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Old 20-02-2016, 18:53   #1
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Sailing upwind - 1 board or 2?

Hi is there a rule of thumb about how much or how many boards to use in various upwind conditions? More board is more lift but also more wetted surface drag at low speed. It seems there would be a rigorous mathematical approach to this problem that no doubt has already been solved...
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Old 20-02-2016, 19:03   #2
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Re: Sailing upwind - 1 board or 2?

The mathematics of drag are of little use when actually sailing. Try thinking of vector forces and directions.

Your boards will primarily oppose any lateral force vector acting on your boat. (Aka leeway)

Try one or try many. Watch your sideslip and forward motion. The best choice will be obvious.

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Old 20-02-2016, 19:12   #3
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Re: Sailing upwind - 1 board or 2?

Thanks that is interesting. Yes unfortunately the wind conditions here are usually too gusty to make the results of even sail trim changes obvious. I imagine many others have already made the required observations however and can report the results.
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Old 21-02-2016, 03:53   #4
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Re: Sailing upwind - 1 board or 2?

Depends on the boat. I have pretty big boards, and typically run one all the way down at high speed.
When racing, you'd assign a crewman to switch boards each tack.

Two boards at less than 5 knots boat speed.

Having the boards partially down messes up my balance (CLR) when going upwind.
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Old 21-02-2016, 04:57   #5
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Re: Sailing upwind - 1 board or 2?

I agree with Paxfish when he says it depends on the boat. On our Pdq 36 we race with one board (lee) and tack them. When we cruise it I use both but only lowthered to the point where they're flush with the deck. This configuration doesn't affect the handling on the boat

I have not figured it out on our Outremer 45 yet. The boards seem small so I have been running both. I would be happy to hear from other owners on this subject, especially regarding how far to lower the boards
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Old 21-02-2016, 09:15   #6
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Re: Sailing upwind - 1 board or 2?

OMG I am left with no boards to push up/down

I just hope that those having boards are not the same ones complaining about the management of running stays...:-)
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Old 21-02-2016, 11:01   #7
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Re: Sailing upwind - 1 board or 2?

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OMG I am left with no boards to push up/down

I just hope that those having boards are not the same ones complaining about the management of running stays...:-)
I very much doubt it, there are no multis that I am aware in the cruising, even high performance cruising world that have boards and running backstays.
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Old 21-02-2016, 19:31   #8
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Re: Sailing upwind - 1 board or 2?

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I very much doubt it, there are no multis that I am aware in the cruising, even high performance cruising world that have boards and running backstays.
I'm not sure about other brands but my Outremer 45 has both dagger boards and running backs
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Old 21-02-2016, 20:19   #9
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Re: Sailing upwind - 1 board or 2?

If you're at all concerned about safety, sail with only the weather board down. That way, if you get overpowered enough, before you can ease a sheet. Then said board will lift free from the water (along with that hull). And in theory, you'll slide off to leeward, sans going inverted.
As there wont be a board in the water in that hull, restraining your transverse movement.

By which time, hopefully someone will have already have eased the sheets, so as to prevent the necessity of a "trouser check".
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Old 21-02-2016, 20:30   #10
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Re: Sailing upwind - 1 board or 2?

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If you're at all concerned about safety, sail with only the weather board down. That way, if you get overpowered enough, before you can ease a sheet. Then said board will lift free from the water (along with that hull). And in theory, you'll slide off to leeward, sans going inverted.
As there wont be a board in the water in that hull, restraining your transverse movement.

By which time, hopefully someone will have already have eased the sheets, so as to prevent the necessity of a "trouser check".
That is exactly how I sail into high winds. Have found pinching up to depower a useful tactic in an unexpected gust as well.
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Old 21-02-2016, 21:17   #11
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Re: Sailing upwind - 1 board or 2?

Racing my Tornado Cat (20 feet and really light weight) use only the lee board. I think the two boards may not be exactly parallel so they fight one-another as well as greater drag. Since the Tornado is usually flying a hull, the windward board is useless most of the time. I have also found that the board must be down to balance the forces. Helm disappears when the board is dropped, speed up, leeway much reduced. I often find the lessons on a small boat hold on larger versions as well although I like the idea of using a windward board as a safety measure in higher wind.
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Old 22-02-2016, 03:18   #12
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Re: Sailing upwind - 1 board or 2?

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I often find the lessons on a small boat hold on larger versions as well although I like the idea of using a windward board as a safety measure in higher wind.
Yeah, Not much to be gained having the crew out on a trapese on a 45.
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Old 22-02-2016, 20:45   #13
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Re: Sailing upwind - 1 board or 2?

Light winds, maximum board. As wind builds we use less. At about reefing time we'd have about 50% board down.
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Old 23-02-2016, 04:09   #14
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Re: Sailing upwind - 1 board or 2?

Racing - Leeward Board Down and tack your boards.
Cruising - Both down about half
Storm - Windward Board Down.
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Old 23-02-2016, 04:37   #15
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Re: Sailing upwind - 1 board or 2?

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Racing - Leeward Board Down and tack your boards.
Cruising - Both down about half
Storm - Windward Board Down.
I doubt all the way down in storm. One needs to consider possibility of breaking board, which will cause some dramas for sure.

I still have copy of catana manual here that explains that clearly.
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