RC Electrics
Any contemporary aeromodeling magazine should be enough to convince even the most doubtful that E-power is now, that it is up and getting happier, and that it is here, as ever. Moving past the popular aeromodeling magazines, there are three dedicated E-power ones, and I don't think any other specialty within aeromodeling can say that!
Basically, those who may have early on viewed Electrics as fad that would soon go away got it all wrong! One convincing indicator is that E-power has grown so popular and so diverse that there are numerous separate specialties within Electric. And I'm told of one industry insider who feels that Electric is now the fastest-growing area within the overall hobby—and money talks, right? So, naysayers, be gone for good!
With E-power attracting newcomers at an increasing rate, there is an increasing need for the most basic information. I see it all the time at meets, on my own flightline, and in reader mail. Basics and basic questions have not changed with time! There are just more people in need now. Following are a few fundamentals for the newest participants.
Classically, the power source for electric flight motors has been the nickel-cadmium (Ni-Cd) rechargeable battery—the Electric fuel tank. Recent years have seen some inroads being made by the rechargeable Nickel Metal Hydride (NiMH) packs. One is not categorically better than the other; both have their place at this time, and both have some basics in common, as follows.
A cell is the smallest individual unit (individual voltage source), and a series is an interconnection of two or more cells. The range of usage is broad. I know a serious modeler who competitively flies single-cell powered Free Flight and another with a 72-cell Radio Control (RC) power system.
Virtually all batteries we use have their cells connected in series, but cells connected in parallel are also called a battery. These connections are shown in a accompanying sketch.
Cells wired in series result in a battery which has a terminal voltage equaling the number of cells multiplied by the cell voltage. If a cell has a voltage of 1.25 volts, a battery of four series-connected cells has a total (terminal) voltage of 4 x 1.25 = 5 volts. Simply put, the voltage of cells in series adds up.
Series-connected cells must be of the same type. This means that they are of the same chemistry (all Ni-Cd or all NiMH) and of the same capacity (i.e., the same milliampere-hour rating). Any current flowing through one cell flows through all cells. This is true for charging or discharging current. Ideally, all the series-connected cells of a battery charge up together and run down together. The total voltage varies with cell count, but the capacity (milliampere-hours) of the battery remains equal to that of a single cell.
Though rare, one may occasionally find reference to cells connected in parallel. The resulting battery has a terminal voltage equal to that of a single cell, the capacity equal to the sum of all the cells. It is generally considered okay to discharge but not okay to charge cells wired in parallel. The rationale is as follows.
Discharging parallel-connected cells is considered okay because all cells are constrained to an identical terminal voltage during discharge. During charging, however, it is felt that the inflowing current will likely not divide equally or in any other predictable way among the individual cells. It's this unknown plus concern about possible associated ill effects that make charging cells in parallel a no-no (Charging is done by electrically breaking up the battery, charging, then reconnecting all.)
The basic concepts of series- and parallel-connected cells are extended to that of series- and parallel-connected batteries (packs). Consider a commonplace six-cell pack. One could series-connect six or two identical packs and have a 12-cell battery. This battery can be charged and discharged as though it was a single group of 12 cells because (electrically) it now is.
At this point, one could not tell by examining the terminal behavior of this new pack exactly what its makeup is. Is it 12 individual cells? Is it two six-packs? Is it four three-packs? Is it three four-packs? The originating makeup of this "new" pack does not matter as long as all the cells are of the same type, as explained in the preceding.
Similarly, one can readily tell from terminal behavior what exactly is inside a pack of parallel-connected cells or even parallel-connected packs. Is it two one-ampere-hour cells or four half-ampere-hour cells? Or is it two one-ampere-hour packs or four half-ampere-hour six packs? Discharge measurements would all yield the same milliampere-hour capacity. (Note that paralleled batteries must have the same cell count.)
While all this is offered to aid a beginner's understanding, I do know of one modeler who is a recognized leader in the All Up/Last Down fun event. He has very effectively used in-flight switching of cell groups to manage series and parallel combinations "on the fly." This, in conjunction with carefully selected motors, props, and the airplane itself, has made him a consistent winner!
This ends this midsummer column. Please enclose a self-addressed, stamped envelope with any correspondence for which you'd like a reply. By the time you read this, it will be only days away from daylight hours getting shorter. Now is the time to maximize your E-flying fun!
Happy E-landing all! RA
Don't use stand screws on any of this model's control surfaces. The instructions suggest using "good quality ball bearing servos with output torque of 65 inch-ounces or more for this model." Since I'm using a JR PCM10 radio, I installed some of the new JR digital DS9411 Ultra Torque servos; they are included on the rudder, elevators, and ailerons. I installed a standard servo for the throttle.
The DS9411 servos have 62 ounce-inches of torque with all-port gears, and they weigh slightly more than 1.5 ounces. JR has two other servos in this lineup: the DS3421 mini servo with 65 ounce-inches and the DS668 micro servo with 35 ounce-inches of torque. Only the DS668 has a coreless motor, the others are coreless. All have the metal-alloy gears and are compact, light, and powerful.
Join the wing halves with plenty of 30-minute epoxy. It's very important to coat not only the inside of the slot on the wing halves, but to coat the brace. Set the side, and let it dry.
Strip back approximately 1 1/2 inches of the UltraCote®, and add a strip of fiberglass cloth around the wing center section. I used Paper Z-Poxy thinned with rubbing alcohol off the pharmacy's shelf. This makes the Z-Poxy go on fast, and it fills the fiberglass evenly. The Z-Poxy doesn't have a strong odor as some epoxies do. The UltraCote® that matches the CAP's color scheme is Dark Yellow (item number 889).
After re-covering the center section, fit the wing to the fuselage. Mine fit perfectly with no adjustments needed.
More about the CAP 231 and the PT-19 next time.
Scale Search:
I'll call this section this because the name covers those of us who are looking for documentation, plans, or some unique piece of equipment that's just plain hard to find. Send an E-mail with a title to me, then it will take roughly three months for an answer.
You can also send the information to the National Association of Scale Aeromodellers' (NASA) Web editor Ed Claryman and have it included on the NASA "FBO" (Find Base Operation) Web site. This will be quicker, and increase your chances of obtaining more responses. That Web address is www.nasascale.homestead.com.
A fellow modeler is searching for a set of plans drawn by Pat Massey of Pampa, Texas. Pat has passed away, and Jim McCoy would like to find plans for a Seabee re-creation KCA. Anyone who has any information please contact Jim McCoy at The McCoy Group, 1 Wyeth Circle, Milford MA 01757.
This year's Scale National Championships will be held July 7-9, which is a change from the previous announcement. The dates had to be adjusted because of some safety and administrative considerations.
It should be a great event with plenty of activities for everyone. There will be Fun Scale Nats and Open, Sportsman, Classic, Expert, Designer, Team, and F4C on the RC side. There will also be an official Free Flight Scale event hosted by Dave Platt. After static judging at the Horizon Convention Center on Sunday, we will take part in the indoor RC events to be held at training area.
For more information, contact the AMA Competition Department at (765) 677-1256.
I received a flyer for a contest in Michigan that the Radio Control Club of Detroit will be hosting. The 11th Annual Great Lakes Contest will be held August 4 this year. This is a Fun Scale event; documentation isn't necessary, and ARFs are allowed per AMA rules. This contest is laid-back, and it's a good entry-level contest.
Bob Chapman is the contest director; you can contact him at (248) 524-0092 for more information.
It looks like I've run out of room this month. Fair skies and tailwinds. RA
Transcribed from original scans by AI. Minor OCR errors may remain.
