Simon Chaddock Posted January 26, 2023 Author Share Posted January 26, 2023 That printed P13a has the EDF up the front which is logical as it apparently exhausts just aft of the landing skid. From what I have seen of the bits there is no 'through' duct. Indeed the manual download suggests that the battery has to go well back to avoid having to add significant tail weight. As far as I can tell my Depron P13a is so light that the battery will indeed end up in the Cockpit area. I am actually tempted to buy the STL files if only to what sort of a job it makes. However with STL files it is not at all easy to modify them to include a proper 'through' duct. 1 Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted February 6, 2023 Author Share Posted February 6, 2023 The wings on, such as they are! An incredibly 'bluff' leading edge. The sort of thing used on the Whitley bomber and to make matters worse it is sweptback 60 degrees! About the best you can say it is a lifting body! So far it is very light, less than 180 g including the EDF and ESC, so I am reasonably confident it will have the thrust to fly but rather less so as to whether it will be controllable even with the benefit of a 'stab' rx! Elevons next. The only reason I even contemplated building the Lippisch was that my HP 115 which is almost as extreme aerodynamically actually flies really quite well. Although with a similar EDF and all up weight its relatively thin sharp leading edge wing section is more suited to a delta and it has nearly twice the wing area. I fear the Lippisch will be an aerodynamic step too far. We shall see. 5 Quote Link to comment Share on other sites More sharing options...
cymaz Posted February 6, 2023 Share Posted February 6, 2023 Fancy the idea of a gyro in it ?? Quote Link to comment Share on other sites More sharing options...
tiny-james Posted February 6, 2023 Share Posted February 6, 2023 Looking forward to seeing this plane fly Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted February 7, 2023 Author Share Posted February 7, 2023 On a bit further with the elevons fitted and the servo installed. Note the Lemon 'stab' rx sitting in its Depron box. It is easily removable as I know from past experience getting delta elevons to work correctly from the sticks and to react correctly to an external input takes quite a bit 'trial and error' fiddling. The rudder will also be stab controlled but as a single surface is much easier to set up. With such short control surface moment arms my confidence is not improved that it will 'controllable' let alone nice to fly! Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted February 9, 2023 Author Share Posted February 9, 2023 With the elevon servos connected the game starts of getting it all to work correctly. Which eventually it does. https://www.youtube.com/watch?v=Ciy82muNXVo Apart from setting the 'delta' dip switch on the rx. The servos had to swop channels on the rx.. They then had to be reversed on the DX6i. Finally the servos had to be reversed via the rx dip switches. Slowly getting there. 🙂 1 Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted February 13, 2023 Author Share Posted February 13, 2023 Finally organised the battery box si the fin, with the rudder servo could be glued on. The cockpit cut out is actually oversize simply because it also acts as the battery hatch. Note the battery box (for a 1500mAh 3s) is offset slightly to the right to counter the weight of the ESC on the left.. Still the quite substantial nose skid to do. It will not be vital for landing but it will be used as a 'hand hold' for launching. Given it is entirely white Depron it will just a have light 'wash' of acrylic white with some detail picked out in black to help establish which way up it is! 5 Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted February 14, 2023 Author Share Posted February 14, 2023 (edited) Nice and sunny so a picture of it virtually complete taken outside! Being all white the low angle sun rather over exposed the camera. It has still got to be about the most unlikely EDF. Edited February 14, 2023 by Simon Chaddock 1 Quote Link to comment Share on other sites More sharing options...
MattyB Posted February 14, 2023 Share Posted February 14, 2023 (edited) It does rather resemble a tailplane that you forgot to attach the front half of the fuselage to... 😉 Edited February 14, 2023 by MattyB 1 Quote Link to comment Share on other sites More sharing options...
cymaz Posted February 14, 2023 Share Posted February 14, 2023 Ah, the looks only a mother could love. No, seriously, great effort and may she fly and land safely Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted February 15, 2023 Author Share Posted February 15, 2023 The Lippisch is now complete. All white except for black control surfaces and of course the exhaust nozzle. The substantial nose skin is black to make the underside different. Working on the principle if you can't see the black skid - it is inverted! It weighs 373g (13.1 oz) ready to go. No great surprise but its completion has coincided with a forecast of gales and that is after a long(ish) period of extraordinarily calm conditions. Oh well! I will just have to wait for the right conditions to find out that it is unlikely to fly. 2 Quote Link to comment Share on other sites More sharing options...
MattyB Posted February 16, 2023 Share Posted February 16, 2023 I don’t understand why you are so pessimistic about this one… It is well built and thought out (as with all your model), light enough and not too unconventional in terms of planform. I agree it’s unlikely to be that efficient given the ducking you’ve had to use, but I can’t see any obvious reason why it wouldn’t fly controllably - certainly that 3D printed version seemed to be fine. Be positive! 2 Quote Link to comment Share on other sites More sharing options...
MattyB Posted February 16, 2023 Share Posted February 16, 2023 3 hours ago, MattyB said: I don’t understand why you are so pessimistic about this one… It is well built and thought out (as with all your model), light enough and not too unconventional in terms of planform. I agree it’s unlikely to be that efficient given the ducking you’ve had to use, but I can’t see any obvious reason why it wouldn’t fly controllably - certainly that 3D printed version seemed to be fine. Be positive! Ducting, not ducking! Ducking will only be needed if my hypothesis is wrong...! 😉 Quote Link to comment Share on other sites More sharing options...
Jake Bullit Posted February 20, 2023 Share Posted February 20, 2023 P13a is now available in Phoenix simulator, if you need some stress free practice. https://youtu.be/w-HvyCaNK90 1 Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted February 24, 2023 Author Share Posted February 24, 2023 (edited) To my surprise it does fly but it did not last very long! 😟 Shortly after the launch it started to wobble in roll. My immediate thought was the roll gyro gain was to high so I decided to land asap. It kept flying rather fast but the roll wobble made is very difficult to control the direction of flight. Now the field I fly in has a rugby goal post, just one, and you guessed it the Lippisch hit it hard just off centre. No damage to the EDF or duct, in fact it kept working, and the gyro made a good job of keeping level to allow a soft pancake landing with no further damage however the delicate Depron wing structure did not fare so well. It does however show the absorption qualities of a hollow Depron structure. There is no other damage. Whilst an 8 second long maiden with substantial damage might be considered a failure, the fact it flew more or less controllably means I consider it a success. In hind sight I am now pretty sure the roll wobble may have been aggravated by too much 'give' in the top tape hinges, particularly as in roll the elevons are huge compared to the size of the wing. On the rebuild the elevons will be given proper 'pin' hinges. 😉 We live and learn. Edited February 24, 2023 by Simon Chaddock 7 Quote Link to comment Share on other sites More sharing options...
J D 8 Posted February 24, 2023 Share Posted February 24, 2023 Saw or angle grinder needed depending on post material.😈 Quote Link to comment Share on other sites More sharing options...
MattyB Posted February 24, 2023 Share Posted February 24, 2023 22 minutes ago, Simon Chaddock said: ...Now the field I fly in has a rugby goal post, just one, and you guessed it the Lippisch hit it hard just off centre. If there had been a forest of posts you'd never have managed to hit one. Next time do a test flight at a rugby club! 😉😁 2 Quote Link to comment Share on other sites More sharing options...
PeterF Posted February 24, 2023 Share Posted February 24, 2023 Reminds me of the time I flew my Ripmax Spitfire belly lander in winter. Our flying field had a few horses in, there was a pile of horse droppings at the edge of the runway, 100m x 80m to land in but one wing hit the pile and it turned out to be frozen solid. Quote Link to comment Share on other sites More sharing options...
Trevor Posted February 25, 2023 Share Posted February 25, 2023 Congratulations on achieving (more or less) controllable flight with such and odd subject. I'd suggest taping on a fin extension for future test flights to provide a bit more yaw damping, on the basis that that wing shape will give a very strong yaw/roll coupling which could be the main cause of the roll oscillation you were seeing. Good luck on the next flight, Trevor Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted February 25, 2023 Author Share Posted February 25, 2023 As high pressure is approaching the UK, = little or no wind, I have pressed on with the repairs. Now complete. Surprisingly no new Depron added just the existing straightened and glued back in place. It needed a great deal of masking tape strips to hold in all in place whilst the glue dried. I can guarantee the root wing section is exactly the same but with such bizarre aerodynamics I doubt it will make any difference. The elevons now have proper acetate pin hinges. Much better! Possible try again tomorrow (Sunday) but only if it is really calm. 8 1 Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted February 28, 2023 Author Share Posted February 28, 2023 (edited) Calm in the morning 2 days ago so I tried again. Better. It actual completed a short circuit and passably under control but, and there is always a but, it does exhibit some tricky characteristics. Go too slow and it just continues to slow down and enter a severe full stall but speed up and it gets very pitch twitchy with a tendency to execute an un commanded dive. Which is exactly what it did and I was not 3 mistakes high! That intake makes a good plough.😲 The sudden stop caused the battery to break free and crush the duct. A view up the exhaust. And as usual everything still worked where it lay! As the whole airframe was constructed around the completed duct repairs are going to require some serious surgery. High pressure still lingers around the UK so its a case of press on with the repairs - again! First cut open the top of the fuselage back to the cockpit and extract the EDF and all damaged parts of the duct. Then it is several hours of 3D printing in LW-PLA! Edited February 28, 2023 by Simon Chaddock Quote Link to comment Share on other sites More sharing options...
GrumpyGnome Posted March 1, 2023 Share Posted March 1, 2023 Got to admire your tenacity Simon........ Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted March 1, 2023 Author Share Posted March 1, 2023 Its not so much tenacity as frustration as it so nearly flies. The new duct work installed. And after much trial and masking tape to hold things whilst the glue dried its all back together. It has added a few grams but it is mostly ahead of the CofG which should actually help. The next calm day. 😉 Quote Link to comment Share on other sites More sharing options...
J D 8 Posted March 1, 2023 Share Posted March 1, 2023 Long grass in the old free flight testing needed? Quote Link to comment Share on other sites More sharing options...
alan p Posted March 1, 2023 Share Posted March 1, 2023 Definitly showing true Grit💪 Quote Link to comment Share on other sites More sharing options...
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