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Old May 29, 2014, 07:26 AM
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United Kingdom, England, Frome
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Electrifying the Keil Kraft Chief

ELECTRIFYING THE KEIL KRAFT CHIEF

If you were a schoolboy or an RAF Air Training Corps cadet during the fifties and early sixties, these type models were in every model shop. Names like Veron, Mercury, Frog and of course Keil Kraft would put your imagination into overdrive. Radio control was in it's infancy and very expensive, therefore some of these models had very cunning devices to keep them under control. Devices like de-thermalisers, where the tailplane pops up at a pre-determined time, (normally 5mins. for competitions), and the model descends in a series of gentle stalls in order to stop you loosing the model in a thermal. They were so light that they seldom damaged themselves on landing. Or automatic rudders, like the Chief, which activates after launch to get the model to fly in a gentle turn. Late summer evenings was normally the best time to fly these models when the wind has dropped and thermals died down, all ways of loosing your masterpiece.
Of course there were plastic models from manufacturers like Airfix & Revel, but these models did not fly very well.. When finished they just gathered dust and some times literally flew of the shelves if mother was careless with a duster They were, however a very good way that a young air cadet could get to know the names of all the parts of an aircraft and learn Port from Starboard.
We soon progressed to flying models. From a very young age I remember looking at the Keil Kraft Leaflet a thousand times and in particular the Chief, this model had a massive 64 inch wingspan! With a tape measure spread over the floor at 64 inches it seemed huge. Today it would be considered a 'tiddler', especially by my fellow LMC members. However at that time it was just about the ultimate Keil Kraft glider. As we get older though, the models get bigger, some of us progress to 1/1 scale. Those are models that you have the inconvenience of having to sit in them to fly and the disadvantage of seldom walking away from accidents!
As a schoolboy I built many Keil Kraft models, (part of my aeromodelling 'apprenticeship'), but not the Chief, but now thanks to the UK's Vintage Model Company I can build one now. The Chief with it's long nose that seemed tailor made for a 3s Lithium polymer battery and an electric motor, is an excellent candidate for Micro RC and electrification.
The VMC kit is much as the original was with the same plan and bits, with one exception, the parts are laser cut. Some original Keil Kraft models were die-cut but not many. Most of the time the parts were just printed on the balsa and you had to cut them out with a modelling knife.
With laser cut parts they just need to be 'teased' out of the balsa sheet, they are very accurately shaped. The only problem you might get is that the burn marks can sometimes show through the covering. A small price to pay for such beautifully shaped parts.
The aircraft is of course a 'free flight model', yes, you just launch it and let it go! Therefore, as with all free flight models the Chief is self stabilising thanks to the polyhedral wing. That is, if a gust of wind hits from the side or causing it to pitch or roll it will endeavour to stop this from happening and correct itself. The same effect can happen if we try co turn the model with radio control, it will try to prevent this from happening and the tail will start to wag from side to side. The outcome of this is called 'Dutch Roll', a common problem with rudder steered aircraft. A simple fix for this is to fit ailerons. Not an option, I think, with the Chief. Alternatively you could reduce dihedral/polyhedral, which gives it it's stability, by about 50%, (wing root and wingtips).
For covering I used 'Airspan', this material is almost indistinguishable in looks from tissue, but much stronger. It shrinks well around shaped parts, much better than 'Litespan' does. Airspan does not necessarily require doping. If you need to use dope one coat should be enough, it will however become more brittle and more easily punctured. I covered the nose section with some Solartex off-cuts, this is the bit that thumbs can penetrate when launching!
You could, of course build and fly the model free flight just as it would be done in the 'fifties'. Why not!
I decided however, to take advantage of modern R/C equipment and motor/battery technologies that are currently available, which would be considered science fiction in the fifties.

Other R/C modifications:

1). With the extra weight from the battery, servos, RX, ESC and the motor, (double the normal weight) the balsa wing spars need to be replaced with spruce and webbing just to be on the safe side.
2). Elevator, (snake) and rudder, (closed loop), system fitted for R/C control.
3). Interior of nose lined with liteply, to hold the Li-Po battery and motor, with access hatch fitted.
4) Underside hatch to access servos, if you wish.
5). The original had 'crash proof plug-in wings' with no retention. For our heavier model hook and elastic retainers seemed necessary. With a two-piece wing I found that when under load the dihedral increased causing 'tail wag', and the start of 'Dutch roll'. You may wish to convert the wing to one piece, with a suitable wing joiner built into the spar and change the fuselage construction accordingly.

R/C & power conversion specifications.

New weight: 31oz. ( free flight original 14Żoz.).
Wing loading: 8.66oz/sqft, (free flight original 4.05oz/sqft). Still good.
Motor: 960Kv 480 brushless outrunner.
ESC: Eflite 30amp Pro.
Propeller: 10x6 Graupner CAM Folding Prop.
Receiver: Spektrum AR6115e
Servos: Hitec HS65HB x 2, or similar.
Battery: 2200mAh 11.1v 3S Li-Po
Covering: White Airspan, (nose area covered with Solartex) .

Flying the Chief

With this power configuration, at full power the thrust is very noticeable, the aircraft needs little effort to hand launch and will climb at quite a steep angle. You will need to decrease power.
At the desired height the motor can now be 'cut' and the prop will fold. In this case a folding prop with a 'brake' on the motor is a necessity, a 'windmilling' prop makes an excellent airbrake.
With the present wing configuration, (50% reduced dihedral/polyhedral and a one piece wing), turns are very smooth, with little or no tendency to yaw from side to side. Final glide is long and flat. With no airbrakes you will need to ensure that you have plenty of room to land, especially in calm conditions.
Longest flight so far is about 45mins, using an occasional 'blip' with the throttle and little assistance from thermal. Despite the extra weight the Chief is still best suited to calmer wind conditions or perhaps on a 'ridge' in a gentle breeze.

During my aeromodelling career I have built many models large & small including ╝scale. Oddly enough though, these VMC models are in some way just as much fun with the 'pressure' of a mishap off. Maybe we have lost something over the years. A 'Keil Kraft' image search on any search engine should reveal old Keil Kraft leaflets pictures etc.

Other conversions completed: Keil Kraft Halo. But that's another story.

Where to next, I wonder? Still on the theme of miniature RC aircraft, what is now required is a model that can cope with windier conditions, is aerobatic and can be taken on vacation without taking up too much room in the car. I think the late Dereck Woodward's VSP, (Very Short Plane), would 'fit the bill' and could double as a sort of flying memorial to a great modeller....

DW.

Useful links: http://www.vintagemodelcompany.com
http://www.solarfilm.co.uk
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Old May 29, 2014, 07:50 AM
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Bradford West Yorkshire, UK
Joined Apr 2010
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I before E except after C.

Don't work with Eddie Keil s name though.

Nice description David.


Impala at 52" looked big and OMG when I built my first 100" !!!!!!!

Regards Ian.
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Old May 29, 2014, 07:51 AM
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Staffs, UK
Joined Nov 2003
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Quote:
Originally Posted by davidwright View Post
A 'Kiel Kraft' image search on any search engine should reveal old Kiel Kraft leaflets pictures etc.
Interesting conversion but you'll find searching for "Keil Kraft" will work better. Though I'm sure the late great Eddie Keil would forgive you for continually getting his name wrong .

Steve
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Old May 29, 2014, 08:15 AM
Sticks, Tissue & old Diesels
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France, Centre, Amboise
Joined Nov 2011
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This is an imminent "near future" project for me. Mine will be totally traditional (tissue and dope) and the only mods will be for minimum RC & electric, plus a little reinforcing of the known Chief weak spots (wing attachment and mainspars).
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Old May 29, 2014, 01:28 PM
So I'M meant to be in control?
Colonel Blink's Avatar
Ilkley, West Yorkshire, UK
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Quote:
Originally Posted by brokenenglish View Post
.......the known Chief weak spots (wing attachment .....
I have no idea what you are on about.....
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Old May 30, 2014, 01:44 AM
KNS
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nice!
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Old May 30, 2014, 02:07 AM
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United Kingdom, England, Frome
Joined Dec 2012
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Thanks Guys.

Chief weak spots (wing attachment and mainspars). ref. brockenenglish.
Please see the Vintage Model Companies own description of the Chief and the accompanying vintage video from the 60's. That says it all.

DW
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Old May 30, 2014, 02:26 AM
So I'M meant to be in control?
Colonel Blink's Avatar
Ilkley, West Yorkshire, UK
Joined Nov 2008
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To qualify my last post, see paras 7, 8 & 9 on my blog:

http://www.rcgroups.com/forums/showthread.php?t=1770198

Looking at the video referred to it looks like the towline was still attached, so probably the same thing happened there - it certainly has some familiarity (apart from the Jag and the colour cine camera - they must have been rich!!!)

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Old May 30, 2014, 06:12 AM
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A familiar story

Hi Colonel Blimp.
Your story sounds all too familiar, but a good read.. highly recommended to anyone reading this blog. The rush to get the A/C built and then when finished too scared to fly it. Mishaps happening, like a KK Topper that dived vertically of the launch where I put the Cof G in the wrong place and a KK Dolphin that disappeared in thermal.. still flying for all I know. But I think you'll agree, time over we would do it again.

Hope all is well.
DW
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Old May 30, 2014, 06:46 AM
So I'M meant to be in control?
Colonel Blink's Avatar
Ilkley, West Yorkshire, UK
Joined Nov 2008
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Quote:
Originally Posted by davidwright View Post
But I think you'll agree, time over we would do it again.
Indeed - in fact that's sort of the driver that got me back into aeromodelling in the first place, with a KK Ajax converted to RC & electric.... followed by a KK Gypsy. I've enjoyed every minute stolen from real life!!

I'll admit to having a hankering to build an Invader or Topper with twin outrunners.....
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Old May 30, 2014, 07:16 AM
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I'll admit to having a hankering to build an Invader or Topper with twin outrunners.....[/QUOTE]
A topper with twin outrunners, sounds good to me, I'll look forward to the video.
On the subject of videos, thanks for the ride in the Gypsy, It felt that I was actually sat in it.... Brilliant.
What camera did you use?

DW
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Old May 31, 2014, 12:39 AM
So I'M meant to be in control?
Colonel Blink's Avatar
Ilkley, West Yorkshire, UK
Joined Nov 2008
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Quote:
Originally Posted by davidwright View Post
Thanks for the ride in the Gypsy, It felt that I was actually sat in it.... Brilliant. What camera did you use?
David - it was the ubiquitous 808 #16 keychain camera with (if memory serves me correct) the D lens, bought from eletoponline on ebay:
http://www.ebay.co.uk/itm/Mini-DVR-8...item2a20b389dc

I simply velcroed it to a tongue depressor which I held on top of the nose with elastic bands....
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Old May 31, 2014, 01:46 PM
So I'M meant to be in control?
Colonel Blink's Avatar
Ilkley, West Yorkshire, UK
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Originally Posted by davidwright View Post
A topper with twin outrunners, sounds good to me, I'll look forward to the video.
Talking of which does anyone, anywhere, have the printwood for the KK Topper that they could scan and make available????
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Old May 31, 2014, 02:02 PM
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KK Topper

Hi
Try this link:
http://www.outerzone.co.uk/plan_details.asp?ID=1402

or of course the VMC.

DW
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Old May 31, 2014, 04:55 PM
So I'M meant to be in control?
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Thanks David - last time I looked the printwood wasn't there. Never ceases to amaze me how generous and helpful people are in this hobby!!
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