Urupema – cigarette commercial

A while ago somebody sent me a link to a really cool 70’s cigarette commercial featuring the Urupema. Somehow I forgot to include a link on my blog. Now corrected. Note: there is a brief shot of what seems to be the cockpit interior of the Urupema. Unfortunately that’s a fake, it’s actually a shot from the cockpit of a Blanik. Do turn on the sound for this video – it’s so seventies!

Link to the video on Facebook here

Ventus 2c: Stabiliser and Rudder

Rudder and stabiliser are both built around a foam core. As this plane is supposed to be “super light”, I used 1mm balsa rather than the usual 0.8mm obechi wood. I also used 49gr glass fiber (45 degrees) rather than carbon inserts, as well as a thin (7mm) glass fiber strip at the trailing edge of the rudder and stabiliser. The stabiliser will not have a separate spar, but the carbon tube that also marks the hinge for the elevator will give enough stiffness to the stabiliser. In the middle of the stabiliser is a piece of plywood (with a hole for the screw to fix the stabiliser to the rudder), fixed with two bits of kevlar (top and bottom) to keep it in place.

Last week I built the upper side of the stabiliser and one side of the rudder for the Ventus 2c. Today I finished the lower side, which is now curing in the vacuum bag. I’m using my new small KNF vacuum pump, which seems to be holding up quite well. To avoid having to walk over to the workshop regularly to check all is ok, I installed a cheap webcam in my workshop to guard the vacuum pressure, and put a timer on the plug so that the vacuum automatically switches off at midnight – all so that I can have an easy and worry-free evening :-). Unbagging is tomorrow and then I’ll get to work on the stabiliser of the Diana 4.

Diana 4: landing gear and seat

For the Diana 4 we will be using a landing gear that is slightly smaller than the one we used for the JS3 – it’s a bit shorter and we’re using a 89mm rather than a 104mm wheel. The reason is that we’ve been using landing gears that were developed within our club and produced externally well over two decades ago. We’re now on the last of our stock and only have just enough smaller ones left for the three Diana 4 that we’re building.

Using a small milling tool made by a club colleague I cut out the landing gear doors and did a dry fit of the gear and the frames to hold the gear and the towhook (made out of 4mm plywood).

Last week I also produced the seat of the Diana 4, using a mould that we made for the JS3. After waxing the mould I covered it with thickened and coloured epoxy resin. Let it settle for a few hours and then put on two layers of 160gr glass. Unfortunately I didn’t have time to let the thickened epoxy rest long enough before adding the glass, so there are quite a few airpockets in the seat. I filled most of them today with some excess epoxy with micro-balloons. I’ll spray it with filler and then gray paint later, so the pockets will not be visible.

Diana 4: 2nd fuselage

Two days ago we built the 2nd Diana4 fuselage (mine). Today we released it from the form. It’s the best one we built so far. When we built the first one a few weeks ago we used a new resin for the first time(Hexion EP-Harz L285 LF and Hexion-Härter LH 285 (LF1), both from Suter Kunststoffe AG), one that has a much shorter processing time (50 minutes). The advantage is that the when layering the glass, the first layers are more stable and less likely to shift as you’re building up the layers. The disadvantage is that you really need to mix only small quantities of epoxy (we mix 100+40gr) and must time the mixing right. We quickly learned this when building the first fuselage. For the second fuselage we got it right from the start. The result is a fuselage that has much fewer airpockets (haven’t found any so far) and one that’s also quite a bit lighter (1288 instead of 1428gr).

Diana 4: first fuselage in the mould and first assembly

After our building team colleague and master painter Andi painted the JS3/Diana4 moulds last week, today Georg and I built the first fuselage. It’s always a bit harder to build the first one after a break of almost a year, and are using a new epoxy resin and a different size 160gr glass, which also takes a bit of getting used to. Include setting up the workshop, other preparations, waiting before joining the two mould halves and cleaning up afterwards we almost spent the whole day working.

While we were waiting for the epoxy to cure a bit before joining the two halves of the mould, excitement got the better of us and we put the wing and elevator shells that Georg finished over the weekend on the fuselage of his scratch-built JS3 (the same fuselage we are using for the Diana 4). The result looks great.

Joining the fuselage halves went very well. We will release the first Diana4 fuselage from its mould on Wednesday afternoon.

Chocofly JS3: Short outer wings

In-between work on the Ventus 2C and Diana4 I installed the servos and IDS system in the new short outer wings for my Chocofly JS3. It’s now “ready to race” :-). Installing the servos is significantly easier since Chocofly started including the gaps for the servo rods and servo links in the wing moulds. It’s still a fiddly process to get the IDS installation right, but it came out very well. I like the colour of my new winglets and thought I’d go for the “Rapture” decals in grey this time.

Diana4 and Ventus 2C: Wing joiners and ballast tubes

In-between other tasks I’ve been preparing the sleeves for the wing joiners and the ballast tubes for the 4.5m Ventus 2C and the 5.14m Diana 4. I’ve also given my new vacuum pump a test run and have done most preparations to build the elevator and rudder for the Ventus 2C.

The sleeves for the wing joiners are done as usual: first liberally apply Teflon bike lubricant to the wing joiner and wrap it 1.5 times with a thin plastic bag. Then pull over a kevlar tube and wrap it with kevlar rovings. Then tightly wrap the whole thing with tear-off fabric, put a weight at the end and hang it out to allow the epoxy to cure. We always leave the sleeve on the wing joiner while building the wings and only pull out the wing joiner once the wing shell is done.



Urupema – new pictures and a first cockpit picture

I regularly get contacted with questions or suggestions in relation to our builds. I was particularly happy by an email I got from Marvin S., who is planning to build a Urupema with his father-in-law and has done extensive research into this unique Brazilian glider. Marvin shared some really nice pictures that I hadn’t seen before, including one of the instrument panel (which we were unable to find for our build). Marvin kindly allowed me to share these pictures on my blog. I hope that they can be of use to other builders. Thanks!

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) .

Chocofly JS3: new winglets and short outer wings!

It’s been a while since I last updated my blog – keeping busy with other things! Now that winter has fully arrived and I have a bit more time on my hands again it’s time to post a few updates.

The first exciting news is that I received new winglets and short outer wings for my Chocofly JS3! I lost my winglets on the slope at the end of August (see two posts back), and the new ones got stuck in Chocofly’s delivery chain. I finally got to pick my new winglets up with Dani yesterday and fitted them to my long outer wings this morning. I also decided to go for the rapture logo in grey instead of white (looks better in real life than on the picture…). I’ll be building the servos into the short outer wings over the next week or so, in parallel to my other projects. My Chocofly JS3 is now ready to fly again. I’m particularly looking forward to finally maiden the version with the FES fuselage on our club’s airfield – will be an awesome thermaller :-).

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.