The choices for EDF are both vast and exciting when you start to venture off the beaten path. EDF enthusiasts that want to advance faster than the current mainstream market allows must find other power system components and host planes from a variety of smaller vendors.

Higher power EDFs and Do-It-Yourself conversions aren't for everyone as they can push the limits of today's technology, and your skills, so these projects are usually best suited for the advanced modeler.

If you want a larger model with more power or maybe a good building fix, you don't need to spend thousands of dollars on an R/C model. With the right skill set, and attitude, you can create something impressive enough to get noticed at any flying field.

My focus in this month's issue of AMP'D is to show some higher power EDF models that, without breaking the bank, can be flown off grass, have functional retracts, and provide enough thrust to make that awesome jet sound!

The F-4 Phantom-II is a large foam EDF model. It is one member in a series of Styrofoam EDF jets from FlyFly Hobby. These models are distributed overseas by Hobby88.com or here in the U.S. by Electric Jet Factory (EJF.com).

If you are not familiar with FlyFly Hobby foam jet models, they are uniquely engineered designs that are made from EPS foam. The large jets are designed for 90mm EDFs and fit together like a precision 3D puzzle piece. They come with the ducted fan unit and fixed landing gear. They can be hand-launched over grass or fitted with optional retracts.

My favorite way to power these 90mm FlyFly models is to use the following components. I replace the FlyFly rotor with a more efficient WeMoTec MidiFan rotor and keep the perfect fit of the FlyFly DF in the model. The Great Planes AMMO inrunner motors have worked very well for me and the Castle Creations ESCs truly meet their rating. I also use a quality LiPo pack like the Enerland 30C series Lipos.

In general, these big foam kits are easy to build and fly. I protect the outer surface with a coating of Bob Smith Industries 20-Minute Finishing Epoxy. They provide a good host for a larger, more powerful 90mm EDF system and look great in the air!

F-4 Phantom II Power System:

• WeMoTec MidiFan 90mm rotor replacement on the FlyFly DF Unit
• Great Planes ElectriFly Ammo 36-56-1280kV Brushless Electric Motor
• Castle Creations Phoenix ICE Lite 75-amp ESC
• Two Enerland 3s 30C 5050mAh LiPo packs in series

The Nitro Planes Predator UCAV comes complete with fixed landing gear, fiberglass canopy, missiles, and all hardware. The model can be powered by a 90mm to 101mm (3.5" to 4") EDF unit. On sale, I have seen this model sell for as low as $120.

Features

• Top quality wood construction
• Fiberglass fuselage and canopy
• Sheeted built up balsa and plywood wings
• Comes with hardware and accessories

My power system for the Predator UCAV is a WeMoTec Midi Pro 90mm EDF for 5mm shafts, Medusa Research MR-3680-1100V2SE-5 Inrunner Brushless motor, Castle Creations HV85 ESC, and two 6s Enerland (30C) 3200mAh LiPo packs in series. The motor was a great fit for high-powering a low-cost 90mm EDF and at only $150. On a 12s LiPo supply, it can provide burst power up to 3300 watts at 74amps current. This delivers 7lbs of EDF thrust for a powerful 390w/lb. All these components, except the motor, can be obtained from Hobby Lobby International.

The fiberglass canopy is pre-finished and only needs the latch mechanism attached. The landing gear are fixed with a steerable nose wheel assembly. Two sheets of finishing decals are supplied and the 7-page manual, although sparse, provides sufficient photos and text to complete the model by an experienced assembler.

A closer look at the fuselage reveals the size, quality finish, construction techniques, and high level of pre-assembly. The T-nuts are already installed, and glued in place, for the gear mains and steerable nose wheel assembly. The battery and servo trays are also pre-installed. It is always a good idea to check for bad glue joints where the formers meet the fiberglass and high stress areas like the gear mains and EDF mount.

Some modelers fall into traps with these lower cost models from China. Without realistic expectations, an improper attitude to complete the project may not be a recipe for success. That being said, you should expect some missing parts, some not so great fits, and glossed over details on assembly and proper CG placement. Plan to utilize your full skill set.

With the proper expectations and skill set, you can feel confident that you bought at least a decent shell for much less money than other models on the market.

After gluing in a pair of 2-1/4" long hardwood slats, the Midi Pro fan fit perfectly in the ducted fan bay. I'll be using the air intake ring that comes with the Midi Pro fan because the bay area opens into a large area.

Hitec HS-81 servos fit perfectly in the plywood bay frame opening. I secured 36" HD extensions to the control lines by first tying the connectors with Firewire fishing line and then covering them with shrink wrap. The lighter .6oz HS-81 servos will provide 42oz/in torque on my 6v CC BEC.

The main landing gear mounted very well without any issues. The holes were pre-drilled in the fuselage and T-nuts already mounted in the former. I only needed to cut off the excess axle length with a Dremel tool. However, the steerable nose gear installation was not as easy. The hole for the gear wire was not marked on the fuselage so I installed the plastic piece inside the fuselage first since the T-nuts were already installed. I used a long rod with a sharpened end to press through the gear wire holes on the plastic piece to create an aligned hole from the inside to the outside. The hole was then opened with a 11/64" drill bit.

All the holes in the plastic piece also needed to be opened. I used a 1/8" bit for the screw holes and a 11/64" bit for the gear wire. The smaller nose wheel hole was also opened with an 11/64" bit. Once installed, it allowed me to finally sit the Predator UCAV on its own wheels. It is not a bad idea to replace the stock nose wire with some real 5/32" steel music wire. Du-bro makes a very nice (#154) 5/32" Universal Nose Gear Wire with 4 coil turns for added shock absorption.

Note that the Medusa V2 motor wires come out at a right angle for an easy exit through the exhaust tube. The motor shaft also has a flat side for the set screw on the Wemotec Midi Pro 5mm adapter to keep it from spinning under high RPMs. The power system measurements are from Carl Rich. (12s LiPo, 75amps, 3333 watts, 200mph e-flux)

I installed 4mm gold bullet connectors between the motor and ESC. The main power lines got 6mm gold bullet connectors so they don't get hot enough to melt solder. I will make a series adapter with Dean's Ultra connectors for each 6s LiPo pack and 6mm bullet connectors going to the CC HV110 ESC.

Note the 100 ohm resistor used for anti-spark connection on the 12s supply. This worked very well on my larger 4500 watt Byron EDF conversion. Also note how well the 36mm (diameter) x 39mm (length) heat sink fits on this setup. All my new models (including reviews) that are 6s or higher voltage will have the anti-spark feature added. I buy the 100ohm, 1w resistors on-line at Newark Electronics for 5 cents each and there is no minimum purchase. Radio Shack is another good place to obtain the resistors. You can get all the anti-spark details in the Ask AMP'D section of issue 2 of AMP'D called, Arming the Big Boys.

The Wemotec Midi Pro EDF is the industry leader for efficient 90mm fans. Although the Pro rotor itself can still be used in other ducted fans, I have found that the Wemotec EDF is the easiest to assemble of the 4 manufacturers I have used.

For a complete build thread on the Predator UCAV, go here.

The Nitro kit does come with a nice piece of thick Mylar so I cut it down to 90mm size using the same FSA ratio as in my FlyFly EDFs.

I bent the motor wires at a right angle to plug into the CC HV85 ESC without hitting the wall. The wires are also twisted so that they are flat in-line with the Wemotec mounting tab. This allows for an easy slice out of the Mylar to make the exhaust tube fit.

The Spectrum AR7000 dual receiver was mounted to the side with Velcro.

On strong power systems using two packs in series, I use a separate receiver pack (2-cell 1500mAh LiPo) and a Duralite (DUR65060) 6v regulator with a fail-safe switch for safety.

I had been warned by other modelers that the battery (or batteries) needs to be placed behind the nose gear servo in between the two air intakes. It seems obvious that the manufacturer had never tested the design with EDF. I have seen this several times before on other designs from overseas so I thought about a solution.

I decided to build a battery box that allowed the packs to easily slide in place and have holes for some cooling. The battery packs will be secured with a Velcro strap across the top. The battery box partially blocks the air intake openings but they seem large enough to make the blockage insignificant. My initial setup used two FlightPower EON28 6s 3350mAh packs in series.

My Nitro Predator UCAV was Ready-To-Fly at 8.5lbs. The empty plane weighed 100oz (6.25lbs) and my two 6s EON packs weighed 36oz (2.25lbs) together. The 3300 watt power system provides a powerful 390w/lb!

We had some good success with our first test flights on the Nitro Predator UCAV. The power system was awesome and had no problem taking off grass. After landing hard on the first few flights, we moved the CG from 7.25" to 7.75" and had much easier take-offs and landings.

The Predator flew very stabile, even when it was flown slower. The EDF jet performed loops and rolls with ease. We discovered that when landing, you need to carry a certain speed or the plane will pitch up if it lands too slow. The pitch-up is due to the fact that the V-tail stops flying first when the air flow is low and simply drops.

I did permanently glue on the wings for added structural integrity. The rather soft landing gear act as shock absorbers on those less than perfect landings and they are easy to bend back in place after first removing them from the fuselage. We left the nose gear bent backwards as it seemed to still take-off and land well until I finally replaced it with the Dubro 5/32" Universal Nose Gear Wire. The coil spring in the nose gear still works when the gear is bent back.

The fact that the aluminum gear mains bend upon hard impact is a real plus as it absorbs those less than perfect landings.

The Predator UCAV was a very fun project and exceeded my expectations for a larger EDF model without breaking the bank.

My Byron A-4 Skyhawk was originally built about 18 years ago by Dominic Cognata (RCU's "Major Woody") and flown with an O.S .91 glow engine. At one time, these high-end kits were at the top of the R/C world but are now considered outdated. The stock 6" diameter Byron fan put out between 10-12lbs of thrust. The air intake openings for Glow Ducted Fan (or GDF) are larger than needed for turbine-powered jets but are a great fit for EDF. The new EDF components available today weight similar to their original glow-powered counterparts but the power system can now deliver about 15lbs of thrust for improved flight performance.

Older Byron jets like my A-4 Skyhawk can be purchased at auctions or through R/C clubs. They make a great host for a higher powered EDF conversion without breaking the bank. New kits and spare parts can still be purchased from the Iron Bay Model Company. I have found the best approach to contact them is to keep calling them on the phone until someone answers.

The plane was in good shape but required some minor repair and upgrades. All the servos were replaced with JR DS-821 Digital Sport Servos and the elevator and rudder controls were re-designed using short linkages with the servos in the tail. The 72MHz receiver was replaced with a Spektrum AR7000 2.4GHz dual receiver. The nose gear got a Robart strut upgrade and the slimy exhaust tube needed to be replaced.

The Byron A-4 was originally flown with the O.S. 91 engine shown on the right. The new EDF components weighed slightly less than their original glow-powered counterparts but it was not significantly different. The glow engine and fan weigh in at 1.5lbs. When we added the tuned pipe, Rx. battery pack, Byron duct unit, extra servos for throttle and fuel mix change, we eliminated over 3.25lbs not counting the slimy exhaust tube, 24oz fuel tank and 2oz header tank. All in all, we estimate removing about 5lbs for the GDF power system.

The new power system for my A-4 uses an E-Turbax ducted fan unit from Jet Hangar International. It is powered by a Neu 1527/1.5Y motor, Castle Creations HV110 ESC, and two 6s Enerland 5050mAh LiPo packs. The Byron conversion with the Neu 1527/1.5Y motor on a 12s LiPo produces about 4500 watts.

The E-Turbax unit assembled quite easily using the supplied instructions. The only difference is that the tail cone is no longer supplied as it was an expensive custom carbon piece that had no real benefit on the air flow.

I was impressed with the machined quality of the E-Turbax fan and consider it an excellent value for this type of product.

My EDF test stand was once again modified for the larger 120mm unit. It had been previously used to test 70mm and 90mm setups. I extended the motor wires using 18" of #10 gauge Castle Creations silver wire and connected them to the CC Phoenix HV110 ESC using 6mm gold bullet connectors.

For initial testing, I'm using a gold Dean's Ultra connector for the two 6s packs in series. I haven't seen a problem in the past when passing 95-100amps through them but this application may be at a higher current for longer periods than my other applications. I had been warned that others have melted the wires off the Dean's Ultra connectors, when used in higher power EDF setups like this one, so it is best to use 6mm Gold bullet connectors.

My initial low RPM testing with a single 6s pack was very successful and exciting! I then upgraded my HV110 ESC to the latest software over the Internet using the CastleLINK USB Interface and disabled the brake function. The packs shown are very old Kokam 6s2p 20C 4200mAh packs that have seen plenty of use. The old FMA BalancePro HD connectors kept the packs healthy over many years through balanced charging. I initially used these older packs to see what happens on a 12s setup in my EDF test stand as I was waiting for some of the new chemistry Enerland 30C packs to arrive.

I bought a new cockpit for my A-4 from the Iron Bay Model Company. I used a pilot from Nitro Planes and imaging from a real A-4 cockpit from the Special Cockpit Edition of Code One Magazine.

I decided it would be easier to paint my canopy frame flat black rather than try to match the grey paint from 18 years ago. I used inexpensive spray enamel from Valspar called "Odds N Ends". It is available from Michael's Craft Stores or Home Depot for only $3 a can.

We replaced all the servos with JR DS-821 Digital Sport Servos and eliminated the long nyrod linkages. The old Byron Skyhawk now has the rudder and elevator servos in the tail with short metal linkages. We also installed a Robart 656 Straight Robostrut w/Fork and used a solid rubber Robart (225TL) Treaded Lightweight wheel for the nosewheel. I added some spacers to eliminate any side-to-side movement of the wheel. By mounting the servos in the vertical stab, it stopped the fin sides from being able to come together or spread apart, eliminating any flex.

Before installing the wings, I rubbed some silicone lubricant onto the rubber seals that plug into the fuselage sides to connect the air line. After pumping 100lbs of air pressure into the tank, the old SpringAir retracts came back to life!

A plywood collar was made to close the gap from the original Byron GDF 6-1/2" opening down to the E-Turbax 5-1/8" opening. Initially, I tried using some 1-1/2" long aluminum channel stock (in 4 pieces) above and below the EDF bracket but decided that the two 2-1/2" steel brackets I bought at an Ace Hardware store for $0.79 each would work better and easier. The motor wires will route between the former and fiberglass body like the existing servo wire.

I modified a new Byron thrust tube from Iron Bay Model Company to fit the smaller diameter needed for the E-Turbax. The dimensions are as follows:

• Length: 27.5"
• DF end 4.88" diameter (x Pi = 15.3" circumference)
• Output 3.75" diameter (x Pi = 11.8" circumference)

A 5" hose clamp will hold the thrust tube in place around the EDF and a hole will be cut about an inch back from the motor to drop the wires through.

Note that an output diameter of 3.5" would favor top end speed while a diameter of 4.0" would favor thrust. The recommended compromise between thrust and speed is 3.75". This is where I decided to start and see just how much of our 600' long field length is needed for take-off. The Byron A-4 does not have flaps.

To close the gap between the thrust tube and the fiberglass body, I made a custom "ring" of foam that fills the gap and stabilizes the tube. I cut a 1-1/2" wide plastic ring from a CD case cover which is about 5" in diameter and then custom glued it to just fit around the 3-3/4" thrust tube end. I then glued a thin 1-1/2" strip of foam to this thicker plastic ring made from the CD case and pressed it in place. In this manner, the thrust tube does not get distorted by the foam. It is held by double-side tape between the plastic ring and the thrust tube so it cannot slip.

I held down the control and motor wires with some homemade balsa pieces and CA. The other set of servo control wires is held in place with some 3M cord clips. The CC HV110 ESC is secured by both a Velcro plywood plate and a Velcro "seat belt". I can pick up the entire jet by the ESC so it is secured well and resides in the secondary air flow out of the way of the primary air flow for power.

Once the wires were secured, I created an air intake scoop from a large plastic funnel I bought at an Ace Hardware store. The scoop directs all air from the 9" fuselage to the 5-1/8" E-Turbax opening. The photo shows it sitting in position but not yet mounted.

To safely power the A-4, I used a Duralite Flight Systems 6v regulator with a built-in fail-safe On/Off switch. The regulator supplies 6.0 volts at 7.5amps continuous current with spikes up to 10amps. If the switch fails, the regulator remains on.

The regulator is fed by a 3oz, 2-cell Kokam 1500mAh pack which I modified to use the FMA Cellpro Multi4 charger.

Likewise, my two 6-cell Enerland 5050mAh packs will be charged by two Cellpro 10s chargers. These chargers provide safe balanced charging at up to a 3C rate. My 6s 30C packs can be charged at a 2C rate on the Cellpro 10s charger for a 30-minute charge time.

I came up with a convenient way to arm the 12s LiPo power system on the Byron EDF conversion which eliminates any spark. By touching the 100ohm 1w resistor lead to the + side of the HV110 ESC and then sliding the 6mm gold bullet connector in place, the spark is eliminated. The main red ESC wire sits in a safe channel so it doesn?t move around but the exposed resistor wire can also be easily covered with a piece of tubing, once the system is armed. The paper in the photo is positioned to make the connectors easier to see.

Resistors like this can be purchased at many places. Mine cost $0.053 from Newark Electronics On-line. Newark Part No: 71M1113 1w Metal film resistor.

These new generation Enerland (PolyQuest) 6-cell, 30C, 5050mAh packs promise increased cycle life and performance. Since they can deliver up to 150amps continuous and 200amps burst, I will not be stressing them in my Byron EDF conversion that draws only 95amps at full throttle. The new packs should be available at Hobby Lobby soon.

The larger #8 gauge wires on these Enerland packs fit my 6mm Gold bullet connectors perfectly. I found another source for these connectors at Tower Hobbies. Great Planes GPMM3116 Gold Plated 6mm Male connectors and GPMM3117 6mm Female connectors. Another nice improvement is the single node connector for a 6-cell pack. The balance node connector plugs in perfectly to my FMA Cellpro 10s charger using the ThunderPower/PolyQuest adapter.

When the Byron A-4 was ready for test flying, I measured the following weights:

• Main Fuselage = 145oz (9.06lbs)
• Wings w/Retracts = 44oz (2.75lbs)
• Two 6s 5050mAh Enerland Batteries = 51oz (3.2lbs)

The plane without e-fuel was 189oz (11.8lbs). The total RTF weight was 240oz (15lbs). The thrust was equal to the weight which was an improvement over the original glow-powered system.

Pilot, Lynn Bowerman, and I had a great day test flying the Byron A-4 EDF conversion with the new Enerland 30C 5050mAh packs. The power level was excellent! I used 6mm Gold Bullet connectors on the packs which eliminated the Dean's Ultra connectors and the need for a series harness. The 200-amp rated bullet connectors allow you to simply chain packs in series and the 95-amp draw at full throttle would not produce enough heat to melt the solder connections.

After several successful taxi tests on grass, we decided to let it fly! The Byron A-4 seemed well balanced and even landed very well. On one of the taxi tests or take-off, the nose gear wire was bent back but it didn't affect the ground performance.

Flights were a short 3 to 4 minutes as we were pushing the A-4 hard in the wind. Higher capacity 6AH packs may provide more stick time but we are not sure what effect the extra weight would have on the A-4 handling. The nose gear bent aft again but didn't seem to affect the ground handling at all. I ended up replacing the metal pin going into the retract mechanism and used a slightly larger 2-1/4" Dubro wheel.

Overall, we were pleased with the EDF conversion performance on the Byron A-4 Skyhawk. It flew better than it ever did with the original glow-powered engine and we see about 135mph speed using an internal GPS device.

After about 15 flights, we continue to have success with the Byron EDF conversion. The trickiest part is landing without flaps (and no breeze) because there is about a 5mph window that makes or "breaks" a successful landing. Perhaps we will add some flaps to it over the winter. One of the photos below shows the proper alpha landing position where it touches down nice and sweet. We "clocked it" with an internal GPS device at 135mph. After the 10th flight, I added a silver fuel tube for an added scale touch.