Greg Covey

The tail support kit comes in its own bag with the instruction number on it from the manual. The tail already has pre-installed metal sleeves so you only need to cut away the openings. The plastic-coated steel wire supports all four quadrants.

Greg Covey

The linkage was very easy to install. All the parts for the rudder and elevator linkages came in their own bags. The wooden dowels and metal rods were pre-cut and pre-bent for easy assembly. The pre-drilled holes in the control rudder and elevator halves were marked with pinholes through the covering. This provided perfect alignment for the control horns.

My only change from stock parts was to replace the supplied quick links with Dubro E-Z links. The E-Z links cannot slip as the metal rod is bent 90 degrees through the servo arm and securely held in place. There is no need to have both ends of the linkages adjustable.

I ran the antenna wire from my Futaba R127DF 7-channel receiver into a plastic tube (not supplied) and taped it into the rear of the fuselage inside.

Greg Covey

To power the AXI 5320 motor, I am using two BalancePro HD packs in series. The 6s and 4s packs are combined to create a 10s pack with a 3200mAh capacity. The diagram/photo shows the hook-up for a single 6s BalancePro HD pack using the Discharge Protection Module (DPM) and the optional LED/Spkr module. The DPM also connects in-line with the receiver throttle channel to ESC signal. This allows the DPM to monitor the throttle setting and pulse it if any one of the cells in the pack goes below the danger threadhold that can damage the pack.

For my 10s setup, the DPMs simply daisy-chain together by connecting the power output lines in series and routing the receiver throttle channel through one DPM and then the other DPM. The last DPM in the daisy-chain gets connected to the ESC.

For my servo and receiver power, I'm using a [link=http://www.fmadirect.com/Detail.htm?item=2004&section=58]Power Force Regulator[/link] from FMA Direct set to 6v. This device eliminates the need to keep a seperate receiver pack charged, has a fail-safe On/Off switch, and can handle the higher current needed for my heavy duty servos. The On/Off switch has a flush slide switch that I mounted on the side of the fuselage with the supplied plate and hardware. I powered the regulator from the DPM connected to the 4s BalancePro HD pack. Note that this pack must be connected to the ground side of the wiring and the other 6s pack is wired in series to power the Jeti 90-amp ESC. Optionally, you can also supply the Power Force regulator with a separate 2s, 3s, or 4s Lithium pack or 5-12 cell NiCd/MiMH pack.

Greg Covey

After first testing my motor direction without a prop attached, I installed the APC 20x11 e-prop using the spacer made by my friend, Paul Weigand. Although I couldn't find any 12mm hubs, I thought it would look nice if I drilled out a Higley Safety Hub to fit on the end of the prop shaft.

Greg Covey

The instructions for the pilot tray were quite sparse so I decided to make some simple modifications to better suit my electric conversion. I wanted the pilot tray to be easily removeable to better access the batteries for recharging. I cut one of the two trays so that it could slide in and out. I then used the cut away sections to strengthen the assembly underneith. The trays were glued with 5-minute Z-poxy and also screwed into the channel of the main hatch door.

Since I plan to test fly the Cub tomorrow, I will use the stock screws to hold the pilot tray in position. The tray rests on a channel on the inside of the left window area. The rubber pilot is pre-painted and comes with a double-sided sticky foam pad to hold him on the tray. I used some medium CA to help hold the pad to the wooden tray.

Note that the front windshield is held in place with supplied screws and rubber inserts to protect the plastic.

Greg Covey

The windows came in the kit as a single piece for each side and only needed to be cut on one line to separate them. I glued them in place with Pacer POLY ZAP(tm). Designed to work on plastics, delron, polycarbonate, nylon, and rubber...is is ideal for clear canopies and windows. It dries clear and is non-fogging when kicker is not used.

Greg Covey

The wing assembly is straightforward. Two aluminum rods are inserted in the right wing first and held with machine screws in pre-tapped holes. Once the wing is in position, the left side is held by drilling holes into the aluminum rods via the pre-drilled holes in the wing. The left wing half is then held by sheet metal screws. To dissassemble, you remove the machine screws in the right wing half.

jooNorway

Look forward to hear a flight report on this beauty.

Two weeks ago a friend of mine maidened his electric converted 1/4 scale PA18 Cub. It have been flown with an OS120FS for several years, but suddenly he bought a Cyclon 160 and connected it to 10S5000 FlightPower EVO through an Jeti 90 ESC. AUW appr 7,5 kilo. It flew nice already on an 16x8 APC-prop at just 50A on WOT. More power than the OS gave, and still it is not tested with a better prop! It is planned to work as a TUG for our 1/4 scale wintage gliders and there are no doubt it has enough power!

Do you use the 5320/28 or 5320/34? I suppose the /34...

Greg Covey

Hi,

I used an AXI 5320/28 motor. The maiden flight demonstrated so much power that the 20" prop is not needed. I used it because it was all I had at the time. An 18" or 19" prop should work fine.

Greg Covey

I had an opportunity to test fly my Cub over the weekend so I rushed to finish the assembly to make it air worthy.

It was rather funny as I hesitated and squinted at the first part of the large callsign decal. I was about to apply the large decal to the wing, leaving the others for after the maiden flight, when I noticed that the "N" in the plane I.D. was a mirror image. I cut out the center portion of the "N" and then applied the decal. Once applied, I cut the correction from a piece of black sticky-back Monocote trim sheet that I had from a previous project.

I notified Fai Chan of Airborn Models (the U.S. distributor for World Models) and he found that his new stock had the corrected decal. Apparently my model was one of the last from the previous production run.

Greg Covey

The final step of my assembly was to attach the struts and their supports. The design of these struts were very good and proper for a plane this size. All the wing inserts were pre-installed so you only needed to find the pin holes in the covering. My only change after the maiden flight will be to make the attachment to the fuselage a quick release post and pin instead of the supplied screws and locknuts.

The maiden flights were perfect yesterday! I'll post photos and video soon...

Greg Covey

Here are some Ready-To-Fly photos of the J3 Cub. For now, we'll assume an all up weight of about 16lbs. The power system delivers 2500 watts at 68amps for about 156w/lb. Obviously, I have much more power than needed which will be seen on the second video (I made 2 of them) showing slipping and stall turns. For the most part, we used 1/4 to 1/2 throttle and then throttled up to 3/4 or full for various power maneuvers.

Videos and flying shots coming soon...

photos by "Papa" Jeff Ring

Greg Covey

This first video shows that maiden flight of the World Models 1/4 scale J3 Cub. After a slight trim, it flew like a dream in 10-15mph winds. The strong power level allows for easy rolls and loops and the flight times were about 15 minutes with 3200mAh packs.

[link=http://www.gregcovey.com/reviews/WMJ3Cub1.wmv]J3 Cub Video 1[/link] (10meg)

Greg Covey

photos by "Papa" Jeff Ring

Greg Covey

The second video of the J3 Cub shows some slipping into landing approaches at an angle and some stall turns. Next, I'll show a few modifications I made for easy access and setup.

[link=http://www.gregcovey.com/reviews/WMJ3Cub2.wmv]J3 Cub Video 2[/link] (9meg)

Greg Covey

After the maiden flights, I finally got a change to add the tail decals.

Greg Covey

After the initial flights, I decided that the stock foam tailwheel was a bit weak for a Cub this size. I replaced the stock tailwheel with a Dubro #150TW 1-1/2" solid rubber tailwheel for quarter scale planes.

algutkin

My Feedback: (1)

Hey Greg,

How ya doin?

Anyhow this is a nice build thread, notice how nobody screwed it up with off subject questions. I have an on subject question. Did you have to modify the the tail wheel axle or the replacement wheel? I tried to replace the wheel on another plane and discovered that the stock axle was much smaller than the hole in the replacement wheel. What a pain in the butt trying to fix it and stop the wobble.

Al

Greg Covey

Hi Al,

The replacement Dubro tailwheel had a slightly larger axle hole diameter but it was not sloppy so no drilling was needed.

I also made these other modifications.
[ul][*] The pilot tray was more easily removeable by creating latches from cut off servo arms.[*] The strut screw and nut holding it to the fuselage brace was replaced with a hitch pin clip from Home Depot and a short brass screw with a hole drilled in it to act as a hitch pin.
[/ul]

algutkin

My Feedback: (1)

Hey Greg, what super ideas, got any more?

Al

tlnibert

Greg, I just ordered the Cub, do you know if a Zenoah G-38 will fit under the cowl. I'd rather not go electric because of battery cost.

Tom

Greg Covey

Hi Tom,

Sorry, I do not know if the G-38 gas engine will fit. I expect it will in that size plane.

Your concern about battery cost is the number one issue keeping more R/Cers from trying a glow conversion. Perhaps new emerging technologies like A123 and Molicel will prove to be a reasonable trade of more weight for less cost. Time will tell.

tlnibert

A friend was building the GP's Cub for me, but after I saw the cost of batteries, I sold the plane to him and ordered from Airborne. I've called Airborne several times to see if they received the order, but haven't heard from them. It'll probably get the G-38, I'm tired of cleaning goo from my planes.
Thanks for the reply
Tom

whizzard

My Feedback: (2)

Hi all, I'm Tom's friend that bought his GP Cub and I still intend to fly it on lipoly's.

I just think the E-Flight 45 size motor that Tom picked out for the GP Cub is going to be able to fly it on 3s 11.1V.

If not I would like to put the 3s 11.1V in series and try flying it at 22.2V but the motor seams to be happier with a max of 18.4V of a 5s battery, problem is that those batteries are expensive.

Any one want to check Motor Calc and see if I could still fly on 22.2V if I don't fly full throttle all the time? I hope it will fly very "Cub like" at half throttle with the E-Flight 45.

I am trying to stay "fuel power" free in my second time in the model airplane hobby.

Bill

Greg Covey

Hi Bill,

If you are refering to the E-flite [link=http://www.horizonhobby.com/Products/Default.aspx?ProdID=EFLM4046A]Power 46 BL Outrunner[/link] motor, then it can produce 800 watts of power on a 5-cell LiPo pack at about 44amps.

Calculate 3.6v per cell under load * 5 cells * 44amps = 800 watts.

For a 7lb plane (estimate of GP .40-size Cub), that provides a top power level of 800w/7lb or 114w/lb which will provide strong aerobatics.

On a 3-cell pack, depending upon prop size, you could get 3.6v * 3 * 55amps (max. burst) = about 600 watts. This provides about 600/7 or 85w/lb of power which will provide good flight performance on a Cub. They key here is to have a good LiPo cell capable of delivering 75amps or more like the PolyQuest 5000mAh cell.

Good luck!