A Depron Airbus A350 - 1000 for 76 mm EDFs

Started to create the wing ribs for the inner wing panel to just outboard of the nacelle. This bit has the most extreme taper going from 13" to 6.5" in less than 12".
The wing section also changed as well, 16% t/c ratio at the root to 10%.
I decided to make this section of the wing is a similar manner as the fuselage with "printed" wing ribs and a stressed Depron skin with a single balsa/Depron/balsa spar.

The spar flanges will be incorporated into the Depron skin.
Just to make it more difficult each half will have to be built upside down as only the wing top surface is 'straight'. There is quite significant (5 degrees) dihedral on each wing as well.

That big root wing rib only just fits on the print bed!

looks to be a lot of bracing in the ribs Simon for someone who builds with the scale at hand at all the times

BB
Although the ribs are heavily braced however each 'strut' is only 3 mm wide and 0.3 mm thick.
The resulting rib is about 20% heavier but considerably more rigid than if it were cut directly from 3mm Depron sheet.
The big advantage of this process is that the shape of each rib is mathematically generated from the same 'master' set of instructions so the profile is not only accurately maintained but is exactly reproducible. An Important attribute in this case where the first six ribs are so different in size.

The wing under 'upside down' construction showing the relative position of the nacelle.

Note the temporary Depron support for the rib trailing edges.

The LH inner wing panel fully skinned with 2 mm Depron.

The nacelle pylon has been cropped to fit into the slot.

The inner wing panel and complete nacelle weighs 98 g
Note for the wing I am using Foam2Foam rather than UHU POR. Even more expensive than POR and not quite so nice to use on large areas as it dries faster but it does dry rock hard so can be properly sanded!

Really amazing work with that printer! It would be very interesting to see the actual weight difference between your printed rib and a built-up balsa rib.

Reach
I expect you could make a built up balsa rib for a similar weight and strength.
In this case my biggest rib is 12" (300 mm) long, 2" (50 mm) deep, 3 mm thick and weighs 2.9 g. It would take some skill and time to make such in balsa and I fear it would be hard to match the 3D printer's accuracy and 'repeat' ability of 1/100 of a mm!

However such printed lightweight structures do have a serious drawback as unlike a wood (or foam) component even a minor repair is almost impossible. The only practical option is to print a completely new whatever bit it is and rebuild the structure around it.

Today I printed off all the components for the other engine nacelle, about 4 hours worth.

However compared to the trial and tribulations of designing the first it is a joy that everything fits - first time!

Just for interest I printed out these two ribs.

The big one is the section at the wing root.
The little one is not the flap or aileron it is the tip! The curled up 'winglet' outboard of that and is even smaller!
At this scale such a tiny wing it seriously inefficient. The only advantage of the taper is that for its span the inner portion of the wing has relatively plenty of 'girder' depth to support the engine nacelles.

The other advantage would be the fact it will look like the original, so we'll worth the effort, great thread Q.

With no ribs or spar, just shear webs, the outer wing panel really has very little in it.

The wing section is generated by carefully pre-forming the wing skins so when both are glued on the result is the required section, hopefully!
Towards the tip the wing chord is so narrow the section will change to fully symmetrical to reduce drag.
The actual wing tip will be sanded from a 'blank'.

A lamination of 4 layers of 'formed' 2mm Depron glued together and held with rubber bands over a cardboard tube to dry.
The blank only weighs 1.2 g and much of it will be sanded away. It will be pretty delicate with no crash resistance but then neither has the wing it will be fixed to!
Every part of the wing has been cut out in duplicate so hopefully the other half will be a bit quicker to do.
With the ducted props being much lighter than the intended EDFs it looks like the A350 should come in a bit below the target of 24 oz (680 g) but at this stage it is hard to predict by exactly how much.

yet another one of your fascinating builds Simon.

you do know how to pick interesting subjects.

Tony B

Tony Thanks for the kind words.

The A350's 'trade mark' curled up wing tip.

The complete outer panel with a top hinged scale sized aileron.

Under test with a 3.7 g sevo. It has lots of "mechanical" differential in the linkage.

The complete outer panel (less paint) weighs 20.8 g.

The LH outer and inner wing panels joined.

The RH wing is coming along slowly.
The half wing and the complete nacelle combined weigh 120 g so 240 for the full wing.
The empty fuselage is 98 g
The battery weighs 100 g
Total so far 438 g
Tail feathers with 3 servos, wing to fuselage fairing, ESCs and rx all for 120 g? giving an "optimistic" all up of 560 g (20 oz). Possibly!.

The number of bits is slowly rising.

Although the one piece wing will be detachable the fact that it is swept and includes the engine nacelles means it will still take up a quite a bit of space - which I simply don't have!

The tiny 20A 4s OPTO ESC - no BEC.

It has no heat sink so I was a bit concerned about cooling.
I tested one of the ducted prop nacelles using it on a 4s.It draws exactly 6A at 14.4V (90W) and it did not disintegrate! I need not have worried about cooling as the ESC was barely warm.

At only 6A full power I can use thin 16 AWG lacquered magnet wire from the motor to the ESCs and with a total of 12A it will only need a single 1200 mAh 4s. .