CorporalB's Bixler 2 - build log

[Dusty]

Introduction:

Welcome to my latest and greatest FPV project, the Hobbyking Bixler 2

http://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=29053

I owned the original Bixler and although it was my first retail plane (I had dabbled with scratchbuilts first) it was an excellent all rounder. I've owned other aircraft including JETiger, Skywalker, Swift II and FPV Raptor.... but without doubt the Bixler blew them all away. Not only is it ideal for training purposes, but it's docile nature, stability and ease of flying also makes it an ideal FPV platform

Hopes are high then for the new big brother version.... the Bixler 2


The Build

Motor Choice

When the Bixler 2 arrived, the first thing I did was remove the stock motor and motor mount. There had been enough documented reports about how thin the wires are and that they heat up enough to not only melt the insulation, but the foam around it also. Others had reported that the solder in the bullet connectors had melted and the connectors had come right off.

Seeing as I'll be installing a fair bit of FPV equipment, I didn't want to take any chances so I decided to upgrade the motor mount and install a better motor... one I have previous experience with.

Stock 1300kv motor on the right, next to a 2200kv unit from Giantshark


With the motor in the stock position the maximum prop size you can fit to the Bixler 2 is only 7" (one inch larger than the original Bixler). I wanted to have the option of changing the motor/prop combo for different payloads and styles of flying

2200kv w/6x4 prop for blasting around the skies
1400kv w/8x6 prop for run of the mill FPV flying
1000kv w/9x6 prop for longer range, high altitude and endurance

This motor mount was the ideal solution to give me the flexibility I desire:


new mount installed into the Bixler 2 motor nacelle, the mount is 1mm smaller in diameter than the nacelle so I used Gorilla Glue for this job as it expands/foams out to produce a rock hard filler:


Servo Positioning

I removed both the tail servos from inside the fuselage near the canopy, as you can see they came out with no hacking of foam or mess. They must have only been stuck in with a tiny spot of glue:


These are the pre-installed servos... HK15178 (nope, I've never heard of them either) I can't comment on their reliability but I'm not even going to chance it.


Replacing all servos with Turnigy metal gear servos, apart from the flaps which will just be the plain old blue Tunigy 9g units.


However, due to this being a FPV platform, I plan on having more weight up front than the plane is designed for. Many people load the tail up with dead weight once they've fitted their gear but I'm not a fan of dead weight so I've relocated BOTH tail servos to the tail itself.

Rudder servo to the vertical stabiliser:


Elevator servo to the horizontal stabiliser:


This is how it looks with the tail surfaces installed:


The aileron servos were simple to replace, but the first issue I came across on this build was the unusual design of the flap servo placement. For some strange reason, Hobbyking have decided to have the flap servos mounted as a mirror image of each other... just like the aileron servos. This means you have to do one of the following to get your flaps working correctly:

1 - re-solder the innards of one of your servos
2 - have the flap servos on different channels and use mixes in your computer transmitter
3 - buy a servo "reverser"
4 - do what I did and simply cut the right shape out of the wing to place one of your servos the right way around [see below]



as you can see here, the servos are now in the same orientation so the flaps can be operated using a Y harness on a single channel


you might notice the velcro on the wings in the picture above, this is my wing joining method. the loop material is stuck to the underside of each wing. The hook material is not self adhesive and simply passes through the wing joining hole of the fuselage when both wings are installed and fastens the wings together. These wings are going nowhere fast and now I can get rid of the next strange design feature...

Access hatch creation / wing fastening tube removal

As you can see, there's not much room rear of the canopy area, but it seems like such a waste of space... those wing screw tubes are a silly design feature.


In order to gain access to the space behind the screw tube, I've cut an access hatch directly beneath the CG


There's not much usable space here, but you can see the potential if one chooses to remove the tubes


So that's exactly what I did. Look at that cavernous space... plenty of room for either a larger LiPo or tonnes of FPV gear. I'll be placing my UHF Rx just in the back, down the tail boom.


I've given it a good twist n bend and this hole doesn't affect the torsional strength much at all, mostly because of the large amount of surface area glued to the other half directly above the hatch (the wing joining area). Also, with the hatch taped closed any strength lost is restored.

FPV Pod / Canopy installation

I will be mounting as much of the FPV gear as possible onto the canopy itself. the HornetOSD will be mounted to the underside like so:


The rest of the the FPV equipment consists of a WDR600 camera and 2.4GHz VTX. I designed it this way to make it hot-swappable with my upcoming GoPro Pod and a stock canopy. I ordered 2 replacement units from Hobbyking and they only cost me just over £5 shipped to the UK.


The camera is screwed down, with epoxy inside the screw hole for added purchase, the VTX is zip-tied to the back plate of the canopy and the HornetOSD is stuck to the underside with foam tape





Here's what it looked like installed onto the Bixler 2, nice and clean looking, even if I do say so . The only thing I haven't placed on the canopy is the GPS unit. The general consensus with regards to GPS and VTX placement is that you shouldn't have them near each other... I know the GPS is very close to the VTX in this picture, but I have since relocated it to the tail


GPS relocation, ESC and RX installation

So in order to minimise any potential issues I went ahead and relocated the GPS puck to the tail boom.


I also finally decided on what motor/prop combo to use and installed the 40A Hobbywing ESC on the outside of the airframe for cooling.


The motor is a 2208/14 1450kv unit from Giantshark, swinging an 8x6e TGS propeller.


As you can see [above] the adjustable motor mount is in the middle position allowing for 10mm - 12mm clearance from the tail boom [below]


The RMILEC UHF receiver has dual/diversity antennas, but there's no way to disconnect them like a SMA connector or anything, they're hard installed into the rx unit itself. I've done a lot of reading on the subject and listened to people's personal experience with the RMILEC equipment and have decided that 90 degree separation, one vertical and one horizontal, is how I'm mounting the antennas. The TX antenna will be in the vertical position also.

The vertical antenna is in the tube just in front of the motor, extending a few inches up from the top of the Bixler 2, this tube is very stiff and I will be very surprised if the Bixler2 can gather enough airspeed to effectively bend the tube far enough to reach the prop. The horizontal antenna is in the tube running to the rear of the tail. The horizontal tube simply slotted into the recess left by taking off the push-rod tubes (no longer needed due to relocation of tail servos to the tail).



Build Completed

The almost final product, fully laden with 2200mah 3S for flight and 800mah 3S for FPV equipment. All electronics are installed and the only things left to do is to program my TX for flaps and OSD switch, centre all the control surface channels on the TX and manually trim the surfaces to level.



AUW = 1.1Kg

[Dusty]

First recorded FPV flight

Hobbyking Bixler 2 FPV - 2.2km	Small | Large

[Dusty]

reserved

[mrholozip]

This thread rocks, can't wait to see you lob it in the air... I dunno where I got the idea from, but I figured you were exclusively a quad guy.

Some great mods there; especially like that mount - where is it from?

[Dusty]

Thanks Gareth, the motor mount was bought from Readymaderc.com http://www.readymaderc.com/store/index.php?main_page=product_info&cPath=53_60&products_id=748

only a tenner

[Ratty]

Awesome Chris. Thats a very nice build and lots of good info.

Isnt your horizontal rc antenna pointing the wrong way? I thought it should be along the wing rather then the fuse. So the diversity kicks in when you bank rather than when you climb/dive.

[Ant]

Nice build bud ! Are you going to use the rssi feed from the rmilec. Its pretty good and a doddle to set up.

[Dusty]

HornetOSD doesn't have Rssi

[Dusty]

Video is usually fine on the ground but you tend to find the noise/static when you throttle up. So I did some ground throttle tests with the video running to see if it is indeed affected...

you can see the Amps in the bottom left, on the second "move" the plane got caught on some leaves and couldn't go any further... even on full throttle. full throttle only pulled around 20Amps with the bixler 2 held stationary, I think the 40A esc is a bit overkill but I prefer to have the safety net so to speak.

the video speaks for itself, even on full throttle there's no interference on the video happy days

video-throttle tests	Small | Large

[Cupid Stunt]

HornetOSD doesn't have Rssi

No I asked Foxtech when the Hornet first came out and they said it's pointless with RTH

[Cupid Stunt]

Wht, no maiden flight before fitting FPV gear ?

[Dusty]

Didn't want to get it up, then change it all around when i installed the gear... just wanted a clean install from the beginning.

Just got back from the maiden now, did a LOS maiden with all the FPV gear on for a few minutes, trimming it out, see how it handles.... pretty much the same as a bixler1 lol.... but slower (with the 1400kv 8x6 prop) so might change the motor for next time.

things went pretty well so I slipped the goggles on. and the FPV maiden went without a hitch.

No video though.... went to all that trouble and left my flippin archos dvr travel adapter in the car.... didn't have time to walk back to the car then back to the field, needed to get home so the missus could take the car (hair appointment lol)

will get a video next time.

2 things to note though:

1. on one of my first landings with flaps, the bixler2 flared up drastically and stalled, causing a little crash, nose first from about 3 foot high. no damage, but the fuselage had split right at the nose where it's glued together... good job I had a rubber band at hand to keep it together. there was no way I was leaving the field if I didn't have to.

I'll make sure to re-glue and fibre tape it together before the next flight.

2. The wing spar is definitely too flexible, I thought it was going to snap at one point I had to really make an effort to fly very conservatively.

I have a 4mm 1.2m carbon rod on the way from a kite store though, so that should strengthen the wing and reduce the flex.

[Cupid Stunt]

Well done mate
My SSS is still sat on the table waiting for the gear to be permanently fitted in, just can't be bothered to do it, what a waste of an RVOSD G5 and RVGS really

[Dusty]

I used to be like that, many projects and all the gear to build them were just sitting in the shed or garage waiting to be completed... could never be bothered. So I decided to put everything aside and chose a single project to work on... this Bixler 2.

and it paid off, will definitely get footage next time.

Oh, by the way... I'm installing my KK2.0 board into it after the weekend... looks easy enough and will have gyro stabilisation and auto level

[Cupid Stunt]

You need to test things like flaps at high altitude so you can save it
Often flaps will require you to mix in a bit of elevator

Things about flaps:
1. They give slightly more lift when there's not much wind about to soar on (about 5 deg flaps is plenty)
2. Full flaps can be used to slow a plane but on their own may well cause the plane to pitch up or down, you may need to mix in some elevator to compensate for the pitching
3. Use flaps in combination with individual ailerons for crow breaking (flaps go down both ailerons go up) you do need to have the ailerons on separate channels for that though which is no good with any of the autopilot systems I know of
4. Same as #2 really but it does allow you to land in tighter spots i.e. where you have to come in over trees then drop fast, flaps can help to scrub off the speed gained in the dive

Flaps especially when on full can put a considerable load on the sbec/ubec, that plus the fact that you simply have two extra servos to power can mean that it is even more wise to have a separate sbec with more power than a built in one i.e. 7amp