Simprop Prolution 4004 Electric version

Simprop Prolution 4004

Electric Version

 I was lucky enough to get hold of the non electric version of the Simprop Prolution 4004 in the early summer Chedder flying event in June, I was amazed how good this glider really was, either in a light breeze or a 20 mph wing. This glider is a quality soarer for all occasions, so good I thought of fitting a power system to her, Simprop have very carefully already marked out in the moulding where to cut of the unwanted part of the nose to fit the motor. But the prolution is such a good glider I could not bring my self to start cutting a way to fit the electrics, Tony  one of the Ghost squadron team had a damaged fuz of a Powered version of the prolution and said I could have it if I wanted, I said yes right a way and Picked it up at Binham the second of the Ghost Squadron weeks flying holidays. I will go through the repair of the fuz and the fitting of the power system with the problems I encountered on the way.

All the stickers will be removed before painting

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When I first looked at the inside, I thought "what am I thinking", but in the back of my mind this is a very good glider so its worth doing.


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I first rubbed the inside with 80 grit to remove the shine from the glassing so I could lay down some glass matting,and also rub down the outside as well, this can be seen in this picture. I did this by starting with making a card cut out of what I needed to cover in the inside, then using the card jig place it on the glass matting and cut 2 pieces, once done get a plastic bag, it has other uses then carrying things

When I first looked at the inside, I thought "what am I thinking", but in the back of my mind this is a very good glider so its worth doing.

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Stick it down on the table and place the first glass patch that has just been cut out and with brush on skining epoxy, there is others you can use But this is what I had loads of at the time.Then place the second patch on top of the first and brush more epoxy on, now brush some epoxy in the inside the fuz where the matting needs to go.Now peel of the double patch and lay it where it needs to cover, I was suprised how easy this was to do and then with a brush and some more epoxy brush outwards to flatern the edges.

Then with some more epoxy and micro ballons make a paste and rub down and level of to match the outer skin, the keel is still missing to finish of the body rebuild.

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To build to keel up took 115 strips of matting bushing on epoxy on every strip laid, with more rubbing down and with some filler primer, its looking good.

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 The fin had some brake damage on the trailling edge, this time some super glue and rubbing down with some filler primer sorted.

All the stickers have been removed and the fuz was rubbed down with a scourer to remove the top coating to allow paint to take to it. Got some white gloss equipment spray and then t-cut the fuz.


I thought at the begining of this project the fitting and finding the power system was going to be the easiest part of the rebuild, but I was wrong really wrong.I didn't realize when you step up to 4mtr power gliders  and a weight of about 5kgs how segregated you find your self, I searched on the internet for two weeks , see the original power train was a inrunner with a gearbox, I wanted to use a out runner so trying to find a conversion from the in runner trying to get a motor with low amps and slow revs for a 16/8 folding prop and 44mm front end to fit in to the nose.I have tried all local model shops and the glider specalists all with empty results which amazed me, I was thinking how have anyone else got round this problem.Then I started once again to look at glider forums and started to follow the chats between people, and with doing this found a link to a electric motor formular chart, you just fill in the information in the boxes and hit go, and a list of engines that are suitable.

Axi Model Motors

Electric Conversion

Electric Conversion will require translating from German, but will explain completly on the transformation from the soaring version.


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Folding prop 16 x 8 Aero-naut Cam Carbon 44mm Graupner spinnerThese come from Puffin Models

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70amp Brushless speed controller

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Axi 4120/20 Motor

This comes from The Electricwingman

Next day delivery

5200 / 5cell 30C Battery pack


Direct contact Mon -Sat Halo Ping - [email protected]

Please remember they are 6 hours in front of us

Servos are Hitec HS311s, RX is a Futaba R6014HSand a Eneloop 2500-4.8v

The reason for the 14 channel rx is because I require 9 channels.

The next is a trip to John Greenfields workshop for working out where to place the Battery's,servos and tray and rx, and try and sort the problem with fitting the motor.

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The night was very eventfull and loads was sorted out, the best news was the motor fits after all the worries of the motor shaft not to be long enough for the folding prop and spinner, a 7channel receiver will be used to get round this I will be joining the airbrakes together and changing one of the servo's for a digital one to allow us to set the servo to match the standard servo.

The battery will be fitted behind the cockpit fitted to a bed that will be made shortly and shown in detail.

Now to fit the servo tray and a supporting former along with the battery tray, I will start with the former because the control cable for the elevator is already fitted, this says where the servo tray and former will be fitted.Using some flexi card create the former, and once happy with it, use the card former jig to cut out the real former out of 1/8 ply sheet.

The former had a clearance hole cut out of it for the control wires to the servos, thena servo tray cut out and placed on a  mm  6mm square hardwood shelf stuck to the former and at the front of the servo tray is 9mm triangle balsa.The tray behind the former is the base for the battery tray that will be screwed and glued down.

ghtBattery bed bad from 1/8 ply with some stiffining struts underneath, to the right is the locking stop for the battery tray to slide in to, and a nutsert fitted at the other end to lock the tray down.I have still to cut out some lightning holes out to save some wei

Speed controller now fitted just waiting for the two batteries one being a enloop pack for the rx and servo's and the other a  5 cell Onbo  5000 35c motor pack. 

hey have arrived from Onbo now all systems are go, have also bought two 2000mA enloop 4.8v rx packs, the reason I bought two was because there might be required as extra ballest and also give me a longer flight time.And picked up the 14 channel futaba rx from my local model shop, before going a round to John's to setup the Prollution and do the final fit.

They have arrived from Onbo now all systems are go, have also bought two 2000mA enloop 4.8v rx packs, the reason I bought two was because there might be required as extra ballest and also give me a longer flight time.And picked up the 14 channel futaba rx from my local model shop, before going a round to John's to setup the Prollution and do the final fit.

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Had to start the night of properly before getting down to work, started of fitting the receiver and setting up all the wing servo's then the rudder and elevator, had some slack to take up on the closed loop system on the rudder to reduce,when doing the c of g found that both rx batteries were required so they also need to be fitted permanently and a Y lead added between the batteries and the rx.One of the rudder hinges needed replacing because it become to loose and thanks to the internet to find the information on setting up the slow start on the speed controller.

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Once found the C of G the main power battery for the motor with putting a stop behind and in front of the battery to stop it slide from the position and then velcro holds it on top of the battery board.

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The two batteries held down with tyraps but each battery pack has double sided velcro wrapped a round them to hold them against each other, ply boards were glued down with 5 minute epoxy and micro ballons, these ply boards are the bases for velcro to seat all the equipment.The spare board is for the vario, and of course the rx is on velcro as well and two snake tubes wrapped with masking tape and glued with epoxy ans micro ballons to make the glue thicker so it doesn't run, these are for the two rx aerial's.

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All fitted ready to go

After flying with the battery tray I made found it was not practical, to remove every time to change the batteries over each time. Tony has the same glider as me and showed me what he made , so here is my version of the battery box which is more friendly to use.

The box stays in the plane just open the velcro each time to change the battery, I made lighting holes to remove some of the extra weight. Not that it matters to much as the battery box is on the C/G.

Today was also a electrical day with charging the new batteries and I had a broken 3 way switch on my Transmitter, this has not been required till now my first 3 way switch is for the motor at two speeds and the new replaced one is for the vario.

All ready now for the test flights.

The days here after all the hard work put into getting the Prolution repaired and ready for this day to get her back in to the air, it's hard to believe that 20 minutes before we had a bad raining most of the morning.

A few last checks and a range test before the maiden flight A dolly was used on take off and the soft start was nice to have and once the switch went to the second postion and the motor went to full power the Prolution took of with ease.

Once in the air John proved that the flight under power went straight with hands off, with a very good climb rate with just a touch on the elevator it was all good.

Thanks to the Electricwingman getting it right with the Axi motor the climb rate was very good and with the Onbo batteries I got 6 to 7 climbs to 1000ft from 30ft and when I landed we checked the battery and found there was still 30% power still left so I was more then satisfied

I have one little problem where the rudder again , where the rudder hinge broke so some new ones will be made from a more flexible material that will be nylon 66 sheet.
Well this brings this page to a end, but what this has taught me is never turn down a broken glass ship because they can be repaired.

A big thanks to

John Greenfield for all his advice and help

Electricwingman for his choice of motors

Puffin Models for the spinner assembly

Gliders uk for the folding props

Onbo for the batteries

Mainly Models for Rx and servo's