The Detail

​

If you review several of the videos and articles on tuning an IOM (HERE), there is a consistent process people have adopted which seems to work.

​

Having set up your boat with the mast rake according to the boat plan, enough shroud tension to stop the leeward shroud from hanging loose when beating to windward, enough backstay to straighten the mast and 15 mm of chord depth in the foot of the main  You are then ready to start.  

​

Set the boat up on a run with the main boom just touching the shrouds and hold it in wind that you expect on the course.  Tighten the kicking strap until the leach twists by an inch or so.  Do this on both port and starboard to make sure the mast is centred and straight.  Look to see if you have more twist on one side or the other.  If the mast is straight and the twist is different on each tack then your gooseneck may not be parallel with the mast.

​

Set up the mainsail

 

Set up for close hauled and adjust mainsail twist with the backstay and mast ram.  The goal is to have the top batten parallel to the centreline of the boat and a fair luff shape consistent top to bottom when viewed from behind and leeward.  If you are having problems with the mainsail leach tension between the run and beat, check that you have some packing under the bottom of the gooseneck.  2 layer of deck patch should do it.  This alters the geometry so the kicker tightens as the boom goes out from a beat to a run.  If you have to add a little kicker tension to get the leech right it will not hurt you.

​

Check the mast bend looking down from the top of the mast.  On an A rig there should be a slight S curve with slight reverse bend at the mast ram.  The B rig should have a fair curve as will the C rig but to a lesser extent.  If you followed the instructions in Boat Tuning and Setup and noted the settings, there should be very little to do other than adjust for more wind or less wind.

​

If you are sailing on a pond surrounded by trees, conditions will likely be quite variable.   As a rule I set my boat up for the lightest conditions but enough kicker to control the mainsail leach and hold it firm in puffs to create power and acceleration.  I am also setting the mainsheet post lower than usual so that as the wind increases the boom is pulled down slightly better supporting the leech

 

Adjust the jib

 

Once you are happy with the main, look at the jib.  The sheet setting you will have pre defined but you need to check the leach.  Looking at the boat from behind and to leeward, see that the leech twist is parallel to the mainsail and has a max twist according to you setup numbers.  Adjust the topping lift to match the twist depth specified for your boat.  As the wind increases, tighten the jib luff bowsie slightly to keep the leech from going soft.

​

Run through checklist for all your settings to ensure nothing is out of place.

​

Check the radio settings are all correct as per checklist.  You may need to micro adjust the sheet setting for the conditions.  As a rule, look for close sheeting with the main boom 10mm out on flat water and ease the booms out slightly as the wind and waves increase.  

 

Check rudder movement is OK and finally scan the whole boat to make sure all is OK and add the burgee to the top of the mast.

 

Check bung is inserted and secure and you are ready to launch.

​

Once all is set, you need to consider conditions on the water.  The base settings will give you a good setup but there are fine tweaks to be made.  The fundamentals are, flatter sails with less twist in flat water with deeper sails and more twist in choppy water.  With experience you will develop your own tweaks but always start with the base settings.  Never change anything by more than a couple of mm.  There are extremely fine margins between and outstanding setup and an average one.

​

​

 

Don't take my word for setting up your boat, have a look at some of experts.  HERE.