Raceboard Design 2
June 16, 2010
Raceboard Design 2 The “Skiffboard” – Conceptual Design
Last year I wrote an article on LBWS regarding Raceboard design. It outlined some design principles that I believe could improve Raceboard performance. Since writing that article, I’ve fleshed out a conceptual design and attempted to gain industry support to bring a new Raceboard concept to market. I’d like to share with LBWS my preliminary conceptual design and the feedback I’ve received from industry.
DESIGN
The overarching design objective is to the build a faster Raceboard: a ‘round-the-buoys’ sailboard conforming to the Raceboard class rules for use in 0 to 25+ knots. It would be used in a wide variety of conditions, typical of sailboat racing venues such as Sydney Harbour, and would need to be able to handle moderate-sized waves, and areas of light wind. It is an all-conditions racing board.
The overall design concept borrows heavily from the 18foot skiff designs (the pre-cursor of the Olympic Class 49er) of the early 1990s, hence the name “Skiffboard”. It has a long, sharp bow with a vertical stem and a wide, flat planning area at the stern. The design merges the bow of a displacement hull (such as the Starboard Serenity or Div 2) with the stern of a planning hull (such as a modern wide-ish slalom board).
>It would be 3.8m long, the maximum permitted length for the Raceboard class, and of a width equivalent to modern Raceboards. The diagram below shows a rough sketch of the concept:
This design as pictured above is preliminary and conceptual – it obviously requires significant refinement. However, I believe that this design concept (if refined) would provide superior all-round performance to any raceboard currently available. This superior performance would be driven by the reduction1 of the “hump” in the drag-speed curve1, as discussed in my previous article on raceboard design.
POTENTIAL PERFORMANCE
In light winds, I believe that its performance would be significantly better than existing Raceboards because of its lower form drag (due to the fine bow) – its performance should be closer to a pure displacement hull than a modern Raceboard. In moderate winds, I believe that the wave-piercing abilities of its bow would continue its out- performance of existing Raceboards – in addition, it should outperform displacement hulls because it would plane earlier.
In strong winds, I believe that its performance would be comparable to the current crop of Raceboards. It would outperform displacement hulls in strong winds because it could plane on its tail like a slalom board.
However, handling may be challenging in stronger winds. I believe it may have a propensity to nose-dive while sailing downwind in chop. This can occur with high performance designs such as skiffs and catamarans. However, I believe that handling techniques may be developed to compensate and its potential all-wind performance would be worth this compromise.
Areas where this board maybe more difficult to handle is in manoeuvring/turning (particularly tacking and bearing away). The long displacement-profile bow may be difficult to ‘push’ laterally through the water. However, I don’t believe this would be any more difficult than the Div 2 boards of the 1980s and, again, handling techniques could be developed to adjust.
DESIGN CONTEXT
All of the above comments about performance are hypotheses, but based on first- principles hydrodynamics and from my experience in developing, racing and observing Moths, 18 foot skiffs and other high performance sailboats. This design concept is unproven2 – it needs further refinement, particularly regarding the alignment of the shape to the key ‘numbers’ (rig & hull forces, weights, volumes, mast and centreboard locations etc), and then development / testing of prototypes.
I am not aware of any other truly comparable boards at the moment, although some designs have touched on this concept. This design concept varies significantly from a Div 2 board (displacement hull) because of the wide, flat planning area at the stern. It also varies significantly from the hybrid boards that were designed as potential Olympic boards because of its 3.8m length.
INDUSTRY SUPPORT
I am not approaching this as a commercial venture: I simply want to sail faster Raceboards and see the Raceboard class develop. To this end, I have contacted several of the leading sailboard manufacturers to try to make this design a reality. I have shared my design concept with them. In addition, I have even offered to co- ordinate further design / development and construction / testing of prototypes (effectively outsourcing their R&D for this board), while allowing them to retain commercialisation rights.
The feedback from the manufacturers has been positive regarding the design concept. However, they have not been interested in developing this board with me, generally stating that the Raceboard / lightwind market is too small and is considered a niche. This response is disappointing but understandable: they are operating a commercial enterprise.
While the big manufacturers may not find it attractive to invest in Raceboards, such investment might suit a niche or boutique sailboard manufacturer. I’m interested to talk to such parties and I would offer to co-ordinate further development if they’re interested.
Alternatively, perhaps an individual will take these design concepts, and build and race a board competitively. Unfortunately, the Raceboard class production rule discourages such innovation.
The Author
Richard Reatti (AKA ‘yagon’) is an avid sailor of Raceboards at Dobroyd Aquatic Club in Sydney, Australia. His sailing background includes extensive racing of skiff Moths and 18 foot skiffs, achieving top 5 placings in their respective world championships and he was the world junior champion in the Moth class. He is also an engineer specialising in fluid dynamics.
Richard can be contacted at: richard @ reatti.com.au
(1) I expect that eliminating the hump in the curve will not be possible for a craft as small as a sailboard, but I believe that this design will reduce the hump significantly.
(2) Unproven in sailboards, however, this design concept has been proven in dinghies such as: Moths, 18 Foot Skiffs, 49ers, 29ers and others.