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.
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).
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.
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.
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.
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…
This Moswey III kit is not an easy one. Every time I think that I’ve made a lot of progress on the build I spend hours again on small details. But it’s progressing. Still need to glass parts of the wings and shape the leading edge out of linden/basswood. The work on the fuselage is also almost done, with the canopy, motor mount and towhook fitted. The Moswey III is now almost ready to cover.
Work on the Moswey III continues. With the very short nose, the Moswey III needs around 400-500gr weight in the nose to get the CG right. I’ve tried to reduce this by building the lighter (balsa) version of the elevator (with parts kindly provided by Frank Albrecht, who also produced this kit). Then the difficult decision: FES or not. The opportunity to replace so much dead weight with a much more useful electric motor, and gaining the benefit of being able to fly at my club’s airfield, really makes the answer a no-brainer. Leomotion.com provided a really nice and light electric motor with shaft extension. It’s at the lower end of what’s needed to bring this bird up, but I really wanted a light 6S setup and, knowing how the Moswey III flies, it will not be used all that much.
I guess the least favourite work of most aeromodellers is fitting and glueing the canopy. I built the canopy frame a few weeks ago, using plywood, balsa and glass. Sanding it to size and fitting the canopy was a lot of work, but something that just needs to be done. This morning I glued the canopy onto the frame using epoxy resin, doesn’t look too bad. Fingers crossed that it will separate well tomorrow morning.
Also ready are the rudder and tow hook servo setup. They will be glued into the fuselage over the next few days. I’ve gone for very light Chocomotion 12/9.5 servos. They are as powerful as the Futabas that we used for earlier builds. I’ve used these Chocomotion servos before, they’re great.
“Light” is the main theme of this build. Last week we maidened a Moswey III of a colleague in aerotow. It was an older and much heavier version of the kit by Frank Albrecht, with a heavy FES setup. The flight again underlined the importance of building light. The Moswey III handles a bit of extra weight well, in flight. The one of a colleague we maidened last week was well over 7kgs. The problem is that landings can get critical. The stall speed goes up a lot as it’s weight increases, which makes landings so much more challenging. I aim to have my Moswey well under 6kgs. I’ve occasionally flown the very old Moswey III of Georg, which is around 5.5kgs, and a real “balloon”, staying up forever. So far I’m at around 4.1kgs with all electronics, but without covering and some parts of the wings. Curious where it will end up….
To my surprise there was another article on the Moswey III, this time in in our local newspaper, the “Zürisee Zeitung”: https://www.zsz.ch/als-in-uznach-segelflugzeuge-gebaut-wurden-879571428937. Unfortunately I cannot reproduce the article here, and it’s hidden by a Paywall, but it’s a nice informative read on the production of the plane in the workshop in Uznach. It also has a nice picture of the restored HB-374.
In the meanwhile the construction of my Moswey III is making progress. The first wing is just about ready to be covered, and I’ve started on wing nr. 2.
In January 1946, Swiss glider pilot Siegbert Maurer attempted to break a glider rekord. On the Albis Pass, across lake Zürich from our club, he started his Moswey III in sub-zero temperatures and with a strong northern wind (Bise). The aim was to stay airborne for more than 28 hours and 7 minutes. Staying airborne in a glider for a long time wasn’t uncommon in this days. Trying to do so in the midst of a cold winter was. Unfortunately he was forced to land after “only” 17 hours, in the early morning of Wednesday 16 January. It wasn’t the performance of his glider that forced him to land, but his fear for serious injury after his legs started showing signs of frostbite.
In June 2016 Frank Albrecht (http://www.albmodellbau.de) provided me with a wonderful cnc-milled kit for the wings and control surfaces of a 4.28m Moswey III. The Moswey III is a glider from the 1940’s that was built in Horgen, which is just across lake Zurich. Frank’s kit is closely based on the first scale model built by colleagues in my club in the 1970s – the first of which, built in 1976 by Georg Staub (chief designer in our building team), still makes its annual appearance in Hahnenmoos (see this low-res video of me throwing it off the Schalmy cliff in Hahnenmoos). The Moswey III is one of the most performant oldtimer gliders I know, and a beautiful plane on top of that.
I’ve been working on and off on the plane for the past few years – using it as an “in between other projects” kit. Three years ago Georg and I produced two more glass fuselages from the original 1970s moulds. In December I picked up work on the kit again where I left off. Frank Albrecht’s kit is beautifully made, and looks very much like the original. But it’s not an easy kit to build, and a lot of work. I’ve set my mind on finishing it this year though, fingers crossed. What helps is that two other colleagues in my club are now having a go at this same kit, including Georg, who’s decided to build an “extra-light” version with FES.
This afternoon we released the 2nd Moswey III fuselage from the moulds. It looks even beter than the first one and only weighs 974 gr (the first one was 1055 gr). Very pleased with the result, and very curious to see how the first JS3 fuselage will come out….
On Friday Andi spray painted the JS3 and Moswey III fuselage moulds, as well as the rudder mould, so we can start building fuselages and a JS3 rudder again.
Today Georg and I built the second Moswey III fuselage, trying to improve our technique and using quite a bit less time than we needed for the last fuse. On Wednesday we plan to build our first JS3 fuselage. In the meanwhile Georg has finished the first rudder, which came out not too bad, and has started the second rudder over the weekend. Georg has also made good progress on preparing the main wings of his JS3, the core of which should be ready over the next few days.
This afternoon we opened the Moswey III forms, to see the result of our first “fuse building” practice run. The halves separated well, and a beautiful Moswey III fuselage emerged. We spotted only a few smaller bubbles, but none on critical/visible spots. The fuselage weighs 1.05kgs and will only need a bit of paint to hide the seams. Very happy with the result. Now it’s back to waxing and spray painting, and hopefully we can do another practice run the week after next.
We’ll need to produce four JS3 fuselages over the next few months. To make sure that we get these right we decided to do two practice runs, using the almost 40 years old moulds of the Moswey III classic Swiss glider. Georg built the first model of this glider in the late 1970s/early 1980s and still flies it at least once a year. It’s a must in every Swiss RC Glider pilot’s hangar. Georg and I still have a set of ribs for the wings, elevator and rudder of the excellent Frank Albrecht kit, so we decided to make two more fuselages out of the old moulds to enable each of us to build a Moswey III. Andi, the master painter in our JS3 team, kindly spray painted the moulds. This will enable us to build the fuselages as light as possible as only a thin layer of paint will be needed to finish the fuselages once they come out of the mould. Yesterday we built the first of our two fuselages, learning a lot in the process. Curious to see how it will come out of the moulds in a few days’ time.