English Electric Canberra - in Depron of course

If you go back through the threads I did consider building a Canberra but with 55mm EDFs in scale ducts it was rather bigger than I wanted so I eventually built the Fairey Delta 2 instead.
As the Q400 is nearly complete I thought I would resurrect the idea.
I certainly don't want to compete with Tony on size so I will go the other way as I just happen to have a couple of 35mm EDFs going spare!
Still at the planning stage but I think it will be a B2 - simple cockpit canopy and all black underneath.
First task is to produce an 'outline only' 3 view.

This is a reduced size version for downloading, the original file is 50 times the size!
Each 35mm EDF weighs just 12.5g!

Not worked out the size in detail but it will be about 30" span.

RC or FF Q? I'll look forward to it either way.

lovely looking aircraft.
good choice.
go as big as you like sir.
i thought about one of these but went for the meteor instead.
cant wait to see how you build it.

It will have to be extremely lightly built to stand any chance of flying. but hopefully its 'compact' layout will make this possible.

My first task will be to build a 'test' engine nacelle to see how much thrust is lost in the ducting.
HK no longer seem to stock the version I have with a 10200kV motor but I doubt the thrust will be much over 2oz at 6A.. At that sort of level I can't afford to loose too much as small planes are notoriously inefficient aerodynamically (even a Canberra!) so a thrust to weight as near 1:1 as possible is the target.

The next task is to decide if the EDF should go at the back or the front of the nacelle. I can see different advantages in either.
EDF right at the back like this.

Has the advantage than the inlet duct is twice the area of the FSA which should reduce the duct losses
but with the jet pipe at 35mm the airframe is rather larger than I had intended at 40" span. Keeping such a large airframe to no more than 6oz ready to go seems a daunting task.
Putting the EDF right at the front of nacelle - which a quite a bit bigger means than the overall scale size will be a bit smaller (about 35" span) and it has the advantage the the EDF spinner would be a reasonable representation of the Avon's inlet 'bullet'.
The down site is that virtually the entire length of the nacelle is the exhaust tube. With an area of the FSA it would long and narrow, just 30mm dia, so I fear the total duct losses would be significantly higher than with the EDF at the back of the nacelle.

Still thinking........

Q.A few years ago I was interested in building a Canberra for PSS and I looked at the Greenair Designs version which is in foam but a bit bigger than your version.
It was too expensive for me and I eventually built their F101 Voodoo but I never got round to flying it. I will put a picture on my photo site.......

It might be worth looking at their website to get some ideas of scale.
Coincidentally I have just bought a s/h book by Roland Beamont about testing the Canberra and other great UK aircraft prototypes!

I have doodled a version of a Canberra nacelle with the fan right at the front.

As I hoped it allows the overall size to be reduced by 15% but that long small exhaust duct (27mm diam!) would sap quite a bit of thrust.

And I just happen to have found a 27mm diam broom handle that would make a nice mandrel.....

Having checked my sums again it appears I was wrong.
For a 30 mm EDF at the front the exhaust tube is not 27mm but only 22mm!
This a good as it means I can use a piece of 22mm plastic pipe as the mandrel.
At that size the Canberra will have a wing span of 28.4" (720mm)

The EDF nacelle is shown in 'stright' plan view although in reality the whole thing is canted nose up.
It would have a wing area of just over 1 sqft so if I can keep the all up weight to 4oz it would stand a chance of flying reasonably well with 3oz static thrust but it will have to be one heck of a light weight build.

Good luck!

My intention is to make the exhaust tube from paper over a complete mandrel. The nacelle will then be built up (formers and planking) around it in 2mm Depron.
When the nacelle is complete the mandrel will be withdrawn forward and the EDF inserted.
If this method actually works the mandrel can be used again for the second nacelle.

The paper tube will be entirely supported by the Depron and will hopefully produce a smooth inner surface for the high speed airflow.
The inner tube could also be made of planked 2mm Depron, as I did on my bigger Fairey Delta 2, so the question is how much lighter would paper be?
A small test using my jewellery scales

A useful saving particularly when you take into account the weight of the significant amount of glue planking construction requires.

Hi Q
That ruler looks like it belongs on the Antiques Road Show, is it a family heirloom ?

Its a good 'Imperial' rule with 1/16 and 1/12 scales on the front.
1/10s and those new metric units are relegated to the back!
Unfortunately it is broken in two.

So a bit further to test the proposed nacelle construction technique
a. To make a paper tube on the 22mm mandrel (actually a piece of plastic central heating pipe)
b. To glue 'ring' formers onto the paper tube.

Fiddly but it seems to work quite well.
Even 2mm Depron is far too strong and heavy for some the airframe. The fuselage probably will have to remain an all Depron monocoque but parts of the wings could be tissue covered.
A comparison of 2mm Depron and acrylic sprayed 'Modelspan' lightweight tissue.

I have in mind a conventional built up 'D' box wing structure but all in 2mm Depron with its rear panels tissue covered.

sounds very complicated to me Simon.
going to love watching how you manage this one.
you will i know, but will be great fun watching you succeed.

It will be interesting to see how you decide to pass the main spar (if there is one!) through the nacelles!

The 'spar through the nacelle issue' was one of the reasons I choose to start with the EDF at the front configuration as it gives a small diameter thrust tube so has deeper formers to support the nacelle skin.
There will be no spar as such. The 'D' box wing leading edge, going back to 30% wing chord, will be plenty strong enough just in Depron and it will be simply glued directly onto the side of the nacelle.
The target weights are
EDFs 1.0 oz
Rasio, servos and ESCs 0.8oz
LiPo 1.2 oz
Airframe 1.0 oz
Total 4.00 oz