A350-900 70mm EDF 1:40scale scratchbuild

[mrdepron]

The skin will be the paper looking thingy which i bought from Sydney.i have sanded the formers/ribs to the shape of the original,then 1mm lesser for the skin.

I will be releasing a profile jet version of the A350 at the original size after i finish the fuselage,wings and stablizers.

*A profile jet's fuselage is in the shape of a '+' just like the Concorde below.

[mrdepron]

Hi viper, we are holding the 'best scratchbuilt airplane'. I have seen all your builds including the GIANT F16.You might want to enter the competition. Just send at least 3 photos of the chosen plane to communityrcsg@gmail.com

[viper1990]

Thanks for the invite, Send me the Date,time and venue via PM and i'll revert to you after i check my schedule calender.

[viper1990]

Prepping The Underbelly

Before the wings could be built, some minor prep-work is needed for the underbelly as the wings will be constructed on the belly itself as a one-piece wing. One-piece wing is preferred instead of building a 2-part wing is because it will have more structural strength as there will be one thick spar embedded in the belly holding both the right and left wings together. Most importantly, the 161.8cm Wingspan was able to fit in the backseat of the car!

Below shows the step-by-step construction of the underbelly main landing gear-well construction. There will always be rough and jagged edges after the hot-wiring process and will be putty-ed and sanded to shape afterwards. The gear door was originally a piece of the underbelly and the door thickness is 3mm.

Last step was to test fit the main landing gear by placing it into the gear-well, the space between the wall and the main wheels was roughly 5mm which was spacious enough for the gear to swing in and out. I'm happy with the results at the end of the day.

[boonyeo]

https://www.facebook.com/video.php?v=378553885637884&video_source=pages_finch_main_video

[mrdepron]

I might try a Lipo pack instead of the Li-ion which i built from my old laptop.It caused 2 incidents, 1.my boeing 747. While flying, the battery burst into flames and burned the esc and i was landing it with flames at the tail.(I have 2 747s, a micro, which is about the same scale as my version of the A350 and a 1:50 which was in this incident.) My father fetched a bucket of sand and poured it over the tail. 2. Yesterday i was flying my Concorde which was in the BOAC livery. Then,it happened.It burned and i flicked the switch to release the equipment box (i designed the plane and built it badly. I finished the fueslage and forgot about the electronics bay. So i fitted a servo released box into it.)This time, only the esc and battery caught fire. I had to reconstruct the box. I wonder anyone filmed my 747 landing. It was spectacular.

[viper1990]

https://www.facebook.com/video.php?v...nch_main_video

Ah yes, the famous helium filled A310 by Martin Müller. It has been the "talk of the town" in many hobby forums including daddy hobby back in 2011. http://www.daddyhobby.com/forum/showthread.php?t=66163

The amazing thing about this plane that it was only 350grams. The helium manage to lighten it by 40grams from its initial 390gram weight.

Shocking fact,the 2X EDFs with motor im using already weighs 400grams!

[viper1990]

I might try a Lipo pack instead of the Li-ion which i built from my old laptop.

Please exercise caution especially when using a battery pack not meant for high discharge such as your laptop battery. I highly suggest you to just buy a lipo pack specifically meant for your rc-model. Carefully plan and decide which type of battery to buy.
Plan the following values correctly and you can optimize the performance of your model. It'll take some experience to select one, but you will be an expert in no time over trial and errors.
1) correct cell size x S (depending on your motor rating)
2) capacity xxxx mah (depending the extra payload your plane can carry)
3) discharge rate xx C (is there a constant need to go full-throttle for that extra burst of energy?)

[Super-Hornet]

About using the Arduino for your navigation light, recently I tried to use Arduino Nano for powering a range of Ultrabright (2mm) LED but I find that the Atmel microcontroller easily turn hot when running it for like a minute.

My recommendation is that, your Atmel o/p is connected to a LED driver and the LED driver will use it to drive the LED light.
U can either look for LED drive DIP chip or maybe using 74series logic chip of inverter or buffer.

[viper1990]

Hi Super-Hornet,
I've tried both Arduino Nano and Arduino Uno and i agree with you that the Nano will overheat if the I/O pins are overloaded (typically 40ma for each pin). The Arduino Uno seems to have more tolerance to overheating as i'm using the ATMEL-ATmega328 chip , not the surface mounted version. So the micro-controller i'm using now for driving the Nav lights will be the Arduino Uno.

I've shared my schematic online and i got a recommendation such as using N-channel logic level MOSFET to drive the LEDs as it measures voltage level to turn the lights on and off instead of current ,thus draining virtually nothing from the I/O pins. See post #42 onwards: http://www.rcgroups.com/forums/showt...2263665&page=3

Both yours and his idea are almost identical, which is to draw as little current as possible from the Arduino board to stop it from overloading and overheating. Thanks for the suggestion, i've still got lots to learn from you guys and the learning possibilities in this hobby are endless! I'll look into my electrical schematics again after i'm close to finish with my build.

This is my wiring diagram, I've excluded the gear-door sequencer as it shares the same board with the nav-light else it'll be too messy to see. What do you all think?

[viper1990]

Attaching the Main Landing Gear

The Main Landing Gear will be directly attached near to the root chord of the main wing, between wing rib #1 and #2. After-which it will be covered with (3mm) depron panels. The location of the Main Landing gear is important as I wanted it to sit slightly aft of the aircraft CG. The reason for that is to ensure smooth rotation when the aircraft hits take-off speed. If the Gear is placed too near the CG it will pitch up easily during the take-off run, stalling the aircraft early. If the Gear is placed too far aft from the CG , the plane will have a really hard time to rotate or might not even lift off the ground at all.

This was where the initial chuck-glider test came handy to pin-point to me the correct CG location of this particular model. Though the Chuck-glider had different Airfoil-Camber,Thickness and other variables, the CG location deviation will be very small. The most important factors determining the CG location would be the wing and horizontal stabilizer dimensions and the distance between the both of them. So I can conclude the Chuck Glider A350 CG and this 1:40 scale model have similar CG location.

Back to the build, Airfoils were cut out followed by spar-slots and landing gear slots on Rib #1 and #2. CF 8mm square spar was skewered through the belly to serve as the main spar to hold both wings. Paper peeled off from the Airfoil to reduce excess weight.

The tricky part was to design a hard-point for both the main-gear to channel the aircraft weight directly into the main spar and act as one solid piece all-together . This was to prevent Ribs #1 and #2 from snapping subjected to excessive load. A simple solution was to strengthen the rear half of the airfoil with 2mm plywood so the load will be transferred directly from the main landing gear to the CF spar. It will be still prone to breaking but under higher loads now .It will be sustainable under proper and smooth landings.

Did a gear-retract dry run without doors to test the fittings. I've did up to Rib #4 for now. Rib #5 will take some time to make as it will be a thick plywood that will holds both EDF engines to the main-spar.

[viper1990]

Balancing the 70mm 10 blade EDF

There are several guides i've read on balancing EDFs, here is one that really caught my attention but i didn't went to that extent to use a cell-phone to help balance the fan. http://www.rcgroups.com/forums/showthread.php?t=1267814

Most cheaper fans online will always claim that their fans are dynamically balanced, but as a regular user on EDFs, i had never received dynamic balanced fan that are ready to pluck and fly except my Wemotec 68mm fan which is easily 4-6 times more costly than the cheaper fans.

I spend about an hour each balancing each of the two EDF i have for my A350. I don't think i could explain in details how i did it in words so i came out with an illustration on my method.

End-result: An awesome almost-turbine like swooshing suction sound effect as claimed by the many hundreds who have used this fan before.

[viper1990]

Wing construction and engine mounting

The EDF was screwed onto the pylon mount with 2mm tapping-screws. I will change to a 3mm-nut-bolt in the future as this was only temporary to test fit the EDF.

At my previous post, I've left off after completing Rib #4 as Rib #5 would be slightly more tedious to make.

Rib #5 was made out of 3mm plywood which will be holding the 10bladed 70mm EDF. Also, Rib #5 was the last airfoil rib epoxy-ed onto the main CF spar. A second 6mm diameter CF rod was skewered through ribs #1- #10 to have added stiffness. The CF rod was placed in the wing from root to tip,full span. Reason was,I had encounter one bad experience when i once had a plane with CF rod spanning only up to mid-wing,the wings snapped in air when banking hard although it seems that the wing was really strong on the ground. My lesson learnt was not to be stingy and save carbon-fiber rods.

Wing specifications:
Washout angle: 2° from root to tip
Dihedral angle: average of 5° from root to tip. (Dihedral angle is steeper at the root and shallower as it spans out)

[viper1990]

Constructing the main-landing gear system

The wing panels are first glued on the under-side of the wings using uhu-por ,I found it a less messier alternative to epoxy for this scenario. As uhu-por works like contact glue, it gave me time to slowly apply on every surface, when ready, i preposition the panel above the ribs and push them together. It instantly bond to the ribs when both surface touches.

Gear doors drawn on the panel and cut out afterwards. Note that in my design, there are 2 gear doors on one side. I'm not familiar with the technical name for them, the main-wing door should be called fixed-fairing and the tiny door is called the hinged fairing.

i've googled for the door names here, I'm calling out to anyone who can confirm this? : http://s94.photobucket.com/user/Jet-...a/323.jpg.html

Thesmaller door had no servos actuating it's movement and it was "spring" loaded with a rubber band. It is open when the main-wing door pushes it and closes when the rubber band pulls it back. The reason for the smaller door was due to the closed-position of the wing gear,it leaves a small gap open in the wing. The only way to cover that hole up was to design a second pivoting door. The actual A350 had the same gear-door design.

Here is the video of the main gear and full retract system working.

[viper1990]

Flaps Fairings Construction

Flap Fairings are the pods located on the underside of the wings. They are made to streamline the flap mechanism that extends and retract the flaps. Different types aircraft have different number of pods, in this case, the actual A350 has 3 on each side. Fowler flaps was the type of flap system the A350 used, one of the advantage for this system is that the wing area increases when the flaps are extended.

Had been cracking my head on this one on which type of flap mechanism i should go for, the flap tracks or the hinged-flaps? what sort of complexity will i face between the 2 options? I eventually went for the Hinged-flap option (Refer to picture)

Option 1) Flap Tracks is definitely more rigid but precision cutting is required for the tracks to slide smoothly back and forth, i would have went for this choice if i had a 3D printer or a milling machine.

Option 2) Less complex to construct and i feel that this option will be less prone to jamming as it rotates on the axis rather than sliding and rubbing between material surfaces which might cause wear and tear.

Choice of material will be blue foam and wood where strength is required. The flap fairings itself will be the hinge for the flaps. It's range of rotation angle will be from 0° to 45° before it feels stiff and difficult to push beyond 45° due to the design limits. The Actual A350 also had a 45° limit for it's flap max angle.

Pictures will further illustrate how the flap fairings with hinges are made. For my next post i will try to get the full working flap mechanism up and running.