This is a commentary on thrust angle and wing incidence and how they each affect flight performance. Very useful info for flying wings and plank style wings. www.mh-aerotool... adamone.rchomep...
Hey Mr. West, I just wanted to put in my two cents regarding a couple of things that bothered me. In reference to the point of rotation of an aircraft, all aircraft will pitch, yaw, and roll at exactly their CG in flight, not at a point slightly behind. Also, the horizontal stabilizer does produce lift, but it is "negative" lift, or a down force, opposing the wing. This is required to stabilize the aircraft about it's lateral axis because the center of lift is always aft of the CG. Cheers!
Just what I wanted to hear, thanks. I didn't think torque should be to big of a problem. I am making a motor mount that will have several positions that lock in a certain degrees. My first pusher pod try did about everything you were trying to explain not to do in the video so I greatly appreciate your help. I'll have videos of the build posted on my channel soon I hope. As a reference I did buy the Cox SkyCruiser, a perfect tool for me to study with.
Very well explained and worthwhile experimenting too,on biplanes the upper wing is usually set at a few degrees more so the upper wing will stall first,I would like to see you do a piece on lifting tails as opposed to normal flat stab the more common variety,aerodynamics is a fascinating subject that every model builder and flyer should study and its fun too,then you can get the best from your models performance,I like the sketches too,I have subscribed to your channel
I built one of my RC airplanes with tail and wing parallel ( wing was symmetric airfoil). I positioned the motor (trust line down and right 1-2 degrees). So when flew the plane, it had a tendency kinda like nose heavy even though I checked and CG was correct. I trimmed elevator up to compansate that. Yes, its better to keep trust line and tail parallel.
Airframe relational proportions is important here too...like the location of the wing on the fuse, the size of your horizontal stab relative to the wing area, and so on....how do you know the CG is in the right location? Did you use a calculation, or the 1/3 rule of thumb? "Things that make you go hmmm?"
Well explained indeed, however what if i have a T tail, with the motor higher,than the wing, mounted on the horizontal stabilizer? What angle should i mount it at?
Yes, the calculated C.G. where it intersects the MAC cord. That is said to be the most efficient point to rotate the main wing to adjust incidence. This video came at a great time as I am converting a $6 dollar free flight glider called the dynam Hawk Sky at nitroplanes (dot) con. They have a large already RC version. However the free flight glider is EPP foam=strong, and it leaves me a platform to use any setup I like. I hope to see something on torque roll effect from a pusher, kind of stuck.
Just checked one of my favorite books, you got me thinking, lol. Incidence adjustments are made from the intersection of the C.G. and the "MAC" (MEAN AERODYNAMIC CORD) of the main wing. Ref. (Theoretical Aerodynamics, by L.M. Milne-Thomson, C.B.E). On a swept wing (NOT DELTA) use only 30% of the MAC in the same formula. Thanks again for the video! Not many on RU-vid make me think. LOL. Looking forward to much more great stuff!!
Hey Wacko...lol Thank you for the comments and these questions. I sent you a PM to clarify this thought in some detail. Also, please explaine the type of stall, tip, lift, or tail plane?
The stall is the kind that makes the plane want to go up, almost like its tail heavy. The only reason why I think its the wing angle issue is because on full throttle it want to climb up or if I cut the throttle, no motor running it still tries to climb up
Great video. My question is, what if the motor pod (pusher) has the prop one inch rearward of the leading edge and the thrust line 6" above the bottom of the airfoil?
Very good explanation MrWest. My understanding is the reason for such calculations is to try and get as close as possible to having 100% proficiency over the entire plane making it fly longer smoother and more efficient, which we all know is impossible. To many variables for this to happen. My question is with the angle of the motor? to a certain point you will either have to much angle causing more drag and pitch variation. Is the axis line what has worked best for you? Or aerodynamic law? thnx
MrWest, thanks for all your videos, I have two questions. 1. motor mount setting, should I be worry about the torque to the right and compensate to the left( motor down and to the left)? I am using a 12x8 prop. 2. would it be ok to make the wing span 1900mm or longer?
Hi Mr West. I'm building an airplane I designed myself and it is a flat bottom wing plane with a very high thrust line that is parallel to the bottom of the wing. The plane has a cruciform tail with the horizontal fin also parallel to the bottom of the wing and the thrust line and it is mounted high enough that it is exactly in the thrust line. I was hoping that the propeller wash will be sufficient to give the elevator plenty power to correct for the pitch down tendency of the high thrust line. The thrust line is about 4 inches high from the bottom wing. Is this practical?
Hi Mr West. What will be the thrust angle to counter propeller torque for a pusher plane with a clockwise spinning propeller when you observe the direction of rotation while standing behind the model airplane. Should it be to the right or to the left?
Awesome job MrWest! Very useful info! Hey I got a question. On my Axon the plane keeps stalling and the nose wants to go up all the time. So one of our RC guys told me that I need to mess with the angle of incid bcz cg on my plane is good. Anyways he added couple degrees at the back of the wing, the plane seems to fly better but it didn't seem to have basic acrobatics ability. Do u have any suggestions?
I just built model but mistakenly glued wing at positive incidence than I was supposed to do. Is there anyway I can adjust down thrust of propeller to compensate for this mistake?
Hi. Hope you doing well. And pray to my Allah give you more knowledge. I want to ask the motor should be fixed anti rotation of propeller? If yes then what is the formula for fix it?. Because my airplane goes down to one side opposite of propeller rotation.
Hey James, if you are using a right handed prop, which is standard, then NO! Pushers do not induce torque nearly the same as tractor mounted (pulling in front) Caution with the 12-8 prop bud...when using a 28xx something motor with higher kv than 900kv I would start at 12-6e. 1900mm span is good too but with less cord like 9" and about 1.25" thick. West
Hey Vizz...torque roll...hmmm, well it, IMO, would not nearly have as a pronounced affect as in a tractor mount position. Keep in mind the size/torque produced by these 2826 or less size motors. I do not account for it in my builds and have yet been able to isolate the cause of a wing dropping under power to torque affect. Sorry a bit wordy.
Very informative Mr West. I was hoping you could answer a few questions for me if you've got time (even if the video is 2yrs old). I scratchbuilt an imitation of the Axon from Experimental Airlines, my motor moount is higher than the trailing edge of the wing with the thrust going through the CG as to my knowledge I learnt that the thrust line should go through the CG (for pushers) to counteract the nose dip, whereas in your explanation you suggest 1-2" from the leading edge of the wing. What are your thoughts on the thrust line through the CG, knowing that the Axon's wing is higher than the horizontal stabilizer unlike your drawing? Also wouldn't the forward push be wasted if the angle is slanted higher above the wing and forcing the plane down more instead of forward? I'm hoping you could shed some light on the subject for me and your video did make sense but got me confused. No questions for incidence though ;) Radz
+Radz Gardiner Hi Radz, how did this work out for you with the thrust going through the CG on a wing? I just built a 900mm popwing with a box between the wings to carry my battery and FPV gear. I mounted the motor 2" high so that I would have clearance for the propeller since I decided to mount landing gear. Again this is a true pusher wing setup.
+Carl Bradley My Axon has long been retired since my post but flew great. From what i've learnt since then is that it is crucial for a high mounted wing to have the motor shaft in line with the wing taking into account little to no incidence on the wing, or have it through the CG. Too far forward and you'll tip the nose, too far back and the plane will be pushed down and there'll be alot of wasted power. Then again its a play around with your actual CG. But as for mid-wings its a different story, the prop shaft should be pointed a little forward of your CG, tested that out with the MERMAID. Parallel mount to the wing and you'll brutally nose tip. For a flying wing it'd pretty much be the same, adding a washer to the bottom of the X-mount will correct that if your motor is slighly raised above the wing's x-axis. Hope it helps, i only wished someone would have told me that last year, would have saved me some DEPRON but its all in the hobby! Happy flying
+Carl Bradley For flying wings you wouldn't have to worry too much since you don't really have a fuselage, so adjusting the motor angle if you're using landing gear should be a walk in the park.
The axis line is what I shoot for...and IMO there is no reasonable logic for moving the thrust line so far away from the roll axis to the point that thrust is misplaced or wasted, if you will. Thank you for the comment bud, West
