One can not deny that it is a true work of art and a beautiful thing to see in action. Really slick. It’s sort of a hybrid between feathering and folding as the blades swing around for reverse giving the same profile advantage as in forward action. It’s hard to describe the action but the blades swing on an axis perpendicular to the prop shaft. When you go to neutral they fold up like a conventional folding prop. When you go to reverse the unfold in the other direction (they continue swinging from forward-open to folded to reverse-open). You really need to see it (what I can’t resist each time when visiting a boatshow). The prop is a beautiful polished bronze. I’m talking about the Gori 3-blade folding prop …..
Two speed propeller.
My search in the huge array of folding and feathering props has been narrowed down to four potential candidates; Kiwiprop, Maxprop, Flexofold and Gori. There is much to say about these props (and all the others not mentioned here), but I will not do. Being not very scientific and trusting my gut feeling I have examined only these four types in more detail. I don’t think a feathering prop is suitable for speeds above 15kn and besides of that, the folding type has less drag. So in the end the real choice is between Flexofold and Gori. No idea which is best and test results in the various magazins aren’t of any help either as the outcomings are so different per test. The Flexofold is cheaper but the Gori is more appealing for my needs, especially the overdrive function for use during windless periods (what is the major circumstances where the engine is in use, I hope) and the power in reverse, which (to my surprise) is even better than a fixed prop.
The Gori look much like any other contemporary folding propeller, with blades that are geared at the base and open on hinge pins. What’s different is that the blades can open in two different directions so that either side of the blade can become the leading face when in forward gear.
The “pitch” of a propeller, which is a measure of how aggressively it bites the water, is determined by the shape of the forward faces of its blades. Gori blades are machined with the hinge pins slightly skewed. When opened in the “normal” direction, the blades have one pitch; when opened in the opposite direction, the other side of each blade becomes its forward face, with approximately 20 percent more pitch. Gori calls this the “overdrive” mode. Putting the propeller into overdrive increases the boat’s speed at any given engine speed. The immediate benefit to the overdrive mode is that the engine runs slower for a given boatspeed and creates substantially less noise and vibration. This results in a 20 percent longer cruising range in overdrive (according to Gori)
Time will tell whether the Gori propeller is equal to the task of maneuvering Fram and bringing her to the desired destination during calm wheather or end up as an expensive piece of art on the coffee table.