The following Article was kindly written for us by Christian Birrell and Stu Bithell “pictured above”
How we approached and won the GP14 Nationals Abersoch 2011.
We are probably not the best people to give specific GP14 tuning advice because neither of us have spent much time sailing a GP14. This meant that when we picked up our brand new Boon boat we had no pre-conceptions on what were the ‘correct’ or ‘fast’ numbers in terms of rake, tensions, pre-bends etc. Therefore, all the setting we used to win the nationals were developed from our own feel for the boat, and by changing setup until we thought the rig looked correct, and they were not based on any existing tuning guides. This was a process of evolution over the week, and the following guide represents our thoughts at the end of the week. Consequently, some of the following guide could well be different to the class norm.
Hull: Epoxy Boon/Ovington
Foils: Boon CNC Epoxy foils
Sails: Goacher laminate
Spars: Selden Cumulus
Static rig setup
Mast foot position: As far aft as legally possible
(2830mm from Transom to aft face of mast).
Rake: 22’0 feet (note that this is specific to Boon boats and accounts for the difference in transom shapes).
Tension: 425lbs (Measured using a Harken digital gauge). This tension was established by applying tension until all the luff sag was removed. In extremely light conditions, ease tension to encourage a small amount of luff sag.
Pre-bend: 30mm (note this was only our static setup, see chocks section).
Chocks are effectively a powering up, or depowering tool. Chocks in front of the mast straighten the rig, creating a deeper, more powerful mainsail shape. Conversely, removing chocks or back-chocking bends the mast, thus flattening the mainsail.
We setup our mast with a base setting of 30mm pre-bend, which effectively gave us more options than those who setup with a straight mast. We used a large chock (15mm) to straighten the rig to around 5mm of pre-bend in any conditions between 6-18knots.
In conditions below 6 knots we removed the chock, which gave us 30mm of pre-bend and thus a flat mainsail and open leech which is desirable in very light winds (back-chocking would be an option if your spreaders were set with less pre-bend). If you are struggling to get the leech of your mainsail to fly open (i.e. the top tell-tale won’t fly) remove the chock in front of the mast which opens the mainsail leech. Similarly in +18 knots, we again removed the chock to flatten the mainsail. As a basic rule, if you are consistently over-powered, remove the chock.
Try to control leech tension by using only mainsheet tension for as long as possible and never use vang until you are over-powered. Vang has the effect of bending the mast, and thus opening the leech with is a negative effect in sub 8 knots. The vang should only be applied once you start easing the mainsheet to keep the boat flat. The more mainsheet you have to ease, the more vang you need to apply. If you reach max vang and the mainsail is still ‘ragging’ pull some Cunningham on.
On a boon boat with a goacher jib, set the jib cars so that the block on the track is just in front of the block which is screwed into the boat (about ¾ of the way back on the track). If you dissect the jib with the jib sheet by following the line of the jib-sheet all the way to the jib luff, it should dissect the jib luff about ¾ of the way up.
Some people adjust the jib cars to control the leech tension of the genoa in varying conditions. We didn’t. Instead, we used sheet tension to control leech tension, which we believed was more than effective enough. The only possible exception to this rule would be in 20+ knots to assist in opening the leech when the boom was a long way off centre-line (speculative, as these were conditions we didn’t experience).
Avoid using the supplied pin to hold your mainsail tack in place. Use a piece of rope to tie the tack around the mast (maximum of 10mm from the aft face of the mast).
Upwind: As soon as you are over-powered it is all too tempting to pinch your way upwind, and depower through steering high. We found that all our speed gains came from depowering the rig more and steering a lower angle which was faster forward. This delivered a much more effective VMG (although it does require a bit more hiking!). Keep an eye on the waves at all time and try and steer around them as much as possible. Look for flat spots in the waves which will allow you to sail a higher angle without sacrificing speed. Due to the shape of a GP14, it is absolutely essential that the boat is sailed completely flat upwind.
Downwind: The helm has to be active in moving his/her body weight around to keep the helm balanced whilst steering around the waves. If you feel like the rudder keeps loading up, it will be because you aren’t being active enough with your body weight in keeping the boat flat. Your aim is to keep the boat pointing downhill at all time. This is achieved by surfing waves for as long as possible. Try to steer in a way which allows you to avoid hitting the back of the wave in front of you. Be as active and versatile as possible with your steering. There are no hard and fast rules, just be inventive!
Our primary aim for every start was to ensure we popped out the gate when we were lifted. If the pathfinder was lifted, we were happy to allow them to sail the lifted tack for us. Once we had popped out the gate, we always looked to maximise our options right up to the windward mark. This basically means staying in the middle of the course and on the long tack unless there were any obvious gain features (e.g. tidal or geographical effects). In Abersoch, the long tack and the middle of the course was often heavily influenced by the strong tide. There were many tide lines in Abersoch which created big differences in tidal effects across the course, and this played a big part in our strategy. Generally, unless you have good reason to do otherwise always sail the lifted tack, and when you see a mean number on the compass sail towards the middle of the course.
A full and comprehensive Tuning Guide for the Boon Boats GP14 will follow shortly.
The guide will be specifically for our new epoxy Boon Boat.