Plan B

International One Metre Racing Yacht



Peter Burford Builder

Plan B – Step by Step Rigging & Set-Up Guide


Champion sailor, Scott Fleming has prepared this guide to help you gain the best from your Plan B yacht.


Every time you rig your Plan B, you should do exactly the same steps in order to develop a consistent approach, quickly achieve relocatable settings and develop a greater understanding of an IOM rig dynamics. 

At the end of the day, loosen off the boom vang, jackstay (if supplied) and down haul to ensure that your main sail is not stored under load, which shall help increase the life of your sail.

Your PLAN B comes supplied to rig up perfectly and ready to race following these steps  - IN ORDER ...

1.  Loosely assemble main, jib, sheets and side stays onto the boat.  Tighten side stays to your normal marker (or lock nut).  Don’t worry too much about even side stay tension just yet.

2.  Backstay Tension should be applied to match the main sail luff curve.  Keep applying backstay tension slowly and smoothly, whilst watching the top seam of the main, until you see this top seam brake its shape ... STOP.  Gently release back stay tension until the top seam shape comes back into shape and stop ... Perfect base setting.  Tighten main downhaul and jackstay to smooth out any wrinkles in the main.

(Picture to come)

Trick Notes:

Light winds – Aim for a slightly straighter mast (result fuller main).

Medium Winds – Match main luff curve exactly.

High Winds – Aim for more mast bend, you can apply some mast ram at this stage to help bring back the top seam shape, allowing for more back stay tension.

3.  Side Stay & Boom Vang Settings sheet out all the way for down wind sail setting.  Hold the boat by its keel (mast pointing toward the ground) and look down the leech of the main sail, sighting a straight line between the end of the boom to the tip of the mast. 

BOOM VANG - Adjust (tighten) your Boom Vang so the top main batten is in line or slightly below your imaginary sighted line b/w end of boom and tip of mast.  Flip your boom over to check that the leech on other gybe matches perfectly with your initial side (highly unlikely) and your new imaginary sighted line. 

Main leech on run.jpg


Trick Notes:

Light and High winds – Aim for the top batten to be approx 20-50mm down from your imaginary line.

Medium Winds - Aim for the top batten to be right on your imaginary line.

The Boom Vangs sole purpose is to set your downwind main twist setting.  Once you have the setting you desire, don’t adjust the Boom Vang again.  (Many use the boom vang to adjust the upwind sail twist – Do Not do this, use the Mast Ram instead)

SIDE STAYS - Adjust Side Stay tension to even out the your mast bend and achieve an even main leech curve on both sides.  Tighten the opposite side stay to the main leech being lower, if the side stay gets too tight loosen the other side. 

(Picture to come)

Trick Notes:

Before tightening the side stay, use a spare finger to press onto the side stay whilst looking down the main leech to get a feel how much tension needs to be added.

After some practise you will be able to flip the sail from side to side quickly adjusting your boom vang and side stay tensions quickly to be even on both sides, with the correct amount of main sail twist for down wind.

It’s a good idea to have lock nuts on the side stays so your base setting is fairly close and easy to replicate quickly each time ... Although this should be checked each time as a half turn on the side stay turn buckle makes a fair difference.

A & B Rigs use the forward side stay deck loops.

C Rig uses the back side stay deck loops.

4.  Mast Ram sheet your sails in for your upwind positions (use your Matrix settings).  Adjust your mast ram to suit the upwind main twist and match your jib twist settings.  This should be the most frequently adjusted setting on your boat on a race day for fine tuning, with ¼ of a turn making a huge difference.

During the day you should adjust your mast ram frequently to suit the current wind conditions for each race and feel of the helm.

Trick Notes:

More Ram = Less Main Twist – Higher pointing / less speed / more weather helm.

Less Ram = More Main Twist – More speed / less pointing / less weather helm.

OK so the Above does look a little daunting ... Once you do this process 5 or 6 times, it will become a habit and easy to remember!


Should you not win your races, there is either another Plan B out there (set-up better than yours) OR you haven’t followed the instructions correctly – Try Again!


Plan B – Rigging Guide Notes

All measurements are taken with the boat fully rigged and tensioned ready to race.

1.  Jib Boom Tension is measured in grams from the jib clew with a small digital scale.  An accurate measurement is very difficult to achieve, however the measurement is taken as soon as the jib boom starts to lift up.  Do this 2-3 times and get a feel for the average.  The jib boom lift tension is a product of mast pre-bend, jib pivot point location, main sail luff curve, backstay, mast ram and side stay tension – in that order.  The Plan B comes designed and supplied to achieve these tensions as shown on the matrix.  Generally we’ve found the more tension the better, so it’s better to be over than under.  Figures shown in the matrix are considered to be a minimum.

Jib boom lift 2.jpg

2.  Mast Rake is measured from the top of the stern deck to the bottom of the top mast band (trailing edge).  The Plan B rake is supplied pre-set, generally a tolerance of 3mm either side is acceptable, given that measuring is also difficult (particularly single handed with a tape measure).  A good idea is to make a stick with measurements marked on it to enable a fast check, however once set, the rake should not change as there are no moving parts to slip.


3.  Heel Angle is a guide to the wind strength, so look at the day prior to setting up and try to decide on an average.  Generally, rig for the lower end of the days conditions, unless the forecast is for the wind to strengthen.

4.  Main Boom to Post is measures from centreline to centreline.  The measurements shown are a guide only, being a good starting point.  Adjusting the main boom further in / out shall affect weather / lee helm, so some fine tuning and helm feel shall be slightly different from boat to boat.  Try these settings first and adjust from there.

Main boom to post.jpg

5  Jib Clew to Mast is measured from the jib clew (or jib boom wire / centreline of the jib boom) to the centreline of the mast.  Given that the Plan B is designed to run fairly high jib boom lift tensions, this measurement is critical to the boats performance and largely affects the jib /main slot, as little as 3mm makes a vast difference.  You’ll find that the Plan B points exceptionally well, running slightly wider jib boom settings helps prevent over pointing and enhances speed. 

Jib slot, clew to mast.jpg

We’ve found that the following to be a good starting point and easily slighted by eye ...

A Rig -  Jib boom straight in line or pointing at the side stay.

B Rig -  Jib boom 2-5mm outside of the side stay.

C Rig -  Jib boom 5-8mm outside of the side stay (rear side stay point).

6.  Main 2nd Seam to Backstay is measured from the middle batten to the backstay with the main boom off the post as per your normal upwind sheeting in position and out of the wind (if possible).  Arguably one of the most critical setting for the boats performance, this is impossible to accurately measure outside in the wind.  So don’t focus too much on the measurement.  The main point to look for ...

Main leech at mid seam to backstay.jpg

When in the breeze and sheeted in (holding and swinging the boat by the keel and looking down the leeches from behind) the main leech should match the jib leech.  If anything the main should have slightly more twist.

The Plan B seems to enjoy slightly more twist than other IOM designs and generally has pointing height to burn, so if in doubt, sail with slightly more twist in the main.  Remember more twist = more speed.

NOTE:  To set / adjust upwind main twist only use the Mast Ram adjustment.  (Don’t alter your backstay or boom vang settings.)

7.  Jib Top Seam to Wire is measured from the top jib seam to the jib boom leech wire, hopefully out of the wind or with the sails not loaded up with breeze. 

Jib leech at top seam to jackstay.jpg

A little easier to measure.  The aim of running higher jib boom lift tensions is for this jib shape / slot to remain fairly constant, allowing for pointing and sheeting position to be more effective achieving greater height and speed in the gusts.

8.  Main & Jib Foot Camber are both measured by gently pushing a ruler against the middle of the sail to the centreline of the boom.

Main chord.jpg


Other Factors for Consideration:

Wind Shifty & Gusty = More Twist and looser side stays

Flat Water = Less Twist and flatter foot camber

Waves = More twist and fuller foot camber

More Wind = Wider Sheeting Angles

Rig settings

Rig settings
"Everyone needs a Plan B"