Nationals Preparation Tips Part 3

Straight line speed.
Once you've taken care of the basics that we reviewed earlier, involving preparation of the hull, centreboard and rudder, and mast and rig tuning, boat speed is then about sail trim, boat trim, adjustment of those two, and steering.

Sail trim.

Whether your sails are old or new, you will still benefit by trimming them correctly. Generally new sails will perform better than old because in new sails, the shape will be where the sailmaker has designed it to be as well as being more stable in it's position. In old sails, the shape generally moves towards the aft edge, which is generally a slower, draggier shape, especially in the jib, but can sometimes aid pointing ability in the mainsail.

Mainsail.

On the mainsail, I use just one set of telltales at about the top ¾  height position, wool in the middle along with a leech telltale at the same height. I only need to look at these and don't need to bother looking at anything else.
On the jib, just a pair of upper and lower tufts, and one upper leech ribbon. The lower tufts for steering and the upper for sheet tension.

Going upwind, we have the boom sheeted onto the centreline until the point where we need to ease the boom out to stop us from heeling over.

Until then, I am concentrating on sheeting the top of the mainsail so that I have the windward tuft flowing and the leech telltale flowing about 50% of the time.

Beware, you need to be steering at your optimal angle to the wind while you are trimming the top of the mainsail.
If the windward telltale is not flowing straight aft, you are giving away power.
If the leech telltale is flowing all the time, you are probably giving away some pointing ability. You want that leech telltale to be flicking behind the sail some of the time.
However, if you are in a situation where you don't need to point so much as go fast, you can ease that little bit and have the leech telltale always flowing.
It's not easy to get a consistent flow of each telltale. You often just have to get a good average of the two ideals, especially if there are waves about.
So, this trimming is usually achieved just with the mainsheet. The sheet should pull the boom to the centreline and then start pulling down on the leech until you achieve the correct trim for the top of the sail.
The you want to hold that tension steady until the wind changes strength. It's easy to slack off the tension a bit, so be vigilant that your mainsheet tension is consistent.
On boats with end boom sheeting, you should firm up the  boom vang to help hold the leech tension in case the mainsheet tension comes off a bit.

Now every time that the wind changes strength significantly, you likely will need to adjust the leech tension, easing off in a lull and increasing tension in a gust.
I gauge a significant change in wind strength as when we need to move ourselves inboard or outboard to keep the boat sailing flat. Have to move in, check the sail, ease the sheet. Have to hike out, check the sail, sheet on.

At the foot of the sail, I gauge the depth by how far the middle of the foot is out from the centre of the boom. While we are not trapezing at all, I'd have the middle of the foot around 70mm out from the centreline of the
boom. Once we start trapezing I'd start flattening the foot until it is pulled flat by the time we are fully hiked and trapezing.
Luff tension should be just slack/relaxed. You can pull the sail just firm when you are fully hiked/trapezing. You usually don't need to overdo it, unless perhaps you have a old stretched sail where the draft is deeper and further back than a new sail. Tightening the luff can flatten that sail a bit and pull the draft forward.

Battens.
Use only enough tension to remove any slackness in the cloth along the batten pockets. You don't achieve anything by tensioning harder in different winds. If you want a different depth at the batten, speak to your sailmaker and/or change the batten stiffness.
And the best tip I can give you is to always leave the battens tensioned like that when not sailing, with just that slight tension on them. It saves the sail from getting little vertical wrinkles in them that are impossible to get out without over tensioning.

Jib.
Here you have less controls over the shape so you are reliant on the built in shape and the quality of the cloth to hold that shape.

In the wind strengths up until where you have to ease the boom out to stay level:
If you have athwartships jib tracks, they should be all the way inboard, and the foot is pulled in just until it begins to get distorted along the foot. It shouldn't get a strong horizontal crease along the foot.
When there, it's time to look at the top of the jib.
If the helmsperson is steering so that both of the bottom tufts are flowing, you want to adjust the sheet tension slightly so that the top two tufts match what the bottom ones are doing.
Top windward tuft lifts before the bottom one, sheet on tighter. If the leeward top droops before the bottom one, ease the tension a bit.
Then check that the leech telltale is flowing All the time. No flicking behind with this one.
If you want to get into even finer trim, there are degrees to which the leech telltale will flow. Flowing just to flowing easily. You can squeeze a bit of extra pointing in the right conditions, flat water, by going for just flowing.

Getting the meeting point of correct foot and leech tensions is mostly achieved by the positioning of the jib tracks and jib height on the forestay that we talked about earlier.

Exceptions.
In very light air, you may not be able to get the mainsail leech ribbon to flow while having the boom in the centre. That's ok, just ease it out until the top starts to work. We aren't really trying to point at a higher angle in light winds, rather we are just trying to move forward as speed will give us our height then by having water flow over the centreboard faster, creating lift.
You may also need to increase luff tension in these conditions to flatten the top of the mainsail slightly and open the leech a bit.

If there are more waves than you would normally expect for the wind strength, in other words, you are finding it difficult to keep momentum, you may need to ease the jib a little and perhaps the boom out a little too. But make sure the top windward tuft on the main is still flowing.
Be careful easing the jib, it may only take 10 to 25mm or so to open the leech quite a bit.

Strong winds.
From where you need the ease the boom out, and above.

Boat trim.

Sideways trim.

Not sailing the boat level, or flat, if excessive, will dig in the corner of the transom a bit and cause lots of turbulence behind the transom.
Not only that, it directs the power of the sails a bit downwards rather than forwards, losing available power, pressing the boat further into the water, making it appear heavier, and sailing on the more curved chine rather than the flatter bottom.
Sailing flatter directs the sail forces more horizontally, efficiently, and smooths the flow off the transom, and encourages the boat to accelerate in any gusts.

I gauge this by looking aft and comparing the top line of the transom with the horizon.

Really work hard at this. It is easy to think you are flat when you are not, and it does make a huge difference. It is probably the number one error to be seen in a fleet, and the most obvious, and easiest, Slow Spot to rectify.

Fore and aft.
Here the idea is to not be too bow down or stern down.
The ideal is to have the water leaving the transom smoothly, not bubbling up behind it, nor creating a sharp wave close behind the transom.
You just have to gauge this by looking aft.
Below planing speeds, note whether the water is smooth or turbulent.
Above planing speed look to see if the wake is long and flat or there is a wave pushing up not far from the transom.
If you see these problems , move forward in the boat.

Generally, the crew should be near the sidestays and the helmsperson astride the thwart if not planing, or just behind the thwart if planing.

Once planing, you want to achieve a balance of not dragging the transom and not having the bow dig into the waves too much, slowing the boat. The crew will be in the best position to judge this by sight, and the helmsperson by feel.
You may need to physically move fore and aft in waves to avoid digging into the worst of them.

Downwind, you need to trim even more fore and aft.
While you are near the top of a wave try to trim bow down and only move aft once you've caught the wave and also to avoid burying the bow into the next wave. You'll move back to neutral mode until you come onto another wave crest.
Don't be afraid to move significant amounts, both of you, to trim onto an off of a wave. Sometimes it is necessary.
Just be sure you do the movements smoothly and not come to a sudden stop when moving forward. That is Ooching and not allowed.

We'll talk more about stronger winds, steering and developing the feel for your boat next time.

Jamie
Thomson Sails
https://thomsonsails.com/