Can a Solid Wood Airplane Actually Fly???

this video is sponsored by Magic spoon cereal in my opinion one of the fascinating things about airplanes is that they can be passively stable this means they can fly straight and level without any moving Parts an example of this is a well-constructed paper airplane which can glide on a straight and level flight path without any external guidance of course there's no way for it to passively course correct against external disturbances like wind but in theory a perfectly symmetrical paper airplane would fly perfectly straight and level if it were in perfectly calm air in this video I will attempt to CNC machine a solid block of wood into an airplane that has passive aerodynamic stability and then I'll see if it can actually fly despite having an abnormally High Wing loading for a plane of its size before we start cutting let's take a look at what makes a properly designed airplane passively stable we're going to look at each of the three axes of rotation separately first up is the yaw axis and it's probably the simplest it works just like a Weathervane the side with the most drag will get blown downwind vertical stabilizers are added to the back of the aircraft so that the tail gets along lined with the oncoming wind the biggest difference here is that a Weather Vein rotates around an axle whereas an airplane rotates around the center of gravity so that's it for yaw the roll axis is next passive roll stability comes from what's called dihedral dihedral is where the wings are angled inward slightly so that the wing has a slight v-shape to it to illustrate how it works I made this model in onshape this airplane has a very exaggerated dihedral angle and a steep angle of incidence angle of incidence is how the airfoil is tilted upwards relative to the rest of the plane so let's say we're flying a long straight and level and our lift is equal to our weight then all of a sudden we get hit by a gust of wind that blows the plane over at an angle now our lift and weight are no longer directly opposing each other this imbalance of force creates a new net force that pulls the aircraft off to the side this is called a side slip as the aircraft starts to slip to the side the direction of the oncoming air is now hitting the plane at a bit of an angle this is where the dihedral comes in now let's pretend that the camera is looking at the plane at the exact angle of the oncoming there so we are the oncoming air in this case now the plane goes into a side slip and the oncoming air changes angle whoa look at how different each side of the wing suddenly looks relative to us as the oncoming air this side of the wing now has a much steeper angle of attack than the other side of the wing see how the airfoil profile is angled up more here that makes the lower wing generate more lift than the upper Wing which brings it back to level how neat is that as I yaw the plane back and forth you can more clearly see how the angle of attack is changing one interesting thing to think about is how the vertical stabilizer is there to try and prevent this side slope motion so that means a smaller vertical stabilizer would actually allow more side slip and make dihedral more effective in correcting roll pretty interesting next up comes the pitch axis pitch stability comes from the angle between the wing and the horizontal stabilizer if the horizontal stabilizer has a negative angle of attack relative to the wing the plane will have a natural tendency to want to pitch up this is because the wing is lifting up in the front and the tail is pushing down in the back due to their respective angles of attack this is easier to visualize if you think about it like a car if the wheels have an angle relative to each other it will turn same with the plane if the wing and the tail each have an angle relative to each other it will turn up or pitch up the thing with the plane is that the amount of pitching up Force you get depends on your air speed So the faster you go the harder it's going to want to pitch up so if this angle is present in all stable aircraft then why don't they only ever want to pitch up well it's because the center of pressure is behind the center of gravity you can think of the center of pressure as a sort of focal point of the lift that the aircraft generates if you balance the planes that the center of gravity is in front of that it will make the plane want to pitch down due to gravity so now we have an aerodynamic course trying to make the plane pitch up and at gravity trying to make the plane pitch down and the one thing that controls the balance between these two forces is air speed and what controls the air speed of a glider the Glide angle too Steep and it will go really fast too shallow and it will go too slow and stall here's the magic part if the Glide angle is too steep we will build up too much AirSpeed and the aerodynamic pitching forces will outweigh the gravitational forces and this will cause the plane to pitch up if the Glide slope becomes too shallow the plane will slow down and the aerodynamic pitching force will lessen this makes gravity the dominant force and the plane pitches down it's a self-stabilizing feedback loop if our plane has too much of an angle between the wing and the horizontal stabilizer it will oscillate like this if there isn't enough angle it will just be unstable in nosedive if the angle is just right the plane will settle on a smooth Glide slope so that's the basics of passive aircraft's stability now it's time to model our plane I stole the fuselage shape off a cad model of a DC3 that I found online and made the wing entail myself the angle of the horizontal stabilizer is at zero degrees relative to the fuselage the wing root has a 2.5 degree angle of incidence this is where our lift will come from the wing tip on the other hand has a very slight angle of incidence at only one degree so why make the wing have a little bit of twist like this there are two reasons first the wing root should in theory stall before the wing tip since it has a steeper angle of attack this is good because anything is better than a tip stall a root stall will make the plane nose down nice and flat but a tip stall will make the plane dip off to one side and potentially go into a death spiral the other reason for Twist is that it makes the root do more of the lifting work than the tips this minimizes the strength of the wingtip vortexes and increases efficiency okay enough with all the science it's finally time to start cutting wood these are the solid blocks of wood that I'm going to turn into airplanes step one is to use this surfacing bit on my stepcraft m1000 to plane down one side of the board this way it will be a uniform thickness throughout around to this time snotmaker had sent me their 3D printer slash laser cutter and engraver CNC machine to try out I figured this project would be a good torture test for the CNC functionality so I took off the laser and popped on the CNC tool head when you change functions you also need to switch out the workbed so I installed the MDF wasteboard that it comes with I'm using these steel pegs to interface with the wood block they slide into the holes drilled all the way through the wood this way when I flip the work piece over to machine the other side it will stay perfectly centered I also bolted it down to hold it in place finally it's time to start cutting [Music] oh goodness that sounds pretty bad this is only a 50 watt spindle which is not really made for hogging out Big Blocks of wood like this it's more for light duty cutting and Engraving for arts and crafts and stuff like that but I thought it would be interesting to see if it can pull it off the downside to having a weaker spindle is that you can't cut as deep and as fast as you would be able to with a more powerful one this just means it's going to take a lot longer to cut I think this plane took about 18 hours of Machining or something like that I could have done it a lot faster on my step craft but I wanted to try the snapmaker out the machine is inside of the enclosure that snapmaker provided and I started noticing all these crazy patterns on the acrylic panels I'm assuming these are all caused by static electricity causing the dust to stick but it's amazing how different all these shapes are they look like everything from zigzags to ice crystals to mushrooms apparently they can be caused by air currents material irregularities surface contaminants and all sorts of other stuff like that pretty interesting after the bulk clearing operation it was time for the surfacing finish operation for the this I'm using a parallel tool path that just goes back and forth and removes a little bit of material on each pass this is what really defines the final shape after that was done I vacuumed it off and this is what it looked like not bad I'd say next it was time to flip it over using the indexing pins to make sure it stayed perfectly centered this side was more difficult because more wood needed to be removed due to the wings dihedral angle after hours and hours of Machining tragedy struck I'm not exactly sure why but the horizontal stabilizer split in half could have been from impurities in the wood or it wasn't well enough constrained or something like that so then I tried again the second time the top half came out well and then miraculously the bottom half did as well it wasn't perfect but hopefully it was good enough to fly but do you know what is definitely good enough to fly fly into my mouth that is it's magic spoon cereal which is the sponsor of this video magic spoon has reinvented cereal making it with more protein than ever and zero grams of sugar it's also grain free making it perfect for those living on a low-carb lifestyle each serving is packed with a generous 13 to 14 grams of protein and a mere four to five grams of net carbs while delightfully retaining the nostalgic flavors of your favorite childhood 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sanding to get rid of all the little Machining cusps and smooth everything out I had to be careful not to sand off too much material because then it would have altered the aerodynamics but this is how it turned out looks pretty good if you ask me nice and soft nice and smooth it's just missing one thing and that is the vertical stabilizer to make that I converted the snap maker back into a laser cutter and cut it out of 8 inch plywood that just slots right into the plane all done look at that so amazing so precise so representative of the cad model the angles of incidents were accurate the dihedral angle was accurate the airfoil profile was accurate had reasonably sharp trailing edges I was pretty happy with how it turned out so now I had to figure out where the center of gravity should be throwing it by hand the Glide past wasn't going to work since this thing is relatively heavy and I was going to need a ton of AirSpeed to actually fly spinning it in circles with a string actually sort of worked and I was able to add weight and sort of figure out where the center of gravity roughly should be it was at this point that I realized that it would be smart to 3D print some identical models of this plane and use those for CG testing so that I wouldn't need to risk my precious wooden model I figured out how to print them with solid infill on the nose so that the plane would balance in the correct spot I made several models all with the CG in slightly different locations for comparison I used a bungee cord to launch these things since they have a super high Wing loading for their size and would need a lot of AirSpeed to fly oh not so good although they did seem to be flying a bit the performance was not amazing it did a Loopsy Loop probably do so the low Reynolds number and high Wing loading I printed some more variations with angle of attack adjustments and even different air boil profiles so I loaded up my backpacking and rode to the park on my new Varla Eagle One Pro electric scooter I know I know another product plug but can you really expect me to have the willpower to turn down a free two kilowatt full suspension scooter I mean come on put in all seriousness I've got to say I don't think I ever would have bought this thing if they hadn't sent it to me but now that I have it I can't imagine going back to life without a small electric vehicle it's super convenient to get around town quick especially in a more urban area and now that I have it I put way less miles on my truck the top speed is 40 miles an hour and the range is like 30 or 40 miles so it's super practical there's a link in the description if you're interested so I made a few modifications to the design and one of those was giving the wing one degree less angle of attack at the root my thought was that this might prevent it from going into a high speed stall I launched these with a larger bungee and was getting some pretty unexpected flight characteristics boom go whoa whoa blew up one two three whoa that was crazy on this flight here the plane seems to be flying straight and level and then all of a sudden boom it does a rapid barrel roll absolutely out of nowhere and keeps rolling until it hits the ground super weird whoa on this one here it seems to briefly get stuck on the tether which caused it to pitch down but then suddenly pitched back up just to barely avoid hitting the ground the weird part was that it didn't keep pitching up it leveled off and flew relatively straight until it rolled off into the ground but hey wait this plane has dihedral it's supposed to be passively stable on the roll so why did it do that well chances are on some of these models I had a fraction of a degree of error when gluing the two halves together and that's enough to give them a huge role bias and that outweighs all the dihedral effect also small planes behave very sporadically with high Wing loadings I should note that these 3D printed planes weighed pretty much the exact same as the solid wood plane I feel like I need to address weight here because I know so many people are going to be suggesting that I use lightweight pla they aren't wrong these planes would undoubtedly fly better if they were lighter but the point of these test planes is to be representative of the wood plane and the point of the wood plane was to see if I could make an impractically heavy airplane fly just by getting it going super fast so next up I decided it was time to do some drop testing from a drone this first one dove straight down and then once it had enough air speed it pulled up whoa it's going it's going but then it went into a spiral and dove into the ground this next one just went straight into the ground two one go there we go whoa that went fast that was my first thought but I think what really happened is it just didn't have enough altitude and AirSpeed to pitch up okay I'm going from higher this time to see if it pulls up with enough air speed [Music] wow no idea where that whoa holy that flews so far oh my God it must have pulled up and flew flown up and then gone down again whoa I could hear that thing whistling it was going that fast so to bring this full circle back to our pitch stability lesson from before what was happening is that as this thing was first dropped it didn't have all that much air speed so the gravitational forces outweighed any aerodynamic forces and this caused the plane to go straight down because the center of gravity is in front of the center of pressure and then once it got going super fast the aerodynamic forces from the angle between the wing and the horizontal stabilizer started to overcome gravity and at this point the plane went full send it had enough kinetic energy to climb way up clear out of the frame and then several long seconds later I was lucky enough to capture it coming back down after it bled off its air speed and gravity started to overcome the aerodynamic pitching forces again so that was amazing unfortunate personally it flew away so I was unable to measure where the CG was now I've got a super long bungee but I feel like this is not going to work not much left of that if the gliders were too tail heavy then they would try to pull up prematurely but since they have a high Wing loading the wings would just stall and start to spiral here the plane just went straight into an unstable spiral before it straightened out but then the ground came up too soon they probably would have flown if it were dropped from higher damn that thing turned into a torpedo I figured if I was going to keep driving to the field to test these things out I may as well try some different designs as well this here is a delta wing with some reflex and a Twist in the airfoil oddly it seems to prefer flying upside down if at all not entirely sure why probably too much twist in the wing that was weird most of the time it wouldn't even recover from the initial tumble it's worse it's a seed pod I tried moving the CG further forward but that didn't seem to help turns out the other design also occasionally had this problem of never really recovering from its tumble before straightening out so I needed a better launching solution here's what I came up with speaks for itself I glued these little plastic rail guides onto the bottom of the planes apart from getting stuck on the rail sometimes it actually worked really well at preventing the planes from tumbling after launch the issue now was that the rail guides were adding lots of drag to the bottom of the aircraft this moved to the center of pressure down making the aircraft want to pitch down more at higher speeds or in other words they just became more of a lawn dart even the delta wing just Dove straight down so yeah not much luck with either design on this day look at that beautiful airfoil there it goes whoa Jesus all the planes up until now have needed additional weight added on or denser infill in the nose in order to get the center of gravity right this got me thinking that it would be cool to design a plane where the natural weight distribution of its shape would result in the correct center of gravity so I hopped into onshape and this is what I came up with it's a bit like the space shuttle but a little less boxy and more aerodynamic I added some dihedral to hopefully get a bit of roll stability and for pitch stability we can roll back and look at the original sketches that the wing is lofted from you can see that I'm using an airfoil with some reflex to it reflex is that little up kick in the back also the airfoil at the tip has a negative angle of incidence whereas the airfoil at the root has a positive angle of incidence this works just like pitched ability on a normal wing and tail type airplane the key is that the tip profile is behind the center of gravity so it's adding downforce in the back and that causes the plane to pitch up and again that downforce is AirSpeed dependent resulting in passive stability you can have access to this on-shape model for free including all the original profile sketches and everything so you can make changes tweaks and tune things or whatever you want to do just click on the link in the description to sign up for a free on-shape account to access it here it is in real life it's got a hole in the middle for the rod but I forgot to bring the rod to the park this day so we aren't going to use it here we go up into the sky so this one actually started to fly but then the two halves probably weren't glued together perfectly straight and it ended up kind of circling down in a bit of a spiral a good start though I dropped another version that I printed and this one took off and actually flew pretty straight a little too straight three two one drop it's flying oh that's excellent oh my God that thing is gone holy crap whoa okay I'm a litter bug I'm never gonna be able to find that thing it's gone okay I'll go have to pick up some random trash to offset my my litter that thing's zoomed what I didn't realize until watching the footage back is that this thing did a Big Arc and pulled up to gain altitude just like the other one did pretty awesome and then you can see it hit this tree here the noise must have spooked to the horses because they all started running so the next day I printed some more of that same design on my flash Forge guider 3 plus and I also printed this big chunky lifting body design that you can also get through onshape what do you think of this you think it'll fly I think it will but I also think it's fat it is a little fat let's do a test Quick Test yeah it seems to nose down when I drop it that's a good sign that sure didn't work very well I think it's CG was not quite right I'll revisit this one again later back to our original design this version has a hole through the middle so it can fit on the rod without any aerodynamic disturbances oh wow that thing's flying like a Tweety Bird oh it's flying all over the place damn where'd it go so it looked like this thing started out doing kind of a swooping flight path but then the oscillations damped out and it settled on a nice smooth Glide slope wait what is that is that it no that's a bird right what is that is that dead oh my God that's it holy that thing was in the air forever whoa that was awesome that whole flight lasted 40 seconds which is super impressive for a heavy little 3D printed glider with a high Wing loading like this after that I tried it again and this time the swooping motion didn't damp out as quickly beautiful so far so good oh it dived it swooped all the way down into the ground still a great flight though holy crap it's going so far oh it's just up and down it's a little too tail heavy look at that oh that is epic that was so good back to the shuttle design I printed another version that was split front to back instead of down the middle like my previous versions by making this adjustment it ensured that any potential errors in gluing the halves together wouldn't result in a roll bias thus improving its chance of flying straight I also printed this one with a thinner outer wall and less infill so it was lighter than a solid wood version would have been wow this one's a beauty oh my God it's so Majestic look at that it's just cruising in perfect beautiful circles with no trim or anything no center of gravity adjustment at all it's just amazing oh the amazing thing about this model is that it doesn't even have any like modified infill you just print it as one chunk and the center of gravity is perfect just based on the natural geometry and mass distribution of it then I gave the thick lifting body one more try and this time it actually worked wow it's kind of it looks like it's more or less working whoa huh interesting I'm glad I tried that again I printed a new version and added trim tabs so that this time I could hopefully get it going straight drop oh [Music] holy cow it's flying oh it's circling circling to the right so I gotta trim it to the left a little bit there it goes will it fly straight or will it not oh oh wow it will oh and then it looks like it just kind of stalled it was doing it for a sec yeah maybe it's always turning because it's always in a stall after giving it some down trim to hopefully keep the airspeed up it seems to Circle a bit less not terrible for something with wings this stubby next it was finally time for the solid wood airplane to fly I measured the center of gravity from the 3D printed version that flew really well and marked it onto the wood version then I poured some molten lead into the nose to make it match I dropped it without the rail so that I wouldn't have to add a guide tube that might mess up its aerodynamics it tumbled at first but then it straightened out and a lawn darted I didn't drop it from high enough but if I had in hindsight I think it would have worked really well I removed a little nose weight to get the CG further back nope it is seed potting dang I need that rail the seed potting made me think I had moved to the CG too far back but the next drop made me change my mind at first it looked like it was just lawn darting but at the end we can see it just barely started to pull up a little bit before hitting the ground I really needed to drop this thing from higher but I think I was too afraid to do it because I didn't want it to fly away come on on this drop I think it was more nose heavy because the wood on the front was wet it also kind of looks like it was wiggling in midair which is weird this could indicate it was near a high speed stall the whole time for this drop I drilled out some more nose weight while I was at the field oh where'd it go I don't see it at all I think I just heard it land over there hmm it might have landed somewhere over here could have gone way over there for all I know that thing is gone I have been walking around for quite a while now and there are no signs of that airplane but I did find a pile of wood so I could just grab some of that and make a new one I'd say chances are it flew across this River and there's no way I'm gonna find it over there holy crap oh what no way oh I cannot believe I just found this wow I was just aimlessly wandering around for like 20 minutes and suddenly there it is wow that is crazy I'm missing the nose it looks like the vertical stabilizer is cracked but the wings are fine okay well that's proof the solid wood airplane does indeed fly to fix it I mixed up some wood filler putty my plan was to mold it into the shape of a new nose so I smeared it on there and then I cut off the nose and threw it in the garbage this was because I decided to steal the other nose off the failed CNC piece and tape it onto the good body that's a weird looking airplane but hey at least with this nose I won't need any lead since it's much longer and therefore heavier today I got a brass tube glued on the bottom so we can launch it with the rod three two one drop I guess the brass on aluminum was a bit too sticky are you serious okay take two three two one drop you just go there it goes if you look closely you can clearly see the plane is flying upside down oh my God it's flying holy cow look at that incredible well it was flying and then it turned what it turned this is probably because the tube on the bottom added enough drag to move the center of pressure below the center of gravity causing the plane to pitch forward I couldn't see this through the viewfinder so I lubed up the rod with some chapstick and tried again yeah the Chapstick worked oh my God whoa whoa it just hit the tree right above that truck I just went into the tree I think it was going so fast I feel like it could oh wow I found it already oh gee whiz oh no my airplane just sitting in the tree without me well I think the fact that it flew from way over there to right there proves that it does fly how well it flies that's another question but it definitely flies once again it decided to fly upside down not a great finale for The solid wood airplane but at least it showed some potential I think if I were to make another version and get the CG right it would fly even farther than the 3D printed ones did this is because it has a much smoother surface finish than the fdm layer artifacts from 3D printing so it would have less parasitic drag and fly faster and farther I think that if I ever revisit this concept I'll CNC cut the shuttle design because it's cooler anyways that's all for this video thanks for watching bye beautiful

Channel: rctestflight

Views: 1,193,941

Keywords: aircraft, pitch, stability, roll, yaw, stable, glider, dihedral, heavy, wing loading, solid wood, wood, cnc

Id: 7oy3jXu_DmY

Length: 27min 57sec (1677 seconds)

Published: Tue May 30 2023