Tips/tricks for high aspect ratio single motor tail sitter?

I need to build a high aspect ratio single motor tail sitter plane. Kinda like a motor glider tail sitter, but with a lower aspect ratio. It only needs to prop hang to take off and land. I’m trying to avoid vectoring the motor or using dual motors. I’ve seen Andrew Tridgell’s videos and read the tailsitter threads on here.

I am building the plane from scratch. I’m wondering about control surface authority.

What tips or advice does the community have for me ?


This is very ambitious. You will have essentially no (copter frame) yaw control in the hover. The ailerons will be outside of the prop-wash so will not have any authority and the high aspect ratio gives the wings loads of leverage to yaw it round in the wind.

Two motors on the wings in front of the ailerons fixes this but it is still very hard to get it flying right. Two motors with vectoring in the pitch axis give significantly more control.

Thank you for the reply.

Traditional ailerons would be outside of the prop wash, but conventional landing flaps with individual servos near the fuselage wouldn’t be. They would be well within the prop flow, especially if I used an oversized prop. Currently considering a 17" prop on a ~2m wing. Will this work ?

I was more worried about controlling (copter frame) roll. With only one motor the only thing to invoke a roll torque would be the rudder. Would that be enough ?

Canberra AUV has at least simulated a similar plane with dual tilting motors. Not sure how they made out in real life as I can’t find any further information. It seems to have very good stability and control in the simulations. It appears they elected to go forward with a quadplane.

I’ve never made a SITL model. Would it be worth doing this before building something ? Or just build and test ?

I had not considered roll, as you say this will be very tricky. You will need such a huge rudder it would offset the benefit of high aspect wings.

This is my version of that, to my knowledge the only ArduPilot none-flying-wing tvbs irl.

It flys quite well, landing and take off get harder as you scale up, this you can sort of land on the tail and ‘flop’ forwards, as you go bigger this will just break stuff.

Realflight is a excellent tool for prototyping, if you don’t care about the graphics model the physics model is quite easy to change. There is a ArduPilot repository of models here there are a couple of tailsitters there you could use as a starting point.

Thank you for the quick reply.

“I had not considered roll, as you say this will be very tricky. You will need such a huge rudder it would offset the benefit of high aspect wings.”

Hmmm… would a big rudder have more drag and weight penalty than the inefficiency of a second motor ? Would it be better to have the rudder closer to the wing or further away ?

How do you think the Canberra UAV would fly with 2 non vectored motors ? How much is the vectoring needed ?

Not sure how I feel about doing SITL with RealFlight. Could I accomplish the same thing with FlightGear ? Or JBSim ? I run Linux on everything, not even sure I have a bootable Windows computer anymore. And I don’t feel like buying RF just to test this. I’m wondering if I’d spend as much time fiddling with the RF model as I would save if I worked on the real model.

Thoughts ?

Edit: why did this simulation not work as well as the other simulation ?

Edit: the AddictionX seems to be very responsive as a single prop non vectored tail sitter.

you don’t have to use the second motor all the time, you could have a dedicated forward flight motor, but then you might as well make a quad plane

Closer you will get more induced airspeed from the prop, further away there will be more leverage

without vectoring control in wind becomes tricky, and how would you take off

probably but it will be significantly more involved, I have no experience with either. Realflight has nice physics and the editor is quite easy.

crashing is much less costly in Realflight, and you can turn on infinite battery life.

What other simulation?

its not vtol tho, still has to have a rolling take off and landing.