Category Archives: My planes

Killer Kaos restomod part 6

It was one of those incredible warm and sunny august afternoons, with clear blue skies and just a hint of a breeze, and I brought my daughter along and went flying. We were alone at the field when my Killer Kaos crashed spectacularly.

I tuned the engine. At first it was flooded, and that killed the OS #F plug, so I replaced it with an OS #8. At home, I had shortened the pipe by cutting the header a good 2 centimetres. It worked. The engine ran strong, frighteningly so, as I tached it at 11.200 rpm. Glad I ordered bigger props, I thought, as I took off. Immediately it started leaning out, not providing the power the tachometer promised when on the ground, and I landed a minute later. The engine was piping hot, it oozed heat and I scorched my finger touching the head. I was at a loss, and then I remembered:

The engine was bought used, and when I got it, it was full of burned Castor oil. I always use 15% nitro and 15 % Aerosave pure synthetic blend in my engines. Problem is, this engine was brought up on low nitro and Castor oil and it was made in an era long before the AX-series engines I’m used to now. So I switched fuels, draining the tank and putting in 10 % nitro fuel with 18 % synth/Castor blend oil. The difference was amazing.

It screamed. I was able to turn the needle almost one full turn out, and power and smoke just kept coming. Simply unreal. Delighted, I took off into wind, and the Kaos was tooling along the blue skies like a dragster down the strip, a gorgeous white smoke trail in its wake. It just hauled upwards like nothing else mattered, and I got that incredible, indescribable rush of pure joy and I wanted nothing more than to hammer the throttle and roll upwards until the cows came home. Then it blew up.

I knew it was flutter before my brain even processed it. The elevator boomed for a second with such ferocity, it even drowned out the sound of the engine. I startled so that I pulled the throttle back as pure muscle reflex, attempted a turn towards home, and realized only the ailerons worked. It wobbled, stalled and then went in nose first. It only lasted two seconds.

The engine was buried 10 inches in soft soil. The fuselage from the rear wing mount forwards was smashed. The fuel tank, receiver, two servos, battery, everything smashed. One wing half in pieces, another crushed. Incredibly, the header and pipe seem undamaged. But the plane is a total loss.

The elevator fluttered. No doubt about it. There is a gaping hole where the elevator horn was, and the carbon rod broke where the threaded rod was screwed into it. The horn and link is missing. It’s one of the very few planes I’ve had over the years with a single elevator pushrod, and it will be my last.

I’m really sad. I was in heaven, truly enjoying myself and thinking that wow, this is what all those hundreds of hours in the basement is really all about. The sound, the smoke, the goose bumps you get when you pull up and the plane, your creation, just keeps on going. And then nothing but silence and sorrow.

I’m also grateful, now that the shock has passed. Grateful that a lot of expensive parts survived. Grateful that I had those few minutes of pure pleasure in the skies before it was over. Grateful that it landed in a field and did no harm to anyone. Grateful to have had this plane. I always wanted to fly pattern, and this was the first plane I had that didn’t crash. I flew it in its original version for four seasons, and it really taught me to fly pattern. It inspired confidence, and I felt it even today, that my fingers could do nothing wrong with it. It was… solid. A rock.

The only way to relieve my sorrow is to look ahead. My decision was already made as I walked to the crash site: I will build another. It will take a while, as is my custom, but I have already started to plan my next one. I will build it from scratch, I have my original plan, and using bits and pieces of the wreckage as templates I will build a new Killer and fly it like there’s no tomorrow, and as a homage, the new one will carry one single wing rib from the original with it into the skies.

So long my friend.

Yoshioka Aladdin update

The wonderfully strange Yoshioka Aladdin 45L that I built in the autumn of 2012 has finally flown, after hanging on my wall for almost three years (That’s what family life can do to ones hobby). The first flight was highly successful. After some trimming, it flew hands off straight and level. The engine, an old but well looked after YS .63 FZ ran rich but did not stop. It has ample power, it’s not a rocket, but it pulls it along with enthusiasm. The sight of the sleek plane with the fourstroke sound was very strange. It looks like a pattern plane and sounds like a scale model.

The Aladdin has a very strange feature, an offset engine installation. It is explained in the poorly translated Japanese instructions that mounting the engine like this does not require any right thrust. It looks very odd, and gives the plane its trademark appearance. See here:
Offset! It’s mounted 90 degrees to the models centreline. The benefit, apart from the obvious fact that the engine and muffler are almost completely buried in the cowling and not hanging out the side, is that right thrust will vary with engine RPM, and this setup will not. I have just the one flight, but I could see no apparent problems in the air, it certainly flew straight enough. Perhaps it really does work? But if so, why haven’t others done the same? Comments?

Here are the build photos.

Killer Kaos flies (restomod part 5)

2015-08-05 21.37.44

The O.S engine gave me a little headache. I ran it at home a little bit, and it ran strong and started like any O.S motor should, i.e. with a light flip of the prop. It tached 10.000 rpm on the APC 11×12 and idled smoothly. All was well and then I tried holding the nose up, and it leaned out badly. A lot of tweaking later, I was unable to fix it. I re-did the fuel plumbing and moved the tank a lot further forward and hoped that would solve it. It may have been optimistic having the tank as far back as I did without using a pump or header tank.

On the field yesterday I had exactly the same problems. I switched from an O.S 8 plug to an OS F, and that did nothing. I tried a smaller prop, an 11×9, and that helped a bit. I then tuned it some more and eventually it ran strong. I had one flight where I landed early because I could hear it leaning out a bit in loops, tuned more, and then suddenly it ran like nothing else mattered, not missing a beat going up, down, sideways or anything. Success! The third flight was suddenly bad again, leaning out. Landed in a hurry, tuned, and suddenly it ran great again.

I have a successful track record of making stubborn engines run good, and I don’t intend to let this one beat me. I suspect the pipe is slightly too long, and I think shortening it might do the trick. I will also try an 11×10 to load it up just a bit more.

The plane flew just like you’d expect. I had some wild deja vu’s while flying. I have lots of flights on the old version of it, so it behaved as I remembered, which is a strange sensation when I was mentally prepared for a maiden flight! I was also surprised at how well behaved it was on takeoff and landing, and how well it tracked straight and level. It has no vices whatsoever.

Here’s a before/after photo, with at least 13 years between the two:


All the pictures from the project can be found here:

The restomod project blogposts:
Restomod part 1
Restomod part 2
Restomod part 3
Restomod part 4

Killer Kaos restomod part 4


The Killer Kaos is covered and painted. I used Tamiya Lexan spray cans to paint over the white Oracover. Before painting, I gently scruffed the Oracover with 1000-grit sandpaper, which makes it less glossy without scratching it.

Tamiya lexan spray paint covers well and is easy to work with.

To avoid paint seeping under the masking tape like shown above, here’s a trick I use:

Spray a coat of clear, flat paint first. If any clear paint bleeds under the tape, it won’t show, and it fills the edge so that the color coat will not bleed under. 

A perfect result

The undercarriage looked completely hopeless.

I cut the legs and added a pair of Great Planes axels. It now sits lower and has a perfect stance with clearance for up to 12 inch props.

Tettra 55 mm wheels look great

I repainted an old field box to match

Some stickers


Next up is hooking up the control surfaces in the tail, mounting engine and pipe, and the tank plumbing.

Killer Kaos restomod part 3

The finished radio bay in the fuselage

My favourite part of any build is the pushrod mechanicals, the electronics and engine installation and so I take my time getting it as perfect as I can. I ground out a huge cutout for the Tettra 400cc tank in the fuselage former. The tank would fit in front in the tank bay, but I wanted it further back in order to not have the CG shift in flight due to the tank being emptied.

The Tettra 400 cc Crank Tank fitted. 

The servos were moved forward from their original position and the battery sits behind them, in order to fix a CG issue that the plane had back in the day. Because of that, the pushrods had to be lengthened. I wanted to stick with the original Carbon Dubro pushrods that were already in there, so I simply added a longer threaded rod that extends a bit into the pushrod inner and outer tubes. It adds a little bit of weight, but it adds it behind the CG where I need that weight, and as a bonus it stiffens everything up a little more. BLS451 servos were bought very cheap from a chopper guy switching to HV gear. They are great servos, so I get them whenever I see them up for sale. The throttleservo is a Dymond metal gear digital midi.

To top everything off, I fuel proofed everything using flat black enamel paint, which also looks cool. I’m very happy with how the interior bits and pieces turned out.

The radio bay. Note Tettra switch mount bracket

The aileron linkages. I used a pair of trusty old 9154s that have over 400 flights but are still pretty solid. I added plywood inserts to the ailerons so that the screws have something to bite in. I shortened some Futaba servo screws to fit, as I didn’t want anything visible on the upper side of the ailerons.


The O.S .61 SF engine was fitted in order to get the throttle linkage hooked up. The intake is finished. It’s a lot of motor for so small a nose. 


Killer Kaos Restomod part 2


This is part two of the Restomod-project. Check out the new tail (above). I made a new fin and rudder, new elevators and modified the stab tips to make everything nice and uniform. I wanted to get rid of the pointy, tall fin and elevators. It’s not radically different, but a lot cooler. The fin and rudder are almost 2 cm lower, something that will tie in nicely with the overall stance of the plane when it’s done. I have more changes in mind!

This has been a tough decision, but I’ve decided to go with a standard Kaos 40 canopy (The plain Tower Hobbies $3 canopy) instead of the long Killer Kaos canopy. It’ll be a whole new look. I wanted to loose the 1990’s styling, and this just looks a whole lot cooler!

You can see comparisons of the old and new tail, plus how it looks with the old canopy compared to the new one in the builds photo album.

Supra Fly 25 resurrection

I built an old Supra Fly 25 from the OK model kit in 2002, flew it with an O.S 40 LA, and stored it away when the engine was sold. I came upon a new-in-box O.S 32 SX engine in the summer of 2013, and I put two and two together, literally. What a match! The airframe was still as solid as when it was new after all that time in storage, it just needed a good cleaning. I treated it to some more color on the wings and a dozen stickers to liven it up a bit.

Inside, it got a new CG-mounted fuel tank, a whole lot of stuff removed with the dremel, and new digital servos snugly fitted to a carbon tray. But there was no cowl! I had the old one, but it was A) not original, being taken from a Supra Star, and B) had all the cut outs for the engine and muffler in all the wrong places. I was unsuccessful at moulding a new one and so ordered a Great Planes Escapade 40 cowl. It was too deep and too high but I managed to cut it in half, join it again and shorten it, before repainting it yellow with red trim. It fit perfectly!

An underslung Hatori tuned muffler finished it off nicely, and I look forward to flying my old friend with all new equipment this winter.
This is the way it looked in 2002, and this is what it looks like now.

Curare update

The 2013 contest winning Curare ARF was badly treated. In order to win, I practiced intensely two days before the contest and ignored signs of worn bearings. The engine quit and I landed nose first into tall grass. Broken header, bad bearings, broken nose gear. With no time to spare I managed to patch the cracked header using silicone tubing, screwed the nose gear in the lowered position and tried not to think about the bearings. It held together for 2,5 flights, enough to win my first contest.

Now for the overhaul. A new setup is costly and I decided to retire the engine and buy a new one. A new header was ordered as well. The nose gear was not that easy, I could only buy a trike set and not a single replacement nose gear motor, so to save on my budget I bought a cheap Hobbyking set. I should have known better, they fit poorly and I had to shim the mount to get sufficient height. Anyway, It’s on and it works.

With the removable cowl the overhaul was easy. However I noticed that the firewall had also come loose. All the glue joints were cracked and it is a testament to the build quality, the notches was all that held the engine for three flights, and I never noticed a thing. It was simply a matter of gluing the joints, and there it was – completely overhauled and ready for a new season that I very much look forward to.

Curare wins F3A retro contest

The Curare Trio: Me on the left with my Schweighofer Curare ARF (glow), Ingmar Svensson (middle, third place) with his scratchbuilt Curare, and Ola Maltesson on the right (5th place) with his new Schweighofer electric Curare.

The Swedish/Norwegian border cup is back, and our Swedish neighbours hosted a three day F3A event at Lilla Anrås airfield just outside Fjällbacka on the beautiful Swedish west coast. The event started with an informal retro-F3A meeting on Friday. Designs older than 20 years were allowed to enter the competition. Electrics were allowed, but got a 10 % penalty due to “the silly noise”…

Ola Maltesson getting ready for his third flight, Conny Åquist carries his Curare

The nostalgic event was hosted by Mikael Nabrink, Ingmar Svensson and Conny Åquist. The “Curare Cup Normal” schedule was flown, and it worked well. It’s easy to fly but hard to master, so there’s something in it for everyone.

Ingmar Svenssons immaculate Curare with Webra 61

Three pilots flew Curare. Two were Schweighofer ARFs. Ola Maltesson flew his brand new electric Curare, and former World Championship contestant (1989) Ingmar Svensson flew his immaculate model built from MK plans. He used an old Graupner 6014 radio from the 1980, converted to 2,4 Ghz, and a Webra Speed .61 engine. Truly nostalgic! Ingmar flew the most precise figures, but had fuel tank problems and had to land dead-stick after two short flights. He came in third place following his great third flight.

Ola Maltesson used his new electric Schweighofer Curare to win 5th place

I flew my glow-powered Curare, and it performed well for the first two rounds, despite having undergone hasty repairs to the cowling and having a cracked exhaust header. I also damaged the nose gear two days before, so I had to fly with it locked down (nobody noticed!). In the final round the engine quit with ruined ball bearings, and I had to land dead stick. It was a worthy end to its hard life with full throttle and much Nitromethane – I won the contest and could take home the fabulous Asano wooden prop signed by Hanno Prettner.

First price – Asano propeller signed by Hanno Prettner

More pictures here

Hanno Prettner Curare ARF part 3

The final part of the build is the engine and pipe setup. This is usually time consuming with a lot of alignment, but I found that not to be the case here. One evening, and you’re done!

The firewall and tank area is 100 % ready from the factory, fully fuelproofed. Even the blind nuts for the engine mount is installed. No epoxy has been allowed to ruin the threads either, they have been very carefully covered with tiny pieces of masking tape!

The O.S. .55 AX engine is mounted. (Note the nose gear electric motor protruding through the firewall). Just bolt on the engine mount, and drill holes in it. My only grief here is that I did not find any measurement in the manual regarding distance from firewall to the back of the spinner, so that I could position the engine correctly. Trial-mounting the cowling solves this. By removing the cylinder head (you have to do this later anyway), you can slide the engine in and out with the cowling on to determine the correct position. All hardware for mounting the engine is included, right down to the last washer. The throttle linkage fits in a ready made slot in the tank tray, you just have to drill a hole in the firewall, and the resulting linkage is nice and straight.

The fuel tank comes next. It is included, it’s decent quality, and it fits like a glove. It’s large, and it needs to be -a piped engine burns a lot of fuel. The tank tray is installed, and has cutouts for straps. These are not included, so I used spare helicopter battery velcro straps. Fit some soft rubber sheet under the tank (to prevent foaming) and strap it in place.

The straps are slung around the nose gear cable to hold it firmly in place.

Tuned pipe
The pipe is next. It turns out you can’t buy a decent header/pipe combo at just any hobby shop these days, so you need a specialty supplier. Many experienced modellers might still have suitable headers and pipes in their drawers. The days when Hatori produced 2-stroke headers for just about every plane in production are over, but you can still get hold of a #400-series 2-stroke pipe in certain places. I opted for the so called Purple Pipe combo made and sold by Just Engines in the UK:

This is the contents of the medium size Purple Pipe Combo, that fits 40-50 size engines. For a very reasonable price you get everything you need with a 1-click purchase. The three-baffle tuned pipe, a header, silicone coupler, straps, pressure tap, screws and a pipe mount. You can choose three different widths for the header. The wide header is the best suited for our Curare. While our engine is a .55, you do not need the big 60-pipe. It will be too large for the plane and too long for the engine. And clever readers will notice that Purple pipes are no longer purple in color…

The header is fitted. It clears the nose gear perfectly. I bent it ever so slightly outward by hand (it’s aluminium) to get the radius 100 % correct.

The pipe mount is ready. This is a very simple Dave Brown pipe mount. I shortened it a bit, used the offset mounting option, and it fits beautifully. To secure the mount to the wing, I carefully drilled a hole in the center spar, threaded the hole, saturated it with thin CA, and screwed it in.

Note: Engine trials done after the pictures were taken proved the header to be too long, so I sawed off about 3,5 cm. using a metal saw.

And that’s it! Nothing to it. When the engine and pipe are in, you must Dremel a large opening in the cowling to clear the header, carb, cylinder head and needle valve. It seems brutal to cut out almost a third of the beautifully painted cowl, but when it’s done you can enjoy the sight of the beautiful O.S engine hanging out. It tops off a very nice looking plane.

Weight and equipment used
The ready to fly weight of just 2.93 kg for my model is nothing short of incredible. A decent Curare could weigh in at over 4 kilos in back in the day. The target weight of 3.1 kg is within reach for all builders of this ARF, regardless of equipment used. I built this plane like a would a 2-meter contest model, saving weight whenever possible. For an ARF, that means using glue sparingly, and fitting strong 40-gram digital servos. Using mini servos for flaps and throttle saved further precious grams. I used a Futaba 9650 for the flaps, Futaba S-3151s for ailerons, and Futaba S-3050 and 3172 HV for elevator and rudder respectively. Ideally, I would have used S3050s or even BLS-551’s all over, but I had all these lying around. The electric retracts has an operating voltage of 4,8 – 6 volts, so that excludes the use of HV-equipment. My 2200 mAh NiMH RX battery could be exchanged for a lighter 4-cell 1000 mAh pack, but the CG was spot on with the heavier pack. Higher voltage also means faster servo response and less current draw.

Ready to fly – almost. There’s still all the servo programming to do, and we’ll get to that in part 4 – I’ll show you a few videos of the plane on the workbench, demonstrating undercarriage operation and the different control surface mixing.