RC SCRAPPY MAIDEN FLIGHT and almost the LAST FLIGHT
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- Опубліковано 5 жов 2024
- RC Scrappy got off the ground for the first time today. But not everything went as I expected. What happened??? You can already see in the video!!!
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Definitely looks like it's tail heavy. If anything you want to lean towards nose heavy. Also agree that expo and lower rates should help. If that doesn't do it, install a gyro. I love the plane! Keep up the good work! Wish I could build one.
his static margin may be a little tail heavy but i think the main problem is the wing size vs the horizontal and vertical stabilizer size.
I'm a commercial pilot, not an engineer; but if I had to guess I would say it's the main landing gear struts acting like canards.
Me too, and makes it tailheavy, like the engines on the 737 max.
That would make sense. On the real scrappy, the engine is a monster and thus needed extra lift up front
@@savage_x89right but also on the real scrappy, he made it have 28 or so inches of suspension travel and he wanted the parts to be light, and aerodynamic.. it is possible that his suspension geometry is different than your causing the arms to be at a different angle and lesser Issa of lift. It also appears to be a short issue too. I’m assuming you checked the cg before flying?
Yes those winglets on the wheels are causing alot of unstability I think because they are right in the backwash from the propeller, I also blame these wingless for what happened to the real scrappy, I believe a wing should not be in the wash of a propeller for the best stability and performance, but thats jùst my opinion and others would think differently ofcourse, I mean there are aircraft with these wingless on them but they are there to improve stability with wind tunnel testing and it just proves how affective these tiny wings or canards can be if one gets it right, on a jet or pusher it's perfect but different results on a puller prop the way I see it
Id 😮remove the landing gear skirts and move CG forward so it’s not to tail heavy. That should definitely help stabilize it way more then the maiden flights, good luck. Beautiful plane.
Impressive recovery and landing.
My first inspection points would be the cg and the throws of control surfaces. When you were checking movement on the controls, you seemed to have a ton of throw. Maybe turn those down and dial in expo if you haven't already?
First thing I would try is see what happens without the wheel strut cowlings, and with smaller wheels. Maybe move CG forward a tiny bit too.
Engineering and build skills off the scale, I am an RC pilot with 20 years experience on turbines, helicopters, war birds ect. I'd say it looks cg related, please be sure to do an update when you get it sorted. Good luck mate, when I grow up I want to do your sort of building models. Fantastic
Thank you very much
The fact that it calmed down at lower speed would suggest those wheel covers are acting as unwanted wing surfaces, I would re-check CG, non-laminar flow over the wing from the slats sitting too high, asymmetrical wing/stab incidence and did you give the engine a downward angle?
Agreed. they are enormous enough to be considered canards. Especially under the accelerated slipstream of the propellor. It makes sense why it would be docile under ground effect.
Absolutely, it would explain the problem going away at low throttle. The negative oscillation (non phugoid) seems to be more pronounced around high throttle which could be prop-wash striking the stab in a very disagreeable way.
The long-awaited maiden flight. after a few adjustments it will fly wonderfully!👍
thanks
Watching your channel you clearly have a grasp on CG, throw, and expo. I can't imagine you wouldn't have that sorted beforehand. So...curious if you are using an optical ignition kill switch? Without one (on a gasser) static electricity can develop and affect the RX. That would explain the complete loss of control at higher throttle settings and sporadic control at lower throttle settings. Glad you saved it.
You're models are beautiful. I love seeing your comments during the flight. I always wondered what you were thinking about after building these beauties while you are flying. Congratulations!
Thank you🫡🫡🫡
Aerodynamic instability generally comes from a small distance between the COG and the aerodynamic center. The airplane did not seem particularly tailheavy, but probably just on the brink. Try to add some weight in front to have a distinct distance between the two centers.
How about the fuel tank? Was it only half full and could potentially have increased the oscillating behaviour?
Just some thoughts...
Amazing recovery and very well handled! The plane seems to short for the size of the wings.. but I could be completely wrong.......
Really happy that you were able to save it! +100!
I just did a first flight after 25 yrs with a new Trainer . First 2 flights just like this . Removed tank cover and placed 2 small sockets in front of tank . Much better CG out but not by much 😊👍 That's a nice Aircraft and well done to get it down always tricky with such instability 👍👍
Thank you very much
Glad you got Scrappy back down in one piece! Maybe a combination of wing incidence and CG? Had a glider do something similar in the air until i reduced the wing incidence. Hopefully you get sorted!
👍🏻 Check wing and stab incidence
I agree with others, the landing gear airfoils, when the throttle is high, the prop is throwing very fast wind past those wheel covers, causing them to act like canards; so, they are causing lift in some direction, either up or down, it is causing oscillations. That makes sense that when you lower the throttle it gets better.
Rookie here: I would check the Angle of Attack of main wing, elevator and wheel covers. To me it looks more like that than tail heavy. Not all designs are scalable without modifications. So when you made everything like the original Scrappy, doesn´t mean it flies as well. The fuel tank is way in front of the CG, right? So it changes the CG when going from full to empty. Maybe try a smaller, but steeper prop to reduce prop wash on certain parts? This is more opinion than knowledge, but maybe I add some thoughts to it.
Good save, well done!
To me as a Pilot PPL-SEP and RC-Pilot it definitely looks terribly tail heavy.
On this type of wing, if it has a somewhat standard profile, I would set the CG to be at 25-30% for the first flight, measured from the leading endge of the slat.
And that would change with every power setting die to the profiled landing gear legs being in the propwash
Things to consider, get the Cg wet and dry, thrust line, add baffles to fuel tank to reduce liquid sloshing effect, try to remove slats and landing gear strut cover.
Probably CG, but also check on the ground if there is some servo movement when applying throttle, because RC ignition on high RPM can cause interference with servo signals, and cause uncontrolled servo movements.
Fantastic build! But wow, there’s nothing like the feeling of launching a new model, only to find yourself fighting to get it back down in one piece. Been there…
Engine thrust line maybe. That is one beautiful plane I can't wait for the next flight.
I must agree with Model AV8R! There must be some interference somehow or maybe just a bad rx altogether. I’ve built a few rc planes with slats and it does affect performance but never enough to cause a blanket over the tail in my experience! As well if the incidence of the gear wings are in line with the thrust it shouldn’t cause any pitching moment especially not an erratic one! By far my Favourite build I’ve yet seen on UA-cam! I hope you figure this out! Mostly, I hope it’s a quick easy fix! Take care and I look forward to seeing a smooth flight soon!
Your cameras could very well be throwing off your weight and balance as well as Interfering with air flow around the fuselage.
I think, that slats on the leading edge makes a problem of shifting lift along the chord of the wing. When flying at normal angle of attack aerodynamic center of the lift is somwhere we all asuume to meant to be, but when piutching model up, aerodynamic centre of the lift is shifted toward leading edge as LE slats starts to produce increased lift at very front portion of the wing. But of course, I could be wrong, as also CG of the model can influence a lot, then AWD between wing and tail, and possible cause is also the insufficient tail surfaces (pretty small in relation to the wing). Othervise, really good work on this scale plane of Mike Pattey! Congratulations!
If the oscillation increases with added throttle (or decreases at low throttle) I would suspect it's related to either the thrust angle of the motor or control surface deflection being too great. --Authority increases when the surface gets a blast of air from the prop, so having too much surface deflection can cause oscillation under throttle. To me it looks like there's too much control deflection on the elevator at least. I think I would start there (at minimum add expo). If you're using a stabilizer, the gain can also induce oscillation. Insanely sweet plane... glad you got it down. I think I would also agree with most here, that it's a little nose heavy.
My first thought was CG and then get lower rates in and some Expo.
WOW she looks GREAT!
Check CG not only as percentage of chord but also longitudinally down the thrust line. It looked heavy to port.
To really know what is going on, need more info.
Some things to look at:
wing mean camber will determine how much pitch instability is created by the wing, as well as the airfoil, and changing CP with AOA.
moment and area/planform of horizontal stab is fixed, so no changing it. and probably no need.
incidence of horizontal stab to wing
CG position
Engine thrust angle, and position in the vertical plane, relative to the CP. (probably most of the problem lies there, because in the video it seems that it stabilized when the power was reduced).
the scrappy thrust position looks lower than most single engine aircraft, which is already lower than ideal. probably should have at least 4-5 deg. of down thrust, perhaps a little more. 4 is standard. also about 2-3 degrees of right thrust, to compensate for P factor, slipstream effect, and torque effect.
Why you didn't start with a proven J-3 cub model design, airfoil and incidence?
well, not that hard anyway to get it right.
also make sure that servos are centering, and not getting EMI or RFI from ignition system under full power.
cheers! love your channel. it inspired me recently to buy a vinyl cutter to go with my laser cutter. :)
THANK YOU VERH MUCH
Maybe servo connections to do with vibrations from the engine. If you notice the problem changing more at different engine speed ?
CG off? Tail heavy 🤔 good job on bringing it home in one piece! ✌️😎👍
I think the 4 landinggear canards & the CG ? .. the plane acts so weard for that sice & with a Nitro.. Nice you landet it . Cat. "Spooky Flight " 😉
Glad it’s still in one piece! Was the CG set from the leading edge of the slat or the wing? On a Storch model that I have it’s set from the leading edge of the slat. Builders that set it from the leading edge of the wing instead had similar results as you had.
Great job! Mike Patey will be proud of you.
Looks amazing. The detail is... perfect. Hope you get it flying better. A gyro just seems like it would be a bandaid on the problem.
It looks like it was very sensitive to pitch and had little roll authority. That would indicate CG is backwards. I recommend going through XFLR5 stability analysis pdf. There's a bunch of info to determining airplane stability and CG. I bet this thing is going to fly well.
Beautiful plane 👍
Good save Marko. I've had a few of those myself, never much fun.
Outstanding effort. That said, I did think the tail area looked a bit small and the tail moment a bit short. Cannot change that easily so need other solutions. The plane becomes more stable when the throttle is closed because the centre of lift moves rearwards at low air speeds and moves further behind the centre of gravity - which increases pitch stability. I would add nose ballast but also add a pitch gyro in the elevator circuit. Now I will look at the next video to see what you did!
It's almost as stunning as "Scrappy"
Fantastic work buddy!
Thank you so much for continuing to share your content and creations with the rest of us.
Can't wait to see what's next?
Can you make a UMX Draco please 🙏
Wow that was hair raising, glad it didn't crash!!! Hopefully you figure it out before the next flight!!
Whew, that was really close! Fortunately, the results landed safely. BTW, this is the first time I've watched a UA-cam video and actually felt nervous. I even spilled my coffee on the floor.😂
could have been worse - at least you didn't spill it in your lap
@@raymondo162Fortunately, I was using a mobile phone at that time😆
My guess, in order: thrust angle, CG and maybe the ratio of wing to horizontal stab distance?
I'd check for wing stiffness at the wing tips, and CG, wing incidence and horizontal stab incidence.
That’s a good point, could be at the wing root too. 👍
All planes should do the CG check before maiden? Good build!
A local club member built a piper cub-like plane a few years ago. Maiden flight turned out exactly like this. I flew it a few times and found out that the landing gear covers are like canards. Also, with those high control throws on elevator/rudder, the plane will need more weight to the nose to make the plane stable. Luckily it survived, well done 👍🏻
Ok, very interesting. Many thanks
Superb landing!!
Cant really say much without knowing what the plane is doing versus your stick movements. Visually it looks tail heavy if its pitch sensitive from all that porpoising. On the other hand the way its holding the attitude changes after making a jump makes me believe its slat related.
Sweaty Palms! Excellent recovery flight well Done
Been there like 4 times. And every time it was a battery that moved and threw off the cg.
That would be my first guess.
When you landed, at slower speed it seemed more stable. Maybe it is the landing slats...... i have never flown anything that has had such a thing........ if they can be removed, try without.
I'd say bring the slats up a bit...that way when you look from the leading edge it doesn't fully blank the LE...
My small 1800mm super Cub did the same dance when the slats were set too low....
CG Issue maybe but My Bets are in the slat position...
Throws too look Good for a Cub...
Awesome plane Right there.....
yes i say very much cg this is very very nice build im doing one now electric and 50% of yours so fingers crossed i started the printing today
like everyone keeps saying C of G more forward and given it's a bushplane, could do with a bit shorter wingspan, yes ... and it'd be interesting if bryan is correct about the motor angle. surely a plane this size should not need a gyro. awesome build and looking forward to its next flight!
The sources of unstable flight are short distance between the wing and the stabilizer, a bunch of big surfaces like bulky chassis, wing supports in front of the stabilizer. The fuselage is so thick and there are so many thick bulky objects in front of the stabilizer that it makes the stabilizer is in the aerodynamic shadow right in the turbulence zone which makes it even less stable and less controllable (it basically like flying without stabilizer because of the stabilizer is located in inconsistent turbulent air). You need to relocate the stabilizer to move it out of the turbulent air. Maybe make the stabilizer bigger (bigger span) is the easiest way to make it more stable without changing the rest of the structure.
Good landing for this situation !
thanks
Definitely tail heavy but have you checked for interference in the radio from the ignition?
Close the slats gaps with some duct tape. Than place the CG at 25 % from leading edge and try again. It seems that tail volume is quite low but is hard to tell from the video.
Thank you. I was thinking about that also
Rule of thumb CG with a Hershey bar wing ... 25 to 30% of the chord. Also keep rates and expo within your limitations.
I think you have a bit of a rubric’s cube of problems. I would install a gyro to help you manage the problems in flight and then start addressing the many issues that others have talked about one at a time. I don’t like gyros but in this case it might help you to keep the airplane in one piece while you work through all of things that might make the model act tail heavy.
thank you
Either the gear strut covers or maybe thrust line? Hard to say without knowing 😜 glad it ended well, too nice of a plane to crash!
Wise man once said a nose heavy plane flys bad a tail heavy one flys once :P
If its more stable with power cut, definitely thrust angle needs a bit of adjustment, awsome plane and great relief you saved it, i hate that feeling.
Im saying tail heavy is the problem add a few ounces to the nose. It will be a whole different plane😊
make sure you add some flapperons but out standing job.
heavy wing and wing tips, tail heavy, gear leg covers are interfering, the aircraft's decalage may need to be addressed.
Try a longer moment arm (longer fuselage) it seems somewhat short also balance prop + check that CG i have had bad aircraft i dump them if they are not stable .
The front slat maybe pitching the centre of lift on the wing forward. The angle of attach may also vary the amount of pitch from the slat. I think the position of the slat is important to avoid the issue but that is just my guess. The extra drag from the large landing gear may be contributing to that as well. With high air speed, the nose pitches down due to the landing gear drag. Try flying without the front slat then try more conventional landing gear. This might isolate the issue. I think if it was the engine thrust line, you would just need some heavy trimming and not the oscillation that you were observing.
If it is the slat, you can adjust the position and shape of the slat to minimize the oscillation.
You are a very good builder but maybe double check the torsional rigidity of the wing and other surfaces. I just mention that just in case. If they were flexible, you would likely see the flutter.
thank you
Try flying it without those wheel strut covers. I had something similar and lost one in flight. It went bonkers until I slowed down. Also check your thrust angle? Not sure about that one unless you try a glide. Then throw on the power and see how it pitches or not. Amazing that you got it down so nicely. Well done!! I think your comments were a great place to start. You got this man.
More nose weight! And landing gear fairings need to be in line with stablizer, they need not to move or they will effect the cg.
Looked like it was out of balance? Power looked good. How is center of gravity?
Don't worry Marko , every problem has a solution, and you know that very well ! 😂I dont think it's a big deals! if never you find out the problem , let us know ! 👍✈
Looks amazing.
Definitely looks like a C of G issue. But if its jus out or being created by something else not sure.
Will fly amazing once small adjustment made 😊
Great landing!
I can't find it but there was a maiden flight of I thinks a large scale red biplane that did the same thing. On full power, he lost control but when throttled back, seemed to be ok. It was down to engine vibration interrupting the controls.
Long shot, I know.
thanks
Reduce your elevator throw or add more expo. You’re most likely continuously stalling the airfoil by over controlling(you could see it happen in your flare to landing even with the power off). It’s a cub so you shouldn’t need more then 1/4 in or so. In other words reduce elevator throw ( don’t give yourself enough rope to hang your self). 3d aircraft have large throws but the maneuvers “pull through” the stall until the aircraft flys on the prop. Stalls are also dependent on cg, but cg on the wing tube and you should be fine.
There’s nothing more frustrating when a plane passes all preflight checks and still flies poorly. A gyro would be a great idea to help you control it while you hunt down the issues. I’d be verifying CG, maybe moving it a little forward to be safe for now and removing the cowls on the landing gear. I think that they could be playing havoc with the aerodynamics. It would also be good to check for any flex in parts particularly twisting flex in the wing.
1- CG more lead in the front
2- reduce control movement
3- try to remove slat
Great job, Looks like CG is too far forward, always a good maiden if you take the model home in one piece well done.👍👍👍🛩🛩🛩
Forward?
It is too far back.
Interesting with the landing gear planes may indeed act as canards but more importantly the engine of the original plane was MASSIVE which is not replicated in your model. So adding more weight at the front should resolve the instability issue as well as ensuring the canards are angled to assist flight in all attitudes…
Definitely looks tail heavy in my opinion.
Gorgeous plane though.
Seems like the struts. Under power a lot of air over them they they where lifting but when you cut power was a lot less pitch sensitive. Plus it's a high wing and your extremely experienced the CG I'm sure is fine
YES IT PROBABLY IS THE MAIN LANDING GEAR ACTING AS A CANARD!!!
Tail heavy is a possibility. It could also be the huge gear leg fairings moving the aerodynamic center of pressure too far forward. Just because they work on the real thing, doesn't mean they will work for you. Aerodynamics don't directly scale.
thanks
It appears that you need to add weight to the nose to move the CG forward.
I think the vertical and horizontal stabilizer are a bit on the small side. Or probably the landing gear, hoes it have the correct angle of attack in comparison to the wing?
Now that is what I have been waiting for, right on, just amazing.
Sweet wagon.
Like most have said tail heavy and way too much elevator, and aileron throws. This plane will need some coordination with rudder. As i saw some adverse yaw in turns. And the wheel wings might be cause lift and need to be figured into the CoG.
Nice save! Well done. Looks like CofG maybe or maybe something to do with slats or the landing gear 'wings'? Or elevator flutter?
Hope you find the issue.
i reckon it's the winglets holding the wheels to the fuselage that's the problem #1
Looks tailheavy to me - and maybe too large control throws - maybe because I don't know what you like. Those large gear fairings will produce a lot of lift too, and you will need more weight in the nose to counter that.
Or maybe it is the ignition of the enging playing tricks with the radio.
Impecable trabajo. Gracias, disfrutos desde el inicio hasta el final con sus grandiosos proyectos.
Did you give an angle on the engine mount ? Gas engines need to be mount around 5 degree off alignment.
your expo is not accidentally inverted? (sensitive around neutral point?) believe me, I've made this mistake!
with such a flat wing (dihedral) that might account for the roll (lot of wing too).. And then what about pitch angle?
You did not display the CG nor the pitch angle so that would be suspect.. CG too far aft, and combine that with a center of pressure too far aft? I think that could account for the violent pitch and stability issues under throttle.. (need to see what thrust angle is also)..
Sure is a pretty build.. I do not have the skills for something like that so is fun to see that process...
Sorry I don't have any suggestions, but it is a beautiful plain. Best of luck. Maybe ask Mike Patey for advice, he might have a minute or two to help. He seems always willing to help with aircraft problems. He is a very busy man though. Back to work, lol.
Back to work yes ;)
It looks like the wing isn't stiff enough in torsion (twist). I had a foam glider do the exact same thing. When I slowed it down, the problem wasn't as bad just like your Scrappy. Also, are the leading edge slats well supported so they can't deflect up/down? That could also be the problem or could be adding to the problem. Finally, I think your control throws are far too large. I suspect overcontrolling added to the problem. But, that was an EXCELLENT SAVE!! You kept a cool head and never gave up. Congratulations.
Yes good save. I've had a number of first flights like that - which makes me wonder whether there is a more sensible procedure with RC models for checking the COG is actually in the right place compared to the vehicle CoP? Anyhow, yea bring COG 10% forward on the wing section, a few clicks of up elevator trim, and when at altitude shut off motor to see if the problem is CoG or something to do with propwash on the spats (spats are at same longitudinal position as the wings so I can't see them acting as canards but theres only one way to be sure eh?)
Good afternoon, is there any chance that it is the landing gear??? The black carbon fiber landing gear arms seem to be acting like canards!!! With that and it looked like the plane was slightly tail heavy, seemed to make it porpoise. Good luck my friend, can't wait to see it fly without issues. Robert
Great brother remember me 2yrs back 😊
Great Work, Awsome
thanks
first, congratulation staying calm and back earth with no dammage !!
after that, it's better going step by step ; if not, all mixes and it'll be impossible finding clearly.
according to me :
1- Vz control between wing and horizontal tail
2- motor axis control
3- CG at least 4-5 cm forward
4- increase exponential
and that's all for begining
I'm dealing with exactly these problems at the moment :) Thank you
Hope you solve it.
Cause I'll built mine....😊