A light weight EE Canberra

The lightweight brushed Meteor has flown a tiny bit but it is really not suited to outdoors and the current weather!
Having bought (by accident!) two brushless 30mm EDFs (CW and CCW) I originally thought of putting them in a bigger Meteor and printed a "test" nacelle.
 
Not entirely happy with it so decided to make a Canberra PR9 instead.
   
The long thin Avon creates a much better nacelle for an EDF particularly if it is placed right at the nose so the bell mouth is retained.
I rather hoped just modifying the Meteor nacelle stl files to suite the PR9 would be relatively easy.
A CAD image of the PR9 nacelle.
 
An "exploded" view of its 5 parts.
 
The middle bit is specifically strong to carry the spar loads around the duct. The other parts are just hollow single wall tubes.
The first nacelle printed in LW-PLA.
 
I don't have much 2mm Depron left so I may have to print part of the airframe.           

A "short" video of the printed nacelle on a 850 mAh 3s (the likely flight battery).
www.youtube.com/shorts/J-cjtip5HEA
It delivers about 90g static thrust.
The calculations indicate the finished PR9 with have a span of 30" (760mm)

I did build a sub 250g Canberra B2 some time back (2016) entirely out of 2mm Depron as it was then available from Webbies. It also used 30mm EDFs and flew remarkably well.

I still have  it but I converted it into a NASA Martin B57D.
 
It was then virtually uncontrollable! 

A bit more on the PR9.
Both nacelles printed, EDFs added and the nacelles held in their correct relative positions by a printed spar.
A test run to more or less to see what happens!

Together on a single 1500mAh 3s they draw 12.3A (130W) and generate 175g of thrust.
To stand much chance of keeping the total weight to my target of 250g I really will have to get some more 2mm Depron - somehow!   

First I have reprinted both nacelles   as I decided the spar attachment was to far back. I also change the spar construction to a box with lengthwise printed top and bottom with 3mm Depron sides. It is nearly 50% lighter than the all printed structure.
I have also printed out the plan (7 sheets) to the required size but they are not yet taped together.
 
Both its span and length will be 31" (790mm).
Just waiting for some 2mm Depron.
Hopefully it will come out just below 250g. Not that it makes any difference now!  
 

Made a modest start on the fuselage just the bit ahead of the spar.
To save Depron the fuselage formers are printed in LW-PLA.
 
It certainly helps that all the fuselage formers in a the Canberra are true circles!

Planking with 2mm Depron is slow and fiddly but some progress has been made.
The completed nose section with its printed nose cone and the set of formers for the rear fuselage printed out.
 
The rear fuselage is even longer than the nose so still more planking! 

I took this picture for no reason other than when the fuselage is joined everything will be hidden!
 
I did consider building it with no cross pieces but as a belly lander I thought having vertical impact stiffness was a good idea.
It also neatly displays its true stress skin construction as no other part of the structure resists bending or torsion  .

At last some real progress! The completed planked rear fuselage section actually joined to the nacelles via the box spar. 
 
But it will have to sit like that on the corner of the bench undisturbed until the glue dries! 
The nacelles are set at the Canberra "nose up" angle relative to the fuselage datum.
 
Outer wing panels next.

  

The parts made so far with the plans for the outer wing panels to give an ide of the size. The span will be 32".
 
I have in mind to make the outer wing panels a LW-PLA/Depron composite construction but I will have to wait for some more eSun LW-PLA to come from China.
I do have a reel of ColorFabb LW-PLA but compared to the eSun it "foams" a good bit less and needs a higher flow rate so "like for like" it is heavier.

I shouldn't grumble because I used ColorFab to "vase" print all the parts of the Canberra nacelles with no problem.

Today I spent a ridiculous amount of time test printing the leading edge portion of the Canberra outer wing panel using the CURA lofting process to automatically create the surface from one size shape to another.
  
Left is the first simple print showing the scale symmetrical section reducing from root to tip. Looks nice but not nearly stiff enough.
Middle is the first attempt at including a diagonal braced box spar that also reduces root to tip. Plenty stiff enough but it leaves too much unsupported skin. 
Right is the final version with internal diagonal bracing to support the skin. The whole structure acts as a "D" box spar and is really stiff in both bending and torsion.
The "D" box just resting in correct position against the nacelle.
 
The rest of the wing panel will be built from the "D" box with an almost conventional open rib structure in Depron. When complete with its aileron servo in place the servo wire will be fed through the nacelle and the wing simply glued on. It will then be tissue covered.
What really took the time was to find a way to kid CURA into "vase" printing what is a complex "multi cell" structure. Vase printing normally only follows the outer surface and ignores the rest.
Of course the simple solution would have been to use a gyroid fill but I would then have lost the quality benefit from vase printing.
Nevertheless I suppose I should do one with a gyroid fill as a comparison for both stiiness and weight.        

I had a go at Vase printing. I thought it would be usefull for ailerons, especially the hinge edge.
It didn't seem to do what I'd read, ie. just go round & round with no seams; maybe it was the design.

 

Yes
Vase printing normally ignores any internal structure. To work correctly the outer surface also has to be uninterrupted. Even a double thickness wall is ignored and printed as a single.
This is why basically circular prints "Vase" print so well.

It is possible to "trick" CURA into vase printing a complex structure by arranging that no joints actually touch but are so close that when printed the two surfaces actually melt together. It does take quite a bit of trial end error to find the correct gap.
Even then it is not always possible to arrange the whole structure to be printed as a single continuous path.
A video of the vase printed wing.
youtube.com/shorts/GebG4BVHksA
It took nearly a full day of experimenting to eventually achieve the required print!   

 

Yours isn't doing a continuous spiral either but you seam to have the seams under control or have you cleaned them up? Are the gorilla grunts the machine changing layers? My machine will only go up to about 110mm, yours is obviously much taller.
I thought the nearest one with just an ellipse & circles would do it but maybe because the outside is half an ellipse & an arc stops it.
I'll do another one with a whole ellipse and circles.