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Oct 09, 2002, 01:51 PM
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Paul Willenborg's Avatar
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RFB Fantrainer 600 electric conversion

Some longtime members here will remember previous threads about electrifying my RFB Fantrainer 600 design. In the past I've been pretty negative about the idea. The TD.049 glow powered model had stunning performance for a scale model. I could not see any way to do an electric conversion that wouldn't be a lot heavier and probably less powerful.

But times there are small Mega brushless motors that barely weigh more than a speed 400 and CP1300 cells. Also, the DEAF fly-in was rapidly approaching, I had crashed my Skyray, and really needed something new and exciting. So I vacuumed the dust off my Fantrainer and got to work.

Here's a picture of the plane for those not familiar with it. It's driven by a shrouded prop 4.25" in diameter.
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Oct 09, 2002, 01:53 PM
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The real plane is quite unusual- it is one of very few full-size designs powered by a ducted fan! The fan has a five bladed rotor and is powered by a small turboshaft engine. The intent was an advanced trainer that would provide jet-like performance and flight behavior at a lower cost.

A picture of the underside, note towhook location.
Oct 09, 2002, 01:58 PM
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The first step was to draw a line around the TD's motor mount on the firewall. Then I removed the motor and fuel tank. I was afraid that drilling the big hole I needed in the firewall would be a real chore, but it turned out to be simple. I used a 12" long " brad point drill bit to make a series of holes inside the marked circle. The brad point bits cut clean holes and do not wander so they are perfect for this. I cut the wood between the holes with a clipper and knife. Once the center was punched out the edges were smoothed with a dremel sanding drum- it was fairly easy to get the dremel in through the rear of the duct. In twenty minutes the firewall was ready for the electric motor mount, and the airplane and I were covered with sawdust.
Oct 09, 2002, 02:02 PM
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To get the prop far enough into the duct the motor had to be mounted through the original firewall. The mount is a section of Estes rocket tubing (BT-55) a little longer than the motor. A circular firewall was made from 1/8" birch plywood and CA'd into the end of the tube. There are vent holes in the firewall that align with the holes in the motor case. The motor was installed in the mount before gluing it into the fuselage. Four small balsa supports are glued to the rear of the motor and the tube to prevent whipping. The motor is placed in location, the prop is mounted, and the mount is centered by shimming the prop tips with thin strips of thick paper. The tube is then glued into the firewall with thick CA.

Test fits had revealed that the original motor mount was slightly off center so the hole had to be enlarged. This left a gap at the top of the tube. I decided to leave it open to aid fuselage ventilation. A few small wedges of hard balsa were pushed into the gap and glued to the tube and firewall for extra support. The prop was attached with a socket head bolt for easy removal.
Last edited by Paul Willenborg; Oct 09, 2002 at 02:11 PM.
Oct 09, 2002, 02:09 PM
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I decided on a slanted battery tray for easy access and the hope that the battery will depart gracefully in the event of a sudden stop. The bottom is 3/32" hard balsa with 1/16" sides. There is also a piece of trailing edge stock at the upper end. The bottom was trimmed to fit tightly against the rear former. New cross pieces were added at the other two formers so the tray is firmly supported at three spots. A small piece of velcro on the tray locates the battery, and the black velcro strap holds them down. The top section of one former was removed, and another was trimmed to allow the battery to slide in easily.

All the original servos (Futaba S-133's) were replaced with lighter ones- Hitec HS-60's on aileron and elevator, HS-55 on rudder. The aileron servo had to moved to create battery space. Fortunately the aileron linkage allowed it to just be rotated up 90 degrees.
Oct 09, 2002, 02:15 PM
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Controller is placed in the previous tank location, a little wire wrangling and it's done!
Oct 09, 2002, 02:22 PM
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The important numbers:

weight- 34 oz. with 10 x CP1300 pack (up from 22 oz. glow)
wing loading- 25 oz./sq.ft.
power- 20A, 237Watts, 21,800 rpm (after 30 second run)
powerloading 110+ watts/pound
prop- Cox black nylon three blade 5 x 3.5 pusher cut down to 4.25" diameter.
motor- Mega 16/15/4, Jeti controller

The result: Wheeeeeeeeeeeeeeeee!!!!! Better than I dared to hope!

It's fast, it's got a great climb rate, and still slows down just fine. Speed is better than the glow version which maxed out at about 20K rpm, and that was only when the temperamental TD worked just right. The original model
held a line much better than the typical 1/2A model, the electric version is big improvement over that. With the added weight the Fantrainer flies like it is on rails, even in gusty wind. Stall speed is still quite low with a very benign break.

I entered it in the scale competition at DEAF. It placed third or fourth in the static judging (out of five) but won the contest due to excellent flying by Ezoner ThomasB. They allowed designated pilots so I designated Tom and he put on a pattern performance in high winds that left the other planes struggling to fly.

If you built one of these, but like me just got too annoyed by 1/2A motors to fly it any more, do the conversion!

If you are intersted in building one, let me know, I'm considering redrawing the plans as a pure electric. This would allow a simpler and cleaner motor mount than the conversion.

Oct 09, 2002, 02:23 PM
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Great pic's. I heard from a friend that was at DEAF, that this thing was FAST!!
You've given me some ideas on servo mounting that may help in my mini bobcat.

Thanks, looks cool and fast.

Oct 09, 2002, 04:05 PM
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Way to go Paul - sure glad to see it works. A kit in the works?!?!

Fly Fast! Mark
Oct 09, 2002, 05:11 PM
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Mucksmear's Avatar
Thanks for sharing all this Paul,

I would be very interested in building one of these.

Where do I order plans from (I realize at this time the plans are for the .49 motor). If I read your initial post correctly, this is YOUR design?

Oct 09, 2002, 06:50 PM
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Hi Paul, I built a couple of the glow versions, looks like the E-version is just a good. Do you think there could be a rotor instead of the cut down cox prop? I know it is big for a fan rotor, maybe a home made one? I know it flies well with the prop from the glow ones I built, was just wondering. Also did you ever try it with one of the newer 074 norvels?
Oct 09, 2002, 06:58 PM
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Great to see paul, Well done.

I still have an origonal one, weights now about 25oz after one repair and some fuel soaking.

Brilliant flyer with a great turn of speed (no throttle and enough fuel for 8 minutes flying!). It was one of the most enjoyable models I have flown and is what got me started in DF models (I moved from that to a JHH 91 powered mirage!)

Had started to build another one some time ago with the intent of installing a 480 race motor and see how that went, but gave up on the idea a while ago as other projects took my interest.

If you are making modified plans with the electric conversion in mind I would certainly be interested in obtaining a copy and would strongly suggest others, particularly those new to EDF to do the same.
Oct 09, 2002, 08:06 PM
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Hi Paul, My friend ordered the plans and I built two. I used ace foam wings & glassed them. Both planes are still like new from never having flown. The reason is not being able to start the engines without having the props loosen and fly off. We were both waiting for the day to get opposite rotating cranks for the T.D.'s. But now I think The problem is solved. I thought of doing this, thanks for doing the hard part!!! Maybe they will fly now.
Oct 10, 2002, 08:56 AM
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Guys, this thing is one heck of a good flying model. It grooves like it is on rails, is highly responsive and does not do anything you don't tell it to do. This was the most fun I have had flying in quite a while.

The Fantrainer was doing about 90-100 or so and has loads of vertical performance.

One aerobatic advantage that the Fantrainer has over many EDF models is that the rudder is in the eflux of the fan. This little guy can do perfect stall turns, aided by a tiny blip of power as the model slows to a near stop....

Dave, I would be amazed if you could find any kind of impeller that diameter that would work better than the cut down Cox three bladed prop. It was REALLY moving!

For those that don't know, the plans are available from Model Airplane News. They can be found on line at:

One side note: Paul sets his models up with surgical precision and the results pay off. Perfect hinging, clean linkage and accuracy of construction and rigging are key to this kind of superior handling and performance..
Oct 10, 2002, 09:29 AM
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Hi Paul

I built one from the original plans when you first released them. Still have the plan as this is still my all time fav model barr none!!!

I always wanted to convert one to E power, but until now none of the motors had enough power or if they did, were cheap enough for me to buy.

I would love to see a redrawn plan for a electric version. Thank you for putting this up on the Zone!


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