Feathering Propeller

Author: Tim Good
Boat: Shadowfax (43)

The Seastream in either 34 or 43 versions is a heavyweight boat. Whether you regard it is medium or heavy displacement they are not fast in light airs and so every little bit helps. We have a multipurpose spinnaker on ours which helps but also a feathering propeller.

The boat was initially installed with a fixed prop which would invariable cause the shaft to turn under sail due to the hydraulic gear box rotating regardless once the engine is turned off.  Originally the shaft is locked using a ShaftLok system. This was seized when I bought the boat and redundant now that a feathering prop is installed.

fourbladevariprop

4 Blade Variprop

Shadowfax has a 4 blade Variprop from Germany. You simply leave the engine in gear when you turn it off. There is enough oil pressure to lock the shaft for a couple of seconds, allowing the blades to feather, before the gearbox releases the shaft into a neutral state. This is easily checked by lifting a board in the aft cabin to show the shaft lose but not turning.

http://www.spw-gmbh.de/en/variprop.html

 

Note that service parts in the UK are available from www.bruntons-propellers.com. Services is quite straightforward. You simply push a load of new grease into an M5 hole on the side of the prop until it begins squirting out of the blades. You can do this with the prop still on the shaft. If buying a nipple from them ask for the ‘Autoprop grease nipple’ as opposed to a standard M5 nipple.

Advantages:

    • Better sailing performance
    • No need for the complication of a shaft locking system
    • Improved engine efficiently with a 4 bladed propeller

Disadvantages:

  • Expensive initial outlay
  • Propeller has moving parts = maintenance

Other Suggestions:

Boat: Tournesol
We have benefited from installing a Bruntons Autoprop. I can get the same cruising speed of 6.7 knots at 200 recv less than the fixed prop before which I reconned saved about 50gals over a 3 month trip to Spitzbergen and allows at least a 1/4 knot more speed when sailing. I still use the shaftlok which can be a bit of a fiddle but OK once you sort out the best way to operate it!