method applied on a shoestring budget.

Your Talking style is very nice 😊, and great work

very nice work!

DLG gliger：hi

Thank you, great video, and useful for a model I'm building.

Ive been a flying professionally and teaching for almost 30 years. In my opinion this is a great experiment. It makes me very glad to see that we still have young people in this nation with enough curiousity and motivation to try things like this. Unfortunately the experiment while creative is flawed - mostly on the design of th first airfoil. Lift is created by a combination of two principals - Bernoulli's and Newton's. Newtons law says that as air molecules strike the lower side of the airfoil they create a higher pressure area which "pushes" the air foil upwards. This works well on an airfoil where the bottom is perfectly flat. Unfortunately the bottom of the fold over airfoil is NOT flat, while the other two ARE flat. This leads to the first flaw. In the experiment the first airfoil not only has a different topside but also a different bottomside. When doing an experiment it is important to only change one thing at a time. The second flaw has to do with the effect of the step on the bottom. As it moves through the air, it very likely creates a forward pitching moment due to the application of Newton's law as the air flows over the step. This pitching moment should be causing the airplane to try to nose down which the elevator must in turn counteract. The additional drag will reduce the aircrafts performance substantially. The third flaw has to do with the application of the elevator itself. In real life, a pilot operating an aircraft will trim the aircraft so that it is at its optimal speed where the combination of induced drag and parasite drag are at its lowest point. This optimal speed will allow the aircraft to remain airborne for the longest period of time. Unfortunately, the experiment here fails to take this into account. The elevator is simply 'set' prior to flight without taking into account which . The experiment needs to be repeated in a wind tunnel where total drag and total lift can be measured at various attitudes, or it needs to be repeated multiple times using the same airfoil, with different elevator settings. The last flaw is that the aircraft needs to be chronographed/released from a mechanical device so that we can verify that flow of air over the wings is exactly the same for each flight. Still, its a great idea, and I hope this young fellow take my observations as advice and NOT as criticism.

Maybe I misunderstand, but isn't it possible the reason why the 'flat-bottom' fold over did so poorly was because it was actually a modified KFm1 design. It has a step on the bottom, not really a flat-bottom.

Thank you for your work on the KF Trapped Vortex Concept. You might find the paper interesting where the KF concept is applied to a Darrieus Wind Turbine. <PIIS2405844024089503.pdf>

This man will never see a vagina. Ever.

Would be interesting to compare these results to the Lauch speed and kinetic launch energy, as it did not seem to be the same across all models. Speed measurement would also be interesting to get a reynolds number for those gliders.

Please don't do that to your A-26! If you're going to clamp your mike there, please wear a Fairey buccaneer or ohka shirt!

How would they perform add motor induced speeds

I noticed you didn't mention anything about the weight difference between the fold-over, KFM-2 and KFM-3 airfoils. If you could add that to the Flight distance table you showed at 9:34 that could give some more insight into the performance of the airfoils.

I remember an article in Pop Sci or Scientific American forever ago about stepped airfoils and someone wanting to test it on full scale aircraft, claiming they were unstallable.

My man… go easy on the adderall :)

impressive, thank you!

Just one doubt , was the cg adjusted for each model cause you need to trum it beforehand as not all airfoils have their aerodynamic center at the same place. As i noticed in the video the ppane was literally goibg down ( it's clearly nose heavy ) adjust it by using a ballast weight or by changing the main wing position a little forward. And do the test again.