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Jef Ott

electric free flight design

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Jef Ott

Peter,

Totally agree. The Ladybird method will degrade the strength of the wood, but I felt it was relevant as an alternative method of getting the required bends, particularly in such cases as in the rear stringers of the Ladybird, where they are perhaps more decorative than structural. 

And yes, I will still be soaking or steaming the longeron wood on my future fuselage builds, unless someone comes up with an even better idea!

Happy building, safe flying.

Jef

 

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Guest

Jef,

Here is another method of bending longerons to shape which I have used for many years.

Soak the wood for 5 mins in warm water. IMO this fills the pores of the wood and acts like a plumbers coil to prevent bucklng.

Find a baked bean can , eat the contents , find a night light or candle. Fire it up and bend the longeron around the hot can.

Its surprising how hot the can will get and the heat dissipates the water as steam. You get very accurate bends. Dry 24h before glue.

Seemples, Ian

 

 

longerons.jpg

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PeterT
Quote

Find a baked bean can , eat the contents

......and if you don't like baked beans the barrel of a 50-100W soldering iron (switched on of course!) works just as well without the baked beans after effect:rolleyes::D

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oipigface

Ever set fire to your workshop?

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Guest

Hi Peter,

I did try the soldering iron method but I was always over bending and often broke the longeron. The larger diameter of the bean can prevents this happening.

First Area tomorrow...are you up for it?

Regards Ian

 

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PeterT

Hello Ian

I've always managed OK with the soldering iron, but don't need to do much forming and thus steaming over a kettle normally suffices. I made up a can & tealight heater many years ago but

Quote

Ever set fire to your workshop?

as my workshop is in the loft I decided that it was probably better to use another less potentially flammable method. Burning down the shed is one thing, the house is something else:rolleyes:

Just finished charging batteries and making up coupe motors for tomorrow. It'll be a trifle breezy especially down on the coast, but  at least with the wind from the NE there is a good pub downwind!

Happy flying

Peter

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Jef Ott

Goodbye Normal Beans,

Though I never knew you at all,

.........

And it seemed to Ian and PT,

You can bend the wood,

With a candle in the tin.

Sorry Elton.

 

Been wondering what to do with the scented candles we seem to attract at Christmas times. Can't wait to give it a go...

Woodbender.jpg

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PeterT

Jef

I like it! Probably better than the original:D

To stop the tin from rolling around, cut a couple of slits about 1/2" apart & 1" long with tinsnips, bend down, and you can use the resultant tag to hold the contraption in a small bench vice.

Peter

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Norman
On 12/4/2015 at 11:30, Jef said:

Target weight.... I Would think <60g, but don't have any experience with the model prior to this. Model is made with original Keilkraft wood. Built using PVA, tissue covered, very little deviation from original.

Brushless motor. 2S LiPo, 240mAh.

FF

What is a logic level signal?

KP Aero 35 sec timer.

Thanks for your help.

Regards,

Jef

edited_1447810234614.jpg

That skeleton is really cool.

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Jef Ott

Thank you Norman. 

The Pixie is without doubt the strongest and prettiest model I have ever built. Glad you like the skeleton shot, I think it looks even better with its clothes on. This shot taken today as a comparison to the naked one, after many flights and just a couple of minor tissue repairs...

Pixie still looking good March 21st.jpg

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Jef Ott

This is what it's all about though, putting silly grins on the faces of the builders and fliers...

Woodside Session 22 3 16 Dad and Judi.jpg

Woodside Session 22 3 16 Silly grin competition.jpg

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EssexBOF
On 12/02/2016 at 00:56, Jef said:

Peter,

Totally agree. The Ladybird method will degrade the strength of the wood, but I felt it was relevant as an alternative method of getting the required bends, particularly in such cases as in the rear stringers of the Ladybird, where they are perhaps more decorative than structural. 

And yes, I will still be soaking or steaming the longeron wood on my future fuselage builds, unless someone comes up with an even better idea!

Happy building, safe flying.

Jef

 

Some time back when made a Tomboy Senior, I had the problem of the curvature in the bottom longeron,being nigh on impossible to bend to shape where comes up at the front. Decided to laminate it from 4 pieces of 1/16 X 1/4 to give the 1/4 square final cross section. Works a treat and seemed stronger due to the glue joints.

Being at a bit of a loss at the moment, have started a radio assist version of Ben Shereshaw's "Cumulus"  I have a large collection plans and articles that I inherited from Dave Mason's modelling magpie past. Dave actually made one of these that he used to fly at Old Warden, from time to time. It is 50% of the original at 48" span and now being able to use 2.4 makes it attractive as to avoid walking and tree climbing. Think it will be diesel powered rather than electric but we will see

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mikef

Question for Arthur...

I've set a friend up with a Competitor plan and he's talking of an electric version.  What motor battery and prop are you using?  What kind of performance does it give?

Good to see you out with a model!

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Jef Ott
20 hours ago, mikef said:

Question for Arthur...

I've set a friend up with a Competitor plan and he's talking of an electric version.  What motor battery and prop are you using?  What kind of performance does it give?

Good to see you out with a model!

Mike,

Whilst I would have no hesitation in recommending the same set up as my Pixie has, as detailed in this thread (which gives plenty of adjustable power for very little money), I have been unable to buy any more of the excellent little bell motors since. 

I was pleased to pass on your question, and it will be a pleasure for  him to respond, of that I am sure.

Thanks for giving him something to do.

 

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Jef Ott

Hi Mike,

Arthur Ott's secretary here!

Prop is a 7.5 x 4 folder, on a home made hub.

Timer is a KP Aero 35 for brushless motors.

Basic 6A ESC #400266 from Robotbirds.

250mAh 2S1P helicopter battery.

Motor is 22mm Baby Outrunner C22-16-25 from Robotbirds.

Fuse holder is chassis mounting 20mm fuse holder from Maplins with 2A fuse.

Small slide switch from stock. 

2mm gold bullet connector plugs and sockets.

The speed controller is set very low, with a 10 to 15 second motor run, for a gentle circling flight, power right and glide right.

There is plenty of power in hand and it would take a much bigger field, than we have locally, to use a longer motor run.

Any further questions please feel free to ask!

Late edit. Just checked the current with the controller set for a slow steady climb, 700mA. This equates to about 5 or 6 Watts. 

The motor runs at this speed for 16 seconds then decays to nothing over 5 or 6 seconds.

 

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Guest

Mike, Jef

This post is no way a criticism of Arthur’s power unit selection for the Competitor but there is always another way……
The picture shows my Gypsy, the Competitors big brother running a 12mm brushed CN12 motor in an ‘E’  gearbox having a ratio of 10.7:1. The propeller is an 11” GWS Slow Fly with a 250mah 2s battery. Motor run was contrived using a Peterborough FET timer and the Gypsy flew a gentle free flight climb on a 30s run for 2amps / 15Watts. About 8-10 flights were possible before a recharge was called for. This model taught me the following….
1. Big, light rubber vintage models fly well on much less power than I thought possible.
2. The GWS gearbox allows the use of a large propeller in keeping with the models rubber heritage.

I suspect that this GWS setup would also fly the Competitor with perhaps the ‘D’ gearbox and a 9-10” propeller. This gearbox also accepts a Feigao 12mm brushless motor which offers 5amps and 45Watts if you really want a screaming climb. You would , however have to use the ESC and controller that Arthur used.

Regards Ian

gypsy 001.jpg

gypsy 004.jpg

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Jef Ott

My electric mini Skyleada Bantam and my Ajax will have identical systems to the Pixie (but with rc too), but I may use Ian's suggested system in my Competitor build when I get round to it, just to do something different to Dad's one. 

The beauty of the system that Dad and I used, is that virtually any brushless motor and prop of immediate availability and reasonable size (think special offers, ebay purchases, or just using up what you have) can be used to achieve any climb rate you might want, such is the flexibility of the KP Aero 35 timer. speed, time and decay controllers. Like I said, Dad's Competitor runs on about 5W, and there is another 30W+ on tap if you fancy some really hot climbs!

The system also proves very useful for tweaking the speed, to achieve the torque reaction necessary to get the turn you want under power. 

We have not yet managed to flatten the batteries in either the Competitor (nor the Pixie) such is the efficiency of the system, despite flight after flight after flight, for an hour or more, in dead calm conditions (with short retrieves).

At least 60 flights should be practically possible from one charge of a 250mAh pack!

(60 x 15seconds x 700mA = 175mAh)

 

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mikef

Many thanks to Arthur, Ian and Jef for the replies.  Useful food for thought.  I like the idea of the 'big prop' look for a model that was originally rubber powered.  I see that IPS has an 11.8:1 gearbox too....

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PeterT

Mike

GWS IPS stuff is becoming difficult to find. The last bits I bought came from Avicraft, but they only seem to stock gearbox ratios up to 10.7:1.

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Guest

Mike,

Micron have an 'F' (11.7) gearbox in their 'discontinued'  section  and there is of course the Feigao IPS rip off gearbox ...RB have or did have a 6.7:1

If you brave the US then RadicalRC will get you anything you want including the very useful low voltage EDF CN12-RLC motors.

Have a laugh...the piccy shows an early attempt to make a midmounted motor for the Gypsy (I forget why) using a g/f shaft, bits of old servo and cut up IPS gearboxes. Lasted about 2mins at full chat before it rekitted itself. Not shown is the rubber drive shaft made from 12 strands of 1/4".....TV was so awful that the rubber fried....do not try either of these suspect methods at home, they do not work but will amuse onlookers no end.

Regards Ian

gypsy_midmount.jpg

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