WOT4e flying v Junior 60 (with elec conversion)?

[GrumpyGnome]

21 minutes ago, 911hillclimber said:

I guess a 5 cell 2200 is longer than the 3 or probably larger in all dimensions.

Probably... but possibly too much voltage for you esc and/or motor as well....

[David Davis]

I was thinking more along the lines of a 3000-4000 3S LiPo.

[kc]

It would be worth seeing how much further forward the lipo would need to go to achieve CG without any lead weight.  Try strapping the lipo on at the very front using sticky tape or rubber bands etc just to see what is possible.  It's quite likely you could dispense with most or even all of the lead with the Lipo right at the front.   Even if you prefer not to modify or  lengthen the front to get the Lipo forward it will tell you what is possible in future.

 

Light models crash less often and even when they do they crash less heavily!

[911hillclimber]

Just for interest;

 

If I remove the 166 grm 3S 2200 battery and put it where the prop goes on the motor, the fuselage just about balances out, slightly tail down.

 

I cannot see an 'elegant' way to get the battery further forward.

Even cutting the nose about a lot to get the battery vertically and in front of the undercarriage bulkhead, the plane needs 155 grams of lead in the bottom of the nose under the motor.

I'll leave it as it is now and load the nose under the motor and leave the battery inside, vertically behind the undercarriage bulkhead.

[911hillclimber]

Sorry, can't edit my post above, but made a steel prop nut as long as a dare without this plane looking like Pinocchio's long nose..

 

Had to machine the bar down to 19.5mm dia to seat onto the prop hub. The nut weighs 54 gram and the prop 20.

 

All bolted on and the battery in the cabin the plane needs:

 

C of G @ 36% of chord (90mm from leading edge, chord is 10"/250mm): 114 grams ballast.

C of G @ 28% of chord (70mm), ballast needed is 199 grams

 

On the Belair plan the spar is 50mm from the leading edge.

 

Seeing as the ideal C of G is not clear I think 150 grams of weight in the box below the motor is a good starting point. (?)

[PatMc]

If it's any help here is a link to the thread showing how I refurbished & converted my Jnr 60 from IC to electric. 

Regarding model's RTF weight before refurb it was 1871g after it dropped to 1725g. The cg moved back from the Flair kit plan position to aprox 40% & model handles just as benignly but with a better glide & wider speed envelope.

Regarding the motor, what weight & KV is yours ?  A heavier & potentialy more powerful than necessary motor is a good way to reduce any required nose weight. The power can be limited by limmiting the prop size, which also means the motor is having an easy life.

 

PS I forgot to mention that when IC powered the wheels were sometimes replaced by floats & flown from a local small lake & from Kielder lake. I also flew it with the floats from snow & wet grass. The floats increased the weight to 2240g which didn't have any ill effect on the model's general handling. 

Edited January 6 by PatMc

[911hillclimber]

Thank you for your post Pat.

I'll closely read it after this post!

 

The motor is a big thumping Overlander T4240/10, a motor bought a long time ago and never used, so thought I would put it in this 60.

It weighs 241 gr with steel mount, prop and nut. It scres to the original IC motor mount hole like yours.

The ESC can take 3 and 5 cells but is big compared to the WOT4 unit.

 

The prop is an 11 x 7e, it was bought because the Junior 60 upgrade (from IC to elect) on the 4Max website lists it as right for the plane.

 

The motor looks a bit big for the model, but you don't HAVE to use full throttle!

 

I'll try to post pictures tomorrow.

Graham.

 

Edit:

Just looked at the thread Pat. Are all Belair wings bolt-on?. My 60 is made for classic rubber bands front and rear.

The undercarriage bulkhead wood will not allow the battery to be in the engine bay, the power cables and charger lead would be almost level with the front of the wing. Maybe my plan is a Flair kit or even a Ben Buckle kit?

Edited January 6 by 911hillclimber

[Peter Jenkins]

It may help you to know that there isn't a single CG position.  There is a range of CG positions.  The aft most one is when the aircraft becomes neutral in its response i.e. if the nose is lifted up by a gust it will just stay in that position or putting it another way, the aircraft has no stability nor for that matter any instability.  Moving past the aft limit doesn't suddenly transform the aircraft into an uncontrollable beast.  It will manifest itself as having a very slightly unstable trait so that you would need to return the aircraft to S&L flight using the controls.  The forward CG position is usually that at which for a tricycle undercarriage aircraft there will be insufficient elevator force to get the aircraft to take off and once in the air it will be difficult to combat any nose down tendency.  To determine the aft limit, arm yourself with some lead stick on weights and stick them on 10 g at a time to begin with to shift the CG aft.  Go and fly the aeroplane and if its still very stable add another 10 g etc.  Exactly how much stability you'd like for your aircraft will vary depending on your flying but suffice to say that many pilots tend to fly with the CG too far forward and end up with aircraft that handle terribly.

[911hillclimber]

Thank you Peter for this insight.

 

Previously, I've had suggestions that 90mm back from the leading edge is a good spot.

The 'plan' I've seen on google shows 70mm C of G.

The nose ballast needed is quite a difference between the two spots.

 

I think I'm over-thinking all this (I an a novice to all this as you may have realised!).

 

Currently trying to sort the snakes out.

 

The ones from 4Max are really nice, but the slippy inner plastic cables (must have a lot of ptfe in them) ate too large to pass through the existing outers in the plane.

 

This means the whole of the 4Max snakes are inside the plane.

Great, except i need crimp-on 2mm threaded ends for the servo end, the snakes come with one enge crimped on with steel thread and clevis.

 

Of course you can super glue to the ptfe inner wire so need some crimp-on ends.

Local model shop is closed today so this has stalled the plane's progress.

 

Nothing really going to plan!

[Jonathan M]

On 07/01/2025 at 14:31, Peter Jenkins said:

It may help you to know that there isn't a single CG position.  There is a range of CG positions.  The aft most one is when the aircraft becomes neutral in its response i.e. if the nose is lifted up by a gust it will just stay in that position or putting it another way, the aircraft has no stability nor for that matter any instability.  Moving past the aft limit doesn't suddenly transform the aircraft into an uncontrollable beast.  It will manifest itself as having a very slightly unstable trait so that you would need to return the aircraft to S&L flight using the controls.  The forward CG position is usually that at which for a tricycle undercarriage aircraft there will be insufficient elevator force to get the aircraft to take off and once in the air it will be difficult to combat any nose down tendency.  To determine the aft limit, arm yourself with some lead stick on weights and stick them on 10 g at a time to begin with to shift the CG aft.  Go and fly the aeroplane and if its still very stable add another 10 g etc.  Exactly how much stability you'd like for your aircraft will vary depending on your flying but suffice to say that many pilots tend to fly with the CG too far forward and end up with aircraft that handle terribly.

Excellent contribution.

 

Worth also noting that the further back the CG (ideally to almost but not quite neutral) the less elevator deflection that will be needed. So, as you move the CG progressively aft, dial down the travel slightly, else things could get hairier than ideal as you move towards neutral stability. But don't overdo this, you will want enough up elevator travel to flare out, etc.

[911hillclimber]

The servo throw the elevator +/- 15 degs, or about 12mm up/down.

That seems about right to me, but I can increase those values to add about 50% more.

 

The rudder is dramatically more, a good +/- 30 degs.

Edited January 8 by 911hillclimber

[911hillclimber]

Plane is now ready for the first flights this year. After some messing getting the snakes in and glued into position, finding out my '5 minute' epoxy is closer to 25 hours to set, and adding a full 200 Grams of weight right tucked-up into the nose motor box everything works, no binding and just might be nose heavy at 80mm C of G.

 

Bit of an effort but pleased with my plane, all in cost about £40 inc purchase. of the bare plane at Weston Park 2 years ago.

Such a nice design.

I think it is a Flair version, but still not too sure but has corrugated steel gussets on the undercarriage which is a give away I think.

 

With the cold spell now coming to a brief end it is back to classic car maintenance next week...

 

As ever on here, thank you all for the help and advice.