archive 2

Comments submitted between 18th November 2000 and

Ten people completed the questionnaire during this time. All were male with ages ranging from 18 to 59 years (mean age 37). Two classified themselves as beginners, four as intermediate, and four as expert sailors.

Comments about existing sailing rigs

"Windsurfing rigs - Lots of fun. Getting better all the time with weight reductions and a 'smoother' feel due to better designs (plan form, flexibility, etc). They look good too but there's no doubt about the fact that they are far to expensive. Also the happiness of manufacturers to satisfy whims, rather than design faster sails, is holding the sport back. Not my words, but those of Ken Black (Tushingham sails and formerly North)."

"I have a number of boats. The easiest to use is a gaff sloop because it is so easy to hoist and lower the main, although reefing is exciting and windward performance is not brilliant. The hardest to use is a fully battened high aspect Mylar sail on a catamaran, because it is difficult to hoist, and has no reefing, but I don't mind because it works very well. On our most recent 6m cat, also hi-aspect Mylar, we have slab reefing which increases the range of true wind speed we can operate in but the mast, being aluminium, is very heavy at 21kg. I would like a carbon mast to make rigging the boat easier. I am completing the write-up of a thesis on Chinese fully battened lug sails ("Junk" sails), and have some experience of them too. Done well, they offer a number of advantages for long distance/short handed cruising. Done badly they are a nightmare!"

"Not brilliant."

"Laser - so crap materials -expensive - but they look all right I suppose!"

"Too heavy, too complicated to raise (mast), sails OK"

"Heavy, brings too much forces in the boat, aerodynamics could be better."

"Could be improved."

"Takes 15 to 30 minuets to set up. Hard to rig when winds are high. Difficult to transport long mast."

"Too conventional, too expensive."

What do you think of the Transition Rig idea?

"I'm studying at Oxford for a PhD in the biomechanics of animal flight. I carry out wind tunnel experiments to visualise the flow around insect wings by looking at the deflection of smoke as it passes over their cambered surfaces. The concept that we can design BETTER aerofoils than insect wings, the smallest, smartest aerofoils is a little arrogant - they've been evolving for 250million years! BUT we can learn a lot. Why engineers have not turned to biomimetics (copying nature to solve engineering problems) before is a mystery. After all, we want high lift structures, ideally a thin membrane supported by lightweight battens that deform passively according to external forces. The asymmetric twisting and necessary alterations in camber are modelled perfectly for us in nature. So to answer the question, yes, I like the idea."

I believe many engineers and architects have taken inspiration from Nature in the past, and no doubt will continue to do so. However, I think understanding is essential - copying in the absence of understanding may not be effective. Good luck with your research - we shall look forward to hearing about your findings!

"Interesting. I would like to make some comments - I hope they don't sound too negative, but they will need to be addressed.

1. The Market

From your replies to some of the comments already posted it sounds as though you're not yet aiming at the racing market. It seems to me to be an (unfortunate?) fact that sailing boat development is driven by racing, with innovations trickling down to the cruising sailor. Since the transition rig looks as though it contains some sophisticated engineering (e.g. highly loaded carbon joint components), it is likely to be expensive. This would not be a problem for racing but for, for example a sailing canoe for pottering/exploring lakes and rivers (where I think it would be great), cost and complexity may be a problem. If I could build a small, 6 sq m Transition rig from bamboo and plastic tarpaulin for a canoe that I could repair myself, I would be greatly encouraged. I suspect the market for non-racing, expensive small sails to be very limited. Demonstration of a performance advantage in an appropriate development class (Redwing? Moth?) would, in my view, be the best way to go.

2. The Concept

is definitely worth pursuing. As some of your correspondents have indicated, there is a need from the high performance/skiff sailors for a rig with greater tolerance to wind fluctuations than currently available. A sail that can give a limited upper heeling moment by lowering C of E yet increase the forward component of sail force in gusts is a goal that has so far only been met by variations in sail twist (and reefing, of course!). The Transition Rig may take these ideas forward."

Your comment about performance as a driving force in rig evolution is an important and valid one. We shall need to pay attention to this factor while developing the transition rig. However, our market research has shown that the other qualities of the rig such as adaptability in use and foldability are also of interest, particularly to less competitive sailors.

We are looking into the possibility of making simplified versions of the transition rig for smaller-scale applications such as sailing canoes and kayaks. It would be pleasing to be able to do this using readily-available materials of the kinds you have mentioned in order to keep costs down.

"Been needed for teaching sailing since forever."

"A bit weird - I'm not sure how well the windsurfer type boom thing would work on a dinghy."

Whichever boom arrangement is used on the dinghy version, it has to be able to support the trailing edge of the sail away from the mast, and also allow the rig to fold when required. The wishbone-boom currently used works well, but we shall probably experiment with other types of boom to see if there is a better option.

"If it works, it will be the best concept, I have ever seen. I have seen it somewhere else :-) (eg. birds), but learning from mother nature is the best way to learn: great!"

Yes, all credit to the birds and bats ...

"Looks interesting. Will it look so nice after sailing a season North Sea coastal cruising?"

"Interesting."

"I like it, but have some performance reservations."

"Mechanics?"

"I think it is a great idea. I'd like to see you consider also incorporating controllable mast bending (cupping) perpendicular to the planform, to enable active control of spanwise twist distribution, camber, sail tension, and aeroelastic number. This goes a long way toward overcoming some of the problems associated with 'stretchy' membranes, and allows the 'stretchy' sail to perform pretty well over a much broader range of speeds and loadings, although I wouldn't speculate that it could perform as well as an inextensible sail under perfect, invariant conditions. I work with the biomechanics of a couple of large, late-Cretaceous pterodactyls which used a somewhat similar wing with a visco-elastic membrane and short, intercalated reinforcing fibers. They were marvels of efficiency. Quetzalcoatlus northropi (the larger of the two) had a primary wing area of about 7.3 square meters with intercalated aktinofibrils in the outer wing that could redistribute some local membrane compression loads, allowing the membrane to fly at a reduced aeroelastic number before initiating wrinkling or fluttering. The fibers also worked to allow active control of aft camber."

The two parallel struts that form the middle segment of the transition mast are able to rotate in relation to each other, in a similar way to the movements of the radius and ulna of the forearm when we pronate and supinate our hand. This rotation has a profound effect on the overall geometry of the mast, enabling a shift of the 'cupping' effect that you describe from one side to the other when tacking.

I am quite envious of the ability of Q. northropi to actively redistribute tensions within the wing membrane and reduce wrinkling when the geometry changed. Modern-day bats have a similar ability. I understand that active synthetic membranes are being developed, but I have not yet been able to try them.

Would you buy a Transition Rig?

(Two respondents simply said "yes".)

"That depends on the performance and price. Do the joints and elastic sail cloth add a lot to the weight?"

The transition mast is more complicated than a conventional mast, so a weight penalty is probable. That will have to be minimised by careful design and choice of materials. It should be possible to identify an elastic sail cloth that is no heavier than conventional non-stretch sail materials.

"Not yet."

"No I'm a student I avoid buying things at all costs!"

"I have to read all the infos first, but in general: why not?"

"Wait and see what brings the real sailing days."

"Yes, but I want to try it first."

"If it works."

"If I were a windsurfer I would."