A tiny scale plane

Bit windy but it flies quite well with plenty of power and duration.
The only issue is the two prop slip streams seem to interact with each other creating a side to side wobble. I did notice it on the ground runs but assumed it was an interaction with the ground but it isn't!
On a calmer day I should get a better idea of just how significant it is.

I could always try the P38 trick and set the props to outward rotation! .

Managed a video today - between the rain showers!
Not ideal conditions so as with all these tiny planes it has to be edited to show just the bits that you can see it!

It managed a loop ok!
It still tends to 'wobble' in flight as if the airflow over some part of the airframe is unstable and makes it oscillate.
CofG is at 28% the same as the previous Wren.
I will try reducing the wing incidence a bit.

The motors sound like they are singing 'ahhhhh'.

As the wobble was at such a high frequency (3Hz?) it did not feel like a conventional stability issue but more like the airflow momentarily braking away and then reattaching. At these slow speeds and small sizes the boundary between turbulent and laminar flow can be ill defined.

By reducing the wing incidence and flying a bit faster I hoped the wobble region would be avoided.
Every thing is glued so the easiest was to 'adjust' the fuselage just ahead of the tail plane.

Certainly seemed to work.
Now I have just got to cure a definite tendency for it to roll right when pulling a loop.

A bit more development on a possible Cessna O-2 which was afterall the intended subject of this thread..
First it wont be particularly tiny - 54" span
It should weight about 24 oz and with two Emax 2822 driving 9x5 counter rotating props should deliver close to 250W/lb!
As a 'tandem' it should fly well on one so it would be nice to be able to cut a motor in flight.
As simple low power test rig to demonstrate the effect using the "gear" switch on the DX6i to cut out the left hand motor.

I think it might be possible to programme the DX6i to be able cut either (or both!)

I thought I had better see what happened when a motor is cut and switched back on at full power.

In fact it is quite gentle as the ESC seems to ramp up the power quite slowly.
Bringing on the second motor does cause a small voltage drop but then it is only a very old 15c battery!

switch works then! How does it know to switch off the motor? (dare I ask, but am curious -its gonna get technical isn't it lol!)

He switches it on with the transmitter.

Old Fart wrote: He switches it on with the transmitter.

doh!! I know that! But how does the gear switch know to operate the motor?

Sarah
It is done using "mixes". The DX6i has two available.
You can tell a channel (in this case the throttle - ch1) to also drive another in this case Gear (ch 5). It called master/slave.
And you can tell the DX6i to make any of the switches work on any of the 6 channels in this case the Gear switch to switch off channel 5.
With this arrangement you can only switch off one motor.

What I have not (yet!) be able to do is to set it up so that you can switch off either motor but I fear you need more than 2 mixes to do this.
On the DX18 for instance you get 12 mixes but then it costs £550!!

Quorneng wrote: Sarah
It is done using "mixes". The DX6i has two available.
You can tell a channel (in this case the throttle - ch1) to also drive another in this case Gear (ch 5). It called master/slave.
And you can tell the DX6i to make any of the switches work on any of the 6 channels in this case the Gear switch to switch off channel 5.
With this arrangement you can only switch off one motor.

What I have not (yet!) be able to do is to set it up so that you can switch off either motor but I fear you need more than 2 mixes to do this.
On the DX18 for instance you get 12 mixes but then it costs £550!!

I knew it would get technical May take a few reads of this to sink into my peanut brain! lol But thank you
How do you "tell " it? Have not seen anything on mine to suggest it needs plugging into a comp and changing via some sort of programme??

Sarah
Its all done in the menus and selected by the thumb wheel - but it is a bit tedious to do.
The neat bit is the 'Monitor' screen which shows what the Tx is telling each of the six channels when you move the sticks/switches so you don't have to actually connect anything to test what you have programmed.

Next time you are here I will show you.

I am now facing the same problem Grumpy42 has with his P38 (although mine is a bit smaller!) - do I build it in one piece?
At 54" span and twin booms will make it a very tight fit in my Peugeot although no problem with the Scenic.
The obvious answer would be to make the outer wing panels removable but this does add weight and structural complexity. It would also require a plug and socket for each aileron servo.
I will have to decide when I have printed out the full size plan.

This Cessna is going to be a 'lightweight' hopefully around 24oz which should give 100W/lb even when flying on one motor!

The plan top view printed out.


I still cant decide what to do!