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Nov 30, 2006, 08:01 AM
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Build Log

Sportsman Aviation Sonic 500 25-46 ARF

(1) Preliminary Notes and Thoughts:

This is my second ARF assembly from this company. The first one was the Sportsman Aviation Ryan STA 40 ARF. The build thread for that plane is located at:

My original purpose for this plane is to be a “test bed” for some Milwaukee V28/Emoli cells, the Jeti Spin 44-amp brushless ESC and Spin Box and the Sombra Labs Shadow-3 receiver.

The motor is the BP Hobbies (TowerPro) 3520-6. It is a cheap Chinese (maximum 600/700 watt) outrunner that sells for $52.95 at

My original intention was to use a 5-cell Emoli pack. Testing of the motor showed that this was a good option. (See - Section (9) Motor and Prop Data)

A Little History

This was not my first Quickie 500 conversion. In early 1984 I converted a Spickler Quickie 500 to electric power. It is featured in Jim Zarembski’s Silent Power column in the May 1985 RCModeler/RCM. Jim reported on an Electric Flight Symposium that Jim, Art Arro, Keith Shaw and I put on at Salem High School on October 28, 1984. A photo of my conversion can be found on p. 104.

My conversion used an Astro Flight Cobalt 40 direct drive motor, Rev-Up 10x6 wood prop, 18 1200mAh Sanyo cells, JoMar SC-4 or possibly SM-4 ESC, 3 Futaba S-33 servos, 250mAh receiver pack and a Futaba receiver. It weighed about 5 lb. pounds and flew very well as a sport plane for about 6 minutes. It was covered with orange and black Monokote.
Last edited by Ken Myers; Nov 30, 2006 at 08:13 AM. Reason: Added text & photos
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Nov 30, 2006, 08:02 AM
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(2) The Kit:

(2) The Kit:

Sportsman Aviation Sonic 500 25-46 ARF $49.99 (Special Buy)

The kit, ordered from Hobby People, arrived on Tuesday, October 31, 2006. Initial inspection showed no shipping damage.

All of the following weights are out of the box weights with no trimming of the plastic part. All weighing was done using grams on a balance beam scale and then converted to ounces (oz.).

Fuselage: 6.42 oz.
Vertical stab,/rudder/hinges: 0.73 oz.
Horizontal stab/elevator/hinges: 2.32 oz.
Fuselage top/canopy untrimmed: 1.59 oz.
Right wing panel/aileron/hinges/torque rod: 8.68 oz./246.2g
Left wing panel/aileron/hinges/torque: rod 8.90 oz./252.2g
Note: the left wing panel is approximately 1/16” shorter than the right wing panel.
Wing joiner: 0.50 oz./14.3g
Landing gear wire/straps/screws: 1.66 oz.
Aileron servo tray & misc. parts: 0.35 oz.
2 Main wheels: 0.53 oz.
2 wire pushrods: 0.73 oz.
2 aileron pushrods/clevises/keepers: 0.30 oz.
Tail wheel/wire/bracket/screws: 0.52 oz.
Total: 33.29 oz. or 943.7g

Measured Wing chord: 9.96875 in./253mm
Measured Wing Span: 51.3125 in./1303mm
Measured Wing Area: 512^2

The airframe is covered with an unknown red, white and blue iron-on covering. It is difficult to say what type of wood is used in its construction. Whatever it is, it is quite hard and heavy. A well-designed, well-built balsa airframe of similar type could weigh about 2/3 the weight of this ARF. My guess is that it might be some kind of “shipping container” balsawood.
Last edited by Ken Myers; Nov 30, 2006 at 08:16 AM. Reason: Text & photos added
Nov 30, 2006, 08:02 AM
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(3) The Assembly and Modifications

(3) The Assembly and Modifications

Wing assembly:

It should be noted that this is a foam core wing, covered with some kind of wood. The tip ends are either opened forming bays or have ribs. I hope to never find out the actual construction of the wing.

The assembly of the wing was much harder than it needed to be. The torque rod, for the left wing panel, did not move freely. I tried to Dremel it free, but had to remove the trailing edge, free the torque rod from the torque rod bushing and scrape the excess glue from the torque rod so that it would rotate freely in the bushing.

While removing the trailing edge, some of the clear top layer of the cheap covering material pulled away and made the “patch” larger than it needed to be. The clear top layer of the covering on the model pulls easily off of the color layer and the clear layer is easily torn. Of course the Monokote white patch I used did not match the white covering on the model.
There was no mention, in the instructions, of removing the covering material from the torque rod end of the strip ailerons to allow the torque rods to fit into the grove of the ailerons for a tight, gapless fit. Even with the covering removed above the groove on the strip ailerons, I had to use a Dremel tool to make the slot deep enough for the torque rod to ride in and provide a gapless fit. I also had to carefully Dremel and drill out the hole in the aileron stock to align the torque rod correctly in the aileron strip. The way it was originally drilled raised aileron strip end about 1/16” above the mating surface of the wing.

This whole process took a couple of hours, instead of a couple of minutes, before the wing halves could be joined together using 30-minute epoxy.

I modified the aileron servo tray to accept a Hitec HS-85 servo. When I tried to remove the covering for the servo tray, it did not want to come off. The clear layer came off easily, but the white undercoating stayed on and had to be scraped off with a razorblade. The same thing happened when adding the wing bolt reinforcement plate to the underside of the wing.

I put the holes through the wing bolt reinforcement plate and wing covering using a heated soldering iron, which works well in opening up iron-on covering. It took about an hour and a half instead of 1/2 an hour for these steps.

Next I tried installing the blind nuts and wing hold down screws. I modified the provided blind nuts by grinding one side flat so that the nut flange would clear the fuselage side.

The provided screws would not pull the blind nuts into position. I opened up the holes in the in the wing hold downs, but by then the cheap screws had already stripped and would not “pull” the blind nuts into the wood of the hold down.

I started the second day of the build by modifying the elevator so that the modified rudder could pass through it.
I tapped the wing hold-downs for 1/4-20 nylon screws and attached the wing.
The horizontal stab was epoxied onto the fuselage using the wing to align it. Again, the hard to remove covering caused problems. It was very difficult to clear it from where the horizontal stab glued onto the fuselage.

The elevator was finished and attached to the horizontal stab. The slot for the vertical stab was extended into the horizontal stab so that a full rudder could be used. The rudder now extends below the fuselage.

On the third day of the build I fabricated an extension for the provided rudder to convert it to a “full” rudder. The vertical stab was epoxied in place. The extended rudder was finished and the modified rudder hinged onto the vertical stab and fuselage bottom. The original push rod guides were removed and the wood they were attached to Dremel sanded out of the former.

On day four, the rudder and elevator servos were installed after modifying the servo tray to accept the smaller FMA servos. New push rods were created for the elevator and rudder using the provided wire and some dowel rod. The aileron servo was installed into the modified servo tray. The ailerons were then hooked up. The transmitter was set up with the name of plane and the servo throws set to the proper direction and deflection.

On day five the motor mount/cowl holder, that I had fabricated, was epoxied to the firewall.

The slots for the wire landing gear legs in the wings were opened using a hot soldering iron. The main gear and wheels were attached. Flats were ground on the gear wire for the wheel collet’s screw to grab. Thread lock was applied to the collet screws and the screws tightened into the collets. I didn’t cut off the excess gear wire because I thought that I might have to use larger wheels later.

The tail wheel bracket was attached with three screws into CA hardened holes on the fuselage bottom. The tail wheel wire was bent 90-degrees and run through the yellow inner portion of a Nyrod and then epoxied to bottom of new rudder. The tail wheel was positioned and a flat ground for the collet screw on the axle. Thread locked was placed on the screw and the screw tightened on the axle.

The canopy/turtledeck was trimmed and the first coat of paint applied. I ran out of paint, and had to start over with a different paint. The painting was finished later in the day.

On day six, the motor was attached for a quick check of the CG to see where to put the battery tray. The wing was checked to see that it would fit properly with the battery and the rest of the onboard radio components installed.

The radio installation was finished by running the antenna wire to the horizontal stab, Velcroing the Sombra Labs Shadow-3 and Jeti Spin 44-amp ESC into the positions shown in the photo. I had to add a 3.5-inch extension to the Jeti Spin 44 to get it out of the way of the battery. Jeti warns against extending the leads from the ESC to the motor, but I had to do it and it is working. I believe that it just affects the logged data in the ESC.

After the first test flight a pilot and instrument panel were added and the canopy/turtledeck glued on using Tacky glue, a good substitute for RC 56. Tacky glue can be found at craft stores and other places that sell crafts.

My fears about the supplied 2-inch wheels being too small for the grass field I fly from proved to be true and the wheels were changed to some 2.5-inch wheels I had on hand.

The flight surface trims were adjusted based on the transmitter trims. The plane was balanced side-to-side by adding parts of a couple of nails to the right wing tip (~0.23 oz./6.5g). For the security of the canopy/turtledeck, it was, again, glued all the way around with Tacky glue. The ailerons were given more throw. New flats had to ground on the axles for the wider wheels. The collet screws were reinstalled with fresh thread lock on the screws.

Some Final Weights:
The painted canopy/turtledeck weighed 1.57 oz./44.4g
The Fabricated Motor plate: 0.31 oz./8.75g
Didn’t weigh the pilot and dashboard.
RTF weight w/4S1P Skyshark 4000mAh Li-Po: 66 oz./1870g, CWL: 9.84 oz./cu.ft., WL: 18.56 oz./sq.ft.
RTF weight w/5S1P True RC 4000mAh Li-Po: 69.8 oz./1980g, CWL: 10.41 oz./cu.ft., WL: 19.63 oz./sq.ft.

Landing Gear Mod:

After my oopsed landing on November 28, when I loosened the landing gear blocks, I decided to go ahead and install new landing gear blocks in the correct position. I created the new blocks using:
3/16”x5/8”x 3.5” plywood for the base
1/8”x1/4”x3.5” plywood for the top plates to form the groove
1/16”x1/4”x 3.5” balsa to top the top plates and allow easy sanding to the less than 5/32” diameter wire thickness
3/16”x5/8”x5/8” plywood for the “bottom” block

I used straight pins to find the edge of the installed blocks and then marked, cut out and Dremeled out the new area for the landing gear blocks. I was pleasantly surprised to find, not just foam, but some kind of wood actually holding the landing gear blocks in place.
The new blocks were epoxied into place and then more epoxy was added to fill any gaps.

The original groove for the landing gear was filled with balsa and then the whole landing gear area covered with white iron-on covering.

I cut off about 1/8” from the landing gear wire going through the block to make sure it didn’t penetrate the top sheeting. The holes were carefully redrilled to clear any epoxy from them. The gear were reinstalled and the process done in just a few hours, including the epoxy drying.
Last edited by Ken Myers; Dec 01, 2006 at 02:55 PM. Reason: Added Gear Mod & Wing note
Nov 30, 2006, 08:03 AM
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(4) The Power System:

(4) The Power System:

Electronic Speed Control (ESC): Jeti Spin 44 from Hobby Lobby - $141.70

Measured Weight of ESC, leads, and supplied switch: 1.44 oz./40.9g
Measured Weight of ESC, leads, and supplied switch & screws: with 5 Anderson Power Poles/Sermos connectors: 1.68 oz./47.7g
Measured Weight of supplied 2.5mm “bullet” connectors & shrink tube: 0.18oz./5.0g
According to Table 1 provided on the Spin ESC instructions:
Sustained current [A] (2.2Ah batt.): 44 (I don’t understand why a battery capacity is noted here.)
Batteries NiXX/LiXX/voltage: 6-18/2-6/5-26V
According to Table 2:
Max current BEC [A]: 5
Max. servo number: 8 (There is no note or distinction made between analog servos and digital servos, standard servos and micro servos only the 5-amp current rating.)
Resistance in conducting state [m?]: 2x 2 (I have no idea what this means. Anyone?)

The Jeti Spin 44 amp ESC comes with the three extremely short, short motor leads; two battery leads, a receiver lead and a switch lead with the switch. It should be noted that the switch has a red paint “square” on it that indicates the On state not the Off state. All of the leads are attached to the ESC unit. There are five “bullet” type connectors supplied with the shrink tubing to cover them as well as a poorly written instruction sheet. The font size used for the instruction sheet is so small as to be almost unreadable. Hobby Lobby should have noted that this instruction sheet is available online at With the online version being in the Adobe Acrobat format, it is readable and the flow charts are much clearer. Unfortunately, the instruction sheet contains some very “odd” English phrasing. The information regarding the ESC, actually all of the ESC’s in the Spin line, covers only two of the fold fourteen pages of the accompanying instruction sheet and the remainder of the information is about setup and use of the ESC using the “optional” Spin Box.
The ESC contains a switched, instead of linear, Battery Eliminator Circuit (BEC) so that it can use higher cell count/higher voltage batteries with no need for an onboard radio receiver battery.
Setup without the use of the “optional” Spin Box is very limited and uses the throttle stick of transmitter to set the options. The throttle End Points can be set and then there are six preset options to choose from.
Mode 1 Acro inrunner: brake off, timing 0-degrees, gradual power reduction when 68% of starting voltage is reached
Mode 2 Acro outrunner: brake off, timing 24-degrees, gradual power reduction when 68% of starting voltage is reached
Mode 3 Glider inrunner: brake on, timing 0-degrees, gradual power reduction when 68% of starting voltage is reached
Mode 4 Glider outrunner: brake on, timing 24-degrees, gradual power reduction when 68% of starting voltage is reached
Mode 5 Heli constant RPM: “this mode is appointed to model helicopters with the claim or constant speed regulation with changing load/unload of the rotor. This mode does not support fast speed changes” (huh?), timing 0-degrees, gradual power reduction when 68% of starting voltage is reached
Mode 6 Heli constant RPM (3D): “this mode is appointed to model helicopters with the claim” (huh?), timing 0-degrees, gradual power reduction when 68% of starting voltage is reached
Musical tones are played for each mode and repeated five times before moving onto the next mode, which is not noted in the instructions. “Confirmation of the setting is carried out by shifting back the throttle to low throttle position during the tone signals of the factual mode.” (Huh?)
Note that the words in quotes are typed directly from the instruction sheet and have been double checked for typing errors.
That is all you can do without the “optional” Spin Box. (see – Section (8) for information about the Jeti Spin Box)
To me, the default cutoff voltage set at 68% of the starting voltage is a problem. It is typical for me, when using Li-Po batteries, to fly two flights per battery charge. That second flight would be starting at a much lower battery voltage and the cutoff would be below a “safe” Li-Po battery cutoff voltage. Fortunately, I fly timed flights, based on my battery capacity and average amp draw usage, so it will not be a real problem, but it could be for others.

First I set the throttle End Points for my Hitec Eclipse 7 transmitter. There does not appear to be any way to continue the programming without shutting the ESC switch off and the transmitter and then resetting the transmitter throttle to full, turning on the transmitter and then the ESC switch again.
I thought that I had selected mode 2, Acro outrunner, for my BP 3520-6 outrunner. Unfortunately I had not let the ESC play though its 5 tones for mode 1 and had actually selected mode 1, so the timing advance was 0-degrees.
I tested the motor no load and found it to be extremely different (lower) than my data for my TowerPro 3520-7, which had been bench tested with a Castle Creations Phoenix 45 at default settings. It should be noted that my version of the TowerPro 3520-7 is essentially the same motor as the BP 3520-6. Yes, I know the numbers showing the windings are different, but my TowerPro motor tested out to be the –6.
I decided to hook up the Spin Box and see what the timing was set for. It was 0-degrees, so the lower amp draw data made sense. I reset the ESC, using the transmitter throttle stick again to go correctly into mode 2 and the Spin Box then showed a timing advance of 24-degrees, as expected.

BP 3520-6 Outrunner Brushless Motor BP Hobbies - $52.95
Measured motor weight w/leads: 9.27 oz./262.8g
Aluminum motor mount: 0.18 oz./5.1g
4 mount screws: 0.07 oz./2.1g
Prop adapter: 0.78 oz./22.2g
3 Anderson Power Pole connectors: 0.17 oz./4.9g
4 6-32 blind nuts: 0.14 oz./4.1g
4 2” 6-32 screws: 0.42 oz./11.9g
4 1” nylon spacers: 0.08 oz./2.4g
APC 10x7E thin electric prop: 0.67oz./19g
Total weight: 10.98 oz./311.3g
(see – Section (9) for motor and prop data)

Before running the motor/prop tests, sandpaper was glued onto the prop adapter to help the prop grip the adapter when tightening the prop nut.

The aluminum “X” motor mount, provided with the motor, is too “short” and the holes for mounting the motor are too close to the motor body to allow the screws to pass through them in a straight line.

An interesting thing happened when testing the Jeti Spin 44 and this motor. (see – Section (10) Mathematical Motor Modeling, Again)
Last edited by Ken Myers; Nov 30, 2006 at 08:35 AM.
Nov 30, 2006, 08:04 AM
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(5) Onboard Radio Components:

(5) Onboard Radio Components:

Jeti Model Spin 44 w/APP connectors: measured 1.69 oz./47.8g
Sombra Labs Inc. Shadow-3 “Crystal-Less” RC Receiver: measured 0.31 oz./8.85g
6 7/8” Aileron Extension: measured 0.10 oz./2.75g
1 Hitec HS-85BB w/”X” arm, mounting hardware and mounting screws: measured 0.73 oz./20.65g
2 FMA Direct PS100B Mini BB Servos w/”X” arm, mounting hardware and mounting screws: measured 0.69 oz./19.6g each – total measured 1.38 oz./39.2g
Total onboard radio components: 4.2 oz./119.25g
Last edited by Ken Myers; Nov 30, 2006 at 08:36 AM. Reason: Text added
Nov 30, 2006, 08:04 AM
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(6) Flight Report:

(6) Flight Report:

November 24, 2006
I arrived at the Midwest RC field about 1:00 in the afternoon. There was no one there. It was sunny with just a few wisps of clouds in the sky. It was 43-degrees F/6.3-degrees C with a 10-mph/16Kmph wind out of the southeast.
The 4S1P Skyshark 4000mAh battery was loaded into the plane. It had been kept warm in a rice bag* until loading it. The prop was the APC 11x8.5E. The plane had been ranged checked at home. Several attempts were made to get off the field. It had not been mowed since the end of September. It was clumpy, long in parts and had “critter” trails under it. With the landing gear placed too far rearward in the wing and the small wheels, the plane kept nosing over and striking the prop. With no one at the field, I decided to try a takeoff from a bare ground area at the end of the drive. That was successful, although the plane still wanted to rotate forward because of the poor gear placement.
Once in the air the plane needed a bit of up trim and left aileron trim. Much of this first flight was spent flying circuits at greatly reduced throttle while I worked my way back to the flight line. Rolls were slower than I like. The climb rate is very good. Loops are as large as I would like to make them. I tried a couple of snap rolls and they were okay.
The landing was a non-event.
The plane took off at about 62.5 ounces (as the canopy/turtledeck, pilot, dashboard and larger wheels had not been added yet) and just floated in for landing, even much more than I had expected. It was flying fine on the four-cell pack.
I also had a charged True RC 5S1P 4000mAh pack with me and an APC 10x7E, but I elected not to fly with them as I was having a very difficult time orienting on the “white” plane. I don’t know if it was just the way the light was shining or whether I am just too used to my yellow planes. (It turned out that at this time of year it is better for me not to wear my sunglasses when flying this color plane.)
The Jeti Spin 44-amp, BP 3520-6 and Sombra Labs Shadow-3 performed well with no apparent problems.

* rice bag – a kitchen towel that has been turned into a bag with a Velcro top, rice added, heated in a microwave to apply on aches and pains of us old folks and to keep Li-Po batteries warm on cool days. ;-)

November 25, 2006
Three flights were made at the Midwest RC Society field. The temperature was about 53-degees F/11.7-degrees C. The sky was overcast but bright. Wind was from the south at about 5 mph to 7 mph but gusting over 10 mph quite often. Many planes were having a difficult time landing because of the crosswind gusts.
After making several changes as noted in the assembly section, the plane took off from the grass with the larger wheels. It still suffered from trying to flip up on its nose because of the poor gear placement. Using my Skyshark 4S1P 4000 mAh #1 pack, I flew very comfortably for 9 minutes feeling out everything this plane is capable of. It was a good flight with an easy to get to know plane. Refilling the battery the following morning, the AF109 put in 2.283 AH for the nine-minute flight using the APC 11x8.5E prop.
For the second flight my Skyshark 4S1P 4000mAh #2 pack was loaded into the plane. Once again the plane tried to nose over on takeoff. It was a good flight and a lot of fun. Several of the fliers remarked about how well it was flying. The flight lasted ten minutes and a refill of the battery the next day showed 2.888 AH put back into the pack.
Flight three was the first test flight using the True RC 5S1P 4000mAh pack and APC 10x7E prop. I wanted to try and get some flight shots, so Larry Markey took it off and flew it around for quite a long time. He noted that it had plenty of power and speed for him and how well balanced it was. It sure pays off to get the balance for and aft and side-to-side correct. After trying to get some flight shots, I took over the controls and about 6.5 minutes into the flight, the motor shut down unexpectedly. I was sure that it could easily do ten minutes. It restarted in the air, I flew a bit, it shut down again. I kept this up for a couple of minutes and then landed. A good flight!
The next day I measured the voltage of the pack and found that I should have still had quite a bit of flight time with the pack as only 1.720AH were returned by the AF109 charger. I used the Spin Box and found that the ESC temperature had reached 100-degrees C and I had the cutoff set at 99-degrees. That explained the on/off behavior of the ESC during that flight. I have since reset the maximum temperature before cutoff to 102-degrees C, the maximum allowed by the controller.

November 26, 2006
Three flights were made at the Midwest RC 5 Mile Rd. field. The sky was gray but the temperature was about 57-degrees F/13.9-degrees C. Winds were still from the south, but low enough not to be a factor.
Flight 1 was flown with the 5-cell pack, and again the ESC started cutting off at about 6.5 minutes. I believe it had hit the high temperature cutoff again, so I have moved the temperature setting up the ESC maximum of 110-degrees C. The rough field did in my APC 10x7E prop on landing.
Two more flights were taken using the APC 11x8.5E prop and the two Skyshark 4S1P 4000mAh packs. One flight was about 9 minutes and, using the second pack, the second over 10 minutes.
The plane is flying really well. I did just about every maneuver that I know how to do. Spins are especially nice. The avalanche requires a little different timing than most of my other planes, but turns out well.

November 27, 2006
The ambient temperature was near 60-degrees F/15.6-degrees C. Winds were out of the southwest at about 10mph/16Kmph with a gray but bright sky. Three more flights were flown. Again, the ESC shut off early when using the 5S1P pack because of it being “over temperature”. That is quite disappointing. All flight were good and it is a pleasure to fly this plane.

November 28, 2006
The ambient temperature was near 60-degrees F/15.6-degrees C. Winds were out of the southwest at about 10mph/16Kmph with a bright blue sky. The first oops occurred. I flew the 5S1P pack and it again shut off again at about 6.5 minutes. I misjudged the landing and kind of nosed in breaking the prop and the right landing gear block area. When I fix it, I will be making new gear blocks and moving the gear forward. Landings and takeoffs with the stock gear placement are just too nasty for me.
Last edited by Ken Myers; Nov 30, 2006 at 09:12 AM. Reason: Added Text & Photo
Nov 30, 2006, 08:05 AM
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(7) Conclusion:

(7) Conclusion:

The Plane:
When properly balanced and trimmed the plane flies well and is fun to fly. There are several building annoyances and a major design flaw.

The good stuff:
1. The plane is easy to fly and land and performs all sport pattern maneuvers well.
2. It is inexpensive.
The Not so Good stuff:
1. The landing gear is misplaced on the wing causing nose-overs and other difficulties on takeoff and landing on “tufted” grass fields.
2. The wing hold down screws and blind nuts do not work well as supplied and the screws are easily stripped.
3. The covering material is not easily removed for gluing on the necessary pieces and is just plain bad.
4. The supplied wheels are too small for the grass fields I fly from.
5. The wood used in the construction of the model is too heavy.
6. The canopy/turtledeck is difficult to fit as the top of the fuselage is not flat and the bottom of the canopy/turtledeck is.
Other notes:
If a three cell Li-Po pack is used, it would be a good idea to move the servos into the area forward of where they are located as the unit is shipped.
I have my CG set at about 3.25” back from the leading edge of the wing, and that seems just about right for my style of flying.
I plan to do surgery on the wing this winter and move the landing gear into the proper position for this type of tail-dragger. That means that the gear axles should be lined up under the leading edge of the wing.
Basically, you get what you pay for.

The Jeti Spin 44:
The ESC seems to perform well with a 4S1P pack but has caused endless problems with premature cutoff when using the 5S1P pack. The switching BEC seems to be a nice, built-in function.

The Jeti Spin Box:
It works well to fine tune the parameters of the ESC and is relatively easy to use. I like the idea that it is easy to take to the field to make changes, just like when I use my Emeter with my Hyperion ESC.
It does not appear to be very accurate in the logging data. There are many unexplained functions and the instructions need a major revision and update to include the servo testing function.

The BP Hobbies BP 3520-6:
It performs as expected, is reasonably efficient and is a good value. The “X” mount needs a major revision to allow the motor mount screws to fit properly.

The Sombra Labs Shadow-3 Receiver:
This is the third one I’ve had and the first one to work for me. It appears to be working well, but I have not flown it in a rich “RF environment” yet.

The Emoli pack:
I have not purchased one yet, and all of the testing to date has been done with Li-Po batteries. I will not be purchasing an Emoli pack until spring is right around the corner because I don’t want it setting on the shelf dying. I am NOT a winter flier!
Last edited by Ken Myers; Nov 30, 2006 at 08:48 AM. Reason: Added Text
Nov 30, 2006, 08:05 AM
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(8) The “Optional” Jeti Spin Box from Hobby Lobby - $48.20

(8) The “Optional” Jeti Spin Box from Hobby Lobby - $48.20

The Jeti Spin Box, a 12-inch extension with the same JR-type connectors on both ends and the identical instructions packaged with the ESC came in a plastic, reclosable bag.

Using the Spin Box for the first time presented a problem. The instructions say, “Plug in the JR connector of the controller into the plug designated Impuls + - , which is positioned on the right side of the JETI-BOX.” The instructions also note, “Do not connect anything to the connector designated with -+ .”

A photo shows a three pin JR-type connector (on the left) with what looks something like a Pi symbol then a + in a circle and a – in a circle on a light blue background. The three pin JR-type connector on the right has nothing over one pin then a + in a circle and a – in a circle on a white background. (According to what I read on Dec. 9, it is a gray background. If that is so, it is very, very light gray.) There is no connector on the box with a -+, in that order.
I had a 50/50 chance of being right and chose the connector with the symbols on the light blue background. It appears to be the correct one.

When the ESC’s JR-type connector is plugged into the Spin Box, the power flight battery connected to the ESC and the ESC switch turned on (moved toward the red square) the display shows the name of the attached controller and, by using the membrane arrow keys on the Spin Box, can provide the basic information about the controller.

Pressing the down arrow key, while the initial recognition screen is available, shows a screen that reads MeasureOrSetting. If the left arrow key is pressed selecting MAN, it leads to the menu to retrieve the stored values from the most recent motor run. If the right arrow key is pressed with the MeasureOrSetting screen visible the Auto set menu is selected and the auto set choice can be selected with the down arrow key. For me, these had already been set using the transmitter throttle stick. Pressing the down arrow key from the MeasureOrSetting screen allows for a review or changing of the ESC parameters.
Originally, I had already run the motor for a no load test and I decided to look at the measured stored values first to become familiar with the unit. I also collected the data after the first flight using the Skyshark 4S1P 4000mAh battery and APC 11x8.5E prop and then again after the flight using the True RC 5S1P 4000mAh battery. For the data below NL is the no load data, 4S is the data for the 4S1P setup and 5S is the data for the 5S1P setup.

NL - Max. Temperature: 32-degrees C time 02:11
4S – Max. Temperature: 85-degrees C time 08:43
4S – Max. Temperature: 87-degrees C time 07:50
4S – Max. Temperature: 18-degrees C time 00:58 (comparison test 12/08/06)
5S – Max. Temperature: 100-degrees C time 06:59 (note: there is a fault in the temperature in the last data provided)
5S – Max. Temperature: 111-degrees C time 06:31
This was useful in diagnosing why the ESC cutoff during the 5S flight.

NL - Min. Temperature: 18-degrees C time 00:00
4S – Min. Temperature: 16-degrees C time 00:00
4S – Min. Temperature: 23-degrees C time 00:00
4S – Min. Temperature: 11-degrees C time 00:00 (comparison test 12/08/06)
5S – Min. Temperature: 11-degrees C time 00:00
5S – Min. Temperature: 20-degrees C time 00:01
I found the 4S/5S data odd, since the ambient temperature was warmer when the 5S pack was flown.

NL - Actual Temperatu: 15-degrees C
4S - Actual Temperatu: 12-degrees C
4S – Actual Temperatu: 11-degrees C
4S – Actual Temperatu: 10-degrees C (comparison test 12/08/06)
5S - Actual Temperatu: 11-degrees C
5S – Actual Temperatu: 14-degrees C
I have no idea what this means. I believe the word Actual needs to be defined or retranslated.

NL - MaxCurrent: --A, --,--V
4S – MaxCurrent: 40,5A, 14,19V, 01:45
4S – MaxCurrent: 39,3A, 14,19V, 01:39
4S – MaxCurrent: 35,5A, 13.11V, 00:53 (comparison test 12/08/06)
5S – MaxCurrent: 43,7A, 17,98V, 03:41
5S – MaxCurrent: 41,7A, 18,88V, 02:11
During the no load test, nothing recorded. It appears that the unit cannot measure amps under a certain low point. It should be noted that a comma is used as a decimal point in Europe.

NL - MinCurrent: 00,0A 19,49V (The European comma is equivalent to a decimal point) time 02:10
4S – MinCurrent: 26,4A, 13,93V, 08:27
4S – MinCurrent: 21,5A, 14,30V, 05:31
4S – MinCurrent: 33.1A, 12.91V, 00:58 (comparison test 12/08/06)
5S – MinCurrent: 25,8A, 18,27V, 06:03
5S – MinCurrent: 25,4A, 18,41V, 04:33
It is not explained as to what is being recorded here or why.

NL - Max Voltage: 19,95 V time 00:00
4S – Max Voltage: 17,10 V time 00:00
4S – Max Voltage: 16,95 V time 00:00
4S – Max Voltage: 16,87 V time 00:00 (comparison test 12/08/06)
5S – Max Voltage: 21.49 V time 00:00
5S – Max Voltage: 21,49 V time 00:00
This seems to be the battery voltage when it is plugged in.

NL - Min Voltage: 19.26 V time 02:04
4S – Min Voltage: 13,19 V time 00:03
4S – Min Voltage: 13,16 V time 08:10
4S – Min Voltage: 12,91 V, 00:58 (comparison test 12/08/06)
5S – Min Voltage: 17,72 V time 06:12
5S – Min Voltage: 18,01 V time 02:46
It is not explained as to what is being recorded here or why.

NL - Actual Voltage: 12,79 V (“Instantaneous battery voltage.” Huh?)
4S – Actual Voltage: 12,76 V
4S – Actual Voltage: 12,76 V
4S – Actual Voltage: 16.81 (comparison test 12/08/06 This one doesn’t seem to fit the pattern and I have no idea what it is trying to show.)
5S – Actual Voltage: 12,76 V
5S – Actual Voltage: 12.74 V
It is not explained as to what is being recorded here or why. Again, I feel the word Actual is mistranslated. I find it curious that all of these “Actual Voltages” are basically the same.

NL - Off Voltage: 19,75 V time 02:11
4S – Off Voltage: 14,99 V time 07:05
4S – Off Voltage: 14,45 V time 08:30
4S – Off Voltage: 15,33 V time 00:58 (comparison test 12/08/06)
5S – Off Voltage: 19,09 V time 06:12
5S – Off Voltage: 19,29 V time 06:31
This appears to be the unloaded battery voltage when the motor is last turned off.

NL- Motor Run Time: 00:35 s
4S – Motor Run Time: 06:48 s
4S – Motor Run Time: 07:47 s
4S – Motor Run Time: 00:13 s (comparison test 12/08/06)
5S – Motor Run Time: 05:34 s
5S – Motor Run Time: 06:02 s
Appears to be the time the motor was actually run during the session in minutes and seconds.

NL - Power ON Time: 02:11 s
4S – Power ON Time: 09:53 s
4S – Power ON Time: 09:45 s
4S – Power ON Time: 00:58 s (comparison test 12/08/06)
5S – Power ON Time: 08:49 s
5S – Power ON Time: 07:38 s
Appears to be the time in minutes and seconds that the ESC is turned on.

MOTOR POLE NO.: 14 (I set this by checking the BP Hobbies Web site.) and it is the same for all three examples.)

Gear: 1:1,0 (default setting) – same for all three examples.

NL - Max motor RPM: 14880 time 02:05
4S – Max motor RPM: 31240 (forgot to note time) (note: there is a fault in the U (volts) for the last data given)
4S – Max motor RPM: 09660 time 02:32
4S – Max motor RPM: 08370 time 00:53 (comparison test 12/08/06)
5S – Max motor RPM: 12490 time 02:12
5S – Max motor RPM: 12330 time 04:34
These RPM do not match those taken by my Hyperion Emeter and Hobbico Optical tachometers. The numbers given by the Spin Box are many hundreds of RPM higher than those shown on the optical tachometers.

NL - Max prop RPM: 14870 time 02:05 (Interesting that this is different than the above when it is a 1:1,0 gear ratio.)
4S – Max prop RPM: 31240 (forgot to note time)
4S – Max prop RPM: 09660 time 02:32
4S – Max prop RPM: 08360 time 00:53 (comparison test 12/08/06 Notice the 10 RPM difference from the motor RPM. I’ve seen this quite a few times and don’t under stand why when it is a direct drive motor.)
5S – Max prop RPM: 12490 time 02:12
5S – Max prop RPM: 12330 time 04:34
These should only be different when gearing is used.

NL - Errors: U=n, T=n, C=n, I=n (n indicates that the voltage (U), temperatures (T), commutation (C) and current (I) had not been exceeded. A y would indicate it had.
4S – Errors: U=y, T=n, C=n, I=n
4S – Errors: U=n, T=n, C=n, I=n
4S – Errors: U=n, T=n, C=n, I=n (comparison test 12/08/06)
5S – Errors: U=n, T=y, C=n, I=n
5S – Errors: U=n, T=y, C=n, I=n
It can be seen that there was a voltage error during the 4S run, thus the unreal RPM data and a temperature error during the 5S run, explaining the early cutoff.

Next, to learn what parameters can be user set for the Spin 44 I looked at the ESC setting parameters.
ESC Setting Parameters:
Temp. Protection: 99-degrees C (default – can be increased or decreased as the user desires up to 110-degrees C. My current setting is now at 110-degrees C)
Brake: Off (can be changed to soft, medium, hard or manually programmed)
Operation Mode: Aircraft (other choices include; Heli normal, Heli(ConstRPM), and Heli(C.RPM) 3D)
Timing: 24-degrees (this is the default outrunner setting but can be changed from 0-degrees up to 30-degrees. My current setting is 0-degrees)
Frequency: 8 kHz (the only other choice is 32 kHz for iron free motors like Tango & Samba)
Acceleration: 0-100% 1,0 s (The instructions note: “On principle – the larger the propeller, the longer the acceleration time value must be. For big reversed motors apply an acceleration time of 2 and more seconds. For model helicopters we recommend acceleration times of 5 and more seconds.”)
Accumulator Type: Li-Ion/Li-Pol (the other selection is NiCd/NiMh – accumulator is a European word for cell)
NUMBER OF CELLS: LiIo/Po AUTO (there is no arrow on the screen but pushing the right arrow key increments the cell count from 2 – 6. My current choice is AUTO)
LiIo/Po CUT OFF V PER CELL: 2,8 (again there are no arrow indications but pressing the left arrow decreases the voltage and pressing the right arrow increments the voltage.)
Off Voltage Set: 08,37 V (this was with a 3S1P pack being used as the power source. When I changed to a 4S1P pack the off voltage was set to 11.37v)
CUT OFF: SLOW DOWN (The other choice is HARD, which immediately stops the motor.)
INITIAL POINT: AUTO (Fixed and chosen. Regulates the stop position of the throttle.)
END POINT: 1,80 ms (This is the Full Throttle value. I did that with the original transmitter setting.)
AutoInc.END POIN: ON from 1,80ms
THROTTLE CURVE: LINEAR (Other choices include Logarithmical if most of the
flight time is carried out within a region of 50% of full throttle and Exponential.)
ROTATION: LEFT (Can change to right here without having to swap two motor leads. I actually ended up changing this to RIGHT for use with my outrunner.)
TIMING MONITOR: OFF (If this option is turned ON, then the timing is noted as a series of musical tones when the ESC is initiated.)
To save changed settings, turn off the ESC switch.

The Spin Box can be used with a receiver battery instead of the flight battery.
For use with the ESC:
1. Plug the ESC JR-type connector into its position under the light blue background label.
2. Plug a 4-cell (I don’t know if a 5-cell will work) receiver battery with a JR-type connector into the JR-type connector under the white background label and immediately switch on the ESC. Read stored values or setup, as you desire. Reading stored values would be the best option, as some of the setup values require the actual flight battery.
For use as a Servo Tester:
1. Plug a servo with a JR-type connector into the connector where the ESC usually plugs into the Spin Box and a receiver battery into the white background connector on the Jeti Spin Box. The screen reads, “IMPULS GENERATOR” and the options are YES or NO. Pressing YES for the servo I had plugged in read, “IMPULS GENERATOR: 1,541 ms 5,22 V” but I have no clue as to what it is telling me.
2. If NO is chosen, the screen then reads, “SERVO CYCLE: YES NO” If YES is chosen the number of cycles may be selected and OK starts the cycling. It runs through the number of cycles selected displaying some information I am not familiar with.
3. If NO is chosen from the above screen, the next screen reads “SERVO SPEED Tst. YES NO” The high and low positions are selected and then a Servo Speed screen appears with a number like 0.109 s for the servo I tested.

When in the Servo Tester Mode, I really only understand what the Speed Test is telling me.

12/08/06 Recheck of Data Logging

I used a 4S1P Skyshark 4000mAh Li-Po battery that had a bit of runtime on it to check the Data Logging function of the Jeti Spin 44 against the data collected by my Hyperion Emeter and Astro Flight Whattmeter. The Emeter and Whattmeter were placed inline so that all readings could be made simultaneously. I could not compare the RPM reading on this day, as I had to do the test in the basement. The outside temperature was about 20-degrees F/-6.7-degrees C, which is just too cold to set up the video camera to get the optical tach/Whattmeter measurements outside in the sunlight.
I was able to get the volt and amp readings. After “playing” with the Spin Box for a while it seems that the reading to use for comparing is called “MinCurrent”, as that appears to be the last current data taken before throttle is shut down for the final time. I watched the Whattmeter and used the hold function of the Emeter just before shut down and captured the following:
Jeti Spin Box: MinCurrent – 33.1 amps, 12.91 volts, time 00:58 (that was shutdown time)
Hyperion Emeter: 31.1 amps, 12.83 volts
Astro Flight Whattmeter: 31.4 amps, 12.5 volts
The Whattmeter and Emeter are within 1% of each other for amps and 2.6% for volts.
The Spin Box differs with the Whattmeter 5.4% for amps and 3.2% for volts.
The Spin Box differs with the Emeter 6.4% for amps and 0.6% for volts.
These seem like relatively small differences overall, yet, it still bothers me.
One thing I did notice was that when using the 5S pack and the ESC goes over temp and starts lowering the power, the lower power is what gets recorded as the MinCurrent before the shut off of the ESC. Also, restarting the motor to “stretch” the landing or taxi back to the pits, changes the saved values.
If data logging is important to you, you are probably better of to use something like the Eagle Tree Systems MICROPOWER E-LOGGER & POWERPANEL (
Just for archiving purposes I’ve added the comparison run data to the measured data section.

“Found” December 9, 2006
A well-known national RC magazine author had sent me a lot of information he had on the Spin Box in the late summer, as he had done a product introduction about the Spin controllers and Spin Box. I did not open it until today, as I did not want anything he said influencing what I was writing. I found an interesting document enclosed. It appears to be from Jeti Model, yet it is not online, that I can find, and did not come with anything I received from Hobby Lobby. I have taken the time to retype it here, and it does answer some questions about using the Spin Box as a “tester” unit. I have double-checked this retyped document for accuracy and have typed the misspellings, formatting and punctuations as they appear on the document.


Utilization of the JETI Box as a self contained unit:
1. Measurement of receiver channel outputs pulse widths
2. Servo pulse generator
3. Servo cycler
4. Measurement of servo transfer speeds
5. Communication with controllers SPIN (see controller Spin operating instructions)

For application #1 you need a receiver, transmitter and receiver batteries (4,8-6V). Plug batteries into socket GRAY, receiver to socket BLUE, both on the right side of the JETI Box.
For applications #2, #3 and #4 you need the receiver batteries (4,8-6V) and a servo.
Connect the batteries to socket B and the servo to socket A.
In case of change of the application you must disconnect the supply battery from the JETI Box and activate them again. In order to choose the required application use the push buttons P and L.
If you do not have RX batteries or another kind of voltage source (range 4,8-6V) you can supply the JETI box from the BEC of the controller. Plug the JR connector of the controller into socket B (pulse (orange cable) into the unmarked position). Connect the flight batteries to the controller an switch on the switch (if available).

2. Measurement of receiver channel output pulse widths (I think this should have been numbered 1. KM)
By means of this application the width of the output pulse of any arbitrary Rx channel output can be measured. Furthermore, measurement of the receiver battery supply voltage is also possible.
Connect the receiver batteries to the receiver. With the aid of the connecting cable as delivered along with the JETI Box connect socket A with a definite RX channel output.
Switch on the transmitter and receiver. The display shows now IMPULS DETECTION and you can read the values of the output pulse width in ms and Rx battery voltage.

2. Servo pulse generator (yes, it was numbered 2 again KM)
This JETI Box application renders the generation of servo controlling pulses as well as the measurement of the servo supply voltage possible. By means of the push-buttons you can change the range from 1,024 ms to 2,047 ms either in steps of thousendth of hundredth of a ms. This function is for instance very well suited for setting the center position of a servo (1,500 ms) without receiver and transmitter. Connect batteries and servo.
The pulse width can be set by means of all four push-buttons.
With push-button L the pulse becomes narrower in steps of 0,001 ms
With push-button D the pulse become narrower in steps of 0,01 ms
With push-button N the pulse becomes wider in steps of 0,01 ms
With push-button P the pulse becomes wider in steps of 0,001ms

3. Servo cycler
In this application it is possible to set the number of cycles, the servo throw and the cycling speed. This item serves for verification of longevity, burning in and function tests of servos.
Connect batteries and servo and choose by means of push-buttons L and P the function SERVO CYCLE.
By push-buttons N and D set the number of cycles from 10 to 990 (setting in steps of ten cycles).
The speed can be set from 1 to 99 by push-buttons L and P. A speed of v=1 means that every following pulse in comparison with the foregoing pulse will change by 0,001 ms until you reach the limit position (analogous v=20 means a change by 0,020 ms). The pulse period is 20 ms.
By means of push-buttons N and D a value can be set which defines the servo throw in µs, doing from 100 to 500 µs from the center position of 1,5 ms.
If the setting is ?=500 µs the control pulse for the servos will change from 1,000 ÷ 2,000 ms (i.e. 1,500 ms ± 500 µs). The value after # gives the number of cycles which are still left until the end of the test.
When the test is finished the program returns back to the start SERVO CYCLE.
4. Measurement of servo transfer speeds
By means of this test we can find out how much time the servo needs to transfer from one defined position to the other one. Measurements can be carried out without load or with the servo directly installed in the model at real lever conditions.
The pulse width of the first limiting servo position can be set within a range of 1,024 ms to 1,400 ms and the second one within 1,600 ms to 2,047 ms. If we want to measure the speed when the servo output shaft turns for instance by 60º, we have to adjust this angle for instance with a protractor.
Connect the battery and the servo, by means of the push-buttons L and P select the function SERVO SPEED.
By means of the push-buttons N and D set the first limit position of the servo. Proceed with push-button P until you reach the second limit position, which also must be adjusted by push-buttons N and D.
Start the test.
On the display you will read the resulting time in seconds, which the servo needs for the transfer from one set position to the other one. This measurement can be repeated several times or you can set different limit positions.

We wish you a pleasant time and much fun with our products.

JETI model

(It should be noted that there is no #5 on the sheet that I have. KM)

After my initial run through, I had several questions about the Jeti Spin Box. Emails were sent to and to Jason Cole at Hobby Lobby.

1st email: Questions about the Jeti Spin 44-amp ESC and Jeti Spin Box.

What is the difference between Min. Temperature and Actual Temperatu? Is either one of them the ambient temperature of the ESC?

What does Actual Voltage mean? The instructions state, “Instantaneous battery voltage.” What does that mean?

Why would the Max motor RPM: 14880 time 02:05 and the Max prop RPM: 14870 time 02:05 be different on a direct drive motor? The numbers came from one of my “tests.”

Does your word “Impuls” mean signal in English? Does the symbol that looks something like Pi mean signal?

Why are there no instructions about using the Spin Box with a receiver battery?

Why are there no instructions about using the servo tester function of the Spin Box and what the information during the servo testing is telling the user?

Why for Sustained current [A] (2.2Ah batt.) do you designate a battery Ah?

What does Resistance in conducting state [m?]: 2x 2 mean?

The Spin Box instructions note, “Do not connect anything to the connector designated with -+ .” There is no -+ on the Spin Box. What did you mean to say?

Why didn’t you say that shutting off the ESC switch or pulling the ESC plug saves the changes made to the ESC programming?

2nd email: Another question about the Jeti Spin Box
I cannot get a reading for the no load current of about 4 amps on the Spin Box. Yes, I held the throttle wide open for more than 5 seconds. What is the minimum MaxCurrent that can be measured?

3rd email: Big Problem

I ran into a HUGE problem this morning with the Spin Box captured data. I was using my Emeter and gathered and held data on RPM, volts and amps at full throttle. It did not come close to matching the data retrieved from the Spin Box. Spin Box data was about 9200 RPM, 37+ amps and unknown voltage (didn’t write it down) while the Emeter was 8700 RPM @ ~32 amps. Okay, Emeter could be wrong. Got out my Hobbico Mini-tach and Astro Flight Whattmeter. I continued testing on the same pack and the Emeter, Mini-tach and Whattmeter were very close in readings while with the Spin Box was hundreds of RPM higher, usually 3 to 5 amps higher on the amp readings and usually 0.5v or more higher on the voltage. This is not good and I find it unacceptable. Suggestions?

On November 13 I received an email from Jason Cole that said he passed my questions and comments onto Mike Hines. I have not heard from Mr. Hines.

On November 20 I received the following email from Jeti Model. It did not address the first two emails I sent. I was not very happy with this reply.

“Dear sir,
RPM of motor are measured by incoming frequency to the motor. If it is right set number of motor poles, I do not suppose any significant difference.
Situation with current measuring is more problematic due to method of measuring (voltage drop on power FETS).
In this case is difference up to 10% accepted.
Best regards J.Tinka

JETI model s.r.o.
Kadláãkova 894
742 21 Kop?ivnice
Czech Republic”

Note: Also see Tom Hunt's review and comments on the Spin controllers and SpinBox in the June 2007 issue of FlyRC p.140 - p144
Last edited by Ken Myers; Apr 08, 2007 at 02:38 PM. Reason: Did comparison test; Spin Box/Emeter/Whattmeter
Nov 30, 2006, 08:06 AM
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(9) Motor and Prop Data:

(9) Motor and Prop Data:

Data: (Elevation: Walled Lake, MI 938 ft./286m, Ambient Temperature: ~63F/17.2C, Barometric Pressure: 30.36 in./1017.3 steady, Humidity: 78%)

Generator Test: Mfg. Avg. Kv from generator test: 737
RPM: 1560 Volts AC RMS: 1.577 * 1.414 vpk = (2.229878 * (1000/RPM) 0.641025641) = a. 1.429409
Kv= 1/a. 0.699589843 * 1000 = 699.5878 / 0.95 = 736.4
RPM: 1560 Volts AC RMS: 1.581 * 1.414 vpk = 2.235534 * (1000/RPM) 0.6410256 = b. 1.4330346
Kv= 1/b. 0.6978198 * 1000 = 697.81985 / 0.95 = 734.5
RPM: 1560 Volts AC RMS: 1.568 * 1.414 vpk = 2.217152 * (1000/RPM) 0.6410256 = c. 1.4212513
Kv= 1/a. 0.7036053 * 1000 = 703.60535 / 0.95 = 740.6

Speed Control: Jeti Model Spin 44 with 24-degrees timing advance (default)

Average Data using Hyperion Emeter:
Battery: Skyshark 4S1P 4000mAh Li-Po
APC 11x8.5E, 13.09v, 32.376 amps. RPM 8514, Watts In 424, Pitch Speed 68.5 mph/110Kmph
APC 12x6E, 13.484v, 30.794 amps, RPM 8934, Watts In 415, Pitch Speed 50.8 mph/82Kmph
APC 11x7E, 13.296v, 28.688 amps, RPM 8798, Watts In 381, Pitch Speed 58.3 mph/94Kmph
APC 10x7E, 13.496v, 24.252 amps, RPM 9174, Watts In 327, Pitch Speed 60.8 mph/98Kmph
Battery: True RC 5S1P 4000mAh Li-Po
APC 10x7E, 17.028v, 38.748 amps, RPM 11280, Watts In 660, Pitch Speed 74.8 mph/120Kmph
1. Readings were taken on the same fully charged battery in the order of 12x6E, 11x8.5E, 11x7E, 10x7E

Wanting to see how the ESC timing affects the motor, I set the timing to 0-degrees using the Spin Box and took the following readings on a freshly charged battery:
Average Data using Hyperion Emeter:
Battery: Skyshark 4S1P 4000mAh Li-Po
APC 11x8.5E, 13.304v, 31.37 amps, RPM 8472, Watts In 417, Pitch Speed 68.2 mph/110Kmph
APC 12x6E, 13.618v, 29.154 amps, RPM 8772, Watts In 397, Pitch Speed 49.8 mph/81Kmph
APC 10x7E, 14.016v, 23.554 amps, RPM 9264, Watts In 330, Pitch Speed 61.4 mph/99Kmph
1. Readings were taken on the same fully charged battery in the order of 11x8.5E, 12x6E, 11x7E, 10x7E
Battery: True RC 5S1P 4000mAh Li-Po
APC 10x7E, 17.358v, 35.49 amps, RPM 11100, Watts In 616, Pitch Speed 73.6 mph/118Kmph
Last edited by Ken Myers; Nov 30, 2006 at 08:58 AM. Reason: Added Text
Nov 30, 2006, 08:07 AM
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(10) Mathematical Motor Modeling, Again

(10) Mathematical Motor Modeling, Again

For many of us in electric flight, trying to predict how a new, unknown power system (motor/battery/prop) will behave has become a major pursuit. I have published many, many articles on this topic myself. Over the years I have followed the thinking and writing of many experts in this area. Countless numbers of power system calculation formulas, spreadsheets and computer programs have been written and much of the work goes back directly to Bob Boucher’s published work with brushed DC motors (Electric Motor Handbook). While there are many variables involved in trying to predict the performance of any given motor, The Big Three were Kv (rpm/v), Io (no load amps to account for the amp “loss”) and Rm (apparent motor resistance to account for the voltage “drop”). The ESC for a brushed motor system was handled, basically, as just another resistance loss in the total power system.
Brushless motors have brought many new variables into the process. With the commutation of a brushless motor being handled electronically by the ESC, the brushless ESC really needs to be considered a part of the motor.

Bob Boucher’s Electric Motor Handbook describes the methods to collect The Big Three and how to use that information to predict how a given motor will perform with a certain load (prop in many cases) and applied voltage (number of cells). Unfortunately, The Big Three are not all that good at predicting the resulting RPM and amp draw.

Computer motor modeling programs using formulas that rely on The Big Three for the prediction of brushless motor performance are inherently flawed.

1.) Io does change with the voltage and the timing.
BP Hobbies BP 3520-6 & Jeti Spin 44-amp ESC:
Average Io (24-degrees): 16.0v, 3.57 amps; 19.3v, 3.92 amps
Average Io (0-degrees): 16.3v, 2.94 amps; 20v, 3.48 amps
In the brushed model Io (no load amps) is subtracted from Iin (Amps in) to account for Hysteresis loss, rotational speed loss, friction loss, and incorrect timing loss. According to Bob Boucher, “For the purposes or calculating motor performance one can assume that there is a leakage current or loss current shunting the ideal motor by an amount equal to the measured no load current or Io. The net effective current and the torque it produces are decreased to the values: Inet = Iin – Io”.
Since some of these losses do not appear in a brushless design, and new losses, especially in the ESC, are introduced, Io does not appear to be a particularly good value to be used in a brushless motor modeling formula or computer modeling program. As I stated earlier, Io is more of a variable than a constant and if the motor timing of the brushless ESC is advanced from 0-degrees it becomes even more of a variable.
Here is some no load data from a recent motor test of mine.
Jeti Spin 44 0-degrees timing: 16.33v, 2.94 amps, 11808 RPM
Jeti Spin 44 24-degrees timing (Jeti outrunner default): 16.07v, 3.67 amps, 12360 RPM
Jeti Spin 44 0-degrees timing: 20.03v, 3.5 amps, 14520 RPM
Jeti Spin 44 24-degrees timing: 19.36v, 4.01 amps, 15000 RPM

2.) Rm cannot be relatively easily “measured” for a brushless motor/ESC combination.
Rm tries to account for a voltage drop due to the electrical resistance of the windings. The calculation of the voltage drop tries to create the Vnet (net volts). Vnet = Vin – (Iin * Rm).
Watts out = Vnet * Inet, but in a formula or computer model, this is true only if Vnet and Inet are accurately modeled. Using Io and Rm doesn’t produce a very accurate model for brushless motors and their ESC companions and, as previously noted, Kv is dependent on timing.

3.) Kv changes with the timing.
Bob Boucher, Chapter 2, Electric Motor Handbook, “For this measurement (Kv) you need to make sure that that your motor is adjusted for neutral timing.” Of course he was talking about a brushed motor, but it also applies to brushless motors as well.
Changing the motor timing changes everything.

It’s a Matter of Timing:
While collecting the motor/ESC/prop data for my latest plane/power system, I asked myself, “How is the timing affecting the recorded data?”
As usual, I am working on a new plane and power system setup. While checking out the power system, I had “accidentally” gathered some no load data with the timing set at 0-degrees. I then set the timing of the Jeti Spin 44 to Jeti Model’s recommended 24-degrees for outrunner type motors and gathered numbers that were different from the 0-degree timed data.
After running the battery/prop tests with the Jeti Spin 44 timing set at 24-degrees, I became curious as to what would happen if I set the timing to 0-degrees and repeated the battery prop tests. There were three factors that prompted me to do this.
First, I wanted to use a 5-cell Emoli battery in my latest project but found the 39 amp draw using an APC 10x7E with a True RC 5S1P 4000mAh Li-Po battery (doubling for the 5S1P Emoli pack I don’t have) troubling. I have read and seen graphs that indicate that the Milwaukee V28/Emoli cells really drop voltage quickly after passing through the low 30-amp range and are good only to about 40 amps.
Second, my data did NOT come out anywhere near the data on the BP Hobbies’ Web page for this motor. The BP Hobbies Web page shows, “APC 10x7 Sport, 19.2V, 35.6A, 684W, 12000 RPM”. I had entered my collected data for the 24-degree timing tests into the Drive Calculator computer program (FREE @ The Drive Calculator program then gave me back information that was very, very close to my measured data, so I was pretty sure it was working well. I then entered the 19.2V and the APC 10x7 Sport prop from the BP Hobbies site information, set the elevation to 21m (Piscataway, NJ elevation) and the temperature as 20-degrees C as the inputs for Drive Calculator. The program came up with “42.7 amps, 819.8 watts in, 12758 RPM”. That was too far off for my liking. I wondered why?
Third, I was just plain curious about the effects of timing!
I collected no load and loaded data with the ESC timing set to 0-degrees. I created a new motor in Drive Calculator using the 0-degree timing data. Once I had the new, 0-degree timing motor in Drive Calculator working well with my collected data, I used the BP Hobbies data noted above and Drive Calculator output, “37.4 amps, 718.5 watts in, 12277 RPM”.
The numbers for the 0-degree timing are not what I call extremely close to BP Hobbies’ published numbers, but they are a lot closer than when the Spin 44 ESC timing was set to 24-degrees. There are a lot of explanations for the differences between the Drive Calculator estimates and the published BP Hobbies’ numbers, but I believe that the main difference is that the folks at BP Hobbies may have used a cheap, less-efficient Chinese ESC, which had greater losses in the ESC and thus the lower measured numbers. BP Hobbies do not state what ESC was used to gather the numbers or what the timing was set to.
It can be seen that timing plays an important part with how the motor performs both in the real world and in computer simulations.
I collected the following data by charging a Skyshark 4S1P 4000mAh Li-Po pack and then running a motor/battery/prop test using the APC 10x7E with the ESC timing set to 24-degrees and then 0-degrees. Before running the test, I “warmed up” the motor, ESC and battery by running two 10-second full throttle runs. The 24-degree test data was gathered first because it would draw the most amps. The ESC was quickly changed to 0-degrees timing, using the Jeti Spin Box, and then the second set of data was gathered.
24-degrees: 13.75v, 25.51 amps, 9390 RPM, 351 Watts In
0-degrees: 14.16v, 24.04 amps, 9330 RPM, 340 Watts In
While there appears to be an insignificant difference between the 0-degree timing and 24-degree timing on the 4S pack, when a True RC 5S1P 4000mAh Li-Po battery was used, the following data was gathered.
24-degrees: 17.10v, 39.03 amps, 11340 RPM, 667 Watts In
0-degrees: 17.47v, 35.86 amps, 11130 RPM, 626 Watts In
Again the difference is not huge, but it does make a difference when I’m planning on using the Emoli cells. The Emoli cells will be much happier with the maximum amp draw near 36 rather than near 39. By using the 0-degree timing I am giving up ~200 RPM while reducing the maximum amp draw by about 3 amps.

Previously I made statements about how accurately the Drive Calculator computer program predicts the performance of the power system I am using when the data is entered properly. Here is the proof.
Motor: BP Hobbies BP 3520-6
Altitude: 286m
Ambient Temperature: 20-degrees C
Jeti Spin 44 ESC timing 24-degrees
Prop: APC 10x7E
Measured using Emeter: 13.5v, 24.25 amps, 9174 RPM, Watts In 327
Prop: APC 10x7E (not the one supplied with the program but one I had recalculated to match my actual prop)
Drive Calculator output: 13.5v, 24.8 amps, 9236 RPM, Watts In 334.8
Jeti Spin 44 ESC timing 0-degrees, props same as above
Measured using Emeter: 14.0v, 23.55 amps, 9264 RPM, Watts In 330
Drive Calculator output: 14.0v, 23.0 amps, 9276 RPM, Watts In 321.4
It should be remembered that the real world “motor” was modeled twice for this program. A set of data was collected with the timing set at 24-degrees. That data was saved as the BP 3520-6 ESC timing 24-degrees. Then a second set of data was collected with the ESC set to 0-degrees. That data was saved as BP 3520-6 ESC timing 0-degrees. The outputs above are taken from the “two” different motors (meaning the ESC timing was different), thus illustrating the difference timing makes on “power system” predicting.

According to Bob Boucher, advanced timing was used with brushed motors for “Sparkless Commutation”. Motor sparking doesn’t happen with a brushless motor, as there are no brushes. I have only been able to find vague references as to what timing to use with brushless outrunners and no explanation as to why.
Jeti Model Spin Box Instructions: “Motor timing (pre-ignition) –
Recommended values: 2pole motor...0-5°, 4p motor...0-10°, 6p motor..0-20°, 8p and
more...20-30° - necessary in case of the so called reversed motor conception”
Castle Creations Phoenix Line of Controllers:
9.5 Programming Setting 5 - Electronic timing advance
Option 1: High advance timing (120-350) Recommended for higher pole count motors (eg. Jeti or large Mega motors) Gives more power at the expense of efficiency
Option 2: Standard advance timing (50-200) * Recommended for most motors (Aveox, Hacker, Astro, smaller Mega, Kontronik) Gives a good balance of power and efficiency
Option 3: Low advance timing (00-150) Recommended for use when efficiency or run-time is primary concern - Gives a slight loss of power with a slight increase in efficiency.
NOTE: The controller senses the motor type by its inductance, and automatically sets the maximum advance according to motor type (eg: outrunner motors will automatically be run at a higher advance setting)
I guess I am still uncertain as to why the recommendation for outrunner brushless motors seems to be to set the timing at 20-degrees or more. I am looking for the answer as to why this is the recommendation? Also, what is “wrong” with running a brushless outrunner at 0-degrees timing for higher efficiency?
Last edited by Ken Myers; Nov 30, 2006 at 09:03 AM. Reason: Text added
Nov 30, 2006, 11:56 AM
Registered User
Nother very thorough build thread, Ken.

I like what you did with the elevator. Did you just cut a notch in it or did you split it completely and rejoin it with some type of joiner?
The stock tail wheel setup has got to be the most rediculous thing I've ever seen! Love the "hardwood" wedge that you're supposed to mount the tailwheel on .

The only thing I've done to mine is cut a hatch on the top of the fuse between the firewall and 2nd former. It's on the back burner for now.
Nov 30, 2006, 12:46 PM
jrb's Avatar
Another great read Ken!
Nov 30, 2006, 12:55 PM
Registered User
Ken Myers's Avatar
Originally Posted by StrangeGager
Did you just cut a notch in it or did you split it completely and rejoin it with some type of joiner?
I cut a slot for a 2" long dowel joiner at the center, epoxied the joiner in and then cut the "wedge" out for the rudder to pass through. Very, very easy.
Last edited by Ken Myers; Nov 30, 2006 at 03:19 PM. Reason: left out a word
Nov 30, 2006, 04:05 PM
Registered User
BEC's Avatar

Interesting the RPM and current discrepancies you mention. I have done a couple of flights with both a Jeti Spin controller and an EagleTree MicroPower data logger on board the airplane at the same time and saw similar current discrepancies. I didn't have an RPM sensor aboard so I couldn't cross check that. I will have to do so.

I'm surprised Mr. Tinka wasn't more forthcoming. It sounds like he expects the "commanded" RPM from the controller to match the actual - which is pretty reasonable. This angle bears some investigating.

That little "pi-like" symbol is a square wave and yes, that indicates the signal. Jeti aren't the only one to mark things that way. I've seen it on some receivers as well.

The current rating for a battery capacity is a round about way to define how long "sustained" is sustained for the ratings given.
Nov 30, 2006, 06:25 PM
Registered User
Ken Myers's Avatar
Originally Posted by BEC
I'm surprised Mr. Tinka wasn't more forthcoming. It sounds like he expects the "commanded" RPM from the controller to match the actual - which is pretty reasonable. This angle bears some investigating.
What surprised me was that he thought that 10% is "close enough."

Originally Posted by BEC
That little "pi-like" symbol is a square wave and yes, that indicates the signal. Jeti aren't the only one to mark things that way. I've seen it on some receivers as well.
I was pretty sure of that and I felt that impuls was impulse and to me that meant signal.

Originally Posted by BEC
The current rating for a battery capacity is a round about way to define how long "sustained" is sustained for the ratings given.
When I first had that question I had not flown the controller. 2000mAh/2200mAh seems to be the limit at the limit as the Spin 44 keeps shutting off (reaching 110+ degress) in that amount of time when using the 5S pack. I've had both sides Velcroed on the ESC so that the other side was exposed to the cooling air and that seems to have not made a difference. I am considering adding an air scoop near the ESC to make sure it gets plenty of air, but since I will mostlly be flying 2 flights on the Li-Po pack and one 6 minute of so flight on the Emoli pack when I get it, it shouldn't be a problem. I really only pointed it out for those that like to fly a long time.

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