Plan B

International One Metre Racing Yacht

SHOWCASING - PLAN B - A HIGH PERFORMANCE IOM RACING YACHT FOR COMPETITIVE RC SAILING

RADIO CONTROLLED 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.

Settings have been established from trials and racing during 2018 and will be updated as more is learnt.

With Scott's tacit approval, I have added to and tempered some of the notes while leaving his matrix untouched.  


 

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. 

Plan B comes with the rigs loose and at the end of the sailing day, you too should loosen off the boom vang, jackstay and down haul to ensure that your main sail is not stored under load.  This will 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 upper 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 break 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.

 Here the backstay has been tightened to curve the upper mast back, removing all shape from the mainsail top seam. Not seen readily in this picture is that the even mainsail shape has 'broken' to a ragged form, particularly above the mainsail upper seam.

Here the backstay has been tightened to curve the upper mast back, removing all shape from the mainsail top seam. Not seen readily in this picture is that the even mainsail shape has 'broken' to a ragged form, particularly above the mainsail upper seam.

 Now the backstay has been eased to allow the mainsail top seam and upper mainsail to regain the desired shape. In this picture, the mast still has some aft curve, removing some fullness from the upper mainsail and increasing the forestay tension which in turn increases the jib boom lift tension at the clew.

Now the backstay has been eased to allow the mainsail top seam and upper mainsail to regain the desired shape. In this picture, the mast still has some aft curve, removing some fullness from the upper mainsail and increasing the forestay tension which in turn increases the jib boom lift tension at the clew.

 Here the backstay has been further eased to give an almost straight mast, bringing the mainsail close to its constructed fuller shape, with the flow positioned further forward than is shown in the previous picture. The forestay tension and jib boom lift tension at the clew are slightly less and suited to lower wind strength.

Here the backstay has been further eased to give an almost straight mast, bringing the mainsail close to its constructed fuller shape, with the flow positioned further forward than is shown in the previous picture. The forestay tension and jib boom lift tension at the clew are slightly less and suited to lower wind strength.

 

Trick Notes:

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

Medium Winds – Match main upper luff curve and apply mast ram to straighten lower mast or induce a very slight S bend.

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. (result greater jib luff tension, greater jib boom lift tension)

Refrain from re-adjusting the back stay  to set the mainsail twist: use the mast ram.

 

3.  Side Stay & Boom Vang Settings: sheet out all the way to the 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 between the 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. 

 When sighted from the clew end of the mainsail boom to the masthead tip, for medium winds, the leech end of the mainsail top seam should be on an imaginary line between these two points.

When sighted from the clew end of the mainsail boom to the masthead tip, for medium winds, the leech end of the mainsail top seam should be on an imaginary line between these two points.

 

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.) 

Plan B is quicker down wind with the main boom eased out to 10mm short of the side stay, rather than all the way.

 

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

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 generally use the forward side stay deck loops.  A & B Rigs can use the rear side stay deck loops when the masts are raked aft to the maximum matrix measurements, or to give greater jib luff tension at the same side stay tension.

The highly raked 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 for fine tuning on a race day, 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!

 

Disclaimer:

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. 

Major settings can be made prior to an event with minor adjustments only needing to be made during the course of the day.  Setting your Plan B to defined measurements, recording these and the results will enable you to repeat your best performance. 

1.  Jib Boom Lift Tension determines at what wind pressure the jib and upper mainsail leeches ease.  It is measured in gm. 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, main sail luff curve, back stay tension, jib pivot point location, side stay tension, and mast ram pressure. – in that order of application.  The Plan B comes designed and supplied to achieve the tensions shown on the matrix.  The back stay tension is determined by the amount of mast pre-bend and main sail luff allowance curve as these two have been made, and when the boat is rigged, these three establish the base jib boom lift tension.  It can be increased and tuned by moving the jib boom pivot to the aft location, increasing the side stay tension and increasing the mast ram.  The tension can be low in very light winds but 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 for medium winds.

Jib boom lift 2.jpg

2. Side Stay Tension is the primary method of adjusting the critical jib boom lift tension, after having chosen the jib boom pivot position.  Greater side stay tension gives greater jib boom lift tension.  It is read in Kg. using a gauge made with pins at 100mm centres and the digital scale hook at 10mm from the pins face line.  Measurements are taken with the boat upright.  A starting guide to achieving the desired A rig, jib boom lift tension is;  very light winds, less than 2 Kg. reading on the side stay gauge, light to moderate winds, 2 to 4 Kg. and heavy winds, greater than 4 Kg.  Note, it's neither this gauge reading nor side stay tension in itself that is most important. (The gauge indicates less than half the actual side stay tension.)  Mainly they are used for an indication and adjustment of jib boom lift tension.

Shroud Tension.jpg

3.  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, but can be adjusted with the small rigging screw.  Generally a tolerance of less rake, up to 5mm longer than the measurements shown in the matrix is acceptable, given that measuring is 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.  When using A rig maximum rake, the rear side stay deck loops and high side stay tension, the spreaders can be raked back 5 degrees for better mid-mast control.

Rake.jpg

4.  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.

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

Main boom to post.jpg

6.  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 sighted 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.

 

7.  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 sheeted-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 use only the Mast Ram adjustment.  (Don’t alter your backstay or boom vang settings.)

 

8.  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.  If the jib clew to mast measurement is set greater, this top seam to wire measurement is set smaller, so as to keep the jib leech to mast measurement consistent.

 

9.  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

Flat Water = Less twist and flatter foot camber

Waves = More twist and fuller foot camber

More Wind = Wider sheeting Angles


Rig settings

Rig settings
A PERFORMANCE IOM DESIGNED AND BUILT IN AUSTRALIA BY PETER BURFORD
"Everyone needs a Plan B"