adrian garnham Posted February 27, 2021 Share Posted February 27, 2021 Hi After watching a build and flight video on YouTube (Julius Perdana) showing construction of a Depron pusher prop Buckeye I thought I would have a go at designing my own version but using hotwire cut XPS foam sheets. I have made many balsa covered foam core wings in my youth (around 40 years ago !) and have designed and built a CNC hotwire foam cutter to use on this project. I have created a 3d model using CAD and unlike the Depron version I will be mounting the brushless motor at the front. Hopefully it won't detract from the appearance too much. Currently it is designed as follows: Wing span: 1200 mm Wing section: NACA 0015 symmetrical Wing Area: approx 0.27 square metres Airframe weight: approx 0.6 kg excluding motor and battery Expected flying weight: between 1.2 & 1.5 kg depending on battery size and whether I fit retracts or not Motor: Turnigy Aerodrive SK3-3536-1400kv V2 Prop: ? Esc: 60A Before I complete the design and start cutting foam I would welcome any feedback/comments on the above particularly with reference to the selected wing section, whether the motor will be powerful enough and suggestions for prop size etc. 1 Quote Link to comment Share on other sites More sharing options...
Timo Starkloff Posted March 1, 2021 Share Posted March 1, 2021 Nice choice of aeroplane ? A symmetrical NACA has no good stall characteristics on such a wing. It’s also quite thick. I can recommend SD6060 with the original 10% at the wing tip, thickened at the root to 12%. 2 degrees washout. Angle of incidence 0 degrees with your expected low wing load of 55 grams/dm2. 6060 will stall, too. But it is better controllable over a wide speed range. Aerobatics will be fine, too. And with that low wing load it will be easy to fly. Timo Quote Link to comment Share on other sites More sharing options...
Danny Fenton Posted March 1, 2021 Share Posted March 1, 2021 The motor will be a long way in front of the C of G, wont need nose weight that's for sure ? look forward to seeing how you progress. Cheers Danny Quote Link to comment Share on other sites More sharing options...
adrian garnham Posted March 1, 2021 Author Share Posted March 1, 2021 2 hours ago, Timo Starkloff said: Nice choice of aeroplane ? A symmetrical NACA has no good stall characteristics on such a wing. It’s also quite thick. I can recommend SD6060 with the original 10% at the wing tip, thickened at the root to 12%. 2 degrees washout. Angle of incidence 0 degrees with your expected low wing load of 55 grams/dm2. 6060 will stall, too. But it is better controllable over a wide speed range. Aerobatics will be fine, too. And with that low wing load it will be easy to fly. Timo Thank you Timo I was a little concerned about the thickness of the wing. I have looked at the SD6060 and will go with your recommendation. I'm changing the CAD this evening. Will post more info as I progress with the foam cutting. Quote Link to comment Share on other sites More sharing options...
adrian garnham Posted March 1, 2021 Author Share Posted March 1, 2021 1 hour ago, Danny Fenton said: The motor will be a long way in front of the C of G, wont need nose weight that's for sure ? look forward to seeing how you progress. Cheers Danny Danny As I am designing this myself and the CAD program calculates the theoretical C of G for me I should be able to move the battery wherever I want. Fingers crossed LOL 1 Quote Link to comment Share on other sites More sharing options...
Timo Starkloff Posted March 3, 2021 Share Posted March 3, 2021 Put the tail servos aft, short linkage is another advantage. As you said, with accumulators moving the COG is easy if the motor is not too heavy. A thickened RG15 will work, too, but the result will be not very different to the 6060. And both airfoils are tested with thicker trailing edges, which may be the case with your building material. Jet like flying due to low drag, slow landing speed due to low wing load. That's the same basic aerodynamics as on modern rc gliders. Good luck ? Timo 1 Quote Link to comment Share on other sites More sharing options...
adrian garnham Posted June 4, 2021 Author Share Posted June 4, 2021 Finally made a start on the Buckeye. Fin and tail plane assembly completed Motor & retractable nosewheel mount completed Battery mount and wing brace assembly complete . Now I am testing out the 4 axis cnc foam cutter and fine tuning for correct wire speed, temperature and kerf allowance before cutting the fuselage sections and wings. 20210604_170343_Trim.mp4 2 Quote Link to comment Share on other sites More sharing options...
adrian garnham Posted June 6, 2021 Author Share Posted June 6, 2021 Cut all the fuselage sections ready for gluing together ... 3 Quote Link to comment Share on other sites More sharing options...
alan p Posted June 6, 2021 Share Posted June 6, 2021 Now this does look interesting? 1 Quote Link to comment Share on other sites More sharing options...
adrian garnham Posted July 1, 2021 Author Share Posted July 1, 2021 Bit more progress today. Wings hot wired and pockets for servo and undercarriage cut using my CNC router. 3 Quote Link to comment Share on other sites More sharing options...
adrian garnham Posted July 1, 2021 Author Share Posted July 1, 2021 CNC router in action 20210701_131350.mp4 Quote Link to comment Share on other sites More sharing options...
adrian garnham Posted July 27, 2021 Author Share Posted July 27, 2021 Fuselage sections glued together using clear gorilla glue. Now on to the sanding and finishing. 2 Quote Link to comment Share on other sites More sharing options...
Graham Davies 3 Posted July 27, 2021 Share Posted July 27, 2021 Fabulous Alan. way beyond my capabilities, but fabulous none-the-less. Graham 1 Quote Link to comment Share on other sites More sharing options...
adrian garnham Posted August 29, 2021 Author Share Posted August 29, 2021 Almost finished. Just waiting for 60A ESC then I can play around with positioning for balance and then find someone to maiden it for me. If it flies I'll post a video ... if not then I guess its back to the drawing board !! Came out heavier than expected at almost 1.7 Kg 3 Quote Link to comment Share on other sites More sharing options...
alan p Posted August 29, 2021 Share Posted August 29, 2021 Definitly looks right? 1 Quote Link to comment Share on other sites More sharing options...
Trevor Posted August 30, 2021 Share Posted August 30, 2021 It looks great and a very interesting construction method. It may be an optical illusion but in some of the photos it looks like the tailplane may have positive incidence in relation to the wing. If so, I think it could need a fair bit of visible up elevator trim. Good luck with the maiden. Trevor Quote Link to comment Share on other sites More sharing options...
adrian garnham Posted August 30, 2021 Author Share Posted August 30, 2021 1 hour ago, Trevor said: It looks great and a very interesting construction method. It may be an optical illusion but in some of the photos it looks like the tailplane may have positive incidence in relation to the wing. If so, I think it could need a fair bit of visible up elevator trim. Good luck with the maiden. Trevor Thank you for your comments. I think you are right although the photos make it look worse than it is. If the maiden goes OK and requires too much trim i'll redo the tailplane. Quote Link to comment Share on other sites More sharing options...
Martian Posted August 30, 2021 Share Posted August 30, 2021 Excellent build novel and fantastic construction good luck with the maiden Quote Link to comment Share on other sites More sharing options...
Mike Chantler Posted August 30, 2021 Share Posted August 30, 2021 I built a cnc foam cutter recently as well for a project but just used it for the airfoils, so very interested to see your fab fuselage. Looks really nice. Did you have any problem with the gorilla glue when you sanded the fus? Or did you just keep the glue well away from the fus surface? Quote Link to comment Share on other sites More sharing options...
adrian garnham Posted August 30, 2021 Author Share Posted August 30, 2021 1 hour ago, Mike Chantler said: I built a cnc foam cutter recently as well for a project but just used it for the airfoils, so very interested to see your fab fuselage. Looks really nice. Did you have any problem with the gorilla glue when you sanded the fus? Or did you just keep the glue well away from the fus surface? I used the clear gorilla glue spread very thinly for the fuselage joints. Sanding in one direction across the joint seemed to work well. I filled any dings etc with lightweight filler before priming with acrylic primer. Quote Link to comment Share on other sites More sharing options...
Mike Chantler Posted August 30, 2021 Share Posted August 30, 2021 Thanks Adrian. Finish looks very good, guess the trick is to keep the glue thin ? Quote Link to comment Share on other sites More sharing options...
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