Geoff Moore on the IC and Balance
The frostbite season is now officially over, at least here in New England. My last event for the season was the Interclub Nationals in Hyannis, MA out on Cape Cod. Sixty boats competed up. The racing was very tight, and the “streaky” North East wind made for some very difficult conditions. Neil Fowler from Portsmouth RI won the event, my new wife, Gillian, and I finished fifth.
Learning how other fleets overcome obstacles is a great way to expand your arsenal of sailing tools. So I thought you might be interested in a few things about these funny little bathtubs. ICs were first commissioned by Corny Shields in 1946. They were originally built of wood, many of which are still very competitive, but the newer Fiberglass boats give their owners a little more confidence in tight mark roundings (you only have to fix a wood boat a few times before you get a little squeamish about tight places). IC’s were intended to be owned by many of the yacht clubs around Long Island Sound so that members would not have to bring their own boat in order to compete. Hence the name “Interclub”. Nowadays they are used in institutions and as frostbiting boats.
The IC is cat rigged and the mast is only about a foot or two from the bow. The first thing you notice when you start playing with these little tubs is that it pays to tilt the centerboard about seven degrees forward from vertical. This is simply because the boat maintains better balance with the Centerboard farther forward than the original centerboard trunk was designed for. I mention this because it is just another example of how important balance is to the overall picture. It is the same reason we fair a J/24 keel to its max forward position, and it is the same reason we tweak the headstay lengths on most competitive race boats.
The simple truth is that the boat would work better if there were not a class rule that limited the position of the Centerboard trunk and the pivot pin. A vertical board would extend deeper and therefore generate more lift, but it is faster to put the lateral resistance forward and therefore closer the correct position. If the board is not tipped far enough forward then the sensation on the rudder is obvious. There just is not enough helm. In windy conditions the front of the sail has to be feathered, so naturally the force on the one and only mainsail shifts aft, towards the leech. This in turn drastically increases the pressure on the rudder, sometimes to the point where the rudder stalls. So in heavy air it pays to tip the centerboard aft until the balance is just right.
The simplicity of this concept is lost by the majority of the IC fleet, many of which are exceptional sailors. You should hear the quasi technical mumbo jumbo in the parking lot about why the Centerboard’s forward angle improves performance. But I like listening to all the “new” theories about how fluids “behave”, and how vortexes are “generated”. It gives us something to do when the wind is too strong or too light. Sailors like to make things more complicated than they really are. There may be some weird science going on when you rake a mast back or slant you keel forward, but every eight year old in sailing school can tell you about balance and the forces of Center of effort (CE) and of Lateral Resistance(LR).
“Just pull the centerboard lever all the way back until it stops and just go race. You don’t have to know why, you just have to put it there.”
Interclub Dinghy Class 