• This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn more.

MonoProp EasyVTOL Prototype

VAALLEON

Active member
#1
I have started this EasyVTOL project about one year ago to harness the lift from high attack angle wings, on an easy to control VTOL setup. The project started as EDF and I have put the link to that thread, showing the last successful videos of the EDF unit (https://forum.flitetest.com/index.p...tol-project-monophan.57023/page-2#post-513917). Even though I was able to extend the flight time significantly via transitioning to horizontal flight, EDFs are by definition inefficient compared to props and the best flight time that I will get will be around 8 minutes. This is pretty good for EDFs but I wanted to create unit that lasts longer in the air so I can do longer FPV runs.



Loving how the EDF unit flies, I revised my plans to utilize a large prop in place of the EDF, using the same principles of the EDF unit. Still working progress, but after many failures I was able get a proper stabilized and controllable hover. This last hover test is about 1.1 minute and used approximately 330mah of my 2600mah capacity on board, which gives it a theoretical hover time of +8 minutes, which is pleasantly surprising (almost double the EDF hover time).



I believe I can get the unit a little lighter and improve the air flow to push it a little further, not to mention the newer and higher capacity (and same weight) battery that I will get for it. I believe I will be pushing 10 minutes hover time, which will be quite awesome. With 10 minutes hover time I can probably get +15 minutes horizontal flight.



Now the challenge is to get it to fly horizontally. The unit drops the head too fast, risking to stall. But Haven’t really pushed it to see what it can do. That will be coming soon:)



 

Piotrsko

Well-known member
#3
If you're up +50ft, probably have enough time to recover from the stall. Didn't seem to take long on the high speed partial open pass. Very Cool however. Btw 2 bladed single prop? If it's a true monoprop, I am really impressed. Mono prop : weight balanced one blade prop supposedly more efficient than multi blade.
 

VAALLEON

Active member
#4
This looks like a winner so far, I like how the wings fold out. Looks like a complex unit, is this a partial of a full design or is this the complete package?
Thanks! This is intended to be the full package. If I cant' get it to satisfactory horizontal flight I may make some additions. If it survives ofcourse:) We already had a rough start trying to perfect the vertical flight...
 

VAALLEON

Active member
#5
If you're up +50ft, probably have enough time to recover from the stall. Didn't seem to take long on the high speed partial open pass. Very Cool however. Btw 2 bladed single prop? If it's a true monoprop, I am really impressed. Mono prop : weight balanced one blade prop supposedly more efficient than multi blade.
Thanks! Yes, will test the transition in some higher altitudes. It has a 2 blade prop. MonoProp refers to a single prop (as opposed to a multurotor) the way I am using it, not a single blade prop. I heard that the single blade props are the most efficient as you mentioned.
 

VAALLEON

Active member
#7
The effort to achieve horizontal flight capability in progress. Videos of 4 test flights with crashes due to hardware issues. I think I will need to do some aerodynamic changes to go with the tuning. The balance is still not there. After the second flight I took of everything that I believed not to be needed to reduce weight and get a better understanding of the issues.



 

BATTLEAXE

Well-known member
#8
Do you have a video of an bench intro of this thing? something where we can see how it operates. If there was something we could see close up could better help you out and give you suggestions. Like...

It seems that once the wings are deployed it is modeled as a low wing delta style, correct?

If that's the case, the wings fold out trying to fight thrust, drag, and gravity. Sugestion- if it was to open up as a mid to high wing so it locks out to rest on the wing stops, the wings would stay folded out because of thrust, drag, and gravity.

I will say though, it is one tough bird to take hits like that, and it's a cool idea. Almost looks like your avatar lol
 

VAALLEON

Active member
#9
Do you have a video of an bench intro of this thing? something where we can see how it operates. If there was something we could see close up could better help you out and give you suggestions. Like...

It seems that once the wings are deployed it is modeled as a low wing delta style, correct?

If that's the case, the wings fold out trying to fight thrust, drag, and gravity. Sugestion- if it was to open up as a mid to high wing so it locks out to rest on the wing stops, the wings would stay folded out because of thrust, drag, and gravity.

I will say though, it is one tough bird to take hits like that, and it's a cool idea. Almost looks like your avatar lol
Hey, thanks for the suggestion. Actually the operation is quite simple. The wings open with direct input from pitch. The wings also contribute active control by responding to yaw. Yes, it is kind of a delta or a wing when flat. I have dived into some deep thoughts and I think have an idea on the problem. The main difference between the EDF unit ant this unit with prop is that EDF unit is faster, and tilts easier... In other terms more responsive to pitch. For that reason to avoid stall on that unit I set the unit up to open the wings earlier in the transition. However, this unit being slow and less responsive to pitch input, it is not gaining enough speed to create the necessary lift to keep the attack angle when the wings open early. And when that happens the thrust vectoring is trying to keep the head up without any help from the wings and the unit is starting to fight itself...

I will re-tune the wings to open later into the transition to let the unit gain more speed to help the thrust vectoring keep the attack angle. It may or may not work but worth a try.

The unit has carbon fiber reinforcements. If I keep on crashing in the same pace it is probably half way through its useful life... Hoping to keep it off the ground unless landing:)
 

BATTLEAXE

Well-known member
#10
Ok yea I noticed the thrust vectoring but I don't know it responded on it's own to pitch. Seeing the wings flutter in mid transition I thought it was a servo struggling to open, or it was hesitant input by you as the pilot. And the yaw authority is controlled by the wings folding in respectively? That's cool, not simple but cool. What if you got the wings to fold out earlier to commit to the transition as opposed to fluttering when the prop could be working to create lift during throttle up. You will need wings before speed in the transition to stabilize the unit. Just a thought
 

PsyBorg

Wake up! Time to fly!
#11
I cant really tell if the prop is "ducted" with the stuff around it. If not maybe that is where you are losing the stability you had with the edf version? Maybe the propwash coming off the tips is bouncing around too much and or when the wings open only part of the wasted trust gets bounced about?
 

VAALLEON

Active member
#12
Ok yea I noticed the thrust vectoring but I don't know it responded on it's own to pitch. Seeing the wings flutter in mid transition I thought it was a servo struggling to open, or it was hesitant input by you as the pilot. And the yaw authority is controlled by the wings folding in respectively? That's cool, not simple but cool. What if you got the wings to fold out earlier to commit to the transition as opposed to fluttering when the prop could be working to create lift during throttle up. You will need wings before speed in the transition to stabilize the unit. Just a thought
The flutter is due to the yaw compensation causing resonance, amplified by cheap servos, body flex and high yaw compensation... The yaw input to the wings is to stabilize the unit at horizontal flight and get it to actually respond to yaw input in vertical, the reason being large lateral surface area that impacts the unit with even a small wind. I did actually get to open the wings a little later than usual into the transition after the last post and got a better result, but still not good enough. When they open later the unit is not speeding up. One more issue that I identified is that right wing is closing down after transition due to yaw input, meaning that the counter torque from the prop is rolling the unit to right side:)...

1- I will reduce the front surface area by cutting the top a little bit, letting the unit speed more into the transition. 2- I will re-tune the wing opening parameter. 3- I will favor the right wing to open more than the left one to balance the counter torque from the prop. 4- I may cut the wing tips...
 

VAALLEON

Active member
#13
I cant really tell if the prop is "ducted" with the stuff around it. If not maybe that is where you are losing the stability you had with the edf version? Maybe the propwash coming off the tips is bouncing around too much and or when the wings open only part of the wasted trust gets bounced about?
That is a valid point. I did test fixing that by putting a duct around the prop but it didn't help, then I took it off to reduce weight. The major problem is that I am trying to apply a slow air flow large area prop to a design which was built around a rapid air flow small area EDF. This is causing number of problems, one of which I believe is what you have said, but it is not the major issue, or significant enough to cause the transition to fail.
 

BATTLEAXE

Well-known member
#14
So you got the hover tests down, have you tried to shoot it full throttle vertical to see if the wings fully open or is it programmed not to do that until it goes horizontal?
 

VAALLEON

Active member
#15
So you got the hover tests down, have you tried to shoot it full throttle vertical to see if the wings fully open or is it programmed not to do that until it goes horizontal?
No, it wouldn't open the wings until pitch is applied. Yes, hover is good to go. I made the changes that I mentioned before. If still no go then I will try to trim the wings a little bit to smoothen it.
 

FoamyDM

Building Fool-Flying Noob
#16
@VAALLEON Your monophan/prop project is really exciting.
Try a rocketlike trajectory trust up and pitch forward. do you think changing the wing-open curve to be open earlier, at 60° to vertical or 30° AoA, so it starts flying at a high alpha might help? Seems to me, unless you are opening up LARGE lifting surfaces, your craft has to be moving fast to get lift. Based on vector math, at 30°, half the thrust is keeping the craft up. which means throttle will need to be near double hover speed to not fall, that also means 87% is forward thrust (~1.67 craft weight) until the forward speed is fast enough. for the lift to equal craft weight. About 1/3 the curve below is in that 30° zone that is the "getting horiz. speed" zone.
1575387940697.png

*Warning: This advice is worth the paper it's printed on*
 

Piotrsko

Well-known member
#17
IMHO, you are also having wing stability issues as the cg for wings and hover things are very different. Might you want to add a bit of length to the bottom or top of the wings so that the deployed CG for the wing is at the traditional 30% of chord leaving the CG for hover exactly where it is currently ? I'm not sure that would mess with hover stability however

Be also advised: you are in the league of very advanced degreed scientists who had the same transition problems.

Still very cool. You May wish to copywrite or otherwise protect the concept, could make money.
 

VAALLEON

Active member
#18
@VAALLEON Your monophan/prop project is really exciting.
Try a rocketlike trajectory trust up and pitch forward. do you think changing the wing-open curve to be open earlier, at 60° to vertical or 30° AoA, so it starts flying at a high alpha might help? Seems to me, unless you are opening up LARGE lifting surfaces, your craft has to be moving fast to get lift. Based on vector math, at 30°, half the thrust is keeping the craft up. which means throttle will need to be near double hover speed to not fall, that also means 87% is forward thrust (~1.67 craft weight) until the forward speed is fast enough. for the lift to equal craft weight. About 1/3 the curve below is in that 30° zone that is the "getting horiz. speed" zone.
View attachment 149793
*Warning: This advice is worth the paper it's printed on*
Thanks! Very good info, thank you. I always thought of the rocket like trajectory but never tried it. One of the reasons is that you spend a lot of energy to shoot the unit up like that. I had some other VTOL mono units and my transition has always been slowly tilting the unit, laying it on the lift of the wings. Most of the time I found success at higher attack angles. Probably because I am not too worried about aerofoil wings designs, etc... These are basically flying robots that are somehow trying to emulate airplane flight. The EDF EasyVTOL unit flies slow amazingly well but starts losing it as the attack angle approaches zero (which is fine, as the unit was never built to go fly at negative attack angles). My goal is to increase the flight time and distance, and make it very easy for the pilot to transition. And my experience with these units is that when I am around 20-30 degrees I am getting the most economy. If it goes higher or lower, than I am having to bump up the throttle to keep the unit going. Actually my recent updates match your recommendation, such as I made adjustments to get the unit fly a little faster to avoid stall. Thanks again for the good advice!
 

VAALLEON

Active member
#19
IMHO, you are also having wing stability issues as the cg for wings and hover things are very different. Might you want to add a bit of length to the bottom or top of the wings so that the deployed CG for the wing is at the traditional 30% of chord leaving the CG for hover exactly where it is currently ? I'm not sure that would mess with hover stability however

Be also advised: you are in the league of very advanced degreed scientists who had the same transition problems.

Still very cool. You May wish to copywrite or otherwise protect the concept, could make money.
Thanks! Very true, achieving a stable vertical flight and horizontal flight are two very different things. I usually find the balance with trial and error (so much for the scientist! haha)... If I add more to the bottom of the wings the vertical flight will be ruined. I agree that I am having some wing stability issues and some of it is resulting from the unit fighting the counter torque from the prop. My first thought was to favor right wing first but got worse. So I favored the left wing, and got a little more stabilized. I reduced the front surface area and did some other changes. I think it flies better but couldn't take a video, it was too dark...

Making money? I hope so but so far I have been spending... For about 6 years straight:)

Thanks man!
 

BATTLEAXE

Well-known member
#20
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