Why can racing sailboats haul in their sails so close?

[Sublime]

For example:
http://www.charterworld.com/news/wp...-Photo-Credit-Andreay-Francolini1-665x442.jpg

The booms are often so very close to the middle of the boat. if I were to pull the jib and main that close, I'd have a lot of heel without much forward movement, so I don't get how they can haul sails in so close and still go charging through the water like they do.

 

[RichH]

Couple of reasons for this:

1. The sails used on racing boats are cut very precisely with very flattish luff sections (requires extreme precision by the helmsman/trimmers) in contrast to a 'cruising cut' which gets its 'forgiving' characteristics from being 'rounded' in luff shape. Such racing cut sails are very efficient even when held close(er) to the boats centerline.

2. The newer racing boats have very broad flat sterns with lots of beam in the aft section ... this sets up the boat to be able to point much higher than the traditional boat with a more symmetric hull. The 'triangular shaped' hulls when heeled over have the advantage in that the side immersed due to heeling becomes angled 'to weather' ... think of a keel that can be rotated about is long axis in relation to the boats centerline for best lift to weather. The simplicity of this triangular shape advantage is that its easier to point if your hull sides are already going in that direction, instead of 'straight'.
What youre seeing isnt necessarily that the sails are overtrimmed toward the centerline but rather that very broad stern visually makes it look like the sails/boom, etc. are much closer to the centerline than they really are. In all reality the sail's attack angle for main and jib remain fairly close to that angled 10° offset line between tack and clew.

3. The square top mainsails are simply more efficient for pointing, etc. than a triangular topped mainsail where the 'sharp pointy top' is producing a LOT of drag due to formation of a parasitic 'tip generated rotor' streaming back from the very top of the sail.
The probable best 'shape' for sailing speeds is the arrangement of primary wing tip feathers of the birds who soar (produce minimum 'tip rotor' hence less 'drag') ... the square top is closely attempting to imitate birds with large extended primary feathers.
Many experimental attempts to use 'primary feathers' at the head of a sail have failed ... probably because birds precisely control the interaction of each primary feather in relation to the adjacent primary feather.
Also too the flat top allows the leech to be somewhat perpendicular to the horizon ... more efficient leech as all the flow is exiting the sail perpendicularly across the leech instead of at an angle.
The WWII British Spitfire elliptical wing was the first modern attempt to closely imitate 'bird wings' including the 'tip' section --- was a major success in increased aerodynamic efficiency.

4. Most of all the serious racing boats accurately control the 'slot distance' between the jib and main ... accurately controlling the slot distance greatly enhances flow over the mainsail which in turn enhances the flow over the jib which enhances the 'upwash' of air in front of the the jib (air 'getting out of the way of the oncoming boat).
Example: To adjust the 'slot-distance', my sportboat/scow has independent athwartship radial jib (traveller) tracks in addition to fore/aft jib cars (actually I adjust the fore/aft position entirely differently but what I stated will suffice to keep it 'simple'), ... nevertheless this boat becomes a pig if the slot-open distance isnt accurately set for the exact wind/wave conditions. (The downside is that you need many more control lines to do all this and the boat is no longer 'simple'.)

 

[Slow Mo^cean]

Not being a smart ass, but my guess would be having something to do with the millions of dollars of R&D and cutting edge materials used to make a multi million dollar boat..

 

[Joe]

Not being a smart ass, but my guess would be having something to do with the millions of dollars of R&D and cutting edge materials used to make a multi million dollar boat..

I would disagree. If you read RichH's comment........ he's essentially talking about the cut of the sail. Laminated sails stretch much less than dacron.... so the sail keeps its shape longer.

However, dacron or laminate..... racing cut or cruising... fresh sails are going to allow you much finer trimming options.

I don't want to be a smart ass either, (hard not to be sometimes, I know) but... if you've never experienced the effect of NEW sails you'll always be guessing.

 

[Sam Salter]

Just to second what Joe said about new sails:
I bought a new set of main and 135% (Dacron) sails for my C&C 26 3 seasons ago. Before that, I suspect they were the original 1977 sails!
A totally different boat. Points higher; heels less; picks up quicker; much easier to trim; less backwinding of the main; etc. etc..
New sails are the single most worthwhile investment you can make for your boat - bar none!
(Self tailers are the next!!!)
sam

 

[Joe]

New sails are the single most worthwhile investment you can make for your boat - bar none!
(Self tailers are the next!!!)
sam

New sails are bitchen'....... Unfortunately, I've learned to live without self tailing winches....

 

[alexco38]

You can also get your sail maker to "re-cut" your sail to be more racing-cut. i.e. take the stretch out.

I am not saying you can make old sail into racing sail. Just give it a bit better performance and extend the life.

Nothing beats a new set of sail. Only money.

 

[RichH]

New sail are 'bitchin' ... thats why the top racers with unlimited checkbooks usually throw away their sails after about only a ~100 hours (or less) of usage.

 

[FastOlson]

Blame it on... Racing? Whoa

Some red herrings keep showing up again and again and... again... schools of them.... in lots of threads that start out like this one.
1) Racing per se has NOTHING to do how a production sailboat sail is designed. Nothing. Nada. Zip.
1) a. Any (!) boat is a racing boat when that boat enters a race.

2) Stock boats often (nearly always) have inexpensive dacron sails provided to them, that when new, that are rigidly budgeted to the lowest bidder, no matter whose logo is on the sail.
2) a. A major sailmaker will not go quite as cheap on those production boat sails as a discounter will, as they have more to lose if the sails lose shape too rapidly. So a North or UK logo on that new boat is indeed worth a bit more.

3) At the lower and even mid level of the production sailboat market, customers are very short sighted about the need to pay actual $ for good sails.
3) a. These same customers would balk at getting an obviously-underpowered 10 hp engine in their new 30 footer instead of a 20 hp , even to save a few bucs, ---- they do understand the need for power when motoring.
Irony abounds!

4) Thanks to decent software for the last 15 or more years, most all sailmakers can and usually do design an efficient sail, when it's new. When new, any production Blivit 26 can win a race, depending on crew.

5) Because of #4, most production sailboats actually will sail up to their designer's specs for about a year of normal sailing, sometimes less depending on abuse of the sails.

6) Because buyers are shortsightedly "thrifty", after about 5 years, the original owner and/or at least one or two subsequent owners will refuse to even consider that their original dacron sails have become grossly inefficient and are almost impossible to sheet or shape to make the boat sail above about 50% of it's potential.

7) and perhaps a consequense of #6, the majority of owners, after the first 5 or 10 years will insist that any fore-n-aft sail that is mostly white, attached at the usual places to their boat, and with no large tears, is JUST FINE. Period.

8) And..... when asked why their boat goes so slowly and heels so darned much (and scares the stuffing out of new crew or family) , will become perturbed and start complaining that "speed is for those Racers, and they don't care because they are..... Cruisers!"

And no, this rant will not change the world much.
Rationalization is built-in to our mental processes.
Yup. Mine too!


Still, sometimes someone just has to throw down a red flag on the field. "Fifteen yards for abuse of sails". "No First Down."



Carry on. As you were.

 

[justsomeguy]

Good rant!

 

[Sublime]

8) And..... when asked why their boat goes so slowly and heels so darned much (and scares the stuffing out of new crew or family) , will become perturbed and start complaining that "speed is for those Racers, and they don't care because they are..... Cruisers!"

And no, this rant will not change the world much.
Rationalization is built-in to our mental processes.
Yup. Mine too!


Still, sometimes someone just has to throw down a red flag on the field. "Fifteen yards for abuse of sails". "No First Down."



Carry on. As you were.

:neutral:






















Right.

So I have nice crispy sails on my boat (the "stock" sails, used twice before I got the boat otherwise stored indoors). I still wouldn't be able to haul my jib in so tight it nearly touches the car nor could I put the boom amid ships and get much forward movement.

I was just curious. Calme te

 

[FastOlson]

:neutral:
Right.

So I have nice crispy sails on my boat (the "stock" sails, used twice before I got the boat otherwise stored indoors). I still wouldn't be able to haul my jib in so tight it nearly touches the car nor could I put the boom amid ships and get much forward movement.

I was just curious. Calme te

Well, it gets back to your own boat and its inherent capabilities. Some boats are designed to point very very close to the wind and others not so much. The "slower" ones may have many other desirable features that contradict designing for good sailing efficiency, however.

For instance we used to have a 34 foot Danish daysailer/overnight in our club. It was about 6 feet wide and looked like a flush deck "meter boat". One of the best looking boats in our area. Inside was only sitting head room...
I believe that he could hold a 30 degree angle to the wind! My boat is a more common beam/length ratio at 10' 10" by 34', and I can hold onto about a 37 to 40 degree angle with not too much trouble. My main has pretty good shape and our jib is new this season (and sheets very close).
I can sail over the top of quite a few other boats... and then there some that do the same to me. My best guess (kind of a "SWAG") is that your H-26 has a much wider sheeting angle, and, that your boat is relatively wide for its length, and, that your hull might not be stiff enough along with the rigging, to really set up the head stay tight.

Then there's the other side of the "foils" comparison ---- the part that's underwater. My boat has a 6' draft, with an eliptical lead fin keel and an eliptical rudder.

We have always owned what are often called "performance cruisers" and once upon a time were often called cruiser/racers. We really like having a full cruising interior with great speed on the outside. But that's just us.
Here's a pix of us from a couple of weeks ago, courtesy of a friend who by chance was out for a sail and had a camera with him. That is a 95% jib, sheeted just inside the shrouds. Doin' about 7 kts to weather in about 12 kts of breeze.
Note that the main is not on center, but down just a bit to balance the helm.
This week we got 'er up to 7.3 kts in 17 kts of wind with that jib and one reef in the main.
The vertical battens make a huge difference in a tall narrow jib like this. Wish I had thought of this a decade ago!
Fair winds,

 

[Sam Salter]

Sublime,
I was sailing on a 260 last weekend.
There are a few things that could be better - no traveller; no jib cars or track; no cunningham; no backstay to tension.
That said, we could get the boom right up close to the centre line and most (not all) of the tell tales were flying.
It was going well and we had a great sail - nobody passed us - always a good sign.
It's all relative. Any day out on the water is a good day!
sam

 

[Todd Smith]

Warning, I am an engineer

The reason that some boats can sail to windward well and others can not, is DRAG.

DRAG = the force that acts in the direction of the apparent wind on the rig or flow of water over the hull.

LIFT = the force at right angles to that flow. This produces the forward drive of the rig and the resitance to leeway in the hull and keel.

I will refrain from diagrams, but I will state that the angle that a boat can sail to windward is determined mainly by the best ratio of LIFT to DRAG that her hull and rig can achieve. I will also state, that for a given hull, there is a limit to how well she can sail to windward, no matter how well the rig is refined.

So, to get to the point, for a given hull and keel and rig, there is a limit to how close to the wind the boat can sail. Being able to trim the sails in tighter than that limit, will NOT make the boat sail faster, or closer to the wind.

RichH's points about good sails and about sail design are completely correct, I just want to point out that they achieve the results because they reduce the DRAG on the rig.

The hull and keel of a high performance also produce less drag, mainly by having a deep(er) keel that produces less drag while counteracting the sideways force causing leeway.

BTW, cleaning the bottom is the cheapest way to get better performance.

To re-iterate, given the design of your hull, keel and rig, there will be a best angle that you can sail to windward and that will determine the tightest angle that the sails can be effectively trimmed. Trimming tighter than this will be counterproductive.

Thanks for your indulgence of this engineering speel.
Todd

 

[RobertLangdirect]

For example: . . . .

'nuf said!

 

[shemandr]

"The WWII British Spitfire elliptical wing was the first modern attempt to closely imitate 'bird wings' including the 'tip' section --- was a major success in increased aerodynamic efficiency"

That is why I made the foils on my centerboard boat look as much like a spitfire wing as possible.
When I was buying a new main I asked the sailmaker if the increase in efficiency of the sail caused by shortening the cord length and increasing the roach (making the sail look like a Spitfire wing) could make up for the loss in sail area. It's been said elsewhere that the flow is normally attached for only the first 20% of the chord length - if you're lucky. The rest is drag. Never got a good response and wasn't willing to bet a couple of thousand on it. What do our engineers think?

 

[FastOlson]

'nuf said!

Beautiful picture. Lookin' Good!!!

That's a "magazine cover" shot.

 

[DancingDays]

We recently had the opportunity to take a professional racer on board our Beneteau 31 for a wednesday beer can race. He trimmed the boom to center (and sometimes a hair higher) in 8 to 10 kts. We pointed _much_ better than usual, and still kept good speed for the conditions. We went from our usual near-last finish to 2nd place, although much of that was due to his down-wind expertise.

I wonder how much of this goes back to the loose vs fixed footed sail discussion? Ours is loose footed.

 

[Don Guillette]

I don't think it makes any difference between loose or bolt rope. What made the difference was your friend knew what he was doing.

I used to watch the Congressional Cup boats race in Long Beach, Ca. I was very interested in the match up between the loose and the bolt rope. Know what the outcome was? Neither had an advantage. Sometime one won and the next time the other boat won and only by a hair.

 

[FastOlson]

I don't think it makes any difference between loose or bolt rope. What made the difference was your friend knew what he was doing.

I used to watch the Congressional Cup boats race in Long Beach, Ca. I was very interested in the match up between the loose and the bolt rope. Know what the outcome was? Neither had an advantage. Sometime one won and the next time the other boat won and only by a hair.

I used to race a lot. Eventually I won often, too. But that was long ago.

Boat prep is very important. Sail trim is just as important. But more than that, you have to be going in the right direction more often than your competitors are!
And yes, all that learnin' is very useful when you are out cruising and need to find the most efficient way to your destination.

Due to the fast-learning environment on the race course, I still say that every (!) new sailor should race their boat at least two full seasons. Keep it friendly, focus on correcting your errors, and pay attention. Ask advice and listen to it. Get together with the others in your class or group and ask questions about what you can do to catch 'em. Good racers LOVE to have better competition, and mentoring the newer sailors is the best way to do that.

It's the fastest way by FAR to become proficient at handling your own boat under sail, and you will use that knowledge all the time for many decades.

Fair winds!