Slotted Flaps for several RC aircraft

[@vg23air]

nice video, the fowler introduces one thing no other flap does, an extension of the length of the root cord with no deflection of the flap itself, for takeoff, in effect, a longer wing chord with no drag,

[@bradruffalo]

Neal, thank you for sharing this video that includes the essential physics necessary for relatively simple and efficient enhanced lift devices. Always fascinated! Brad R. Vancouver, WA, USA

[@aerobyrdable]

Hey there, Neal! Just felt like letting you know: I'm in the process of developing my own part 103 ultralight, which I hope to build for real someday. Your video, and the NACA link, was a great resource when it came time to design the flaps :)

[@nealmontgomery1307]

Awesome! Glad the info was helpful. The old NACA research is still relevant indeed

[@forestbraylen2758]

i realize it is quite off topic but does anyone know of a good place to stream new movies online ?

[@walkeremilio6008]

@Anders Ramon Definitely, I've been watching on FlixZone for since april myself =)

[@forestbraylen2758]

@Anders Ramon thank you, I signed up and it seems like a nice service :) I really appreciate it!!

[@andersramon4207]

@Forest Braylen no problem xD

[@kaboom-zf2bl]

wow someone who spells Neal correctly LOL ... nice video ... been looking for what the gap measurement is for these flaps ... now I know ...

[@looneytunes47]

Slotted Flaps are less likely to Baloon the plane as well which elinimates the need for down elevator mixing

[@parsecpres]

Hello all! I would like some feedback, please. Too Long/Too short? Irrelevant content? No sound/explanations? What? THX

[@BrianPhillipsRC]

I thought maybe I'd gone deaf... I want to see the last one flying. I bet it balloons like crazy! It's a Kadet Senior, right?

[@parsecpres]

Brian Phillips Yes sir, it certainly is a Kadet Senior! I thought it may be prone to pitching up as well, but it does so only minimally. When the flaps are deployed to around 40 degrees (a bit less than the maximum throw you see at the end) you only need a small trim adjustment when established on the approach power setting. The big Sig will settle into a beautiful, slightly nose high approach attitude with only a small pull for the flare and touchdown. Full flap will give you a great speed-controlled steep approach, requiring only a brief touch of power for transition to flare and touchdown. It slows down in a hurry without it. It’s great fun

[@BrianPhillipsRC]

I bet it flies like a daydream!

[@Cowcharge]

Your video was exactlly what I was looking for. Personally I find it refreshing to have a video without, first of all, the stupid electronic 'dance' music everyone puts on their videos (and louder than the damned dialogue). By the second 'verse' of those beep-boop, mindlessly repetitive non-musical crap tunes I'm ready to commit self-murder. And secondly, you gave us a good look at the slot, and the math needed, without saying a word. I'd call that the epitome of efficiency, and it is to be congratulated in these days of every knob thinking he's fascinating, and the next pewdiepie. The only thing I'd ask for is maybe a better look at the shape of the slot, viewed from square-on to the end of the flap. You could show us from inboard by taking the wing off, or from outboard by removing an aileron... Just a thought, but thanks for the video, it was just what I was looking for.

[@parsecpres]

Cowcharge thank you for the compliments. I would be happy to show you a side-view profile, but I think an even better view is in the TR 664 itself. If you visit the link shown in the video’s description and open the Technical Report, there is a very good depiction of what I have tried to duplicate when you examine Fig 5, slot arrangement 2-h. All the dimensions, radii, planform profiles are there. Nevertheless I will try to meet your request in the near future (I am currently out of the US but will be home the first day of Spring 2018)

[@R.B_B]

Great video! Does anyone know if they are to buy hinges for Sloted flaps?

[@sonnyburnett8725]

Some F4U Corsair models have nice slotted flap set ups. When added to the bent wing it makes for a very nice looking flap design. IMHO.

[@mpikas]

Everyone seems to make a big deal about hinging these things, which doesn't seem all that difficult once you figure out that you just need to move the hinge point downward. What I can't seem to figure out is how to cut them nicely out of foam wings? If they where full length then something like hotwire would work, but I don't see a good/easy way to do that. How are you cutting yours out? Other ideas?

[@parsecpres]

Mark, I use a simple snap-off blade (the nicer ones with the metal blade-guide insert, not the cheaper all-plastic ones...find them at your local hardware store...a tad pricier, but worth it...don't forget extra blades)and some sort of straightedge guide. Work with a newly snapped off point and work your way down into the foam over the course of several or more cuts. If the foam starts to tear, snap off a new point and continue. It may be a good idea to cut your flap 1/4" (6mm) short chordwise so you can use 1/4" X (whatever height is needed) balsa stock to reinforce the flap's leading edge (LE) to prevent its flexing. The balsa leading edge also makes it easier to create a nice leading edge profile. keep in mind you will need to thin down the cambered (upper) side of the flap to ensure if fits nicely under the wing's upper surface Trailing Edge Extension. See the detailed drawings of the flap cove profile (fig. 5) in the Technical Report 664 link In the description section above, and you will see how to fabricate the overhang for the flap to nest under as well as how to profile the Slot Entry on the lower surface of the wing. As you note, the hinge point placement is indeed important, but quite more so than people might think. Not only must the hinge pivot be located correctly below the wing but it MUST be located correctly fore/aft. Small variations in the hinge pivot location make a huge difference in the flap deployment geometry. Mock-ups and experimentation of differing pivot locations I have made bear this fact out. At 40 degrees flap deflection, the slot gap (distance between the Slot Lip Extension and the surface of the flap should be .023% of the original wing chord, (i.e before you cut out the flap) with the LE of the flap just forward of the aft edge of the Slot Lip Extension. These two dimensions, if adhered to carefully, will increase the effectiveness of the slot performance and thus your flap system's performance. Perhaps it may be wise to use slow-setting epoxy to guarantee that your hinge point placement provides for the above two values. As the epoxy cures you can tweak the flap hinge and flap mounts to get the right combination of deflection, gap, and flap LE just in front the slot lip extension. More than you asked for but it's all important. Thanks for the question!

[@parsecpres]

Mark, is your flaps modification finished yet? If so, how dd it go?

[@mpikas]

Sort of. I ended up cutting out a hot wire foam/paper coverd wing to experiment with that will work an existing fuselage, but the project is temporarily stalled a little further than documented here: www.rcgroups.com/forums/showthread.php?3032015-Another-Moded-Super-Cub-was-How-Do-I-Deal-With-the-Details-Paper-Covered-Foam-Wing (there is also a link in that thread to a flap discussion with a lot of geometry testing I did in CAD)

[@seanmolloy9422]

great footage clearly shows hinge and pivots. thx

[@vg23air]

do flaps work for small rc, yes, i added them to a p51 years ago and it really tamed the landings and stopped a lot of high speed gear damage. the design was simple, i just cut the trailing edge and added hinges and a servo, nothing fancy.

[@stvrob6320]

Thanks for posting this. I was thinking you needed special hinges to drop the pivot point down, but I see you have used regular robart hinges and a little bit of wood to do the same. Any guidlines for how far to drop the pivot point? Say as a percent of flap size? Im just drawing out on paper what looks right, but really I dont know.

[@parsecpres]

Steve Roberti there is a link to the TR 664 in the description. Examine figure 29. “Path of flap nose...in percent airfoil chord.” At 40degrees deflection, the flap nose should be 2.43% of the wing/flap chord below the slot lip (c * .0243) which is the y coordinate, and 1.43% if the original wing/ flap chord in front (slightly forward of and under) of the aft edge of the slot lip (c * .0143). The new flap/wing chord should be identical to the old wing chord if the flaps have been fabricated according to TR 664. The flap should not deploy beyond the aft edge of the lip, it should always be slightly below and under the slot lip extension. On a model, it is not a large gap, but it is important to have the flap meet these dimensions at 40 degrees deflection. As a starting point to locate my flap hinge pin (this is where I start to actually answer your question), I used the dimension from figure 5 on pg 4. I started with the hinge pin at .8081c back from the leading edge of the wing and .0475c down from the chord line of the flap/wing (the flap should line up with the wing chord line at 0 degrees deflection). I constructed a profile of the flap cove and a profile of the flap profile from heavy card stock and made a big square tab which would act as the flap hinge locator. I drew a grid to keep track of the locations. I secured the two profiles to the table and used a t-pin to act as the hinge pin. I began to move the flap with different t-pin locations or get the above results of x and y coordinates. The flap movements are remarkably different if the pin location is off by even a little. When zeroed in on the correct pin location, I recorded these measurements carefully and installed my hinge pin (robart hinge) precisely where it should go. I used 5 min epoxy to make sure I had enough time to verify the slot gap distance (c * .0243) with a piece of balsa cut to that exact thickness. The slot and flap profile models using card stock really does help. Hope this answers your question. Sorry for the delay in the response. Good luck

[@creativitytools4576]

I have a qsn what is the general flap to wing ratio of an aeroplane ?

[@andy1514-g1q]

thanks, great video - explains the geometry & design very well. nicely built models too. :)

[@coriscotupi]

Great and inspiring video, thanks for posting. Here is what I have always wondered and have never, ever read or heard any answer for: Will slotted flaps and/or leading edge slots or slats have any measurable impact at RC model Reynolds Numbers? In our aircraft size and speed, would the slot gaps be inside the boundary layer anyway, with little to no air movement through such gaps? The PDF you pointed to, and I downloaded, mentions RN in the order of millions, considerably higher than that of the typical RC model. I wonder if here is any quantitative study of such devices on RC-size wings.

[@parsecpres]

corisco tupi I had the same questions when I built my first slotted flap mod many years ago. I saw a paper by Dr. Leland Nicolas (Illinois Institute of Technology) who summarizes Reynolds Number in RC as a way to describe the boundary layer on a wing. RC’s have a laminar boundary layer and full scale aircraft have a more turbulent boundary layer and thus more maximum lift coefficient. The first part of the video shows the modeled wing sections in the smoke tufts. The air seemed to be channeling through the slot without any large divergence from what their later larger-scale tests showed .The question for me then, was will the flaps be nearly as effective as I hoped? Indeed there were and still are. Are they as effective as a full scale aircraft’s flaps? I have nothing to compare to unless I had an exact scale model and compared the performance to the full scale counterpart. For the models I have, though, there is a distinct difference between flapped and non-flapped landings. The TR you downloaded will give you much info to execute your own design for your airplane. Good luck and thanks for the kind words!

[@coriscotupi]

+Neal Montgomery Thanks for replying. One issue might well be that contrary to full-size airplanes, we don't really have very accurate airspeed or AoA control on take-offs, approaches and landings, so we really can't fully assess to which extent a slotted (or indeed Fowler) flap is effective as opposed to simpler flaps in RC applications. Perhaps those Pitot-equipped flight control boards (Ardupilot, etc) with real-time data links could come in handy for such experiments, so one could determine optimum approach speeds, etc for a real-world model and then get consistent results with that model at closely-monitored airspeed and AoA. Interesting stuff. Thanks again for posting.

[@aeromodellismodinamicoaere3829]

Very good a really nice job ! 👍👍👍

[@parsecpres]

Aeromodellismo dinamico Aerei RC thank you very much!

[@hafizhafiz1609]

nice ..what's the name this parts

[@parsecpres]

HAFIZ...the parts have been made from the trailing edge sections of the wings which were already there. I cut out the sections of the Trailing edge and made flaps from those sections. I had to add material to most of the flaps to make them fit the existing wing structure. I am in the process of making a video of how I did this. I'm sorry that I don't understand your question exactly, but send me a reply and I hope we can make it a bit more clear.

[@johnnyllooddte3415]

do you sell these parts

[@parsecpres]

Johnny, wish I could respond in the affirmative, but these are all custom parts. There are several hinge pylon designs as well. The pylons are mostly hard balsa but one is laminated thin ply. I used the Robart hinge points for all the hinges. Wish I had better news, sorry

[@citroends7308]

Cool video, better with sound but still nice

[@parsecpres]

did not want to put in some lame-ass music, nor would you have wanted to hear me perform my impression of MC Mumbles! LOL

[@umontakahashi9528]

Good video, just stop shaking the camera and show in more detail. Thanks

[@parsecpres]

umon takahashi I’m a tad old. The detail can be found in the Technical Report. It is free and does not cost anything. Same with manners

[@MrHello545]

Yeah man, old sages tend to shake just a bit when they dole out wisdom from on high

[@umontakahashi9528]

@@parsecpres sorry, was not my intention to offend you. Just wanted to see the detail. Regards

[@parsecpres]

umon takahashi I apologize for taking offense and replying with an insult. Growing old is mandatory, growing up is optional. Not digging the growing old part. I hope your attempts to fashion these flaps has gone well. Post an update!

[@umontakahashi9528]

@@parsecpres Don't worry. It's a matter of gentlemen to apologize. And you are a gentleman. As soon as I will use those flaps for sure I will let you know. Best regards!

[@beaclaster]

Yea biplane is cool