GK 1 ZU BLJ is flying

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GK 1 ZU BLJ is flying

Unread post by giarc64 » Mon Feb 13, 2012 11:09 am

Hi All

For those of you that are interested, Carlton (flykr) on this forum has started flying this one of a kind aerie and all I can say is that she is beautiful. She has a honda 16v water cooled engine. I too this video of him taking off at Tedderfield yesterday.

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Re: GK 1 ZU BLJ is flying

Unread post by GL » Mon Feb 13, 2012 11:17 am

Lovely - climbs well - any idea of horsepower?
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Re: GK 1 ZU BLJ is flying

Unread post by Theuns v V » Mon Feb 13, 2012 11:26 am

Well done! Hope to see it soon :D

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Re: GK 1 ZU BLJ is flying

Unread post by Roger » Mon Feb 13, 2012 11:29 am

An older article on this pocket rocket from our own Russ (Whisper):
Garth Kopke and his GK1 by Russell Phillips



There’s a saying out there about the “talkers” and the “doers”. This article is about a “doer”. In this case a young South African who quietly got on with the job of designing and developing a very unique aircraft. The chap in question was Garth Kopke – who sadly is not with us anymore (He died in a fire-bombing crash as a result of structural failure but that is another story).

Garth started building a KR2 when still at high school and some years later ZS-WJN took to the skies. This was a successful aircraft because he kept it simple and light. Garth had the usual itch for more speed and for aerobatic capabilities so it was no surprise that sketches of a sleeker, faster machine started to appear.

The new aircraft was to be a single seater with sufficient strength for aerobatics and very low drag. The issue of an engine became a problem as it is difficult to extract more than about 70Hp from the tried and tested VW’s used by so many homebuilders.

Garth decided to use a Honda 1600. The actual engine used had flown some 200hrs in my Citabria and had been dyno tested to 95Hp.

All the ingredients were now in place and all he had to do was now design and build an aircraft from scratch!

Every few months I would receive a call from Garth giving sketchy details of how he was progressing. Due to his nomadic lifestyle as a cropsprayer/ firebombing pilot these calls came from many different places. The aircraft project also moved around the countryside quite a bit.

I finally got to see the aircraft in Plettenburg Bay when it was almost complete. There is yet another saying (this time an aviation saying) “if it looks right it will fly right”. My first impressions of the unpainted machine in a dusty Plett workshop were exactly that – it looked right!

Garth was not a qualified aeronautical Engineer yet he produced a machine using common sense and gut feel that I believe would be hard to improve upon, even with an army of Engineers. (The sizing of the structural items such as spars etc were all verified by the appropriate people).


Flying the GK1

My first flight in this machine was with the normal trepidation and nervousness one has at flying something new. In this case it was really new – this was/ is the only GK1 in the world!

This machine was designed for speed and the cockpit width is based on ….you guessed it, the width of Garth’s shoulders! Headroom is also limited and there is no place for a cushion (or a parachute! – unless the seatback is modified). The nose is very long but fortunately forward visibility is not too bad as the nose is also very narrow.

The engine has no starter motor and hand propping the engine is effortless as the car engine starts easily and idles sweetly. The first impression as you open the throttle to taxi is that you are flying a turbine due to the high frequency whine and smoothness of the engine. The engine drives the prop through a toothed belt reduction drive which results in a lot less of the low rpm clatter one gets with other gear systems.

Take off is an exhilarating affair as the power to weight ratio is spectacular. The aircraft has reasonable taildragger manners with a powerful rudder. “Lift off” happens at about 70Mph and initial climb rate is in excess of 1200ft/min.

The most striking recollection I have of the first flight is the control harmony that has been achieved in this design. I have read of the classic ratios between elevator, aileron and rudder forces which designers aspire to. Some aircraft which apparently have come close to these ideal ratios are the Chipmunk and Pitts S2A. I would liken the delightful control harmony of the GK1 to the Pitts S2A. Roll rate is yet to be accurately measured but is in the order of 180deg/s making multiple aileron rolls and hesitation rolls a pleasure.

In straight and level flight the aircraft does what it was really designed for …..speed! After leveling off a quick glance at the airspeed indicator yields a pretty impressive speed but patience is required as this machine seems to take about 2 minutes to really get going. The radiator is built into the rear fuselage and has an adjustable cowl flap. Once one is established in level flight the coolant temp is monitored and the cowl flap progressively closed. The first time I tried this I could not believe the reading I was getting on the airspeed indicator. The needle was almost on the stop!! Next flight was with a GPS which verified what the gauge was reading – approximately 160kts! This is an impressive speed in a machine that is burning about 17lites per hour!

Stall speed is a low 45Mph IAS with very little wing drop. This is probably due mainly to the use of a well proven wing section (RAF 48) known to have docile stalling manners.

The circuit and landing can be interesting if one leaves the slowing down process till too late. With no flaps the only way to lose height is by sideslipping. This is also a useful way to see the runway over that long nose. A well planned approach flown at about 65Mph IAS with a sideslip works well and the aircraft touches down gently on its spring steel undercarriage. With a bit of practice landings in 400m of runway are quite feasible. Directional control during the final stages of the landing roll requires a bit of footwork but nothing that a competent taildragger flyer would have a problem with.
Construction

The fuselage structure consists of a wooden framework with plywood skins. The wings have two substantial single piece laminated wood spars. The wing has a foam core with a fiberglass skin. The one piece wing fits into a cutout in the underside of the fuselage. Ailerons employ aerodynamic balance tabs which help reduce stick forces. The canopy is a portion of a glider canopy and blends very neatly into the fuselage lines. The wheel spats are a very tight fit around the wheels and are blended carefully into the spring steel undercarriage legs. Every attempt has been made to reduce drag with even the tailwheel closely faired. The engine cowl has no air inlets thereby reducing cooling drag to the absolute minimum. The radiator is mounted in the rear fuselage and draws air in through an under-belly scoop similar to a Mustang. Workmanship on the aircraft is superb with great attention to detail. Big emphasis has been placed on weight reduction and hence the cockpit is spartan and functional.
Design goals



The end result of Garth’s efforts is a machine that certainly achieved and surpassed it’s design goals. Anyone who has considered designing and building an aircraft single-handedly from scratch will realise what a notable achievement a project like this represents.
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Re: GK 1 ZU BLJ is flying

Unread post by Glas3 ZS-VNE » Mon Feb 13, 2012 6:24 pm

Wow absolute stunning and 160knt on 95 hp 17L/hr that is the way to go :D
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Re: GK 1 ZU BLJ is flying

Unread post by cvh » Mon Feb 13, 2012 9:22 pm

where is a "like" button whenyou need one :D
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Re: GK 1 ZU BLJ is flying

Unread post by Avgas » Mon Feb 13, 2012 9:32 pm

I remember seeing Garth fly it at Nelspruit :D Way back then :wink:

It is nice to see it flying again. well done Carlton =D>
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Re: GK 1 ZU BLJ is flying

Unread post by richard C » Tue Feb 14, 2012 8:22 am

It looks a little like a Mew Gull ? very pretty.
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Re: GK 1 ZU BLJ is flying

Unread post by GlennW » Tue Feb 14, 2012 9:07 am

Well done Carlton!! Looks amazing.
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Re: GK 1 ZU BLJ is flying

Unread post by FLYGUYS » Tue Feb 14, 2012 9:37 am

Well done Carlton, looks very pretty.
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Re: GK 1 ZU BLJ is flying

Unread post by FLYBOY OBD » Tue Feb 14, 2012 10:14 am

I saw it @ Tedderfield 2 weekends ago and it looks for me like a small extra 300!Thanks Carlton for showing it to me.I love it!
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Re: GK 1 ZU BLJ is flying

Unread post by FlyKR » Tue Feb 14, 2012 5:36 pm

Thanks guys for the kind words and craig for posting the vid here on avcom. Cheers C
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Re: GK 1 ZU BLJ is flying

Unread post by Theuns v V » Tue Feb 14, 2012 6:11 pm

just looked at the vid now and that is one amazing little aerie hey! It can take off with the prop not even turning :wink: How is that for airframe cleanness :lol:

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Re: GK 1 ZU BLJ is flying

Unread post by Landbouloods » Tue Feb 14, 2012 7:48 pm

Looks good Carlton, I would love to see what changes you made, dash etc . It also looks like you've changed the exhaust manifold.
Post some pics.
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Re: GK 1 ZU BLJ is flying

Unread post by Neville Ferreira » Wed Jun 10, 2020 7:07 am

GK-1 Webpage

saturdays with Daniel dot com




Wow wow wow..... That was my first impression.

The take-off went without a glitch after keeping her on the ground until she wanted to get airborne. Climbing out at around 90Mph she felt solid and responsive. Once at around 2000 feet above the ground, 6500 amsl she settled in the cruise at around 185Mph with the engine at 5300rpm.

At full throttle, she reminds me of a racecar as the 4 cylinders reached 6000rpm. This is something to get used to after flying 6 cylinder Lycoming engines with max rpm below 2900rpm for the past 8 years.

By comparison to the modern high price tag aerobatic aircraft, this offers a kick in the pants experience that you just do not associate with an aircraft at this price tag. Where have you seen a 100Hp engine delivering 200-220Mph speeds with less than 20Lph fuel burn? Although this aircraft is not marketed as an aerobatic aircraft she is 100% capable to perform loops, rolls and any basic manoeuvres. But the fun lies in the flight itself.

This little aircraft with a 6meter wingspan requires only the corner of your hangar but once you have strapped her on you will be forgiven as she flies as well as any $440 000 aircraft.

Cruising at 185Mph I took my hands and feet off the controls and she remained stable without the tendency to pitch or bank even though she has a straight wing with zero dihedral.

On landing with an approach speed of around 55Mph she touched down and used less than 450 Meters of the runway.



We are in the final stages to start production of this amazing little aircraft. The 2 seat tandem seater will be offered with the 180Hp powered https://www.vikingaircraftengines.com option while the single-seater option powered by 100-130 Hp engine from the same company.
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