Issue 15

Article By Greg Covey

Print Issue 15 "Go Panthers!"

Normally, this would be a loud cheer for a sports team, but in this column, "Go Panthers!" is all about EDF. If you're a fan for those early jet designs from the 1950s, you can build or assemble your own electric-powered F9F Panther from numerous types of materials.

In addition to the many ARF designs currently on the market, you can still find kit versions or plans available if you prefer to build. New, lower-cost EDF components are providing incredible power levels in any size R/C model.

In this month's issue of AMP'D, we'll assemble several different types of Panther models ranging from lower cost foam designs to a higher-end German-engineered fiberglass model that will break 150mph!

Materials for Models

R/C models are now being made from many different materials that vary in weight, strength, thickness, and cost. Here is a brief description of some of these materials and their properties.

At a distance, you often cannot tell what materials some models are made from until you actually get closer or hold them in your hand.

• EPS Foam - Sometimes called "cooler" foam as it is a similar material to the inexpensive beverage coolers. Although very light and inexpensive, the foam dents and scratches easily.

• SEPO Foam - This foam is a higher density than the EPS foam. The smaller cells provide a smoother finish. Although it is slightly heavier, it resists dents and scratches.

• PC Coated Foam - A revolutionary new PolyCarbonate (PC) process that provides a hard 0.3mm shell finish over foam. It won't dent, break, or shatter. The PC is a lightweight coating that is lighter than fiberglass and adds durability to foam never seen before. The smooth glossy finish can be painted without surface preparation with a result that resembles a fiberglass model but has a lower cost.

• Fiberglass Composite - Fiberglass is material made from extremely fine glass fibers. It is used as a reinforcing agent for many polymer products where the resulting composite material is known as fiber-reinforced polymer (FRP) or glass-reinforced plastic (GRP). The Aeronaut F9F Panther that I assemble in this column uses GRP which is commonly referred to as fiberglass. Thermosetting plastics are normally used for GRP production, most often unsaturated polyester but vinylester or epoxy is also used. As with many other composite materials (such as reinforced concrete), the two materials act together, each overcoming the deficits of the other. GRP becomes a material that resists both compressive and tensile forces well, making it a superior lightweight material for model aircraft. This superior material, when properly made, comes with added cost.

• Wood/Balsa - A classic built up balsa kit of the F9F Panther is available from RBC Kits. The kit contains all cnc cut wood parts that provide an accurate fit of lightweight easy to assemble components. The wood kit is complimented by vacuum formed tip tanks, canopy and nose cone. The RBC Panther model is similar in size to the Aeronaut F9F Panther but they are completely different in construction and targeted at different customers. While built-up wood kits are generally light weight and less expensive, they do require a higher level of craftsmanship to complete.

Shenzhen Lander Technology Company

The Shenzhen Lander Technology Company (aka RC Lander) is an innovative organization that makes R/C models and accessories. Based in Shenzhen, China, the group has 50 employees and two floors of factory area around 1,800 square meters in size.

RC Lander specializes in EDF systems and has developed a reputation for exciting products.

One of the owners of RC Lander is Designer and Engineer, Tim Wan. Tim is well known in the R/C industry and has over 20 years of experience flying models from nitro-powered planes to EDF jets and helicopters.

Tim has designed many great looking Panther and Cougar models. They not only look great but they fly extremely well and come with many accessories like flaps, retracts, and working wheel doors. Here he is posing with a new 90mm PC coated foam MIG-17 design soon to be released.

RC Lander has some exciting new designs for 2010 that include different materials and larger 90mm and 120mm power systems.

RC Lander PC Coated Panther

Many RC Lander products are now available at Nitro Planes. RC Lander did a good job with their packaging as each part was wrapped in protective foam and the box was divided into compartments that matched the size of the parts. There were no smudges on any of the parts or on the glossy PC covering. The Panther kit even included little bottles of part A & B epoxy in the parts bag. An all metal RC Lander 70mm EDF with balanced rotor is also included.

The PC version comes complete with the ESC and CBEC already soldered up with pseudo-Deans connectors on the battery side and gold pin connectors on the EDF side. The kit also includes a pre-soldered, ready-to-use series connector if you want to use two 2s packs in series instead of a single 4s pack.

On the wing (left below), the ailerons and flaps are pre-hinged and the servo pockets come with color coded PC covers. Before I knew it, I had the servos installed, the covers in place, and the control rods adjusted.

The RC Lander all-metal suspension strut gear system (with doors) comes completely installed with the servos and control rods already in place. However, there is some tweaking necessary to finalize the correct action of the retracts and doors.

The door covers for the gear mains are attached to the struts and then the wheel doors close after the mains are in their pockets. The cover action is controlled by fishing line attached to custom designed servo horns. Everything is adjustable as shown in the photos.

The nose wheel steering uses its own servo, which is also pre-installed. I mixed the nose wheel steering to the rudder channel with my Spektrum DX-7 transmitter.

The RC Lander all-metal suspension landing gear (available as an option on all of the other models; standard EPS and EPO) are an excellent value.

The tail section required the horizontal stabilizer to be glued in the pre-formed slot on the vertical stabilizer. The elevator comes factory installed but the rudder needed to be hinged in place. I used ZAP-O Foam-Safe CA to glue these areas. Next, two servos were placed in their pre-formed pockets after first covering them with masking tape. The servos were then installed using hot melt glue, so if needed, they can easily be replaced or repaired. Two 12" servo extensions were attached, one to each servo, and the tail feathers were glued to the fuselage using the supplied epoxy.

Once the control rods were attached to the aileron and flap servos, the wing surfaces were tested. The wiring in the wing bay was cleaned up and the extension connectors were hot glued in place to keep it neat.

Tim Wan did some great design work with his new all-metal EDF units. Included in the PC coated version was the new EDF with 6s capable 2399Kv inrunner motor and balanced rotor. The unit produces 4lbs of thrust when drawing about 60 amps of current. The gold pin connectors were already soldered onto the motor wires.

The EDF unit was connected to the ESC/CBEC system and became a drop in fit. The cover fits like a glove and only two screws are used to keep it in place.

The electronics bay was cleaned up because there were wires that needed to be kept out of the way of the retract mechanism. I like to label each servo lead wire that gets connected to the receiver so you can always plug it in with confidence.

The Panther looked rather "naked" without the decals applied in the top photos. Even after they were applied, I decided that the panel lines needed to be more visible. I found some permanent, fine point markers at Michaels (or AC Moore) in an assortment of colors. A dark grey was used to fill in the molded panel lines which resulted in an almost natural weathered look.

We did a video to show the action of the retract system and the covers. It actually works quite well although the mains had a tendency to bounce when the plane was inverted for the video.

RC Lander Panther Retracts Video (6 meg)

Aeronaut F9F Panther

The Aeronaut F9F Panther fiberglass EDF model was designed after the Grumman F9F-5 Panther. The decals supplied in the kit (125183 / WL-25) displayed the markings of VMF-311 (Marine Fighter Squadron 311) which was based in Pusan, Korea in 1952 during the Korean War. Originally constructed as an F9F-4, the jet was completed as an F9F-5 before delivery and is now displayed at the Pima Air and Space Museum on loan from the National Museum of Naval Aviation. The F9F-5 was effectively an F9F-4 with the stretched fuselage and taller tailfin, but with an improved derivative of the Nene turbojet, known as the Rolls-Royce "Tay".

The Aeronaut model has a 52" wingspan and weighs about 7-8lbs when flying. It is an all fiberglass ARF with German-engineered quality which is the best I have seen to date. It sells with and without retract bays for about $700 at Icare RC and Ductedfans.com in the U.S. and at WeMoTec overseas.

The original release of the Aeronaut Panther in 2003, which is what I have, did not have landing gear bays or cutouts in the fuselage. It took off from grass using only 700 watts on 16-20 NiCd cells. It could cruise around on only 200 watts in low wind conditions or speed up to over 100mph. The second release around 2007 had gear bays, cutouts, covers, and a battery bay.

My power system for the Aeronaut Panther would use newer technology components along with the proven high-quality WemoTec Midi Pro 90mm ducted fan with its dynamically-balanced rotor. I have used this fan on previous projects with up to 3300 watts without issue.

• ARC 36-75-1 Motor - The ARC 36-75-1 inrunner motor is designed for high-power EDF applications. It is distributed in the U.S. by LightFlight RC and can deliver up to 2700 watts on an 8-cell LiPo pack for only $130.

• Phoenix ICE 100 ESC - The new Phoenix ICE100 ESC from Castle Creations can supply 100 amps with up to an 8-cell LiPo pack. It also features a programmable 5-amp switching BEC for maximum servo power that can be set from 5v to 7v in 0.1v increments. The light design weighs only 2oz and has built-in Data Logging for only $140.

• WeMoTec Midi Fan Pro - The WeMoTec Ducted Fan for 5mm shaft brushless motors has a dynamically pre-balanced rotor for vibration free power. The 93mm outside diameter ducted fan comes with all the parts shown from Hobby Lobby for only $75.

• Blue LiPo - These new "Blue LiPo" batteries from Hobby Partz come in many size capacities, cell counts, and discharge ratings from 15C to 40C. I'm using two of these 4s, 30C, 4000mAh packs in series to provide a powerful 2700 watts in my Aeronaut F9F Panther.

General Assembly

Most of the Aeronaut Panther parts can be dry fit together right out of the box. I was most impressed with the quality of the fiberglass material as it was both light and strong. All the glue joints used aircraft-grade epoxy and they were very solid. The precision fit of the wings and tail were simply incredible!

The designer added SpringAir 602 retracts in 2007 but my original version without them was from 2003. I didn't mind because I fly off mowed grass fields and I knew that this Panther design would have no problem with it. In 2008, Aeronaut also released their own version of the SpringAir 602s and a new 90mm carbon fiber fan called a TF-2000 that handles bigger motors up to 3000 watts. Since I knew that the Wemotec Midi Pro fan can handle 3300 watts, I saw no need to buy an expensive carbon fiber fan unless you really wanted some weight reduction. My version of the Panther would already be lighter without the retracts.

Tail Assembly

The tail piece comes ready to mount to the fuselage so the builder need only glue the horizontal stabilizer and install a servo and linkage for the elevator halves. A template is provided to make an accurate opening for the stabilizer.

I also decided to cut a working rudder which had to be done in two halves. I used strong digital Futaba S3150 servos that would return to center accurately. Since I did not have sufficient room for clevis adjustment at the control surface, I was able to streamline the connections to the elevator and rudder halves. I used Sullivan Heavy Duty Pushrod Connectors on the servo arm for zero wobble.

I wanted a pull-pull rudder system on both halves but didn't have straight runs for using cable so I used Dubro Micro Pushrod Systems. By securing the tubing along the way to the servo, it made for a light and powerful control system. The elevator halves use much shorter runs of thicker rod and tubing supplied in the kit. I replaced the stock metal adjustable clevis with some Dubro 2mm Swivel Ball Links.

It may not look pretty underneath but both split elevator and split rudder now have precise tracking and return to center. None of the control surfaces had any wobble and the tail section was much more solid with all the bracing so I was happy with the result.

Wing Servo Assembly

My first precision cut on an expensive fiberglass model was made easier by using a metal ruler for a Dremel tool cutting guide. A tip picked up from Bob Ruff via Carl Rich. The two wings on the Panther were assembled using the same technique.

I first marked the position of the servo on the wing bottom and then boxed the area using masking tape. I decided to use less expensive Futaba S3115 micro servos for the aileron control since each aileron required a servo. The 0.80oz micro servo was a perfect size for the thin wing and provides 39oz/in torque on only a 4.8v supply. The servo was positioned inside the wing and held in place with epoxy. I used the stock hardware for the control linkage and glued the fiberglass cover back in place after cutting a section away to allow for the servo arm to swing. A Hobby Lobby (HLH550) Exit Cover was used to reduce drag and protect the linkage on grass belly landings. This versatile plastic cover can also be used in the reverse direction as an air scoop.

It seemed every time I touched the finished fiberglass surface, it made a perfect fingerprint mark. To clean up a plane section after assembly, I used a debonder on the tough stains and then wiped the wing using nail polish remover.

EDF and ESC Mounting

I decided to mount the wings in my Panther as the last step just before applying decals. It was much easier to work on the main fuselage area without the wings being in the way.

When using the Wemotec DF, instead of the Aeronaut TF-2000 DF, you need to mount the fan your own way. The stock Aeronaut TF-2000 DF uses a ring mount technique and mates with three blind nuts already mounted in the firewall. The carbon fiber TF-2000 DF is very expensive compared to the Wemotec Midi. The dynamically balanced rotor of the Wemotec Midi fan makes it the best quality standard on the market for a reasonable price. I already knew it can handle over 3000 watts from my previous Predator UCAV project.

I used a set of .60-size glow engine mounts to hold the Midi DF to the firewall. After first gluing some ¼" hardwood braces behind the firewall to add support, I mounted the glow engine posts using hex head screws and t-nuts. Note the lip from the fiberglass intake ducts fit snuggly inside the fan. This not only provides efficient air flow into the fan but also aligns the fan perfectly. The blue masking tape arrow was used to level the position of the glow engine mounts as it was difficult to get them perfectly aligned due to limited access to the firewall. I used thin ply angle brackets to provide the correction. The result was a very solid but removable DF mount to the firewall.

The Castle Creations ICE 100 ESC was mounted to the left side intake duct. In this manner, cooling air is forced over the ESC and I did not have to cut into the perfectly smooth belly of the Panther.

After installing the ARC 36-75-1 inrunner motor, I used an MPI (ACC3939) 36mm heatsink to aid cooling the back half of the motor. This low-cost aluminum heatsink is a pressure fit and has fins that minimize air flow disturbance.

The exhaust tubing material is supplied in the kit so I cut the proper size needed for an FSA (Fan Swept Area) of about 86%. The fan swept area is calculated by subtracting the area of the impeller hub from the area of the inside of the shroud. Choking down the airflow at the exhaust, increases exhaust velocity, which in turn will increase top end speed of the aircraft. There is, however, a point of diminishing returns: choking down the exhaust too much will back pressure the fan resulting in degraded performance. Additionally, a larger outlet area will increase the static thrust of the system, but lower the top end speed of the aircraft. Using a value around 85% produces a good compromise between static thrust and exhaust velocity. The Aeronaut Panther fuselage was designed for this FSA value so the exhaust tube was a perfect fit.

Before installing the ESC, I added about 12" of #10 Castle Creations wire to extend the leads to the motor. This results in no extra capacitors being needed on the battery leads. I used 6mm gold bullet connectors that can handle up to 120amps and need no harness to connect the two 4-cell Blue LiPo packs in series.

Note the single tywrap to hold the three motor wires together at the connectors. This keeps them from vibrating in the strong air flow.

Cockpit

The cockpit is still a work in progress. I really enjoy this part of any assembly and take some time to make it look good. My pilot is the ParkZone (PKZ4414) molded rubber pilot from their T-28. The Aeronaut Panther kit comes with molded cockpit, seat, and canopy sections that need to be cut out accurately to mate with the fuselage.

Panther Project Completion

My Aeronaut F9F Panther is near complete but will not fly until winter is over. Sometime this summer, a future issue of AMP'D will cover the Panther performance with photos, video, and an internal GPS speed reading.

Larger Panthers

If a larger model is what you are after, there are several options for making a 72" to 75" span Panther that flies around 15lbs to 20lbs. Many of the larger 120mm EDF power systems on the market today (shown below) would make a great power system for this larger size Panther.

PST Jets makes a very nice looking composite F9F-2 Panther with a 75" wingspan. The Panther comes in a variety of color options and has options available like a scale landing gear set and cockpit. Note that this model is designed for turbine power and would need some cheater holes in the bottom if converted to EDF.

Nick Ziroli has a set of plans available for those who want to build their own Panther from scratch. The builder could then allow for a larger air intake if using an EDF power system. An assortment of support kits for the Ziroli Panther design is also available from Kit Cutters Inc. All of Kit Cutter's wood is sealed in a nitrogen purged packaging to preserve the freshness of the wood and control moisture. The wood quality is the best that is available.

Although it is not yet available, a 72" span ASM Panther is being redesigned by Larry White of Jet Hanger International. This graceful warbird will be available for 14lb thrust turbine or EDF systems. The ASM Panther prototype has a wide speed range including excellent slow flight characteristics. Flying weight with the E-Turbax system and 12s 6000mAh LiPo packs is 18 lbs; top speed is approximately 150 mph.

Larger EDF Systems

• E-Turbax with Neu 1527/1.5Y Motor - This 120mm EDF combination from Jet Hanger International provides around 5000 watts of power for 15lbs of thrust on a 12s LiPo pack. The combined weight of the fan unit and motor is only around 33oz and a good value at only $470.

• XPS Dynamax Xtreme - The new XPS Dynamax Xtreme combination uses the proven Dynamax ducted fan unit with a "Big Screamer" outrunner motor from Little Screamers. Although the combined weight is a heavier 52oz, the unit has a wide range of operating power levels that produces from 11lb to 24lb of thrust utilizing a 10s to 16s LiPo pack. This unit is also a good value at only $439.

• Dyn-E-Max - This Dyn-E-Max / Scorpion motor combination utilizes the proven Dynamax ducted fan unit with a Scorpion outrunner motor. It can be used to fly a 15lb aircraft and provides around 4500 watts of power on a 12s LiPo pack. The lightweight combination weighs only 30oz and sells for only $564.

• Stumax SM110-45 - The SM110-45 EDF system is the latest from Stumax Aircraft. These power systems are available in North America from Performance-EDF, LLC. On a 12s LiPo pack using the Neu 1527/1.5Y inrunner motor, the system produces almost 17lbs of thrust at 5000 watts. The fan with motor weighs around 30oz and sells for $795.

• TamJets TJ100HP - The TamJets TJ100HP EDF system has a new stiffer rotor that can handle up to 4800 watts of power. It can use a Neu 1515 2Y motor and a 12s LiPo pack or be set up for other configurations depending upon the model size. The TJ100HP weighs only 5oz and a mere 18oz with the Neu 1515 2Y motor. The cost is around $700 with motor and $995 as a complete plug-n-play assembly that also includes a Castle Creations Phoenix HV110 ESC.

• RC Lander 120mm Set - The new RC Lander 120mm EDF set is an all metal plug-n-play combination that contains the integrated DF unit, 100-amp ESC, and powerful 830kv brushless inrunner capable of running on a 12s LiPo pack. This new package sells at Nitro Planes for only $299.

• Aeronaut TF-4000 - The Aeronaut Turbo-Fan 4000 comes in two versions; one for 5mm motor shafts and one for 8mm motor shafts. The TF-4000 offers high performance and extremely high-quality carbon construction. With a rotor diameter of around 120mm, the impeller generates a static thrust of up to 10lbs, making it an excellent choice for scale model jets with retracts. The carbon fiber fan unit itself weighs only about 4.2oz (120g). The DF without 10s to 12s capable-motor costs about $369 at Icare RC.

Summary

New, lower-cost EDF components are providing incredible power levels in any size R/C model. In addition to the many ARF designs currently on the market, you can still find kit versions or plans available if you prefer a good building fix.

Since you often cannot tell what materials some models are made from until you actually get closer or hold them in your hand, you can choose from many different materials that vary in weight, strength, thickness, and cost to suit your needs.

In today's R/C market, the product choices are vast. Established vendors offer new products that allow you to try something different with almost guaranteed success, while new vendors are emerging with technology changes that can satisfy even the most enthusiastic modeler. I have found that today's EDF designs are an exciting part of electric flight and offer many of us a fun way to challenge our spirit for new adventure.

When you fly electric, fly clean, fly quiet, and fly safe!

Special thanks for contributions by: "Papa Jeff" Ring

This section of AMP'D covers some of the questions that our readers have sent in and I thought would be interesting for others.

Steve S. asks:

Greg, I like your article on storing batteries, but I'm a little confused. If a

(what we call a 11.1 volt battery) is 11.4 at 1/2 charge, what is full charge?

Steve,

It's understandable to be confused because the manufacture ratings often try to mimic the older NiCd/NiMh packs using a so-called nominal cell voltage. A fully charged 3-cell LiPo pack is 4.2v x 3 = 12.6v unloaded. This means that if you measure a fully charged 3-cell LiPo pack with a voltmeter, it will read 12.6v when not connected to anything. If you were to connect the same fully charged pack to a load and draw a fair amount of current from it, it would read 3.7v x 3 = 11.1v. The problem is that the load on a LiPo pack must be much higher than 0.2C to drop the voltage to 3.7v/cell.

So unloaded, the half charge for a 3-cell LiPo pack is about 11.4v. It is easier to read the voltage of a LiPo pack with a voltmeter when it is not connected to anything but this voltage will drop once loaded by a receiver or servos or motor.

Ask questions by e-mailing me at greg@rcuniverse.com

Blue Lipo Batteries - Serious Power for Serious Hobbyists!

More everything! - JR X9503

The hybrid that's part plane, part heli and all fun! ElectriFly VFO

Hobby Lobby eRC Eurofighter EDF ARF

With full functioning canards and 360degree thrust vectoring, the Eurofighter lets you perform maneuvers that aren't possible with other jets. And, like all other eRC products, the Eurofighter is packed with modeler-pleasing extras like a detailed cockpit, Midnight Flyers LED light set and retractable landing gear with suspension. If you're looking for a super responsive jet that'll challenge your flying skills, then the Eurofighter is for you.

Print Issue 15 "Go Panthers!"