DH 91 Albatross

The ribs glued on to the lower skin.

Four ribs, including the big centre one, had to be reprinted as they were not quite the right size.
This would have been no problem if they had been in Depron as they could easily be 'sanded to fit' and no one would ever know!

The interesting bit, actually doing what I imagined in my mind!
The completed wing as far as intended at this stage.

It feels slightly 'heavy' compared to say the A350's wing but is admirably stiff, probably unnecessarily so, but I was concerned at the weight of the 4 motors on the wing, not for flying loads (they actually distribute the load) but in any sort of any sort of hard landing.
One problem is that with my rough grass field it will not belly land well. The bottom of the fuselage is level with the under side of the wing so there is nothing to 'slide' on. As a result it will probably ground loop very easily and likely breaking off those low mounted tail fins in the process! :woohoo: .

Now the boring bit - making the other wing, but at least I have already cut out and printed virtually all the bits.

The two wing halves joined.

In this state the wing weighs 115g which of course includes the retract inits.
Still a bit of sanding to get both halves of the wing to the same standard, then its cutting out the wheel wells to ultimately get the retracts working. .

You have a record of success with challenging projects and this must be one of the most challenging! I envy your progress with the practical use of 3D printing.

With the Big Dragon 2 rebuilt and flying attention can return to the Albatross.
I used 'printed' hinges for the A350's rudder. All the other surfaces use tape hinges.

They work well enough but are not very strong so a better more robust version that will be used for all the control surfaces of the Albatross.

The two parts simply 'click' together and it can be 'scaled' in CURA to a suitable size but below 75% the hinge 'pin' (at that scale it is only 1.5 mm in diameter) does not print well enough to retain all the required diameters.
The air frame side of the hinge will be glued to a printed rib. The other side is simply glued into a slot in the solid Depron control surface.
If possible I would like to use surfaces 'direct coupled' to the servos as in 2.4 individual centring, range of travel and differential movement can be incorporated. The 'thorny' problem is how to do the rudders in a way that is both simple and light!
The lightest of all is of course "bank & yank" (no rudder) but that might not be a good idea with the inertia of 4 motors out on the wings and with a rather modest fin area.
This could be a significant issue as on the prototype the fins/rudders were enlarged and moved to the ends of the tail plane to overcome directional control issues!

The aileron fitted with the three hinges.

The biggest problem will be keeping it free moving after it is all painted! :woohoo:

The wing at the aileron is just to thin to fit a servo directly to the aileron so it will have to have conventional horns and links with some differential movement included in the geometry.

With the servo installed the aileron can be tested.

With a conventional aileron horn on the underside belly landings are not recommended!
The aileron horn is designed to be glued directly onto the Depron surface of the aileron.
It is 3D printed.

Made a modest start on the rear part of the engine nacelles.

Slow going, planked, all in 2 mm Depron and there are 4 to do! :woohoo:
The motors and ESCs will have to be installed and all wired up before the wing rear top skin can go on.

The only question is will I go 'stir crazy' before I get to finish it!

Still slow as I keep getting distracted to do other things - chicken perches and a new base (printed!) for an outside light. :woohoo:

About 16 Depron (2 mm) planks per engine nacelle and each individually cut/sanded/formed to shape. Its tedious and rather boring!

As a break from the tedious planking I worried about the aileron servo horns sticking out of the wing underside and the possibility of them 'snagging' on any sort of belly landing. Very likely a necessity with my rough grass field!
So a printed horn cover seemed a good addition.

To allow it to be as thin as possible the cover itself actually retains the rod in the servo horn.

With a Z bend at the aileron horn end it becomes something else "permanently built in".

Great idea. What about one for the aileron?

OT
I am not sure a cover for the aileron horn would reduce any snagging.

At last I have finished all the nacelle planking.

Then there are the 4 nacelle 'tail ends' to do on the under side. :ohmy:

There are similar nacelle 'tail ends' on the wing top surface but they will have to wait until the rear top skin goes on.
The OPTO ESCs have not yet arrived so cutting out and fabricating the undercarriage wheel wells is next.

The lower wing skin cut out for the wheel wells.

The scale wheels will be 2.25" (57 mm) diameter.
Guessing from the relative size of the main and tail wheels I suspect the U/C was positioned pretty close to the CofG when in the "tail up" attitude so for a model with 'non scale' grass it may not be easy to avoid a landing 'nose over'.

The 3 view suggests the tail end of the fuselage supporting the tail plane has a very small section and is where I would suspect it would break off in any sort of rough landing.

I intend to use 'printed' fuselage formers.
The tail plane also has slight dihedral so it makes use of printing's capabilities to incorporate a tail plane spar brace into the appropriate former. This will be last former as it is just a non structural tail cone after that.

The tail wheel is also mounted at this point so the brace includes pivot pinions.
Printed braces will also be used for the tail plane to fin joints.
So far so good but I still have not decided on a method to connect and move the rudders! :ohmy:

The easiest way may be to run a normal push-rod down the fuselage to a 90' bellcrank. That changes the fore/aft to a left/right through the tailplane, then to rods extending forward from the rudders.
You could change through 90' again, for a fore/aft drive to horns on the rudders, but it's an open invitation for slop to creep in.