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2 or 3 questions please, need some wise advice

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Nigel R17/02/2020 12:36:29
3464 forum posts
524 photos

My dad has done a couple of vintage slow fliers. All of them have -

relocated ply firewall with motor screwed direct to it

vertical battery immediately behind the motor

access hatch on top of nose above the battery.

speed controller right behind battery

servos right behind speed controller

motor mounted using a long screwdriver, screwed straight into ply firewall, with a fixed wood block cowling around it

about 50w/lb AUW (including battery) - these things don't need much juice to stay aloft, they're essentially a powered glider with wheels.

I'm fairly sure he used 3S 2200mAh lipo on a Southerner of similar dimensions. Don't know exactly what motor or prop or ESC, sorry.

PeterF17/02/2020 12:41:35
479 forum posts
669 photos

There is nothing stopping you using the motor you have and just putting a smaller diameter prop on to reduce the thrust and power consumption as long as the motor fits and the plane balances. With an electric motor the revs will not increase much unlike IC if that is where your experience lies. An 11x6 prop would reduce the power to around 275W and a 12x6 to around 350W on a 3 cell battery.

Bob Cotsford17/02/2020 13:00:29
8230 forum posts
454 photos

As Peter says, your 4240/10 would be fine for this model, at around 890kv even a 13*6 on 3S would only be giving you around 370W according to e-calc.

As for covering - am I the only one who used to get a gloss finish when using tissue or nylon back in the 60/70s? I would be happy using film on a vintage model. Tex would be tougher, comparable to doped nylon, but for this size of model film covering should be strong enough.

911hillclimber17/02/2020 14:06:44
155 forum posts
30 photos

To answer in order:

Yes, I used to hillclimb my old 911 Porsche, my 'name' came from that a very long time ago!

Still have the car, still hill climb, but in a very different car now.


The BIG motor I have: v interesting thoughts on weight and power and prop size. I have had a nice simple reply from George.

He says:

4-Max PO-3541-920 motor


Prop 12 x 6 or 13 x 6

Batt: PPL-40C3S-2200

Refreshing to have a specialist reply with all the questions answered!

If I keep the Big Motor (I've modelled the cowl etc to install it) what Esc/battery spec do I need please?

I find this a bit of a mine-field.....

Edited By 911hillclimber on 17/02/2020 14:09:12

Bob Cotsford17/02/2020 15:44:19
8230 forum posts
454 photos

You could still use George's recommended esc, his 920kv motor will actually draw a shade more current on those props than your 870-890kv motor will. That looks to be a 40A esc which in theory would be good for 440W on 3S. Battery size will be a case of what size will fit. That 2200mAh could be taken as a minimum, it's a pretty common size as used in a lot of foam ARTFs. If there's room in the nose you could go bigger but both my Junior 60 and Black Magic give good enough flight times on 2200 3S packs though they both need a bit of lead too in order to balance correctly.

911hillclimber17/02/2020 16:45:48
155 forum posts
30 photos

I don't know the equivalence of 'Georges' PO 3541-920 to the Overlander T4240/10 motor I have.

It would be good to use it if I can as I've done all the drilling and ply panels to allow it's fitting.

Not worried about the cost (£34), just want to be sure the plane will fly correctly.

Not sure adding lead to get the CofG is a big deal as the plane obviously is not an aerobatic design.

Not a lot of immediate room in the nose of this plane to get the batteries in.

Denis Watkins17/02/2020 16:58:40
4168 forum posts
82 photos

Hi Graham

The lads don't like adding too much lead because this adds speed to flight

We have to get the C of G right, so prefer to move servos and batteries about where we can

You are building a relative lightweight for more sedate flight

Unnecessary lead then makes this less of a slow fly

PatMc17/02/2020 17:26:52
4318 forum posts
524 photos
Posted by Denis Watkins on 17/02/2020 16:58:40:

Unnecessary lead then makes this less of a slow fly

But not necessarily much less. wink 2

Bob Cotsford17/02/2020 17:57:21
8230 forum posts
454 photos

Yes, my previous Junior 60 came as IC power and the previous owner used a ton of lead to balance it. It still wafted along quite nicely. Once I moved servos and the battery around I got rid of most of the lead. It still just wafted around but having less lead gave me a warm fuzzy feeling wink

Don Fry17/02/2020 18:52:04
4557 forum posts
54 photos

Look at Nigel R post of 12.36. That is a recipe for success. Better to have a bit of weight added at the back,than half a bag of sugar at the front.

Cool, and brave, early 911 up a hill.

I was born not far from Shelsley Walsh. My dad used to prepare, as a hobby, powertrains for the off road climbers.

But the workshop usually had 4 and 6 cylinder BMC units, for the road climbers. Never saw a Porsche unit. I remember the interminable rebuild of a Bugatti engine, and shoehorning an oil pump in. I think, that was a racing car.

Small child's hands were good for rebuilding carbs. Or being dangled into machinery spaces by the ankles to start a screw. Child abuse nowadays.

All changed, passed my 11 plus. Dad never treated me the same. Not destined for tools he thought. And I have taken half a life to learn, what was available for free, in childhood.

Not a criticism, no complaints, never knew him as an adult.

911hillclimber17/02/2020 22:57:38
155 forum posts
30 photos

Don: been competing since 1990 and have run Shelsley and the other hills every year. Great sport and very demanding. I am very involved with Loton Park by Welshpool too.

Aeromodelling looks to be quite the opposite hence the appeal, but it will not be a substitute.

I'm sure my first landing will be almost as scary as a full hill climb run!

I think I'm leaning to keeping the motor I have and get the appropriate controls and battery pack from 4-Max for about 10 mins flight time. (too long?)

To my mind the motor feels about as heavy as the never been run PAW diesel I bought for a control liner about 35 years ago...

Old Geezer18/02/2020 00:02:07
670 forum posts

911 - the club you're thinking of is the Central MFC - not 'zactly secret though. We fly from a field off Lowe Lane on the Kidderminster/Bridgnorth road - our club details are on the BMFA site. We have a "Wrinkly Fliers" sub-group who - weather permitting - fly every Tuesday, Thursday and Saturday morning - the friendliest bunch of aged p***takers you could ever hope to fly with.

911hillclimber18/02/2020 08:10:29
155 forum posts
30 photos

Yes, that is the club I intend to join when the plane is ready, but even if not, I have the old Stol which I converted to electric a few years ago (with a lot of help from this forum) so have something ready.

The Stol is a smaller wingspan, same size fuselage.

As a motorsport competitor, used to the micky taking!

Peter Miller18/02/2020 08:40:46
10717 forum posts
1254 photos
10 articles
Posted by 911hillclimber on 17/02/2020 22:57:38:

I'm sure my first landing will be almost as scary as a full hill climb run!


Not with a vintage model. Just line it up, throttle right back and it will land its self . If you want to be fancy squeeze in a touch of up elevator at the last flair.

911hillclimber18/02/2020 15:22:23
155 forum posts
30 photos

I do hope you are right!

Watched endless YouTube vids of these classics, esp Junior 60 /Super Scorpions flying, touch downs and landings and they all look like you say.

Feeling nervy already, but I'm sure I will crack it.

All part of the fun, sounds like I will get a LOT of sympathy from fellow aviators at the time....

Meanwhile, back to carving the mile of leading edges on this kit.

Nody has said not to use the Big motor as to do so will be a disaster, so will ask 4 Max for the motor speed controller and battery pack. This will save mods to the ply bulk head I've made for the motor mount.

This has been a great thread for me, I really appreciate everyone's help so far.

Peter Miller18/02/2020 18:24:24
10717 forum posts
1254 photos
10 articles

Many years ago one of our club members wives taught primary school childrenat a locla private school and she asked me to come an talk to them.

I took my original Suoper Scorpion and we took her class out onto the school lawns.

It was most interesting.The little boys yended top thrash the sticks around but the little girls flew the model so smoothly and gently.

No, I did let them land it because it was a fairly restricted area but I am fairly certain the little girls would have managed it.

Also, a friend was lerning to fly and was doing well but he could never land. I lent him an three channel shouler wing model.

He learned to land in one session.

paul d18/02/2020 19:03:03
130 forum posts
8 photos

Hillclimber, not sure where your located but if your anywhere near surrey your more than welcome to come fly my vintage jobs just to show how benign they are.

I'm sure yours will be fine, if in doubt chop the throttle and let it sort it's self out....

Bruce Collinson18/02/2020 19:16:31
468 forum posts

911, check that you’ve got a full set of the right connectors for the motor, ESC and LiPo. George has them all in stock. Bullets and XTs seem easier to solder. Amass branded seem to be more resilient to excess heat. Will you fit a battery isolator? George has them too.

I started with Deans but they’re pigs to solder especially if using thick cable. I’ve swapped the whole fleet to XT 50s apart from the 6S planes which are on XT 90s, for what it’s worth.


911hillclimber18/02/2020 22:29:36
155 forum posts
30 photos

Paul: I'm up in West Midlands/Shropshire, but thanks for the offer!


Good point. I used those hard to solder connections before on the Stol conversion, pigs to do.

I'll ask George for an 'installation kit' if he can do such a thing. The ones I used on the Stol are yellow in colour.

The wiring is the least interesting part of all this and I'm not looking forward to it at all.

Just about to open my 3rd tube of balsa cement tomorrow so getting close to the end of the easy bit.

Just wishing a bit I had simply bought a nice 4 stroke!

Peter Miller19/02/2020 08:22:13
10717 forum posts
1254 photos
10 articles

Balsa cement? It is a long timme since I used that. I and most other people these days use aliphatic resin. It take\s longer to dry but doe makea stronger joint.

I use XT60 plugs and socket sets. They seem to be about the best for our size of models and power units.

Up until a couple of years ago I was a dedicate ic flyer but now I have to confess that I rarely take an ic model flying. The extra weight of starter (I can hand start but...) battery, fuel etc is a bit too much for these oldlegs to lug up the long if gentle hill to out flying site.

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