Airbus A350 for 50 mm EDFs

[Colin Leighfield]

It’s really taking shape now Simon. Have you thought about how you will do the hand launching, will it be the under-arm technique? That’s the bit that always worries me, where exactly to hold it for a safe chuck into the air!

[Stephen Jones]

I think Simon is going to have to throw this one over arm above his head.

And i bet it is going to look awesome the sheree size of it.

Keep up the good work Simon i have been watching this one with much interest.

Steve

[Simon Chaddock]

How will it be launched?

Well certainly over head! Its not the weight that is the problem but how and where to hold it.

There is quite a large flat sided area under the wing to contain the U/C on the full size so there is a chance that will provide sufficient surface to get a grip. It has the advantage it is also in about the right place.

And there are two NACA ducts in just about the right place for cooling air to the ESCs.

[Simon Chaddock]

Whilst I am quite happy to use top tape hinges for both the ailerons and elevator (you are likely to need more up than down on both) a tape hinge is not so suitable for a rudder where equal movement is required.

This requires a suitable hinge. The rubber has nearly a 3:1 taper so varies in thickness by the same suggesting different size hinges are required. Another print job!

After several attempts this was the final design.

Two identical parts with a separate 'stepped' pin that is free running in one and tight in the other. A dab of glue on the tight hinge face ensures the pin does not work loose.

This is then printed at 100 , 150 and 200 % to suit the rudder thickness.

Free running and surprisingly strong.

I think I can make some balsa shrouds to reduce the hinge gap.

[Simon Chaddock]

After much thought I finally decided on how to mount the rudder and elevator servos. Each elevator half has its own servo.

The rudder is conventional enough with the servo buried in the fin but the elevator servos are stacked one on top of the other under the tail plane. This has the advantage that the servo will be inside the fuselage but the horn centres are different so it took a bit of trial and error to get equivalent elevator travel - well almost!

Now I have just got to start putting the pieces together.

[Simon Chaddock]

It is always a bit alarming when you have to cut open a perfectly good fuselage but its the only way to get the tail on however it givee an idea of what it will look like.

Nothing fixed just balanced in place but ti do look about right.

There is still quite a bit to do to get it so that is properly fixes together.

 

Edited By Simon Chaddock on 18/12/2017 21:49:46

[Martian]

Ye gods that is wonderful a real credit to your skill with 3d printing and depron

[Simon Chaddock]

It has been a rather slow build with a quite a bit of 'development' along the way but with the major structural components now complete it has turned out rather better than I dared hope.

Although it appears to be made exclusively from Depron (virtually all 2 mm with only a tiny bit of 1 mm balsa) it does actually contain no less than 54 different 3D printed parts. Some are used more than once (there are two identical nacelles) giving a grand total of 84 - so far!

I wouldn't like to even think how many bits of Depron -probably in the hundreds!

[Colin Leighfield]

You’re a pioneer Simon. Something of a hero as well!

[Simon Chaddock]

Pioneer? - maybe a little bit. Hero? - hardly!

With Christmas looming things slow down a bit but the tail in now permanently fixed and the elevator and rudder servos wires run down the fuselage and guess what they are retained by printed cable clips!

.The ESCa are located in the fairing under the wing. It a bit of a 'sardine can' tight fit.

The BEC and rx will go a bit further back and for CofG reasons the battery further forward but if it all goes to plan everything apart from the rudder and elevators servos will be in, or under, the wing.

[john stones 1 - Moderator]

It is wonderful you're correct, love the curly wing tips.

[Simon Chaddock]

I am probably guilty of using printed components simply because I have a 3D printer but it does allow critical but bespoke structures to be precision engineered without hand fitting, indeed I am not sure I could make the required bits lighter by any other process.

The issue with stressed skin structures is that there are no 'natural' strong points to place wing bolts without adding extra structure and weight.

This odd looking thing is the fuselage part of the wing retaining structure.

The two formers are shaped to exactly fit the inside of the fuselage skin. Sandwiched between them are two M4 threaded 'blocks' to accept the nylon wing bolts. The whole structure weighs 1.6 g

The bolts pass through similar full depth blocks glued to the wing spar and the inner rib.

A third bolt using a similar mounting arrangement will be on the fuselage centre line close to the wing trailing edge.

Once the wing is mounted then comes the task of creating the .wing to fuselage. fairings, if I can find some decent pictures of what they actually look like!

[Simon Chaddock]

The "electrics" more or less complete.

Except the RH ESCs is faulty!

Strange it runs perfectly on 2s (which is what I tested both of them with before installation) but on 3s or above the motor just oscillates. The other ESC works fine no problem. A replacement is on order but it has to come from China!

The battery (1000 mAh 4s) is part buried inside the fuselage but its battery box is still part of the wing so everything but the elevator and rudder servos are mounted in the wing thus the main part of the fuselage has nothing it at all!

[Simon Chaddock]

With the wing fairing complete the wing can be unbolted and carefully "pried off" the fuselage.

This shows the battery box with a 1500 mAh 4s mounted in front of but still part of the wing.

It fits in a "hole" in the fuselage.

This is about as far as I can go until the replacement ESC arrives.

[Colin Leighfield]

Take a breather while you’re waiting and dream up the next impossibility that you are going to make work. A Me321 Gigant might be too simple. What about a Focke Wulf Trifugel? Projects I fancy but am totally incapable of doing.

[Colin Leighfield]

I got so carried away with trying to think of something difficult I forgot how to spell. I just had a look and the Focke Wulf idea was of course the Triebflügel. I can’t think of a practical way to do it though!

[Erfolg]

The impracticality of low thrust engines is most probably part of the reason it never got past the idea stage. Also the reason it almost certainly would not work with current DFs.

[Simon Chaddock]

A Triebflugel is a interesting idea but even if EDFs at the blade tips had enough power just think of the gyroscopic forces that would be created!

Given that a gyro wants to move at 90 degrees to the actual displacement even with helicopter type cyclic pitch control would be problematic to say the least.

The Rotordyne managed because it only needed light 'rocket' nozzles at the rotor tips burning fuel with compressed air taken from the Napier Eland turboprops.

I think I will stick with planes that actually flew!

[Simon Chaddock]

At last the replacement ESC has arrived but it needed some fiddly soldering to get it in.

Doesn't look very different than before but now both motors run on a 4s.

I also changed one of the props as it was horribly out of balance. A small 4 blade is hard to balance.

Once the wing and fuselage are put back together I will do a nose down thrust test on the kitchen scales, hopefully close to 16 oz thrust which should be "adequate" for its 21 oz all up..

[Simon Chaddock]

The tail painted loosely following Thai Airlines scheme who were one of the initial customers of the A350 - 900. Fairly simple as the rest of the entire plane is white.

Taken with a flash so the purple comes out rather blue.

As a an experiment, and to save buying any more paint, the narrow gold and pink stripes are done with self adhesive "Fablon". Probably a bit heavy but there is not much of it.

[Simon Chaddock]

After a rather nasty bout of flu (painting and coughing don't mix!) it is now virtually complete.

Just the cockpit windows to do.

It may look like it is made mostly of Depron, which it is,  but it has over 50 individual 3D printed components that have been used where particular strength, shape and repeatability are required.

It weighs 595 g (21 oz) ready to go with its 1000 mAh 4s.

I can see that all the controls work in their correct sens but 'jerking' a big lightweight plane around to show the stab functioning in the correct sense is not so easy.

In any case its maiden will have to wait for both ideal weather conditions and the grass to be cut so not likely any time soon! .

Edited By Simon Chaddock on 22/01/2018 15:01:34

[Erfolg]

It will be very interesting to know what the maximum wind speed it can handle comfortably. Although I guess that the wing loading is not as low as the all up weight suggests.

At first glance I would be thinking are there inertial issues with such a long nose, but I guess the bulk of the mass is concentrated near to the CG?

[Simon Chaddock]

Erfplg

The masses are indeed concentrated close to the CofG. The fuselage is so light I doubt its inertia will be significant particularly with its fairly generous tail moment,.However there could be some aerodynamic effects of the long fuselage at the more extreme angle of attack that models can achieve.

Of more concern is the roll inertia of the relatively heavy motors on the wings coupled with its modest ailerons and rather flexible wings!

[Erfolg]

Has I am guessing the lack of torsional rigidity surprised you, on completion? Or have you accepted a less than stiff wing as a price of keeping the weight down?

I can envisage that aerodynamic issues will always be an issue with a very light aircraft, with low power. I have flown models with low power, with some mass. In these cases handling in any sort of wind is not good, although the momentum and Inertia keep it going, at least on a temporary basis. The problem becomes you seem to run out of energy, if the situation continues. In my case I was glad to finally get the model down. An increase in power helps, although mass in addition helps further.

The worst case for me was back in the day, when I started gliding. I launched my glider, only for the model to go up, then to all intents and purposes became a leaf, being tossed about, until striking the ground, then turning into a Solarfilm bag of bits.

I guess it really is a really good flying day model that you have intentionally created,

[Simon Chaddock]

I took the advantage of a rare calm and relatively mild conditions a couple of days ago to maiden the A350. To my astonishment it flies really rather well.

The field was very soggy with big patches of standing water but the hand launch was easy and it simply climbed away.

It glides pretty well too such that it took me three approaches before I could get it down on a passably dry bit. The nacelle undersides still got a bit muddy but no damage!

I will video the next flight.