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Electrifying A Junior 60

A Cheapskate Needs Your Help.

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Mike Etheridge 107/01/2018 16:42:56
1406 forum posts
394 photos

I do have a complete plan of the KK / Flair 1955 junior 60 and a plan of the Ben Buckle 1946 Junior 60 fuselage. if you have any problems with the computerised copies from Mc G 6969, I can get plan copies made if required David?

Mike T07/01/2018 16:43:30
319 forum posts
25 photos

I'd use meths to degrease, it will dissolve the methanol and oil better than petrol and certainly wont stink as much!

A tip I got many years ago was to mix a paste of meths and talcum powder, then slather it on the fuel soaked parts. The idea is that the meths dissolves the oil and draws it into the talc as it evaporates. After a day or so, the talc will be full of oil and you scrape it off and clean up with meths. Repeat as necessary. I've done this a few times and it does work. However on a badly rotted airframe, you are probably better off putting in new wood!

kc07/01/2018 17:02:37
5444 forum posts
161 photos

You just plug a memory stick into a USB socket of your computer, note what drive name it is given and then when you open the file from Outerzone etc and select to save the file onto the drive of the same name as the memory stick.( likely to be drive E if the computer has only 1 hard disc and a DVD drive)

David Davis10/01/2018 09:19:22
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2860 forum posts
480 photos

I got the plan printed yesterday and it was nice to be re-acquainted with it, even if it's not quite the same plan that came with the Flair kit. It's a single channel plan but the fuselage is much the same. It cost me less than 15€ to have the Junior 60 plan, a much larger 40 sized pattern ship plan and a copy of the old Balsacraft Blenheim plan printed. 15€ is the equivalent of £13.26 Sterling or $17.92 US. I thought that that was pretty reasonable.

I have built a box for the battery and will have to extend the lower nose blocks by 1/4"-1/2" (6-12mm) in order to hide the battery box. The alternative would have been to use 2300mAh LiPos instead of the 3300 mAh Lipos I intend to use to give extended flying times. My aim here is not to reproduce an original Junior 60 but to use the model as a basic trainer capable of twenty minute flight times. It may end up looking like one of those Merlin engined Bf 109s! I could cut a hole in the rear former and push the box further to the rear but I encased the rear undercarriage legs in a sandwich of three pieces of plywood and it would be difficult to remove the sandwich without damaging any thing. Besides I need as much nose weight as I can get. I'll post some pictures as soon as the nose structure is complete.

I plan to bolt the motor to a piece of 3mm ply which will itself be firmly glued to the balsa nose blocks. I am undecided whether to incorporate side thrust and down thrust as this could be adjusted with washers. What do the cogoscenti think?

Finally I'm going to re-cover the tail surfaces in Orange Solartex to match the wing. I realise that a "Vintage" colour would look better by showing off the structure of the model but the wing is already covered in "solid" orange and I have no intention of stripping away perfectly sound covering and replacing it with something prettier. I have plenty of Orange Solartex in stock but I've also got sufficient black or dark blue to cover the fuselage. Orange is a highly visible colour of course which is why life-rafts are orange, but would a different coloured fuselage aid orientation?

David Davis16/01/2018 11:33:27
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2860 forum posts
480 photos

My Bull-Nosed Junior 60!

I've built the battery box, and added the nose blocks and motor mounting plate. Further sanding will be required on the nose section and I still need to build the undercarriage and fit an undercarriage plate, but I'm getting there. The propeller is an 11x4 Airflow wooden propeller and is fitted just for show. I have an analogue ammeter and I intend to solder XT 60 terminals to it to check current consumption.

I have also tidied the bench a bit! Note the club trainers and sports models in the background.

junior 60 nose (1).jpg

junior 60 nose (2).jpg

David Davis19/01/2018 05:45:32
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2860 forum posts
480 photos

Soldering has never been my strong point, perhaps that's why I've never really taken to electric power but over the last few days I've had to alter the terminals on the ammeter to take XT60 connectors and to put XT 60s on a couple of batteries I had skulling about. I had always been advised not to twist the bare ends of exposed wires together because oil from your finger tips could contaminate the wires and make soldering difficult. I hit on an answer to this. Use a piece of spare insulation, wrap that round the exposed end, then twist the wires together. Having had to solder up a total of four connectors, two on LiPos and two on the ammeter, my soldering skills have come on apace!

I spent a merry half hour yesterday testing the current consumption of the motor while using different propellers. With an i/c wooden 11x4 it drew 25 amps, with an electric 11x5.5 it drew about 28 amps and with a 12x6 it drew over 35 amps at full power. I even fitted a 10x6 electric three blader to it for a laugh, that drew 35 amps too! The photo shows the J60 carcass clamped to my Workmate and the motor throttled back a bit.

Unfortunately my hithertoo very reliable charger, a Vislero A6, now refuses to recognise a LiPo!

twisting wires.jpg

test rig.jpg

test rig reverse.jpg

propeller testing.jpg

Geoff Sleath19/01/2018 11:51:48
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2556 forum posts
197 photos

I've been twisting wires together for soldering for something like 65 years and never had a problem with the wire not tinning properly. Perhaps, like I was told my mother had, I have dry skin but everyone does it without problems AFAIK.

Analogue meters are fine (in fact I have an unused one still in its box like yours) but so-called Watt meters are better because they measure and display both current and voltage. Plus some, like the HK one I use regularly, also check LiPo cell states and they're much cheaper than the Astroflight one I bought years ago. From your experiments with current draw, I'd use the 12x6 prop (in my personal experience a 12x6 seems to be the prop of choice very often!)

There's something odd about your charger problems. The easiest way to solve it is to try your LiPo on a known working charger, preferably one that can measure internal resistance (IR). If the IR/cell is significantly > 10 milliohms then the battery is toast. Then to check your charger try it with a known good LiPo.

Geoff

David Davis19/01/2018 12:22:02
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2860 forum posts
480 photos

I've tried four different LiPos on the charger Geoff with the same result.

Geoff Sleath19/01/2018 12:45:57
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2556 forum posts
197 photos

Then perhaps it's time to invest in a new charger, David. You're unfortunate because in my experience the ones I've had have been fine for years of regular use - probably not a good thing to write

I'm not familiar with the Vislero chargers at all. I have an old charger which does cope with LiPos but has no balance feature (Constellation or something, can't remember) but I never use it now even though it still works as well as it ever did. I have a Graupner Ultramat 16 I've had a while and used (and still use) a lot without problems but my favourite is an iCharger 308 Duo which was expensive but excellent. I can recommend them both.

Geoff

David Davis19/01/2018 12:49:22
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2860 forum posts
480 photos

Mine must be at least nine years old so it doesn't really owe me anything.

David Davis11/03/2018 19:14:01
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2860 forum posts
480 photos

It's been Tangoed!

j60 electrified (2).jpg

British aeromodellers will understand the reference! I was not going to bore all of you accomplished craftsmen with pictures of the re-covering of the fuselage and tailplane in Solartex and I will not apologise to fundamentalists who insist that I should have used a translucent colour. The wing and fuselage were already covered in Orange Solartex before I sarted the restoraration, and I intend to use the model as a basic trainer with nervous elderly beginners so orange is a very practical colour for that purpose. Besides I have plenty of Orange Solartex and it matches my flying suit!

be2e.jpg

I may well add some lettering and extra decoration once it's flown successfully.

The model is powered by a French-made electric motor and uses a 40 Amp speed controller from a late WOT 4 Foam-E ARTF. I have six suitable LiPos, all 3S and ranging from 3000 to 4000 mAh. They will live in a box under the motor. With the 11x5 wooden prop fitted the motor draws 28 amps. I have not weighed the model because my scales stopped working but the when I first built the model it weighed exactly 4.75lbs exactly the weight specified on the kit box lid. Assuming it still weighs the same, that means that this combination produces 65 watts per lb. This should be enough. If not I have larger propellers which will do the trick. I intended to fly it today but it was too windy.

I have been rationalising the workshop/boiler room. An extra set of metal shelves has been assembled and all of the shelving units have been screwed to the wall and to each other. Lots of stuff has now been stowed on these shelves.

j60 electrified (3).jpg

Half a dozen trainers and sports model fuselages hang from the east wall as you can see. I've also built a set of wing supports out of 2x1 (25mmx50mm) timber and shelving brackets which you can just see to the right of the Junior 60 in the first picture. The old ARTF Boxes are used to store balsa wood!

j60 electrified (1).jpg

David Davis14/03/2018 06:51:46
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2860 forum posts
480 photos

Test-flew it yesterday. It needs nose weight and there is wash-in in the starboard wing. I have left the wing clamped in a wash-out position overnight and have applied a little heat to the top covering. We'll see how successful that is.

The motor proved to have plenty of power even with an 11x5 prop fitted and despite a less than perfect landing the undercarriage solder held!

Excellent flying day forecast here in Central France and I've another two models to maiden.

Nigel R14/03/2018 17:45:42
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1168 forum posts
259 photos

I must admit, that is remarkable tenacity shown on the restoration job. I would probably have used it for firelighters and remade from scratch. And some excellent thrift on display, too.

It could only be better if it was fluorescent!

David Davis14/03/2018 17:52:21
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2860 forum posts
480 photos
Posted by Nigel R on 14/03/2018 17:45:42:

I must admit, that is remarkable tenacity shown on the restoration job. I would probably have used it for firelighters and remade from scratch. And some excellent thrift on display, too.

It could only be better if it was fluorescent!

I'm of the "make do and mend" generation.laugh

Two flights today. Warped wing is still a problem and motor requires a bit of downthrust and side thrust.

David Davis01/04/2018 18:16:27
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2860 forum posts
480 photos

Incorporated a bit of downthrust and side thrust into the set up this morning and had three ten-minute flights this afternoon. Everything went well but I think I'll increase the downthrust a bit more.


Much though I appreciate the convenience, reliability and cleanliness of electric flight, I have an Enya 19X and an Irvine 20 looking accusingly at me!

Edited By David Davis on 01/04/2018 18:38:45

David Davis21/04/2018 13:28:38
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2860 forum posts
480 photos

The model has flown on several occasions now but I'm aware of two "challenges" which I'm dealing with little by little.

  1. With a 3300 3S LiPo installed the model displayed all the characteristics of nose-heaviness. It was particularly difficult to control when trying to flair the model for a landing. I have been progressively moving the CG back by using smaller Lipos. I'm currently using a 2200 3S battery but I still lack a little elevator authority on landing approach.
  2. Under power the model climbs so much that it's on the verge of instability unless I add down elevator. If I reduce the power to just over half the throttle-stick travel the model flies nicely. I have added a 1/8" plywood wedge between the motor and the noseblock to increase downthrust and that has improved things. I plan to add a piece of 2mm plywood to increase the downthrust yet further.

A question to those with superior aeronautical knowledge to me. "If I were to fit a smaller propeller, thereby reducing the power of the motor, would this reduce the tendency to climb so violently?"

David Mellor21/04/2018 15:02:32
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642 forum posts
230 photos

I've built and flown an electric J60, and I have another part built.

From what I understand of the J60, the airfoil is essentially a "one speed" deal and that speed tends to be low. If you have a very lightly loaded J60 the "one speed" seems very low indeed and I had comments at the airfield with my first one along the lines "Hmmmm... I'd forgotten they can fly that slow".

 

So, assuming the "one speed" description is roughly right, when you apply power above that speed then the J60 will balloon up (climb violently). So, one answer is to fly it at its own individual 'one speed", which in turn depends on how light or heavy yours is.

There are several threads in which people talk about the need to "beef up" the centre of the wing to cope with higher g-force and more speed. However, the old-hands will point out that is unnecessary because they aren't intended to handle those forces or go fast or cope with more than about 200 Watts. A lightly built, low-powered, slow J60 will not "clap its wings" if flown slow and gently with just enough power to keep her up.

It isn't really a smaller diameter propeller you need, but a lower pitch (and possibly a smaller diameter as well).

For any chosen (static) thrust of interest, a bigger diameter propeller will always consume less power than smaller diameter propellers of the same pitch.  This is a bit counterintuitive because many people think that increasing prop diameter draws more power - it does, but only because you allow it to also generate a lot more thrust than you may need.  

I'm using a 13 x 4 prop on mine and it just floats along and sips the electrons........

Edited By David Mellor on 21/04/2018 15:12:49

David Mellor21/04/2018 15:50:40
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642 forum posts
230 photos

Here are some photos of my latest electrified J60, not yet finished.

It is a lightweight- it should weigh in at around 40 ounces all-up-flying weight when finished. I am covering it with lightweight doculam and using sewn hinges. So far the canopy is in, and the tail feathers are finished in doculam but the main fuselage is yet to be covered.

It is powered by 2 x 850 mAh 3S batteries in parallel to drive a Turnigy 3536/8 100 kv motor from a 30AESC.  I already had the motor, and the weight at the nose it provides comes in handy to balance it.  

Even though the motor is rated at 430 Watts, it will take an awful lot less than 200 Watts to pull it through the air on a 13 x 4 prop.

 

p1060229.jpgp1060232.jpgp1060231.jpgp1060230.jpgp1060236.jpgp1060233.jpgp1060240.jpgp1060238.jpg

 

Edited By David Mellor on 21/04/2018 15:54:39

David Davis22/04/2018 04:44:28
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2860 forum posts
480 photos

Thank you David for your advice.

My Junior 60 is of course a lot heavier than yours, thirty years old, and an old i/c conversion covered in Solartex. It's also the model I learned to fly on with an Irvine 20 up front! The weight comes in handy in a breeze I've noticed!

I'll try the effect of less pitch on the propeller and I may install another less powerful motor to reduce its climbing tendencies. I have an Emax BL2815/09 which might power it and an Axi 2820/10 which defintely will.

I can control the model but I intend to use it as a basic trainer with ageing novices and they may not be able to co-ordinate the control inputs if the model is climbing rapidly and stalling all of the time.

Don Fry22/04/2018 07:32:54
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2349 forum posts
30 photos

David, David is quite correct. Its a one speed wing. At the proper throttle setting it neither comes down or goes up. If you want to go quicker, do some elevator down trim, increase the throttle, and you get a new, higher, single speed.

But it will balloon coming into wind, and sag turning out of the wind. Goes with the undercambered wing profile.

And they get twitcher as the speed is increased. Cast your mmind back, when I was a boy, I had one of these. It flew right nice as a single channel machine with a worn out 2.5 cc ED RACER diesel chugging along

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