Mode Zero

During a recent visit to the South West, Shaun dropped in for a surprise visit! He'd been helping someone dispose of various modelling assets, and amongst them was a KwikFly 3. I immediately made an offer on it, which was accepted!

It was either an ARTF or built from a Graupner kit, and the airframe was in generally excellent condition, though it had suffered a little bit of "hangar rash". Apparently it had also had retracts at some point, though these had been removed and conventional tricycle gear fitted. This was lucky, as it turned out!

It had been fitted with an Axi motor originally, but this had been removed. I looked up the specs for it, and it was a real beast of a thing - and expensive to boot! I've found an Overlander motor that makes a very good substitute for a 60 glow motor on 6S. Both my Schluter Cobra and DS-22 fly very nicely on it, so another one was ordered. I had to hack the original motor mount around a bit to fit it, but it went in without too much effort.

The original Axi motor must have been quite heavy, as I found about 50gm of lead under the tail! This was removed, as the Overlander is much lighter. The previous owner had attached labels with the required control throws. I was a bit sceptical of these, as the control surface are real barn-doors, and I reckon it would have taken off if I'd just waggled the ailerons a bit!

The CofG came out towards the rear of the recommended range, but all the write ups indicated that it was quite tolerant of balance, so it was off the field once the weather improved enough.

That first flight was one of the scariest I have ever had! Talk about "tiger by the tail"! The first hundred feet or so was a constant roller coaster ride as I fought to keep it under control! Once I had sufficient height, I throttled it back to under half power and quickly landed it. Just as well I was wearing bicycle clips!

Back home, I reduced the aileron and elevator throws to 50%, mechanically. The next flight was better, but still very unstable. I decided it needed the CofG moving forward! Luckily, the removal of the retracts had left a nice box shaped enclosure that went from the leading edge of the wing right up to the front bulkhead. The original tailweights were wrapped up in a plastic bag and shoved right to the front, followed by and old (dead) receiver battery. The total came out around 160 gm. This moved the CofG forward by nearly an inch!

The next flight was almost perfect. It revealed a slight nose down trim, which I'd suspected on the earlier flights, but been far too busy in crash avoidance to do anything about! I landed, dialled in some up trim, and the following flight was spot on.

At present I only have one battery that fits - a 6S 4250 mAH pack. Can't quite get a 5AH pack in there. I have another on order, and it should be here on Monday. Changing batteries is a time consuming job as the wing has to come off. It clearly wasn't designed for electric power. If I was building one from scratch, I would make a hatch on the lower fuselage, between the front bulkhead and the wing leading edge - where my lead ballast is presently located. This would not only make battery changes quicker, but also help with the balance.

Hopefully, it is now fully sorted, and I'm just awaiting the weather improving so I can get out and get some stick time under my belt with it!

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Pete

Looking forward to seeing it at Ponte Pete

Every one of the original owners planes were massively overpowered. He told me whatever was recommended, he would go 50% more to be on the safe side.

Great stuff Pete! What is the Overlander Motor that you are using please?

Its a 580 kV 5055/06 (1280 watts) showing out of stock at the moment. 580 kV should give around 14,500 RPM on 6S, but in practice will be a bit less. An old skool .61 glo-engine would be around 1000 watts, and peak around 11,000 RPM - maybe a bit less.

The RPM and wattage make it an ideal replacement for a cross-flow .61. The specs suggest a 13x6 prop, but I'm running a 12x8. Most of the flight is at half throttle, only going fully open for loops, etc.

On my Webra Blackhead 61s, I used to use either 12x6 for aerobatic models or 13x6 for a large bi-plane.

That motor is the closest match I've found. I did try a 500kV initially in the Schluter helis (Cobra and DS-22), but it resulted in a slightly low headspeed - rather critical on the fixed-pitch Cobra! The 580 kV was spot on.

Basically any motor around 600 kV and 1000 watts should be perfect to replace an old style 61 glow engine (Merco 61, Veco 61, Webra, etc).

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Pete

Another fine day on Saturday, so took the KwikFly up to get some more stick-time and explore its abilities.

It has a very strong swing to the left on take-off that requires a lot of rudder correction. It is not nose-wheel alignment and needs further investigation. It also screws out of loops slightly, which may - or may not - be related. Rolls are superb, both fast and slow requiring very little correction. Similarly inverted flight. Spins are very slow! It enters (and recovers!) quickly, but once established the rate of rotation is surprisingly slow.

I was a bit worried whether the 4250 mAH batteries would provide enough duration, but after 7 mins flying, I still had 45% left. I'm upping the timer to 8 mins!

Most of the flight is conducted at around half throttle, with full power only required for loops and other vertical manoeuvres.

The second flight was much more interesting! After a couple of minutes in the air, I became aware of a loud crackling noise that seemed to be coming from the model! My first thought was fire, as it sounded just like a bonfire!

I immediately throttled back for an emergency landing. It wasn't until the last few moments before touchdown that I became aware of something amiss with the upper surface of the starboard wing!
Due to the circuit direction, and attitude of the model, this had not been visible before.

On landing, I discovered that the covering on that wing had peeled back from the leading edge, right back to the main spar!
Although not visible in the picture, it actually extends from the wing root almost to the tip! Luckily, I didn't slow it up too much on the approach, as I think the stall characteristics could have been quite interesting! In the event, the landing was totally unexciting - a tribute to the designer!

I hope to get the wing LE recovered today - with plenty of overlap! I'll also be inspecting the rest of the covering closely!

Prior to the failure, there was no indication of any issues with the covering. Quite why it suddenly failed is a mystery. As I say, a very lucky escape!

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Pete

I always thought the Kwik Fly 3 had a D-box sheeted LE Pete?
...though I had an Ugly Stik with an unsheeted wing that was really strong and survived for many years...
it had a slide-on nose-block and spent most of its time sloping - I also recall seeing a Kwik Fly on the slopes (Ron Donahue?) way before Squire Kay

I thought it did too, until I got hold of this one!

This seems to be built from a Graupner kit - or it may have been an ARTF. The build quality is excellent, though I would have done the electric conversion a bit differently. Its a pig to change the batteries!

Maybe the original KwikFly and/or KwikFly2 had a box section LE? The model feels quite light. Once airborne, it flies superbly and requires very little power. I need to investigate the yaw on take-off and the slight screwing on loops. Maybe it needs a bit of side-thrust? Its also possible that the u/c is a bit out of alignment, though it runs straight enough on my (flat!) garage roof.

More stick time needed!

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Pete

Hi Pete,
It's the same as mine; they are both the Graupner ARTF version and had a number of differences from the kit built version. I totally recovered mine due damage caused by the mouse living in it at some time but the covering was pretty well stuck in place and required some effort to get it off. It did seem more rigid and brittle than Solarspan or Profilm though.
I have the ARTF Caravelle they sold at the same time. The covering's fine on that but it has always been stored inside and never subjected to freezing temps as you would experience in a shed or garage in our average British summer.

Roll rate is steady considering the barn door ailerons but it is a brilliant plane to fly.

Mines powered by an Irvin 46 (red crankcase version) and has plenty of power to fly aero's , old school fashion. Prop hanging isn't possible but the original never could.

Shaun.

My plan-built version does have a sheeted D Box

Yes, that looks a lot more robust! The Graupner one feels very light, which is good in one sense, but it is a bit of a floater when landing - and since Devon is nearly all hills, we quite often end up landing down the slope! Not so good!

Also, most of our fields are farmland, so hardly bowling green level, and a really solid undercarriage mount is a necessity! Tail-draggers definitely preferred!



It didn't take long to repair mine. I had some left over white Oracover, which is what I suspect it was covered in originally. In any case, it was a perfect match and was flying again by the week-end.

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Pete