Urupema cockpit upgrade

I’m not usually one for great detail on my cockpits, but I wasn’t too happy about the orange cockpit seat and the square headrest of my Urupema. Also, some of the paint on the seatpan started to chip off. So I was very grateful when our building team colleague Richie offered me a beatifully made yellow seat inlay for my Urupema cockpit. Before sticking it onto the seatpan with hot glue, I also resprayed the seatpan, which now looks like new, and redid the headrest (now round). A great upgrade for an awesome plane methinks. 🙂

Chocofly JS3 – ready to fly again!

My Chocofly JS3 is ready to fly again. Chocofly kindly supplied me with two new outer wings and a new wing joiner. I also replaced one of the outer wing servos (gear was damaged) and fixed the small cracks in the fuselage, as well as the connector of the left winglet. I replaced the hinges of the landing gear doors with some more robust ones (the ones supplied by Chocofly unfortunately did not hold long, I’m back to our usual and proven method), and fixed the EDF bulkhead, which had a few small cracks and made a few other smaller repairs and improvements to my JS3. The wings have no scars from the accident, but the repairs on the fuselage are still visible. I hope to have the fuselage repainted in the coming winter to remedy that – but now it needs to fly! Unfortunately the weather has been pretty bad in the last few weeks, fingers crossed that will change soon….

Hahnenmoos week – some of the finest slope soaring

Our annual club outing to Hahnenmoos was great again. Even with some Corona restrictions and a very bad weather forecast we got plenty of opportunities to fly. Here are some videos and pictures.


When disaster strikes – Chocofly JS3 damaged :-(

It’s been a few years since I had major damage to one of my planes. Unfortunately disaster struck again on Thursday last week. After maidening Georg’s Chocofly JS3, I wanted to have a flight with mine as well. Upon the start in aerotow, the right wingtip of my JS3 touched the ground, I overcompensated and before I knew what was happening it flipped over to the left and crashed upside down just meters after the start.

Fortunately the damage is relatively minor for what was a pretty serious crash. Both outer wings can probably be made usable again with repairs (but will need replacing, also for optimal performance), and one of the small wing joiners of the outer wings needs replacing. There are a few minor cracks in the cockpit area of the fuselage and the EDF cleanly broke off. I was really lucky that there is no damage to the inner wings, elevator, rudder and tail of the fuselage. With a new wing joiner, some work on the outer wings, fixing the smaller cracks in the fuselage and re-attaching the EDF, I should be able to restore my JS3 to flying service again soon. I’ve already ordered new outer wings and will probably have the fuselage resprayed the coming winter to restore the plane to full glory.

The worst thing is that I was really very much looking forward to flying the Chocofly JS3 in Hahnenmoos starting Sunday. That will not be possible.

Another lesson learned. Flipping over after overcompensating at the start in aerotow is not uncommon. Most of my flying mates have had serious crashes (and much worse damage than my JS3 suffered) this way. But it’s something that can be avoided by asking somebody to hold up the wing of your glider upon the start. I was stupid. I definitely won’t forget this for next time.

Maiden flight of my Moswey III

Yesterday my Moswey III successfully completed its maiden flight, completing the maiden flights of this winter’s builds. I was quite nervous about this one, since I’ve been building this plane for quite a few years now. It’s been one of my most difficult builds, with lots of possibilities to “get it wrong”.

Well, it looks like I got all essentials right :-). We decided to take three of our recent Moswey III builds (all based on the kit from http://www.albmodellbau.de, but with different versions of the kit and different glass fuselages) so that we could compare and finetune settings on all three. Georg Staub has been flying his Moswey III quite a bit in the last few weeks and has gradually moved the center of gravity forwards to 125mm, and increased the longitudinal dihedral, as well as the throw of most control surfaces. We copied these settings on all three Moswey III before maidening mine in aerotow.

The maiden flight went very well. We had to mix in a bit of down elevator with the motor, and a bit of up elevator with the airbrakes, but for the rest the settings seemed spot on. As I was flying the towplane in the afternoon, Georg Staub had the honour of doing the maiden flight and all follow-up flights in the afternoon. I did fly it for a short bit, but since he flies mode 4 and I fly mode 2 (swapped rudder and aileron controls) it’s hard to get a real feel for the plane. Georg was having a great time flying mine though, in the end really putting it through its paces with some nice aerobatics – something the original Moswey was actually also designed for. Interesting was the difference between my Moswey and the one of our third colleague. His is around 2kg heavier (a bit over 7kgs rather than the 5.4kg of mine). The heavier Moswey also flies very well, but, not surprisingly, has a much higher stall speed and is a bit harder (faster) to land. The light version thermals incredibly well and is a breeze to land.

I hope to fly my Moswey III on my local club’s airfield with catapult start over the next two weeks. The third week of June it will come to our annual Hahnenmoos slope soaring week, where we hope to get together a whole bunch of Mosweys.



Slope testing the Chocofly JS3

After Friday’s maiden flight in aerotow, I could test the new Chocofly JS3 Rapture on the slope today. The conditions were perfect for the JS3, very light lift, with great intermittent thermals. We had three JS3 on the slope, one scratch-built by Georg Staub, identical to my scratch-built, with around 6.3kg, one scratch-built by Richie Oberholzer, without FES, around 5.5 kg, and my Chocofly with JETEC E-70 with around 6.6kg. We were all flying the 18m/5.14m version (I only have this version for my Chocofly JS3, and always fly the longer wing version with my scratch-built).

The Chocofly version is virtually identical to our scratch-built JS3. The differences are of course that the wings are fully moulded, whereas our own are foam core with carbon/glass layup. The elevator of the Chocofly JS3 is approximately 1cm less deep, and the fuselage approximately 2cm thinner. In addition the wings have 3 rather than 4 control surfaces.

With the identical wing and elevator profile, the performance of both planes is however very similar. We did some formation flying in different camber settings. My JS3 and that of Georg performed equally well, with the Chocofly version giving the impression of being slightly more performant in thermals. With more robust wings, the upper end of the speed spectrum is of course also higher for the Chocofly version – I got to 230kmh in some of the low passes.

The JS3 (both my scratch-built and the Chocofly version) ist the best scale glider I have for flying in thermals. It picks up the least bit of lift and allows for slow, tight turns, very similar to a F5J glider. With the multiple dihedrals in the wings, it turns mostly on rudder and only needs minimal aileron. Even with massive camber settings it is hard to stall, and it announces a stall very nicely – nasty stalls are very rare. The nice things about the Chocofly version is that the 5.14m also allows for higher speed passes, and of course having a JETEC rather than FES makes the plane so much nicer to look at.

To note is that there is also a 4.28m version of the JS3. I have shorter outer wings for my scratch-built JS3, but, to my shame, have never flown it with these. I may however be tempted to order the shorter outer wings for the Chocofly version. With the shorter outer wings it should be quite the slope racer – although in the GPS version not as much as my Apline Edition Diana2 (with which I can do just anything). To be decided.

I’m still not done with determining center of gravity and longitudinal dihedral. I did move the CG somewhat backwards but have found that I still need quite a bit of uptrim on the elevator. I hope to get some test flights on one of our local airfields soon to sort this out. I also still need to sort out the battery issue. I’ve using 2 older 3S 3700 LiPos as a 6S setup, with 4mm plugs, which I’m not happy with. I’ll be measuring Ampere/Watt of the JETEC shortly to see what power flows, and will probably adjust plugs and battery. I’ll also replace my 2S LiPo that I use as a backup power source (next to the BEC). More on all that later.

Even with all this, the plane flies great already, it will only get better. I’m a big JS3 fan, together with the 1:3.5 Diana2 it’s my favourite plane.


A day at the races – EMB400 Urupema in awesome slope conditions

Finally, spring weather! And added to that a stiff northern breese (“Bise”), means time to head out to the slope. Yesterday’s conditions were almost scary – a stiff and gusty wind, and very turbulent conditions. We decided to take our Urupemas, which were built for precisely such conditions, although the turbulent conditions pushed them to their limits. The tall grass unfortunately meant that a catapult launch is difficult and a dangerous hand-start was necessary – fortunately this went ok, although two starts were close to going wrong (planes over 6kg on a slope without a drop and gusty winds is challenging). Below a short video of yesterday’s flying.


Chocofly JS3 Rapture Maiden Flight

An unexpected opportunity to go maiden my Chocofly JS3 Rapture came up today at the Eglisau airfield of the Zurich model aircraft club. A windy and bumpy northern breeze, but some nice thermals and especially some great towplanes and towplane pilots and assistance from Dani Aeberli from Chocofly. The maiden flight went well, but the plane was a bit nose-heavy and had too little down-elevator in crow. Moving the battery to the rear fixed the CG issue, and it’s now flying just as nice as my scratch-built one. It’ll still need some fine-tuning though – but the turbulent weather wasn’t conducive for that today. Dani insisted on trying a self-start, something I hadn’t counted on being possible, but it went amazingly well – even uphill on a grass piste.

Here is a “quick and dirty” video and some pictures. More to follow.


Re-organising the website

Originally this website started out as a blog tracking the building of our scratch-built JS3 – mostly as my own online “notebook” to track how we build our planes. Over time it has evolved in an overview of multiple builds, both from scratch, but also kits and ARF planes. I was astonished to find that I’ve got more than 125 posts on it.

Unfortunately, it has also become very hard to find information on a single plane. So it was time to slightly reorganise the site. You will now find a new tab “Models”, under which I’ve listed the various models that are described in this blog. For each of these models I will over the next few months construct it’s own page, with data and a few pictures for that model, but also with a link to all related blog posts. Until then, the links on the models page will lead you to a page with all the blog posts related to that model only. I hope that makes it easier to find information on a specific plane.

Users may also notice that I removed the “build gallery”. I initially included this to allow access to full size pictures in the blog. As I hadn’t updated the build gallery for a while, and all blog posts now link directly to the full size pictures, I decided to remove this page.

Finally, I’ve also reopened the blog posts for comments. I closed this a few months ago as a result of the huge amount of spam I was getting. I hope that the new spam filter prevents this, but still allows those who want to comment to do so. Note that comments will need to be approved by me before they appear on the page.

As always, thanks for visiting my site and feedback welcome.

Moswey III – HB-474 original pictures

I was recently contacted by Peter Willes from the UK, who took a whole bunch of pictures of the original HB-474, a long time ago. The pictures and copyright on them are his, but he has kindly agreed to allow me to post them on this blog – in the hope that it might inspire other builders to build a model of the HB-474 as well. They will certainly help me to finalise the cockpit. Many thanks Peter!

At the time of writing this post, the original HB-474 is actually for sale in the UK. There are some helpful (but very low resolution) pictures on the website of the club where it’s offered for sale. This is the link – for whatever it’s worth (it may be taken off-line once the plane is sold).

Chocofly JS3 – ready for the maiden flight

With the JETEC E70 and retractable gear fully installed, and having prepared the rest of the components for the fuselage a few weeks ago, all that remained was finalising the installation of the components into the fuselage and programming the transmitter. It still took me more than two rainy days of work, but the JS3 is now ready for its maiden flight. The take-off weight is 6.67kg (this time weighed with my professional Mettler scales – having obtained different values from my cheapo scales earlier). That includes two 3S 3700mAh LiPos for the EDF, and a 2S 2200 Lipo as backup power (main power comes off the BEC from the ESC). I put the Center of Gravity at 103mm, identical to our scratch-built JS3 (which has the same wing layout and profile, but a larger elevator and thicker fuselage), this is also what Dani from Chocofly is flying his prototype with. Georg is also close to finishing his JS3 – once the weather is ok again we can maiden both our JS3 and my Moswey III.

That concludes my builds for this flying season. I’m pretty proud of a productive winter – having (finally!) finished my Moswey III, built a great towplane (Eco-Boomster) and completed the Chocofly JS3 Rapture. Now it’s time to go flying, do some maintenance, but also start on the next projects for the coming winter – more on that soon. And of course I’ll post some pictures and videos of the maiden and other flights :-).


Chocofly JS3 Rapture – installing the JETEC E70

The weather over the last few weeks has been dreadful. On the few days that were ok-ish I had other things on, so have been unable to go maiden my Moswey III. On the positive side, the many rainy days also meant that I had time to get back to my Chocofly JS3. Together with Georg Staub, our team’s designer, we fitted the JETEC E70 retractable EDF, as well as the retractable gear into the fuselages of both our JS3 (he’s also building one, identical to mine). It’s the first time we’ve done this, and was not without it’s challenges.

We were fortunate though that Dani from Chocofly was so kind to provide us with a perfectly fitting CNC cut mount for the JETEC. He also kindly supplied a perfectly moulded “spare” of the top of the fuselage, from which we could cut out the cover of the JETEC and allowed us to study and measure the installation of the JETEC on his JS3. I also made a drawing of Dani’s cutout in the top of the fuselage, which I digitised to allow me to cut both the positive and the negative template of the opening at the top of the fuselage on my Silhouette vinyl cutter (a PDF version can be found through the link, contact me if you want the version for the Silhouette vinyl cutter).

After correctly positioning the vinyl template, we used a dremel to cut out the opening for the JETEC. The correct positioning of the motor mount in the fuselage proved to be quite challenging. Georg constructed a tool that allowed us to fix the motor mount to the wing joiner to allow us to adust it to the correct position. We then fixed it on a couple of places with 5minute Epoxy Resin, before fully fixing it with 24hr Epoxy and a few strands of carbon roving. Cutting out the landing gear doors wasn’t too hard once we determined the position of the retractable gear (which was determined by the position of the JETEC). Once the whole thing was installed I cut the EDF cover to shape, again using the vinyl template, and fixed it to the top of the JETEC. A lot of work, but I’m pleased with the result.

Moswey III cockpit

I’ve had some questions on the design of the instrument panel of my Moswey III. While there are lots of examples on the web of instrument panels for the HB-373 and HB-374, I only found two pretty vague pictures of the HB-474. I decided to reconstruct the instrument panel based on these pictures, and pictures of the appropriate instruments I found on on the web.

The instruments on my cockpit panel are printed and covered in transparent vinyl. I drilled appropriate size holes in 0.7mm plywood, stuck the instrument pictures behind the holes and glued the whole thing to 3mm plywood. The rings around the instruments are washers and o-rings to fix water taps, spray painted black. The 0.7mm plywood was painted in a transparent brown varnish. Result doesn’t look too bad. For those interested in building this instrument panel, the PDF file below contains the data required to construct one yourself.

Moswey III ready for its maiden flight

The last “small” bits of work always take more time than expected, but the Moswey III is ready for its maiden flight!

Because of the short nose and relatively large elevator and rudder, most Mosweys need quite a bit of trim weight in the nose. The goal of this build was to replace this weight with a light motor setup, and avoid having to add any dead weight. Unfortunately I didn’t quite succeed in doing this. With the light motor setup and 2x3S 3700mAh batteries placed way at the front, I still need approximately 140gr of trim weight in the nose. But even with that trim weight the take-off weight of my Moswey is below the targeted weight of 5.5kg. Even with the heavier full-carbon wing joiner it’s a leasurely 5.36kg.

Most of the Moswey III builds I’ve seen are either in yellow or in blue, and based on the HB-373 or HB-374. I’ve chosen to go for the less known HB-474. I found a few pictures of this one in full white, probably following its restoration and before the final paint was applied (at the time of writing this blog post the HB-474 has yellow wings and a white fuselage, it’s based in the UK and actually up for sale). The clover on the tail is also on the original, and I decided to add the Moswey III logo to the nose (thanks to Frank Albecht from http://www.albmodellbau.de for supplying pictures of the original logo for me to use to cut the logo).

A quick summary of this build: the fuselage and wing joiner are self-made, using old club moulds from the 1970s. The kit for the wings, elevator and rudder is from http://www.albmodellbau.de, which is in turn based on the original 1970s build from Georg Staub, member of our building team. It’s not an easy build, but a beautiful kit for a great and very well flying plane.

I’m looking forward to flying this beauty shortly.

Moswey III painting…

Covering the Moswey III with SIG Koverall went better than I expected. The surface tension is good, and there are no major deformations in the wings. After applying two layers of dope (Fuller Spannlack), I’ve now applied the paint. I’ve used a water-based acrylic paint (WESCO), applied with a paintbrush. This was recommended by Andi, our paintmaster and member of our building team, whose knowledge of paints is amazing and whose advise always spot on. I could have spray painted the Moswey, but for an oldtimer you simply need to see a few strokes of the paintbrush.

Painting the wings and especially the fuselage with a paint brush isn’t easy, especially if you do it for the first time. Key is using the correct brush (soft, thin hair), not applying too much paint and especially the thickness of the paint. I had to redo one side of the fuselage because the paint I applied was too thick and the brush strokes were way too visible for my taste. With around 40% water added to the paint it now looks much better. I used transparent paint for the transparent parts of the wings. The transparent parts and underside of the wings all have two coats of paint. The upper side and fuselage three. The result is far from perfect (TIP: do make sure the masking tape is applied well, especially on uneven surfaces!), but I’m satisfied – and an oldtimer shouldn’t look too perfect.

Moswey III covering….

Before the slope outings started I managed to get a bit more work done on the Chocofly 1:3.5 JS3. The wings are now ready, next step is installing the Impeller. For this I’m waiting for my friend Georg (the designer of “our” JS3), who will be building an identical Chocofly JS3. We’ll be installing our impellers together.

He’s been busy finishing his 4.28m Moswey III and has been pushing me to finish mine as well before finishing the JS3. With a few days of bad weather I decided to follow his advice and started covering my Moswey III. Until now I’ve always used Oracover, Oratex or Oralight. While very easy to handle, it doesn’t quite give the same surface tension as a covering using dope. Georg has quite a bit of experience with this and yesterday he gave me a brief introduction on how to do this (using SIG Koverall and Fuller Dope). After two full days of work the covering is done, and the first layer of dope applied. Now I’m waiting for it to dry out before applying the 2nd layer, whilst crossing my fingers that the wings and control surfaces will stay straight…

Slope season start!

As the snow starts to clear from nearby mountains and temperatures are slowly going up, we had a couple of days of great wind for our favourite slopes. Most nearby slopes are good to fly when we have a northern breeze (“Bise”). About a 10 minutes drive from where I live is the Pfannenstiel Hochwacht. It’s not the best of slopes, but a good place to head out to when the weather is too cold to make longer flights or when you just want to head out for an hour or so.

In mid-April we had three good consecutive days of Bise, but still very cold and cloudy weather, and most of my usual flying buddies didn’t feel like heading out in the freezing cold. I spent three lovely but freezing cold afternoons up on the Pfannenstiel with my Chocofly 2.8m Taranis and my Chocofly 2.2m Kobuz, accompanied by a few friends. The Kobuz is a lot of fun to fly, you notice it’s smaller size and the fact that it’s not a purpose designed aircraft – it’s “lively” and requires you to work the sticks :-). The Taranis is a completely different plane. It’s got a huge speed envelope, is pretty hard to stall and totally stable to fly even in the most turbulent and windy conditions. Lots of fun – including some high speed passes at over 310 kmh (without ballast in the lightest version of the plane!).

Last week the weather got a bit warmer and sunnier and with another few days of Bise we were able to head out to our favourite (private) slope in Toggenburg. We opened the slope season there with our Diana 2, the 4.28m version (both scratch-built and the Chocofly version of the same plane), and on the 2nd day we took out the 5m Diana2. My mate Richie also “slope-maidened” his brand-new EB29R – with an incredible 8.3m wingspan and only around 9kgs. I got some time on the sticks of the EB29R – an amazing thermaller. See the video I did on the first slope flight below.

Starting work on the Chocofly JS3

Finally found the time to start working on the Chocofly JS3. The build quality of the Chocofly JS3 is excellent, and the amount of work to be done not too bad, it’s a real joy to work on this.

I’ve glued in the elevator servo and prepared the pushrod. The landing gear (own production from our club), rudder servo and the towhook, are also ready to be installed, but I’ll wait with doing so until the Impeller is in place.

Today I started work on the wings and cut out/glued in the IDS rudder horns for all six control surfaces. Dani from Chocofly kindly provided fitting rudder parts and perfectly fitting aluminium IDS servo arms. Tomorrow I hope to finish installing the wing servos, and then will start soldering the wiring harness. The difficult part will be installing the impeller – which I’ve never done before…

Start of the new group project: the Czech VT-16 Orlik

Even though I’ve still got enough going on in the workshop, it’s time to start planning ahead for the coming winter. So far we’ve done a new project with our building team every two years, and the team’s fingers are starting to itch to get into something new. Richie was going through some books with oldtimer gliders and found the Czech VT-16 Orlik. The original Orlik had it’s first flight in 1959 an was all wood, but filled with foam. It’s got a very characteristic shape and there are not many RC models of it around, and certainly none in a “modernised” version with a thinner airfoil. It didn’t take much for the rest of the team to enamour itself with the plane and decide that we want to build this one.

Fortunately there are many relatively good plans available for this plane on the web. I’ve had the best ones enlarged to our usual 1:3.5 scale. The fuselage is huge, 2.13 meters long. We’ll build the 16m version, which gives a wingspan of 4.6 meters. The length of the fuselage and size of the elevator are great for the model version, and we’ll probably stick to scale (we usually need to enlarge the elevator). We had some discussion on doing the wings in wood/ribs, but decided to build it in our usual method – foam cores, covered with abachi/carbon/glass and carbon spars. We will do the rudder in Balsa/ply, covered with tissue, to save weight and give it at least this little “scale” detail. As usual we will also omit the airbrakes and do four or six control surfaces. Wing profile will probably be MH-32. This will give us a nice all-rounder. We build our planes to fly – a lot.

Richie will now start work on the fuselage plug (which is a huge amount of very messy work – but he likes it and is a true master at this), and Georg will start desiging wing and control surfaces. In Autumn we will probably do the fuselage moulds and start building the wings, in the hope that we can maiden the first Orlik in spring 2022.

To be continued…

The JS3 has a new sister

Corona-delayed, and a long wait, but she’s there. The Chocofly JS3, fully moulded, 5.14m wingspan, empty weight around 4.2kg. On Monday we picked up three JS for me and two friends in our building team. Ours are the first production builds of the lighter version (production nr. 3, 4 and 5), but wings are still very stiff and their torsional strength is better than our own scratch-built versions.

The Chocofly version is closely based on our scratch-built JS3. Chocofly has used the same wing and control surface profile and layout (all by Georg Staub, who also designed the “small” Diana2 and SB-14). The only difference is that the 5.14m version has “only” three control surfaces, rather than the four in our JS3. The fuselage is stunning, and based on original CAD data. Chocofly has a record number of orders for this plane, and the waiting list is huge. But it’s a beauty and I know it will fly very well – my scratch-built JS3 was my most-flown plane in 2020 and already has clocked up a couple of hours of airtime in 2021.

I’m deeply impressed by the quality of the build. I’ll be building mine with a small retractable JETEC E70, running on 6S. Unfortunately this means that I cannot fly it on our local club airfield (no turbines allowed), but I can fly it at the other club that I’m a member of in Gossau and of course on the slope. I’ve been dreaming of getting a glider with JETEC, and the fuselage is so beautiful that I just cannot bring myself to hack the nose off this one. Haven’t decided yet if I’ll add a landing gear – this will depend on whether there is enough space in the fuselage once the JETEC is installed, and the weight of the plane. Aim is to keep the take-off weight at around 6 kilos at most (my scratch-built one is 6.3kgs, which flies great).