The Skymaster's Electric Fun Fly is scheduled for Sunday, June 28. It will be held at their Scripps Road Field. Scripps Road is between Joslyn and M-24 in Lake Orion, MI. The start time is 10:00 AM.

     This event is a full day of flying. There will be Electric Power open flying from 10 a.m. until 8 p.m. Pilot prizes are provided for participants.

Additional Event Information

Event Flyer

Event Website

Map

Contact CD Pete Foss
Email Pete

     Dates given for the flying season EFO flying meetings are tentative. The date depends on the weather and may change from the one noted in the monthly Ampeer. The EFO Web site has the most current information posted. Also, emails are sent to EFO members if a date change is required.

     The Capital Area Radio Drone Society (CARDS) Electric Meet is Saturday, August 22, 2015

     There field is located at 8328 Otto Rd., Grand Ledge, MI. Time is from 9 a.m. to 9 p.m. The Landing Fee is $15, which includes pizza & a soda. The field is available to registered pilots for electric only open flying on Friday Aug 21st from 4-9:00 p.m., Pilot pre-registration and Spectators are welcome.

Pilot and airplane requirements:
Current AMA or MAAC card required
Open to All RC Electric planes and helicopters

Site Accomodations:
1000 ft E/W runway
Basic restroom facilities

Contest Director: Marv Thomson

     The first part of this article appeared in the June, 2015 Ampeer.

     The article had reached the point of selecting the specific motor for my new Sig Four-Star Forty.

     I stated that I reached the conclusion that there were five Cobra outrunner motors that would be appropriate for consideration for this project when using an APC 12x8E prop and 4S LiPo. A table of appropriate motors was shown in the June issue. Note that all five motors have approximately the same watts out (about 500).

     How that table was created is explained in this issue.

     The C-3520/12 is the least efficient and has the highest percent of voltage drop. At 689.7 watts in it has the highest watts in per gram of motor weight at 3.19 watts in per gram of motor weight. While it would work, it would 'waste' the most energy, run the hottest and just generally not be a good choice, except where weight might be a critical.

     The C-4130/14 and C-4130/12 are the most efficient and have the the lowest percent of voltage drop. At about 600 watts in each, they have the lowest watts in per gram of motor weight at 1.5 watts in per gram of motor weight. They weigh significantly more than the other three motors. They might be useful in aircraft with an extremely short nose moment and or a very long tail moment where their weight doesn't adversely affect the wing loading.

     The C-3525/10 and C-4120/14 could be good choices for most applications. There is only a 40 gram, 1.41 oz., difference in weight between the two motors. The prop adapter and cross mount for the C-4120/14 is slightly heavier. There is not enough difference in current draw, resulting RPM and price ($5) to be of any real significance. It is pretty much a toss up. It comes down to achieving the proper CG without having to add weight to the nose or tail of the aircraft.

     Both motors require the same 4S 3300mAh 20C LiPo pack, for approximately 7 minutes of flight time, and an ESC with a rating of 60 amps or higher.

     Generically, the two most useful Cobra motors are the 4351-780, 253g and a 5052-710, 293g.

     That information can be used to find similar motors that 'should' provide similar performance.

     The Hobby King Motor Finder can be used to find similar outrunner motors, weight and K_v, sold by Hobby King.

     The sliders on the Motor Finder page need to be set to about 5% either way of both the weight and what they note as Kv.

     The Cobra C-3525/10 generically is a 4351-820, 253g
Kv range 820*0.95 =779 to 820*(1/0.95) = 863
Weight range 253g*0.95=240g to 253g*(1/0.95)=266g

     The sliders on the Hobby King Motor Finder Web page need to be used from both ends to adjust the range for both the Kv and weight.

     The search yielded only one motor that was somewhat equivalent to the Cobra C-3525/10. It was the Turnigy 4258 Brushless Motor 800kv.

     Generically the Turnigy motor is a 4251-800Kv, 266g compared to the Cobra C-3525/10, which is a 4351-820, 253g.

     This particular Turnigy motor has an 'odd' mounting for the motor, as far as I am concerned. No amp draw was noted on the motor's Web page.

     The Cobra C-4120/14 generically is a 5052-710Kv, 293g.

     The Kv range for searching, using the Hobby King Motor Finder, is 675 to 747 and the weight range is 278g to 308g.

     The search yielded only one motor similar to the Cobra C-4120/14. It is the Turnigy L5055C-700 Brushless Outrunner 700kv.

     The Turnigy is generically a 5055-700Kv, 296g and the Cobra a 5052-710Kv, 293g.

     Using other sites like, hobbypartz.com, headuphobby.com, towerhobbies.com, horizonhobby.com, etc., is much more difficult.

     First, the chosen site needs to be searched for a similar K_v number. That usually requires several searches to locate a similar K_v. Next the weight needs to be verified.

     A search of the Tower Hobbies Web site yielded: Great Planes Rimfire .46 42-60-800 Outrunner Brushless, 4260-800Kv, 268g.

     The Great Planes motor is a 4260-800Kv, 268g and the equivalent Cobra C-3525/10 which is generically a 4351-820, 253g.

     A spreadsheet has been created to do the math for you to use as an aid in searching for an outrunner motor. It is located here. It is an Excel formatted spreadsheet workbook. All of the entries, and there are VERY FEW, are made into the green cells only and all of the results appear in red cells.

     There are several spreadsheets in the workbook demonstrating various examples.

     The spreadsheet named "SIG 4-Star 40" is used for this example.

     The Target Motor & Prop Results appear just to the right of the Aircraft Input Data.

     The results show that the motor needs to handle 600 or more (+) watts in and weigh between 200 grams and 400 grams. A watts in range is also noted. It also shows the pitch to diameter and diameter to pitch ratios.

     A table of Cobra motor weights, to the right of the Target Motor & Prop Results, suggests which series of motors to look at on the Innovative Designs Web site for Cobra Airplane Motors.

     The table indicates that the C-3520, C-3525, C-4120 and C-4130 series contain motors in the desired weight range.

     Start the search for the 600+ watts in motor using an APC 12x8E prop by selecting the highest K_v motor of the series. Open the Propeller Data Chart. Check to see if it lists an APC 12x8E at about 600 or so watts in. Note the watts in range on the spreadsheet.

     The C-3520/10 doesn't have an appropriate match. It lists a 12x8E at about 480 watts in using a 3S LiPo.

     The C-3520/12 Propeller Data Chart lists the 12x8E prop at 689.7 watts in using a 4S LiPo.

     The watts in may seem high, but it is worth adding to the Motor Input Data of the spreadsheet. Yes, your judgement has to be used about how much more, or possibly less, power in is acceptable.

     When a suitable motor is found, using the data from the Propeller Data Chart, enter its name, weight, Kv and Io starting at cell A12.

     The same procedure is used for the remaining appropriate series motors. A total of five motors were found.

     The Motor Results area of the spreadsheet compares the approximated motors' watts out, system efficiency, voltage efficiency, suggested minimum ESC amp rating, number of LiPo cells, suggested safe battery mAh for the desired flight time, the safe minimum C-rate for the LiPo battery, the similar motor K_v range and similar motor weight range.

     A screen capture, on the following page, shows the complete Excel spreadsheet named "SIG 4-Star 40".

     The Motor Results also demonstrate that the C-3525/10 and C-4120/14 provide almost identical power to the APC 12x8E propeller. Either motor would 'fly' the plane in a similar, and probably indistinguishable, manner.

     The plane would not 'know' that the C-3525/10 is working much harder compared to the 'loafing' C-4120/14, and it wouldn't care.

     The spreadsheet screen capture shows that the system and voltage efficiencies are just too low to consider the C-3520/12, when compared to the other motors.

     The suggested battery mAh for the C-3525/10 to fly for approximately 6.5 minutes using 80% of its capacity while turning an APC 12x8E prop is a 4S 3042, which can be rounded to 3000mAh.

     For the C-4120/14 turning the same prop for the same amount of time, the suggested mAh is 2881. A 4S 2800 mAh 20C, or better, would be appropriate.

     Rounding the suggested battery mAh down, might result in slightly less flight time than the target flight time, while rounding up might result in a slightly longer flight time than the target flight time.

     To select a similar motor for the selected Cobra motors, the Motor Results show the Kv range and motor weight range for motors that might be somewhat similar.

     LiPo batteries make the selection process a bit simpler, in some ways, and a bit more difficult, in other ways.

     A123 Systems 2300mAh or the newer 2500mAh cells are 'best' used to provide about 100 watts in per cell. That means an amp draw of about 35. Using A123 cells requires selecting a Watts in per pound to equal a Target Power in (Pin) in even hundreds.

     The spreadsheet allows for this and can compute a weight range and K_v range for a suggested motor using A123 cells.

     Select a Cobra, or other brand of motor, in the suggested weight range and K_v range.

     For the example plane, a check of the Cobra Airplane motors on the Innov8tive Designs Web site showed no 4130-series motors with a K_v between 602 rpm/volt and 731 rpm/volt.

     The Cobra C-4120/16, Cobra C-3525/12, and Cobra C-3520/14 all fall within the K_v and weight range.

     Actually, the Cobra C-3525/12 was chosen for my Sig Four-Star Forty. A full review of the plane and power system will appear in an upcoming Ampeer. For now, just know that the plane flies great on my 6S A123 2300mAh pack, this motor and an APC 12x8E thin electric prop.

     This process works very well except for the The Gordian Knot of APC Propellors, which will also be discussed in an upcoming issue of the Ampeer.

     Saturday, June 6, Keith Shaw's actual birthday, turned out to be a PERFECT flying day for this 15th annual event.

     The attendance was good, the planes and camaraderie were great.

Carolynn Foss visits with Keith

     We were all thrilled that Keith was able to attend. He'd been 'under the weather' since April and was still having problems with light sensitivity. Although he could not fly, we were more than pleased that he was able to spend the whole day with us.

     Planes were constantly in the air from about 9:00 a.m. to after 4:30 p.m. What a day!

     There were folks from all over attending, and there was a really good contingent of us from southeastern Michigan.

     There are some excellent photos taken at the event by Patric Layman. They appear in this thread on RC Groups.

     Patric shares a lot more great photos, like the one above of his, on the RC Groups thread.

     That is NOT a staged photo. It is Jim Young's Wedell-Williams and Denny Sumner's Gee Bee on a fly-by. Great shot Patric!

     Unfortunately, Sunday was less than a perfect weather day. The wind howled and rain was imminent when we packed up our canopy and left about 10 a.m. Sunday morning.

     It was still a great time and we will be back next year!

     On April 28, 2015, Denny Sumner's Aircoupe had its maiden flight at the Midwest RC Society flying field.

     It was built from a short kit, and mostly redesigned along the way.

     The maiden flight was very successful! The photo was actually taken during the maiden.

     Full information and more photos appear in Denny's build thread on RC Groups.

     This in not a hanger queen! It is flown on a regular rotation with his other great planes.

     Great job Denny!

     Mark Rittinger brought his very unique Lower-Minges LM1 out to the Midwest RC Society flying field for its maiden flight on April 20, 2015. Keith Shaw was on hand to help with the maiden.

     Unfortunately this plane did have some 'teething problems', but it did fly!

     Mark has the 'bugs' worked out now, and it is flying.

     Mark's build thread on RC Groups has a lot more information on this plane very, very different aircraft.

Mark's hand disappears into the guts of the beast!

     2 Brothers Hobby, LLC has an interesting article on materials used in RC modeling.

     The article covers materials and their uses. The article includes notes about woods (balsa, spruce, plywood & basswood), carbon fiber (all its shapes) and foams, including EPS, XPS, EPP, POE/EPO and other foams.

     I thought it was worth sharing.

     By the way, their aircraft reviews are first rate!

Hi Ken,

     Thanks for sending me the info on how to access the previous Ampeers.

     I have had a ball looking through the back numbers, believe me. I seem to remember being aware of this possibility but not having too much luck.

     Anyway, I thought that you would find the attached copy of an advert from MAN of January, 1962 of interest if you had not seen it before. If your print-out of the ad is hard to read, I can send you a decent copy by Mail, let me know, OK?

Thanks again, regards,
Cedric Longman of St. Marys, Ontario.

     Chris Hass captured this low, high speed pass of his dad's KeeCat at the Radio Control Club of Detroit Field.

     Joe converted this ARF from glow to electric. Joe worked with Ken Myers of the AMPEER Newsletter to determine the power system.

     The aircraft is powered by an AXI 4120/14 brushless motor driving an APC 11X9 pattern prop. A Jeti 90 amp Electronic Speed Control controls the energy from a 5 cell 5000MAH Thunder Power 65C Li Po pack. Peak power is 915 watts at 10,600 RPM.

     The aircraft radio system is powered by a 5 cell 2000 NiMH pack. A Tactic TX850 transmitter works with a Tactic TR825 receiver and Tactic servos on the flight surfaces. Using the programming in the transmitter the landing gear retracts in sequence and the twin rudders are used as air brakes.

Some more info from Joe on the KeeCat

     It flew and flew well. Just a couple of clicks of down needed.

     Looks good with the gear up. Looked great in the air. Rolled really fast. Needs rudder in turns.

     Air brakes worked. Caused a pitch up as expected, so I have programmed in some down elevator.

     5 minute flights.

     Had to readjust the retract mechanism on the mains to lock properly.

     Looks like all the math was correct.

     Don't remember if I mentioned it but I paid $40.00 for the ARF including retracts.

     Thanks for your help. It was a great lesson on how to figure out a power system without any math. Your number confirmed my guesstimate.

Hi Ken,

     Would you consider changing the format of the HTML version from the extremely narrow display to something that doesn't force a fixed width? It makes it uncomfortable to read in this format. See attached image. It's much easier to read something that scales with the width of the browser window (you know, the reason people buy wide-format monitors).

Thanks.
Andy

     I will definitely look into it. I want to do something that will work on phones and tablets. KM

     The 2015 Flyer

     Map to the Field & Motel List