Is VTail okay for starters?

[jstapels]

Hi All,

First, since I'm new I wanted to thank everyone involved in the MultiWii project. It an amazing piece of software that gives noobs like me a chance at playing with some really cool "toys". Now on my (first of many) question...

I'm starting to build my very first quadcopter and while I have a strong programming background, I know next to nothing about RC aircraft. I've seen a few videos of V-Tail style quads and thought they looked pretty cool. I was wondering if that would be a good style for a "starter" craft or if it's recommend that I build a more typical X style copter before I start to experiment with something more advanced?

Any and all feedback is much appreciated.

~ Jason

[kos]

.. a good starter craft is a craft that you can crash without being sorry.

v-tail are generlay speeking more difficulte to balance (center of gravity not being necessarily the center of the quad)

[PatrikE]

V-Tail is easier to se the orientation of in the air.
It's not to critical with the CG. The physical CG will be behind the centerplate.
I balance by by a sliding battery and adust CG forward.

[Bledi]

for VTAIL there is differents solutions and differents problems.
The comon problem is to find the best mixing vs your flying style
In my case, this one :

- the mixing is a Y4 one
- the biggest problem is to have a tail with no vribration. On the final version I had a horizontal plate.

The flying style is near a tricopter but with a very good yaw

[jstapels]

Bledi,

That's a very impressive build and I've seen some of your videos, amazing stuff! If you don't mind me asking a few questions...


1) Did you make the frame yourself? Or is it based on an existing kit?

2) What motors+prop size did you go with and how did you arrive at it?

3) How did you balance the thrust for this model? Is it 33% at each point similar to a tricopter or is it closer to a 60% front, 40% back setup?

[Bledi]

Bledi,

That's a very impressive build and I've seen some of your videos, amazing stuff! If you don't mind me asking a few questions...


1) Did you make the frame yourself? Or is it based on an existing kit?

Yes it's home made frame, but I have if a frame-maker want to create a kit with me ...

2) What motors+prop size did you go with and how did you arrive at it?

For motors it is different compare to other VTAIL. In my case the front motors are 1400kv and the rear 1100kv but the 4 props are the same.
How I arrive to it ... it is fun it's juste because I didn't find 9" prop so ... I used my 8" but with different motors. And the result was very good.

3) How did you balance the thrust for this model? Is it 33% at each point similar to a tricopter or is it closer to a 60% front, 40% back setup?

For my VTAIL the mix is different, for pitch I use -1/+1 front have the same thrust as rear. for roll I only use front motors, for yaw only rear one

[jstapels]

Your copter is very inspiring, I think I'd like to attempt to make something similar. Thanks a bunch for the info.

[Bledi]

the loopings of the day :
http://www.youtube.com/watch?v=FguyHC1KsiM

[jstapels]

the loopings of the day :
http://www.youtube.com/watch?v=FguyHC1KsiM

Nice vid!

How did you settle on having the rear props push down rather than pull up?

Merely cosmetic or did you find it was more stable that way?

[Bledi]

the distance between the 2 motors is more important so it's better for the stability. The second reason is that the 2 motors push to the center.

[jstapels]

Okay, good to know. I was thinking along a similar approach as it seems to me that if the motors are pulling away from one another and the "prop wash" is colliding, there would be a lot more turbulence on the tail.

[copterrichie]

Okay, good to know. I was thinking along a similar approach as it seems to me that if the motors are pulling away from one another and the "prop wash" is colliding, there would be a lot more turbulence on the tail.

Believe it or not, that collision is a benefit.

[jstapels]

Believe it or not, that collision is a benefit.

Not sure I'm following you as it looks like you have your props setup differently. Looking directly at the tail of your copter, you have...

A) Your props pushing air down and away from one another. So your motors are thrusting up and into one another.

B) Alternatively the motors could be on top of the tail, pushing air down and into one another. So the motors are thrusting up and away from one another.

So you're saying that there's a benefit of (B) where the air is colliding which looks to be the opposite of how you have yours setup.

[copterrichie]

LOL, have fun.

[Bledi]

I think the best solution is the flying solution. The copterrichie's VTAILs are flying very well, my VTAIL also but we don't have the same flying style, the same motors, ...
I don't had made calculations etc my VTAIL is just a proof of concept.
So VTAIL is just fun even if you have the props thrusting ouside or inside

[kos]

Okay, good to know. I was thinking along a similar approach as it seems to me that if the motors are pulling away from one another and the "prop wash" is colliding, there would be a lot more turbulence on the tail.

Believe it or not, that collision is a benefit.

is not .. please consider the properlers intake ...

De préférence, l'entrée d'air est symétrique par rapport à un plan médian passant par l'axe du pylône et par l'axe du moteur

[copterrichie]

Okay, good to know. I was thinking along a similar approach as it seems to me that if the motors are pulling away from one another and the "prop wash" is colliding, there would be a lot more turbulence on the tail.

Believe it or not, that collision is a benefit.

is not .. please consider the properlers intake ...

De préférence, l'entrée d'air est symétrique par rapport à un plan médian passant par l'axe du pylône et par l'axe du moteur

Yea right, LOL

[copterrichie]

The fundamental idea of having the props pointing inwards verse outwards is very simplistic in nature, the two airstreams combine creating a downward thrust with less lost. Just how much lost can be calculated at SIN(angle of Tilt).

However there is a maximum angle of 30 degrees that yields the greatest efficiency when pointed inwards. Pointing outwards, there is a greater lost as the angle increase.

[Bledi]

Don't be so categorical.
Me, it is with 40 ° that the results are the best, given the behaviour of my VTAIL also in stationary and looping, I think that different solutions are possible.
If you watch my videos, I do not think that you will find that it lacks power.
As I said there are different approaches and different solutions that work very well.

[copterrichie]

That is Lost in DOWNWARD thrust. Bottom line is, if it works, then don't fix it.

P.S. and if my memory is correct, this is why you had to compensate by using higher KV motors on the rear verse the first.

[Bledi]

no 1100kv rear and 1400kv front ... with the same props ...

[PatrikE]

And i have another setup with the motors tilted 20°
Same engines and props on all four.
1100 kv 10*4,5.

I think the best solution is the flying solution.

The V-Tail is no Rocket sience.
In fact The lift from the rear motors will be enough.
The more you tilt them The more response yu get on YAW.

So just build it and Testfly then change the mix to suite your machine and flyingstyle.
If it's not good just Rebuild in new style....

/Patrik

[Bledi]

+10000 it's what a try to explain !!!!!
Just have fun and just try what you want !

[copterrichie]

LOL, interesting that it is not Rocket Science when the idea is not of our own. Hmmmm.

[copterrichie]

Ha!

http://www.youtube.com/watch?v=23Kdoa2JwOo

[jstapels]

I agree that testing is the way to go, but for a beginner on a limited budget, as much upfront knowledge as possible can only be a "good thing". After looking around at various builds and doing some back-of-napkin math, I'm planning on going with four hexTronik DT-750. On the front 11x47s, on the back 10x47s pushing down and out at 30 degrees (similar to Bledi's build). That should give me around a 1000 grams of vertical thrust on each point.

By having the rear thrust outwards, I suspect I'll be sacrificing a little bit of efficiency to gain a little bit of yaw stability. CopterRichie's linked vid seems to coincide with my thoughts that while having the motors push air into one another is more efficient, there will also be a little bit of a yaw-wobble from the turbulent airs being thrown into one another.

I also realize that having smaller props in the back isn't exactly necessary since the software+sensors will be smart enough to compensate, my thoughts are that if I can balance (maximum) vertical thrust, I should hopefully have a little more balance when dealing with either high-thrust or low-voltage situations. But as you've all pointed out, the proof will be in the pudding .

[Bledi]

Have à good flight and remember to send pictures

[copterrichie]

Nope, IMO prop size is not an issue, just spacing and where the CG is located in relationship to the Center of Thrust also known as the Axis of thrust.

[Bledi]

@jstapels : The Hunter-Vtail by DialFonzo & Bledi is alive !
I had work with DialFonzo to create a frame for the VTAIL. Our baby is flying like my "old" prototype.

The official post is here : http://www.rcgroups.com/forums/showthread.php?t=1622447
and the first fly video : http://vimeo.com/39434122

[jstapels]

Very impressive!