A Guide to Folding Propellers for RC Planes

What is a folding propeller?


Unlike a fixed propeller attached to a radio controlled plane, when we say "folding propeller" we are usually referring to one or more parts which comprise the entire mechanism of the folding propeller. These parts usually include some kind of motor shaft attachment such as a collet type adaptor, a back-plate on which a spinner cap is seated, the spinner cap itself and probably the key element: a yoke (often referred to as a centre-piece, middle-part or prop bar). Of course, the setup would not be complete without the folding propeller blades themselves! By contrast, when we talk about propellers in the realm of RC models using fixed or non-folding setups, we generally mean literally just the propeller!

What are the parts of a folding propeller?


For the purpose of this simple guide, we will talk about the following parts: -
  1. Adaptor – the part that attaches to the motor shaft, on to which everything else is mounted
  2. Back-plate – the part that fits onto the adaptor and on which the spinner cap and yoke are seated
  3. Spinner cap – the optional spinner cap that improves aerodynamic efficiency and makes everything look pretty
  4. Yoke or middle-part – this part also slides over the adaptor and the propeller blades attach directly to it

Please see the diagram below for some examples of these parts.
rc folding propeller components


In the image you can also see three parts which we have not mentioned. There are a nut, bolt and washer. These are generally included with most RC spinners and definitely with the Aero-Naut spinners that we sell. The parts are the spinner cap securing screw and then the nut and washer that secure the yoke against the back-plate and importantly also tighten the adaptor against the motor shaft when tightened up. The latter mentioned nut and washer are usually included with the adaptors that we sell. More on that later, but in case you're curious, the diagram actually shows an Aero-Naut Precision Spinner, which you can buy right here on our website!

Of course, we have missed a our key element! Component No.4, which allows the folding propeller blades to be mounted. Here it is:

a folding propeller yoke
The folding propeller yokes (Also called middle-part, centre piece or prop bars) sold here also include the fixing screws and nyloc nuts for the safe and secure fitting of your folding propeller blades.

Yoke Compatibility


Inevitably, when many components are involved, there arise compatibility issues. The gap in the ends of the yoke where the folding propeller blades are seated is unfortunately not consistent between manufacturers of these components. Aero-Naut yokes are great, because Aero-Naut have standardised on an 8mm gap – happily all Aero-Naut folding propeller blades have an 8mm blade root, which means that any Aero-Naut folding prop blade will fit your Aero-Naut folding prop yoke. Watch-out for Graupner folding propeller blades – whilst these offer great value and performance (Just like the Aeronaut blades!), Graupner have not standardised on their blade root and these vary from 4mm for the tiny blades up to 10mm for larger sizes.
All Aeronaut folding propeller yokes have an 8mm gap to match their propeller blades. Check the diagram below:

blade root correlation with yoke gap

How to choose a folding propeller


If we forget the propeller blades for a moment, there are three things to figure out before choosing a folding propeller: -
  1. The diameter of your motor shaft
  2. The diameter of the nose of your model
  3. The diameter of yoke to use

Choosing (1) and (2) is quite straight-forward, as most spinners for folding props are packaged with the shaft adaptor and you will see folding propeller spinners listed for example as 50mm spinner for 5mm shaft. From there, if you stick with Aero-Naut, it is just a question of what size propeller blades to choose based on your motor specification and the number of cells you are using (a whole other subject!) Choosing (3) is also relatively simple; Aero-Naut recommend choosing a yoke at least 2mm larger than the spinner diameter, this means for a 50mm diameter spinner, you should choose a 52mm or greater yoke.

Our Folding Propeller Setups



Thanks


We hope you enjoyed this guide. Your comments and questions are always welcome!

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