Chocofly JS3: FES Fuselage

I’ve been mostly flying my Chocofly JS3 on the slope. For my club’s airfield I have my scratch-built JS3, which is lighter and has more wing-flexibility (allowing for awesome thermalling). But I’ve very much grown to like the Chocofly JS3 and am keen to give this one a go at our club’s airfield as well. Unfortunately, our club doesn’t allow the use of impellers or noisy motors – it’s in a very quiet and sensitive area. To enable me to fly the Chocofly JS3 at my favourite airfield I thus ordered a 2nd fuselage a (long) while ago.

The 2nd fuselage arrived a few weeks ago. It’s in the usual excellent quality. Initially I considered installing a landing gear, but in the end decided against it. The reason is that I’d like an even lighter version of the JS3 for situations where lift is very bad, especially in early spring or late autumn. My Chocofly JETEC JS3 weighs around 6.8kg, my scratch-built one around 6.6kg, the Chocofly FES Edition will hopefully end up under 6kg.

The fuselage didn’t need much work to finish. I installed the FES with my usual method. I used the outrunner and ESC combination that I’ve been using for just about every build in the last few years, a Dualsky XM5060EA-14SE with a Castle Lite 100 ESC. On recommendation of Dani (Chocofly) I went for an 18×10 GM scale Propeller and the usual Freudenthaler 43mm scale spinner. The result looks really good. The fuselage is now ready for its maiden flight – once I receive a new set of winglets (see previous post)….


Chocofly JS3: losing the winglets :-(

We’ve had some really good slope conditions over the past few weeks and I’ve been mostly flying my Chocofly JS3. I just love this glider. It’s my favourite choice if the winds are weaker or, as often happens in summer, when you can expect sudden gaps in lift. The JS3 will allow you to battle through low-lift episodes much better than most of my other gliders.

The many hours on the slope however also showed that the JS3 does have an upper limit in terms of speed. I own an early production version of the lighter GPS edition. I prefer this version as the lower weight and somewhat more flexible wings give it better thermalling properties. But it’s not made for vertical drops, tight loopings and ultra-high speed passes – I own other planes that are (including my other favourite, the Chocofly Diana2!).

The slope conditions were at times however just too good not to test the JS3’s limits. We’ve done multiple high-speed passes at well over 260kmh, but noticed that the winglets were starting to get a bit “noisy”. Ever since I lost the winglets of my scratch-built JS3 in Autumn last year I’ve been keen not to push my JS3s too far. But due to a stupid combination of unfortunate circumstances (of which I am to blame) I ended up in a steep dive with a brief loss of signal. The speed of the dive (260kmh) and the sharp recovery turn out of the dive were a bit too much for my JS3. Upon landing, I noticed that I lost my winglets. I always attach them with a strip of tape over the top and nose of the wing, but they were literally “torn out” of the outer wing, damaging a few cm of the underside of the outer wing. Fixing this is not a big issue and a new set of winglets has been ordered, but I promised myself and my JS3 that I will behave in the future….really!


Chocofly JS3: testing the short wing version (4.28m)

Although I built a short-wing (4.28m) version of my scratch-built JS3, somehow I never got around to flying it. The long version (5.14m) simply flies awesome so I’ve never seen the need to install the short outer wings. Plus the short version doesn’t quite look as good as the long-wing version.

Chocofly also offers its JS3 in the long and short outer wing version, but I only ordered the long outer wing version. A few weeks ago Dani (Chocofly) put his set of short outer wings in my hands and urged me to give them a try. We’ve had some awesome slope conditions in the past few weeks, so I did. My impressions confirmed what Dani told me: it’s a very different plane. The JS3 becomes very agile (rolls great 🙂 ) but at the same time doesn’t seem to lose much of it’s thermalling capabilities. It’s a nice addition to the JS3 that extends the range in which the glider can be used to conditions with stronger lift and wind and where the pilot wants a more agile plane.

For me, the JS3 already had the broadest range in which a glider is excellent to fly. I’ve never flown a scale glider that is so good to fly and so much fun in conditions with very little lift way up to good slope conditions. The short outer wings further extend this range upwards. Interestingly, I did notice that the JS3 accelerates faster, but I did not notice a large difference in the top flying speed (see my next post). Important to note however is that even in the short wing version it doesn’t match the Diana2, which is still my favourite plane for good to excellent lift conditions. This in partly because my JS3 is the lighter GPS edition (and thus not as robust and heavy as the Alpine or HG Editions – my Chocofly Diana2 is an early Alpine Edition), but also because of the winglets – which limit the top speed of the JS3 (the Chocofly Diana2 comes with a set of “tiplets” for when it really gets “hot”)(see my next post). That’s however no criticism of the JS3 – it’s an amazing plane for the slope, but not built as a slope racer. I very much enjoyed flying the short wing version and have ordered a set of short outer wings.

Below a few pictures of the short and long outer wing version side-by-side.


Scratch-built JS3 with new winglets

Last year was not a good year for either of my JS3. After the incident with my Chocofly JS3, which is fortunately flying again, I also had some bad luck with my scratch-built JS3 in September. We were racing triangles at our airfield in some of the most amazing thermals I’ve ever encountered, with a thunderstorm and heavy clouds coming in. I misjudged the height of the cloud coverage as well as the strength of the thermals. My JS3 was literally sucked into a dark cloud. I instinctively gave down elevator, which caused my JS3 to reappear within seconds. Unfortunately it picked up speed massively (my GPS logger later told me I hit 265kmh) which caused the winglets to flutter and torn out of the wings. After a quick check that all control surfaces were still functional, I managed to land the plane safely. The winglets were never found, and there was quite a bit of damage to the end of the outer wings, but fortunately nothing that could not be fixed.

Chocofly kindly provided me with a set of moulded JS3 winglets, which fit perfectly, saving me the task of making them myself. Fitting them and fixing the outer wings took a bit more work. Two weeks ago I then also finally managed to get the wings spray painted and today my JS3 happily took to the skies again, flying as good as ever. I love this plane.


VT-16 Orlik: Maiden Flight

Yesterday my VT-16 Orlik had its successful maiden flight.

The day proved to be quite eventful. As usual we do the maiden flight in aerotow – which again proved to be a good decision. Even though we did extensive pre-flight checks, we somehow oversaw that the elevator wasn’t quite neutral and slightly up. As soon as I released the Orlik from the towline at around 250m I had to give a LOT of downtrim, after which the plane was flying ok. Also challenging were the crow (butterfly) settings. I installed and programmed the inner wing control surface (brake flap) to allow it to come down by around 75 degrees. This proved to be a bit too much, as (unlike some of our other builds) the plane responds very well to crow. In addition to that, the Orlik also needs a lot more downrudder in butterfly/crow than with our other builds. This meant that the Orlik came in too slow for the first landing and stalled around 30cm above the landing strip, literally dropping out of the air. Fortunately nothing happened. A quick reprogramming and further finetuning during subsequent flights cleared all problems.

Unfortunately that wasn’t all the excitement of the day. During my 7th flight I lost the canopy after engaging the motor for a short climb. We found it back after a long search in the already high wheat and I could have a final good flight at the end of the day. To add to the events of the day, in the late afternoon Georg’s Orlik also had a really nasty looking mid-air collision with the glider of a colleague. Both gliders however landed safely with barely a scratch.

I like the Orlik. It’s the pleasant oldtimer that we hoped it to be. It thermals very well, responds very well to rudder and needs little aileron in curves. It also has excellent stall behaviour. Of course it’s not a racer – and wasn’t built for that – but does pick up speed nicely with negative camber. I plan to fly it a lot in the next few weeks and further finetune settings and the center of gravity.

 


VT-16 Orlik: Ready for maiden flight

My VT-16 Orlik is ready for its maiden flight. Three rainy days off meant I had time to finish installing the wing servos and finalising the wiring and programming and getting the center of gravity right. Getting the CG right proved a bit harder than I hoped. The fuselage of the Orlik is very long, and the nose very short. I had hoped that my two larger 3S batteries (2x 3S 3700), a small backup battery and the Dualsky outrunner motor would be enough to get to the CG. Unfortunately I’ve had to add a bit over 200gr of weight to the nose. The surprise however came when I weighed the aircraft: 7kgs. I had feared I would end up a higher than that. With deep wings and a wingspan of 4.6m the wingload will still be very low. Georg’s VT-16 is a bit more than 6.7kgs, so I’m not too far off the weight of his. Fingers crossed that I can maiden the Orlik in the coming week. I’ll soon post a data sheet on the Orlik as well.

 


VT-16 Orlik: installing wing servos

The resin on the seals of the wing control surfaces of the Orlik finally hardened out enough to sand the seals into shape (it takes 3-4 days to fully cure when you use white colourant and micro-balloons and your workshop is not that warm). Finally I had some time off and a few rainy days:  time to install the wing servos.

We’re using the usual setup for our Scale 1:3.5 gliders: Six control surfaces (3 on each wing), connected with an Integrated Drive System (IDS). We never use airbrakes on modern wing profiles – butterfly is better for landing on the slope and with modern profiles the ability to camber the full wing makes a much more performant glider.

As servos we use the Chocomotion FOX 10/10 and 8/6. We’ve used these servos on all our builds for the past few years and with many flying hours never had one fail on us. New for the Orlik are the IDS aluminium servo arms and the new glass/wood servo frames with ball-bearings kindly provided by Chocofly. The new frames are easier to install than the plastic ones we used earlier, and the aluminium servo arms are a perfect fit with the Chocomotion servos (unlike the plastic ones we used earlier) and also very robust. For the rest I used IDS pieces I still had left over from earlier builds. Rather than building the connectors on the control surfaces within the wing, I’ve placed them externally. The reason for this is that the control surfaces are quite large and I’d like to somewhat reduce the power required by the servos to move them.

Fitting all is a lot of work and careful filing all the openings. It almost took me two full days. After getting all openings and pieces to fit, I first fix all the bits with 5 minute fast-curing epoxy. At the end of the day I add slow-curing epoxy resin thickened with aerosil, to make sure that it all holds. The epoxy will cure overnight.

Next step is finishing the wiring in the wing and programming the plane….


Out on the slope – Photo session EB-29R

We’ve been spoiled with quite a few fantastic slope days over the last few weeks. I’ve been mostly flying my Chocofly JS3 and this week also my EMB-400 Urupema. Both planes still require some fine tuning (elevator incidence, center of gravity).

The JS3 is just a dream to fly, but I need to work a bit on the aileron throw and differentiation still.

The Urupema was a bit too nervous for my liking (very aggressive on the elevator, especially at higher speeds), but with increasing the elevator incidence and moving the center of gravity forwards it seems to have improved a lot. I’ll need to do a bit more experimenting still. The plane still amazes me – it combines the characteristics of a number of my favourite planes. It has totally friendly stall behaviour (with a very low stall speed) and thermals very well. But it also accelerates immediately as soon as the nose tips down even slightly (even in full camber!) and has an almost scary speed retention.

Last Thursday Richie joined us at the slope with his EB-29R (8m, 8kg). He built the plane entirely from scratch, including plug and fuselage moulds. With 8m the wings have lots of flex in them and the plane is definitely not built for high speed flying. But it thermals incredibly well and easily does very tight turns. Due to the low wing load, it’s also a breeze to start by hand – Richie didn’t need much more than a flick with his wrist to get it airborne – so cool to see!

I took my Canon camera to the slope to do a bunch of pictures of the EB-29R for an upcoming journal article. Here you can find the best pictures from the photo shoot, as well as some earlier pictures, videos and more information on the EB-29R.


In-between: Harth Style wing twisting glider (97cm)

While ordering some parts from the Hoellein Shop I couldn’t resist also adding a small in-between build: the 97cm Harth Style from Tim Wirth. It’s a very easy and good value kit for a glider with twisting wings. It was a very quick build – bridging the time I had to wait for the resin of the Orlik wing seals to fully cure. The Harth looks like a pretty fast and not easy to fly (and especially difficult to land) little glider, but it could be much fun on the slope and for morning and evening flights at our club’s annual Hahnenmoos excursion in June.


VT-16 Orlik: silicon hinges and seals of the control surfaces

Finally time to get back to my VT-16 Orlik build again. First I set the silicon hinges. After leaving the silicon to cure for a few days, yesterday I added the seals for the wing control surfaces. Both were done using our “usual” method, already described in earlier builds. Now I need to wait for the epoxy resin of the seals to harden out, before sanding them into perfect shape. It usually takes a few days to fully harden out and become easier to sand due to the white colourant and large amount of micro-balloons (and the fairly low temperature in my workshop at the moment). While I waited for the silicon hinges to cure I also finished the decals on the fuselage, which now looks pretty neat.


Project VT-16 Orlik: maiden flight of the first Orlik

We maidened the first of our three VT-16 Orlik, the one built by our chief designer Georg.

As usual we did this in aerotow, yours truly having the honour to be the tow pilot with my trusted Boomster. In our experience aerotow is the safest way to maiden a model where you’re not sure if you got all the settings right – a powerful towplane will at least get the model to a decent height, giving the pilot time to get to know the model and change some of the trim settings.

The first flight went very well, with only a few changes required to the butterfly settings and aileron differentials and some further fine-tuning in-between further flights in the afternoon. Georg will be further fine-tuning this over the next few weeks, giving Andi and myself the benefit of being able to copy his settings before the maiden flights of our Orliks.

The plane behaves as expected. With 6.7kg (4.6m wingspan) and a large wing surface, it’s a real floater and can be flown very slow. The thin wing profile and option of negative camber however also allows for higher speeds. It reacts very well to rudder and ailerons and has a friendly stall behaviour.

I’ve had some time at the sticks as well and immediately fell in love with the plane. It’s perfect for the type of conditions we have at our airfield, where light and well thermalling-friendly gliders are our preference. Can’t wait to maiden mine.

 


Alpine slope season start

A spell of warm weather and a nice northerly means alpine slope season start! On Monday our shaper Richie and I spent the afternoon on our favourite slope. There’s still quite a bit of snow there, but the landing area was clear.

For me a chance to fly my Chocofly JS3 again. Richie was flying his wonderful 6m scratch-built JS1. We spent two hours non-stop in the air with endless lift – awesome conditions. I’m hoping for a next opportunity soon….


VT-16 Orlik: cutting the wing control surfaces

There is still a lot of work that needs to be done once a plane comes back from the paintshop. Most frustrating is that after the big “wow” of putting it together, the next steps are barely visible and yet there’s a risk of really messing things up. Probably the scariest thing is cutting out the control surfaces on the wings. If that goes wrong (not a straight line, wrong place), you at least have a very visible mistake and even risk ruining all the work and having to start again.

A crucial step for cutting the control surfaceds is always made during the building of the wings, where we drill small holes in the abachi between the two spars that mark the division between the control surface and the wing. These holes need to be kept open during all subsequent steps, so that you can find them back! With these holes you know that you’ll be cutting in the right place.

For the actual cutting we use two different methods. The first is an adapted Dremel with a 0.8mm mill bit, that’s pulled along an aluminium ruler which is in turn stuck to the wings with bits of double sided tape. I used this method for the Urupema wings. The second is a nifty little gadget with a small motor running on a 2S LiPO battery, running on an aluminium “track” (see picture below), which Andi and I used for the Orlik wings. Both methods require a steady hand and double-checking before you cut. Fortunately Andi is an expert in this and perfectly cut our control surfaces. Using wooden templates we also cut out the openings for the servos.

Following this there’s a lot of work cleaning out the foam. Then we sand back the upper part of the wing so that the gap between control surface and wing is around 2 to 3mm wide. Then we sand the part where the control surface goes under the main wing back so that you have a sharp edge. Finally, we apply 49gr glass inside the main wing so that it’s protected against humidity and slightly reinforced.


VT-16 Orlik: Back from the Paintshop!

We spent three half-days painting the various colours on our Orlik (and Andi three more by himself). This wasn’t without challenges. It’s the first time that we spray-painted surfaces covered with Koverall (always a bit of a gamble to see if the solvents are compatible), and the first time that we applied so many different colours. The masking of surfaces takes a lot of time, and we needed to wait at least 12 hours between different colours to let the paint harden out. It all went relatively well, albeit with a few mishaps. The elevator and rudder covered with Koverall were very static and attracted every bit of dust, and the Koverall in some spots shows pinholes and stood up a bit. Most of this was easy to correct with a bit of sanding. Although not perfect, the surfaces look very good. We also made a mistake leaving two fuselages too close to the painting which resulted in some excess spray landing on them – the lower part is now a bit textured. But without these mistakes the planes would have looked too perfect – it’s an oldtimer that needs a few flaws :-).

This morning Andi went to pick up the fuselages and I just couldn’t wait to put my Orlik together. The edge of the canopy still needs to be painted (you now only see the epoxy used to glue the canopy to the frame), but I think it looks awesome.

Now comes some really difficult and precise work: cutting out the control surfaces, setting the hinges and seals, and then installing the servos. We’ll be doing this in parallel to finishing the electronics in the fuselage.

 


VT-16 Orlik: first day at the paintshop

We’re incredibly lucky to have a “master painter” (malermeister) in our building team. Andi is an absolute expert in paint types, spray painting model aircraft and also has enough connections to secure a slot in a friendly paintshop that allows us to use their professionally equipped space to spray paint our Orliks. Today was the “white” day, where Andi spray painted the white base coat on our three Orliks (and I provided an extra pair of hands to help secure and transport all the bits). We’ll need another few visits to the paintshop though, as we’re going to put a few more colours on :-).


VT-16 Orlik: fitting the canopy

The general view among builders I know is that fitting the canopy is their least favourite (most hated?) task in building a model aircraft. The canopy frame is not too hard to build (see earlier post), but cutting and sanding the canopy to a perfect fit, and then glueing it on is a real pain. It takes a lot of time and patience and very few things are so visible and ruin a build like a badly fitted canopy.

I use a pair of Tamiya curved lexan cutters and a Permagrit sanding block to cut and sand the canopy to size. Important is to mark the center both at the front and rear of the canopy as well as the fuselage to make sure that you always place the canopy in the same position. I do a first a “rough” cut using the Tamiya cutters and then using the Permagrit to sand it into perfect shape (being VERY careful that you don’t slip and scratch the canopy!!). Then it’s try, sand, try, sand…..repeat. It took me a bit over two hours on the VT-16 Orlik to get to an acceptable cut.

I then wax the seat of the canopy frame in the fuselage (three times, using liquid wax, slightly rubbing it with some soft cloth in-between coats). I then prepared epoxy mixed with micro-balloons and aerosil, fairly thick, but thin enough so that I could apply it using a syringe. Using the syringe I applied the epoxy evenly to the canopy frame and gently placed the canopy onto the frame. Using pieces of waste wood with double-sided tape as well as lots of wax tape I made sure that the canopy is in the right position and nice and even with the edge of the fuselage. Now it’s time to let the epoxy cure. Fingers crossed that it will come out well tomorrow….


VT-16 Orlik: elevator and rudder ready, fuselage servos installed

Today I finished covering elevator and rudder and applied the final (3rd) layer of dope. The rudder came out very well, but I will need to check a few things on the elevator’s fitting to the fuselage still (there’s a small difference in the throw of the two sides) before it can go off to the paintshop. I also installed the rudder and towhook servos, as well as the plate for the bungee hook (we usually start using a bungee on our airfield). Both rudder and towhook are the usual setup, with the rudder using the nifty adjustable wheel developed by our club, in a pull-pull setup using a kevlar cord. Now I’m looking for the right moment to cut the canopy to shape – a very tedious job which I’ve been putting off and for which I need to be in the right mood ;-).


VT-16 Orlik: Covering Elevator and Rudder

I’ve used many different methods for covering aircraft in the past. Among my favourites are Oralight and Oratex. Both are relatively easy to apply, with Oratex being very robust and oralight very light. Most recently I used Oralight for my Inside F5J and Oratex for my EcoBoomster Towplane. Both however have as a disadvantage that the surface tension is good but not brilliant, and you regularly need to do another pass with the hot air gun or iron to iron out new wrinkles – especially when you store your planes in an unheated room like I do.

When building my Moswey III, I was shown another method by Georg, the designer in our building team, and an experienced builder. This method not only gives great surface tension (love to drum my fingers on it :-), it’s also very light and, importantly, doesn’t require you to regularly straigthen out wrinkles. For the VT-16 Orlik we decided to use the same method again.

I’m sure that there are many different ways to cover a glider. This is the one we use for the Orlik. Materials to use: SIG KOVERALL covering fabric; Dope (we use Fuller-MZ), UHU Hart glue, nitro thinner and acetone. Method: 1) make a mix of 50% (by weight) UHU Hart and Dope and use a brush to apply one or two coats to all areas that the Koverall tissue need to stick to, allow this to dry; 2) cut Koverall into rough shape; 3) put the Koverall on the area you want to cover and fix the edges (not inner parts!) of the cloth to the wood using a small cloth with acetone (the UHU Hart/Dope mix will dissolve and the Koverall will stick to the wood); 4) use a hot air gun to carefully tighten the Koverall and remove any wrinkles; 5) using the cloth with acetone attach the rest of the Koverall to the inner ribs/surfaces; 6) apply two or three coats of dope, letting it dry out in-between and making sure that the covered surfaces stay straight.

While the Moswey III was hand-painted (to get that Oldie look), the intention is to spray-paint the rudder and elevator of the Orlik. More on that later.


VT-16 Orlik: installing the rudder

The rudder is now installed in the fuselage. Georg kindly prepared a balsa plate, with a coat of carbon on each side, in which the hinges (3 (bottom) and 2mm (middle and top) epoxy plate) were glued. After sanding everything into shape, the whole “cassette”, including 16mm balsa separators between the baseplate and rudder, was then glued into the tailfin (before inserting I used a syringe to apply slightly thickened epoxy just a bit before the location of the carbon coated baseplate). I clamped two bits of wood to the side of the tailplane to ensure a straight and tight fit. After allowing the epoxy to cure the rudder was sanded into its final shape, also to allow sufficient throw to each side.


VT-16 Orlik: wings ready for the paint shop!

The Orlik wings now perfectly fit the fuselage and are ready for the paintshop.

Fitting the wings to the fuselage is alway a bit of a torturous process, with lots of trying and correcting. Andi and I spent a whole afternoon for each of our planes, before glueing in the 6mm aluminium pins and letting the epoxy cure overnight – and hoping that the wings release again (we liberally applied wax to the fuselage to avoid this) and the fit is correct. Fortunately all went well.

Next step was to make the perfect fit between the wings and the fuselage. I used epoxy thickened with microballoons in a syringe, pressed in the space between the wings and the fuselage (after waxing the fuselage to avoid the epoxy sticking to the fuselage rather than to the wings). Then I spent hours sanding down the abachi on the wings, to get a nice and even surface, leading edge and trailing edge.

After making some corrections to the leading edge (there were some minor holes that needed filling with epoxy and micro balloons) the wings were covered in 49gr. glass, one side at a time. The glass was applied diagonally (for extra torsional stiffness of the wings). It was fixed with whitened epoxy, thinned down significantly with alcohol to allow the epoxy to be applied with a foam paint roller. The wings were left to cure hanging with the trailing edge down to avoid deformations.

Once cured, the wings were lightly sanded (220 grain). We then applied two coats of primer. The first coat with a spatula, pushing it into the glass structure (to avoid visible pinholes after spray painting), the second coat using a foam roller. Once the primer hardened out we spent some awful hours sanding it down again, almost onto the glass. For sanding we first used a machine with 220 grain paper, then finished the sanding by hand, using wet 400 grain paper.

A few minor flaws were corrected with spray primer, the wings are now ready to go off to the paintshop.