RCU Review: World Models Fun World EP

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    Contributed by: Greg Covey | Published: August 2004 | Views: 33978 | email icon Email this Article | PDFpdf icon

    The World Models Manufacturing Co., LTD.
    Unit 23-24, 10/F.,
    Kowloon Bay Industrial Centre
    15 Wang Hoi Road
    Kowloon Bay, Kowloon,
    Hong Kong

    T: (852) 2707-9783
    F: (852) 2798-0728

    Watch videos of the
    Fun World EP

    High Band Width

    • Great size for 3D flying!
    • Designed for electric power.
    • Flies superbly!
    • Excellent value ARF.

    • Ground clearance a bit short.
    • Wing rod holes drilled incorrectly.

    The new Fun World EP design from World Models is a scaled down version of their Fun World 3D plane that is meant for a 350 watt electric power system. I have been looking a long time for an ARF version of the popular E3D by Gary Wright and the Fun World EP is a very close comparison. The Fun World EP has a 2" longer wingspan and 100 sq. in. more wing area for a similar flying weight.

    Model: Fun World EP
    Manufacturer: The World Models Manufacturing Co.
    Wing Span: 50 in / 1270 mm
    Wing Area: 700 sq in / 45.2 sq dm
    Flying Weight: 3.3 lbs / 1450 g
    Fuselage Length: 50.0 in / 1270 mm
    Radio Required: 4 channel radio w/ 4 mini servos
    Power System: 350W electric motor system

    Power System Used:

    AXI 4120/14 brushless outrunner motor
    Jeti 70-amp Advance ESC
    KFS003 UBEC with 6v output (from Kool Flight Systems)

    Battery: (2) 15C 2AH Kokam cells.

    Kit Contents:

    The parts came very well packed and anchored down where needed. The model is almost finished and has many time saving features like pre-installed hinges that only need CA, and uncovered surfaces that need to be glued like the stabilizers.

    Individual Weight of Parts:
    Wing half w/ aileron = 4.3oz
    Fuselage = 4.7oz
    H-stab w/elevator = 1.3oz
    V-stab w/rudder = 0.6oz
    Gear and short control rods = 1.2oz
    Canopy (already pre-drilled) = 0.5oz

    I don't usually weigh the individual parts but I was impressed enough to do so after picking them up for the first time.

    Power System:

    The Jeti "Advance" ESC comes with mating plugs for the motor.
    The UBEC and ESC are wired together before connecting the AXI motor.

    One of the nice things about electric power systems is that 350 watts is 350 watts, so as long as you have a reasonable prop size, the solution you choose will work fine. I plan to use an AXI 4120/14 motor from Hobby Lobby with an APC 14x7 e-prop. The manual shows the use of a folding prop, so perhaps a Graupner CAM, or CFK folding prop is a good choice as well.

    For battery power, I'll use two of the new Kokam 2AH (15C) 2-cell packs in series for a 4s1p combination that provides a 30amp continuous current delivery capability weighing only 12oz. Alternatively, two 7-cell CP1700 NiCd, or 1950FAUP NiMH packs, wired in series would work, but would weigh closer to 22oz.

    To power my Fun World EP I'm using an AXI 4120/14 brushless outrunner motor, a Jeti 70-amp Advance ESC (although the 40-amp version will work also), and the new KFS003 UBEC with 6v output from Kool Flight Systems via Hobby Lobby.

    The 6v output UBEC is like using a 5-cell receiver pack to speed up your servo response and make them stronger. A great advantage for 3D flying! The UBEC weighs only about 1/3 of the 5-cell receiver battery pack and eliminates the need to keep a second battery charged since it gets its power right from the main flight pack. If the receiver does not have enough channel connectors to plug in the UBEC output cable, you can connect it in parallel with any channel using a "Y" adapter cable.

    Wing Assembly:

    Short control rods provide great strength and add little weight.
    The aileron servos are mounted first. World Models provides a string with a piece of hardwood attached to each end to draw the servo lead through the bay into the center side.

    I used Hitec HS-85 Mighty Micro servos from Hobby Lobby. They have ball-bearings and optional metal gears for added strength. The powerful 49oz./in. torque is similar to a standard size servo but the smaller micro-size case weighs only half the weight at 0.8oz. They fit perfectly into the servo bays.

    The short control rods provide great strength and add very little weight. The World Models ARF kit provides pre-bent and threaded rods for all the control surfaces. Even the rubber keepers are supplied.

    Tail Assembly:

    I chose to assemble the elevator first on a flat surface before installing it into the tail.

    The elevators and metal joiner rod are normally assembled on the fuselage after first gluing in the horizontal stabilizer.

    I chose to assemble it on a flat bench first, then glue the completed assembly into the fuselage. This insures a properly aligned elevator and makes it easier to glue the metal joiner in place. It does, however, require cutting out a small section of the tail to insert the completed assembly. I easily cut out the small section of tail with a sharp X-acto knife.

    The steerable tail wheel mounts easily and is included in the kit.

    The tail wheel mounted easily after first drilling a hole and cutting a channel for the metal rod into the rudder. After drilling pilot holes for the two screws, I applied some white glue to the threads before installing them.

    Huge control surfaces with a wide throw range are great for 3D flying!

    The finished tail had thin seams and wide swings on very large control surfaces. I had a good feeling about the potential for 3D performance. Both rudder and elevator HS-85MG servos are mounted in the tail to use short control rods for tight, responsive throws.

    Gear Mains:

    The stock main gear is light yet strong.

    The main landing gear is designed to be strong and light. It assembled easily by drilling pilot holes for the six screws to hold the three straps. Plastic washers and metal collars are included in the kit to hold the wheels in place.

    Mounting the AXI:

    The AXI Radial Mount Set was used with the stock plywood formers.

    To mount my AXI 4120 motor, I used PM41002 Radial Mount Set and the stock Fun World EP plywood formers. I did have to supply some T-nuts and 2" screws to attach the mount to the plywood firewall.

    I initially placed the radial mount plate onto one of the plywood formers and outlined the outer mounting holes and inner larger hole with a black felt-tip pen. The second, identical size, former was then glued to the first former with CA for added strength. The T-nuts were then mounted before gluing the former in the fuselage with 5-minute epoxy. I used a Dremel tool to widen the inner hole to match the black pen line.

    I used the discarded plywood pieces to strengthen the fuselage.

    The firewall former, which is pre-cut to a perfect shape by the manufacturer, is then glued in place using 5-minute epoxy. I used the discarded plywood pieces, that originally held the aileron servo tunnel strings in place, to strengthen the fuselage in four places. The AXI 4120 motor has incredible power, so care should be taken to support the fuselage properly.

    The AXI 4120 fit perfectly. The power of this 350+ watt motor will make this plane rock!

    Wing Mounting:

    The removable wing is held securely by a metal rod.

    The wing is mounted using a metal support rod that is secured on one end by a machine screw and the other end by a metal screw. It can be disassembled by removing the machine screw. One end of the metal rod has a tapped hole to receive the machine screw through the wing support wood.

    My wing was built wrong and the guiding hole for the machine screw was not in the correct spot. I simply drilled a new hole with my Dremel tool. This is common on early versions sent out for review.

    The rear of the wing is held by wooden dowels that stick through a sleeve pre-built into the fuselage. There was a slight wobble when the wing was fully installed so I drilled holes into the dowels and secured each of them with a toothpick. With the added rear wing support, I could pick up my plane and shake it now without any wobble. This is needed for the abuse it will take in 3D flying.

    Flight Pack:

    The power for my AXI setup comes from the new lightweight 15C 2AH Kokam cells. I'll use two 2-cell packs in series for a 4s configuration that can deliver 30 amps continuous at a capacity of 2000 mAh. I can also get peak burst current up to 40 amps when needed.

    The two packs are easily connected in series using the Kokam Series Connector Module cut down from 5 plugs to 2 plugs. The series connector joins the 2-cell packs together as a single 4-cell pack.

    Finishing the ARF Model:

    My Fun World EP uses an FMA M5 receiver for a full-strength, double-conversion, rock-solid signal that weighs only 0.3oz. To hide the antenna inside, and keep it from flopping around in 3D maneuvers, I ran the wire inside a tube and mounted it inside the fuselage. The extra wire length is coiled around the supplied plastic bobbin.

    The photos above show my component layout for the M5 receiver, antenna tube, 6v UBEC, and ESC. The plywood tray is in the stock position and will hold my two 2-cell Lithium packs. The ESC Dean's Ultra plug routes through the center plywood opening.

    The canopy is mounted stock. It had pre-drilled holes in the plastic for the supplied screws and rubber grommets. For good luck (or superstition) I usually test fly my new plane before adding a pilot.

    I love the plug-n-play aspect of using a Tower Hobbies System 3000 Switch Harness whenever I use a UBEC to replace the receiver battery. The On/Off switch plugs inline between the UBEC 6v output and the receiver battery connector. The added safety of keeping the motor and servos disabled after plugging the flight pack into the ESC is a great convenience. When the 5v is removed from the receiver in a system that uses an Opto-isolated ESC, there is no signal going to the throttle channel so the ESC keeps the motor disabled. The Opto-isolated ESC needs power from the receiver side to run before enabling the motor. This is a key difference from a normal ESC.

    That being said, it should never be used as a complete safety system. Whenever the battery is connected to the ESC, always treat the power system as enabled by keeping the prop clear of all objects.

    The layout of my FunWorld EP components followed the manual design.

    My component layout followed the suggestions in the manual. Although my motor extended out beyond the example in the manual, my lighter Lithium packs would help offset most of the difference. I ended up adding a quarter coin to each side of the aft end of the fuselage. The two quarters weigh about 0.6oz. I also moved the two battery packs aft an inch until the rear pack touched the M5 receiver.

    My finished model, less decals, was RTF at 52.5oz (3.3lb) using the 4-cell Kokam 2AH pack, AXI 4120 motor, and APC 14x7 e-prop drawing 38amps at full throttle.

    I had an opportunity to maiden the Fun World EP myself on a Friday night before a local R/C show started the following day. I'm glad I did because it flew fantastically! I was very happy with both the low speed response and the incredible power from the AXI motor. I was able to trim the plane with only a few clicks of aileron and rudder correction. The winds were too great to fly on Saturday during the R/C event so we didn't get another chance to fly it until the following week.

    On our next set of flight tests, the plane again flew incredibly light, with awesome control and power! It will hover at 1/3 throttle. In fact, I never tried full power as it wasn't needed. I could fly down the field runway very slowly about 6' off the deck while rolling, or have strong vertical runs at only 1/2 to 3/4 throttle!

    I added several quarters to the aft-end of the fuselage for better balance and later moved my two Lithium packs about an inch aft. The battery packs were as far back as they could go without further modifications. The rear pack was now touching my M5 receiver.

    The prop ground clearance is minimal so you do cut some grass on take-off. On my first landing, it was so incredibly slow that my elevator offset of 45 degrees caught the right tip on the grass and broke. A simple CA fix, and I was ready to fly again in seconds. I ended up swapping the wheels for a slightly larger set. Alternatively, you can reduce the prop size to 13", or mount the main gear on a block, or simply bend a new main gear. The goal here is to keep the 14" prop for awesome power when needed.

    The Fun World EP is
    now fully-dressed
    and ready for test flying.

    Here is World Models' Fun World EP ready-to-fly with the decals applied. The in-flight photos were taken after the maiden voyage on a different day in calmer conditions. While across the street from work, we tried to take-off in a short cement area that went straight into some tall uncut grass. Just as the plane lifted, the elevator tabs on each end caught the grass and broke backwards. We continued the flight as the performance seemed unaffected.

    The AXI-fied Fun World 3D has incredible power when needed.

    I repaired the elevator tabs for the video on the following day and added some flat carbon fiber rods along the outside of each elevator end, and I still needed a bit more weight in the tail for good hovering. It may also need a slight thrust angle change, but I'll be flying this model all summer long so I can slowly dial-in the right mix for awesome 3D performance!

    Thrust angle correction and CG changes need to be dialed in for good 3D performance.

    The Fun World EP and AXI power system both provide an incredible dynamic range of performance. You can pull out of a hover and accelerate vertically, or perform slow, powerful "in your face" aerobatics. The review movie shows some examples.

    The Fun World EP offers a great value for a pre-built ARF design. It has about 1/2 the wing area of my larger Graupner ShowFlyer 3D plane but weighs less than 1/2 the weight, so I knew it would be a winner with the powerful AXI 4120/14 power system. I'm very fond of this mid-size design for an easy lunchtime break, or just down the street flying without being twitchy in the wind.

    The Fun World EP has excellent flying orientation with the dual covering scheme. My AXI-fied setup can hover at 1/3 throttle and pull up into an accelerating climb. At a flying weight of only 3.3 lbs...it really rocks! It can also slow down to a crawl without stalling. This wide envelope of flight performance makes the plane an excellent choice for intermediate or advanced pilots.

    Note that we didn't have time to set the proper thrust angle and balance for good hovering in the video. The torque from the 14x7 prop was evident and the CG still needs to be moved a bit aft. Overall, I am very impressed with the plane and the power system. The lightweight design combined with a huge wing area allows for closer and slower maneuvers to be performed with greater confidence. I'll be practicing with my Fun World EP all summer long!

    The World Models Manufacturing Co., LTD.
    Unit 23-24, 10/F., Kowloon Bay Industrial Centre
    15 Wang Hoi Road
    Kowloon Bay, Kowloon, Hong Kong

    T: (852) 2707-9783
    F: (852) 2798-0728

    AXI Power system
    5614 Franklin Pike Cr.
    Brentwood, TN 37027
    (615) 373-1444

    FMA Direct
    Kokam 2AH Packs at FMA Direct

    5716A Industry Lane
    Frederick, MD 21704
    (800) 343-2934
    Tech/Service: (301) 668-4280

    Kool Flight Systems
    355 Sunderland Circle
    Fayetteville, GA 30215
    (770) 716-7578

    Comments on RCU Review: World Models Fun World EP

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    The comments, observations and conclusions made in this review are solely with respect to the particular item the editor reviewed and may not apply generally to similar products by the manufacturer. We cannot be responsible for any manufacturer defects in workmanship or other deficiencies in products like the one featured in the review.

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