8 up to 11 to 1
by John Curnow, Global Editor, SailWorldCruising.com 12 Oct 15:00 UTC
Commissioning and sea trials are underway on 68.06 © Gunboat
Now you cannot have that discussion without first having one about displacement. In fact, they really do need to be run concurrently, but so as not to get fixated on the latter, let's sort of let it coast along on cruise control for a bit so that we get stuck into the former. Whilst we are at it, we also need to remember that volume is also part of the mix, but it too is not what we need to put the laser pointer on, right now...
So 8 to 11:1 is a ratio that is so utterly crucial to cats. Length to beam, as it turns out, and in between those two is fairly hallowed ground. At 8 you are a motorsailer, at least with the leeward donk anyway. After 10.5 you are flying a hull, you'll be made of carbon, and your gear bag will be weighed when you get on. Actually, leave the bag dockside, and step on with that which you can only wear or carry in your arms.
After 12 and a pipe cot will look glamorous. Yes. There are a few caveats to all of that, and I'd hate to be using humour for humour's sake... Now in theory anything can be done, but large chainplates in titanium for a cruising cat and E6 standing rigging is just a little bit overboard, wouldn't you say?
So at 8 or so you have seriously millions of choices. And it is fair to say that the more you go past 12 (and take into account the other two big ones) the more you'll look like an F50. Cure Marine's glorious Cure 55 is one that sits at the upper end of this narrow and somewhat exclusive band.
Here there is a trade off in outright volume for less wetted surface area, lower mass, and wait for the big one, a significantly greater 24 hour run distance over the porky pigs. You could be up to 150nm in front in just the one day, which means you will have left that anchorage and be setting up camp in the next one by the time the other boat is just arriving at the one you left before. You're nowhere near done with sailing if you go down this path!
So what about the other end of that wee niche. Where you trade off a bit of outright pace for more volume. The ability to have a head amidships, and not at one end of a narrow cul de sac. Perhaps even a King bed instead of a Queen. One where you can and do still sail it, as well as turn the smelly off in just about all conditions. Yes. Not many production level boats reside in that place.
This was a locale that Excess arrived to lay claim to, and indeed the later Excess 11 and now Excess 14 (which are effectively Excess 1.5 and 2.0 respectively) have delivered upon. In the case of the Excess 14 especially, the work done under Covid rules has paid off. Time to run various designs through CFD modelling has resulted in asymmetric forms and shorter, but deeper keelsons, amongst other things.
To say I have enjoyed my time speaking with The Catman Group Beneteau's Bruno Belmont over our Sail-World journey really is the classic understatement. Notwithstanding any of that, Excess Brand Director, Thibaut de Montvalon, sat down to get the low down on cat design with Bruno, which you can watch just below...
As a completely self-confessed nerd and trainspotter, it was refreshing to see and hear just how far they were prepared to go in explaining the ins and outs of what's in and what's out when it comes to delivering on a very special promise - that sailable cruising cat.
The reason is simply that these are points every buyer should know and be aware of, for it is going to maximise your dollar and more importantly, your overall experience. Not everyone wants to fly a hull, and not everyone wants to grade every piece of ocean they cover. Where you land on the spectrum is going to be best served by one style of vessel over another, and selecting said craft is THE only thing you need to be concerned with.
Below is a list of the subjects they go into and explain. Do not worry if you do not comprehend a section at first, just watch that portion again. For instance, don't get locked in on the formula for prismatic coefficient, just think of it as a representation of how big a hole a certain hull form makes as it moves along. If you want to read more about, please read this America's Cup article.
- Hull form
- Displacement as it pertains to beam
- Outright displacement itself, and how to assess it
- Centre of Gravity and keeping it in the same position
- Beam as it relates to room and stability, against cost and mass
- Beam as it relates to wetted surface area, hull form, and specifically the beam at waterline (BWL)
- Platform length (i.e. internal space on the main deck) versus hull length, and therefore also mass
- Appendages - especially drag versus lift (performance), including asymmetric hull shape
- Volume spread as it relates to seakeeping and pace
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Finally, stay safe, and let's see where it all goes now,
John Curnow
Global Editor, SailWorldCruising.com