Best STOL Wing Design Ever?!?

this video is sponsored by squarespace back in the early days of aviation hanley page and his aircraft company had the idea that splitting up an airfoil into multiple elements would ultimately allow it to create more lift since then this has proven to be true and it's why slotted flaps and leading edge slats are commonly used in many of today's modern aircraft leading edge slats mainly come in handy when a plane is flying at high angles of attack if the angle of attack of any given wing gets too high the air flowing over the top will separate away from the surface and become turbulent this causes the wing to stall and fall out of the sky leading edge slats help redirect the air so that it stays attached to the wing for longer increasing the angle of attack at which it can fly without stalling slotted flaps are basically just improved versions of normal flaps they increase the amount of air that the wing pushes down and in turn increase its lift the detached section of a slotted flap helps airflow over the top surface of the flap without separating this allows you to use a steeper flap angle and generate more lift airliners use multiple slotted flaps to really take advantage of this phenomenon handley page really took this concept to the extremes with this eight element airfoil that he estimated to have a coefficient of lift of 4.33 which is insanely high here's a little chart from nasa that gives you an idea of what sorts of coefficients of lift you can expect from other airfoils the one at the very top has a leading edge slat two slotted flaps and a boundary layer suction device at the top and its coefficient of lift is still below four a much more practical design but it still falls pretty far short of hanley's eight element wing with a coefficient of lift of 4.33 so in theory this wing can generate a huge amount of lift compared to other wings of similar sizes and that are flying at similar speeds in this diagram the airfoil is shown at a 42 degree angle of attack which is the angle for maximum lift any single element airfoil would definitely stall at such an insanely high angle other than an ultra high coefficient of lift this airfoil really doesn't have much else going for it especially at such a high angle of attack it would surely create a ton of drag and it would have a strong pitching moment any airplane built with this wing flying at this angle of attack would almost certainly have some terrible flight characteristics it might however be much more practical if you significantly lower the angle of incidence the youtubers sam shepard and bailey harris both built multi-element wings that they flew at lower angles of incidents and these seems to work pretty well the stall characteristics and slow flight performance seemed to be improved quite a bit however to really hit the high coefficients of lift that these wings are capable of they need to be used at an ultra high angle of attack like handily paige showed here i thought it would be interesting to build an airplane that utilized such a wing and had it mounted at a steep angle for maximum lift just to see what the flight characteristics were like if it flew at all this is the design i settled on it's kind of like a mix between a triplane and a plane with multiple slotted flaps the first wing has a 5 degree angle of incidence which is on the steeper side of normal the second wing is at 16 degrees and the third wing is at 29 degrees if we look at the data from the airfoil i'm using we can see that the lift kind of starts to flake out above 10 degrees which is probably around where it starts to stall but hopefully with my design the upper wings will help redirect air downwards over the lower wings to keep it from stalling out even at crazy angles like 29 degrees if i were to have built these wings without any twist the tip stall characteristics probably would have been horrendous and they probably would have created some serious wingtip vortexes which would have made them even less efficient than they already are so to mitigate this i gave each wing enough twist so that the angle of incidence at each wing tip is zero i also staggered the wingspans in an attempt to spread out the vortexes a bit more and keep the majority of the lift in closer to the center line i knew the pitching moment was going to be pretty wonky on this wing so that's why i made the horizontal stabilizer really big and mounted it really far back away from the wing i cut all the foam parts for this plane with my new stepcraft m1000 cnc router this is xps insulation foam i really like this stuff because it doesn't break apart as easily as styrofoam and has pretty good structural rigidity all the parts are done as a two-sided milling operation so after cutting the first side i flip the foam over and make sure it's aligned with the pins that i put in the work surface then i clamp it down and start on the other side after the cnc machine is done i trim the wings out of the stock here's the airfoil profile left in the stock you can see that it's very nice here are some shots of machining the lower wing there's no way a four axis hot wire would be able to cut a wing with so much twist especially since all the twist is in the outer third of the wing here the machine is cutting the two top wing halves and one side of the fuselage and then with the next setup i did the other side of the fuselage and the horizontal and vertical stabilizers so after all the cnc machining was done i sanded down the parts to remove any imperfections the horizontal stabilizers ended up being way thinner and flimsier than i expected so i ended up covering it in a layer of fiberglass in hindsight i probably should have just re-cut a thicker one and not fiberglassed it but oh well so i started by painting on resin and then i added a little bit of carbon to for some extra stiffness i'm using lightweight kevlar fabric on the elevon hinges and yes i'm adding elevons to the horizontal stabilizer because it's easier than adding ailerons to these funky wings we'll see if it works then came a layer of two ounce glass and some peel ply over that i stuck it into the vacuum bag and let the epoxy cure or at least partially cure i got a little too excited and started removing the peel ply before the epoxy had become fully rigid this caused the foam and fiberglass to bend in a few spots to try and reset the epoxy in these areas i heated it up with a heat gun and i do think that helped repair the epoxy a little bit but also melted some of the foam underneath so then i had to do a little patchwork with some spackle i mixed some goop glue in so that it would not crack so easily if it flexes at all after that dried i sanded it down and ended up with this not pretty but at least it's super smooth next it was time for the elevon hinges so i used the dull side of a razor blade to score the epoxy then i used my dremel to cut the inside edges and to cut away the fiberglass on the inside part where it would need to be beveled then i cut that bevel into the foam with a razor and worked the hinges free to break up the epoxy that was inside the kevlar to make it flexible next up came the fuselage i installed my flight controller a dragon link 900 megahertz receiver and a gps on the inside and then glued the two halves together i cut in some doors and made hinges with packing tape to access the inside of the fuselage after that came gluing on the horizontal and vertical stabilizers for this build i'm using two hs 5055 mg servos for the elevons that i installed in the back section of the fuselage now back to the wings after machining and sanding the surface of the foam gets kind of fluffy so to smooth this out i applied a layer of polycrylic after that dries i lightly sanded it down with some 150 grit sandpaper that gives it a smoother surface and also a bit more durability than the raw foam i 3d printed this wing holder that the foam slips right into it's so satisfying when your parts just line up perfectly so that left me with this awesome wing assembly that i was super stoked with definitely not quite as aggressive as the 8 element wing but that would have taken much longer to build and this one probably also has a much better chance of actually flying so then i glued the side panels onto the fuselage stuck the wings on there and i also added two motors to the front so that just about sums up the build for the first flight i flew it without the two lower wings attached the reason i have this camera way out in the front is because the tail ended up being heavier than i had planned so i needed the weight way out in the front to get the cg right all in all it flew pretty well and the whole elevon on the tail thing seems to work out okay with one wing its cruise speed was around 23 miles per hour or 10.5 meters per second so then i added the two lower wings and after a bit of finagling i got it flying pretty well [Laughter] oh it's so tail heavy tape this sucker right on there even with the extra nose weight that i had to add the cruise speed went down to 14 miles per hour or 6.3 meters per second that's roughly 9.5 miles per hour slower than with only one wing pretty impressive the stall speed was about nine miles per hour the crazy part is the stall characteristics were very mellow it really wouldn't tip stall at all which is incredible it would just kind of fall straight down probably thanks to the zero angle of attack on the wingtips [Music] so after that i took the camera off the front and replaced it with the flight battery to get the cg right this took the total weight down to 2 pounds or 907 grams at this weight the cruise speed went down to 5.6 meters per second or 12.5 miles per hour that's pretty impressive for a two-pound plane with a wing loading of one pound per square foot that's with projected wing area by the way not combined wing area of each individual element this plane could be a lot lighter too i've got some pretty heavy electronics in there and the fiberglass tail does not help now i'm wishing i would have made it as light as possible for ultra slow flight so the flight characteristics are good but that's not to say this is some sort of revelation in aviation technology or anything like that all in all it flew very poorly compared to a normal airplane the pitch axis was pretty unstable and increasing the throttle too much would cause it to nosedive the elevons on the tail did not work as well with the two lower wings installed and sometimes the roll axis would get a little wonky a few times i accidentally took off without the flight controller stabilization turned on and those flights didn't last long despite all that it still flew well enough for audio pilot to be able to do a waypoint mission so i let it fly itself around while i got some video clips of it so i'm just sitting here filming the plane and it's doing its own thing in auto mode just flying the circuit around the field hi i have the altitude set to two meters so [Music] next up i glued the landing gear back on and did some takeoffs and landings normally when a plane takes off the front wheel comes off the ground first but a few times with this plane the rear wheel picked up first and then it just kind of rode a nose wheelie for a while before lifting up pretty awesome this would mostly only happen when i would use a lot of throttle on takeoff since throttle causes it to pitch down [Music] the next day i put a dji fpv camera on the top along with an insta360 go camera so let's see how this thing does with proximity fpv [Music] um [Music] it's definitely no race quad but it's still pretty fun to fly fpv with a really slow airplane the next day i put the plane into auto mode so it would fly itself while i got some air-to-air shots of it the problem here is that i switched from a 2s battery to a 4s battery and although i did reduce the maximum pwm for the throttle and rdu pilot i did not reduce it enough and the flight controller certainly didn't know that raising the throttle would cause it to pitch down so then the plane went crazy and eventually ended up in the top of a giant cedar tree [Music] sounds like the prop broke off [Music] i'm so lucky so i was wiggling the throttle and i kind of got it to start oscillating it broke free yay oh i thought i was gonna have to do some crazy big drone recovery mission with another drone but it came out that's lovely after that i pieced some of the wings back together and glued it onto a stick that i clamped onto the stool samples steering wheel this was so that i could move the wing back and forth through a consistent path and film the downwash with the help of a fog machine and a line laser the air suddenly becomes visible you just have to not let the fog mixed with the air around it too much because then there's no contrast and you can't see anything so this is a comparison of all three wings versus just one wing no surprises here three wings definitely push more air downwards it would have been really interesting to see a comparison of a multi-element wing with no twist and one width twist like mine that might allow you to see a difference in the wingtip vortexes which would be cool but building that would have been a lot more work so i didn't do it so all in all this was a really fun concept to tinker around with and i think ultra aggressive multi-element wings like this might actually be sort of practical for short takeoff and landing aircraft if you can manage to control them well enough i'm sure big ailerons would have worked a lot better than my elevons or maybe even little thruster motors for pitch and roll control there's lots of interesting ideas to try with slow flight mechanisms but that's all for this video a few weeks ago i posted the snow cat up on rctestflight.com for pre-order the whole batch sold out in less than a week i couldn't believe it you can now pre-order a kit from the second batch but that will likely not ship until late winter or early spring it's definitely a bit intimidating to have all these orders piling up but luckily i'm using squarespace and their ecommerce tools so processing all these orders will be just about as easy as it gets i also used squarespace to build the website and it's definitely my preferred website building platform of choice i've been using squarespace for several years now and i can honestly say it's the best website building tool out there squarespace gives people a powerful and beautiful online platform from which to create their website their powerful ecommerce tools make adding products tracking inventory and managing orders super easy squarespace extensions make it easy for me to connect third party shipping and order fulfillment services to streamline the logistics this is going to be a huge help for the snow cap project let's just hope i can fit all the parts in my house for bloggers creating a community on your squarespace website is easy with a fully integrated commenting system that supports threaded comments replies and likes use their powerful blogging tools to categorize share and schedule your posts too automatically push website content to your favorite social media channels so your followers can share it too check out rctestflight.com to see my squarespace website and for your own website go to squarespace.com for a free trial and when you're ready to launch go to squarespace.com rc test flight to save 10 off your first purchase of a website or domain thanks again to squarespace for sponsoring this video but that's all for this video thanks for watching bye

Channel: rctestflight

Views: 2,963,288

Keywords: aviation, rc airplane, foam airplane, drone, fpv, aerodynamics, multi element wing, element, split flaps

Id: Rc7PcmAl7Ag

Length: 16min 2sec (962 seconds)

Published: Sat Jan 22 2022