- Editor's Corner -
by Cecil Collum
I hope everyone got an opportunity to fly at least once this month but with the bad
weather early on, once may be all we get.
The Kansas City RC Swap Meet is history once again. Hardy Jeffries had a table
at the meet and sold his 1/3 size Stearman among other items. Tom Minton also had
a table and sold most of the items he had purchased from Brad Otts. Both were
pleased with their sales at this one day event. Those attending included Bill Womble,
Giles Helbling, Don Jones, Terry Rollins, Bill Stranahan, Tom Minton, Hardie Jefferies,
Larry Scheer and your editor. I believe there were more planes at the meet this year
than last and one could get a very good buy. One member bought a 1/5 size Cub that was
originally priced at $250 but actually sold for $160 with an engine, receiver, battery and
all servos. Several others made good buys also, including a flying wing complete with
motor, servos and ESC for $25.00!
We left Fort Smith at 5:00 AM and drove through rain and fog for about 150 miles but arrived
just a bit after our planned time. The highways were clear even though the vegetation in
Missouri was encased in freezing fog. The return trip was uneventful and we arrived back in
Fort Smith about 6:30 PM. It was a very enjoyable experience and you missed a good show
if you didn't attend. The meet is held each January, about the third weekend.
The second part of "Volts and Amps for Dummies" is in this issue. I would like to remind
everyone that this article was run in an online magazine, modelflight.com, and published here with
their permission. I hope everyone got something out of Part 1 and that you will get even more
out of Part 2. Mr. Wheater explained electrics in a way that took the magic out of it for me.
Now maybe I can get an electric plane to actually fly! The more I am exposed to electrics, the
more I like their potential. I will still miss the engine sounds but not the mess on the plane
and, if I were to ever totally switch from wet fuel to electric, I would consider purchasing a
product that RAM markets to simulate engine sounds.
Please e-mail me at redleg142@hotmail.com and tell me if this sort of article helps you to
understand further the workings of our hobby. I want to publish what you want to read so please
help.
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... from the president's perspective
by Ron Roberts
February! Most likely, we will have another month of cold weather before things start looking
better for flying again. I don't know about you, but the older I get the more I dislike cold
weather! Someone once said, "We can always put on more clothes, but there is a limit to how much
we can take off". I suppose that is a true axiom, but I'm not sure it is a helpful one, because
even bundled up in long johns, sweat shirt and field jacket, I'm still too cold to be comfortable!
I remember once last year Walt Moore came to the field on a cold day and didn't even get his planes out of
the vehicle... He got out for a few minutes and then spent the rest of the time in his car with the heater
on. He and I are sincerely looking forward to spring.
Speaking of spring, it is not too early to announce that February is the last month for the monthly
club meetings to be held "inside". The March meeting, which will be on Sunday, the 14th of March,
will be held at the field.
I apologize for the "marathon" meeting we had last month. Those who attended know it lasted
for about two hours. We had a lot of things to discuss and decide upon, but we have them out of
the way now so future meetings shouldn't be anywhere near that long. I really appreciate the
comments from all and the discussions we had. We "tabled" a few items, but we accomplished
a great deal.
I would like to take this opportunity to thank Cecil Collum for the great job he is doing as the
newsletter editor!
We have 30 members who have paid their dues for 2010 as of this writing. I am happy to report
that some of those who have renewed their membership are members who have not flown in a few years and
are returning members. This is a good omen!
The new field committee has been in contact with the Fort Chaffee Reclamation Authority, again, in regard to
the possible acquiring of a new field location. I know it appears that this process is moving
about as fast as a snail through Jello, but we are advancing. We were able to report to the FCRA
that we have a firm commitment from a pulp plant to get the trees cut down and hauled off at no cost to us.
That will leave the "stumps" needing to be dealt with, which Larry Evans mentioned, the FCRA may be able
to help us with.
We also approached them (the FCRA) with the idea of deeding the land over to us at the outset instead of us
"leasing" the land for awhile and then the FCRA deeding it over to us, as Mr. Ivy Owen proposed. They were not over
joyous about that, but they did not rule it out either. There is hope! We should be
scheduling another "fact-to-face" meeting in February.
Please try to attend the February meeting, to be held Tuesday Evening, February 9th in the Razorback Room
of the Western Sizzlin' Restaurant on Towson Ave. at 6:30 PM.
Until next month .....
Ron
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The Magic of Electric Flying
or
"Volts and Amps for Dummies" (Part 2)
By John Wheater
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[Item j] Now there is a useful figure. You must have some idea what size prop you want!
[Item l] This is a reference to the ESC you should choose, always err on the large size.
If your motor is going to consume 45 amps, choose a 60 amp controller so it will not have to work at its capacity.
- What you NEED to know:
- Choose your ESC by taking the maximum current draw of the motor and going for the
next size up.
So, what sort of model is the Thumper 4250 capable of flying? We will assume it will draw a
steady 35 amps at 11.1v on its 12 x 6 prop.
Question: How many watts is it producing?
Answer as at e) in Part 1: 35 amps x 11.1v = 388.5 watts
As a general rule of thumb the power requirements of the four basic type of model are as follows:
- Powered Gliders 50 watts per pound
- General sport model around 75 watts per pound
- Mild aerobatic model 100 watts per pound
- EDF and 3D in excess of 150 watts per pound
That means that the Thumper 4250 will fly:
- A powered glider weighing 7.77 lbs, that’s a biggie!
- A general sport model (which includes scale types like the Piper Cub and Beaver) of around 5 lbs.
- A mild aerobatic model (or scale low winger like a Mustang) of up to 4 lbs, or
- A 3D model of 2.5 lbs.
THIS MOTOR IS NOT SUITABLE AT ALL FOR EDF, it simply does not turn fast enough!
3. Testing for power - Wattmeter
- What you NEED to know:
- How do we measure the current draw? That’s how many amps?
- Answer: We use a WATTMETER!
Wattmeters vary with the readings they give but even the most basic will provide at least the current
‘amps’ drawn and the voltage of the battery at that current. Better ones will also multiply the
two for you and give you the units of power that is ‘watts’. Generally about £30 from most model shops.
A wattmeter is installed in the electrical circuit for testing purposes only between the battery and the
ESC. With a propeller attached and following the instructions for the ESC gently fully open the throttle
and note the readings on the watt meter.
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The current drain will increase as you advance the throttle.
Repeat the experiment with a variety of propellers and note the difference they make to the current drain.
What you should aim for is the power to fly the aircraft as you intend, motors are more efficient at a lower
power than designed maximum and you will achieve a longer flight time.
Let’s look at chart from an actual test:
E-Flite 25 Motor Test Current
| Battery | Propeller | Volts | AMPS | Watts | RPM |
| 3S 1P | 11 x 8 | 11.1 | 31.0 |
344.10 | 7860 |
| 3300mAh | 11 x 10 | 10.4 | 36.3 |
377.52 | 7200 |
| 20-30C | 12 x 8 | 10.6 | 36.0 |
381.60 | 7200 |
| | 12 x 10 | 10.0 | 40.2 |
402.00 | 6680 |
While this isn’t the Thumper we have already discussed, it is a similar motor rated at 3.3 Ah (Amp/hours).
But we are drawing 31 amps at the minimum, how does that figure?
- What you NEED to know:
- All model Lipo batteries carry a figure which is the C (for charge) rating. It is, but wait a cotton
picking minute. What’s that 3300 Mah under the battery type? And what the heck is 20-30C?
OK, now is as good a time as any I suppose...
- What you NEED to know:
- All batteries carry a figure which states the amount of current they are able to deliver shown as Milliamp
(mA) Hours. A milliamp is 1/1000 of an amp so 3300 mAh in fact, the maximum current that the battery will
allow itself to be discharged at. Therefore a 20C 3300 mAh battery (3.3 Amps) can be discharged safely at 66
Amps.
- The second figure is the very maximum the battery can be discharged for in a short burst; 99 amps.
- The greater capacity the battery (in Amps) the longer will be your flight time, all other things being equal.
- And the RPM figure has sneaked in too but I will come back to that later. The difference in the RPM on
this test you will notice doesn’t alter dramatically.
So what’s the best prop for this motor for a sport model? Looks like an 11 x 10 or a 12 x 8 doesn’t it?
There is virtually no difference in the figures. A 12 x 10 is offering only 5% more power (watts) but at a
higher required current (Amps) so the flight time is likely to be slightly less.
Part Three will appear in the March issue... Stay tuned!
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Meeting Shorts:
These are not the actual "minutes" of the club meeting, as those were
taken by our Secretary, Mike Beck and are available in the "Members Only" section of the club's website.
These are "much shortened" notes taken by your editor and available for public viewing. |
President Roberts called the meeting to order at 6:35 PM with 24 members and 4 guests present in the Razorback Room
of the Towson Avenue Western Sizzlin' Restaurant.
The New Field Committee gave a report updating us on our search and their efforts to secure a field at Chaffee
Crossing. Everything looks very promising at this point but only time will tell. The committee plans
to schedule a meeting with the FCRA soon.
The Minutes and Treasurer”s reports were read and approved.
Everyone is encouraged to attend the meetings and voice their opinions about the business being discussed or bring
up new business. The club belongs to each of us and will only get better with the participation of all members.
Next Meeting:
Tuesday, February 9th, 2010
Time: 6:30 PM
Place: Western Sizzlin on Towson Avenue
Come join us!
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BUILDING KINKS AND HINTS
This column is devoted to Tips and Hints for building and repairing our birds, since they seem to come with an
unknown expiration date. Even those who fly only ARF's will need to make repairs from time to time (seems
like those times are extremely compressed for me)and since we have several skilled builders in the club, we will
use this to disseminate that information to all.
The first Tip is from Bill Womble who is repairing his Hangar-9 P-51D: Bill needed to repair a few cracks
in the balsa skins of his plane's wing near the root rib so he removed the flap servo, re-aligned the pieces of
balsa and reinforced the area by laying a piece of fiberglass drywall tape adhesive side to the balsa over the
cracked area and drizzling CA onto the balsa and tape. This made a quick, effective repair.
The second tip is from an anonymous source: If you need an air scoop, use a portion of a plastic spoon.
Glue it to the wing or fuselage, fair it in and paint it to match the structure. Looks great!
When repairing coroplast airplanes, it is essential that all oils are removed from the surfaces to be glued.
One method is similar to that used in repairing balsa planes -- wipe down the surfaces with a degreaser, then wipe
again with alcohol. This will remove 99% of the oils and glue will adhere to the surfaces. The best glue
to use is a contact cement such as 3M's Super 77.
The best way I am aware of to prevent your landing gear wheels from falling off the axles is to thread the axle
and fix the wheel with an aircraft nut. It will not fall off!
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UPCOMING EVENTS
The following events have been scheduled by the Flightmasters or other organizations. Mark your calendars so
you don't miss any of them. If you learn of others, please e-mail the editor at redleg142@hotmail.com for
inclusion in our list.
2010 Event Schedule
DATE | EVENT |
LOCATION | SPONSOR |
March 6th |
El Dorado Swap Meet* |
El Dorado, AR
|
Model Aviators/So AR
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April 17th |
Spring Picnic & Fun Fly |
Club Field |
Flightmasters MAC |
May
15 - 16 |
Petit Jean Fly-In |
Petit Jean Airport |
MARCS |
May
29 - 31 |
C. Venable Jumbo Fly-In |
Club Field |
Flightmasters MAC |
June
24 - 27 |
"Mega" Huckfest |
Sallisaw Airport |
OKC Club w/FMAC |
September 3 - 5 |
K. Roberds Mem Fly-In |
Club Field |
Flightmasters MAC |
October
23 & 24 |
Last Bash Fun-Fly |
Club Field |
Flightmasters MAC |
* For more information or directions, e-mail jcunningham50@hotmail.com or call 870-814-6005.
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2010 Officers:
President: Ron Roberts
Vice-President: Harold Wille
Secretary: Mike Beck
Treasurer: Bill Womble
Past President: Josh Price
Club Safety Officer: Bill Womble
Newsletter Editor: Cecil Collum
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