The propeller is more or less the final part of the equation once the motor and drive train has been figured out for your DIY Electric Hydrofoil. The prop is the part of the boat that transfers the energy from the motor to the water. This transfer of energy is called thrust.
Thrust is created by the propeller blades pulling water from in front of the prop (boat side) and then pushing the water outward and backward. This pull/push effect is taking water from a low pressure to the high pressure and its this change in pressure that creates thrust.
In my previous post talking about 3D printed and other props I shared the key things one must understand when selecting/creating a propeller.
Ducted Propellers I believe should be used for a couple of reasons. The main one to me is actually safety. I keep seeing people build and test boards with no protection from the propeller, and its just a matter of time before someone loses a lot of blood or worse…
The second reason our DIY electric hydrofoil boards should have a ducted propeller is that a properly designed ducted prop can have up to 30% more power (thrust) than an open bladed propeller.
Those of you who understand exactly how a ducted propeller works along with its efficiencies and inefficiencies know that ducted props are most efficient at lower speeds up to 11-12kt. YES, you are correct but keep these points in mind..An electric hydrofoil
An electric hydrofoil requires a lot of power are low speeds to get moving, but once it’s moving and up on foil the board becomes so efficient, the motor just needs to maintain speed. The high efficiency of the hydrofoil wing compensates for the ducted propeller at higher speeds when the prop is not 100% efficient.
Just take a look at the prop slippage table below for different types of boat hulls. This does not show an electric hydrofoil board or any hydrofoil hull for that matter, but I’m guessing the slippage for a prop on a DIY electric hydrofoil board would be 4-6% range, maybe lower.
Watch this video about how and why ducted propellers work and I promise you will learn something new…
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