Author Archives: j_lefevere

Chocofly DG800: maiden flight

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This spring has not been good for flying so far – the weather has been all over the place. On 8 April I did however finally get a chance to maiden my Chocofly DG800. My mate Georg, who also built one, maidened his two days earlier. Unusually, he struggled a bit to get it flying well and had to play around with the throws, incidence and center of gravity. I greatly benefitted from his experimenting and was able to maiden mine with much improved settings.

We’ve changed the incidence significantly (reduced it to around 1.2 degrees by applying five layers of masking tape under the front of the tailplane) and moved the center of gravity to 68-69mm. It also needs a lot of differential on the ailerons.

With these setting the plane flies very well. It has the perfect combination of light weight (easy hand start), good thermaling and a lovely acceleration, exactly what I was looking for. Unfortunately the wind changed to a northerly breeze early in the afternoon, so we were unable to experiment further. The settings are thus still preliminary and will need to be fine-tuned. More details once I get the chance to fly it again.

Monnett Monerai: maiden flight of Richi’s Monerai

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My Monerai is still waiting for its coat of primer before heading off to the paintshop. My mate Richi, who’s built the plug and mould for the Monerai fuselage, already finished his Monerai a while ago. He had the maiden flight yesterday.

We were incredibly lucky with excellent conditions on the “airfield” of his club (Modellfluggruppe Wald), which is a wonderful SW-facing slope with stunning views over lake Zürich. Richi first launched a small glider to check for lift – of which there was plenty. I then launched his Monerai for him.

Maiden flights of an all-new self-built model are always a bit of a gamble. While you can calculate the center of Gravity and incidence, as well as throws, our experience is that these values are mostly less useful than following our instinct and experience. Richi’s instinct and experience proved right – as so often. The Monerai flew wonderfully right from the start – in fact his first flight lasted more than two hours! He will need to experiment a bit with the CG and throws still, but the settings are not far off where we’re likely to end up.

I made a video of the first flight, including start and landing. Between filming I also flew my self-built Ventus 2c for an hour and a half. Pure bliss.

 

Chocofly DG800: ready to maiden

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My new Chocofly DG800 is now also ready for the maiden flight. Finishing the canopy was quite a bit of work. I wanted to have a “hidden” lock (under the left wing) – as I do with all my larger scale gliders. I also needed to cut out part of the seat pan for the motor. Fortunately the seat pan was a really good fit, as was the canopy, so glueing it together wasn’t too much of a hassle. I wasn’t sure what glue to use – my mate Georg used canopy glue – but decided to go for thickened and whitened epoxy resin. To avoid epoxy getting onto the fuselage I put clingfilm into the fuselage and some grease on the canopy lock and pin at the front. I then applied a thin layer of epoxy resin to the side of the seatpan, installed the seatpan onto the fuselage and then carefully put the canopy on top. With a bit of waxtape I fixed it into position and waited for the epoxy to cure. Instead of painting the canopy edge I used vinyl tape. Chocofly kindly sent me the plotter file for the canopy frame so that I could plot it on my trusted Cameo 3. Applying the sticker required a steady hand but went well. Canopy looks fine.

I also finished installing the electronics in the fuselage and added the decals. My mate Georg’s DG800 is also ready for it’s maiden flight – hopefully we can maiden them together in the next few weeks. More pictures to follow then.

Monnett Monerai: airframe ready for painting

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The Monnett Monerai’s airframe is now ready for painting. I installed the landing gear and spray painted the canopy frame. I also made the basic parts for the seat pan and instrument panel.

The next step is applying primer to the wings and parts of the fuselage. That’s something I really dislike – the primer is very smelly and sanding it gives a huge mess. I’ve been waiting for it to get a bit warmer so that I can work in the barn with the door open. I hope to get a chance next week – especially since it’s likely that I may get a slot in the paintshop the week after next. Fingers crossed.

Chocofly Avanti: ready to maiden

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The Chocofly Avanti fuselage is repaired, spray painted, polished and the electronics installed. It’s now ready for the (re-)maiden flight. The yellow paint came out ok – it’s a standard acrylic car paint (spraycan) that’s not too far off the gelcoat yellow of the fuselage. I managed to nicely polish the newly painted part. Unfortunately, as expected, the transition to the “old” paint will always remain visible. I’ll have the upper side of the horizontal stab painted white to match the white wings when the Monerai heads off to the paintshop.

I hope to have the maiden flight in the next few weeks. Interesting will be to also fly my Avantihawk (which uses the same pair of wings) on the same day to see the difference in performance.

DG800 and Avanti: Decals!

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The DG800 deserves some cool decals and the Avanti needs them to cover up the repairs and repainted nose. So I set myself to work. Dani from Chocofly kindly shared with me some of his plotter data for the DG800s, which I modified and adapted for our version. As we are building two of these (Georg and myself) we decided to use the same basis, with a small difference in colour – as we did with the VT-16 Orlik (red and blue). I also decided to push my Silhouette Cameo 3 to its limits by plotting smaller pieces and to try two-coloured decals. Let’s see if they will hold :-).

Chocofly DG800: installation servos and motor (FES)

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As mentioned in my earlier post, this is a pretty quick build. The servos in the fuselage and wings are installed. I used the Chocomotion 10 and 8mm Servos with the new Chocomotion LDS system, all of which I’m familiar with from previous builds and which work perfectly. There is no play on the wing control surfaces whatsoever and I’m able to use the full range of all servos, with sufficient throw.

I also installed the motor bulkhead. I was a bit nervous about this one, as Chocofly now uses MIGflight motors with a new type of bulkhead that’s glued in from the front. This no longer allows me to use my usual method for installing the motor. It turned out to be easier than feared. I first did a rough cut and then sanded back the nose, repeatedly fitting the motor and bulkhead to see if the fit was right. In the end I fixed the bulkhead (with motor) in the right position using a few dots of 5 minute epoxy. I then removed the motor, covered the front of the bulkhead and the nose of the DG with wax tape and fixed the plane with the nose down. Using a small pencil I first added some white coloured resin on the sides of the bulkhead (from the inside), wrapped in a thin carbon roving and then filled up the rest with somewhat thickened epoxy resin. Curious to see how it comes out tomorrow. I do hope that I got the downward angle of the motor (usually somewhere between 3 and 4 degrees) in the right range.

 

In-between: Chocofly DG800

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I’ve got too many unfinished projects in my workshop (a pretty common “problem” among aeromodellers I think). As the monerai is now in a phase where it requires long waits for paint to dry I have time to tacke the other projects. One of the unfinished projects is a brand-new Chocofly DG800 that’s been sitting in my workshop since Autumn and that I’m keen to get ready in time for the start of the new flying season.

The Chocofly DG800 is the successor to the DG600 (still available from RCRCM). The DG600 was one of my favourite planes and also the glider that got me into slope soaring in Hahnenmoos. I sold mine a few years ago as I wasn’t flying it enough, I wasn’t entirely satisfied with the build quality from RCRCM and one of my club mates was keen to buy it from me. I did however miss my good old DG600. When Dani (Chocofly) raved about his new DG800 I ordered one, together with my flying buddy Georg.

Georg has started building his DG800 and kindly given me his notes (see also below, downloadable as a PDF file in the correct size). As a results my build can be pretty quick. I’ll be using the cool new Chocofly LDS system that I already used on my Ventus which is very precise and robust. I’ve glued the servo horns and servo frames into wings and fuselage and should have the wings and fuselage ready shortly. A bit of a hassle will be the canopy, as I’ll be installing a FES system that seems a challenging fit with the canopy. More on that later.

 

In-between: Chocofly Avanti (4m)

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A few years ago I built my “AvantiHawk“, a combination of the “Duckhawk” glider from the United States with wings from the Chocofly Avanti (which are similar to the scale wings, albeit much deeper). I’ve always toyed with the idea of getting an Avanti fuselage so that I can fly the same wings with the thinner fuselage as well – ideal for handstarts.

One of my club colleagues crashed his Avanti on the slope last year (catching a tree). He destroyed the right wing and broke the nose of the fuselage. The right wing was not salvageable, but the fuselage was. He played with the idea of ordering a new set of wings, but eventually decided against it and kindly gave me the broken fuselage as well as tailplane and the left wing. Chocofly kindly provided me with the missing wing joiner and a new canopy, as well as the servos for the fuselage and motor. I’ve started fixing the fuselage, using multiple layers of 100gr glass. I’ve also inserted a new motor bulkhead and extended the fuselage somewhat, so that I can fit the new Chocofly/MIGflight outrunner for 6S and the matching 42mm Spinner (rather than the 45mm Spinner that was used before). The fuselage needs a final sanding and is then now ready for it’s final coat of paint. The components are ready to be built in once it’s painted.

The only problem is that my wings are white and the fuselage and tailplane are yellow. Respraying the entire fuselage white is usually not a good idea (you will always see that it was once yellow), but I can make the upper side of the tailplane white to match with the wings. The underside of wings and tailplane are the same blue. Also cool is that the new canopy as well as spinner and propeller are white, so I’ll probably go with a yellow-white (and blue underside) colour combination. I do however still have to find a spraycan with matching yellow.

Monnett Monerai: more canopy and landing gear

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The canopy came out well – except that the small pins that I put in to avoid the center part of the canopy standing out when it gets hot (from standing in the sun) broke off when releasing it from the fuselage. Not a big issue, I’ll just have to do it differently.

On Saturday I went to one of my Hahnenmoos flying buddies who has a CNC milling machine and had offered to cut the sides of the landing gear. I’d prepared a DXF file for the sides earlier using QCAD, so it was easy to convert and upload to his CNC computer and cut the sides. I use 2.5mm glass fiber plate. Unfortunately I couldn’t find a black or white plate, so it’s green-ish, but that’s not too bad either.

I now need to position the gear into the fuselage, cut the opening on the bottom of the fuselage to size and glue it in using thickened epoxy resin.

Monnett Monerai: tow hook, canopy lock and canopy

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I’ve yet to decide if I’ll add a FES motor to the Monerai. The main issue is that the tail is very light and there is no space to put the batteries far behind the center of gravity. I’ll decide on adding FES before sending the glider off to the paint shop.

I do however want a tow hook. And of course I still needed to fit and install the canopy.

The towhook I built myself, using a servo I had lying around still, and our usual DIY setup. The same with the canopy lock. I like these to be “hidden” below the wing/fuselage.

Fitting the canopy is always a lot of work – usually saved for a day that I feel up to it and pull it through in one go. I roughly cut it to shape using my Tamiya canopy scissors. Then it’s a lot of sanding/trying/sanding/trying until it fits. Most of the sanding is done using my permagrit. After that I glued the canopy to the frame using thickened epoxy resin (aerosil and micro-balloons), this time also adding some grey colourant (after waxing the fuselage to make sure that the resin only sticks to the canopy). The whole thing took me more than 5 hours…..

Monnett Monerai: fitting the tail boom

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I’ve been putting off fitting the tailboom of the Monerai – too many variables and things that can go wrong. In the end I asked my mate Georg to help me. He’s the one who usually does the wing positioning of the plugs of our new models and also has the right gear and space. I had already mounted the tailplane at a 0 degree angle to the tail boom. That left deciding on the length of the tailboom, the right incidence of the tailplane in comparison with the wings and the exact positioning of the tailboom and V-tail.

We first positioned and fixed the fuselage pod and wings at an incidence of exactly 1.3 degrees, so that the tail boom could be fixed horizontally. We then prepared a support for the tail boom and roughly aimed it in the right position. Then we removed the tail boom, prepared epoxy resin and glued the tail boom into the correct position. Using our laser we double-checked everything and allowed the epoxy to cure. The next day I prepared and added some thickened epoxy on the inside of the fuselage as well as plywood bulkhead. I also used 10cm of leftover tailboom to reinforce the inside of the tail boom where it is glued into the fuselage (cutting it open on one side to reduce the diameter so that it fits).

Monnett Monerai: Landing gear

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The Monnett Monerai has a fixed suspended landing wheel. My mate Richi’s gave his Monerai a wheel without suspension. I’m not a big fan of unsuspended wheels – especially when you have bumpy landings on grass or slopes the forces on the wheel and risks of damage are too big. Most importantly, I thought it would just be nicer to build a suspended landing wheel – also to put the crash-course in CAD drawing that I had in August last year from a flying buddy on a rainy day in Hahnenmoos into practice.

The design of the landing gear is very much based on the well-tested design of our Urupema and Orlik – just smaller, with a 70mm foam wheel. The front and rear bulkhead are 4mm plywood and designed “by hand”. The sides of the gear were designed on QCAD and will be milled from 2.5mm glass fiber. To check if all the bits fit together and are sufficiently stable I first cut them out of 2mm plywood. A flying buddy will mill them out of glass fiber for me next week. The front and rear bulkhead are held together using wooden sticks that are just there for correct positioning and will be removed once the gear is glued into position in the fuselage. The suspension will be bicycle inner tubes.

Monnett Monerai: small steps and glassing the wings

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The small things always take up a lot of time – especially if it involved waiting for epoxy resin to cure between the different steps. After sanding and fitting the wings I glassed the corners of the wing root (protection from transport damage), finalised fitting the V-tail to the tail boom (0 degree dihedral compared to the tail boom) and filled up the space between the two parts of the V-tail and the tail boom with thickened resin.

The next big step is glassing the wings. I used 48gr glass cloth, cut at a 45 degree angle (this means a 2cm overlap around 30cm from the wing root). I first put the glass on the wings (and tailplane). Then I prepare a mixture of epoxy resin, with a bit of white colourant and 30% methanol to make it really “watery”. The white colourant helps ensure that we will need less paint afterwards when painting the wings. Using a paint roller and an old non-stick frying pan I roll the resin mixture onto the glass, making sure that it’s nice and straight, without any folds.

I first do the underside, making sure that the glass is about the middle of the leading edge. After applying the glass I hang the wings leading edge up on the wing joiner and a piece of wood to let the resin fully cure (without warping the wings). After the resin is cured I will use a razorblade to cut away the excess glass and gently sand the edges.

Tomorrow I will do the upper side of the wings and tailplane in the same manner, with the only difference that I’ll wrap the glass over the entire leading edge. In total I need around 2x25gr of thinned down resin per side of each wing.

Monnett Monerai: first time assembly

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After fitting the wings I applied lots of wax to the fuselage and then used thickened epoxy to fill out the remaining gaps between the wings and the fuselage. The fit is now perfect.

Using a template I also glued the carbon tubes for both sides of the v-tail into the tailboom. Like the original, both sides of the v-tail are slightly off-center.

In-between I sanded back the canopy frame and applied an extra two layers of 100gr glass on top. I also did some work on the instrument panel and the seat pan.

Most importantly: time for a first fitting together of all the bits! it’s starting to look like a Monerai now. Still lots of work to do though. Next steps are to glass the wings and tailpane, finish fitting the tailplane to the tailboom and fitting the tailboom to the fuselage at the correct incidence. I’ll also need to start working on the fixed landing gear. More on all that later.

Monnett Monerai: sanding and fitting the wings

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The main advantage of using ebechi to cover the wing cores is that it makes it easier to get rid of any uneven parts. These usually occur on the underside of the wing where the main spar or the two spars on either side of the hinges of the control surfaces are epoxied into the foam. The 0.6mm thick abachi usually gives enough “margin” to sand the uneven bits out.

Sanding the ebechi is a messy job. I usually do this outside and was lucky that today was relatively warm and windy. To sand the ebechi I use my favourite Permagrit (the really rough side), my trusted old bosch sanding machine (80 grit sandpaper) as well as a block with 100 grit sandpaper. Most important is to sand the leading edge of the wings into shape. During the building I put a few mm of resin thickened with microballoons at the leading edge, which makes it much easier to sand. I also use a small template to check the profile of the leading edge at different places of the wing. The template I used for the Monerai is the same as the one I will use for the Diana4 – the wing profiles are not identical, but close enough. A good trick to make sure that you sand the wings evenly is to mark the entire wing with a pencil. Once the pencil stripes are sanded away you have sanded enough and any uneven parts are most likely to have been sanded out.

Sanding reduced the weight of each wing by almost 40gr. Both of them now weigh exactly 482gr each (I weighed the wings during sanding to make sure that they weigh the same).

After sanding the wings I fitted them to the fuselage. The wings are attached to the fuselage using 6mm aluminium pins that are glued into small bits of plywood that I inserted into the base of each wing during the build. On the side of the fuselage they fit into short aluminium tubes that I glued into the fuselage earlier. To ensure that these pins are in the right place I first make the two holes in the fuselage for the wing joiner and make sure that the openings in the fuselage are just big enough to keep the wings in the right place. I check the position of the wings using my laser, as well as by measuring the distance to the table and to the nose of the fuselage. I then fix the first wing using tape, remove the other side, and use a long 5.5mm drill (thanks Aliexpress) to mark where the hole for the aluminium pin needs to come. I do the same for the other wing. I then drill open the holes for the four pins, making sure that there is enough play to enable the pins to set themselves in the exact right position. After waxing the fuselage around the area where the pins go in I then glue the pins into the wings using thickened epoxy resin (with cotton flakes), put both wings onto the fuselage and wait for the epoxy to cure.

Monnett Monerai: wing cores both ready

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Last week Friday I closed the 2nd wing, with help from EP. We’ve built up a nice routine and division of labour, so that closing it now takes us less than two hours. On Saturday I took the wing out of the vacuum bag. After sanding off the rough edges the scales showed a weight of 518.5 grammes. That’s a weight difference of 1.1gr compared to the first wing we built earlier last week (519.4gr.) – the closest I’ve ever come with building wings and well within the margins. Wing flex and torsional stiffness of both wings seems excellent.

All the main bits and pieces of the Monerai are now ready in their “crude” form. Now comes the long process of putting it all together. Just to see where I am weight-wise I weighed all the bits – it adds up to around 2.4kg. My mate Richi, whose monerai is ready for its maiden flight, has a take-off weight of 3.6kg. I hope I can keep mine in that same range, but under 4kg.

Today I worked on the tail end, skid and canopy frame. I also installed all the wing plugs in the fuselage. Next step is to sand the abachi on the wings, before fitting them to the fuselage and then glassing them.

Monnett Monerai: Main Spar Buildup

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Today I spent a few hours preparing the 2nd wing of the Monerai for closing. Measuring, cutting out the foam and especially preparing the Rohacell core of the main wing spar always takes quite a bit of time. All is now set for closing the 2nd wing, which we will do tomorrow.

I got a question via the comments form on the buildup of the main spar, especiall how I connect the sleeve of the wing joiner with the rohacell core of the main spar. I always glue the different core bits of the main spar together using 5 minute epoxy, fixed with a small piece of painters tape (picture below). This is really only to make sure that the core of the main spar stays together while handling. It doesn’t add to the stiffness of the wing. The stiffness of the wing is provided by the carbon sleeve around the entire core (from wing root to wing tip), by the carbon rovings below and on top of the main spar (for the Monerai 2×19 at the root and 2×2 at the tip) and of course the carbon layup underneath the ebechi (note that the carbon layup continues under the main spar for the entire length of the wing, in the first 75% of the wing covering the entire width of the wing, in the last 25% only the carbon D-Box as well as the area of the control surfaces).

So to be clear, the buildup from inside to outside is as follows:

– in the area of the wing joiner: carbon wing joiner (stays in the joiner sleeve during the building of the wing); kevlar sleeve wing joiner; 3k carbon sleeve; 19 carbon rovings; carbon layup (100gr biaxial); ebechi.

– in the area after the wing joiner (from inside to outside): rohacell core; 3k carbon sleeve (reducing to 1k towards the tip); 19 carbon rovings (reducing to 2 at the wing tip); carbon layup (100gr biaxial); ebechi.

– Important: once the Ebechi is sanded into shape I’ll also add a layer of 50gr glass (diagonally), before applying primer and then paint.

Also see my earlier post on building the wing of the Diana4 with a list of materials used.

I hope that the drawing below provides more clarity.

Monnett Monerai: Logo

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I prepared the logo and decals for my mate Richi’s Monerai a while ago (his is ready for the maiden flight). Finding a usable version of the logo wasn’t easy. Until around a year ago there was a full website with documentation on the Monett Monerai – including building instructions and plans. Fortunately I saved the logo from that website already last year – just before the website went offline. Here’s the logo, I also have a digitised version if anybody needs it – just send me a message over the contact form.

Monett Monerai: wing building

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Last week I put both the upper sides of the wings in vacuum. On Monday I prepared the layout and spars for the first wing. Today I “closed” the first wing, with help from my flying buddy EP.

Preparing the spars was a bit more work than usual as I had to do the calculations for the amount of carbon rovings on the main spar and decide on depth of the control surfaces. I used in total 2×19 rovings at the root and 2×2 rovings at the tip, distributed using Christian Baron’s helpful excel sheet. The width of the main spar is 25mm at the root and 6mm at the tip. I used three different types of carbon sleeves around the main spar, a 3k for the first third and 1k sleeves for the middle and outer third. The amount of rovings at the root was determined on the basis of the space available after deducting the space required by the wing joiner and sleeve. I’m curious to see how heavy the first wing will be.