Project Windrigger

by Ian E. Smith, 81 Eric Fenning Drive, Surfbeach, NSW 2536, Australia
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Copyright by the author. All photographs by Ian E. Smith

If you are interested in proa development, the author would like to hear from you

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See also:
Page 2 : Hull form and capsize recovery

Page 3 : Progress to Dec 1997, and Business Plan

Page 4 : Progress to June 1998 (part 1)

Page 5 : Progress to June 1998 (part 2)

Page 6 : Progress to June 1998 (part 3)

Page 7 : Progress to Dec 1998

Page 8 : Progress to June 1999

Page 9 : Progress to April 2000

Page 10 : Progress to July 2001

Page 11 : Progress to January 2002

Page 12 : Progress to April 2002

Page 13 : Progress to March 2003

Page 14 : Progress to Dec 2003

Page 15 : Progress to Dec 2004

Page 16 : Progress to Jan 2005

Page 17 : Progress to June 2005

Page 18 : Progress to October 2005

Page 19 : Progress to December 2006

Page 20 : Progress to August 2007

Page 21 : Progress to October 2007

Page 22 : Progress to April 2008

Page 23 : Progress to April 2009

Page 24 : Progress to October 2009

Page 25 : Progress to June 2010

Page 26 : Progress to April 2012

Discussion : answers to correspondants

For some years, Ian Smith has been working on a development project, hoping to establish design rules for Micronesian proas. This project needs more participants and more funding. Many topics would make suitable student projects - watch this space for details.

In the mean time, here is Ian's progress to date (self-funded so far):

The first (out of a planned 7) prototype was built in 1992 - a 5.6 m proa named "Windrigger". Sailing trials were carried out in Canberra to proof of concept stage to demonstrate the potential of the proa. "Windrigger" has a balanced sailboard rig, twin reverable spade rudders providing the required lateral resistance, a simple capsize recovery arrangement and functional trailering configuration.

The following photos are of the trials of Windrigger MK I.

Its hull is 5.6M loa, outrigger 3.7M loa, both dory-shape and constructed from 4.5mm plywood, powered by sailboard sails ranging in area from 5 sq m; to 7 sq m, rigged on an unstayed sailboard mast modified to be supported by the hull Laser-fashion.

The rig is free to rotate 360 degrees (which makes it easy to ride out the winds of a thunderstorm). The balanced sailrig does not require a mainsheet, it is a module that can be lifted out of one location in the hull and shifted to another - great for experimentation.

Is anyone is interested in building and using this proa for their experiments?

I first sailed this proa during late 1992, without rudder and centreboard, steering by shifting myself fore and aft about 300mm. I sailed it as a non-reversible proa - that is, outrigger to windward on one tack (Pacific proa) and outrigger to leeward on the other tack (Atlantic proa). I never detected a difference in sailing performance between these modes - which was contrary to my expectation that outrigger drag would be greater in the Atlantic mode.

I could not sail in straight line with the wind dead-astern, it always turned to windward - I guess because the C of E (centre of effort) acts outboard to leeward producing a force couple acting to turn the proa to windward. It was possible to sail in a straight line using steering oar to counter this turn.

This problem was solved using the balanced sailrig shown in Photo 2. This rig maintains the C of E acting along the fore and aft centre-line of the hull for all points of sailing thus eliminating the force couple and drag created by the steering oar.

A shortcomming of this rig was poor windward performance. My explanation for this - a conventional sailboat leans to leeward producing a large force couple which is countered by its hull turning and maintaining a slight skew to windward, developing a hydrodynamic couple equal and opposite to the wind force couple and lateral resistance to oppose leeway.

In the case of my proa with the balanced rig, due to the lack of the force couple the hull does not adopt the skew (known as angle of attack) and cosequently does not produce the lateral resistance required to oppose leeway. Is my explanation correct?

I eventually overcame this by using twin spade rudders and operating in the following manner. When sailing to windward the bow rudder was set with a positive angle of attack ( turning the proa to windward) so that the stern rudder required a positive angle of attack to maintain heading.

Collectively these rudders appear to produce sufficient lateral resistance to counter leeway. My biggest problem I experienced in trialling various sailrigs was determining windward performance and particularly hull angle of attack. My literature search shows that no one including Bruce, Morss, Bethwate, Chapman and Norwood, have solved this problem. Instead of trying to measure angle of attack, I plan to measure hydrodynamic pressure differential generated by hull and centreboard when sailing to windward, using pressure transducers. Does anyone known of such an investigation or existing equipment?

This illustrates the basic rationale of the Windrigger capsize recovery system. In the capsize positon, the outrigger is rotated to a position where it overhangs the hull thus providing a force couple to cause the proa to roll over to the upright attitude. The bridgedeck on the outrigger side of the hull contains buoyancy to prevent it rolling the other way. More about this later.

My thoughts on self-righting - wind and waves beam onto to the proa in the attitude shown in the photo, maybe sufficient to roll it over into the upright position. Also it maybe possible to simply unlock the outrigger so it free to move to the positon shown in the photo and leave to the sea and wind to right it. Could be a good model simulation project.)

This shows the outrigger nesting above the hull in a trailering configuration. Launching is achieved by first rotating the outrigger outwards and fastening it to the bridgedeck followed by sliding it off the trailer and into the water. Its a one-person operation.

In late 1994, the proa was converted into a catamaran, now named "Windriggercat". It has LOA 5.6m, Beam 3.8m (sailing), 2.4m (folded), weight 200 kg, with a biplane rig of two 7 sq m sailboard sails. It is now a daysailer which carries four in comfort and safety.

Windrigger has been publicised in:

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