WHAT IS FSA | FOR EDF LOVERS

By Ed Waldrep

FSA (Fan Swept Area) is the area of the opening where the air goes through the fan. In other words, find the area of the entire face of the fan, the subract the area of the motor/spinner/hub, the result is the FSA.

Here's an example

WeMoTec Mini fan 480
Fan Shroud ID 2.715"
Motor tube OD 1.27"
Max Area 5.79 sq. in.
Motor tube area 1.27 sq. in.
Fan swept area 4.52 sq. in[U].
Tailcone diam. 100% 2.4"
Tailcone diam. 95% 2.28"
Tailcone diam. 90% 2.16"

The inlets may look quite small but if you measure and calculate the area you may find plenty of area. 100% of the FSA is the goal, a bit under you'll be ok, a bit larger is OK. You can go way above that and possibly improve static thrust, but too large and the scale looks begin to suffer (look at the huge nacelles on the GWS Me 262 and you'll see what I mean, they're way oversized) and there's increased drag at higher speeds because too much air is going in.

For exhaust aim for about 85 to 90 percent of the FSA.

Another thing to consider is the fan location. For most fighter type edfs, with the battery in the nose under a hatch, the fan needs to be placed with it's face toward the trailing edge of the wing. A fan access hatch on the bottom of the airplane usually looks better than one on the top.

Also, the battery mounting area up front should be made as long as possible to allow room for different sizes, lengths, and weights of batteries to be used. Some users will want to upgrade the power and making a small opening for only one size of battery that can't be moved makes upgrading difficult, a heavier battery would cause problems with balance.

Another factor is inlet ducting....it should be kept far apart until mid wing, then it should come together to meet at the fan. The reasoning is this will allow room between the ducting for a battery to slide farther back to achieve proper balance. A stock size battery may not need to go back that far, but with a power upgrade a heavier battery may be needed. However, you still need to make room for retracts on the outside, so there must be some room between the outside of the fuselage and the ducting, so back from the inlets in the front the ducting can head toward the center of the airplane but not at a really sharp angle, then once you get past the rearmost end of a battery the ducting can make another turn toward the center of the airplane and join in front of the fan. Avoiding sharp turns is important, make gradual turns if possible. With molded foam this is easily achievable.

TRANSFER PLANS TO FOAM

Transfering Plans to Foam ~ Sent in by Gene Cook

Fabric stores sell a spray that is used to temporarily bond patterns to fabric.  The spray works very well to hold plans onto foam and the plans can then be easily peeled off after the part has been cut out.  I also use the spray to temporarily bond two layers of foam together if I need two copies of the same part.  Using a carpet knife to cut through both layers of foam will then produce two parts that are identical that are easily separated.  The spray will lose its stickiness over time and does not interfere with other adhesives used to put the model together.

TORQUE ROLL RULE

Prop Rule of Thumb to Minimize Torque Roll Tendencies

Whenever you are building a pusher prop, jet type plane, to minimize the effects of torque roll, always keep the prop diameter 1/3 (33%) of the wingspan or less. With a 28" wingspan, a 9" prop is 32% of the wingspan and would be a good choice. A 12" prop is 43% of the wingspan and will generate a large amount of torque roll.

On the larger models, if you can keep the prop down to 25% of the wingspan, there will be almost no discernable torque roll tendancies. My 166% F-18 has a 48" wingspan, and I am running an APC 11x8.5 prop on it. In this case, the prop diameter is 23% of the wingspan, and it has almost no torque roll coupling.

Lucien

MOTOR EFFICIENCY

Calculating Efficiency of Electric Motors

(Example Motor)

Volts = 14.2
Amps = 28.0
Io = 1.1A (no-load amps at the operating speed)
Rm = 0.055 Ohm (internal resistance of motor)

Input Watt = V x A = 14.2 x 28 = 397.6 Watt

Copper Loss = Amps ² x Rm = 28 x 28 x 0.055 = 43.12 Watt

No-load Losses = Volts x Io = 14 x 1.1 = 15.62 Watt

Total Losses = 43.12 + 15.62 = 58.74 Watt

Output Watt = Input Watt – Total Losses = 397.6 – 58.74 = 338.86 Watt

Efficiency = Output Watt / Input Watt = 338.86 / 397.6 x 100 = 85.23%

Please note that we calculated the efficiency of the motor with a given prop. After calculating the efficiencies with a few different sized props (on the same motor), it will be evident how copper loss is mainly responsible for heat buildup and consequently lower efficiencies

INSTALLING MAGNETS

Installing Magnets:(In Foam)

Locate and glue in all the single magnets flush on the fuse bottom. Cut small squares of saran wrap and place on top of them for a glue barrier. Now place the matching magnets on the ones you glued into the fuse with the saran wrap trapped between them.

Carefully place the fuse on the wing and make sure it is perfectly lined up. Apply pressure to the fuse at all magnet locations to make an indentation of the magnet into the wing. Remove fuse, dig out all the indented places so that the magnets will fit flush. Fill the dug out places with glue ( I always use epoxy for this) and refit the fuse to the wing. Weigh down or tape securely until the glue cures. After the glue has set, pull the fuse off, remove the saran wrap squares and you have the magnets all glued in and perfectly aligned and never a problem with aligning the correct polarity.

JMorgan

MOTOR GUIDE

MOTOR BASICS

R/C Electric Motors For EDF and Pusher-Prop Parkjets

If you have any Motor Information or if you would like to see a specific manufacturer's motor information listed here, please CONTACT PARKJETS.

Axi: The first two digits of the number are the stator diameter in mm: the second two, its length. The full designation of the motor includes the number of turns of the winding, found after a slash. For example, the 2212/34 has a 22mm diameter stator that is 12mm long, and it has 34 turns of wire.

Mega motors: Similar designations - Mega 22/30/3 has a 22 mm-diameter case x 30-mm-long rotor, and a three-turn stator.

Aveox: An Aveox 27/13/3 seems to use the following: 27-mm diameter of the outside of the motor (not the rotor!) and 13 mm is the length of the rotor while three is the number of turns of the stator.

Hacker: A Hacker B20-26S is 20 mm in diameter, with the “S” indicating short length (L is for long) and is a 26-turn stator.

KV ratings: Kv gives the rpms produced by a motor per volt applied, i.e . if the motor has a Kv of 2000 and you run it on 6V it will turn at 12000 rpm.

Number of Turns: Turns are much like gearing! The higher the number of turns, the larger the propeller you can swing, however, the lower the maximum current it can withstand. Brushless motors that come in 1-, 2-, 3-, 4-, and 5-turn varieties are usually the internal-rotor type (but not always like the Hacker!). Brushless motors with high numbers of turns (say 10-30) are usually the external rotor (outrunner as we call it) type like AXI, Nippy, PJS, and the new little Hacker Baby.

GEARING: Gearing allows our motors to turn high rpm at low amps while swinging efficient propellers. For example an Aveox 1406/3 speed 600 size motor on 7 cells will turn an 8 x 4 prop at 13,000 rpm for a prop speed of 50 MPH while drawing 28 Amps. If you use a 3:1 ratio gear box with an 11 x 11 prop the rpm goes down to 5,100 while the prop speed goes up to 53 MPH and the current goes way down to only 15 Amps. The end result is a cooler running, more efficient motor and almost double the flight times. The drawbacks to gearing are that the gear box can block cooling air to the motor, add to the weight of the plane, and add to the length and sometimes circumference of the motor. The motor also has to be retimed to run in the opposite direction from the prop. If the plane has a narrow nose it will probably need a planetary in-line gear box. These gear boxes have little or no prop shaft offset, allow the motor to turn in the same direction as the propeller and are usually more expensive than standard gear boxes. Belt drives allow the motor and propeller to turn in the same direction, but can be large and heavy

Inrunner vs. Outrunner?

Inrunners are "standard" style motors. Meaning the can is stationary and the shaft spins inside.

The latest type of brushless motor available is the so-called "outrunner" like the Model Motors AXI types. At first sight these are rather odd. They are arranged the same way as a brushed motor with the coils in the center and the magnets on the can.

But...it is the CAN which rotates NOT the center armature. This means they are a bit tricky to mount since you obviously can't just clamp them down but it does have one BIG advantage. These motors generate much more torque than a conventional arrangement. In practise what this means is that they will turn a much larger and more efficient propeller without needing a gearbox. Gearboxes of course add complexity, cost and weight so that's a real advantage.

Other Resources:

www.flyingmodels.org

Has produced a HUGE Database of Electric Motor info
The Great Electric Motor Test #5
Featuring: Hacker, Jeti Phasor, Krontronik, Mega, Model Motors (AXI), 
MP Jet, Uberall Nippy, PJS, Plettenberg, and Typhoon Motors
The entire Motor Test Results have been compiled in a 108 page PDF
available for downloading here

GETTING STARTED

R/C flying is a really great hobby.

It's not as popular as some of the other forms of the R/C Hobby, however.  But since you are here reading this, I'll assume that you want to fly Jets, R/C Parkjets to be specific.

READ THESE FIRST:

 R/C Dictionary 

Read Tower Hobbies R/C Dictionary to become acquainted with General R/C Terminology

A really good Tutorial for Electric R/C flying

R/C Groups Electric Flight FAQ

First, let’s take a look at you, and your experience. Do you feel that you are physically capable of grabbing a jet that is anywhere from 2-Ft. to 5-Ft. long and weighing several pounds, and giving that jet a mighty toss, like Brett Farve throwing a bullet pass for the winning touchdown, and then having enough wit's about you to grab the TX control sticks, and fly that jet out of what ever problem it has gotten itself into?

I hope you answered "Hell Yes!!" If not, then you may want to consider flying a more "Conventional" Airplane," one of those slow flying type's with the prop up front, and leave the ParkJets for when your older, and/or when you have more experience.

Things You Need to Do

You need to start reading all about the Electric R/C Hobby at the RC Groups E-Zone discussion boards. I HIGHLY Suggest you join the RC Group's and participate in the thread discussions.  The owners of the ParkJet plans found on this website deeply appreciate knowing there plans are being built, and they will gladly answer any questions you have about the construction, and flying of their creations.  Everything I know, I have learned from the great people at the E-zone :)

BECOME AN AMA MEMBER

I've been an AMA Member for the last few years now, and I consider this organization to be essential to the R/C Flying Hobby. No matter WHERE or WHAT you fly. You WILL need an AMA card to fly at any sanctioned event, and the accident insurance they offer can really save you a ton of money, if you ever hurt someone, or damage any property while flying.  See more information on my Sensible Safety Rules webpage.

Your First RTF ParkJet

Your first ParkJet should be a Ready To Fly (RTF) 3 Channel (motor, aileron, elevator OR motor, elevator, rudder) kit, with , a pre-built jet with a transmitter (TX) receiver (RX), servo's, and speed controller (ESC) already installed, with flight and transmitter battery packs, and a appropriate battery charger.

NEVER fly a 2 Channel RTF jet!!  These jets are the imported "Kids Toy Store" variety with controls for the motor and rudder only!  You will learn BAD HABITS flying one of these jets, that you will have to un-learn to fly a proper Parkjet.

This is not to say that a 2 channel parkjet won't fly, your altitude is controlled by the motor, and steering is controlled by the rudder. It's your money, if you want to waste it, and then go right ahead. These toys are not my choice of plane to fly, the only thing there designed to do is separate your money from your wallet.

A Room to Build and Store Your Aircraft!!!

Find a space, and call it your own.  Don't let anyone in there (especially Animals and Children) These ParkJets take time to assemble (although I have read of one modeler building a jet in One day) glue and paint have to dry; epoxy has to set, and so on. 

YOUR MOST IMPORTANT PURCHASE

Is going to be your Battery Charger!! I know what your thinking, your Transmitter is more important, but this is not necessarily true.

You may buy several transmitters, but most likely you will only purchase a single Battery Charger.  Of course, how you fly, and the number of planes you fly at one time, may have a bearing on your "Need" for additional charger.

Charging takes time, and the only way to charge multiple packs of batteries quickly, is to use multiple battery chargers.

Your battery charger is the life blood to your flying hobby.  Once you get to the point of building and flying your own ParkJets, you will most likely be using Lithium Polymer  (Lipo) batteries.  So, it only makes sense to buy a changer that can handle Lipo batteries, and charge them SAFELY.

A lot of changers will charge Lipo batteries. The only "Problem" with many battery charges is that they require a 12 VDC Power Source.

One good way around this "Problem" is to use a Portable Power System, commonly used for roadside emergency Battery Jumping. J.C. Whitney sells several models.

You can recharge your batteries away from your car, and you can even take the unit right out to the flight line with you to charge your battery packs all day long!!

Another "Must Have" tool is a Power Meter. You can use these meters in a variety of ways.  Use it to monitor your battery charger, to see how much "Juice" your battery is taking.

Use it to test and monitor power set-up's, check the Voltage, Amperage, power (in Watts), Amps-per-hour, and Watt's-per-hour.

The Hyperion E-Meter (Left Side) and the Medusa Power Analyzer Plus (Right Side) can connect to your PC and download the information collected so you can produce graph's and record a "History" of your batteries and equipment (an easy way to spot potential problems)

The Hyperion E-Meter will also function as a tachometer, and It can also program the Hyperion Tital Brand of Brushless ESC's. You can read a discussion in the RC Groups about the Hyperion E-Meter here. You can also view a 20 Meg Video about the Hyperion E-Meter.

Special Thanks to RCParkFlyer for this article

SENSIBLE SAFETY TIPS

SAFETY BASICS

Most people enjoy flying ParkJets because they are not restricted the way that Fuel and Turbine Jets are.  They feel they can avoid the hassles and fees associated with flying fuel planes, by flying small electric planes in large open areas, or public parks.

However, just because you can do something, it doesn't mean that you should do it, if your not going to do it in a safe manor.  You need to follow a new common sense safety rules, which can save yourself and others from having needless accidents.  Finding the Right Place to fly.

MAKE SURE IT IS LEGAL FOR YOU TO FLY IN THE AREA YOU HAVE CHOSEN!!!

Some communities have banned flying any type of Radio Controlled aircraft, not just Fuel planes, in their city parks.  Check with your local Park or Recreation Department, or the local Police Dept., regarding any R/C flying restrictions that your community has.

If your community has banned parkflying, try to find someone with suitable private property, and go ask them (Nicely) if you can fly over their land.

If all else fails, Join a Local AMA Sanctioned club.  (Believe me, any dues you have to pay will more than cover the cost of one citation for breaking a local ordinance..)

Remember, ignorance of the law is no excuse!!  If you want the right to fly your Parkjet, it is your obligation to know the local laws and rules governing your hobby.

Your Flying Area

At a minimum you should only fly in an open area that is 500 Ft. X 500 Ft. (almost the length  of 2 football fields end to end)  A ParkJet flying at 60 mph will travel 88 ft. per second.  Giving you roughly 6 seconds before you need to make a turn-around.  Not much time at all.

If your field is larger, say 1,000 ft. your straight line flying time increases to about 11 seconds.  1,000 ft. is about the range limit of some of the micro receivers in use today, so plan according to your needs.

General Rules

The Area you fly in must be relatively level, with no trees, or any other obstructions to block your line of sight with your plane.

You cannot fly within 3 miles of any airport.

You cannot fly higher than 400 feet high without invading general aviation airspace.  (Some AMA flying sites have FAA Wavers allowing their members to fly higher)

You should not fly within 3 miles of any OTHER flying sites.  (transmitter overlaps)

Avoid areas of tall grass, farm crops, etc.  (It's very difficult to find a plane in a corn field)

Avoid area's with lots of people!!!!   The 4th of July is NOT the time to be flying your ParkJet in your local park.  (More on dealing with people later)

Always set yourself up so you can launch into the wind, and land into the wind.

Avoid flying in un-safe conditions, High Winds, bad weather, etc...

Flying with Others

Flying with other people calls for some special requirements:

Spectators: NEVER fly when the number of spectators or passers by exceeds your ability to keep track of them as well as your model. A helper or spotter can keep you informed of people walking past. A faster more challenging aircraft will severely restrict your ability to watch people while you’re flying.

The one thing that people love to do is watch others fly. Children especially love to watch, and they will most likely run over to you and start asking questions. If you have another person with you, ask them before hand to take care of any "Distractions" that may happen.

If you’re alone, just tell them that you will answer all of there questions AFTER You Land. Have them stand behind you at all times, and keep your model in front of you!

Other Flyers: Getting together with your friends for a day of flying is one of the best times you can have in the R/C World, but it can also cause problems if you’re not careful. You do need to follow a few rules from the AMA Safety Guide however....

CHECK YOUR TX FREQUENCY'S

To make sure no one else is using your frequency when you are flying.

1. I will have completed a successful radio equipment ground-range check before the first flight of a new or repaired model aircraft.

2. I will not fly my model aircraft in the presence of spectators until I become a proficient flier, unless I am assisted by an experienced pilot.

3. At all flying sites a straight or curved flightline must be established, in front of which all flying takes place. Only personnel associated with flying the model aircraft are allowed at or in front of the flightline.

4. No powered model may be flown outdoors closer than 25 feet to any individual, except for the pilots and helpers located at the flightline.

5. Under no circumstances may a pilot or other person touch a model aircraft in flight while it is still under power, except to divert it from striking an individual.

6.If there are several planes in the air at the same time, use a spotter to keep track of the other aircraft, and to warn you about aircraft flying too close to you or your ParkJet.

7. Call out your Intentions (Landing, Taking-Off) so your friends can fly out of the way.

That wasn't so bad now was it :)

One LAST Golden Rule: KNOW WHO TO CALL IN EVENT OF A FIRE OR OTHER EMERGENCY, AND HAVE THE MEANS TO CONTACT THEM!! 

Special thanks to FlysLikeABeagle and Grejen for these suggestions