By Jesper Bank · BDA Magazine 2006 Annual, p. 25
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A 1998 letter from Jesper Bank to Patrick Gifford setting out his simple, feel-based approach to Dragon rig tuning. He sails with the rig loose – virtually no tension on the lowers and the leeward upper only just loose in 8 knots – keeping the mast straight sideways up to 14 knots and tightening the lowers so the top falls about 8 cm to leeward by 25 knots. There is no runner tension below 6-7 knots (headstay tension comes from the mainsheet), 4-6 cm of forestay sag with three on the rail, genoa halyard set by twist and telltales, and stiff jumpers reading 25 on the gauge 50 cm from the turnbuckle for 1 cm of forward bend with no sail up.
In 1998 when Jesper Bank had just won the Worlds and come second in the Europeans, Patrick Gifford was finding his main and genoa difficult to set up. After an exchange of faxes with Jesper, back came a clear, non-technical tuning guide, which is reproduced here …
Dear Patrick,
I have the exact opposite feeling about the sails than you have. As you have noticed, we sail with everything quite loose. Virtually no tension on the lowers, and the uppers so loose that the leeward shroud is loose (only just) in eight knots upwind sailing.
Looking up the mast it is straight sideways in winds up to 14 knots. As the wind increases, you tighten up the lowers until the top goes to leeward by approximately 8 cm. This setting should be reached in 25 knots. Between 14 and 25 knots you apply the tension on the lowers that gives you the best feeling on the helm.
This is not as scientific as could be, but use it as a guide and try it. Forget what you are doing today. Look at the tension on the upper shrouds and on the lowers, get the feeling right. Then measure the tension. Not before.
You have most observations right (I had set out what we thought, from observation, he was doing). We do not use any runner tension in winds up to 6-7 knots. The appropriate headstay tension is coming from the mainsheet. This means that when you have set your main right, your headstay sag is also right. How can it possibly be any simpler?
The tension on the luff of the genoa is decided by the twist of the sail. Apply halyard tension until the telltales fly the same. If for some reason you want the top of the sail more powerful and less twisted, apply more and more tension.
As the wind increases, runner tension is needed. As a guideline: have 4-6 cm of forestay sag with three people on the rail.
To make all this work you need a good stiff top (Jesper used fixed jumpers). When we measure the tension on our jumpers 50 cm from the turnbuckle, our gauge shows 25. That tension gives you a 1 cm forward bend when there is no sail up. When sailing in 10 knots you will see a 1-2 cm aft bend over the whole length of the mast.
This is a different approach to tuning, but I think a much more fun way, which leaves the fine tune open to each individual’s style of sailing.
When you use the sails like this you will never feel underpowered or oversheeted.
In your basic set-up the most important factor is mast bend. Get that right and then try my way. I know you will feel the difference.
Originally published as “Jesper Bank’s non-Technical Tuning Guide” in the BDA Magazine 2006 Annual. © Jesper Bank, Patrick Gifford and the British Dragon Association. Reproduced with permission.
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