As we're without a mast, it seems fitting to give some love to an important part of the motoring system on the boat: the propellor.
The propellor, or prop, is a fan-like structure submerged in the water and connected to the engine via the prop shaft. Its job is to convert rotational energy from the shaft into thrust within the water, thus moving the boat forward. The critical design aspects involved are the shape and design of the blades that skull through water; the extent to which those blades can rotate efficiently; and how much drag they produce while we're using sail power.
The boat came with a fixed prop which showed a little wear:
We decided on the Max-Prop Easy because all four of the blades swivel completely around the center of the prop. Meaning, not only is the prop efficient while we're moving forward, but it maintains the same efficiency in terms of energy and steering when we're in reverse. This is insanely cool for a prop! And particularly advantageous for us--Helios' full keel can make navigating in reverse a bit clunky.
The other huge bonus is that when the prop isn't in use, the blades can still rotate. So while under sail, all four blades are parallel to the flow of the water and cause minimal drag. We're hoping the prop spends most of her time in this relaxed, stress free position. You can check out a 3-D animation of the prop rotation here. While the small amount of reduction in drag may not be a big deal for the average boat sailing on San Francisco Bay, it will definitely pay off during our extended ocean passages.
The installation was something of a process. First, Dominic sprayed the prop with a zinc barnacle barrier to keep the prop clean and act as a sacrificial metal (meaning it will corrode before the bronze of the prop). Then, we called up our friend Matt at Fast Bottoms to do the install. It would have been pretty quick had it not been for one ill-fitting piece of key stock that required some heavy duty filing. So the project took two days, but was pretty straight forward.
And now we have a fabulous new prop! Cheers!