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-   -   Good boat designs for sails windward (http://www.sailnet.com/forums/general-discussion-sailing-related/61341-good-boat-designs-sails-windward.html)

quicksilver512 01-17-2010 12:34 PM

Good boat designs for sails windward
 
I tried Google last night without success, so I have to ask you veteran sailors. What are the design elements in sailboats that lead to better performance going into the wind?

bobmcgov 01-17-2010 02:22 PM

These are generalities, and others will leap in with counterexamples, no doubt -- sometimes it's a happy combination of elements rather than a mere assortment of features. But these characteristics are fairly conducive to upwind sailing:

* Sloop rig with high-aspect, powerhead mainsail and/or full battens.

* Large overlapping headsail, either fractional or masthead. A good genoa supplies much of your drive to windward. Ability to sheet headsail in tightly, or at least control the slot.

* Long waterline, narrow beam. Some people subscribe to a v-shaped keel for added lateral resistance, others prefer some kind of hard chine.

* High ballast ratios to keep the boat somewhat upright and reduce leeway.

* Fin keel with NACA foil profile: the deeper and narrower the better. Deep narrow fins w/ bulbs is the trend.

* Spade rudder, likewise a lifting foil. Possibly dual rudders to keep the foil vertical when heeled.

* Perhaps non-intuitive: slow boats may point better than fast ones. A fast boat moves the apparent wind onto the nose and must sail wider angles. A slow boat's apparent wind is closer to the true wind and it should point higher. The old 12m boats were paragons of pointing, but they were much slower than an Open 70, speed-over-ground. Despite narrow hulls & flat sailing attitudes, fast multis often have trouble pointing above 60 degrees because their apparent may be 2x true wind speed.:eek:

klem 01-17-2010 02:59 PM

To add to what bobmcgov wrote,

Sheeting angles are very important. This is one of the reasons that you see inboard shrouds on a lot of boats.

Sail shape is important. The ideal shape for a sail will change with the point of sail.

Faster 01-17-2010 03:01 PM

I'd add narrow sheeting angles coupled with underbody configurations that won't stall when you try to sail that high...

Not too sure that large overlapping genoas are especially conducive to pointing ability on their own. These headsails came into the fore to make up for the lack of sail area of the skinny high aspect mains of the day.... depends more on sheeting angles. Look at all of today's non-overlapping rigs like the Farr 40 and others you'll see out on the race courses.

Hopefully Jeff H will chime in with the definitive essay on the subject.

catamount 01-17-2010 04:11 PM

In addition to sheeting angles for the headsail, the ability to maintain or adjust tension on the headstay is also important, typically done with some sort of adjuster on the backstay -- i.e. tightening the backstay will in turn tighten the headstay, reducing wind-induced sag and maintaining sail shape and pointing ability.

Generating hydrodynamic lift from the keel is also really really important. Deeper fin keels with appropriate foil shape are best. If the boat stalls, you want to fall off to get flow going over the keel to start generating that lift.

Obviously righting moment will be important, too -- thus the heavy bulbs on the ends of long keels, and the row of heavy people hanging by their butt cheeks from the weather rail. Generally, the more upright the sails are, the more effective they are at moving the boat forward rather than sideways.

trantor12020 01-18-2010 09:17 AM

I think the best sail for going head into wind would be the iron genny. no tacking requires. :)

FishSticks 01-18-2010 10:13 AM

I've heard no mention yet of the schooner rig, but mine goes like blazes and is downright comfortable when I abide by the rule stated below. I'm 74-1/2.

sassafrass 01-18-2010 01:37 PM

to all the items listed

i would add new sails or sails in very good condition.

narrow entry is very important.

tom

Jeff_H 01-18-2010 04:37 PM

I am not precisely sure what the original poster is asking. Normally, when I think of a boat that sails well to windward I think of that as the boat offers the best VMG (velocity made good) and not necessarily the one that points closest to the wind. There are three main factors which control how well a boat goes to windward, the ability of the sails to maintain flow at a particular angle to the wind, speed through the water, and the ability of the boat to resist leeway.

Upwind speed is a matter of minimizing drag, since drive is limited. Anything that adds drag will reduce VMG, so efficient sails and efficient underwater foils (keel and rudders) are important windward performance. I think that the posters above have hit the high points, but there are a number of items that I respectfully suggest could be a little misleading.

* Sloop rig with high-aspect, powerhead mainsail and/or full battens.
I agree with the sloop rig as being the most weatherly of the modern rigs. As noted tongue in cheek, schooners for all of their virtues do not point well because of their high drag and downdraft issues. Powerhead mainsails while good for reaching, are not so hot upwind where they offer more drag for the lift. It is also harder to control twist in the leech of a powerhead mainsail which also hurts upwind performance.

* Large overlapping headsail, either fractional or masthead. A good <?xml:namespace prefix = st1 ns = "urn:schemas-microsoft-comhttp://www.sailnet.com/forums/ /><st1:City w:st=high points, </st1:City>but I disagree with several points that have been mentioned as follows:

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<font face=" /><st1:City w:st="on"><ST1:pGenoa </ST1:p</st1:City>supplies much of your drive to windward. Ability to sheet headsail in tightly, or at least control the slot.<O:p</O:p

Actually, large overlapping headsails are far less efficient upwind than non-overlapping sails because of greater drag per drive of the low aspect genoa and the interference between the trailing edge of the genoa and the mainsail. Overlapping genoas also tend to have wider sheeting angles than non-overlapping headsails. Overlapping headsails are a left over design feature from antiquated racing rules.

* Long waterline, narrow beam. Some people subscribe to a v-shaped keel for added lateral resistance, others prefer some kind of hard chine.
<O:p</O:p
I agree with a long waterline as that tends to stabilize motion and reduce drag due to wave collisions. Fine bows tend to track well and offer some lateral resistance as well. But, Vee shaped hull sections tend to have more wetted surface and have more induced drag and so are not good for windward performance. There was a time when much of the resistance to leeway derived from the hull. For the past quarter century there has been a general consensus that the best windward performance is obtained when the hull is designed to minimize drag and leeway is addressed with the highly efficient foils.
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Narrow beam is helpful up to a point, but reasonably larger amounts of stability are more critical to upwind ability and so a boat with a moderate beam rather than a narrow beam will often offer a lot better windward performance.

* High ballast ratios to keep the boat somewhat upright and reduce leeway.<O:p</O:p
I agree that keeping the boat upright is important for upwind performance, but again, its all about how its done. High stability allows a boat to stand up to a taller rig and therefore get by with higher aspect ratio sails resulting in a higher efficiency sail plan. Simply adding ballast is not necessarily a cure-all since greater ballast means greater displacement and greater displacement results in greater drag.
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The best windward performance is achieved by keeping when a conscientious effort is made to minimize the weight of the boat and her gear and concentrate the weight as low as possible which is why bulb keels have become the norm. Bulb keels allow a lower ballast ratio to offer a lot more stability. Again its all in the execution. Big, poorly modeled bulbs can offer a whole lot of drag as well.

* Fin keel with NACA foil profile: the deeper and narrower the better. Deep narrow fins w/ bulbs is the trend.

* Spade rudder, likewise a lifting foil. Possibly dual rudders to keep the foil vertical when heeled.<O:p</O:p
Dual canted rudders that work at larger heel angles are great for reaching, but are not so great upwind where sailing flat is critical and the added drag of a second rudder can really hurt rather than help performance.

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Jeff

quicksilver512 01-18-2010 08:15 PM

Thank you all for your input. Thank you Jeff for simplifying the topic for me. I saw reviews of two boats, a Compac 16, and Westerly 26 twin keel, and read that they both perform poorly going into the wind. I looking to buy my first boat, and wondered if their was a particular hull design to look for.
I am so new that I had to google iron genny. Thanks again.


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