EvilC57

And presumably all this sunshine we’ve had recently is down to the proliferation of solar farms we have now.

Yes, I said in my original post that it appeared to have failed at the interface between the back end of the skid and the front of the carbon tube which reinforces the fuselage. Unfortunately the underside starts to slope upwards towards the nose just forward of the front end of the CF tube (which is why I guess they ended it where they did). As you can see in the pic below, the skid also has to support the wheel. I agree though Keith, it’s a stress point. I could however edit the .STL file for the skid, to make the glued lap joint longer where it overlaps the front to the tube.

I agree. I wasn’t really happy with the way the fuselage and wing parts have to be printed with their layers running perpendicular to the direction of maximum stress. Unfortunately because of the necessarily flat ends of each section of the structure (where they interface to the adjoining part), there is no other way to print them unless you use a lot of supports, which when removed would leave a pretty unsightly surface. With the wings stress across the layers isn’t really an issue because they’re supported by the two 8mm carbon fibre tubes, the longer of which runs almost to the wing tips. However, particularly for the part below which supports the weight of the battery, if I build another one I’ll increase the gyroid infill density, and fit some strips of CF as longerons inside. There is some longitudinal support provided by the ‘Fuselage protector 2’ PLA parts as shown below. However these were obviously insufficient.

Yep, OK thanks leccyflyer. I would add a point 7 to my post above in relation to this particular aircraft, Planeprint are an established company (in Germany I believe) with a range of around 24 different models. There are also a number of videos on YouTube from around the world of various people flying their Jetwing, and none have reported structural failures or other problems with the design. I was unlucky I guess, and as I say, if I build another one I’ll pay more attention to reinforcing the structure around where it supports the battery.

It had had two previous flights without any problem (both included several high speed passes). At the time it broke up I had just pulled out of a turn back in towards the field, and was at the start of a high speed diving pass, but was at nowhere near the full speeds previously attained without issue. I have been flying RC for over 20 years and many of the aircraft I fly are high performance EDFs, and ‘Reno Racer’ type models. As Don Fry says above, why would it break where it did if flutter was the problem? Several observers saw the short fuselage (with the battery inside) fall away from the wings separately, in other words it didn’t break off in the impact with the ground. Looking again at the design, there is clearly no reinforcement and no measures taken (like increasing the 3D infill) in the area to take account of the not inconsiderable weight of the 3700mAh 4S lipo it has to support in flight. In my opinion, and the opinion of several people there at the time, it was structural failure, not flutter.

Yep, unless I’m searching for something specific, I only ever use the Latest Posts page.

A warning for anyone who has, or is thinking of building this model. I built the EDF powered version last winter, and had two successful maiden flights with it recently. Unfortunately during a third flight yesterday it suffered a major (and quite spectacular) structural failure. I had completed one fast low pass, and had just gone around for another one when the whole model seemed to blow apart in the air. Studying the recovered remains on the ground afterwards, it became evident that the fuselage had failed just forward of the wing. I suspect this to be due to a potentially weak point at the rear of the PLA skid where it joins to the carbon fibre tube on the bottom of the fuselage. During flight the weight of the heavy lipo battery with additional g-forces is effectively cantilevered from around this point. I would suggest strengthening the area by glueing CF strips to the inside of the fuselage, and/or soaking the area with thin cyano, as Planeprint suggest for other areas in the model which need local reinforcement. Despite carefully following their instructions regarding print settings and Cura profiles to ensure sufficient adhesion between the LW-PLA layers, I suspect the stresses in the area which failed were just too great for the material. The failure point was around the area I’ve marked build instruction extract below, and not at the joint between parts. During its short life the Jetwing flew beautifully and I feel deprived now of the fun I could have had with it in future, so if I do decide to build another one I shall certainly be paying more attention to strengthening the structure where it seems it’s needed, and suggest that anyone else building the model do the same.

You were lucky! My late father once told me the story of how on the last day of term when he was at technical college in the 1940s, the chemistry lecturer said ‘Right lads, what do you want to do?’. ‘Can we make some gunpowder sir?’, said one of the lads. ‘Of course!’, said the teacher. So they proceeded to make gunpowder. Having effectively made a small bomb in a glass container, someone lit the fuse and they all ducked down below the benches. Apparently the resulting explosion saw them spending the remainder of the lesson removing bits of broken glass from the wooden panelled walls. Health & Safety, what’s that?

When I was at school in the early’70s I remember the chemistry teacher passing around an open glass beaker about half full of mercury, getting us to notice the weight, then allowing us to float steel ball bearings in it and pick them out with our bare fingers. Different times…

The ad was probably written by a non modeller, the kind of person I’ve had ask me what my models are models of. They don’t seem to understand when I’ve tried to explain that some of our models are not scale models OF anything in particular, they’re just small aircraft in their own right.

Not so funny when you read this one 😐.

I used Planeprint’s test parts as well. Go to Planeprint and download their Wingtest and Calibration Tool. colorFabb’s LW-PLA reels are only 750g rather than the usual 1Kg, so presumably that’s why the reels are narrower then usual.

Oh dear. I used them OK back in the winter. But I must admit I do seem to remember their communication with me was non-existent after the initial confirmation too. I think my reel duly arrived after about 5 days though. I guess all you can do if there’s still no arrival soon is to keep trying to ring them. Hopefully you paid by credit card, so you can get Section 75 protection if you need it. I think I remember using iDig3D because 3DJake didn’t get very good reviews on TrustPilot. iDig3D are also based in Nailsworth in Gloucestershire which isn’t too far from me, whereas I think I read somewhere that 3DJake are in Holland. Unfortunately it seems suppliers of colorFabb LW-PLA are few and far between in the UK.

I’m currently in the city of Nanning in southern China for a few weeks with my wife (who is Chinese) while we visit her family. We spent an interesting half hour or so in the local DJI shop this afternoon, where I got a chance to handle various DJI products, including the new Avata and associated goggles. I must admit I hadn’t seen the Avata before, as I don’t constantly keep up with DJI’s latest innovations (pun intended!). The lady assistant gave us a short flying demonstration around the shop with the Avata, flying it with the RC Motion 2 controller while we tried out the FPV goggles. With the aid of my wife translating, I explained that I fly fixed wing, helis and multi rotors back in the UK, and could I have a go? Unsurprisingly the answer was no. Insurance issues I guess, and as I think she tried to explain, she didn’t know my capabilities - and I’m unfamiliar with the RC Motion 2 controller anyway. I’m thinking of getting a Mini 2 sometime, and my my wife was trying to encourage me to buy one in the shop. I must say that having done some price comparisons with Amazon back in the UK, the prices are favourable (DJI products are made in Shenzhen, which is only about 450 miles from here). For a couple of instances, a Mini 2 SE Fly More Combo here is about £372 and currently £439 on Amazon UK. And an Avata Explorer Combo here is about £1,014 and currently £1,099 on Amazon. I won’t be buying here though as I’m concerned about guarantee issues if there’s a problem back in the UK. I suspect the FPV (and maybe the main) transmitters are more powerful than allowed in the UK, and any documentation or software is likely to be only in Chinese. An interesting diversion for me though, and made a nice change from being dragged around shoe shops!

It wouldn’t, you’re quite right Bob (go to the top of the class, and I’ll go to the bottom 😅). In which case I’d use a 6-way Multiplex or maybe a 9-way D-type.

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Like you I used to use Prusa until I built one of Planeprint’s models. Their build instructions and print settings are based only around Cura slicer, which is when I learned about the adjustable seam position facility.

Re. being stuck with the seam near the leading edge. In Cura (not sure about Prusa slicer etc.) you can control the position of the seam. If you’re printing the wing sections vertically, can you not put the seam at the back and position the piece so the upper or lower corner of the TE is at the rear of the print platform. I discovered this recently when I built one of Planeprint’s models, and this is what they suggested doing. I found the seam barely shows then.

For a 4 servo wing with effectively 12 connections, I’d probably use a 15-way D-type connector as used in computers etc.. We used them a lot in military spec equipment when I worked in the aerospace industry. If they’re good enough for them, they’re good enough for me. I used the 25-way D-type below in a large twin engined model a while ago, and the connector has never given any problems. You can see that each soldered pin has heat shrink sleeve over it for reinforcement, in this case I think this is sufficient. But in other cases where more strength is required, other than fitting a backshell if convenient, I’ve partially potted the wires in hot melt adhesive if necessary.

Or crocodile clips.

Yep, I always use a brim with LW-PLA, which if find doesn’t stick to the bed as strongly as normal PLA. Doing this though, I’ve never had a failure even with tall thin wing parts. The printing instructions and Cura profiles supplied by Planeprint here are very comprehensive, and need following closely. In fact it took me several hours of settling up and saving the multiple profiles before I could even think of starting to actually print anything.

👍 I found with the LW-PLA that you have to print at about 230 - 240°C, otherwise it doesn’t foam sufficiently. I was reluctant to do too many test prints with the colorFabb as it’s quite expensive, and by the time I’d printed the parts for the Jetwing as well, I only had around 150g of the original 750g reel left. In fact towards the end I was getting quite nervous that it would run out and I’d have to by another reel just to finish the last couple of parts. Despite being supposedly ’light weight’ PLA, the model has turned out quite heavy, so I’m convinced it’s not as light as balsa.

I’d suggest colorFabb too. I built a Planeprint Jetwing EDF from it during the winter. As Ron mentioned above, there is also eSun LW-PLA which is available from Amazon, but doesn’t seem to get such good reviews generally in YouTube videos I’ve seen, although is a bit cheaper. Their so-called ‘natural’ colour also seems to come out somewhat more yellow than colorFabb’s. I bought my colorFabb LW-PLA from iDig3Dprinting here (I found it easiest to search for ‘LW-PLA’ on the site). Although they’re only showing grey/silver (note leccyflyer), red, natural and black in stock at the moment. My wing section test print .stl samples downloaded from Planeprint, when printed with Colorfabb PL-PLA came out at around 65% of the weight of the same piece printed using normal PLA. The Jetwing model below was printed using colorFabb natural LW-PLA. When it foams and expands in the hot end nozzle during printing, the natural (ivory/cream) coloured LW-PLA becomes somewhat more white in appearance because of all the bubbles trapped in it. The colours on the model were painted with artist’s acrylics, which seemed to take well to the rough LW-PLA surface.