Anyone Seen or Used Sharrow Propellers?

[MACflyer]

Anyone here used or heard anything about Sharrow propellers? Saw first one yesterday: very different. Advertised improvements are amazing but pretty pricey propeller.

https://www.sharrowmarine.com/

[oldmanjoe]

 Can not say that I would use one yet .  Very mixed claims on the real performance .   Not like a bladed prop were you can play with cupping and trim blades .

[jurelometer]

Been reading about them.  This type of prop was actually invented a longgg time ago.  But manufacturing a torroidal boat propeller was far too expensive until recently.  Sharrow uses 3D printing (they use the sexier sounding term of "additive manufacturing") for the casting process, originally by printing the master for a "lost wax" style sand casting, and later with Ford's help, switching to printing the sand mold itself(sand mixed with a resin binder). 

I find this funny, as I went through a similar progression using a hobby 3D printer designing casting molds for lures and other small parts, first designing a master of the final part for the mold, and later designing a mold for the mold itself without needing any part master.  You would think that these guys would be smarter than me and skip the first step

They probably need some fancy 4 or 5 axis CNC machining for the finish work after the casting.  This more expensive manufacturing method combined a lack of competition is probably why they are so crazy-expensive.

Why the manufacturing method matters:  The complex manufacturing requirements means that these are also probably going to be difficult props to repair.  I don't know how much more sensitive the design is to getting dinged, how much a ding is going to affect performance, and what are the repair options(how bad is repairable, and where can they get repaired, if at all),  but these are questions that I would ask.  They have a prop  insurance program, but it looked pretty expensive, and there still is a problem if you lose time on the  water due to more frequent or slower repair/replacement.

Money wise:  The claim is that these props provide a moderate improvement in mid-rpm performance, and with enough miles in the ideal RPM range, the props will eventually pay for themselves.  So they have to last long enough to get your ROI.  Plus if you can't mix and match, when you smack something with one of a pair, your backup has to be a Sharrow as well (worse if you have counter-rotating or more than two motors), or you have to switch both out to standard props. If you prefer to carry backup props, the switch to Sharrow could get really expensive or at least more complicated.

-J

[MACflyer]

Why the manufacturing method matters:  The complex manufacturing requirements means that these are also probably going to be difficult props to repair.  I don't know how much more sensitive the design is to getting dinged, how much a ding is going to affect performance, and what are the repair options(how bad is repairable, and where can they get repaired, if at all),  but these are questions that I would ask.  They have a prop  insurance program, but it looked pretty expensive, and there still is a problem if you lose time on the  water due to more frequent or slower repair/replacement.

Money wise:  The claim is that these props provide a moderate improvement in mid-rpm performance, and with enough miles in the ideal RPM range, the props will eventually pay for themselves.  So they have to last long enough to get your ROI.  Plus if you can't mix and match, when you smack something with one of a pair, your backup has to be a Sharrow as well (worse if you have counter-rotating or more than two motors), or you have to switch both out to standard props. If you prefer to carry backup props, the switch to Sharrow could get really expensive or at least more complicated.

-J

You bring up some very valid points Dave. Appreciate your time and input.

[boon]

The measured performance gains are pretty crazy. But so is the price. If I owned a large single screw launch that would never see less than 30ft of water under its keel I'd consider it.