Look for articles on twisted rudders
Deals with this issue in exactly the same way stators in ducted fans are shaped to conform to the angled air flow from the fan blades - the benefit is improved efficiency and reduce noise and vibration . US Navy had frigates it did this with also.
Electrics are very responsive to efficiency improvements with resultant drop in amp draws giving longer run time or improved performance
However from what I have seen a wholesale rethink of props would achieve far more
Andrew
On 28/06/2012 11:11 AM, Arby bernt wrote:
Hi Anne,I was describing some force transmitted up the tiller, perhaps an oscillation induced by the twin rushes of water off the prop as it spun. I think this is because the prop blades and rudder are not parallel (or prop shaft perpendicular to the rudder, for example) in our Ericson 27 test boat. This allows for a timing discrepancy in the arrival of the pulses of water from the prop blades. The tiller would waddle. It was unnerving. I don't think this would be a problem in a full keel boat, as the rudder axis is usually closer to normal relative to the prop shaft.
Cavitation only occurred under peak output.
The MaxProp is quite a nice piece of engineering, and I'll try a three-blade version when sailing becomes more important then demonstrating an electric drive.
Be Well,Arby
From: amracel <amracel@stuffandjunk.net>
To: electricboats@yahoogroups.com
Sent: Wednesday, June 27, 2012 7:41 PM
Subject: [Electric Boats] Pulsing Action
Arby (or anyone else with a bit of knowledge), can you explain what you meant by '... a pulsing action against the rudder' with your 2-bladed MaxProp. I've had some issue with some sort of vibration. I've taken care of what appeared to be cavitation, but there's still something else going on. I haven't been sure if I'm noticing it because the electric engine is quieter and vibrates less than my diesel did or if something else is going on. So I'm just curious what your experience was since I also have a 2-bladed MaxProp.
Anne Racel
CAL 2-29
4 Degrees
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