Simon Chaddock Posted July 5, 2023 Share Posted July 5, 2023 (edited) It is well known that 'pushers' tend to be noisy due to the prop and the airflow from the wing trailing edge interacting. Putting a prop in a slot in the wing is even worse. Such an arrangement is the basis of any siren! Obviously the faster the prop, its diameter (i.e. the power involved) and the closer it is to the wing edge the louder the noise. For reasons mainly for prop protection I have built several pushers of various configurations. The quietist considering the power involved was the Cessna Skymaster. With the rear prop some distance from and a bit below the wing trailing edge meant the pusher prop itself added virtually no 'extra' noise. My most powerful (380W) is a simple pusher. The motor is set back to give a full 2" clearance between the prop and the wing trailing edge. The motor rearward placement is actually a benefit as it eases placing the battery in the nose. The prop is a relatively large diameter with a low kV motor so the full power noise is at a lower frequency than the high pitch whine of a small diameter prop. Indeed fly gently at 400' and you really can't hear it above any background noise. Nothing earthshattering but it does mean my pushers are quiet! Edited July 5, 2023 by Simon Chaddock Quote Link to comment Share on other sites More sharing options...
John Lee Posted July 5, 2023 Share Posted July 5, 2023 9 minutes ago, Simon Chaddock said: The quietist considering the power involved was the Cessna Skymaster. Agree with your comments Simon but that is quite surprising as the full size was banned from a number of UK airfields because of the noise, we used to have one (G-BATH) based at our flying school at Liverpool in the 70's. Nowadays the Piaggio P-180 Avanti is an irregular visitor and its very distinctive noise that can be heard several miles away. Quote Link to comment Share on other sites More sharing options...
Rich Griff Posted July 5, 2023 Share Posted July 5, 2023 Simon, may I ask, the Cessna, based on the free plan from many years ago, a solid plank wing sanded to some sort of aerofoil ? It didn't glide well and was a real handful ! One of these is on my "to make" list but much lighter this time with a proper aerofoil wing, probably Clarke y to keep it simple. Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted July 5, 2023 Author Share Posted July 5, 2023 (edited) Rich It was an own design built almost entirely in 3 mm Depron from this 3 view. It was flown as a hand launch/belly lander. Conventional ribs with wood flanges top and bottom on the single spar. Most of the wing stiffness came from the Depron skin. The fuselage was formers with a planked skin again all in 3mm Depron. The wing braces in hard balsa were also functional. With a 1320 mm span (52") it was indeed light at 646g (22.7 oz) with a 2200mAh. Plenty of power. One motor could be switched off in flight. Even then it still had a quite adequate performance. All in the past tense as it crashed badly, my own fault, but it was by then 7 years old and had done quite a bit of flying. Edited July 5, 2023 by Simon Chaddock Quote Link to comment Share on other sites More sharing options...
Simon Chaddock Posted July 9, 2023 Author Share Posted July 9, 2023 Not that I would really recommend doing this sort of thing but in truly calm conditions with a light and well trimmed plane low level slow manoeuvring is safe enough. https://www.youtube.com/watch?v=HFBf4XFpTzU&t=2s Having plenty of spare power (unlimited near vertical) does improve the confidence to quickly get out of trouble. Quote Link to comment Share on other sites More sharing options...
Erfolg Posted July 10, 2023 Share Posted July 10, 2023 I have built many models with pusher motors, a couple of flying wings, and a Dornier 335 (the picture attached is the one currently being built, as I do not appear to have a picture of the NITRO MODELS D335). Non have been noisy at all, the delta had a frequency beat from the two motors. My experience suggest that it is the Yagi? types with the prop adjacent to the TE of the wing that are noisy as a combination of high rev( high KV) small propeller type situations. Quote Link to comment Share on other sites More sharing options...
Graham Bowers Posted July 10, 2023 Share Posted July 10, 2023 18 hours ago, Simon Chaddock said: Not that I would really recommend doing this sort of thing but in truly calm conditions with a light and well trimmed plane low level slow manoeuvring is safe enough. https://www.youtube.com/watch?v=HFBf4XFpTzU&t=2s Having plenty of spare power (unlimited near vertical) does improve the confidence to quickly get out of trouble. Given that buildup I was expecting it to be plucked from the air with teeth 😉 Quote Link to comment Share on other sites More sharing options...
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