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MonoProp EasyVTOL Prototype

VAALLEON

Active member
#21
As a VTOL have you considered the benefits of counter rotating props, same style of BDF used in the FT A-10 release vid the Bix came up with. The font prop accelerates the air for the rear prop to thrust. 2 motors counterrotating will cancel out the torque roll
I absolutely did. I actually started designing it with counter props. But then changed course to reduce cost and weight. I will probably revisit if I can figure this one out. Another reason that I wanted to figure out the MonoProp is that I may build a larger gas version of this with a 9cc gas engine that I have. Maybe build it autonomous with ardupilot. Not sure yet, we'll see...
 

VAALLEON

Active member
#22
A better flight. It got into trouble 2 times but other than that it was pretty good. I started with a higher attack angle but after a minute or so switched over to a lower attack angle and got a better result. It is favoring left a little but so I need to re-tune the wings to fix that.



The problems and the solutions that I tried:

  • The unit is too slow in transition and thrust vectoring and lift from the wings not in balance. Solutions tried: reduced from surface area, retuned the wings to balance a little better.
  • Unit drifting when transitioning, resulting from counter torque from the prop. Solution tried: favored the left wing over the left one to balance.
  • Attack angle not stable: I have not resolved this yet but I think I am in the right direction. I added a stabilizer wing to the top and will extend it a little more.


My initial flight time calculation was not correct. This flight used about 1367 MAH and is about 4 minutes. So, with the new battery I will probably break 10 minute level but not sure if it will do 15 minutes. May be if I hand launch, fly really slow and not hover at all…



 

BATTLEAXE

Legendary member
#23
Seems like the wings are opening earlier to give it a platform to pivot into transition better plus they don't flutter as much. I would say you are getting closer
 

VAALLEON

Active member
#24
Seems like the wings are opening earlier to give it a platform to pivot into transition better plus they don't flutter as much. I would say you are getting closer
Yup! A muuuuch better flight. Extended the rear stabilizer and a slight tune-up and we are there. This is 3 minutes flight that I used close to 1000mah. Which should give me about 9 minutes max on a full charge. The unit drifts a little bit in different attack angles but I can live with that. Everything works fine. I am almost full roll + a little but of yaw from time to time to keep it on the park. When I apply a little more yaw it makes super tight turns. The neutral hover has a little forward built into it for added hover stability and easier turns. Will get the new battery ready and test the flight time. Interestingly, the unit doesn’t seem to have a significantly longer flight time over the same size EDF unit…. Am I doing something wrong here? Props supposed to be way more efficient. Anyways, happy with the result. Very fun to fly. Time to install the cam.



 

Piotrsko

Master member
#26
Nice flight. Didn't think it was a gull wing but I like the surprise; IMHO needs a bat wing. Props are more efficient but battery time is used up in watts. Can you vector thrust an edf into hover? If you have enough thrust, yes. How many watts will that edf take to get the thrust you are generating with the prop? Probably more. Put it on a scale then select an edf that has 1.25 times your measured weight as thrust. Suprised?

Can you throttle back some in horizontal flight? My bird thought you were issuing a mating call and keeps screeching back, so I have to kill sound.
 

VAALLEON

Active member
#27
Nice flight. Didn't think it was a gull wing but I like the surprise; IMHO needs a bat wing. Props are more efficient but battery time is used up in watts. Can you vector thrust an edf into hover? If you have enough thrust, yes. How many watts will that edf take to get the thrust you are generating with the prop? Probably more. Put it on a scale then select an edf that has 1.25 times your measured weight as thrust. Suprised?

Can you throttle back some in horizontal flight? My bird thought you were issuing a mating call and keeps screeching back, so I have to kill sound.
haha (bird)... Batwings is an interesting idea. I already have an EDF unit that can do it really well (check the link in the first post of the thread). I moved over to prop to get significantly better flight time but I am getting slightly better, which is really weird and disappointing. Obviously I am doing something wrong... I am not sure if cutting the throttle will help a lot.

Below is a new +5 Minutes flight that used 1950MAH of the 3000MAH on board. I messed up the transition back to horizontal and crash landed the unit. Minor damage. The thrust is significantly lower at the end of the flight which also contributed to unsuccessful landing. I want to test a 3 blade prop to see if I can get some more kick...


Onboard cam:

Ground cam:
 

Piotrsko

Master member
#28
The 3 bladed prop on a V35 bonanza is more efficient that the 2 blade even though it is shorter. Definitely not the norm however, most full size lose thrust going to 3. I don't have the engineering to understand why. OTOH many here swear by multi blades over 2.

Transition back to hover looks trying. I suppose it's not just nose up until it on the prop?
 

Vimana89

Legendary member
#29
Forward flight looks nice and stable, sort of like a little RET plane with dihedral wings. I like the look and idea. Transition does need a bit of work, but I'm sure you'll get that part of it dialed in no problem. Cool to see some of the new transitional concepts you have been trying lately(y)!
 

VAALLEON

Active member
#30
The 3 bladed prop on a V35 bonanza is more efficient that the 2 blade even though it is shorter. Definitely not the norm however, most full size lose thrust going to 3. I don't have the engineering to understand why. OTOH many here swear by multi blades over 2.

Transition back to hover looks trying. I suppose it's not just nose up until it on the prop?
I thought 2 blade prop would be more efficient but I did order a 3 blade prop just to test and see. I am also concerned about the lack of thrust after 5 minutes of flight. The transition back most likely failed because the unit couldn't support hovering with the juice left. That's also why I want to test 3 blades, to see if I can complete a 6-7 minute flight without crashing with the added thrust.

I thought hard and I think have a better idea on why the efficiency is not there. It is the drag from the design and 5 servos sucking some of the energy. Especially the wing servos are under continuous load at horizontal flight. So, I need to come up with a much sleeker design which will cut the air. The same design should support horizontal flight and reduce the load on the wing servos. I have a couple of ideas shaping in my head. Meanwhile I will keep on testing this design with the 3 blade prop and possibly with a 4S setup.
 

VAALLEON

Active member
#31
Forward flight looks nice and stable, sort of like a little RET plane with dihedral wings. I like the look and idea. Transition does need a bit of work, but I'm sure you'll get that part of it dialed in no problem. Cool to see some of the new transitional concepts you have been trying lately(y)!
Than you sir! The design is definitely not final. I will keep on improving to reduce drag and improve flight time. I think it has a lot of room to grow.
 

BATTLEAXE

Legendary member
#32
Than you sir! The design is definitely not final. I will keep on improving to reduce drag and improve flight time. I think it has a lot of room to grow.
Watching your vids I can definitely see the improvements with the tweets you have done, sweet flights. I think your efficiency issue isn't with the prop selection or even choosing between props over EDF. I think if your wings extended fully you would see a significant increase in flight time. The prop itself is not only creating thrust, but also the majority of your lift even at semi-horizontal flight. The wings are good to hold the stability for control but aren't contributing to the lift much. I have a theory that if the wings extended out flat in the transition you could drop some throttle in horizontal flight because the wing is now doin the work for free.
 

Piotrsko

Master member
#33
Unless you need the speed in open and close, why not consider an over center lock mechanism like landing gear? Retracts come in all sizes nowadays, and can be operated by one servo. Once locked down ( or in your case, out) there is no servo draw when adjusted.
 

VAALLEON

Active member
#34
Watching your vids I can definitely see the improvements with the tweets you have done, sweet flights. I think your efficiency issue isn't with the prop selection or even choosing between props over EDF. I think if your wings extended fully you would see a significant increase in flight time. The prop itself is not only creating thrust, but also the majority of your lift even at semi-horizontal flight. The wings are good to hold the stability for control but aren't contributing to the lift much. I have a theory that if the wings extended out flat in the transition you could drop some throttle in horizontal flight because the wing is now doin the work for free.
I agree with your diagnosis. I think I would get a better flight time if the wings go flatter. I need to do some hardware updates for that I think. The wings are not extending any further in the current status. Thanks!
 

VAALLEON

Active member
#35
Unless you need the speed in open and close, why not consider an over center lock mechanism like landing gear? Retracts come in all sizes nowadays, and can be operated by one servo. Once locked down ( or in your case, out) there is no servo draw when adjusted.
Thanks, that is not a bad idea actually but I cannot do it because the wings are active during the flight, stabilizing the unit. However, I am considering a design that doesn't put continuous load on the servos.
 

VAALLEON

Active member
#36
@BATTLEAXE I extended the wings and did get a better flight time. This flight is about 4 minutes and used up 1341mah, which points to an estimated flight time of 9 minutes. I did get into trouble once, so need to re-tune some other parameters to accommodate the new wing angle. However, overall good flight and I had enough juice to land. I will see if I can somehow push 10 minutes with some other adjustments. Meanwhile waiting for the 3 blade prop to see if it can give me a little more kick so I have enough juice to land after a 7-8 minute flight.

 

VAALLEON

Active member
#39
The latest flight after further tuning. The unit is pretty stable. Did a couple of stop and go's to practice the transition. The unit is consistently pointing to a 9 min max flight time. However, that would mean slowly laying it down on the belly at the end of the flight as it wouldn't have enough juice for vertical landing. This this make MonoProp a VTO? lol



I got the 3 blade air screw props. Haven't air tested yet but they sound completely different. I am very curious how the unit will perform with the new prop.



 

VAALLEON

Active member
#40
Installed the 3 blade props. Much better sound and less noise, better thrust and the unit felt a little more controllable, except a wobble started when hovering. It is very weird that the prop chance impacted the hover characteristics... I'll need to do PID again to see if I can fix it.

The flight time shows between 8-9 minutes, a little less than 2 blade prop but 3 blade test was promising enough for me to pursue this setup further...