We were asked by the factory awhile back for a wish list on what we would improve with the KiwiProp, so we asked our customers. Everyone was pretty happy, but since a high percentage were moving from a fixed 3 blade prop to the KiwiProp, a common compromise was motoring performance. Manufacturers will make all the claims they want, but the fact of the matter is that a well designed and optimized 3 blade fixed propeller is the best thing for motoring forward. They generally suck in reverse, and of course sailing you’re dragging a bucket, but let’s give them their due, they do move the boat. Now you will notice that I said optimized. A fixed 3 blade propeller is always a best guess, after you put it on, it is what it is, and very few owners will try a few different propellers before settling on the best one. It has been our experience that 2/3 of the boats on the water do not have the optimal fixed propeller mounted, more like what was available, or close enough.
How else do you explain customer feedback like ‘We picked up a half knot motoring speed at our cruising rpm over our old fixed 3 blade’. The ability to fine tune our props for motoring is something you simply can’t do with a fixed prop.
So back to the wish list. The factory has been busy playing with the latest in hydrodynamic simulation software- forget tank tests, this stuff is kewl. We’ve seen preliminary data that suggest that there is a 20% improvement out there without a measurable trade off in reverse or drag when feathered. We always suspected it was there, but there was something elegant and cost effective about our symmetrical blade design.
Picture a driving face similar to our latest design with the trailing edge wedges and extra surface area where the speed is the highest, then remove some of the material on the other side that you don’t need and approximate the nice ogilval shape you see on all fixed propellers. Next up it material analysis to make sure the blades are still strong and stiff enough, but the chemical engineers who design our custom Zytel formulation are up to the task.
We hope to have some of these blades for our own trial late this year for a release early 2015. The great news is that they will be retrofittable on all of our existing props out there. What a great upgrade!