Trimming tips for the electric version of the Junior 60

[Skippers Walker]

Taking advantage of some very calm conditions a flying pal achieved a maiden flight today of my newly built J60 (2020). The model required 40g extra nose weight to achieve the 'plan' CG. Despite this my 'test pilot' needed to feed in max down trim in an attempt to stay in level flight! A safe landing was made non the less. The conclusions reached so far suggest that perhaps more nose weight should be added plus a little down thrust on the motor before flying again. Are there any seasoned J60 flyers that may wish to comment further about this trimming issue please?

Stay safe

SW

[Peter Jenkins]

I would try reducing wing incidence rather than move the CG further forward.  If the aircraft wasn't twitchy then the CG is fine where it is.  Your problem is too much lift so the relationship between the wing and tailplane is wrong.  Easiest solution is reduce the wing incidence by packing up the rear of the wing.  If you then find that application of power makes her climb then add downthrust but try reducing wing incidence first.

[PatMc]

Reducing the wing incidence would have the effect of also reducing the motor downthrust.

The quick easy cure is to adjust the clevis to give the required amount of down elevator when the Tx trim is neutral. In all probability the model will cruise without climbing simply by reducing the throttle once the desired altitude is reached.

My Jnr60 has the cg at 33mm behind the plan cg & about 10mm down elevator with the Tx trim at neutral. Flies at it's power on slowest with full up trim (elevator neutral) and a smidgeon of throttle. 

Built circa 1986 there's a thread on it's refurb & electric conversion here.
 

[Peter Jenkins]

Actually, increasing downthrust has no effect on the wing/tailplane relationship.  But I agree that increasing downthrust will help as well.  As ever with aerodynamics it's swings and roundabouts.

[Don Fry]

A J 60 will climb on power. Reduce power it won’t climb.  Reminder, throttle is the climb control. Set up as plan, that it it’s envelope. It is also indifferent to a rearward CG.
Reduce the throttle.

Deck chair, a beer, enjoy. Anything else, get another design. 
A one speed wing.

if you want to fly in a little more wind, a bit of down elevator, a bit more power. But still a calm weather flyer. 

[PatMc]

7 minutes ago, Peter Jenkins said:

Actually, increasing downthrust has no effect on the wing/tailplane relationship.  But I agree that increasing downthrust will help as well.  As ever with aerodynamics it's swings and roundabouts.

I didn't suggest increasing downthrust or say it had any effect on the wing/tailplane relationship. I pointed out that reducing incidence would in the process reduce downthrust. The wing incidence & motor thrust line relationship is locked.  

[PatMc]

3 minutes ago, Don Fry said:

A J 60 will climb on power. Reduce power it won’t climb.  Reminder, throttle is the climb control. Set up as plan, that it it’s envelope. It is also indifferent to a rearward CG.
Reduce the throttle.

Deck chair, a beer, enjoy. Anything else, get another design. 
A one speed wing.

if you want to fly in a little more wind, a bit of down elevator, a bit more power. But still a calm weather flyer. 

Nearly there but the a "one speed" wing epithet is a fallacy. 

[Skippers Walker]

Some really interesting but slightly confusing stuff guys. I'm not too sure if I should stock up on beer, buy a new chair or take a pin and stab at the text for a 'next step?

If there was one change to make to start with what would that one change be please?

Kind regards

SW

[Bob Cotsford]

Throttle back!

If it drifts backwards then add down trim and a little more throttle.

Edited June 6, 2021 by Bob Cotsford

[Peter Jenkins]

Assuming your tailplane is glued in place, the simplest thing is to reduce wing incidence by packing the the bottom of the wing trailing edge.

[PatMc]

It's simpler still to adjust the elevator clevis to give the desired degree of down elevator with the added advantage that it doesn't alter the effective thrust line.

Edited June 6, 2021 by PatMc

[ken anderson.]

hello SW,too much power will make your Jnr climb like a goodin,throttle back to enough to keep the model cruising(it'll need very little power)...and thats it...open up and it will climb,throttle back and it will sink......it may need a bit of down trim to get it to sink/land.......they are vey good flyers.....once you get used to the model...its a Load of Fun.

 

ken anderson...ne..1...Jnr 60 dept.

 

[David Davis]

SW the Flair Junior 60 was my first successful radio controlled model, consequently the design still holds a place in my heart. It was powered by an Irvine 20 car racing engine which some kid had butchered and guided by a Sanwa Conquest radio if anyone remebers them. Without realising it I had made the tailplane out of the heaviest wood in the box so that it required one and a half pounds (680grammes) of lead in the nose to get the cg right! Yes really! It still flew and displayed all of the characheristics which you describe. One shouldn't be surprised. It was designed as a free flight model to climb under power and to glide when the power was off.

 

I subsequently built a lighter tailplane for it, moved the battery under the engine and was able to remove all of the lead. It went on to have several different engines installed and was even converted to electric power. In the end I gave it to one of my trainee pilots. The model obviously didn't like him. We lost signal and watched it descend far away into a field of wheat. We were unable to find it but the farmer did!

 

I have built two or three Junior 60s since then and changed the structure slightly continuing the upper longeron in a continuous line to the stern post so that the tailplane adopted a positive angle of attack in order to stop the climbing tendency. I can't say that I noticed much difference.

 

Edited June 7, 2021 by David Davis

[Skippers Walker]

Good morning modellers

Thanks for all the comments about the J60. It has been a very longstanding (60 years!) ambition of mine to build and fly this model. As a youth and modeller in the 50's I could never afford the KK kit little own the power plant to drive it (ED2.46 me thinks?) all well beyond my limited funds at that time. I certainly built and flew a good many FF models but as I then only could afford an ED Bee 1cc they had to be suitable for that engine. I've recently finished a Vic Smeed Madcap for electric power, a virtual copy of my original version from about 1955!. All of this is really a trip down memory lane whilst I can still wobble a TX stick.

Please keep the comments coming they are all very interesting.

Stay Well

SW (Chris)

[Matt Carlton]

There is little point in trying to get a J60 to fly like a neutrally stable aerobatic model, just accept that what it really wants to do is fly along with just enough throttle to maintain altitude, whilst you sit in a deckchair and sip a Pimms and listen to something like this:

 

 

[Nigel R]

Mine was exactly as plan. Flew great. Any much sort of power, it climbed. Engine at idle, it glided slowly down. In between was level. Elevator was largely optional. It is, as Don says, what it does. 

 

That said, for some extra amusement, try flying it upside down.

 

Preferably after that beer.

 

[Skippers Walker]

Thanks Nigel. I really am beginning to understand the general flight envelope of this model.

After my F/F days I spent many years flying thermal and slope soarers, with a break from flying in the 1990's until fairly recently. Returning to the sport in my 70's, I have attempted to embrace the 'new' world of electric flight. With a good deal of patience and helpful advice from a small friendly group of seasoned power modellers I can now fly electric gliders reasonably well. I have just started a transition to flying conventional electric powered models, the J60 being one of the basic trainers on the list to fly first. Confidence is returning slowly but with a fairly steep learning curve ahead!

Kind regards

SW (Chris)

[Matt Carlton]

To be honest, you can fly a J60 in exactly the same way that you do an electric glider, but rather than completely close the throttle, just throttle back to maintain height. 

[Skippers Walker]

Music to my ears Matt, thanks. I just need to keep it simple to begin with, hence my choice of model combined with a fair portion of nostalgia too!

Cheers for now

Chris

[PatMc]

It's a common myth that the Jnr 60, and a lot of other vintage models, were originally always flown sedately with the engine at tickover. Remember that when these models were being produced they were state of the art, the people flying them were not timid old farts reminiscing about things that didn't happen. They were often teenagers & recently "demobbed" national servicemen, their models were often used in timed power run duration de-centralised (i.e. local area) competitions but even when not they were flown in the same manner - full power, steep climb for (IIRC) 15 secs then glide. Free flight of course.  

The old guys of the time mostly flew underpowered scale FF military models only in calm late afternoons & evenings and sat around tutting their disapproval of the manner of "todays" youth's idea of flying models in general but especially control line 
As more specialised FF duration models were designed, the Jnr 60 was one of the most popular to be converted to s/c RC, hence the wider fuselage later (1956) version but in their sports FF mode the short fast climb then glide routine was still common.   

 

Edited June 8, 2021 by PatMc

[Skippers Walker]

Thanks for the memories Pat. I'm certainly old enough to remember the F/F tank full, launch and chase era of the 40s and 50s. Many of my epics finished in trees or distant fields often after a hectic cycle chase. I couldn't afford to buy or use the early radio kit in those times, so it's a privilege now to be able to attempt to fly some of those old timers fitted with modern electronic R/C gear. It certainly saves a sweaty bike ride! My biggest problem now is coordinating brain with TX sticks!

Best wishes

Chris (SW)

[Matt Carlton]

 

38 minutes ago, PatMc said:

It's a common myth that the Jnr 60, and a lot of other vintage models, were originally always flown sedately with the engine at tickover.

 

Quite so, but when we convert free flight models to RC, generally we don't try to emulate the original flight pattern of rapid climb and a glide just off the stall.

Given that, pottering around sedately is probably the better way to go for general sport flying. 

Of course, if the OP wants to stick an Ohlsson Rice 60 in the nose and watch it spiral up to 500ft pdq then of course, that's a different conversation ?

 

[Don Fry]

I lost mine once, it had so little elevator, the thermal took over, recovered 17 miles away, landed in a paved farmyard, undamaged.

And Pat, your rose tinted specs are a bit misted up. When the J 60 was invented, motors only had one speed, the arthritic best they could manage, or stopped.

I for one, if you want to return to the era, will appoint you chaser in chief, and holder of the bottle opener. 

[PatMc]

No rose tinted specs here, Don. I only ever flew one FF power model, KK Bandit or Outlaw (can't remember which). I wouldn't have built that but I was given an ED Bee by a workmate & there was no way I was going to build a CL model small enough for it.

Getting back to the Jnr 60 - I lived in Dundee for a couple of years in the mid '50's, joined the local club, flew CL with most of the lads of my age & scoffed at the aforementioned scale buffs. However there was one old codger, he must have been at least 40 ?, who would turn up & have a couple of practice flights of the SMAE stunt schedule with one of several beautifully built models. He also had two Jnr 60's that he flew regularly. One was the 2nd KK version powered by an ED Racer modified for two speed running via twin needle valves to give normal full power or rich lower power running. This model was fairly new & equipped with home made radio gear for rudder & motor control & usually took about 1/2 an hour to tune & set up before it's first of two or three flights for the day. Although it was by no means fast he always flew it in a purposeful manner, no haphazard drifting around, then land deadstick within a couple of paces from himself. It was his first venture into RC. 

The older Jnr 60 was the earliest version, FF & several years old. Although in good condition it was obviously well used with plenty of patches to the tissue but also decorated with a number of transfers showing that it had won or placed in several competitions. Power was a Yulon 29 mounted inverted in order to give best access to the needle because the intake pointed downward. The owner told me that this was the third engine he'd used in the model, previous being a British diesel then a US made sparky but the Yulon was by far the most powerful. As I remember it the climb was near vertical & fast, it usually transitioned into the glide smoothly although sometimes a couple of stalls before settling then glide in circles with a few of us following it. Impressive though it was, the distance it travelled downwind & thoughts of losing a valued engine convinced me to stick with CL until I could afford RC.  

Neither of these Jnr 60's were flown in the sedate fashion that's today considered how vintage models should be flown.

Here's mine in it's first flight after electrocution, I don't think the climb is anywhere near as fast as the FF one described. 

 

BTW @Nigel R I've flown it inverted several times, with all that dihedral it's like balancing on a ball & if you push the nose up too much the rudder control reverses. ? 

[Don Fry]

Right mate, Yulon 29, 300 watts? J60, 3 lbs?

Vertical and fast?