A: Thanks for the note. Unfortunately, I'm not much of a mathematician. It looks like hyper elliptic mathematics yield shapes that remind the mathematicians of things they've seen in birds and fish. For wings I gather that hyper elliptic wings are curved along their span - not straight like most man made wings.

I'm a believer that there is a lot to be learned from the planform shapes seen in flying and swimming animals (a tuna seems like a study in extreme hydrodynamics to me). However, the furthest that I've gone with that idea is to make my foils "look" natural within the constraints of structure and the construction technique (i.e. I've always built them in molds with a planar part line). I've attached a picture of the planform of my most recent 14 hydrofoil.

All the best,
Paul

12/28/06

Light Air Start

Q: I have read about starting patterns and timing, but in our latest 6mR regatta I had an active J120 skipper on board for crew, and he kept telling me to get on the tail of the hot boat or the boat with a good run at the line and follow them (this was inside the last minute). For various reasons (light air, bad driving on my part, etc.) it never came clear what the objective was. I get some good starts, mostly in light air, but often I am starting with a lower third position in a fleet that has no speed stratum to let me use other talents to move up. What are the advantages to being on their tail? What do I do if somebody gets on my tail?

A: That’s a good question. What in the world was that J/120 skipper thinking??? Honestly, I have NO idea…. My rules of thumb for starting in light air include starting next to boats that are slower than you at the start, making sure you have clean air and having tons of speed. By following the boat with the best run at the line you ensure the outcome of your start will not be in your hands… If that boat has decent timing, at best you will start close to windward and slightly behind a boat that is sailing faster than target. Think of getting leebowed in light air – not very good for the windward boat…

If I were you, I would concentrate much more on your own timing and know where the starting line is. Next time you’re out there, take a few runs at the starting line before you start. Before you start a run try to guess how long it will take you to cross the line from where you are. Start your watch and sail full speed to the line. This is basic time and distance training. The more advanced drills would be starting from head-to-wind, with a tack, etc… Also think about the type of boat you’re sailing and how the fleet behaves in that wind condition. If you’re sailing a Laser, then work more on time and distance over a few boat lengths. In your 6m in light air, I would be getting good at your time and distance runs from up to 90 seconds out.

Once you have you timing down you need to work on finding the starting line. Use line sights ALL of the time. If you can get a friend to help you, put him/her in a motorboat at one end of a practice starting line. Run a few practice starts trying to have perfect timing. Have your friend radio telling you when you are actually on the line.

With some practice, you will be better than anyone at your timing. I promise your light air starts will improve.

Andy Horton

Got a tactical question? Send it in!

12/11/06

Q: Situation this summer. I am windward and behind competitor (Harri) is leeward and ahead. We are both sailing Lasers and we agree that my bow and his transom were in line with about a boat length separating us. We are on Port tack. Wind is about 4 Knots. Flat water. A small puff comes in and this causes him to begin his tack.

Harri says “Tacking” and begins his tack. I say no you’re not. He does not hear me (He has tinnitus.), and I bear off slightly to try to close the gap before he can finish his tack. We meet with my bow at his mid-ship and not quite at 90 degrees to each other. I luff to avoid him and then slowly complete my tack. He is worse off as he is slowed by the whole maneuver and ends up behind me. There is no contact, but Harri insists he had completed his tack and was rolling his boat flat and had to luff up to avoid me. As his boat was obscured by my sail, I can not confirm this claim, although it seems that given our beginning positions, it would have been impossible for him to do this.

Is this just one of those times when you need video, or is there some kind of rule-of-thumb for spacing required for a tack?

A: n your specific situation Harri must complete his tack (turn all the way down to close-hauled on starboard) before you need to start avoiding him. You are required to start avoiding him the instant he completes his tack. If you don’t have enough time to avoid him then his tack was too close. On the other hand, you are in the wrong if you don’t immediately start avoiding him once he completes his tack, or you don’t try to do everything in your power to avoid him. You would be wrong, too, if you could have easily ducked him and instead tried to tack (tactical decision) and fouled him by tacking too close. That’s a simple summary of your options under the basic rule.

Now for the hard stuff…. You said, “I luff to avoid him and then slowly complete my tack”. Could you have turned faster at the end of your tack to avoid the situation? If so, this wouldn’t be very good for your case.

Harri however also might have a little problem. It sounds like he tacked so close to you that even if you had tacked immediately and quickly he might have still needed to luff to avoid you. If that was the case then he also broke a rule by gaining right-of-way (starboard tack) and not giving you enough time to keep clear. I can imagine Harri’s response to this, “The boats didn’t hit, so I must have given you enough space to keep clear”. Honestly this is my gut reaction also, but the way the rule is interpreted you need to tack with enough room for the other boat to tack without having to luff to avoid him….

The funniest protest I have ever been in was a tacking-too-close protest. This one should have made it into Dave Perry’s book. We were sailing Mumm 30’s in Newport, RI a few years ago. I was asking a starboard boat if we could cross. They were yelling, "Starboard!" As we got closer, it was clear we would cross, but not by much. Since they clearly wanted us to tack, and because it would be a close cross, the safe bet for us was to tack and not to risk a protest.

So, we tacked in front and slightly to leeward of the starboard boat. They tacked away and started screaming at us saying they were going to protest and a bunch of other things… When we got to the dock, someone on that boat came up to me and said they were protesting. Later, I tried to talk them off the cliff, but they wouldn’t listen and wouldn’t talk about the situation.

My argument was simple: They had wanted us to tack and not cross. (Since we would have been crossing them prior to our tacking, there was a 100% chance they were going to get leebowed and be forced to tack away anyway. This means they must have wanted to go right and not allow us to go right.) That is, in fact, what happened, so what’s the problem?

We went into the room, and in his opening statement the guy representing the other boat said, “Andy tacked in front of us, then we had to luff to avoid him and there was no contact”. The committee looked over at me and asked me to explain the situation. I told them it was word-for-word exactly how the other guy described it and I didn’t need to ask him any questions.

We completed our tack, then he luffed to avoid us, and there was no contact. No rules were broken. The committee disallowed the protest, and the whole proceeding took about 30 seconds.

I don’t think you and Harri have such a cut and dry situation. Sounds to me like both of you weren’t 100% clean. The nice thing is that is also sounds like the two of you discussed the situation and left it on the water, which is nice….

Hope that helps,

Andy

Comments on this article.

11/28/06

Q2: Would also appreciate your views on Carbon vs Kevlar or aramid. I believe that Carbon mixtures (e.g Carbon / Tarwon) are more brittle and do not flex well. So although they might hold their shape better they are probably not going to last as long. Given we sail on a budget I would probably opt for longer lasting sails -- especially for the mainsail. Our gennie is the power sail so may be worth sticking to Carbon. Would we lose much speed vs carbon?

A2: Carbon fibers have lower stretch than aramid fibers and they
are impervious to UV. Carbon is more brittle and can break when folded sharply. Try rolling your sails (particularly the main) when putting them away. No, there would be no appreciable speed difference when the sail is new, only over time with lower stretch would the carbon show its edge.

09/14/06

A 30 foot boat is still small enough that you can make a very good main in Dacron. Except for the windiest conditions the Dacron sail will hold its shape as well as a composite sail. In fact after 3 seasons or so the Dacron main will probably look better than a composite main. There is a small difference in weight that will have an effect on pitching and heeling moment, and the lighter the boat the bigger that performance factor will be. For the jib you will certainly want to stay with some type of composite construction.

In order of shape holding ability, which also strangely corresponds to cost, the different constructions are:

D4 (because that is what we build) or other load path type sails - These are the lightest and best shape holding sails on the market today, but 3 years will be pushing the range just a little due to the cracking and scaling of the mylar films that will be happening by then.

Carbon Paneled sails – Certainly proven to be have the longest competitive life of any racing laminate sail on the market today. We have lots of these out that are in their 4th and even 5th year. The longevity is due to the natural UV resistance of carbon and the good flex properties of the yarns in this type of lamination. Expect the paneled sail to weigh 10% to 15% more than a D4.

Aramid tri-radial paneled sails – For local day racing this is a good option if the price of the D4 and carbon sail is out of your budget. In sails this size they will be as light as, or slightly lighter than the carbon paneled sail. Their shape holding ability is as good as the carbon when the sails are new but will go down a little over time because of the UV and flex degradation. They should go 3 years in normal use but if you sail in the southern latitudes like Florida or Hawaii where the UV exposure is high they may not last a whole lot longer than that.

Aramid or Carbon/Aramid cross cut sails – Contender has their MAXX line of fabrics and Dimension has their FLEX line. Both types work well in mains and high aspect ration jibs where most of the load is going vertically up the sail. They are not quite as good on lower aspect roachy mains where you will have more off axis loading. We have done sails in both fabrics including quite a few J105 and J109 one design mains and jibs where they are being very successful. They are going to be a little heavier than the paneled tri-radial sails because you will carry more off axis fibers in areas that don’t need them, and because there is no really good way to use different strength cloth in different areas of the sail. Longevity is still a bit of a question because we don’t have any of these sails that have been out for that long. My believe is that we will see more change in shape over the long term in these cross cut laminates because they don’t have totally correct yarn alignment in some areas of the sail, and therefore have to rely on the mylar film to carry more of the load.

Pentex tri-radial sails – Personally, as stated in this forum before, I am not a big fan of Pentex sails except in one design classes where they don’t allow anything better. They are much too stretchy for the small price difference. In this application they will work but will be quite a bit heavier to get anywhere near the shape holding ability. They are better in UV resistance than Aramid, but not as good as Carbon.

07/27/06

Would building the sail out of either Cuben Fiber or Radial Hydranet deliver a sail that could hold an effective club race sail shape for over eight years?

Assume a 40 foot masthead keelboat, roller furled, with the priorities of:shape, life span of that shape, and the sail in use for about 400 hours per year.

A: Increasing your budget isn’t going help; I don’t know of any fabric that will really hold its shape for 8 years as a racing sail. In all honesty a good Dacron cross cut sail will probably be the closest you get.

Cuben fiber is definitely out, as is any other laminated racing type fabric. None of them are going to last 8 years, let alone last 8 years with good shape for 3200 hours of sailing; and keeping any of them on a furling system will only make the longevity worse. The radial hydra-net will probably last that long, but it certainly won’t have the same shape it had for the first few years, and it is really too heavy for a racing genoa on a 40 foot boat. The lightest Hydra-Net 343 Radial cloth weighs 8 oz. The cruising laminates are similar; they will probably last that long but they won’t hold a racing shape that long and they are all very heavy for this size boat.

The closest thing that will hold a competitive racing shape is the Challenge PinStripe Aramid. It is a radial Dacron with Aramid fibers woven in. I have seen sails that have been very competitive after 5 or 6 years of sailing but that is certainly pushing the limit.

Racing laminates with mylar on both sides are good for 2 to 4 seasons depending on how critical you are about shape, and will probably physically wear out in that amount of time. Laminates with a taffeta on one side will hold their racing shape about the same but will get another year or two of use before they physically wear out.

Hydra-nets and Cruising Laminates are very heavy for a 40 foot boat genoa and may last 8 to 10 years depending on use but their racing shape holding won’t be as good as a laminate racing fabric.

PinStripe aramids will last 5 to 6 years and their racing shape will generally last 1 to 2 seasons more than a similar laminated fabric. They are generally a little heavier than the good racing laminates.

Dacron will last 10 to 20 years depending on use. It will never hold its shape quite as well as a racing fabric, but it also won’t change as much over time.

Ask Someone

Board Game

This week, Luke Shingledecker from Farr Yacht Design tackles design questions.

Q1:I'm curious as to why the dagger boards on the ORMA 60's are angled inwards so as to become more horizontal when heeling as opposed to the V.O 70's boards that become more vertical..

Q2: On the same topic why are the boards curved (on the tris)?

The boards on a Volvo 70 (and on Open 60 monohulls) have the job of creating side force, to counter the side force from the sails. Because the keel is canted to weather, the keel cannot produce side force very effectively, but the daggerboards on a Volvo 70 have camber (like an airplane wing) so they can be very efficient. In addition, if they are angled outboard, they become nearly vertical when the boat is sailing at heel. When they are vertical, they produce side force more effectively than a foil that is inclined.

On the trimarans, there is a central daggerboard in the main hull and boards in the outer floats. The main board is deep, and can produce side force effectively because the multihulls sail at relatively angles of heel. When the boards in the outboard floats are angled inwards (so that they become more horizontal), they produce both side force and a vertical force. The vertical force helps keep them from nose-diving at high speeds, and effectively reduces the boat's total weight and therefore drag. By making the boards curved, the upper part of the board is more vertical and creates side force. The lower part of the board is horizontal and it creates more vertical lift.

The monohulls aren't as concerned with nose-diving, and it is more important for the boards to create side force efficiently. Therefore they use the boards angled outboards.

Luke Shingledecker
Naval Architect

06/09/06

Ask Someone

To Sprit Or Not To Sprit...

We've been a bit lax getting these together, but the Ask Someone series is a good opportunity for you to get your questions answered by the best in the business. Sailmaking, rigging, tactics, design, whatever - send them in and we'll get them done for you. This edition is answered by designer John Corby.

Q: From a racing and rating perspective is it worth converting a conventional asymmetric non-panning boat over to a bowsprit and asymmetric spin? Is the extra sail area and ease of handling of the asymmetric going to out-weight the likely rating penalty and the extra distance sailed downwind to keep the sail driving?

Is the answer very much dependent upon the hull shape and weight? Specifically I am thinking of boats of around 28-32 ft LOA from the old quarter tonners through to modern production cruiser racers.

Assuming it makes sense, how do you work out the ideal length of the bowsprit?

A: IRC is pretty fair about poles and sprits. You get a rating credit for a sprit because you cant square it back but you then spend that credit on more sail area.
Sprits work better on larger boats, eg over 40 foot, because of two reasons: a) sail handling is easier and b) larger boats tend to be proportionally lighter and are quire nippy when sailed on hotter downwind angles. An old IOR 30 footer won't get up and go in the same way and also its spinnaker pole isn't a great drama so I would stick to a normal pole and spinnakers.

In terms of sprit length, just what looks right! 2m on a 41 footer. 1.5m on a 29 footer might be decent guidelines.

06/02/06

Q1: Most of us have seen the famous shot of Silk II bow down carving up the corn field. Is this due to the lack of volume in the bow sections of modern IRC designs?

A: This pitch pole in relatively flat water is likely due to a number of factors. In part the driving force is a good distance up the rig, roughly 40-45% when velocity gradient effects are considered. The drag of the boat is definitely below the waterline when the total of hull drag and appendage drag is considered. The driving force and counteracting drag combine to set up a bow down trimming moment. For all boats, the faster the boat goes, the greater the resistance and so the higher the required driving force. For displacement boats the curve goes up very steeply as they try to exceed hull speed. Consequently, this bow down trim moment gets quite large. When boats plane the drag goes up less steeply.

The bow down trimming moment is counteracted by people moving aft (crammed in the pushpit in this case) and also by dynamic lift of the hull. Dynamic lift is the same as a power boat trimming bow up as it starts to plane. For some boats the dynamic lift doesn’t get large enough to overcome the trimming moment. In the extreme, think lead-bellied IOR pintails. This can also happen in more modern boats if the boat gets knocked off a plane by some bad chop or sticking the nose through a wave or recovering from a minor spinout. Then the apparent wind speed increases since the boat slows and the dynamic lift isn’t there because the boatspeed has dropped. So, it isn’t necessarily fine bows, but a combination of many factors.

Q2: Or does it have to do with the placement of the bulbs hung on the keels?

A: The fore and aft location of the ballast certainly can change the trim of the boat. This affects the baseline trim which can be changed by the crew moving fore and aft and the pre-race storage of sails and gear. Once a boat’s fore and aft trim is fixed the bulb location doesn’t materially affect the dynamic lift or the driving/drag trim moment. It is quite possible that some boats are trimming more bow down in empty condition in order to shorten the waterline length (LWP). For most boats the bow overhang is much more vertical than the stern overhang so trimming down in the bow results in shorter rated length.

Q3: And finally, does the amount of rocker have any bearing on the performance vs rating under IRC?

A: Rocker affects several aspects of the boat, some rated in IRC and others not. When a boat pushes to and above hull speed, some rocker can help the boat naturally achieve a more bow up running trim. This can help the boat climb over the bow wave ahead. It can also make the boat look shorter to IRC with the assumption that the boat will need to be going faster before the stern overhang is full immersed. Rocker also affects volume distribution along the hull and hence the prismatic coefficient and longitudinal center of buoyancy which play into tuning for light or heavy air, etc.

Here is a photo of a boat (The Andrews 80' Magnitude -Ed) at the other end of the spectrum, planing along after just blowing the vang in a gust off the hills between Koko Head and Diamond Head.

05/23/06

A: While working as a designer at Bruce Farr’s office, The Mumm 30 was one of my projects. I had lots of experience with this size of fast keel yacht, having designed and raced quite few similar 30 footers in California.

I developed most of the plans for the Mumm 30 working with Bruce, who always had his hand in shaping the hull. The rig on a Mumm 30 is very large, making the yacht fully “powered-up” in anything above 8 knots TWS. The rig was designed to carry both masthead or fractional asymmetrical and symmetrical kites, and developed to carry masthead sails without jumpers, to simplify the mast fittings/tuning. The weight normally associated with the jumper struts and stays was converted into additional carbon laminate in the upper mast – it is built very strong.

The Mumm 30 is fitted with a normal pole to gain an advantage in windward/leeward races when sailing against other designs with prods. The Mumm 30 has quite a heavy keel, moderately light construction & inboard diesel, which means it is not an ultra-light by any means.

Although the boat gets up and goes quite fast in a breeze, it is important to keep the rig and yacht all headed in the right direction, or the big rig will quick take control, making the rudder somewhat useless

Carrying a masthead kite in over 25 knots of breeze can be “interesting”. The good news is that as soon as the chute collapses, that the heavy keel quickly rights the yacht, and off you go for more.

Generally the boats and rigs are reasonably robust. Until you and your crew get used to the boat, error on using smaller kites in breeze.

Good idea to concentrate crew weight aft running with the big kite in breeze

If you’re not sailing in class races, consider adding a fixed bowsprit to carry the tack line for the A-sails, it’ll make gybing much easier.

Hope this helps – have fun.

James Donovan
jp donovan DESIGN
(410) 212 6114

04/20/06

Tripping

Designer Bill Tripp handles this one.

Q:Our crew is moving from an IOR boat to a Tripp 47. What are some of the upwind and downwind differences we will experience?
Also, what are some of the habits we may have built up sailing an IOR design that we want to make our selves aware of and avoid falling back to while sailing the Tripp design?

A: There are two different generations of 47's - one from '91 and the other from '96. The boats are two design generations apart, and sail differently. Among other things, the '91boats were mid-level production, built in both fractional and masthead versions. The '96 versions are built to a higher spec and are fractional rigs. Upwind, you will need to sail the boat with twist in the mainsail. Don't' sheet the mainsail hard, and be sure to drop the traveler. That is just a big airbrake! Open and close the mainsail leech subtlety with the top batten going from straight aft to pointing 5/10 degrees to leeward. Once the boat is going full speed, in winds over 13/14 knots, pointing will come through speed first, so it is important to get the boat up to speed.

Downwind, you need to move the boat around, changing your true wind angle more than an IOR boat, as the boat heats up faster and can burn deeper. Turn her up in the lulls before the speed drops and down in the puffs once the boat is accelerating. Hope that helps!

04/11/06

Design This

This short and to the point Ask Someone answer courtesy of designer Tim Kernan. Send in your question and have it answered by the pros (or at least someone pretending to be).

Q: I have been inspired by Purple Haze and the Red Sled and would like to build something similar in the 20 foot range. However, I am a complete novice when it comes to design. Would someone be so kind as to give me some basic pointers?

A: Good: Buy “Principles of Yacht Design” by Larsson & Eliasson.

Better: Buy a set of stock plans and modify details if necessary.

Best: Hire a good designer to work with you.

Got a question? Send it in and have it answered by the pros (or at least someone pretending to be one!)

03/13/06

Hooked

Questions asked and answered here. Just send them in. Thanks to Harry Pattison from E/P Sails for this answering this one.

Q: I have a Santana 30-30 pc. Masthead rig. Inboard genoa tracks. My No. and no. 2 headsails (153% and 140%) both have good shape in terms of draft location and amount of draft. However, both also have one odd feature - I am getting approx. 3 inches of leach hook to windward in the aft 10 inches of the sail. This hook is in the middle third of the sail - the head and the clue do not show the hook. The hook is not extreme, but it is there. I have tried various combinations of halyard tension, backstay tension, sheet tension and at times I can remove the hook but there does not seem to be a "formula" that I can repeat to consistently remove the hooking. It does seem that the hook is present at the lower end of each sails range and as the wind builds the leach tends to flatten out. Ideas (that don't involve firearms)?

Best regards and thanks for the time.

A: All genoas will have some amount of hook in the leech after they have been used for a while, but 3” is certainly extreme. Genoa leeches flutter a little bit because air flow will not usually stay attached that far aft in the sail. As the flow becomes turbulent over the leech it causes the leech to become unstable and it starts to flutter. This is taken out by applying just enough tension on the leech line to cup the leech slightly and take the flutter out.

The first thing I look at is to make sure the leech line is loose if I see a lot of hook. People often tighten the leech line to stop the sail from fluttering as it get windier, and then don’t ease it back off as the wind lightens. The more wind you have the tighter you have to pull the leech line, so the more important it becomes to let it back off in lighter conditions. If it is not as simple as the leech line you need to look closely at the shape of the sail. With a three inch hook I think the problem is bigger.

You didn’t mention what your sails are made of but I’ll assume they are some type of laminate. All laminate sails shrink, and they shrink more in areas that are fluttered and impacted. Because the genoa leech impacts on the shrouds and mast during every tack the area where it overlaps the rig shrinks more than the rest of the sail. As this area shrinks and gets tighter the area aft of it appears to get looser and falls off to leeward; which results in having to put major leech line tension on and this results in a very big hook. Go out sailing in medium air and let the leech line off all the way. Look at the leech section of the sail and see if the leech comes back smoothly until you get 12” to 18” in from the leech and then seems to get loose. Often it will look like the back 12” has a gutter shape to it. This sounds like you problem because you said the hook gets better as the wind increases. This is because as there is more load on the sail it will start to stretch the mylar film back out towards it preshrunk shape.

If the sail is not too old your sailmaker may be able to fix it, or at least make it better.

02/07/06

Reefer

Q: I have a 52' sled with double line reefing. I often single hand or have inexperienced crew. I am considering switching to single line reefing. I do not race the boat, but cruise extensively distances far from home in unsheltered waters. Would single line reefing be better for me to manage from the cockpit or when I am single-handing?

A: Single line reefing system has been one of the best and more practical systems for shorthanded crews and it would be ideal in boats up to 30 ft. On larger boats the friction is increased to a point that the system will not work properly. Even though, during some sailing tests we were able to apply the Single Line Reefing system on boats up to 40 ft. without problem, it is not recommended.

Our suggestion in this case is to rig a Double Line System lead back to the cockpit. This will help you to stay in the cockpit when reefing. This dual line system is very popular on big boats since the load is spread between more points, which makes it easy to use on 50 footers.

The graphic may help (courtesy of Harken).
A stainless steel eyestrap must be installed on one side of the mast with the right angle following the path of the line coming from the grommet of the "new tack" and then be tied and lead back.

By clicking here, you may find the parts needed to rig the simple and efficient system. Also you will need a dedicated rope single clutches on each side. Spinlock is a good way to go. This will show you some options according to the size of the line.

Please contact us with any questions or comments. We are looking forward to help you with your sailing needs.

Sincerely,

Rod Favela
Mauri Pro Sailing
We share your passion for sailing

01/24/06

Tweaker

This week's Ask Someone is courtesy of Harry Pattison of E/P Sails.

Q: With regards to gybing symmetrical kites on yachts, we have had an ongoing arguments regarding the use of tweakers. We dip pole the kites that are both mast head and hounds (7/8th). The ongoing debate is whether or not to snug the tweakers down when gybing these kites. I was wondering if The Experts might like to throw in their two cents.

A: Matt,
Since you are doing dip pole gybes you are using separate afterguys and sheets. The afterguys should be led to the deck well forward so they will be helping to hold the pole down as you come out of the gybe.

The only time I would recommend pulling the tweakers down on the sheets in a gybe is in very windy conditions when you need to stabilize the spinnaker as much as possible and keep it from oscillating. In normal conditions you don’t want to choke the spinnaker down, but allow it to float through the gybe. It will stay filled much better.

01/10/06

Back the Shield

We haven't done one of these for a while, and we want you to keep the ball in play. Send your questions in that you might want answered by a professional in the biz. Here both Ken Read and Chuck Allen from North sails show a level of attention to these questions that is truly impressive. Well done and thanks very much.

Question 1: I sail Shields and Etchells. Lately I've noticed a trend in both towards much slacker forestays than the tuning guide states. Very fast sailors have been adding inches to the forestay, adding tons of sag, and it seems to be faster. Why would this work? Is it because it allows you to flatten the main more while leaving the jib entry really open, or something else? For every person that does this, there seems to be a different explanation.

Answer 1: CA on Shields tuning: As far as your Shields Class questions, you are right on the mark when noticing that class members are changing it up a bit and "modifying" some of the tuning numbers that have existed for quite some time. Some key factors to making The Shield go are: headstay length, rig tip placement and reducing friction on the controls.

We are finding that adding around 1 1/2 - 2" to the forestay datum, in our North Sails Shields Tuning Guide is about right. You need lots of headstay sag to create enough power to get The Shields through any type of chop and/or light spots. Read on.

01/04/06