Seahorse International Sailing
November 2001
When the concept (and the word) "Maxi"
was first coined in the IOR era it served as a hard guideline for anyone wanting
to race at the fastest and biggest end of the sport. Go anywhere in the world
and the word had the same meaning and application : glamour. When IMS took
over from IOR there was a temporary unwillingness on the part of the rule
makers to lock in an upper limit but this eventually evolved in the mid-90s
in the guise of the ILC 70. Unfortunately the ILC 70s never enjoyed the owner
support that the IOR maxis did despite being all around better boats and the
concept languished. Yachting, like nature, abhors a vacuum and into this flowed
a range of concepts that made the maxi concept look a bit staid. From the
Volvo and Open Class 60s to 130 foot catamarans it became hard to view the
ORC mandated maxi as the be all and in all they once were.
Stability and more importantly the limit of positive stability (LPS) raises
it head here once again. It has been a much debated issue in the IMS era but
more from the point of view of those that want to go but can't due to a low
LPS. I don't know of anyone who has bothered to read or understand the development
of these stability limits which are documented under the heading Final Report
of the Directors - Joint Committee on Safety From Capsizing, June 1985. The
joint committee was the United States Yacht Racing Union and The Society of
Naval Architects and Marine Engineers. The document is the result of testing
and documentation to determine the mechanisms of yacht capsize and forms the
basis of the IMS restrictions in this area. As well it is used in other areas
such as the Whitbread/Volvo Race where the stability limit is 125 degrees
or 10 degrees higher than for the Hobart. The prescribed amounts would mean
that, in still water, the boat would obviously remain stable upside down.
Where the values are made reasonable is in the consideration of the sea state
that would actually cause a capsize. This same sea state, combined with an
adequate LPS, will see the boat re-right itself in a reasonable amount of
time. In the case of the 115 degree limit this is estimated to be around 3
minutes of inversion. Actual documentation from this last Hobart suggest that
these values are not far off the mark though exact correlation should never
be expected. It should also be noted that your certificate has a partner value
for the LPS called the Stability Index. This was initiated to expand the LPS
concept to include the probability of certain types of boats being more prone
to capsize in spite of meeting the LPS requirement. Small, beamy and light
are considered more prone that long, skinny and heavy. Despite ORC recommendations
on this matter it has been largely dismissed probably because it keeps smaller
boats out of Cat 1 races. It would be interesting to re-visit this matter
in light of the new data derived from the Hobart.
This issue was academic to some but to races like the Sydney to Hobart it was critical. This is a race that thrives in the public (and therefore the sponsor's eye) on line honours and race records. The fundamental still birth of the ILC 70 class left the front of the race looking predictable with boats like Brindabella enjoying an unprecedented seven years in the lime light. As a result the CYCA took a major decision to break away from the ORC recommended and internationally accepted upper limit and create their own. Their uncertain plunge forward created a dual limit of IMS /ILC 470 sec/mile and IRC TCC of 1.6. Some advice had suggested that there was parity in these two numbers and also that it was not a set of numbers that would outright obsolete the ILC 70s already on the water. The decision seemed right all the more so because the organisers of the Newport to Bermuda Race and the International Class A Yachting Association both readily adopted the 470 (but no the IRC) limit for their own events. As some of the hopped up maxis were already near that point it hardly seemed a big step forward.
What IRC 1.6 meant remained to be seen. For the 2000 running of the Sydney to Hobart it seemed we had an answer in the form of Nicorette and Wild Thing both of whom had undergone significant modification, including water ballast, to reach the 1.6 TCC. Nicorette took line honours and it would seem that the baton had been smoothly passed and the future was well and truly with us. Or was it?
As the smoke of the finishing gun cleared a significant interest developed among a group of owners to join the fray and build new 1.6 TCC designs. We were commissioned by the owner of our evergreen IMS maxi Brindabella to explore what the upper limit really meant. The answer was outside everyone's expectations. The results follow in bullet form:
Water ballast? Definitely not as it is too harshly penalised for a single point handicap system. Far better to take your rating in areas (like working sail area) that are used in a more balanced way across the course. Remember, however, that we are designing for the Sydney to Hobart course which is essentially windward/leeward with small reaching component.
IMS rating equivalent? For the 1.6 design we produced the ILC weighed average is 437 sec/mile. This means the IRC design is 33 sec/mile faster than the new IMS limit of 470. That is almost 6 hours difference to Hobart! Shockwave, a non-water ballasted design which was leading last years Hobart before retiring had an ILC average of 454.6 so even she will be over 3 hours off the pace. This is new territory.
IMS legal? It can be with no real penalty. Not sure why this matters but it is worth keeping in mind if the IRC rule minders ever tire of the level rating game or you want to race in US waters.
Size? Numbers as follows:
LOA: 27.2m (89'
3'')
DISPLACEMENT: 21,800kg
RMC: 1520kg.m
Sail Area:
MAIN: 206.5m^2
MH SPIN: 667m^2
100% JIB: 167m^2
Performance: Using WinVPP on the proposed design gives the following values at 14 knots TWS:
UPWIND Vs: 10.39 knots
UPWIND Vmg: 8.34 knots
DOWNWIND Vs: 13.6 knots
DOWNWIND Vmg: 11.71 knots
It is obvious that an IRC 1.6 maxi is bigger and faster than anyone imagined. A lot more dollars to build, a lot more to run while at the same time creating obsolescence in the rest of the mainstream monohull fleet. The question is, what is the foundation for all this? After all, the main reason rules exist is to provide stability and a certain level playing field. Where is the rule here? Two points to consider:
Firstly, IRC has no upper limit. The de-facto limit is set by RORC for their own season and it stands as a simple LOA value with a maximum size of 100 foot for the major events such as the Fastnet Race and 85 foot for the minor events. No speed limit is implied. As a result, a 1.6 limit boat could happily race in IRC events though it seems that anyone really keen on speed would go the extra 10 foot with no rating limit.
Secondly is the fact that the IRC, which is jointly managed by RORC and UNCL, does not support the idea of a level rating grand prix concept under the IRC umbrella. They have the IRM rule for that. Also, IRC is a secret, designer proof rule whereas the level rating game requires lots of rule probing and manipulating to get the ideal balance of factors in place to equal the magic maxi limit. IRC won't allow this to occur since this type of probing leads to rule cracking. As a result the IRC put forward an edict last February limiting the number of trial and designer trial certificates that can be run by any one office or on any one vessel. The number is low and it makes the designer's job difficult and the results suspect. In effect, we are being warned that the tolerance level is low and that the rule choice is wrong even if it is the choice of the marketplace. This is slippery ground.
All that being said the concept seems to have wings. One design is already under construction in Sydney (on the water next June) and several proposals are still floating about. There will be teething issues, no doubt, but the concept seems to be supported by Australian owners in a way that ILC 70 was not. If all goes forward and a fleet develops then it falls back to the rule makers to accommodate what the market wants.
END
Scott Jutson
Jutson Yacht Design