Hamish's Posts (6)

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Continuation of my FX-61 Phantom build configuration. (this part has the BoM at the end)3689617179?profile=original

The other wing is just stock. Look at that horrible stock servo, it’s transparency only serves to taunt me by showing the horrible plastic gears that are dying to eat each other to bits. I would like to change them ASAP – safety-wise I really think they are the weakest point in the whole system.

The 433 telemetry radio antenna folds flush with the body. Extending it does not increase the RSSI but it looks cool, and looking cool is just as important as flying well when you’re impressing people at the park.

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As much as I dislike adding weight, fibreglass tape definitely buys its way on-board! It seems that every single edge that I didn’t tape now has a dent on it :\ Taping the wingtips and rudders is essential. I always seem to bash them during transport. I laminated the LE (Leading Edge) with strips of A3 hot laminating film using a household iron. It’s not easy to get it on without damaging the foam with the heat (it bubbles up like orange peel if it gets too hot). For that reason I only did the straight sections, and will fibreglass tape the curved outboard LE section.

Ideally, about 20% chord from the LE is laminated with film and then the LE radius is covered in fibreglass tape. Alternatively, don’t crash.

The TE (Trailing Edge) never gets damaged on my aircraft.

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I use a second hand Futaba FP-T8UP, and I love it. Great build quality. It only has 7 custom mixers, but I have not run out yet.

I don’t have a 3D printer or CNC mill so thought I would have to settle for a sub-optimal hack to attach my tablet to the transmitter. Surprisingly, a headrest mount attaches easily to the Tx handle and works very well. An hour of chin scratching whilst surfing the web can sometimes pay off it seems – the mount works great and was only £5.99 delivered.

I don’t take a laptop to the field. I plan my mission at home, then use an Asus Nexus 7 tablet for telemetry while flying. Droidplanner is okay, but annoyingly it disconnects when the signal is too low but doesn’t try to reconnect. I have to manually spam the connect button, and it’s getting annoying now. Is there a solution?

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The plane balances nicely. CG is very sensitive to placement of the huge battery, but there’s plenty of space. Velcro is not enough to secure the battery, so I use squares of grippy pad on the tray to firmly stop the battery from slipping. With everything in (autopilot, video gear, no payload) it weighs 1350g.

Grippy pad is the rubber-like material marketed as a dashboard phone holder. It is truly amazing, you should get a bit just to play with it if you have never felt it. When it’s clean it sticks almost as well as sellotape when used on a smooth material like plastic. I use it to attach the radio to my tablet, because it’s not permanent and leaves zero residue.

I like to leave space in front of my battery so that in a crash it can slide slightly allowing the grippy pad absorb the impact rather than crunching into the nose and killing itself.

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The phantom has a stupid bell shaped moulding around the motor. I cut the bell shape away. The purpose of the bell is unclear to me – the aerodynamic effect of its shape is to promoted radial flow across propeller, but that reduces efficiency. Plus, it blocked the root portion of the blades.

I balanced the motor using the trim balancing technique, using a laser plus a portion of DVD taped to the tip of the rudder to measure vibration amplitude. I have not seen any videos of trim balancing being used for RC models, it seems to be reserved for gas turbines despite being rather simple. Perhaps a video tutorial is in order.

I found the stock propellers to be impossible to balance. I thought I was being an idiot, but on closer inspection I found that the plane of rotation of the blades is not orthogonal to the axis of the hub, causing dynamic imbalance. In other words, the blades can be statically balanced to perfection and the prop CG can be bang in the middle of the hub, but the blades will teeter when spun and cause vibration. I’m not just being picky, the dynamic imbalance in my blades is very powerful!

At the moment when I come in to land I have to stop the prop on approach, and hope for it to stop in the horizontal position to avoid hitting the ground, otherwise I have to tweak the throttle until it does. The sooner I switch to a folding prop the better. I will also be switching to a 10” prop in hope of reducing noise, because at the moment this model is far too noisy for it’s power.

Okay, here's the most important bit: Money! 

I worked out the cost of the drone (just aircraft, no ground equipment) as described in the above build log to be £540

The breakdown below includes some of the hardware, but also other tools and consumables. The full breakdown of absolutely everything is available upon request if you really want it.

Thanks for reading, and if anyone in Bristol wants to fly then let me know!

Hobbyking
CodeQtyDescriptionPrice USDPrice GBPTotal
374000039-01Phantom FPV Flying Wing EPO Airplane 1550mm (PNF) V2$111.52£68.58£111.52
shipping£51.81
total [USD]£163.33
import VAT & duty£24.30
sub total£100.44
Total£124.74
Hobbyking 
DFT1FrSky DF 2.4Ghz Combo Pack for Futaba w/ Module & RX$47.99£30.32$47.99
D8R-XP1FrSky D8R-XP 2.4Ghz Receiver (w/telemetry)$27.05£17.09$27.05
912700001-02Multistar High Capacity 3S 5200mAh Multi-Rotor Lipo Pack$27.73£17.52$55.46
504000014-01Mobius Wide Angle B Lens ActionCam a 1080p HD Video Camera Set With Live Video Out$72.99£46.11$72.99
504000004-01Mobius ActionCam External Lens Module Extension Ribbon Cable 65mm$3.88£2.45$3.88
504000006-01Mobius ActionCam A/V Out Cable Set$2.17£1.37$2.17
387000050-01HKPilot32 Autonomous Vehicle 32Bit Control Set w/ Power Module$147.28£93.04$147.28
387000047-01Ublox Neo-7M GPS with Compass and Pedestal Mount$32.59£20.59$32.59
9387000030-01FPV 433Mhz Radio Telemetry Kit 100mW V1.1$31.94£20.18$31.94
387000034-01Telemetry Radio Cases for Ground and Air Modules$5.11£3.23$5.11
263000020-01SkyZone 5.8g 600mw 32CH FPV Wirless AV Tx & Rx Set TS832 and RC832$95.31£60.21$95.31
263000021-01Boscam 5.8GHz Cloud Spirit Circular Polarized Antenna Set RP-SMA$25.74£16.26$25.74
HS -350D1Cable Ties - White (350mm) (50pcs/bag)$2.06£1.30$2.06
478000011-01Wing Tape 45mic x 24 mm x 100m (Narrow - Yellow)$1.05£0.66$1.05
478000010-01Wing Tape 45mic x 24 mm x 100m (Narrow - Red)$1.05£0.66$1.05
450000099-01Glass Fiber Rod 2.5x750mm (10pcs)$2.45£1.55$2.45
CF83Carbon Fiber Rod (solid) 1.5x750mm$1.56£0.99$4.68
HE-28-21HobbyKing 30min Epoxy Glue$0.85£0.54$0.85
TL-2421TL-242 Thread Locker & Sealant Medium Strength$0.99£0.63$0.99
SBEC-26V1Turnigy 5A (8-26v) SBEC for Lipo$4.90£3.10$4.90
4380000011Arduino Leonardo R3 Board Micro-USB$15.00£9.48$15.00
FRFUL11FrSky Telemetry Receiver upgrade USB/Serial lead interface$3.80£2.40$3.80
BOX-379g1Extra Length Cardboard Box and Packing 379g$0.00£0.00$0.00
shipping$62.33
total [USD]$646.67
total [GBP]£408.50
import VAT & duty£115.07
Total [GBP]£523.57

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This is a description of the configuration of my FX-61 Phantom FPV Flying Wing EPO Airplane 1550mm (PNF) V2

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The whole reason for me to get this plane was to get started with autopilots. I have chosen the HKpilot32, a pixhawk clone that comes with the same accessories as the pixhawk and a 4GB microSD installed. 

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The GPS + compass module is mounted on an anti-vib polymer that is marketed by Specialized as ‘Bar Phat’, a vibration damper for bicycle handlebars. The Mobius camera lens module is also loosely secured using bar-phat for anti-jello, and not fixed firmly so that it can pop into the fuselage if hit.

The embedded nuts are used to fasten a tray that goes over the pixhawk. I should have used metal nuts because if the nylon threads are stripped, I am screwed since the nuts are epoxied in.

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The PLA plastic is marketed as Polymorph, and is a granular plastic that melts into a malleable mass when submerged in hot water. Great for making funny shapes like antenna root clamps. The radio PCB is floating, supported by the antenna. I tried fixing the PCB using 3M VHB tape and leaving the antenna floating, but the tape kept detaching.

Note on 3M VHB: it is a spectacular double sided tape, but the full strength is only realised if your apply about 15psi pressure for a few hours – I'm too cautious to clamp a PCB to some foam with that much pressure.

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The carbon tray was freehand cut with a dremmel clone. It opens up a lot more space, leaving the whole rear volume clear. In my opinion, it’s important to have the payload area at the centre of gravity, so I don’t waste time balancing the plane when I add or remove a payload.

The VTx (video transmitter) is powered straight from the balance port, which I learned is a great way of RUINING your battery. I crashed into a tree and everything stayed intact, so the VTx carried on sapping power and drained my battery down to a few mV, since it doesn’t have undervoltage protection. So that battery is now a flammable paperweight.

I also learned the hard way that the arming switch will become gummed up with glue and seize if you just throw it into a gluey hole. So after a number of years with a scalpel I picked all the glue out, wrapped the switch case in tape then glued it again. It’s fine now.

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The fantastic Mobius camera has been a very pleasant surprise, especially considering the cost. The fact that you can extend the lens module out of the main camera is very nice! I have the camera set up to start recording & outputting video as soon as it receives power, which is ultimately from the pixhawk power module which I trust far more than the horrible noisy stock ESC.

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The Phantom v2 now has detachable wings, but the attachment solution is not elegant at all. In fact, it’s horrible! The screw is hard to align, plus it’s made of rubbish playdough steel. Needless to say, the blind nut which the screw goes into became detached, sigh -.-’ I will replace it with a chunky nylon screw ASAP.

I made quick connects using a bundle of servo extenders. It works okay-ish. The connectors are too tight to disconnect 3 at once, so I have to manually plug/unplug each one. It’s no big deal, but it’s not the simple snap-in dream. There are good multiplex quick-connects out there, but they don’t have enough contacts for a servo and a VTx. Next time I will try DSUB connectors with a locking latch.

Note the connectors are loosely held in place so they are free to move in order to survive wing-off crashes.

The VTx is cable-tied to an embedded carbon rod on the suction side. It does not lie straight on the foam, there are spacers to create an air cavity. I thought I would build an air cavity in in case I discovered the VTx gets too hot. If that turns out to be the case I could vent the cavity for some cooling flow.

The circular antenna protrudes, but not lower than the wingtip skid so it shouldn’t be a problem. I actually spent a long hangover-ridden Saturday thinking about antenna placement. I wanted to protect the antenna. The wing suction side must stay clean to keep me happy, so I thought about putting the antenna near the tail to keep it protected, but that would be too close to the other electronics. I decided the current location was the best. I chose the spanwise distance by figuring out the maximum rolling moment I could balance with just the offset battery, because I hate adding unnecessary weight (i.e. balance weights on the other wing tip).

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Instead of digging a cavity for the VTx, I simply cut a whole chunk out of the wing, cut that core to the right shape, then glued it back in. I am pleased with how clean the VTx installation is, the only protrusion is the cable tie.

(reached image limit - see part 2)

High-res .pptx version

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scratchbuilt 2m span airframe for 200g+ payload

331i17a.pngHere's a brief wee build log of a plane i promised myself I would make. I'll make the simple plans available for anyone and everyone.

Any suggestions are very welcome !

 

It's mission is to carry a nikon L4 to take some aerial photos, with an efficient wing optimised for a cruise at about 35 km/h.  It must be stable and fairly easy to fly,have a pusher prop configuration and be easily constructed for those with little experience (me :D) : hot-wire cut wings and tail, a wood fuselage, and a GF tube tail boom.

 

Since i'm on a budget, it's to be powered by a 3s 3300mah Lipo, a cheapo 2212 outrunner and 9x6 prop; just what I had lying around. However I have left space for a bigger battery and a 10" prop.  A nikon L4 is about 8.5 x 5.5 x 2.3 and some 180g.

 

I started off by designing the wing, learning to use xflr at the same time. heres what it looks like 'on paper'

Just a simple 2412 airfoil, with -2.5 degrees twist for better lift distribution and hopefully to make stalls controllable.

Wingspan is 2m exactly, with an 18cm root going to a 10 cm tip, with an offset of 2 cm back.

Theres no dihedral here, because i'm not 100% sure about the construction yet.  If i decide it will be easy enough, it will have at most 2 or 3 degrees of dihedral.

 

I moved on to the fuselage next, making LOADS of sketches on paper, settling for what i thought is the best layout (obviously).  It's easier to understand a picture of the fuselage halfway through construction than it is to understand my drawings:

6j34nq.jpgthe aluminium bar represents the wing and don´t worry, that tail is just a couple of offcuts taped on for visualtisation.

The construction is all from a board of liteply, or at least thats what I think it was, its from a DIY store.  It's 4.5mm thick ply and simply glued together, with the boom tight-fitted into a hardwood block also glued into the fuselage.

 

the 'cargo bay' is at the front and is 7.5 x 10 x 5.5 (5.5 at the lowest point, at the front), it could easily have a shelf put in the middle if it is to have APM xbee gps imu tnt ymca and whatever else packed into it.

If at this point you´re thinking 'mate, don't even bother making plans this thing is a flying brick' then i totally agree with you.  But don't worry, it's going to get some pretty foam fairings outside to smoothen that square shape up!

 

heres another pic showing the servo tray at the back

30bmcz7.jpgthe shelve at the back is the servo tray with LOADS of room for the Rx and ESC, the lump of wires is a dud 3s 3300 for illustration, and theres still alot of room for whatever you may be wanting to carry. like some delicate modelling tools :P

 

I then set about making the tail surfaces. It took alot of practice to figure out how to cut nice cores as you can see from the pink mountain, and i'm hoping the thick wing will be easier than cutting the wafer thin tail

s1kdao.jpgJust a piece of steel wire strung between bits of wood, an a transformer from an ex-amplifier regulated by a dimmer switch.  At 9v it draws about 13 amps and produces the best temperature for cutting the pink foam I have.

The big coil of wire on the board is a makeshift resistor otherwise the small wire used for the tail was too hard to regulate, its resistance is very small and merely brushing the dimmer made too much of a temperature difference.

 

UPDATE

 

okay the wings have been cut out, I recommend slow and cold for cutting foam! it took alot to get it right.  Since I ran out of foam i put balsa leading and trailing edges, and a black spongy foam nose for the impending impacts it's gonna have :D

 

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finished fuselage (minus hatch), wing (glue drying), and one awesome foam cutter as long as you have 4 hands available :D  Thats a 10" prop on it.

 

BUT between seeing people and doing nothing over the holidays, I ran out of time for this project, ending at just needing to attatch the ailerons and go fly!  the wind didn't permit this, so now it's waiting in my parents garage for me to come back and give it it's maiden in easter  -.-'  I'll tell anyone watching how that goes . .. .

 

Hamish

 

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Taking requests for an airframe design !

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Over christmas I'm going to make an airframe just as an exercise, and since I don't actually need a new airplane I'm taking requests for payloads and missions. I'd rather make a plane thats useful to someone than one thats useless to everyone, catch my drift?

so if you have any suggestions or are looking for a plane yourself, go ahead and leave your mission and payload in the comments below !I'll test using dummy payloads of equal weght (max payload around 200g, an autopilot counts as part of the payload !)

i'm an aeronautical student at the moment, and you may think is wierd but I actually enjoy the frustrating process of making a quality, mission specific plane!
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