America's Cup thoughts

[John Vigor]

Spoken like a true capitalist, Zeida! How much did Grant Dalton charge to put his arm around you?

Cheers,

John V.

[Zeida]

A nice sweet smile Plus I have been following many of the excellent Kiwi sailors for many years, reading about them in magazines and the web and it was a pleasure to meet the entire crews of some of the Volvo round the world boats when they stopped in Miami in 2002.!

FWIW, here I am again, with Lisa McDonald, the American born Captain/Skipper of the Nautor Challenge "Amer Sports II" with an all-female crew of top rated world women sailors. Grant Dalton was the Captain/Skipper of "Amer Sports I". He was kind enough to invite me to step aboard the incredible racing yacht and pose with me for the pictures and sign my autograph. It was a great day.

[img]http://www.imagestation.com/picture/sra ... 1e7a1b.jpg[/img]
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[John Vigor]

Terrific pictures, Zeida. You certainly do move in high circles as far as yacht racing is concerned.

One thing about the Versus coverage of the Louis Vuitton Cup intrigued me, and maybe you have some comments.

I noticed from the aerial shots that the America's Cup boats pin in their mainsails so hard on the beat that is looks as if the boom is actually lined exactly up fore and aft. I always though a bit of outward angle was necessary to get some forward push out of the sail, but those guys seems to depend on the fullness of the mainsail itself.

I've never seen booms pinned in so tightly on the beat. This obviously enables them to point very high and it seems they somehow don't lose speed either. There's some magic at work here, something to do with the narrowness of the boats and their underwater appendages, I guess. I don't think it works with Cape Dorys.

Cheers,

John V.

[wingreen]

Even though the boom is lined up fore-aft, the sail stretches out toward the leeward, just enough to produce a forward vector.

I once sailed all day w/ my boom hooked up to the backstay (the main was reefed). I was so busy leaving port that I forgot to unhook it. The winds were pretty strong, so the boom would swing in & out a little, but I never noticed until we were coming back to port, since I had it hauled in all day anyway.

In hindsight I noticed a little performance effect while under sail, but at the time I attributed it to the winds and the seas.

I noticed from the aerial shots that the America's Cup boats pin in their mainsails so hard on the beat that is looks as if the boom is actually lined exactly up fore and aft. I always though a bit of outward angle was necessary to get some forward push out of the sail, but those guys seems to depend on the fullness of the mainsail itself.

[Oswego John]

Wingreen, John and all,

I think that the individual design for the cut of the sail will allow for power push when drastically pinned in. Until now, I never gave it much thought.

When Wingreen mentioned that the boom was pinned in by being clipped to the back stay, the first thought I had was that while under way, especially during gusts, the mast would be subjected to an unusual strain.

In my head, I'm trying to envisage the trigonometry of the standing rigging and the upper mast shape. I realize that the length of the fore stay is set. When the aft end of the boom pulls the aft stay sideways like a bow string, what happens?

If the aft stay is bowed at all, it becomes shortened. Would this bow affect the upper mast column? In turn, would this create more mast rake? Would extra mast rake allow the mainsail to bellow out more than normal and create power push?

If something puts a belly in the aft stay, as the song states, "somewhere, somehow, something's gotta give in." Is the butt of the mast driven into the cuddy roof? If so, the fore stay would shorten, accordingly.

Finally, is wondering and worrying about this worth a three Excedrin headache? The solution is.....

Don't forget to unhook your boom supports, and for those with inboards, don't forget to lock your props.....

.....and all will be right with the world.
O J
PS: Zeida, nice pictures.

[wingreen]

Don't forget to unhook your boom supports, and for those with inboards, don't forget to lock your props.....

.....and all will be right with the world.
O J
PS: Zeida, nice pictures.

I haven't forgotten since, John. If you want to think more about trig & vectors, consider that the mainsheet was probably also producing a downward force on the end of the boom, which in turn would have a component force along the backstay. I think it may have lessened somewhat the forces you were considering, but I haven't tried to work it all out in my head. The main was somewhat more billowed out that day. I have never heard of this "power push" that you refer to.

[Oswego John]

Wingreen,

Thanks for replying.

Apologies first:

Ohmygosh, I did say bellow. Should have said billow, sorry.

As for "power push" I suppose that it is a local colloquialism that I've heard mentioned since Hector was a puppy. John V alluded to something that is similar to my wording.

[Quote John V]
"I always though a bit of outward angle was necessary to get some forward push out of the sail, but those guys seems to depend on the fullness of the mainsail itself.

I've never seen booms pinned in so tightly on the beat. This obviously enables them to point very high and it seems they somehow don't lose speed either."

I vividly remember one of my early mentors attempting to explain how a sailboat derives power to push the boat ahead, from wind that is blowing from the side.

He said to take a fresh melon seed (that is still slippery) and place it between my thumb and forefinger, blunt end facing forward. Next, I should squeeze my fingers together to apply force or pressure to the angled sides of the seed.

I feel that tha act of squeezing the fingers may be translated to the sidewards force that pushes the seed. forward. That's the best analogy (read alibi) that I can come up with on short notice.

I guarantee that at three o'clock in the morning, I'll roll over in bed and think of a proper explanation of the true meaning of the phrase "power push".

Not that I understand a lot of it, but I have always been somewhat intrigued by the subtle mysteries of what makes sailing into the wind possible.

O J

[wingreen]

I have never had a complicated understanding of it, John. I have always believed that as long as you can trim the sail so the wind can catch a little bit of its aft side that it will make the whole thing go forward.

Here's how I think it works...

Since sails billow, it is possible that even though the boom is pinned directly fore-aft, there are still large areas of the sail that are curved so that they act as if the boom were let out a little.

[Zeida]

AC racing yachts did keep their booms in very tight. Actually, the commentators mentioned that fact. The shape of their mainsails have all to do with it. If you notice, they have bigger roaches than average, with full length battens, plus now the square tops give them even more wind-catching advantage. Especially, TNZ did race with its boom tighter than LR on all windward beats. Also they have the narrowest of all boats and that possibly affects the way they trim their main.

How did you like their keeping their staysails up with their spinnakers? And keeping the poles in the same side while gybing? And the way they pulled in those spinnys into the sewers, as if they had some type of motorized system down there.. I'm sure they do! All in all, it is fascinating to me to watch the crew work on those sleek machines. I am now saving $$$ to buy a new main next year!

John V. funny that you say "would not work in Cape Dorys" because I find that on my 33, I normally pull the boom in as hard as I can when upwind... but maybe because my poor main is old and tired and baggy, and to get some sort of shape in her, i need to keep the boom as tight and hard as possible.

[wingreen]

How did you like their keeping their staysails up with their spinnakers? And keeping the poles in the same side while gybing? And the way they pulled in those spinnys into the sewers, as if they had some type of motorized system down there.. I'm sure they do! All in all, it is fascinating to me to watch the crew work on those sleek machines. I am now saving $$$ to buy a new main next year!

I didn't get to watch the live action, zeida, but I was following the races on the Internet, and I noticed in the photo galleries how tight they kept their mains. I'd love to spend a day or two with a crew like that - it would be worth at least a year of experience at my current skill level.

[Al Levesque]

I didn't see it mentioned but most sailboats don't go straight ahead. For the keel to get lift the boat ends up slightly angled. A boom sheeted amidships is also angled by that same amount. I am sure that in such finely designed and tuned boats the angle is not what I am accustomed to but it helps just the same.