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Why have multiple sails downwind?

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Why do these Volvo boats all use multiple sails going downwind?

Is it because they are not really going downwind? I.E. with the apparent wind forward enough that one sail doesn't blanket the other?

If so, are all planing hulls sailed basically the same? With the jib open AND the asym?

 

m45338_13-00-170802-asv-asv-2820.jpg

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Also, these boats really like to be driven hard, like 25 degrees of heel, so more sail is better.

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5 minutes ago, Kenny Dumas said:

Also, these boats really like to be driven hard, like 25 degrees of heel, so more sail is better.

I guess that's a function of the hull shape? More wide = More Heel?

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8 minutes ago, SoFastSoSlow said:

I guess that's a function of the hull shape? More wide = More Heel?

From what I understand the VOR65 keel doesn't cant as much as other designs, like the VOR70 and others.  The reasoning behind that was to make the boats last longer due to decreased loads.  It worked, but the tradeoff is less speed and increased load on the crew working and living at a higher heel angle.

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14 minutes ago, glexpress said:

From what I understand the VOR65 keel doesn't cant as much as other designs, like the VOR70 and others.  The reasoning behind that was to make the boats last longer due to decreased loads.  It worked, but the tradeoff is less speed and increased load on the crew working and living at a higher heel angle.

That's my least favorite part of a sailboat to be honest... I know I know I'm not a REAL sailor :P

Movable interior ballast really needs to take off. Much simpler than canting anything... Fighters jets use it geez! (I don't mean JUST water ballast, but actual movable lead inside).

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7 minutes ago, SoFastSoSlow said:

That's my least favorite part of a sailboat to be honest... I know I know I'm not a REAL sailor :P

Movable interior ballast really needs to take off. Much simpler than canting anything... Fighters jets use it geez! (I don't mean JUST water ballast, but actual movable lead inside).

Water ballast doesn't offer as much righting movement as a canting keel.  Each system has pros and cons, but in the end these systems are for racing boats so teams are going to push boats hard to win, which means more heel.

 

Edit:  Worth mentioning that the VOR65 you pictured also has interior water ballast system.

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Rigid ballast in hull is ancient technology. Been ships have been using them as long as humanity has been building wooden ships. 

Think about leverage for a moment. The  further the keel weight is from the waterline, the less weight needed to create the same righting moment. 

I remember when the 747 carried depleted uranium, but that was a function of correcting for poor center of gravity and not some technological highlight. 

Not really sure what you're referring to in fighter jets. Mass dampers are used to deal with harmonics and vibration but not some magical mass that improves power/mass ratio. 

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