SYNERGY - a collaborative DS project.
Over a year ago we a bunch of us got together on a collaborative DS plane design project. The outcome was the Synergy and the prototype had its DS maiden at Tekapo yesterday.
The Synergy collaboration guys are:
Andrew von Berky (AvB) - design, CNC mould cutting.
Will Deighton (Wdeighton) - design and Catia CAD.
Alex Hewson - design, flight testing
Geoff Sokoll (Geoff_S)- design, Rhino CAD, aerofoil analysis/ optimization
Josh Callaghan (Josh18)- design, prototype building
Sean Moloney - aerofoil.
We set up a private forum for our collaboration. With Josh initially in Victoria, Alex in NZ and Will in the UK, there was plenty of Skyping as well as forum discussion. Into our melting pot of discussion, experience and ideas we tipped everything we’d learnt from watching amazing planes like the Kinetics, Deepend, and our experience from our own homebrew builds, which led to the following aims and concept:
• 2.8 metre (110.2”) span 3 piece wing with small-ish tips.
• High aspect ratio and capable of being flown into WR territory, but with the planform a bit softened back from “ultra extreme” to make concessions for ease of launch and landing.
• Split flaps.
• Chunky long joiners to double as ballast.
• Fuselage fairly chunky in the nose and with some body under the wing seat for ease of holding/ launching.
• Filleting of wing to fuz and stab to fin to be incorporated into the CNC cut female moulds.
• Nose cone.
We looked at using a DP foil, but due to various considerations we decided to go with some locally designed DS specific foils. Sean had done a lot of work on designing some yet-untested DS foils and kindly allowed us to use one. Geoff (who qualified as an aeronautical engineer) using a great foil analysis tool that he’ll mention later, crunched numbers to get optimised aerofoils at multiple locations across the wing span for a range of operating conditions. Ultimately though we settled on one of Sean’s foils for the root section, blending into a custom profile at the tip.
Drawing and redrawing by Will and Geoff took quite some time as once we all saw the drawings we got more and more picky and demanding requiring many changes! Fortunately Will’s Catia drawings are via STL very compatible with Rhino, which is Geoff’s CAD program and which AvB uses in conjunction with Madcam to create toolpaths.
The moulds were cut from Corian/ Freestyle solid benchtop materials using AvB’s machine between June and August. AvB was daunted by the prospect of cutting these moulds which were far more complex that the work he’d done so far. Geoff’s Rhino skills as well as his clever ideas on ways to use inserts to create seemingly impossible shapes in the moulds meant that one step at a time, the cutting progressed smoothly and rewardingly. First the relatively simple stabilizer. Then the wingtip moulds with joiner alignments etc. The big centre panel utilizing crafty methods for centre shapes and fillets. Fuselage using inserts for fillets and nose cone step. A swanky CAD/CNC fuselage joggle gasket mould, and later a nose cone mould. Before we started it had seemed like an unclimbable mountain but it definitely felt when we had got to the top and all the moulds were done and looked good.
Josh, who by then had been moved up to Toowoomba (just 2 hours away) got the moulds in stages as they were completed and took on the massive job of polishing them and building the first Synergy prototype model. Josh works full time on choppers with the army, has a young family, and was on a timeline to be transferred to Darwin (where he won’t be building planes for a while) so he burned the midnight oil and crammed in every spare minute to get things done as best he could. It was a big rush, and it’s a massive task to build the first of any model, let alone a 3 piece wing job.
Finally the day before Josh moved he brought back the moulds and the parts, and very soon the hastily built prototype was shipped over to Alex.
Prototype or not, they all take expensive servos and lots of fiddly setup time. It took Alex a couple of weeks of spare time to get the model set up.
The fitout was finished last Saturday morning. On Skype the bags under Alex’s eyes from the recent late nights were obvious … but there was enough wind for a maiden so after lunch, it took to the skies for the first time at Allandale, Christchurch with light joiners and a conservatively forward CG. We were all on edge for news! There was barely enough wind - Alex scratched around barely gaining height using full camber for 6 minutes and eventually had to land down-slope, fortunately in lovely soft grass. Not much opportunity to suss out “how she flies”, but at least we knew that it did. Will in the UK finally went to bed around 3am, happy to have finally heard the good news!
Next day (Monday) was a big Tekapo forecast so Alex had the day off work. After a painfully slow drive down (holiday tourist traffic on narrow twisty NZ roads!) the Tekapo ridge was baking hot, the wind was hot and changeable, but overall it was strong and a good direction. First dive-in, after 4 or 5 laps at 250mph, a slightly embarrassing “minor structural flap issue” (ahem) required an early landing and the best that could be done was a very bodgy fix. AvB trying to catch up on work was madly taking texts and calls and posting the news on the forum. Next flight, impaired by the repair, it was DSed hard in the up-and-down air, really locked in, felt comfortable to fly and despite making jet turbine loose-tape noises due to the daggy repairs, got 342mph. But the Synergy is very slim and like the K2M, really “disappears” coming out of the bottom turn - and it is hard to get reads on the gun. A slightly smoother repair was done and a 3rd flight late in the day, as the wind was easing, yielded 358mph. So although it was a bummer that we didn’t get to see how fast the clean ship would go, the most important news was very positive … it felt great to fly, was locked into the circuit, and was easy to launch and land. By comparison the K130 got to 388 after the Synergy’s second flight.
Next step is some more test flying, get a better second prototype built and flown, and we expect to make some small changes to the airframe after enough flight testing before embarking on cutting the sets of final moulds.
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Has been a long road to this point and still more to go yet as we enter the CG and rate testing phases as well as building a second and third prototype. I feel the design has a lot of potential.
CG and rates weren't ideal for the first few flights and didn't get it into the best air of the day. Is really hard to pick up on the gun compared to the K130, and the yellow disappeared against the Tekapo background, so there were a few things stopping getting the most out of it yesterday. I have no doubt 400+ was there, but the wind was so up and down, and having so many planes to fly and work to do on the rock wall, it missed out on getting thorough testing and tuning.
Summer has only just begun here, so testing will continue...
you guys what? Holy !!!
That´s probably the biggest International DS Project ever, big thumbs to all involved.
Looks slippery and WR capable that´s for sure!
Can´t wait to see how it´ll perform in Socal 2016
It really makes me want to build something like that, if only I had wind for that
Nice work guys! The Synergy looks awesome! Looks like it ticks all of the list of goals. Looking forward to more Tekapo reports on that one. Hope it survives long enough to see it at Weldon in April! 110" is a nice size. Nice job on the moulds Andrew!
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