KF Airfoils 101 - Introduction and Preliminary CFD Research

[@vet137]

I am new at RC and just started building a BLUEBABY via my needle cutter cnc and the one thing that caught my fascination was this KFM2 and actually all of it. Great Video!!

[@HotelPapa100]

Props for pointing out what the reasons may be for using a KF airfoil. Many just rave about it without going into specifics. Now for some critique: Comparing random geometric/velocity working points does not really give a valid comparison. As you certainly know, airspeed and lift are directly linked, so it only makes sense to compare points of equal lift. To get the whole picture you have to compare complete polars. And the singular of vortices is vortex. You may want to look into the x-foil digital wind tunnel. I'm not sure how well it will do witth the KF airfoils, most such simulations don't do well with separated flow. x-foil can deal with low re separation bubbles, but the explicitly exclude fully separated flow. don't know how KF fits into this scenario.

[@nin_gamerrenatobfa9759]

Dude, this video as awesome, but you have to make Part 2 with those simulations you were talking about, diference in stall etc... Really looking foward to that. Cheers

[@ColtonCampbell]

Thanks man, appreciated! I hope to someday have time to dive into this again 🙃

[@spencerbookman2523]

Speaking of step location, I just watched another channel recommend putting the step at 40% of chord, although they also said it wasn't necessary to be precise. Also, throwing ease of construction out the window, I wonder if making the top of the airfoil behind the step, and/or the step itself, a concave surface would better support vortex formation/stability.

[@matthewbates6301]

Mate, I just randomly stumbled across your videos, but this a brilliant! You would honestly be a great teacher :) I hope you keep making these.

[@kenrobba5831]

Liked the approach, answered several questions I had about the KF aerofoils; look forward to stall analysis.

[@Triple_J.1]

Since the availability of xFoil there is almost no reason to use these airfoils except for very crude models. An inverse designed airfoil will outperform experimental forms in every case. Even a flat plate works well for 3D foamies. And it is very easy to hotwire true airfoil shapes out of XPS styrofoam. Mark Drela has several low Reynolds number airfoils available. As does Selig in his reports titled same. Edit* Clark-Y is a terrible airfoil for almost any use. It has a sharp stall, large negative pitching moment, average maximum lift, and terrible low Reynolds number performance. - If you want a similar archaic airfoil with better performance you are probably better off with a 4412. Or a 4409 for low Reynolds number models. Otherwise, thin Drela or Selig foils.

[@nevillecreativitymentor]

Great video 2024 BUMP 💪 I am an old timer aeromodeller who came into aeromodelling building Balsa Chuck Gliders and then of course moved on to FF,CL, RC and so on and now at Drones. I am also working with kids to ring them into the fold of Aviation (any form for goodness sake LOL) In light of that I am creating a simple simon chuck glider to be made from Kebab Skewers and Foam Plates. Did not want to make errr "complex" airfoil shapes ... so was looking more into Kf ! I think your video gave me that extra nudge I needed to do it. (I was holding back for a long long time) So cheers and I wonder where you are now since 5 years of this video !!?

[@WynnofThule]

Do you think these would work well for cheap STOL aircraft?

[@hansleatherby1032]

Excellent video - very interesting subject look forward to more

[@learningtocrash4030]

I've tried a couple different KF style wings with good results. I think my favorite was my FT Flyer. I wonder what would happen if you put serrations across the top of the step. Kind of like VGs, just cut into the upper piece.

[@ColtonCampbell]

That's an excellent idea! I will add that to my list of things to research

[@杵渕亮子]

I have had the same idea for stepfoil withaut to know about these video...

[@indepviewpt]

Thanks for the explanation.

[@vladimirpetkov1959]

Great channel, i am new to aerodynamics, CFD and F360 but still your video is very useful. Are you using the paid CFD program from Autodesk?

[@pachosanchez1405]

Hi Colton, Which software do you use to simulation?, Thanks

[@buensomeritano1755]

How do KF foils perform as hydrofoils?

[@ianmathieson65]

Should do well. Stepped floats on seaplanes develop less drag than plane floats for the same reason that KF airfoils result in less drag - the vortex. Minimising drag in the water is important on a seaplane to help it take off without having to provide lots more power and hence more weight.

[@buensomeritano1755]

@@ianmathieson65 no. I mean as a submerged hydrofoil.

[@ianmathieson65]

@@buensomeritano1755 Yes, I realised that. I was drawing a parallel between the trapped vortex which is characteristic of a KF aerofoil completely surrounded by air, and the same completely surrounded by water as on a hydrofoil. Air and water are both fluids. Sorry if I confused you by talking about floats on seaplanes, but the comparison still holds as long as the lower part of the float is below the water surface which it is as the aircraft accelerates from rest until it lifts sufficiently as it takes off. The stepped float would behave in the same manner as a stepped submerged hydrofoil where the trapped vortex reduces drag in both cases. Which is why I believe a stepped hydrofoil would result inn greater speed for the same thrust than a non-stepped hydrofoil, and hence greater lift as a result of the greater speed.

[@buensomeritano1755]

@@ianmathieson65 I'm just curious if a submerged stepped foil performs as well as a stepped airfoil, because, water is not compressible and air is.

[@sibujacob977]

Can you please share the KFM airfoil .dat file . thanks in advance

[@alcourtines4707]

I don't see it in nature. Good enough reason for me to move on.

[@reallynotrob4897]

Pls make the video

[@ahmadzaimuddinafif9517]

Great !

[@ColtonCampbell]

Thanks I appreciate it!

[@葛葛-v2x]

たくさん話し

[@alf3071]

your step size is way too high

[@GemstoneActual]

PaDents are pretty imporDent, right? I know you can say "but", bud. Americans DGAF.