VTOLT Build Instructions

7/27/2019 VTOLT Build Instructions

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Designed by: Ran D. St. Clair [email protected] Page 1

VTOL Trainer Build Instructions

The VTOLT (Vertical Take Off and Landing Trainer) is a combination of a basic RC trainer aircraft with a

quad-copter. It was designed to be easy and fun to fly in all flight modes from hover to full forward

flight (FFF). It is implemented as a kit bash based on the popular Bixler EPO Trainer, making It

relatively cheap and easy to build using standard off the shelf parts. There is no programming involved

and no code to download or install. A computer is not required, except to print the instructions. The

motor mounts are the only parts that require any significant custom fabrication and hopefully one of the

major hobby distributors will soon be offering them based on this design.

As an airplane, the VTOLT is very normal. It does all the typical maneuvers you would expect of a trainer

including inside loops, rolls, and inverted flight. It is a bit heavier and more complex than a typical

trainer, and is not very fast due to the low pitch propellers. The flight times also tend to be fairly short,

as little as 5 minutes with a 2,200mAh battery.

As a quad-copter the VTOLT is very easy to fly. It is mostly auto stabilized by the onboard electronics. I

would not recommend it as your first quad-copter only because there are excellent, cheap, and

extremely durable quad-copters that you can learn to fly in your living room. If you can comfortably

hover tail in, meaning the aircraft is facing away from you, then you will have no difficulty hovering the

VTOLT.

Transitions from hover, to SFF (Slow Forward Flight), to FFF (Fast Forward Flight), and back again, are as

easy as flipping a switch and flying the plane. SFF is the easiest flight mode, ranging from gentle cruising

in airplane mode to a nose high hover.


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Unlike a lot of VTOL aircraft, including most tail sitter types, the VTOLT handles a modest amount of

wind with ease. It flies at any speed from slowly backwards to full forward flight, so you can simply

point the nose into the wind, match your airspeed to the wind speed, and hover for a takeoff or a

landing.

The purpose of these instructions is to share the recipe. There is no profit motive and no commercial

affiliation. The information is free and any hobby supplier is free to take the design and run with it. All

of the enabling technologies are now available and relatively cheap. Its just that not very many people

have figured out how to put them all together in this way.

A short video of the VTOLT in flight is available here:

http://www.youtube.com/watch?v=UyVF0xCNMos&feature=youtu.be

These build instructions are based heavily on the original build thread, including video and lots of

detailed information that can be found here:

http://www.rcgroups.com/forums/showthread.php?t=1814667


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Specifications

Weight: 3 pounds, 4 oz.

Wingspan: 48.5

Wing Area: 346 sq. in.

Maximum Power: 555W

Measured Battery Current:

0.43A - All motors at full idle

18.4A Hover Power

49A to 51A Full Throttle

Each motor is drawing about 4.5A at hover power and 12.4A at Full Throttle (FT). The FT battery current

peaks at about 51A when FT is first applied, but within second it drops to under 50A, and in a second

or so it is down to 49A. Presumably this is due to a drop off in battery voltage at this current.

The FT thrust peaks at 5 pounds 12 oz., and quickly drops off to 5 pounds 8 oz. Considering that the

plane weighs 3 pounds 4 oz., it has a FT thrust to weight ratio of between 1.69 and 1.77.

The battery I am using is rated at 35-70C discharge, but now has at least 30 discharge cycles, some of

them to pretty near flat, and is slightly puffed. The actual FT discharge rate is about 22.7C, so well under

the 35C specification. In flight I expect it only ever goes slightly above the hover current or about 20A. I

do fly the plane at FT briefly, but usually in forward flight mode where the motors are not so heavily

loaded.

At 4.5A per motor, the hover current is actually less than I would have expected. Even so, I am only

getting about 5 minute flights using 2/3 of the battery capacity. At 20A average, which is probably on

the high side, 5 minutes is about 1.7Ah, which is about 75% of the batteries 2.2Ah rating, so thenumbers are close to reality.


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Radio Requirements

The VTOL-Trainer requires a 7 channel Transmitter (TX) and Receiver (RX) as a minimum. The prototype

was based on the Spectrum DX7s, which has a 3 position flap switch that can be used to tilt the motors

slowly from hover mode, to Slow Forward Flight (SFF) mode, to Fast Forward Flight (FFF) mode. This

function can also be provided with an analogue input like a pot or a slider so long as it is accessiblewithout removing your hands or thumbs from the sticks, or if necessary only your left hand briefly,

assuming you are flying mode 2 with your right hand controlling pitch and roll.

If you decide to control the motor tilt angle directly, you may wish to use a servo slower to smooth the

transition between hover and forward flight. Here are 2 such products, though I have not tested them

so I cannot recommend them.

http://www.rcdude.com/servlet/the-17/Dionysus-Servo-Rate-Reducer/Detail

http://www.hobbyking.com/hobbycity/store/uh_viewItem.asp?idproduct=8863

It is possible to use a 6 channel TX and RX if you use some sort of a Matchbox like this one to adjust

the endpoints and travel direction of the two motor tilt servos. I have not personally tested this

solution.

http://www.espritmodel.com/jr-servo-matchbox.aspx

It is not possible to drive both of the two motor tilt servos with a Y harness. They need to travel in

opposite directions, and even if they did not, it would be difficult or impossible to adjust the linkages to

get them both to work together properly.

If you have a TX and RX with more than 7 channels you may choose to eliminate some or all of the Y

harnesses that are required for this design.

If you choose to use a Flight Controller other than the recommended KK2, you will need to determine

your own stability parameters, and a way to vary those parameters between hover and FFF mode.


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Control System Block Diagram


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Consolidated Parts List

I have attempted to provide a detailed listing of every part required, as well as a current valid URL where

you can buy them. I am not suggesting that you must buy them from these suppliers. I am mostly

providing the URL information in case there is any confusion about the nature of the parts or materials.

You probably already have much of what is required, or it can be found at your local stores. Obviously,you will need to make substitutions to match your radio.

1. 1 each, Bixler V1.1 kit, for $36.40 eachHobbyking_Bixler_v1_1_EPO_1400mm_KIT_.html

2. 1 each Hobbyking KK2.0 Flight Controller board - $29.99 each.Hobbyking_KK2_0_Multi_rotor_LCD_Flight_Control_Board.html

3. 1 each, HobbyKing OrangeRS R710 Spectrum DSM2 Compatible 7 channel RX for usewith Spectrum DX7s TX. $19.95 each. Any 7 channel RX will do.

OrangeRx_R710_Spektrum_DSM2_Compatible_7Ch_Receiver.html

4. 1 each, HobbyKing Orange R100 satellite RX to add RF path diversity. $11.83 eachOrangeRx_R100_Satellite_Receiver.html

5. 4 each, Turnigy Plush 18A brushless motor speed controllers - $11.90 each.TURNIGY_Plush_18amp_Speed_Controller.html

6. 1 each, HobbyKing, Li-Po Low Voltage Alarm $1.99 each. (Optional)On_Board_Lipoly_Low_Voltage_Alarm_2s_3s.html

7. 2 each, Turnigy nano-tech 2200mah 3S 35~70C Lipo pack, $21.55 each. (The 2ndbattery is optional)

Turnigy_nano_tech_2200mah_4S_35_70C_Lipo_Pack.html

8. 4 each HEXTRONIK, HXT900, 9 gram servos or similar, $2.69HXT900_9g_1_6kg_12sec_Micro_Servo_USA_Warehouse_.html

9. As needed, Wire, 18AWG, Silicon Insulation, Flexible, $0.51/meterhttp://www.hobbyking.com Turnigy_Pure_Silicone_Wire_18AWG

10. 12 each, 2mm bullet connectors, Motor Wires, $1.98/10 male-female pairhttp://www.hobbyking.com/hobbyking/store/__66__2mm_Gold_Connectors_10_pairs_20pc_.html

11. 1 each, Castle Creations CC BEC 10A (peak), $24.95 eachhttp://www.rcplanet.com/CC BEC 10A

12. 4 each, CarbonBird 1175kv, 175W, Reversed shaft for 3S motors, $23.50 eachhttp://www.multiwiicopter.com/products/carbonbird-motor-nmb-1175kv-reversed-shaft

13. 2 each, CW and 2 each CCW, GWS, 9 diameter, 5 pitch, 3 blade, 5mm hub, Props,$19.85 per 4 each CW and 4 each CCW

http://www.multiwiicopter.com/products/sku-27


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14. 16 each, M3 x 5 Bolt, 3mm Stainless Steel Hex Head 5mm Shaft, $2.75/10.http://www.multiwiicopter.com/products/m3-bolt-3mm-stainless-steel-hex-head-5mm-shaft-set-

of-10

15. 5 pair each, JST Gold Plated Connectors w. 20 AWG flying leads, Male and FemaIe,

$6.50/6 pairhttp://www.multiwiicopter.com/products/jst-gold-plated-6-pairs

16. 1 each, Power Distribution Harness, XT60, JST 5 way, $9.95 each.http://www.multiwiicopter.com/products/power-distribution-harness-xt60-jst-5-way

17. 1 each,XT60 Male connector, $1.99/male-female pair, Not needed if you buy the XT60Power Distribution Harness

http://www.multiwiicopter.com/products/xt60-pair

18. 3 each, 50mm Y harness, $3.75 eachhttp://www.multiwiicopter.com/products/y-lead-50mm-rc-servo-connector-1-male-jr-2-females-

futaba

19. 5 each, 5 female to female cables for connection from the RX to the KK2 board, $1.50each.

http://www.aeroquadstore.com/Receiver_Cable_5_inch_length_p/rcvr-002.htm

20. 36, McMaster Carr, 8975K823, 1 x 1/16 6061 Aluminum strip stock, $3.79/6ft.

21. 8 each, McMaster Carr, 91125A339, 1/8" long by 1/4" dia. stainless steel standoff with 4-40 internal thread,,For use on motor mounts, $1.14 each.

22. 8 each McMaster Carr 90062A015 nylon short barrel shoulder washers that will act asbushings on motor mounts, $5.82/100.

23. 8 each, McMaster Carr, 91735A101, 4-40, Pan Head, Phillips, 3/16 long, for use onmotor mounts, $5.65/50

24. 4 each, McMaster Carr, 8876T15, 3/16 Nylon Cable Clamp, $5.40/100

25. 4 each, McMaster Carr, 90272A108, 4-40 screw, Pan Head, Phillips, 3/8 long, holdscable clamp on side of motor mount, $1.49/100

26. 4 each, McMaster Carr, 90631A005, Nylon Insert Hex Locknut, 4-40, holds cable clampon side of motor mount. $2.55/100

27. 4 each McMaster Carr, 90126A505, #4 Flat Washer, 5/16 O.D., Zinc Plated, Holdscable clamp on side of motor mount. $1.09/100

28. 4 each, McMaster Carr, 90272A079, 2-56 screw, Pan Head, Phillips, 3/8 long, holdscable clamp on side of motor mount, $3.28/100


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29. 4 each, McMaster Carr, 90480A003, 2-56 Hex Nut, holds over rotation stop on side ofmotor mount, $1.21/100

30. 5 each, McMaster Carr, 90184A115, #4 self tapping screws, 1 long, Phillips Pan Head,for use on landing gear mount, $11.99/100

31. 20 each, McMaster Carr, 90184A108, #4 Self Tapping Screws, long, Phillips PanHead, For use on motor mounts and strut mount, $6.01/100

32. As needed, McMaster Carr, 7610A11, 3M Super 77 spray adhesive, $20.81/24 fluid oz

33. As needed, McMaster Carr, 91458A111, Loctite, 242 blue removable, $1.95/.02oz.

34. 2 each, McMaster, Carr 90975A002, 4-40 blind nuts, For use on wing mount plate,$10.29/100

35. 2 each, McMaster Carr, 90272A121, 4-40 stainless steel pan head Phillips screws, 2long, For mounting the wing. $6.30/50

36. 2 each, McMaster Carr, 91735A029, 2-56 Pan Head Phillips Screw, long, RearLanding Gear Mount, $7.10/50

37. 2 each, McMaster Carr, 91735A021, 2-56 Pan Head Phillips Screw,1/2 long, FrontLanding Gear Mount, $6.18/50

38. 2 each, McMaster Carr, 90126A509, #6 Flat washers, For wing mount, $1.31/100

39. As Needed, McMaster Carr, 7130K12, Small Cable Ties, $2.27/100

40. As needed, Elmers white glue, McMaster Carr, 7516A1, $3.12 each.

http://www.mcmaster.com/#

41. 2 each, 6mm x 1mm carbon f iber (CF) strips, $3.50 eachhttp://www.rcfoam.com/6mmx1mm CF

42. 1 each, CF rod, 2.5mm, .098, 1000mm (39) long, Wing Struts, $2.50 eachhttp://www.rcfoam.com/2.5mm CF Rod

43. Misc, 6mm Depron, $4.49/ 13 x 39 sheethttp://www.rcfoam.com/6mm Depron Sheet

44. 1 each, BluCor Foam, 2 x 12 x 24, Used for Motor Pods, $5.00 each.

http://www.rcfoam.com/BluCor Foam 2"

45. 1 each, Foam-Tac glue, $9.99/2oz.http://www.rcfoam.com/product_info.php?products_id=1243

46. Misc., 30 minute Epoxy, $8.99/9 oz.http://www3.towerhobbies.com/cgi-bin...&I=LXPT46&P=ML


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47. 4 each, Dubro catalogue number 181, 2-56 threaded ball link, for use on motor mounts,$1.94 each.

http://www3.towerhobbies.com/cgi-bin...P?I=LXD897&P=8

48. 2 each, Hitec HS-85MG Metal Gear Servo, $29.99 eachhttp://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXN685

49. 4 each, 2-56 blind nuts, $0.99/4http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXD966

50. Misc., Foam Safe thin CA Glue, $11.69/1oz.http://www3.towerhobbies.com/cgi-bin...P?I=LXM365&P=8

51. 2 each, Dionysus in line servo reversers, $11.95 each.http://www.rcdude.com/servlet/the-19/Dionysus-Servo-Reverser-V2/Detail

52. 1 each, Y Extension 12" Futaba Plugs 26 AWG - WY-FP-15, for aileron servos, $3.75each.

http://www.slickzero.com/page/SRHP/PROD/Extensions/WY-FP-15

53. 2 each, Hyperion Servo Extension Cable - Standard 12", to drive tilt motors, $2.95 eachhttp://www.rcdude.com/servlet/the-680/Hyperion-Extension-Cable--dsh-/Detail

54. 1 each, Sullivan, SUL505, Gold-n-Rod Semi-flexible, blue outer housing, yellow innerrod, $7.95 each.

http://www.horizonhobby.com/products/pushrods-semi-flex-36-w-clevis-2--SUL505

55. 1 each, White Ultracote, $15.99/rollhttp://www.horizonhobby.com/products/ultracote--white-HANU870

56. 1 each, Trex 500 helicopter Landing gear set, $9.99 eachhttp://www.ronlund.com/rcheli-prod/ALIGN500_LANDING/H50047.html

57. 8 each, Great Planes, 4-40 Clevis, GPMQ3795, For use on wing struts, $8.49/12http://www3.towerhobbies.com/4-40 Clevis

58. As needed, Formula 560 Canopy Glue, $3.99/2oz.http://www.horizonhobby.com/products/zap-formula-560-canopy-glue-PAAPT56

59. As needed, Sticky Back, Velcro. 1 wide, Component mounting, $1.88http://www.cableorganizer.com/velcro-adhesive

60. As needed, Plumbers Goop, Household Goop, Automotive Goop, etc. but they areall the same thing, $4.59

http://www.kmart.com/amazing-goop

61. As needed., thick Foamsafe CA glue, $16.99/2oz.http://www.hobbylinc.com/htm/hot/hotufo4t.htm

62. As needed, Non-Shrink Spackle, $6.00/qt.


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http://www.globalindustrial.com/Non-Shrink Spackle

63. 1 each, Cellfoam1/8, for use on hatch, $5.49http://www.midwestproducts.com/18_3mm_x_11-12_x_11-12_Cellfoam_88.aspx

64. As needed, Aircraft Plywood, Midwest Products

65. 6 x 12 x 1/64, $7.99 each66. 6 x 12 x 1/32, $8.98 each67. 6 x 12 x 1/16, $35.99/6 sheets68. 6 x 12 x 3/32, $39.99/6 sheets69. 6 x 12 x 1/8, $37.99/6 sheets70. 6 x 12 x , $20.99/6 sheetshttp://www.midwestproducts.com/Plywood

http://www.utrechtart.com/midwest-thin-aircraft-grade-birch-plywood-12-x-24-in-sheets---4---

3mm-thick

http://www3.towerhobbies.com/cgi-bin/WTI0001P?I=LXAS66&P=8

71. As needed, Scotch tape, , Available Everywhere


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Motor Mounts

The motor mounts are the most difficult part of this project, which is why I am hoping that someone will

pick up the design and offer it commercially. They are not difficult to build if you have some basic tools,

but it would still be much easier to buy them.

Lets begin with some of the basic design philosophy and specifications. They need to be simple, strong

and reliable of course, and they should be as easy to make as possible. I wanted them to be as narrow

as reasonably possible because the motor boom will be as wide as the motor mount, and it blocks a

portion of the rotor disk and reduces the resulting lift when in hover mode.

The motor pivot point is roughly at the C.G. for the combination of the motor and the propeller. Thisreduces the gravity loads on the tilt servo, and also reduces the shock loads in case of a rough landing.

This design cant protect the servo if the motor or prop hit something though. The motor pivot point is

also in line with the prop shaft, so motor thrust will not be translated to servo torque.

The mount has a mechanical over rotation stop in the vertical direction. This is a safety feature to try

and avoid a prop-boom strike. Depending on the accuracy of the build, the stop may engage 1 or 2

degrees before the motor reaches vertical. This is by design as it provides more clearance between the


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prop and the boom. It is also convenient to have the motors tilted slightly forward even when in full

hover mode. It just means that the aircraft hovers 1 or 2 degrees nose high which is convenient for a

number of reasons. If you should use this design where you need the motor to rotate farther you can

simply remove the over-rotation stop, or you can file a small depression in the side of the outer yoke to

have the stop engage wherever you want.

The tilt bearings are stainless steel in a nylon bushing. They require no lubrication which might attract

dust. They are not perfectly without slop, but the math says that the slop due to the bearing alone is

just slightly over 1 degree. This has not been a problem in previous designs.

The tilt input is via a standard 2-56 threaded ball link, Du-Bro catalogue number 181, with a lever arm of

0.5. This works well with a typical servo output arm of about the same radius or slightly less. It is best

if the linkage uses close to the maximum available servo travel for maximum torque and minimum slop.

The motor wires are well managed throughout the tilt range with no kinks or stress points. There are

provisions for a nylon cable clamp on both sides of the outer yoke.

The design is intended to be left/right symmetrical with one exception. The standard motor mount boltpattern is not symmetrical with respect to the direction that the wires exit the motor. A universal

mount would require slotted holes, which is not convenient or necessary for hand made prototypes, so

the motor mount holes are simply located as required.

The motor mount is suitable for both tractor and pusher applications, however, the possibility of a

propeller-boom strike is greater for a pusher due to flexibility of the propeller blades.

The mount is intended for use with a simple plywood firewall and will typically be attached with 4 each

#4 self tapping screws. It weighs about 18g including bearings, over-rotation stop, ball link and wire

management hardware. For reference, it is typically used with motors weighing 50g to 68g on VTOL

aircraft weighing about 48 oz (3 lb).

The mount works with the Carbonbird motors which are 28mm in diameter. It should also work well for

similar Scorpion, E-flite and AXi motors of essentially the same diameter.

I did run into an unexpected snag during the build of the 4 prototypes. Of the 4 motors I received from

Multiwiicopter.com, one has a reverse image mounting bolt pattern. This is not a huge problem for me.

I simply filed the mounting holes into slots with a needle file. It means, however, that I cant give you a

universal motor mount design. You can use this design as a basis, but you will need to check your

specific motors to determine if they will fit. Its much easier to drill them to fit in the first place rather

than filing them to fit later.


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Inconsistent Bolt Patterns

I also note that the Multiwiicopter.com web site calls for the mounting holes to be 16.5mm by 19mm

spacing. They are not. They are 16mm by 19mm. Personally I would rather they were square, like

19mm by 19mm, but this offset spacing seems to be some kind of an industry standard. The E-Flite and

AXi motors I own have a similar spacing.

Motor Mount Build Instructions

Print the page with the motor mount drawing at 100% scale and verify that both pieces are 1 from top

to bottom. Also verify the motor mount holes as needed for your specific motors. You can often usethe X mount that comes with the motors as a template. Make sure the motor wires exit straight down

as viewed on the drawing.

You will need 4 more copies to use as templates. The templates dont need to be cut exactly on the line,

but if you are using 1 wide base stock then the one long edge should be cut precisely to aid in

positioning the templates.

You can use 1 strip stock from your local hardware store or you can buy 1/16 thick strip or sheet stock

from McMaster Carr or most any other source. The alloy is not critical but 6061, 1001, or 3003 is most

common. You dont want any prior heat treatment because you need it to be soft for bending.


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Spray a light coat of 3M Super 77 spray adhesive on your aluminum stock and place the paper templates

for efficient material use. Let the glue dry so your templates dont shift when you begin work.

Place Templates

I recommend you drill the holes first and then cut the pieces apart. Carefully center punch each of the

holes to be drilled. This is the most critical step for the accuracy of the final product. Using sharp drills

at low speed, drill each of the holes to the size specified on the drawing. Holes larger than 1/8 should

be drilled to 1/8 first and then drilled to their final size. A drill press makes this much easier and more

accurate.

Drill Holes

Soft aluminum is gummy and will leave large burrs on the exit side of the drill holes. I like to use a piece

of soft wood under the aluminum to avoid smashing the burrs which makes them more difficult to

remove. I also use a sharp wood chisel to slice the burrs off the backside of the aluminum. You may

need to do this after every hole, or every few holes, otherwise the burrs will accumulate and you wont

be able to lay the aluminum flat for further drilling.


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Removing burrs

The 5/8 hole in the center of the outer yoke is not absolutely necessary. It is only there to remove

excess material and make the mounts lighter. I used a bi-metal hole saw, but you can also drill it out

with the largest drill you have, or not drill it at all.

Cut the pieces out using whatever tools you have. A hack saw and a file will work if necessary. A good

jig saw with the proper blade is better. A sheet metal sheer is best, or since these pieces are all fairly

small I used a manually operated corner cutter. I also used a belt sander to clean up the edges and

remove the burrs, but you can do the job with a file or even a sanding block.

You can make the bends in a bench vice, but a sheet metal brake is best. You will note that the drawings

show 3 lines at the bends. The one in the middle is the center of the bend, and the ones on either side

show where the bend begins and ends. They also show precisely where to position the brake shoe. The

tip of the shoe is placed on top of the line nearest the end of the part. See the included picture for

reference. Also note that a plastic square was used to insure that the parts were exactly perpendicular

to the brake. Bend the inner motor mount piece slightly past 90 degrees. It will be easier to bend it back

out a little if necessary later. Also, it will tend to bend out a little when the motor screws are tightened.


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Bending Brake Overbend

Use a small tray with a little acetone to loosen the paper templates, and then use an acid brush to scrub

off the glue. You can use a 3M paint stripper wheel to clean up the surface of the metal and remove any

remaining burrs if you are so inclined. I use mine in the drill press at high speed, but work gently as itwill remove material quickly if you let it. Once the parts are clean, wash with soap and water to remove

any residue. You can paint the parts with rattle can paint if you want, but it isnt necessary.

Bent Cleaning In Acetone

Final assembly requires some adjustment to get everything to fit just right.

Insert the McMaster Carr, 90062A015, nylon bushings from the outside in, into the two 3/8 diameter

holes of the inner motor mount. They should fit snug. If they are too tight you may have to file them

out a touch. If they are too loose you may need a drop of CA to lock them in place. You dont want

them to be sloppy as it will contribute to motor tilt angle slop. Dont allow the CA to get into the

bearing surface.


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Stub Shaft and Bushings Bushing Placement

http://www.mcmaster.com/#catalog/119/3235/=lm08z4

Mount the motor in the inner motor mount using 4 each of the 3MM button head screws. You can alsouse the flat head screws that came with the motor but you should really countersink the holes in that

case.

http://www.multiwiicopter.com/products/m3-bolt-3mm-stainless-steel-hex-head-5mm-shaft-set-of-10

Test fit the inner motor mount into the outer yoke. You want the outer yoke to pinch inward on the

nylon bushings slightly, but not so much that it creates excessive drag on the nylon bushings. Make any

necessary adjustments to the bend angles of the outer yoke. If you see that you also need to make

adjustments to the inner motor mount bend angles then remove the motor first. You dont want to

bend the motor shaft or damage the motor. When everything looks good and the pinch pressure is

about right remove the motor from the inner motor mount. You will need it out of the way to install thestainless steel shaft stubs, McMaster Carr, 91125A339, using a 3/16 long 4-40 screw. A standard mild

steel screw with a Phillips pan head will work fine.

http://www.mcmaster.com/#catalog/119/3239/=lm0ewe

Now remount the motor and check the pinch fit. You can pry the outer yoke open slightly if it is too

tight, and you can pinch the outer yoke together slightly in a vice if necessary. Eventually, you will want

to lock down all of the various screws with 242 blue removable Loctite. For now, only put Loctite on the

2 screws that hold the stainless steel standoffs. You will need to remove the motor to access the

standoffs. Use a minimum of Loctite and keep it out of the bearing surface area because once these are

installed there is no easy way to remove them.

Now you can mount the over rotation stop, the ball joint, and the cable clamp.

The 3/16 cable clamp, McMaster Carr, 8876T15, is mounted with a 3/8 long, 4-40 screw, with a Phillips

pan head, from the inside out. Use a washer and a 4-40 nylock nut on the outside. Small cable clamps

like this should be available at your local hardware store, or similar. You may have to slightly file the

upper rear corner of the inner motor mount to make it clear the head of the cable clamp screw.


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http://www.mcmaster.com/#nylon-cable-clamps/=lm0me3

The over-rotation stop is assembled from a nylon spacer, McMaster Carr, 94639A193, and a 3/8

long, 2-56 Pan head Phillips screw, and a 2-56 nut.

Mount the 2-56 threaded ball link, Du-Bro catalogue number 181, with the included washer under the

ball link, not the nut. Otherwise the threaded shaft of the ball link might extend too far inward and

touch the motor bell housing. Speaking of which, make sure that the motor turns freely and nothing is

touching the bell housing.

Critical Clearance Areas

Thread the motor wires though the cable clamp and make sure they have an adequate service loop

when the motor is vertical. When the motor is rotated to horizontal there should be no stress on the

wires.

You will need to remove the motor from the motor mount one more time when you install the assembly

to the firewall.


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Motor Pods

Motor Pod

The two wing mounted motor pods are made from 2 thick blue foam, available at your local building

supply store, or if you dont want to buy so much of it you can get a 2 x 12 x 24 piece for $5.00 plus

shipping here:

http://www.rcfoam.com/product_info.php?cPath=72&products_id=349&osCsid=6bc29e881afe435910e

a27dc8e9b815f

Print 2 copies of the pages with the motor pod templates. Be sure to print it at 100% scale. Both pieces

should be 9 1/8 from end to end. It is drawn in two pieces so it will fit on a standard 8 x 11 piece of

paper. Cut the pieces out and tape them together at the join line making sure that the datum line thatruns through both pieces is straight. You will need a right and a left. As printed the template is for the

inside surface of the left motor pod. You can use PDF software to flip the image, or do it old school with

a straight pin and a pencil. Just poke holes at the various corners of the servo and then flip the paper

over and connect the dots.


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Motor Pod Template

Spray a light cote of 3M Super 77 spray adhesive on the templates and lay them on the foam. Cut out

the pieces with a jig saw, or whatever you have, but take care to cut them square. You will note an

arrow on the template that says Cut to here. We are going to intentionally cut the wing opening

slightly short. Later, we will test fit the pods onto the wing and use the wing itself as a template to mark

and cut the trailing edge of the slot for a perfect fit.

Use your finger to smear a coat of Elmers glue in the wing saddle area and let it dry. This will toughen it

up a bit.

Use the attached firewall template to make all 4 firewalls out of 3/32 aircraft plywood. The templates

should measure 2 wide, use 3M Super 77,or you can use rubber cement which is easier to remove, andyou know the rest.

Firewalls

Double check the foam for square before attaching the firewall pieces with epoxy. The flat side of the

firewall goes to the top on the front of the pod, and to the bottom in the rear. The little round notch

goes to the inside, which is the side where the paper is attached. Tape the firewalls in place with some

scotch tape and let them cure.

Use a sharp X-acto knife to cut the openings for the tilt servos. I am using Hitec HS-85MG servos butany similar metal gear servo should work. You dont have to cut the servo pockets to full depth right

now, but you need to cut them deep enough so you can tell where the servos will go after you remove

the paper template. When you do cut the pocket to full depth later, leave a shelf on the front side for

the servo mount boss. There is no shelf on the back side since the extra material is removed to allow

room for the servo wires.


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Servo Opening with Shelf

Remove the paper templates and carve and sand the motor pods to shape. Round all the corners as

much as possible except in the area of the wing saddle, and even there a little rounding at the leading

edge and trailing edge of the wing wont hurt. We want to allow the air to flow around the motor pods

as easily as possible, especially in the area of the prop disk when in a hover. Dont be afraid to sand

down the edges of the firewalls a bit, they are a little larger than necessary.

Shaped Motor Pods

Finish digging out the servo pockets until the servos fit so the top of the servo arm mounting screw is

flush with the outer surface of the pod. A small blade screwdriver seems to be the best tool for this.

You will also need to carve out room for the lower part of the servo arm to swing through its range of

motion. Poke a hole through the bottom of the motor pod into the servo pocket for the servo wire.

There will be a 6mm strip of carbon fiber running down the center bottom of the pod so locate the hole

to the inside of the carbon fiber strip.


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Servo Pocket and Wire

Carve out the slots for the motor wires and the servo wire per the pictures below.

Front Motor Wire and Servo Wire slot

Rear Motor Wire Slot

Carve out the slot for the Sullivan Gold-n-Rod outer housing. I used the semi-flexible type with the blue

outer sheathing and the yellow nylon inner rods. The slot is aligned with the tip of the lower servo

output arm, across the top surface of the wing and is clear of the motor pod for the last 2 or so. I

carved the slot with a 3/16 diameter round file.


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Gold-n-Rod Slot

The Gold-n-Rod outer housing is 12 5/8 long and the rear end aligns with the surface of the rear fire

wall. It is intended to support the yellow nylon inner rod throughout its entire length to prevent

unwanted bowing.

Dry fit the servo, servo arm, clevis, push rod, etc. and make sure it all lines up nicely with plenty of

clearance for the full range of servo travel. Also, check that the rear end of the pushrod housing is

pointed directly at the ball joint with the motor mount test fitted in place. The top of the motor mount

will be located flush with the flat edge of the firewall and is centered left to right.

Permanently glue the Gold-n-Rod outer housing in place. I used a bead of Foam-Tac and some scotch

tape to temporarily hold it in its slot.

Gluing Gold-n-Rod Outer Housing

You will need 2 each 6mm x 1mm carbon fiber (CF) strips at $3.50 each available here:

http://www.rcfoam.com/product_info.php?products_id=797&osCsid=f8b889d2908e9589b190e4f08036

4d71

Rough up one side of both CF strips with some fine sandpaper. I do this in the sink with a little water

running so any loose fibers go down the drain. You may also want to wear gloves as the fibers can be

very itchy. Cut one strip in half for use along the top of the two motor pods.

Groove the foam on a shallow angle about 1 away from the firewall on the top and bottom at both

ends of the motor pods. Dry fit the CF strips in the slots in the top of the firewall. It is not necessary to

groove the foam along the entire length of the motor pod. Cut a triangular hole in the foam where it

meets the firewall under the groove. The idea is that we will fill this hole with epoxy when we glue the

CF strip in place. It will form an epoxy filet and strengthen the joint between the CF strip and the

firewall.


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Grooves and fillet holes

Glue the CF strips to the top of the motor pods using epoxy and tape the strips in place while the epoxy

cures. Trim the CF strips to length after the epoxy is hard. If you want, you can apply some non-shrinkspackle to fill in the area around the CF strips. The bottom carbon fiber strip will be applied after the

motor pods are glued to the wing.

Carbon Fiber Glued

Carbon Fiber Spackled

Now is the time to finish the motor pods by whatever method you prefer, however, no finish is actually

necessary. I applied white Ultracote with a low temperature iron. Do not cover the wing saddle area or

the bottom where the CF strip will be glued. Cover over the grooves for the motor wires and then slit

the covering and press the edges down into the grove. Later, when you put the motor wires in place,

you can cover them with another strip of Ultracote, or just use some scotch tape.


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Motor Pod Covering

Smear some Foam-tac on the inside surface of the servo pocket to toughen it up and then let it dry, then

glue the servos in place. I used a bead of Foam-tac along the top surfaces only, that way I can peel the

glue out to remove the servos if necessary.

Remove the motors from the motor mounts and then attach the motor mounts to the firewalls. Mark

the holes and drill to 1/16. Attach the mounts with 12 each #4 by Phillips pan head self tapping

screws.


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Motor Mount Mounted

Complete the linkages by whatever method you prefer. I used steel clevises instead of nylon just

because I dont like fighting with the screw threads in order to make length adjustments.

Front Linkage

Rear Linkage

This completes the motor pods as much as they can be for now.


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Preliminary TX Programming and Servo Centering

Oddly enough, the first step for building the Bixler is to program the Transmitter. It doesnt need to be

completely programmed, but we want to identify the channels and center the servos so we can mount

the servo arms. The screws that mount the servo arms arent easily accessible so we need to do all this

before we glue the servos in place. Further complicating matters, The KK2 Flight controller has a specificinput range and polarity it wants to see so we need to set up the TX accordingly.

I am doing this with a DX7s, but any 7 channel TX will do. Set all the trims to neutral. Start with a new

model in airplane or acro mode and name the model as you like. Select the wing type with 1 aileron

servo and 2 flap servos. Use the standard tail type, meaning one elevator and one rudder servo. Set the

flaps up on the flap switch with +100% travel with the switch up, -100% travel with the switch down, and

0% travel in the middle. These are just initial values to get the servos moving.

Wing Type Initial Flap Setup

Power the RX by whatever means is handy and bind the TX to the RX. Use a spare servo to map out the

RX outputs. In my case they are as follows. You might find it convenient to label your RX accordingly, if

it isnt already labeled.

1. Throttle2. Aileron3. Elevator4. Rudder5. Gear6. Right Flap7. Left Flap

Now, on the bench, connect the RX outputs to the inputs of the KK2 board. You will need the user

manual for the KK2 Board located here:

http://www.hobbyking.com/hobbyking/store/uploads/181270330X7478X47.pdf

You will also need double ended female servo cables like these.



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Connect the Throttle, Aileron, Elevator, Rudder, and Gear output from the RX into the corresponding

inputs of the KK2 board per the diagram on the front page of the KK2 User manual. The gear output

from the RX will connect to the AUX input of the KK2. The ground pins on the KK2 are along the outside

edge of the board.

When you power up the KK2 board the initial screen should look like this.

KK2 Initial Power Up Screen

Press the MENU button (lower right) and then press the DOWN button, to highlight Receiver Test,

and then press ENTER. You should see a screen that looks like this.

KK2 Receiver Monitor Screen

As you move the TX sticks you should see the numbers changing for the various inputs, and you will also

see helpful words like Idle or Full for throttle to indicate the direction of stick movement. In my case

the aileron and elevator were reversed so I reversed them using the TX programming. Dont worryabout the polarity of the Auxiliary input for now, just make sure it moves when you flip the appropriate

switch.

If you have already set up dual rates or multiple rates, make sure you are on high rates for the next step.

Use your Sub Trim and Travel adjustment (also known as endpoint adjustment) so that neutral stick

reads a count of zero and full stick deflection reads 100 or -100 as the case may be. For the throttle, low


29/95


stick should read zero and high stick should read 100%. You want to make sure that throttle linearity is

maintained by setting the two travel limits to the same value and adjusting the sub trim as necessary.

You will also note that for throttle only, readings below zero or above 100 are not possible. You want to

make sure that full stick travel just barely gets you to zero or 100 as the case may be. You dont want a

lot of travel at either extreme of stick movement where the numbers arent changing, but you do want

to make sure you get to 100 and zero with a small amount of margin to spare.

That is all the TX programming you need to do for now. Disconnect the KK2 from the RX and set the KK2

aside.

You will not want to touch the Throttle, Aileron, Elevator or Rudder trim, sub trim or travel adjustments

again. Do not use them to adjust the centering or travel of your servos. All such adjustments will need

to be made via the linkages. You can and will need to adjust the sub trim and travel for the two flap

servos but they do not affect the KK2. You will also eventually need to adjust the RX Gear output, which

is also the KK2 Aux input, but that is only used as an on off switch when the signal crosses the zero

threshold.

Now plug in your rudder, elevator, and two aileron servos into the RX and set the servo output arm inthe best possible position as limited by the splines on the output shaft. You can do this one servo at a

time if you want. This is not a permanent installation, we are just checking things out. While you are at

it, check the direction of travel for all servos. You cannot change it in the TX as you normally would.

You will need to identify which servos will need to be reversed.

In my case, I needed to reverse the rudder and both ailerons. In the old days we would have opened up

the servos and reversed the wires to the motor and the feedback pot, but that is no longer a reasonable

thing to do. I bought two of these Dionysus in line servo reversers for $11.95 each.

http://www.rcdude.com/servlet/the-19/Dionysus-Servo-Reverser-V2/Detail

I only need one reverser for both ailerons since I can reverse the aileron signal and then use a Y harness

to drive both servos.

Speaking of Y harnesses, I need 3 more to split the Aileron, Elevator and Rudder output from the RX.

One side will go to the KK2, and the other side will go to the servos. In the case of the rudder, it will go

to the servo through the servo reverser. In the case of the ailerons, it will go through the servo reverser,

then through a 4th Y harness to drive both aileron servos in parallel.

The bottom line is that we need 3 short Y harnesses to split the rudder, elevator, and aileron signals

from the RX, something like these for $3.75 each.

http://www.multiwiicopter.com/products/y-lead-50mm-rc-servo-connector-1-male-jr-2-females-futaba

I have been warned not to use the GWS Y harness with reverse that includes a trim pot. I am told it is

very noisy when used with 2.4Ghz radio systems. I am not bashing GWS and I have not personally

experienced this problem, so I am just passing on the warning.

It is unfortunate and almost unnecessary that we need all these Y harnesses and servo reversers. The

KK2 has 8 outputs and could easily drive all 4 motors plus these 4 servos, but it has a feature (bug) that


30/95


prevents its use. If you take the throttle to full idle, all of the motors will go dead, which is fine, but all

of the servos will also go dead, which is unacceptable for an aircraft that can glide.

I am using HEXTRONIK, HXT900, 9 gram servos just because I had them. They are cheap little analogue

servos but adequate for this application. They also didnt fit perfectly in the foam pockets, but a few

minor cuts with a sharp knife will fix that.

Do not permanently mount the servo arms or glue the servos into their pockets until you install the in

line servo reversers. They might change the optimum servo arm position and it is difficult to remove

and reinstall the arms once the servos are glued In place. Once you are sure of the best servo arm

placement, install them with their mounting screws.

At this point the fuselage is still in two halves. Toughen up the servo pockets in the wing and the

fuselage with a coat of Foam-tac and let it dry. Then install the servos and place a bead of Foam-tac

along the exposed surfaces where the servo meets the pocket. The servos are held firmly, but if you

ever need to remove them you can slice through the glue bead. Foam-tac can be peeled off of the

smooth plastic of the servo without too much trouble so nothing is damaged.

Glued in Servo

http://www.hobbyking.com/hobbycity/store/uh_viewitem.asp?idproduct=662&gclid=CKfU6NHn_7UCFa

dFMgodRSAACQ

You will need a somewhat longer Y harness to reach the two aileron servos. Your installation may vary,

but this is what I used.



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Wing Assembly and Mounting to Fuselage

Trim the fiberglass rod wing joiner down to 6 to save a little weight, and round the ends to reduce any

point loading on the inside of the wing tubes. It doesnt really matter much though, because we will be

using external struts to strengthen and stiffen the wing, which is why we dont need the full length

joiner.

Wing Joiner

Use a sharp knife to remove a portion of the overlapping wing bosses as shown in the photograph. This

is necessary to clear a path for wires through the wing and into the fuselage. Glue in the plywoodwashers that came with the Bixler kit and then glue the wing together at the center section with the

fiberglass joiner rod, making sure that the wing halves are aligned front to back. I used Foam-Tac which

takes a long time to dry in areas where it cant breath. You could also use EPOXY, but if you do,

remove the shine from the EPO foam first.

Wing Opening

I do not recommend CA (Super Glue) for use with EPO, at least not the foam safe variety. It doesnt

seem to stick very well, at least not on smooth surfaces. The non-foam Safe CA might work OK, as might

Polyurethane glue (Gorilla glue) but I prefer not to use it as it often foams up and makes a mess. Foam-

tac is very tough and sticks to most everything, but it doesnt sand well. It is fine on Styrofoam like the

blue foam, and on EPO foam, but will eat up Depron if the solvent cant immediately escape. I always

test it first by placing a dab of glue on the material and covering it with some scotch tape to hold the

solvents in. Others may have their preferred glues and assembly techniques.

Sand the top of the wing flat in the area of the two wing mounting holes, and about beyond on both

ends. Try to avoid scuffing up the top of the wing and the decals in the area beyond the raised wing

root. It might be wise to cover this area with some blue painters tape to protect it from the sanding


32/95


block. EPO doesnt sand very easily but it can be sanded. You will need a course grit and some fresh

sharp sandpaper.

Make the wing top plate out of /16 plywood per the provided drawing. I covered mine with Ultracote

on top just to make it look nice. Do not drill the wing mounting holes in the plywood. Glue the wing top

plate in place with the wide part in front, and make sure that it extends evenly beyond the screw mount

holes on both sides. When the glue is dry, you can drill the 1/8wing mount holes through the wing

using the holes in the wing as a template.

Wing Top Plate

Temporarily fit the fuselage halves together and mark the cut locations to remove the area above the

wing per the provided pictures. Carefully cut the top of the fuselage away using a long straight thin

kitchen knife. If the knife is very sharp, the EPO foam will cut like butter. If the knife is dull, you might as

well be throwing baseballs at it. A clean cut will also leave a nicer surface than sanding, so if possible, get

it right on the first cut.

Fuselage Modification


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The wing mount nut plate that comes with the Bixler doesnt have a large enough opening from the

wing into the fuselage, so make a new wing mount nut plate from plywood per the provided drawing.

I installed 4-40 blind nuts and used 2 each 4-40 stainless steel pan head Phillips screws, 2 long, which I

ground to a dull point to make them easier to start. I also opened up the foam in the top of the fuselage

to match the large hole in the nut plate.

Temporarily install the nut plate, and test fit the wing on the fuselage. Install the screws with #6 flat

washers, but only tighten them gently. Glue the flat washers down to the top of the mounting plate so

they dont get lost all the time.

Wing Mounted

Measure and mark the wing for motor pod installation. The centers of the motor pods are 10 3/4 from

the center line of the wing. Also mark 1 on either side of center. The outside mark should be just

slightly inside of the aileron opening. Make the first marks at the slit for the aileron servo wire. Project


34/95


the marks to the leading and trailing edge using the servo wire slit and a 90 degree triangle. It is not

necessary to make full length lines, just small tick marks.

Glue the motor pods in place on top of the wing making sure that everything is straight as it can possibly

be. I used Foam-tac which takes a long time to fully dry. When gluing major assemblies like this it is best

to dry fit everything and figure out how you are going to clamp, tape, or weight everything in place. I

did it with the wing upside down on the corner of the bed with the wingtips hanging off the side/end of

the bed. I put clear plastic wrap over the wing and weighted it down on top of the motor pods with

some books.

Make sure you leave access to view the motor pod position relative to the tick marks you made on the

wing, and triple check for alignment before you walk away to let it dry. Also, make sure that the motor

pods are mounted with the servos facing inward, not outward.


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Fuselage Assembly and Landing Gear

The VTOLT uses Trex 500 helicopter skids, available here for $9.99.

http://www.ronlund.com/rcheli-prod/ALIGN500_LANDING/H50047.html

The Bixler isnt designed for landing gear, so it is necessary to distribute the point load where the gear is

bolted on over a wide area on the underside of the fuselage. I used a 1/16 thick plywood plate along

the bottom of the fuselage and a smaller 1/32 plywood plate on the inside of the fuselage. Together

with some glue and screws they create a foam sandwich.

Foam Sandwich

There are also 2 each 1/8 plywood mount pieces that include 2 each 2-56 blind nuts. Finally, there is a

thick plywood spacer under the rear gear mount to make the aircraft sit closer to level.

Make all of the pieces per the attached drawing.

This time I decided to use a different technique for transferring the paper templates to the plywood.

This very old technique works well for soft materials up to and including plywood. Do not cut out thetemplate, but instead place the paper over the raw material in the desired location. Use a sharp point,

like a T-pin to poke holes through the paper at strategic locations like corners, the center of drill holes,

or in increments around curves. Lift the paper template and connect the dots on the raw material with

a pencil. This technique does not destroy the template or plans and can be done very accurately.

After you cut out and sand to shape the various pieces, The two 1/8 ply cross pieces are glued onto the

outer plate in the location shown. I used CA, but you could also use epoxy. The ply spacer is glued

on top of the 1/8 ply cross piece in the rear. The 2-56 blind nuts go on the top relative to the final

mounting position on the aircraft.


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Landing Gear Plate

It is possible to install the landing gear mount after the fuselage halves are glued together, but not

preferred. It is easier to test fit everything before the fuselage halves are joined, and then install the

landing gear mount at the same time as when the fuselage halves are glued together.

The outer plate and the inner plate are held together by 5 each, 1 long, #4 self-tapping screws with panhead Phillips heads. The screws pass through the seam between the two sides of the fuselage. I opened

up the holes through the foam with a small needle file. When these screws are installed they are only

very gently tightened because they would otherwise crush the foam or strip out the 1/32 plywood. The

strength of the mount does not come from these screws, but from the glue that interfaces a large area

of plywood with the foam. The screws are mostly just to hold it all together while the glue dries.

After the mount was made and the blind nuts installed, I coated it with some thin CA to protect it from

moisture and make it stronger. You could also paint it if you like, but I did not.

Dry fit everything before you attempt to glue the fuselage sides together. You want to make sure every

screw fits every hole and every nut plate can be threaded, etc. Once you apply glue, you wont have

time to mess around.

I used a fresh bottle of Foam-tac to glue the fuselage sides together. This is somewhat challenging as

there are a lot of pieces to get together all at once. The wing mount nut plate has to be glued and

installed, and also the 1/32 plywood inner plate for the landing gear mount. I glued both with a

generous coat of Foam-tac. Once the two fuselage halves are together, tape them with scotch tape in

multiple locations to hold them tight. I always fold one end of the tape under so I have an easy handle

to remove the tape later.

Working quickly, before the glue dries too much, glue the landing gear mount outer plate in place with

Foam-tac, and install the #4 self tapping screws through the foam into the inner plate. Tighten the

screws just enough to ensure a good fit between the plywood and the foam, but no more. Use somescotch tape across the gear mount to hold the fuselage sides tightly together in that area as well.

Now install the T-rex landing gear and the wing, using the mounting screws for both. Set the entire

assembly on its landing gear on a flat surface and check to make sure the wings are level. If necessary,

put a small weight on top of the high wing to push it down past level. Check it again in ten minutes and

as the glue begins to set, move the weight around so that when it is dry the wings are perfectly level.


37/95


Landing Gear installed

Double and triple check everything for fit before the glue sets. Check to make sure all the seams aretight. Make sure you havent pulled a warp into the fuselage. This is your last chance to get it right.

Dont worry if the wings sag a tiny bit at this point. We will be adding the wing struts shortly. I suggest

you let everything stabilize overnight before proceeding.


38/95


Wing Struts and finishing the Bixler

You need to decide if you are going to run the servo wires under the CF stringers on the bottom of the

motor pods or on top. Under is neater, on top is better if you ever have to remove the servo. If you

decide to run the wires under the CF stringer then press the wires into the slot on the underside of the

wing as far as they reach. Place a small piece of scotch tape over the wires in the area where the CFstringer will cross to prevent gluing the CF stringer to the wires later.

Make the 4 wing strut mounts out of the same 1/16 aluminum that you used to make the motor

mounts per the provided templates. The bend angle is 16 degrees.

Carve out a shallow pocket in the wing for each of the four wing mounts. The forward mounts are

located 1 1/8 ahead of the slit for the servo wire. The rear mounts are located flush with the trailing

edge of the wing. The wide part of the mount is located directly under the 6mm x 1mm carbon fiber

stringer on the bottom of the motor pods. The pockets should be only 1/16 deep so that when the

mounts are glued in place, the surface of the mount is flush with the surface of the wing.

Glue the mounts in place with Foam-tac taking care to make sure that the exposed surface of the mount

is clean and free of glue. The critical glue joint will be between the strut mount and the carbon fiber

stringer.

Cut the carbon fiber stringers to length and plan how you are going to tape and weight them in place. I

used the same technique as when mounting the motor pods to the wing. I set the wing upside down on

the corner of the bed with the wingtips hanging off the side/end of the bed.

Smear a heavy cote of 20 minute epoxy on one side of the CF stringer. Use extra Epoxy in the fillet holes

you previously made at both motor mounts, and also on top of the aluminum strut mounts. Place the

CF stringer in place and hold it down with scotch tape. Wipe up any excess epoxy, and then cover the

wing with plastic wrap. Use weights to press the CF stringer down onto the wing taking care not tosmash down the wing strut mounts. Do the same on the 2nd motor pod and let the epoxy cure.

The central strut mount is secured to the landing gear plate using 4 each pan head Phillips, #4 self

tapping screws, long, as shown in the picture.

Lower Wing Strut Mount


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The wing struts are made from 2.5mm, .098, diameter CF rod available for $2.50 each here.

http://www.rcfoam.com/product_info.php?cPath=95&products_id=739&osCsid=f8b889d2908e9589b1

90e4f080364d71

One 1000mm (39) rod is sufficient for all 4 struts. I used Great Planes 4-40 Clevis, GPMQ3795 from my

LHS (Local Hobby Shop). They are available here for $8.49 for a pack of 12, but we only need 8.

http://www.gravesrc.com/GPMQ3795_GP_4_40_THREADED_STEEL_CLEV_12_p/gpmq3795.htm

Screw the wing to the fuselage and turn the aircraft upside down so the fuselage is supported and the

wings hang down slightly due to gravity. Attach all 8 clevises to the mount points and make sure that

the pins are facing towards the wing. This will make them easier to install and remove later. Cut the CF

rod to fit for the wing struts. The rods should extend through the threaded portion of the clevis slightly

on both ends.

Scuff up the outside surface of the CF rods for the last 1/2 with some sandpaper and screw them into

the clevises. The 4-40 threads in the clevises will cut slightly into the rods which is perfect for our needs.Adjust all 4 struts to length and place them in their final location. Sight down the wing and make sure

you are not pulling any warps into the wing with the struts. They should be slightly loose at both ends,

otherwise they are under tension or compression and need to be further adjusted. You may need to use

a 1/16 drill bit and wobble it around in the holes of the aluminum mounts so they dont catch on the

clevis pins due to any slight angular misalignment.

Glued Clevis at Wing Mount


40/95


Wing Struts Mounted

When everything is perfect, carefully remove the struts one at a time and place a drop or two of thin CAinto the joint between the CF rods and the clevises. The thin CA should wick down the threads and also

through the tiny gap where the threaded barrel comes together to lock the assembly in place. Put each

strut back before removing the next so you dont mix up where they go. You can label the struts if you

like, but it should not be necessary. They are designed to remain attached to the fuselage and fold back

along the fuselage for transport. No tools should be necessary for assembly or disassembly of the struts.

You can use the little fuel tubing keepers that come with the struts if you want, but I dont think that

they are really necessary. You can also add balsa fairings to streamline the struts and cover them with

white Ultracote if you want, but I did not.


41/95


Wing Struts Folded Back

Just a few notes on miscellaneous Bixler stuff. This is all unrelated to making a VTOL-Trainer and only

has to do with making the Bixler a Bixler.

I installed all the control linkages using the hardware provided. It all worked fine. They have improved

the fit from the previous Bixler I bought about a year ago.

I dont normally like to add unnecessary weight to my aircraft, but the rubber pilot head they provided

looked pretty nice, so I installed in in the cockpit and mounted the canopy with Formula 560 Canopy

Glue, available here for $3.99.

http://www.horizonhobby.com/products/zap-formula-560-canopy-glue-PAAPT56

I also glued the tail on with Foam-tac. It fit well and went on nice and straight. I installed the magnets for

the cockpit hatch and the bottom servo hatch.

Overall, I have to say the quality of the Bixler kit is pretty good. I also think it doesnt look half bad,

especially with the motor pods on the wing and the helicopter skids, it looks vaguely like a dragonfly.

Except for a little Ultracote on the bottom of the motor pods, this completes the basic airframe build.

The next step will be to finish installing the electronics.


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Power Wiring

Before the power wiring could be completed on the bottom of the wing, the servo leads and any

necessary extensions were pressed into the groves/slits in the bottom of the wing.

Aileron Servo Wires

I connected the 2 aileron servos using a Y harness from GWS, WY/FP/15, available in many places as well

as here for $3.75.


I also connected servo extensions from the two tilt servos and ran them up through the wing.

http://www.rcdude.com/servlet/the-680/Hyperion-Extension-Cable--dsh-/Detail

It is possible to leave a little slack in the servo wires from the tilt servos by pressing the excess wire into

the openings in the bottom of the motor pods. I made pockets in the wing for the Futaba/JR connectors.

The wires were taped over with clear packing tape in the area of the wing root, both to hold the servo

extension connectors in place, and also to protect the wing when mounting the speed controllers. Theservo wires go up through the wing where they will eventually be connected to the RX (Receiver). Note

that I am using up and down relative to the upright position of the final aircraft, not the position

that you might be viewing as you work with the wing upside down on your lap.

Theres a fair amount of power wiring required for a quad-copter and the VTOLT is no different. There is

also some soldering involved but nothing terribly difficult.

I follow several guidelines with power wiring:

1. Keep it as short as reasonable in general.2. Keep the link between the battery and the speed controllers as short as possible, which means it

is better to have the longer link be between the speed controller and the motor.

3. Use the recommended wire gage, or heavier, and use a heavier gage for longer wires.4. Use a minimum of connectors. It is better to solder joints and use connectors only where

needed for component interchangeability.

5. Use a star configuration providing individual power paths to heavy loads.This design is based on the Turnigy 18A speed controllers.


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http://www.hobbyking.com/hobbyking/s...ontroller.html

I made a small mounting plate out of 1/32 plywood, 1 by 1 , and a small plywood spacer on one

end, 1/8 by by 1. I coated them with CA to protect the wood, and then glued them to the speed

controllers with Foam-tac on the top of the round capacitor, and on top of the spacer. See the pictures

for details. You will note that this results in an air gap between the mounting plate and the speed

controller, and it also leaves the side with the heat sink plate completely open for maximum airflow.

Speed Controller Mount Plate

There is an issue with the main battery connector. I find them all difficult to pull apart at times. This is

not so bad when you have an open configuration like a quad-copter, where you can get both hands on it

and work it apart. It becomes much more difficult with an enclosed aircraft if you cant get your hands

down inside the aircraft. It means you need to have the battery connector on the aircraft side stick out

far enough to where you can get to it easily, and this conflicts somewhat with keeping the link between

the battery and the speed controller as short as possible.

For the VTOL-Trainer, the speed controllers are mounted under the wing right next to the fuselage. The

wires go over the wing saddle, down into the fuselage, and forward to come out of the removable

cockpit opening with enough free length to grab onto. The resulting battery to speed controller link

length is about 14, which includes almost 5 of wire that came with the battery.

The reason for minimizing the wire length from the battery to the speed controllers is to avoid damage

to the speed controllers during use. The speed controllers draw pulses of high current from the

batteries, which results in the electrical equivalent of water hammer pounding on the input capacitor

of the speed controller. The longer the wires, the bigger the hammer swing and the bigger the

pounding.


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The point of the star configuration is to minimize the interaction between the various loads. The

VTOL-Trainer has 5 such loads, each of the 4 motors, plus the SBEC which drives all of the radio gear

including the RX, Flight Controller, and servos. The motors draw about 4.5A when hovering, and briefly

up to about 12.5A at full throttle when accelerating out of a hover. Full throttle in forward flight should

draw less, though I have no good way to measure it. As the propellers unload the motors will draw less

current simply because they are delivering less power to the air. The SBEC will probably never draw

more than 2A peak, and most of the time will be much less. There will always be some interaction

between the loads because they all draw from the same battery, but by providing a separate wire path

for each we minimize the interaction due to voltage drops along the wire.

Each speed controller has a 2 wire power input connector. I am using the Female JST gold plated

connector which comes with 20AWG wire and is rated for 18A burst for 10 seconds max, and 12 amps

continuous.

http://www.multiwiicopter.com/products/jst-gold-plated-6-pairs

The wire on these connectors looks to be slightly lighter than the input wire to the Turnigy speed

controllers, so I cut them down to only 1 5/8 and then soldered them to the speed controller wires. Thetotal wire length from the edge of the speed controller to the end of the connector is 5 1/2.

Preliminary Wiring


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Battery Star Connection

Warning, one of my JST connectors had the wire colors reversed. If I had not noticed, this would have

resulted in reverse polarity to the speed controller and likely destroyed it. Double check your pre-wired

JST connectors for polarity, and dont just assume that the wire colors are correct.

The technique for making wire to wire connections is as follows Prepare both wires by stripping the

insulation back 1/8 and then twist the exposed wire into a tight round bundle. Tin the wire ends with a

generous amount of solder, but do not heat them any longer than necessary as the solder will wick up

the wire and make it stiff. Slip a length of shrink tubing over the longer wire and slide it well back

from the joint so it doesnt start to shrink from the heat of soldering. Place a tiny amount of paste flux

on the tinned ends of the wires. Use a weight, or something to hold one wire stationary slightly abovethe work surface. You can bend the wire a little to get i t into a comfortable position. Hold the other wire

in one hand well back from the joint so you dont burn your fingers. Touch the two wires together, side

to side, overlapping by 1/8. Use your other hand to clean the soldering iron tip and then touch it to the

exposed end of your flux core solder to freshly tin the tip just an instant before making the joint. When

making the joint, steady both hands on the work surface to prevent shaking. Lay the soldering iron on

top of both wire ends for immediate heat transfer to the entire joint. The joint will flow almost instantly,

so you can remove the iron in 1 second or less. Hold the wires steady until the joint solidifies. After the


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joint cools, slip the shrink tubing over the joint and shrink it. When done properly, the whole process is

amazingly easy.

The star connection between the battery connector and the 5 JST male connectors is a bit more

challenging mainly because you are connecting 6 things together all at one time. Alternatively you can

buy this wire harness for $9.95

http://www.multiwiicopter.com/products/power-distribution-harness-xt60-jst-5-way

I made my own by jamming the pre-tinned wire ends of the JST connectors into the solder cups of the

XT60 Male connector. They were a tight fit, which actually helped to hold it all together for soldering. It

takes a lot of heat to fully flow the solder through all 5 wires, and it is possible to overheat and melt the

XT60 connector, so be careful. I used the full length of wire that came with the JST connectors, and the

resulting cable is 5 1/8 from end to end.

Instead of using shrink tubing I used Goop to insulate and strain relieve the wires. Goop is basically the

same as Foam-tac but thicker, and is available at any local hardware store. It comes in many forms, like

Plumbers Goop, Household Goop, Automotive Goop, etc. but they are all the same thing.

http://www.kmart.com/Goop

Gooped Connector

The final remaining power connection is between the speed controllers and the motors. Despite the

long wires that come with the carbon bird motors I still needed to add a few inches to the output wires

of the speed controllers.

The CaronBird motors come with the necessary female 2mm bullet connectors that mate with the male

connectors already attached to the motors. They are also rated at 0.0007 ohms and a maximum current

of 30A. If you need to buy more connectors they are available here for $1.98 for a mating set of 10 each.

http://www.hobbyking.com/hobbyking/store/__66__2mm_Gold_Connectors_10_pairs_20pc_.html

I did find it necessary to add shrink tubing to the male bullet connectors that came attached to the

motors to properly insulate them. This was in addition to the shrink tubing that I placed on the female

connectors after I soldered them to the wire.


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I mounted the speed controllers on the bottom of the wing with a few dabs of Goop. It was then

possible to layout the exact path for the wires to the motors and cut the necessary V groves into the

underside of the wing. The idea is to lay the wires in, with one wire on the bottom and two wires on top.

Its probably not critical, but I am trying to minimize the disruption to the airfoil. I also cut slits in the

wing root and pressed the individual wires in place on the battery end of the speed controllers. The

power wires all come together and go down into the fuselage opening, while the 3 pin Futaba/JR type

connectors go up through the wing and will eventually plug into the flight controller or RX.

Wing Center Section Wiring

The wires to the motors have to be almost exactly the correct length since there is no place to hide any

extra slack. They also need to be at least extra long as we will likely need to reverse at least some of

the connections to get the motors to run in the correct direction. Make sure that there is enough service

loop in the wires to allow the motor mounts to rotate without stressing them. Bear all this in mind as

you lay the wires down in the wing groves and cut them to length. The final lap joint is made above the

wing using a piece of cardboard or something to protect the wing in case hot solder should drip or you

should accidentally touch the wing with the soldering iron. Press the wires into the groves and

temporarily tape them in place with scotch tape. We will do a better job of securing them later, after

we get all the motors turning in the correct direction.

Motor Wire Routing


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Motor Wire Routing


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Control Wiring

I purchased the Castle Creations (Switching) CC BEC 10A (peak) at my LHS (Local Hobby Shop).

http://www.rcplanet.com/CC BEC 10A

These SBECs (Switching Battery Elimination Circuit) work by chopping up the battery input DC voltage

into AC, and then use inductors to efficiently translate to the desired DC output voltage. For comparison,

a linear BEC, as is found on most low cost speed controllers, simply dissipates the extra voltage as heat,

which is why they cannot provide very much current to the servos without overheating. A properly

designed SBEC will work over a broad input voltage range and provide a stable output voltage to the RX

so long as the servos dont exceed the rated load. The VTOL-Trainer will never even come close to the

10A peak rating on the CC (Switching) BEC.

Mount the KK2 board using sticky back Velcro on the plywood platform between the two wing mount

screws. Make sure there is a Velcro pad under the button area of the board. You dont want to be

mechanically stressing the board when you push the buttons. It must be mounted with the push buttons

towards the tail of the aircraft. Normally I would be concerned about ESD (Electro Static Discharge) with

electronics of this type, but there doesnt seem to be any other good mounting options.

The RX (Receiver) and the SBEC (Switching Battery Eliminator) circuit are mounted with Velcro on the

wing center section behind the rear mounting screw. Some marketing fool thought it would be clever to

mold the RX enclosure with a wavy surface on one side, so the sticky back Velcro wont stick very well. I

put the Velcro on the flat side, which covers up the output label, and used a fine point Sharpie

(permanent marker pen) to label the RX outputs on the wavy side, which is convenient anyway because I

can use labels like Throttle, Aileron, Elevator, Rudder, Gear, FLP1, FLP2, rather than Ch1,,Ch7. Make

sure you mount the RX where the connectors are easily accessible.

Component Placement


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The primary antenna from the RX was run down through a small hole in the wing and then pressed into

a small slit on the bottom of the wing. The cable for the satellite RX was run through a slit in the back

edge of the wing saddle and then out along the underside of the left wing. Note that the stub antenna

wire on the satellite antenna is mounted 90 degrees to the wire at the end of the primary antenna. This

provides polarization diversity for more reliable radio reception.

Antenna Routing

The SBEC can be mounted wherever is convenient. Connect the output of the SBEC to the bind input of

the RX. I am assuming that you have already bound the RX to the TX. If not, do so now, because it is a

minor pain to do it later.

Use a double ended female cable to connect Ch1 (Throttle) from the RX directly to the KK2 board. Use

the KK2 manual from HK (Hobby King) to determine where to plug into the KK2 board. By the way, whenI speak of male and female, I am always referring to the electrical contacts inside. Connectors often have

female contacts inside a male housing, or the other way round, so there is lots of confusion about what

is what.

http://www.hobbyking.com/hobbyking/store/uploads/181270330X7478X47.pdf


RX Ch2 (Aileron) goes to a short Y harness, and then one side of that Y goes through a servo inverter to

the Y harness that drives the two aileron servos. The other side of the Y goes to the roll input on the KK2

board via a female to female cable.

http://www.multiwiicopter.com/products/y-lead-50mm-rc-servo-connector-1-male-jr-2-females-futaba

RX Ch3 (Elevator) goes to a short Y harness and then one side of the Y goes to the elevator servo. The

other side of the Y goes through a female to female cable to the pitch input of the KK2.

There is a small hole in the fuselage at the back of the wing, that was originally used for the power wires

to the Bixler motor, that can be used to run the wires for the elevator and rudder servos. These two


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connections must be made after the wing is installed on the fuselage. It is a good idea to label the

rudder and elevator connectors since you will be making and breaking them whenever the wing is

removed.

RX Ch4, (Rudder) goes to a short Y harness and then one side goes through a servo inverter before going

to the rudder servo. The other side of the Y goes through a female to female cable to the yaw input on

the KK2.

http://www.rcdude.com/servlet/the-19/Dionysus-Servo-Reverser-V2/Detail

RX Ch5, (Gear) goes through a female to female cable to the Aux input of the KK2. RX Ch6, (RFlap) goes

through a servo extension to the right motor tilt servo. RX CH7, (LFlap) goes through a servo extension

to the left motor tilt servo.

http://www.rcdude.com/servlet/the-680/Hyperion-Extension-Cable--dsh-/Detail

At this point you have a choice to make. Most speed controllers have a built in BEC (Battery Eliminator

Circuit), and it is usually a simple high pass analogue voltage regulator. In theory, you can have multipleBECs of this type driving the same power bus and they wont fight. Its like having 4 people trying to fill

a bathtub to slightly different levels. At some point 3 of them will stop filling because their desired level

has been achieved. The last person with the highest level will win and no one gets upset. So the

question is, will your speed controllers work that way, and are you willing to take the chance on blowing

them up if they dont?

If you dont want to take the chance then you have a few options. One option is to pull the red wire

(middle wire) out of the speed controller connector and fold it back and tape it. If you are careful, you

can pull the contact out of the connector housing without damaging it, so this is a reversible option.

Another option is to remove the power pins from the KK2 board. I did this for motors 2, 3, and 4 by

grabbing the pin with needle nose pliers and then wiggling it back and forth until it broke off at the base.The power from speed controller #1 is still connected to the KK2 board but It has nothing to fight with.

The KK2 manual says that you dont need to do this, but the instructions that come with your speed

controllers may say otherwise. Its your choice.

You should never connect multiple SBECs in parallel as they will fight and probably damage something. I

would also never connect a BEC to an SBEC though I dont know if it would hurt anything. Despite what

it says in the KK2 manual, the KK2 board receives its power from the Throttle, Roll, Pitch, and Yaw

inputs, which come from the RX, which gets its power from the SBEC. The manual claims that the KK2

board receives its power from the M1 connector, which is connected to the BEC inside speed controller

#1. I have checked with an ohm meter, and the power from M1 is not connected to the power from the

Throttle, Roll, Pitch, and Yaw inputs so the SBEC and the BEC wont fight.

Bottom line, connect the 4 speed controllers to the KK2 board outputs for M1 through M4. Make sure

that you connect the correct motor to the correct KK2 output. The left front motor is #1, right front is

#2, right rear is #3, and left rear is #4. The KK2 board will remind you of this once we power it on. It is a

good idea to label the speed controller connectors M1 through M4 for future reference.

After everything is connected you can bundle the wires and tie them down with cable ties. I found this a

bit challenging just because there is a lot of wire and not much room.


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Wires Bundled

Now you can assemble the wing onto the fuselage and make the final connections to the rudder and

elevator servo. I recommend you tape the rudder servo reverser to the mating connector so it doesnt

pull out in flight. Pull the extra length of wires to the rudder and elevator servo down inside the fuselage

and arrange them so they cant get tangled up in the servo output arms. I once crashed because of

that

When putting the wing on the fuselage, feed the main power cable towards the nose so it is accessible

via the cockpit opening.


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Battery Mounting and Wing Tips

We want to place a 1 wide Velcro strip along the inside bottom of the fuselage from under the wing up

well into the nose. You may be using various different size batteries and you want to be able to adjust

the CG (Center of Gravity) as needed. The problem is, the screws sticking up from the landing gear

mount are in the way, so make a filler plate out of 6mm Depron. This Velcro strip gets a lot of abusewhen installing and removing batteries, so I suggest you reinforce the top of the Depron plate with

1/64 plywood. The prototype was reinforced with packing tape, which was not the best choice

VTOLT Build Instructions

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Transcript of VTOLT Build Instructions