Why are they machining this out of a solid block of aluminum, instead of investing in foundary tooling so they can cast these ?
What aluminum alloy are they using? It doesn’t say, and matters a lot for marine durability.
Each has three variables: diameter, pitch, and rotation. So a different set of molds for casting are needed. Having some experience with aluminum castings, they tend to break rather than bend in thinner sections like on this prop.
“Why are they machining this out of a solid block of aluminum, instead of investing in foundary tooling so they can cast these ?”
That is a very good question... As a fabricator I would guess that it might be due to the fact Forged Billet Aluminum is much stronger and less prone to fatigue. This is why they stopped selling cast aluminum semi truck wheels many years ago, they are now all forged billet and machined. I can just imagine the forces placed on it in this application.
I got the hint they are matching them to the motor, effectively they're custom made with a multi-axis mill. Further, I would expect a cast aluminum prop to be both more brittle and more subject to cycle fatigue. The former would harm efficiency. With such thin cross sections, the latter would be...
These have been around for a few years. Cnc is for stainless steel. They have started using aluminum and casting. The 30% gain is in a narrow band around optimal fuel use. Most other ranges are better than standard props but only slightly. Hard to recover cost on smaller boats, but 30% gain on boats <.5 mpg at over $4.50 gallon may make sense.
Probably prototyping right now. Investment casting molds would be quite tricky with that shape.