Speed & Smarts: Building boatspeed


Boatspeed 2008 IQ test

Expanded answers to last month's quiz on boatspeed, by David Dellenbaugh.

IN OUR April issue, we published a Boatspeed IQ Test with 56 questions about all aspects of what it takes to sail fast. We didn't have room in that issue to explain the answers in any detail, so here are the expanded explanations. (For a copy of the IQ Test, email vanessadudley@yaffa.com.au.)

General sail trim

1. True. A tighter leech gives the boat some “bite” and makes the bow want to turn up more, thus helping pointing. Of course, you must be careful not to trim the leech too tight and kill speed ð that would hurt pointing!

2. True. Drag is created by several factors including the shape, or depth, of a sail. A deep sail creates more drag because it produces more turbulence and flow, separation than a flat sail.

3. B, C, D. A badly tuned rig, wind sheer and waves not aligned with the wind can all cause asymmetries and require different sail trim from tack to tack. A cross-current affects both tacks equally and won't change trim.

4. A. You definitely need a lot of twist in light air and lumpy seas to keep your boat moving fast and avoid stalling the sail plan. You also twist the sails in heavy air to keep from being overpowered. You want the least twist in medium air and flat water.

5. D. Wind sheer aloft could cause differences in apparent wind angle, boatspeed and sail trim from tack to tack. However, the true wind direction will be the same on each tack even when there is sheer.

6. B. All of these are usually good ways to depower your main except for pulling harder on the vang. The effect of vang tension depends on the boat. If it bends the mast a lot this can depower the main but if it mostly makes the leech tighter it can actually add power to the sail.

7. D. You don't want to Ask overtrimming your sails in light air, lump or with an inexperienced skipper. But when you are not quite overpowered, this is usually the time for trimming your sails the tightest.

8. True. In choppy water you need a sail shape that is forgiving enough to keep working in a range of conditions. If you have too little twist, the sail will stall easily and it will be hard to get going again in the waves.

9. False. One reason why you need twist in your sails is because of wind gradient (not sheer). Gradient is an increase in wind velocity as you go aloft ð this moves your apparent wind aft as you go higher and requires twist in order to trim the sail properly.

10. True. The amount of power, or lift, produced by a sail is related to that sail's angle of attack (the angle between its chord-line and the apparent wind). By trimming the sail and closing the leech, you create more deflection in the airflow and increase power (to a certain point).

Boat trim and steering

11. A, C. When it's hard to find the groove, it's good to ease sheets slightly and foot off for speed. Trimming the mainsheet and tightening the backstay will only make the sails more critical and the boat harder to sail.

12. C. All those actions are good to power up the boat before you hit the waves, except you usually want to move weight a little aft, not forward, to keep your bow from ploughing into the waves and stopping the boat.

13. True. You can definitely move your body to help steer the boat through waves, and you should do this on lighter boats where your weight has an impact.

14. B. Four degrees is roughly the amount of windward helm you want. Less than two degrees won't give you much “feel” in the helm and it will be hard to keep the boat in the groove; more than about six degrees of helm usually creates too much drag.

15. B. It's important for the steerer to watch the telltales, the speed readout (if you have one) and the waves that you're about to hit. However, unless she has a great sense of feel for the helm, she should let her crewmembers watch the speed of other boats.

16. True. More heel increases the amount of windward helm because it: 1) puts more of the boat's curved side section in the water; and 2) moves the CE (centre of effort) farther from the CR (centre of lateral resistance).

17. B, D. Flattening your main or the boat will reduce windward helm, but moving the centreboard or your crew weight forward will increase it.

18. C. A round entry on the jib will give you a wider groove, more acceleration and better power to punch through waves. However, when you want to point high it's usually better to have a flatter, finer entry (unless your problem is building enough speed before trying to point).

19. B (or possibly D). When you sail into a lull, your apparent wind moves forward until your speed slows down to match the new wind velocity. The best way to handle this is usually not to bear off right away to keep your sails full; rather, bear off slowly in a gradual arc so your sails become full when your speed settles down.

Rig tuning

20. B, C. If you move the mast butt forward or tighten the lower shrouds you will decrease prebend. By moving the mast forward at the partners (deck) or angling the spreaders aft, you force the middle of the mast forward and increase prebend.

21. False. Getting the mast straight laterally is a good guideline, but this is not always fastest. When you need more power, for example, you may want the middle of the mast to sag slightly to leeward.

22. True. On most boats, the forestay limits how far aft the mast can go; therefore, its length is a good measure of rake.

23. False. An improperly tuned rig is one reason why you might have to trim your sails differently from tack to tack, but there are at least several other reasons that might explain this, including wind sheer and waves not aligned with the wind.

24. False. The backstay and runners are used for bending the mast and straightening the headstay, not for changing the amount of rake. You should normally measure rake with little or no tension on your backstay.

25. A, D. Large overbend wrinkles occur when the mast bends too much for the sail. Easing the backstay or moving the mast aft at the deck will reduce mast bend and decrease the number of wrinkles in the main. Tightening the vang actually bends the mast further and creates more wrinkles. The wrinkles will also be worse if you ease the cunningham.

Spinnaker trim

26. False. When you ease the spinnaker sheet until there is a small curl in the luff of the sail, you know that the spinnaker is eased as far as possible. Though you lose a little bit of projected area, this is better than having the chute overtrimmed at all.

27. True. Lowering the outboard (and inboard) end of the pole is one way to depower a symmetrical spinnaker. Like tightening the genoa luff, this moves the draft forward in the spinnaker and opens up the leech.

28. D. These are all good spinnaker trim guidelines except for the last one. Usually you want the centre seam of the sail to be roughly vertical ð if it angles to leeward there is a good chance the pole is too high.

29. False. It's usually fast to let your mast go as far forward on a run as possible. Among other things, this lets the spinnaker hang (fly) farther away from the mainsail.

30. True. It's always good to get the spinnaker further away from the mainsail, so you should keep the sprit pole fully extended downwind.

31. False. When you are running in breeze, you want an asymmetrical spinnaker to rotate as far to windward as possible so it gets out of the wind shadow of the mainsail. In order to do this, the tack line of the spinnaker must angle to windward as it comes off the end of the pole.

32. False. In most conditions, you should set the tack well off the end of the sprit so the chute can rotate farther to windward. However, if the tack moves to leeward when you ease the tack line (this may happen in light air or when reaching), keep the tack closer to the sprit.

33. True. The rulebook used to say, “A spinnaker … shall not be set without a boom. The tack of a spinnaker that is set and drawing shall be in close proximity to the outboard end of the spinnaker boom …” However, that rule was deleted in 1993, so you can now fly a chute without a pole.

34. True. Rule 42.3c says that in certain conditions you may “… pull the sheet and the guy [brace] controlling any sail in order to initiate surfing or planing …” So downwind you are allowed to pump the spinnaker sheet (and the brace too) once per wave or puff.

35. A, E. Good ways to increase control on a windy run include sailing a higher angle, over-trimming your spinnaker slightly and putting your board down a bit (but not too much). Easing the vang (which allows the main to twist) and moving crew weight forward (which puts more of the round bow sections in the water) will both make the boat harder to control.

Jib and genoa trim

36. True. When you tighten the backstay, this bends the mast and makes the main flatter. It also pulls the mast aft against the headstay, which straightens the headstay (reducing sag) and flattens the jib.

37. False. If the jib's leeward telltales are stalled, it's a good idea to ease your jib sheet to re-attach flow on the leeward side, But you wouldn't want to bear off because that would only stall the leeward telltales more; in fact, you might head up a little.

38. B. The ideal draft position in a jib or genoa is ty
39. False. Pointing higher is not as easy as simply trimming your jib more. In fact, trimming the jib tighter often has the opposite effect ð it pulls your bow away from the wind and makes you go slower, both of which are detrimental to pointing.

40. A, B, C. All of these are good guidelines for setting the fore-and-aft position of your jib lead.

41. False. In many conditions (eg, lighter air) you want at least a hint of horizontal wrinkles along the jib luff. This ensures that you aren't flattening the sail too much or pulling the draft too far forward.

42. False. When you pull harder on the jib luff tension, the draft in the jib moves forward. This makes the front of the headsail rounder, which is usually not too good for pointing.

43. True. If you don't get enough pre-bend, you will have to tension the backstay or mainsheet to bend the mast to shape the mainsail. This means you end up straightening the headstay (and flattening the headsail) more than you want. With the light pre-bend you can keep the jib fuller.

44. False. The best way to change gears with the jib (as with the main) is by adjusting the sheet. This is both quick and effective. Moving the jib lead is usually difficult as a short-term solution and is less effective.

Mainsail trim

45. True. When you ease the backstay the mast gets straighter, and fullness returns to the forward part of the mainsail.

46. False. When you are sailing upwind you usually want your boom near centreline. In order to get this, especially in lighter air, you often need to pull your traveller car well to windward of centreline.

47. A. When you tighten the cunningham, it pulls more cloth toward the front of the mainsail and thus moves draft forward. When you ease the cunningham, it does the opposite (adds fullness and moves draft aft).

48. False. The primary reason for adjusting the cunningham is to get the right mainsail shape for the conditions in which you are racing. Getting rid of wrinkles is not a strong reason for pulling the cunningham; in fact, having some wrinkles is often fast.

49. B. When the telltale on your top mainsail batten is stalling half the time, this indicates that your mainsail is trimmed nearly as tight as it can be. You would want to trim this tight only in flat water and medium breeze; certainly not in very light or heavy air.

50. True. Top batten parallel to the boom is a good starting point for mainsails on most boats, though you may need looser or tighter trim at certain times, depending on your boat and the conditions.

51. True. Easing the outhaul makes the lower part of the mainsail deepen This means there must be more “return” near the leech, and this tighter leech contributes to more windward helm.

52. False. It's usually fastest to hoist the main as high as possible, but there are times (eg, in light air) when hoisting it to the band creates too much luff tension. This often happens, for example, with older sails (which have shrunk). In these cases, it's good to lower the halyard a bit.

53. True. When you are sailing downwind, most of the air flow across your main is stalled, so the telltales won't be very helpful.

54. B, D. You usually need more cunningham tension on an older sail because, as sails age, their draft tends to move aft. You also need more cunningham in heavy air to move the draft forward as the mast bends.

55. B. Of course, the best position of max draft in your main depends on your boat and the conditions, but generally it should be around 50 per cent aft in the sail, or slightly forward of that.

56. C. All of these actions will help reduce backwind in the main except for easing the jib luff tension. That has the opposite effect because it makes the jib rounder in the back.

Upwind speed principles

Improving your boat's performance upwind will boost your chances of better race results.

IF YOU want to win more races, improving your speed upwind is one of the best things you can do. By going just a little faster through the water and/or pointing slightly higher, you will have much more success in holding a lane of clear air after the start and arriving at the windward mark in better shape. Here are some basic principles you can always follow to improve your boat's performance upwind.

– Copy what the fast boats are doing.

Your competitors are a great source of go-fast ideas, so keep an eye on them. Pay particular attention to boats that are going faster than you, and don't be afraid to copy their set-up. For example, how are they trimming their sails and positioning their weight?

You can learn a lot just by watching them on the race course; many sailors will also be willing to share ideas if you talk with them ashore.

– Use other boats to gauge your performance.

In order to optimise your speed upwind, you must always know whether you are going fast or not. Your sense of feel and instruments (if you have them) are two ways to gauge how well your boat is going.
However, these two sources mean nothing compared to the accurate feedback you can get by comparing your speed and height to nearby boats (see opposite page for more).

– Make reference marks to reproduce fast settings.

Developing a fast boat is a long-term effort that happens step by step. Part of the process is being able to duplicate your rig tuning and sail trim from day to day and week to week. What good is it if you're fast one Sunday but slow a week later because you completely forgot how the boat was set up?

Calibrate the key speed-related variables so you can repeat fast tuning and trimming combinations. When you're “in the groove,” note the numbers and record these in a notebook for future reference.

– Try a “wider groove.”

It's not easy to go fast 100 per cent of the time, but try to stay in the groove for as much of each leg as possible. One way to do this is by setting up your sails (eg, by making them a little fuller and more draft-forward) so you have a wider groove.

By doing this you'll give up a little high-end performance, but you will also have fewer times when you stall out and go very slowly. You'll be fast more of the time and improve your overall average speed (especially when you have waves or other conditions that make it hard to stay in the groove).

– Make changes methodically.

When you are going fast relative to other boats, make sure you remember where everything is set. When you are going slow, change something. Start by adjusting the mainsheet, jib sheet or backstay (if you have one) since these controls have a relatively large effect on speed.

When you change trim, do it systematically. Alter one variable at a time, if possible, so you can identify whether this makes you faster or slower. View this as a long-term process of discovering all your fast components and combinations.

– Shift gears all the time.

The wind and wave conditions change continually, so you must constantly adjust the trim of sails and hull in order to keep going fast. There's almost nothing slower than leaving your sheets cleated and your crew stationary when you get a puff, lull or shift.

Sailing is a lot like driving a car ð you can't just stick it in fourth gear and go up and down hills. You have to work the boat continuously by shifting gears.

– Concentrate and work hard.

Above all else, speed comes from an attitude and a desire to go fast. Focus on getting your boat in the groove and keeping it there. This may require hard work, but it will improve your upwind speed!

High and fast

When you're trying to improve boatspeed, one absolute prerequisite is knowing how fast your boat is going already.

Are you the speediest boat on the course, or slower than everyone else? The way you answer this question will have a huge impact on the steps you take with regard to speed.

The only way to know for sure how you are going is by comparing your upwind performance to a similar boat that is sailing nearby.

This is the main reason why all serious racing campaigns use extensive two-boat testing. With another boat sailing upwind beside you, it's relatively easy to see the subtle differences in performance that make such a huge difference when you're racing.

There are two basic and very important dimensions of sailing performance ð height and speed. Height is your pointing ability, while speed is your forward velocity through the water. When you add these two factors together, they determine your velocity-made-good to windward (VMG), which is an excellent overall measure of your boat's progress toward the windward mark.

Therefore, when you look at the boats around you, try to compare your height and pointing with theirs. Are you higher or lower? Faster or slower? More importantly, watch the boats for a few minutes and try to determine if they are making better VMG to windward than you. This is key to evaluating performance and improving your upwind speed.

The blue boat is sailing low and fast while the red boat is sailing higher and slower. However, their VMGs to windward are roughly the same.

On the blue boat: “We're lower and faster, net is even.”

On the red boat: “We're higher and slower, net is even.”

Assign one person in your crew to watch the boat(s) nearby and call out your relative upwind performance. This “speed reporter” should always talk about your own boat (for clarity) and should describe your relative height and speed.

For example, he or she might say, “We're higher and faster,” or “We're lower and the same speed.” In fact, there are nine possible statements that he or she could make about your height and speed compared to the other boat (see list below).

The purpose of this communication is to evaluate your upwind performance (VMG). In seven of the nine possible relationships, it's clear which boat has a better VMG; in two of them (the purple ones) it's not clear. In these two common situations, the speed reporter should try to give an estimate of which boat has a better VMG. For example: “We're higher and slower, net gain to us.” This will help you figure out how much you need to work on speed.

Nine possible ways to compare your height and speed to another boat How your upwind VMG compares to other boat

“Higher and faster”
“Higher and same speed”
“Same height and faster”
“Same height and speed”
“Same height and slower”
“Lower and same speed”
“Lower and slower”
“Higher and slower”
“Lower and faster”

Much better
The same
Much worse
Same, better or worse?
Same, better or worse?

This article is extracted from Speed & Smarts, a newsletter published by David Dellenbaugh filled with how-to information for racing sailors.

Dellenbaugh, tactician aboard the 1992 America's Cup winner and an adviser to the German United Internet team for the 2007 AC, besides being a top sailor is a skilled communicator on tactics, rules and boathandling.

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