UKF5B F5B as it happens
F5B props are designed for very high speeds and so often have a very high pitch which will prevent them from folding flat to the fuselage. This creates more drag on the glide which we definitely don’t want.If a prop hub is made with the blades offset from the centre line it will help the blades fold flatter against the side of a circular fuselage.
Another approach is to make the prop blades with a lower pitch than required so they will fold flatter, but use them on a special hub with extra “twist” at the blade mounting to get the right pitch when open. For example the RFM 17×18 props are only 17×18 when used with a hub that has a blade twist of +5 degrees.
Hubs with both twist and offset are quite common in F5B.The RFM site explains which of their blades need the special hubs.
