English Electric Canberra - in Depron of course

Garry
I would agree entirely but with these tiny batteries the sticky tape holding the leads to the little circuit board to which they are soldered is virtually as strong as the wires them selves and I did put a :woohoo: to indicate it was not a recommended practice.

If a battery swells by more than a little it will have to be cut out anyway. Not such a big deal as the fuselage has already been 'cut out' to get the extended battery box in!

With the battery moved 3" further forward I gave it another go.
Still desperately tail heavy (or too much incidence) as this rather embarrassing video shows!

Plenty of power and managed to get it down ok.
My feeling is that it not primarily a CofG problem (which is at 27%) but rather there is too much incidence (decalage). Although the tailplane is at zero to the fuselage datum the wing is set with significant incidence.
Nor really possible to change the wing incidence without virtually destroying the plane so the only other option is to alter the tailplane.
By cutting the tailplane free from the fuselage and enlarging its slot it was possible to alter the tailplane incidence by a couple of degrees.

At the same time a slight L to R mismatch in the tailplane dihedral was corrected!
So it can now be tried again.

I agree with your analysis Q. If it were a C of G problem, the model would depart down as well as up, but she always tends to pitch up as the speed increases after a stall.

Looks nice in the air, though, and the flying speed is good too.

Well done you!

Flew the Canberra again today with the reduced tail incidence, battery full forward and 0.3oz of nose weight.

Much better but still tending to tail heavy making it very sensitive on the elevator.
Note the radius of the loop and it was still not with full 'up'. :woohoo:

The battery needs to go further forward some more but this time with a new hatch in the nose.
A bit of rather drastic surgery to remove the old battery 'tube'.

One advantage is the old hatch can be sheeted over which will restore the full fuselage strength at a critical point although a small hatch might still be left over the radio just in case it has to be 'rebound' at some point.
Worth noting that I was quite happy to completely 'build in' a 35meh crystal rx - they never needed touching.

With the ESC lead extended the fuselage skin can be replaced leaving just a thin aperture for the battery.

The battery hatch will be front hinged so even if it opens in flight it will not be a problem on landing.
A small hatch has been left over the radio.

Just had to make use of the calm conditions to test the new battery position.

It now flies well enough for low passes for the camera but it is still very twitchy on the elevator.
I have a concern that the elevator is actually twisting (it is only 2mm Depron sheet) under the effects of the scale aerodynamic counter balance it each tip. Although the counter balance area is modest compared to the total elevator area but if the elevator it flexible it may be causing a degree of 'over' balance particularly at the initial deflection.
I could simply cut off the counter balance area and fix it permanently or rebuild the elevators with a higher torque resistance.

To test the theory of elevator flexing the counter balance areas were cut off and fixed to the tailplane.

As I hoped it did indeed tame the elevator response quite a bit probably from both a reduction in flexing and also the reduced area.
It now flies really quite smoothly particularly with the low rate set to 80%.

It also glides amazingly well.

I wonder how well the concept would scale up? - 70mm EDFs, 74" span - but I simply don't have the space - unless I crash and write off a few! :woohoo:

Simon Nice to see your efforts rewarded, a super job.

Well done Q!

I wonder if it's now worth taking the C of G back to see where you would have been with the less twitchy elevators?

I did put the Canberra's figures into this CofG calculator and it calculates my current CofG gives a 7% Static Margin so I don't think it could go back very far before it would upset the handling characteristics.

Its now been flown six times (total about 30 minutes) and so far without any damage. As it has very limited crash tolerance I am tempted to stop experimenting and leave 'well enough' alone.

I will resurrect this thread (the build started in 2014!) to cover the repairs to the Canberra.
On the 21 March 2019 in looked like this.

Today, 20 Mar 2019 repairs have got this far.

The nose is almost fully put back together, the crumpled bit of Depron have been simply glued back in place. Just a few bits of missing skin are need.
The wing is structurally repaired so just needs tissue 'patches' top and bottom.
Some painting to cover the repairs will give it an appropriate "well used" look.

In Feb 2015, Ex-member (whoever he was!) wrote - I wonder if it's now worth taking the C of G back
I suspect he meant forward - forward is safe, aft is not!
Remember the old saying, a Forward c of g flies badly, and an Aft c of g flies once! [badass]

Haven't you missed a bit here Q ? ..... the thread doesn't say how it got broke, it jumps from you leaving well alone to you putting it back together ...... have I missed something? :lol:

Pol.

It's in the 'Been Flying' thread, Phil.

Sorry Phil.
To be honest after the crash which seemed to be control related I was not sure it would be worth repairing so it went in "Been flying" however, all the electrics seems to be sound so the repairs have been added to the original build thread.

The tissue paper goes on.


Being water based Easy Dope is safe to use with Depron.
Nearly there.

On another forum there was a discussion on the problems of making a practical outdoor RC plane under the 250 g 'registration' weight limit in the USA. With its 850 mAh 2s battery the Canberra weighs 247 g.