New Project: Diana 4, scale 1:3.5 (5.14m)

In 2016 the company Avionic purchased the rights to produce the manned version of the Diana2 glider – the 1:3.5 and 1:3 scale versions of which are among my favourite gliders. The Diana 3, production of which started in 2017 wasn’t really interesting to build – essentially a Diana2 with a fuselage to accomodate bigger pilots. But the first drawings of the Diana4, released in early summer this year, really got our interest. As you can see on the picture below, the fuselage is almost identical to that of the JS3. The wings are essentially the Diana2 wings, extended to an 18m version on the inside.

The decision to build this plane in scale 1:3.5 was taken quite fast. We have moulds for the JS3 fuselage, which we can use to do the fuselage of the Diana4. Georg also rapidly did a new version of the plans of the Diana2 wings, extending them and adjusting the root to the JS3 fuselage. He also designed the elevator, based on that of “our” JS3 and Diana2.

Georg will be progressing rapidly on his build over the next few months, and his glider should be flying in early spring – well before the maiden flight of the manned version, scheduled for June 2023.

So far we’ve finished cutting the foam for the wings and elevators and I’ve built the wing joiners. We hope to build the first fuselage early next week.

This will be an awesome plane. It’s a combination of our two favourite gliders, the JS3 and the Diana2. The dynamics of the Diana2 wings in combination with higher wings and a shorter fuselage than the Diana2 will make it an ideal slope and thermals gliders. Looking forward to this one.

New Projects for Winter 2022-2023

I’ve been doing some preparatory work for new projects over the last few months already – in between other tasks – but I now finally have time to start getting into building mode. An I have a luxury problem: too many exciting project opportunities! Work has started on the following new scratch builds:

  • A scale 1:4 Ventus 2C (4.5m): A few years ago I went to pick up a DG1000 fuselage that I purchased from a retiring pilot. In his workshop there was this really pretty fuselage, which he agreed to sell to me for a few Francs. When I showed the fuselage to colleagues on the club they got all excited: it’s a fuselage that was built by a colleague in our club almost 20 years ago, from moulds and plans that are still around. In fact there are also still a few built planes around. This summer my mate Georg did a full revision on his and stripped out the landing gear, with the result that he got a really wonderful and surprisingly performant 4.5m glider weighing less than 5kg. The plane fills a “gap” in my collection of gliders, in the sense that it’s easy to hand-start on days with little wind. I’ve decided to give this build priority for this winter. I’ve built the wing joiner, have the rudder and elevator parts ready to build. Together with Georg we also cut the foam for the wings.
  • A scale 1:3.5 Diana 4 (5.14m): this one will be 2nd in my priority list, and I’ll be building part of it alongside the Ventus. More on that in a next post.
  • A scale 1:3 Diana 2 (5m): The 5m Diana2 was the first Diana2 model built in our club and as far as I’m aware anywhere. It was a huge success within our club, but was quickly overshadowed by the smaller 4.28m, of which the Chocofly version has become famous as one of the best slope gliders around. I’ve been wanting to build the 5m version for ever. We still need to build a fuselage for myself and for Andi. I’ve yet to decide if I will fit it with my Baudis 5m Diana2 wings, or whether I’ll build my own set of wings. I built a wing joiner last week, but the rest of the plane will be for next winter.
  • A scale 1:3.5 Monett Monerai (3.43m): My mate Richi has been planning to do a model of this US 12m kit glider for a while. It’s something very special. It’s also an easy build. Richi has done the plug for the fuselage pod (it’s a pod and boom glider) and is having the boom produced by colleagues in a professional glider manufacturer. I’ve produced the wing joiners for Richi and myself. I’ll work on this one on and off, depending on how other projects progress.

There may be one or two further surprises that I’ll report on as they appear :-)(I’m expecting something from the Ukraine, but the delivery of that is uncertain for understandable reasons) .

Diana 2 Flyday

Dani Aeberli from organised the first Diana Flyday on 16 August 2020, in Eglisau, Switzerland. He brought together 27 Dianas, with pilots coming from as far as Geneva, including three scratch-built Diana 1 (4.28m), a whole bunch of Diana 2 (4.28m, both scratch-built and the Chocofly version), as well as the 5m version of the Diana 2 (scratch-built, and Baudis, and a combination of both), and the Chocofly 6m and 7.5m versions. Our building team was represented by Georg Staub (who came with 8 Dianas!), Andi Schwerzmann (4 Dianas) and myself (also 4 Dianas – lined up in the first two pictures below). Our team supplied all the scratch-built planes (the amazing 4.28m Chocofly Diana2 is the commercial version of the one built by members of our team). Georg and I flew our already 14 year old Diana 1, still a fantastic glider, and we also enjoyed some amazing flying of Dani and his 7.5m Diana2. A you’ll have concluded already by my ample use of superlatives: an awesome day, and a big thank you to Dani for organising it. See below for a few pictures. More pictures and videos can be found on the social media channels of


Diana2 Flyday!

Save the DATE!

Diana 2 Fly-Day…… Sunday 16.August 2020 at
Modellfluggruppe Zürich, Eglisau (
Bring your personal Diana 1 or Diana 2 and Fly with us!
Lets see how many we can get together…..World record??

Saturday 15th will be also first time DONs Grill & FLY

Please sign in on the Doodle Link before the end of July 2020…to make sure you can be part of it!

Looking forward to see you all there
ChocoFly Team

Maiden flight of the Chocofly Diana2 – Glider version

When there is a stable high pressure area north of us, over Germany or eastern Europe, we usually have a stiff northern breeze, called “Bise”. Most of my favourite slope soaring spots are on north-facing slopes, i.e. time to head out. Unfortunately, being a northern wind, it’s also a freezing cold wind, which means that this early in the year you can add a significant wind-chill factor to temperatures already barely above zero degrees Celsius. In cycling we always say that there is no such thing as bad weather, just bad gear. Following that wisdom I went out on Tuesday to my favourite slope, with chilly but perfect wind conditions. The slope is perfect Diana territory – I usually fly one of my Dianas (Diana 1 or 2) there. With the whole Covid-19 lock-down I drove up alone and had to hand launch the plane myself. This is one of the reasons that last year I ordered an extra fuselage for my Chocofly Diana2 (1;3.5), and built it as a light glider without the usual FES (5.5 kilos). Normally I maiden my planes on a nearby airfield, using a towplane. But extraordinary circumstances require extraordinary actions. And as I know the Diana2 pretty well by now, having clocked many hours on the various version I have, I hand-launched it myself on the slope for the maiden flight. It flew off without any bother and I spent a wonderful 75 minutes in the freezing cold. The nice thing about the Diana2 is that it’s such an amazingly versatile plane. It thermals amazingly well and loves low as well as high speeds. At 5.5 kilos it’s not as fast my heaviest version, which weighs almost a kilo more, but still very fast and a lot of fun to fly. I’ll be taking this one to the slope more regularly.

On the slope I met up with my mate Richie, who was also flying his Diana2 (the Chocofly Diana2 is the commercial version of the design from Richie and Georg). Hence the photo below of the two sisters together. His Diana2 is even lighter, well below 5 kg, and on the slower side, but goes up like a little balloon in the least bit of upwind.

In-between: another Diana2….

With the JS3 maiden flight still to go, my favourite plane by far remains the Diana2. So far I had three versions: my 1:3.5, 4.28m and 5.65kg scratch-built (my favourite!), the Chocofly derivative of our scratch-built (identical size and profile), with 6.3kg (Alpine version) as well as the Baudis/Chocofly 1:3, 5m version (8.2kgs). The great thing about the Diana2 is that it’s such a versatile plane and can be flow in weak thermals and in extreme slope conditions. It performs very well at low weight (a real “balloon”) but also carries ballast and higher weight extremely well, when it becomes a real racer. I’ve been wanting to built a “light” version for a while. Chocofly was able to supply me with an extra fuselage, which I’ve now built as a light glider. It’s ready to maiden, and I hope to do a first aerotow soon, and use it on the slope afterwards.

Baudis Diana 2 (1:3 – 5m)

As a huge Diana2 fan I couldn’t resist ordering a Baudis 1:3 version last summer. The plane was delivered a few weeks ago. Now that the AvantiHawk is airborne getting the Diana2 ready will be my priority for the next few weeks. Fortunately the amount of work that still needs to be done on this is limited – fitting canopy, motor and retractable gear, as well as the rudder servo. The wings and elevator servos are already installed. Initially I intended to build my own fuselage with this plane (we have moulds for our own 1:3 Diana2), following the example of Georg, one of the other members of our “building team”. Seeing how much work was needed to adjust the fuselage to the wings, and being unable to resist the urge to fly this plane during this season rather than only next year, I decided to go with the original Baudis fuselage instead (which Dani from Chocofly was able to deliver on very short notice, thanks Dani!). Unfortunately the Baudis fuselage is quite “anorexic”, compared to our own fuselage, so I may still want to do a self-built fuselage sometime in the future.

In the meanwhile…Diana 1 and 2

I can’t resist the temptation to squeeze in a few non-JS3 pictures. Last week Friday I maidened my 1:3.5 Chocofly Diana2. This plane is the exact copy of the Diana 2 that was designed by members of our JS3 team now almost ten years ago (using the same wing design, profile and fuselage), and of which I already built one from scratch last year and had a lot of fun flying it since. My new Diana2 is the Chocofly pre-production heavy slope version. With 6.3kgs it is heavier than my scratch-built Diana 2 (5.8kg), but also a very robust slope racer – looking forward to putting this one through its paces on one of our nearby slopes soon.

We also had a family excursion of our full set of scratch built Dianas, me flying my refurbished 14-year old Diana1 (SZD 56.1), built by Richie, Richie flying his 1:3 Diana 2, and Georg his 1:3.5 Diana 2. Bliss. Oh, and yes, we love our Dianas. The Diana2 is still the best plane I’ve ever piloted, but maybe our JS3 will change that?

Decals – trial run

Getting the decals for our planes made has always been a very tedious job. We either spent a lot of money having them produced commercially or had to beg friends with access to vinyl cutters to make them for us. As the newcomer in the team, and somebody who loves to play with computers, I decided to bite the bullet and bought a vinyl cutter myself. It’s a Silhouette Cameo 3. Not only is it good value for money, but it has excellent and very easy to use software.

I’ve started preparations for the decals for the JS3, which are going to be challenging. As a trial run, I redid the decals on a 14-year old Diana 1 (1:3.4, 4.28m) glider that I took over from Richie. Even though the Diana1 is 14 years old, it was one of the first planes built using the same techniques that we are now using for the JS3. With only 5.3kg it’s a light weight, excellent for more difficult conditions. I maidened it last week, after giving it a full refit of its electronics (and new decals!). Below some pictures of the old decals, done 14 years ago, and the new ones done on the Silhouette Cameo 3. I’m very pleased with the result. I’m even more pleased with my refurbished Diana1, which now looks like new and flies like a dream!

Oh, and I couldn’t resist adding two pictures of my new Diana1 and myself on the slope last week….

IDS system for the wing control surfaces

I wrote earlier about our servos, but not in detail: we will be using KST X08plus for the ailerons on the outer wing of the 5.14/18m version, ChocoMotion 8/5.0 for the ailerons, and Chocomotion 10/9.2 (in size identical to the KST DS225MG, but more powerful) for the rest of the control surfaces (6 Servos in the 4.28/15m wing and 8 Servos in the 5.14/18m wing).

Today I received a large package from in the mail. provides servo frames with Integrated Drive System (IDS) for all the servo types we will be using. We have used their IDS system on most of our gliders in the past few years, including last year’s scratch-built Diana2 (1:3.5). The frames fit well, are robust and good value. The IDS system can be fully integrated into the wing, so no ugly protruding levers or large holes in the wing surfaces. Most importantly, they provide a wing surface control that is extremely direct and completely without play. Fitting the IDS frames requires more effort than standard systems, but the result is definitely worth it. Below are two pictures of the system built into my 1:3.5 (4.28m) Chocofly Diana2 that I hope to maiden soon. The Chocofly Diana2 is identical to my scratch-built Diana2 (which was designed by members in our team), except that the wings were built in a mould.