I noticed on facebook that there was an entry on wind ranges for the 3 IOM rigs which I thought was worth looking into in more detail. Lots of people put forward their ideas and probably the most truthful was use a rig until you see your rudder and then change down. It is not an easy question to answer as the wind band for changing rigs will vary by a few knots depending on the conditions as I explain below:
Various wind ranges were suggested for each rig. e.g:
A rig 0-15
B rig 15-23
C Rig 23 plus
But when you add in other factors life gets complicated:
Are you on a windward shore in flat water? What are the wind speed away form the shore.
Are you sailing on a lee shore in waves?
Are you on the sea with big waves?
Is it warm? The wind is much softer in the summer when it is warm
Is it cold?
Are you sailing in gusty conditions between rigs where the predominant condition is for the lower rig?
Is the forecast for building wind or fading?
What are the clouds suggesting?
Is your venue surrounded by banks where on the water the wind may be less than the top of the bank?
When you are racing the decision to change is quite easy:
1 Can you tack?
2 Can you sail downwind without doing an impression of a submarine?
If the answer is yes for both stick with the bigger rig.
I have sailed fast in gusts of 25 knots with an A rig
I have sailed fast in 15 knots with a B rig in a short chop
Story from racing at Gosport
To explain how difficult the decision can be to change rigs let me recant the story from last Thursday at Gosport. The forecast was 18 knots gusting 30. The wind on the water for the first four races was 18-20 fading to 10-15 with clear skies so everyone changed to A rig. As we changed rigs a large cloud loomed overhead and as soon as we put our boats on the water the wind blew. One boat broke a jib boom on a wipe out and none of us could make progress downwind, so we all had to change back to B rig and that was the right rig for the rest of day. The moral of this story, watch the clouds.
An anemometer will not be of much use to you on its own even if you spend enough to get one accurate enough to give a precise readout. It will tell you the wind speed but not the overall conditions.
The trick is to arrive at a destination early, study the conditions carefully, consider all the factors above, see what the most experienced sailors are doing and then make you choice and test out the conditions on the water. As a rule, if in doubt go for the bigger rig.
Happy New Year.
Ooops, too much sail