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Motor thrust alignment Junior 60

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Skippers Walker30/05/2020 06:30:47
61 forum posts
14 photos

Hi

I'm currently building a Junior 60 for Electric power. I have a Tornado Thumper 3548/05 Motor (900KV 710w). A 11x8 Prop or similar to be fitted.

Any hints or tips about Side & Down thrust settings would be welcome please?

I only intend to fly the J60 in a traditional gentle climb/glide manner with sensible moderate power application. No aerobatics!

Stay Well

SW

Richard Clark 230/05/2020 07:02:27
292 forum posts

Reduce the incidence on the wing slightly (or increase it on the tailplane, which is easier if you have already completed the fuselage sides) and put the motor level with the nominal centreline of the fuselage.

RC is completely different from free flight (which is at a steady speed with incidences mostly meant for slow landings with a stopped engine, so no downthrust at that time) and without  a moveable elevator.

These changes will be worthwhile. It will still climb with increased throttle but compensate for it with the elevator. Manually, not with a throttle/elevator mixer as that will screw up any 'touch and goes' - open the throttle and it will promptly nose over or dive if it's off the ground.

Bear in mind that "The elevator controls the speed and the throttle controls the height". Many modellers get that backwards

Edited By Richard Clark 2 on 30/05/2020 07:10:19

ken anderson.30/05/2020 07:50:01
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8686 forum posts
808 photos

hello SW,when I built mine I did so as per the flair instructions....and gave the motor 5 degrees of downthrust...when flying the JNR will climb like a goodin with too much power so its a case of get to what height you want feed in a couple of clicks of down trim close the throttle a bit and that's it...fly circuits or whatever until you get bored or a stiff neck....

ken anderson...ne...1..stiff neck dept.

Skippers Walker30/05/2020 08:36:21
61 forum posts
14 photos

Many thanks guys for the response. I'm quite new to the Electric scene but with many a sore finger from flicking reluctant diesels in the past! Now trying to learn a new discipline with a different kind of power unit.

Good advice that I will take to the 'workshop'.

Cheers for now enjoy the summer flying (socially distanced of course)

Chris

Andy4830/05/2020 12:47:27
1545 forum posts
9 photos

If you want to keep your fingers do install a safety plug.

Dwain Dibley.30/05/2020 19:53:03
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1505 forum posts
1487 photos
Posted by Andy48 on 30/05/2020 12:47:27:

If you want to keep your fingers do install a safety plug.

Ditto..... Your finger will stop a diesel but an electric motor will just "Try" harder to chop your finger off. LOL

I just fitted my motor in my j60 with the same setup as IC it behaved OK with minimal throws on rudder elevator, and potter round on very low throttle.

D.D.

gangster30/05/2020 21:43:36
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1030 forum posts
29 photos

That is a lot of motor for a junior 60. You may need after calibrating the esc at 0 and 100% need to limit the throttle end stop to about 40%

brokenenglish30/05/2020 21:55:34
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571 forum posts
30 photos
Posted by Skippers Walker on 30/05/2020 06:30:47:

I only intend to fly the J60 in a traditional gentle climb/glide manner with sensible moderate power application. No aerobatics!

Chris, I apologise for posting one of my videos, but there's a valid reason!
The plane in the video was built exactly as per plan, no downthrust, no sidethrust, no changes whatsoever, and with the intention of flying as you described in your initial post.
If you want to fly as you mention, you don't need to change anything!

The 'instructions" that you've been given above are what's needed (I think!) to fly the J60 like a modern RC "sport" model (touch & goes", etc.). Is that what you want? It's not the impression I got from your initial statement.

Anyway, have a look at the video and, if that's the kind of flying you want, you don't need to change anything!
The J60 has been flying for more than 70 years, including several decades of RC flying, without all these suggested changes and, IMO, for traditional vintage flying, you don't need to change anything at all!

Vintage flying means letting the plane fly almost on its own. Flying "with authority" needs a different type of model.

Personally, I fly my J60 like a J60 and my Wot 4 like a Wot 4. Trying to reverse the roles ruins everything!

Apologies again for the video!

PatMc31/05/2020 00:14:52
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4407 forum posts
530 photos

I refurbished & converted my Flair version Jnr 60 to electric about 8 years ago, the blog is here. The power train was a Keda A36-12L (similar in size weight & kv to yours) battery 3s 2200 mAH, initially prop APC 11x5.5 later changed to a Topflite wood 12x6 ic type which gave a more tractable throttle response that suited the model. My model weighs 3.75 lbs, power at WOT with the 11x5.5 prop was 300W. There's a couple of graphs in the blog showing the climb & glide rate. The glide rate was later improved somewhat by moving the cg back over 1".

When I built the model around 1986 I set 5 degrees down-thrust & zero side thrust.

Reducing the wing incidence is not a good idea as this will also reduce any down thrust by the same amount & cause the model to fly nose high by that angle at any given speed. IMO best to either increase the tailplane incidence (if you must) or better still trim the model with some down elevator for flying in the strongest wind speed you will fly it at & use up trim to bring the elevator to around neutral for light wind conditions.

PS - Read BE's comments after I typed the above & I completely agree regarding there being no reason to change any of the incidence or thrust angles. Elevator trim & throttle control are all that's needed. If I were to build one from scratch now I wouldn't incorporate any down thrust. 

But I still like to throw it around in some aerobatics every now and again when I get bored.  wink 2

 

Edited By PatMc on 31/05/2020 00:29:08

Richard Clark 231/05/2020 03:14:56
292 forum posts

"reducing the wing incidence is not good idea"...…."I fly my J60 like a J60"

Comment such as these miss the entire point. And PatMc promptly added 5 degrees of downthrust when the original didn't have any at all. Though his "no sidethust" is correct to the original.

The original was a free flight model. Under power it flew at a fixed airspeed (the optimum and constant climb rate for the UNCHANGING power available) in a gentle left (usually) turn due to 'torgue' or the corkscrewing propeller wash ("or" because opinions differ on why they turn to the left).

The rudder trim tab was set to turn the plane to the right. This was to 'open up' the left turn under power and hopefully avoid the dreaded power on spiral dive. It had the pleasant side effect of making the plane turn the other way on the glide.

And the high 'decalage' together with the rearward (by rc standards) C of G had the desired effect of a slow 'landing' with no elevators in often far from optimum circumstances. It's not a 'landing', it's a slow as possible uncontrolled crash.

My suggested changes will not affect the flying characteristics at all. They merely make the rc side of it more pleasant WHEN YOU UNKNOWINGLY force the plane into flight attitudes/speeds both high and low a free flight plane could never get into.

BTW: Power choice is a problem. Electric has advantages though the sound is not authentic, two strokes are 'period correct' but sound unpleasant. I use an OS 30 four-stroke, and what's more, a 1970's US made 'Pro Line' radio (the absolute 'tops' at the time but never imported into the UK) modified to 2.4 and only 20 years out of period.

Edited By Richard Clark 2 on 31/05/2020 03:18:22

Edited By Richard Clark 2 on 31/05/2020 03:20:59

brokenenglish31/05/2020 07:05:54
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571 forum posts
30 photos

There are a lot "approximations" in the above post...

"The original was a FF model"... OK, in 1946, but the J60 has been "mainly RC" since the fifties (60-odd years!).

"high 'decalage' together with the rearward (by rc standards) C of G". Old vintage floaters, and the J60 in particular, don't need an "RC standards" C of G. They fly superbly with the rearward CG.

The decalage "problem" stems from the fact that most RC "club" J60s are overweight and overpowered.
i.e. the decalage becomes excessive if you fly with far more power than is needed.

I've built and flown 4 J60s over the last 50 years, and I'm planning another one for next winter!
Sometimes I fly with vintage unthrottled engines and sometimes with a throttle, but the same engine size.
The throttle obviously enables allows much longer flights and the model can be flown lower and closer (to be admired!), but I like to give nice old engines some air time as well.

Club flying also has an impact. If you fly with others then you all have to fly in more or less the same "general flying" manner. Thus, vintage flying is much better if you either fly with other vintage flyers (vintage meets) or fly on your own. In my case, when I fly my Wot 4 or similar, I fly in the afternoon with everyone else, but when I fly vintage, I'm at the field at dawn, and flying alone. Vintage flying when everything is still calm, around 6am in summer, is a beautiful experience and a throwback from my FF youth... And I actually did exactly that two days ago... After the confinement, it was so good!

Apologies for the off-topic!

Edited By brokenenglish on 31/05/2020 07:06:49

David Davis31/05/2020 07:39:00
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3759 forum posts
718 photos

I always fly my vintage models in an appropriately vintage, i.e, guided free flight manner. I never feel the need to change my style of flying if I fly a vintage model in company with clubmates flying their sports-aerobatic models. Of course, the risk of a collision is greater if there are several models in the air at the same time but in thirty-two years of flying r/c I have only had three mid-airs and on two of those occasions my model was hardly damaged.

I will confess however to continuing the upper longeron from the trailing edge of the wing directly to the tailpost on the last two Junior 60s I have built . This increases the tail incidence slightly and in theory reduces the model's propensity to climb under power.

I practice I have not noticed any substantial difference.

David Hall 931/05/2020 09:08:31
265 forum posts
16 photos

My recently finished (&flown) Junior 60 is my first "Vintage" model. I don't know what kit it came from, it was powered by a big brushed motor with an equally big belt drive gear system. The motor appeared to be mounted on bearers that had very little or no down thrust. I replaced the power system with a 3730 1000kv motor with the intention of 2S operation. It was flown initially on 3S with the throttle wound down to 50% and was still overpowered.

My F5J gliders all have a simple mix on the throttle to include a throttle to (down) elevator mix, adjustable on a Tx trim. I copied the mix to my J60 config. Without the mix, the Junior 60 would loop if left to itself during a high power run. With the mix added and adjusted, the climb is as I like it and the glide is spot-on... it all works well for gentle flying.

Incidentally, I still would like 2S operation. The same motor on 2S with a 13x7 prop on my E-glider sounds perfect, a nice calm whir. I would need higher capacity packs for the J60 but adding to my present battery collection is not a good idea. I measured the input power at around 200w and have now replaced the motor with a 2826/950kv and 11x6 prop (plus a little extra weight in the nose). I have yet to fly this.

PatMc01/06/2020 00:45:08
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4407 forum posts
530 photos
Posted by Richard Clark 2 on 31/05/2020 03:14:56:

"reducing the wing incidence is not good idea"...…."I fly my J60 like a J60"

Comment such as these miss the entire point. And PatMc promptly added 5 degrees of downthrust when the original didn't have any at all. Though his "no sidethust" is correct to the original.

The original was a free flight model. Under power it flew at a fixed airspeed (the optimum and constant climb rate for the UNCHANGING power available) in a gentle left (usually) turn due to 'torgue' or the corkscrewing propeller wash ("or" because opinions differ on why they turn to the left).

The rudder trim tab was set to turn the plane to the right. This was to 'open up' the left turn under power and hopefully avoid the dreaded power on spiral dive. It had the pleasant side effect of making the plane turn the other way on the glide.

And the high 'decalage' together with the rearward (by rc standards) C of G had the desired effect of a slow 'landing' with no elevators in often far from optimum circumstances. It's not a 'landing', it's a slow as possible uncontrolled crash.

My suggested changes will not affect the flying characteristics at all. They merely make the rc side of it more pleasant WHEN YOU UNKNOWINGLY force the plane into flight attitudes/speeds both high and low a free flight plane could never get into.

BTW: Power choice is a problem. Electric has advantages though the sound is not authentic, two strokes are 'period correct' but sound unpleasant. I use an OS 30 four-stroke, and what's more, a 1970's US made 'Pro Line' radio (the absolute 'tops' at the time but never imported into the UK) modified to 2.4 and only 20 years out of period.

Edited By Richard Clark 2 on 31/05/2020 03:18:22

Edited By Richard Clark 2 on 31/05/2020 03:20:59

I gave valid reasons why reducing the wing incidence is not a good idea.

Although I mentioned that I had set the downthrust at 5 degrees when I built the model in 1986 I also said if I were to build a Jnr 60 now I would not incorporate any downthrust.
The instructions of the Flair kit that I built the model from suggests using downthrust of between 3 & 5 degrees depending on engine used. I don't know whether or not the KK instructions suggests using any downthrust but it was common for the building notes of free flight & rc models of the era to make a similar suggestion even when none was shown on the plan.

It's incorrect to suggest that the KK Jnr 60 had a rearward cg as the cg isn't shown on either version of original KK Junior 60 plans. The Ben Buckle & Flair plans show what would be considered today as "normal" cg positions.
I suggested using elevator trim to change the "decalage" in order to allow the model to be flown at whatever speed would suit the prevailing wind strength.
Having high "decalage" & rearward cg does not preclude using normal elevator & motor control when landing nor does it make landing any more difficult than having low "decalage".

Not using your ill considered wing incidence changes won't "make the rc side of it more pleasant WHEN YOU UNKNOWINGLY force the plane into flight attitudes/speeds both high and low a free flight plane could never get into" nor will it increase the risk of such a situation when flying vintage or any other models.

Edited By PatMc on 01/06/2020 00:46:27

Richard Clark 201/06/2020 06:44:46
292 forum posts
Posted by PatMc on 01/06/2020 00:45:08:

I gave valid reasons why reducing the wing incidence is not a good idea.


Although I mentioned that I had set the downthrust at 5 degrees when I built the model in 1986 I also said if I were to build a Jnr 60 now I would not incorporate any downthrust.
The instructions of the Flair kit that I built the model from suggests using downthrust of between 3 & 5 degrees depending on engine used. I don't know whether or not the KK instructions suggests using any downthrust but it was common for the building notes of free flight & rc models of the era to make a similar suggestion even when none was shown on the plan.

It's incorrect to suggest that the KK Jnr 60 had a rearward cg as the cg isn't shown on either version of original KK Junior 60 plans. The Ben Buckle & Flair plans show what would be considered today as "normal" cg positions.
I suggested using elevator trim to change the "decalage" in order to allow the model to be flown at whatever speed would suit the prevailing wind strength.
Having high "decalage" & rearward cg does not preclude using normal elevator & motor control when landing nor does it make landing any more difficult than having low "decalage".

Not using your ill considered wing incidence changes won't "make the rc side of it more pleasant WHEN YOU UNKNOWINGLY force the plane into flight attitudes/speeds both high and low a free flight plane could never get into" nor will it increase the risk of such a situation when flying vintage or any other models.

Edited By PatMc on 01/06/2020 00:46:27

Today, with radio control giving the ability to 'flare' for the landing it is just plain silly to make the wing give lots of excess lift by setting the wing at a high incidence relative to the tailplane and simultaneously opposing that excess lift with engine downthrust. The original free flight idea of downthrust was ONLY so the aircraft would automatically slow down when the engine stopped and the downthrust ceased.

However, we are not killing babies here. It's just a toy plane. So you play with yours however you want and I will play with mine my way.

Former Member01/06/2020 07:04:11

[This posting has been removed]

Richard Clark 201/06/2020 07:49:37
292 forum posts
Posted by Jason Channing on 01/06/2020 07:04:11:

Im running a PAW 40 rc on mine, severely overpowered and flys extremely well and its all stock incidents' with no changes any where, although knife edge performance is poor, This old lady gets flown as she deserves from High alpha to inverted, The only changes I would make on My next one is to get rid of the PAW and put a saito 40 in to remove the mess after each days flying as the oil goes everywhere and takes ages to clean, Paw works faultlessly.

Much against my 'better' judgement I was persuaded to put ailerons on mine. Proper inset ones, hinged on the upper surface with a V shaped cutout on the lower surface to allow downward movement, rather than strip ailerons as they would look wrong.

Despite that I kept the original very steep dihedral for 'atmosphere' with 50% differential they work perfectly well with no adverse yaw at all. Reasonably axial rolls included. 

So don't believe the 'experts'. One says they don't work probably without trying it and the rest just parrot him. No sane person builds  a model plane because of what it WON'T do

Also none of this, incidence included,  prevents you flying it in what is thought of as a 'vintage' manner. On a dead calm day mine will fly in gentle circles without touching the sticks for as long as you want

Edited By Richard Clark 2 on 01/06/2020 08:13:48

David Davis01/06/2020 10:29:48
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3759 forum posts
718 photos

The Junior 60 was my first successful r/c model. It was powered by an Irvine 20 car racing engine which turned out to have much more power than most two-stroke 20s. It was finished in olive drab parachute nylon on the fuselage, with the flying surfaces in Natural Solartex with black trim! The whole effct was somewhat drab! I don't have a photograph of it from that period. Perhaps that's just as well.

At the time, 1988, I was an absolute beginner, my radio did not have a trainer facility so I gave the model to an experienced pilot to trim out. After a few minutes with it in the air he said, "I can't stop it from climbing all the time."

Which leads me to my point. What was available to power the original free flight 1946 Junior 60? An ED Competition special perhaps? I don't know what engine powered the original model but you can bet your life that it was far less powerful than anything we are likely to put in it today, and I'm including electric motors too.

So, if you put a more powerful engine into a Junior 60, especially since the mode was designed for free flight, and not make any alteration to its incidences, it will climb strongly. I'm ok with that.

If someone fits an engine to a Junior 60 which is so powerful that at maximum revs it forces the model to perform continuous loops, I'm led to ask, "Why have you fitted such a powerful engine to a model which is capable of flying nicely on far less power?" If you want to perform rolls and inverted flight with it then fine, but the model was never designed for those manoeuvres and that sort of thing is not for me.

I simply take off, climb to altitude, throttle back and bimble about with it, admiring its flying qualities. Maybe a little down trim is required otherwise I let it fly by itself.

If I want to perform aerobatices I have models which will do this readily.

Edited By David Davis on 01/06/2020 10:33:27

Richard Clark 201/06/2020 11:59:38
292 forum posts
Posted by David Davis on 01/06/2020 10:29:48:

The Junior 60 was my first successful r/c model. It was powered by an Irvine 20 car racing engine which turned out to have much more power than most two-stroke 20s. It was finished in olive drab parachute nylon on the fuselage, with the flying surfaces in Natural Solartex with black trim! The whole effct was somewhat drab! I don't have a photograph of it from that period. Perhaps that's just as well.

At the time, 1988, I was an absolute beginner, my radio did not have a trainer facility so I gave the model to an experienced pilot to trim out. After a few minutes with it in the air he said, "I can't stop it from climbing all the time."

Which leads me to my point. What was available to power the original free flight 1946 Junior 60? An ED Competition special perhaps? I don't know what engine powered the original model but you can bet your life that it was far less powerful than anything we are likely to put in it today, and I'm including electric motors too.

So, if you put a more powerful engine into a Junior 60, especially since the mode was designed for free flight, and not make any alteration to its incidences, it will climb strongly. I'm ok with that.

If someone fits an engine to a Junior 60 which is so powerful that at maximum revs it forces the model to perform continuous loops, I'm led to ask, "Why have you fitted such a powerful engine to a model which is capable of flying nicely on far less power?" If you want to perform rolls and inverted flight with it then fine, but the model was never designed for those manoeuvres and that sort of thing is not for me.

I simply take off, climb to altitude, throttle back and bimble about with it, admiring its flying qualities. Maybe a little down trim is required otherwise I let it fly by itself.

If I want to perform aerobatices I have models which will do this readily.

Edited By David Davis on 01/06/2020 10:33:27

I tend to fit any 'reasonable size' spare engine that I happen to have at the time. My Junior 60 started off with the vastly more powerful than neccessary OS Max 35 AX two stroke. But later I found a new (but discontinued) OS 30 four stroke, which sounds nicer, is considerably less powerful, but more than sufficient, and the much smaller silencer on its swivellable exhaust pipe doesn't spoil the traditional 'cylinder stuck out' side view in flight.

I spend most of the time bumbling about but it's a laugh to throw it around at times. (I replaced the balsa main spar with a spruce one of the same size but tapering to half size over the root to tip distance to keep the tip inertia low.)

My latest effort is the 65 inch Aeronca Sedan built from the plan from the 1953 Mercury kit. As decent small glows are getting hard to find. I ended up with a rear exhaust high revving twin ball race 'racing' MVVS 21 RC. I bought as 'new old stock' from the local model shop. On a large diameter fine pitch prop it's fine but I'm tempted to buy a PAW 19 RC diesel for it.

Next is an EDF rc version of the old. 1958 049-09 ducted fan Veron Deltaceptor (it's on Outerzone). That'll be something really different

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