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CL 84 Dynavert vtol

#1
I thought I would start a thread on this project cause I think it’s really cool and comes with unique challenges. So far I’ve built a tricopter to get the hover to a place I can work with to add a fuse and wings. That was maybe 2 weeks ago. I then built the fuse and wings and proceeded to hover test the model in my garage
I then added the elevator, rudders and a jankey tilt mechanism. This worked only to 60 degrees max. This was probably a blessing given the cg of this test model was way too far back to be flyable in forward flight.
Went to the flying field to test and It worked great. Ran 3 batteries just puttering around.
Now I’ve taken what I learned and started the 3rd test craft (i guess, pics coming soon)
New features include
-Gear driven tilt
-Fatter more scale fuse
-15% bigger wing(not scale)
-Wing moved rearward(not scale) but CG is seeming to be the issue with this craft. It essentially has to fly on the main rotors with very little lift actually coming from the tail rotor. I found the pic from an old rcgroups thread from 2010.
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#2
Specs of the equipment I’m using
First off and most importantly I’m using dRehmflight code (shoutout to @Rcjetflyer2, he did all the hard stuff)😁 this runs on a teensy 4.0 and a 6050 IMU
4in1 esc off an old eachine drone
2300kv 2206 motors off the same drone
1 large servo for the tilt(any suggestions on the best way to make a tilt is greatly appreciated, I am trying the geared approach but we will see)
2x 9g servos for yaw tilt and elevator
2x 5g servos for ailerons
I want to run a 1300mah 4s but the nose needs the weight and the three(more like 2) can fly happily with a 3000mah 4s. This will bring the AUW to around 1200g. It has a 30in wingspan but really should be lighter. When I make a 4th version I will really need to spare every gram in the tail.
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this is version 2 with the pushrod driven tilt, yikes...
 
#4
alright I spent the morning messing around and I’ve got things starting to come together for a transition! now I have the two main lifting rotors no longer apply asymmetric thrust for pitch. Pitch is all controlled using the wing tilt. This allows me to move the motors to a more favourable position scale wise, and move the centre of gravity forward. This brings me to a new problem the thrust from the rear motor is far too great. to get around this I have scaled the motor assignment to 30%. This would then bring me a new problem where at 30% thrust from the rear motor I no longer have enough yaw authority. So I finally installed ailerons and have them programmed to move for yaw control in hover. Here is a video showing some of the control authority. The jerky movements are all me. If anything it feels a little “drifty” but that could be the wind on the fuse and wing
 
#5
Also just realized I never even posted about the failure of my 3d printed gears. The mesh and ratios and torque required was heating up the servo to uncomfortable level, I’ve gone back to push rods but with a push pull configuration. Seems to work better than the gears but I’m still worried about the wing moving in forward flight.
(P.s. I know this was supposed to be the nice one but that servo has been in and out like 5 times)😂😁
 

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#6
I spent a little time I had this morning messing around with the fading between flight modes, having a little trouble getting it right. For Kp_pitch_rate there are min and max values. When the servo reaches that value(for the tilt as example) I lose the pitch_PID. The servo isn’t at the end point so I’m thinking I might have the control mixer setup incorrect for fading. I will post more about the problem if I’m really stumped buti haven’t spent too much time diving into it and there is no rush to fly right now... it’s just a bit too windy for vtol testing.
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#10
Here’s what I’ve got so far, not sure how I feel about it yet, if I really want it to look scale I’d have to go bigger. But it’s taking a lot longer to build this way. Although it weighs next to nothing!
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The elevator is one carbon spar with two wood anchors and one control rod. The anchors will sandwich the foam former allowing the whole stabilizer to move. I was going to try and make the scale elevator setup, using 2 five gram servos in each side of the stab to make an elevator surface for forward flight. And the whole stab would pivot during transitions and slow flight (only down) just like the real one. But the space for the 5g servo just wasn’t there. Maybe if I go bigger one day.( oh I’d love retracts too)
 
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#12
So I’ve been a little stumped with the whole tilt mechanism. It’s been very difficult to make something with the right geometry so that the servo won’t stall. This is especially difficult given the way the motors are mounted on the wing, when at high throttle they can start pulling the wing vertical. I thought I had tried every solution and was wondering why I couldn’t get this to work, other people have made bigger wings tilt with less power, right? Wrong, I did some research on the servo I was using and it turns out high strength is like 3kg. This won’t cut it....
I’ve gone on Amazon and picked up a 20 kg servo. Hope this helps yield a better result
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#13
A little bit more building tonight. I’ve figured a yaw tilt that weighs less than the 3dprinted mount. I’ve also mounted a smaller motor to it. From a 2206 to an 1806 (Looks weak but everything has some kind of mechanical fastener. Aka not glue)
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I’m not just trying to remove weight in the tail but throughout the whole plane. With the more scale build the wing is much smaller. Here’s what the new one looks like beside v3.
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I am trying to spare every gram but that fancy new servo I got for the wing tilt has 45 grams on the old servo (85g servo, it’s like a piece of lead in the middle of the plane) but it should have the juice to move it with ease. I also got the elevator glued on. (And halfway glued some nacelles but who’s counting)Slowly and sloppy but surely... right?
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#17
Why do you have the rear tail feathers down when you are hovering? The real model plus the RC flying versions have it horizontal when hovering.
Because I’m still learning how to code the flight controller..... lol. The real CL-84 does hover with the tail horizontal however during transition and slow flight it is critical for rear lift. Not sure it has the same affect on the rc model. But for now I have the elevator set to come all the way down during hover and fade to horizontal for forward flight. I might change this to simplify the code and flight characteristics. This also helps clear the elevator surface from the tail rotor on my version 3. On the new build it will be in the scale position.
 
#18
A little worried about that tail motor mount--but I trust your judgement. Having it cantilevered off the flimsy servo horn like that looks like it could bend/twist around. But with such a small motor, I guess you can get away with it
 
#19
A little worried about that tail motor mount--but I trust your judgement. Having it cantilevered off the flimsy servo horn like that looks like it could bend/twist around. But with such a small motor, I guess you can get away with it
It still requires some testing but the tail motor shouldn’t be producing much thrust, with a heavier battery, version 3 would turn off the tail rotor completely on occasion. This was when I found out that I should use the ailerons for yaw in hover. I think I can get away with that tail motor mount but if it’s not up to the task I’ve got some other ideas. I plan on taking the version 3 out to the field tomorrow and then I can start moving electronics over.
 

L Edge

Elite member
#20
Did you see this video. It gleens a lot of good info, including the leading edge flaps(read about it but neverer did see it in other videos) that show up at 7:20 and 9:30. Watch as the angle of the wing goes down.
Also the horizontal prop is 2, so it is cw and ccw direction.
It is interesting that the angle of the wing is 15 degrees, not zero.
If you back up from hovering with horizontal stab down, that's a no no.
Tried this model a number of years ago, only using a bi-copter approach.



Hope you succeed. Wind is the biggest enemy.