Mastfoil Ketch Rig? Boat builders ask the tough questions

Hi Ted,

I’d be very interested in your view of the Mastfoil 47 ketch rig: http://www.chriswhitedesigns.com/atlantic_cats/mastfoil/  …and whether it or something based on similar concepts could be an optional rig on the Antares 44i at some point in the future.

Thanks and regards,
PC

Ted Clements:

I am perhaps rather a wet blanket but I think the correct way to approach an engineering problem (radical rig propositions included) is to ask tougher and tougher questions until the answers reveal as many pitfalls as possible, before nature does it for you.

Cool though his proposal may be, C.W. adopts a tone rather reminiscent of an infomercial, which may be appropriate for his intent to find a taker, but I find it kind of off-putting myself. I would rather see a less glib response to the issues and some balance; what’s good and what’s bad. There is always a downside, best consider it up front.

The ‘Mastfoil’ presentation is remarkably devoid of any meaningful engineering details that may give a hint as to how the truly daunting engineering details may be solved with the essential simplicity that sea-going demands. These problems may in fact have brilliant solutions that remain under wraps until the avowed patents are granted but until those details are revealed, we have to use our imaginations.

The theoretical shape and efficiency advantages of a fixed wing style sail over stressed fabric have been recognized for a long time. Making a practical one has been tough to achieve even in racing circles where longevity and cost are unknown entities. The Mastfoil is presumably an attempt to get there or at least part way there and get some performance advantage while addressing some practical concerns. That the performance enhancement is somewhat necessarily compromised with this particular proposition can be assumed by the fact that it is being marketed to the cruising fraternity; if it was race worthy I imagine we would have seen it already.

The ‘60% size’ model test is undefined. Loads expand exponentially with vessel length, mostly cubed. So;’ 60% of what?’ would be the follow-up question to ask. I believe the engineering will probably have been done but without qualification, I would have been reluctant to present a specific and suggestive number to the innocents.

Multi-mast arrangements went by the wayside when mechanical means of handling large sail areas came along and spreading ‘tall’ sail is relatively more effective for a given area so the single mast eventually won out in both the handling and performance categories.

I would speculate that this ketch rig has been necessitated by structural and operational limitations to possible mast height. The structural problems of stepping and staying multiple masts is especially problematic in catamarans and you need a powerful incentive to go there.

There seemed to be a lot of speculation about the possibilities of sailing sideways and backward with this proposed rig. I’ve done some of that myself, using conventional sails, usually unintentionally. Think of the sheer mass of the forum advice sailing backward etc. could generate.

Fabric sails are inherently blessed with a kind of safety valve; even if you can’t lower them, they will eventually shred or can be cut away in extreme circumstances. I think I would be leery of having a large fixed area aloft in a storm that relies on its ability to swing around and thus avoid presenting its worst profile to the wind forces. If something went amiss with the mechanisms or the real wind was perhaps less theoretical than that of a wind tunnel, I can image getting into a stew about staying upright. Is the windage of a single naked mast with spreaders and diamonds more or less hazardous than two Mastfoil equipped masts? Only sea time in awful conditions would suggest a true answer, hence the traditional conservative inclination in vessel design.

Beyond those observations, I dunno. I may look like a backward ass in a few years’ time, if I haven’t already got there.

Will Antares offer such a rig option?

Installing any item on board represents a tacit endorsement to some degree, even if the builder has declared a reluctance to do so. For something as critical as a rig and sail arrangement, there would have to be an extensive track record of success at sea with similar boats, crews, and goals.

We waited for a long time for the bugs to be ironed out of the relatively simplistic in-mast furling main. The anticipated compromises to performance proved to be ameliorated to a large degree by the ease with which the sails are deployed and recovered, enhancing net usage of the main, so perhaps we were too conservative in adopting it on that score, but the engineering, serviceability, and reliability still had to be established over time. Using our owners as crash test dummies with heavy wallets (even if they are willing) is rather anathema to the company’s sensibilities (we all require sleep at night).

If a wing mast/sail arrangement, C.W.’s or some other, should prove out as a cruising boat option, you may indeed see an Antares with such a configuration. Before that happens we will all need more than a computer render and a video of trials using a different category of vessel to persuade us.

At risk of being repetitive; boat design is an exercise of reconciling compromises. If your confidence in a Chris White experiment trumps a myriad of other considerations like; configuration, support, cost reliability, etc., then that is the way your particular compromises may be reconciled.

I think the reality of clever boat stuff may be more entertaining at sites like this one;

or, even more apropos perhaps;

The ‘Mastfoil’ may be the greatest thing since sliced bread! (I never understood that – I still buy bread unsliced; it stays fresh longer.)

TC

Advertisements