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Propeller pitch


Basil
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Bas,

 

Without knowing very much about your model and it’s power train it’s perhaps a little bit difficult to make any suggestions but as regards slow scale style flying this might just be something of a little pointer. A prop with a 6 inch pitch turning at (say) 8,000rpm will give you a theoretical forward speed in level flight and still air of about 45mph; a 4 inch pitch spinning at 10,000rpm will move forward at approximately 38mph whilst a 3 inch at 11k will only achieve a mere 31 miles to the hour. As said, these are very much ‘roundabout’ figures, there are other little factors always waiting in the wings? (sorry) to come into play, such as ‘prop slip’ and ‘props unloading’ etc.; but I’d try a bit experimenting and a few test flight and it shouldn’t be very long before I’d have a very good idea how the model was going to fly. Or not, maybe…. A bit of a moot point perhaps, but I tend to just use a tacho as my sonic screwdriver, followed by a contact thermometer looking for hotspots if I’m suspicious and sometimes a clip on power meter just to confirm what I’ve estimated the current flow to be. All part of the fun!

 

Good luck with your model!

 

PB         

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