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Old 20-08-2009, 13:05   #1
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Sailing to Windward

It seems to be accepted as a truism that a ketch will not sail to windward as well as a sloop. Why is that? If two vessels have identical hulls and sail areas, why is a ketch inherently inferior in this area?
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Old 20-08-2009, 13:52   #2
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It seems to be accepted as a truism that a ketch will not sail to windward as well as a sloop. Why is that? If two vessels have identical hulls and sail areas, why is a ketch inherently inferior in this area?
I am definitely not an expert on ketch rigs, however, when I used to race at a fleet with a go-fast ketch rig boat, these guys dropped their mizzen sail in the upwind legs and hoisted it back up during reaches and runs... I would guess it has to do with the drag the mizzen may cause.

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Old 20-08-2009, 13:54   #3
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It seems to be accepted as a truism that a ketch will not sail to windward as well as a sloop. Why is that? If two vessels have identical hulls and sail areas, why is a ketch inherently inferior in this area?
Windward ability is related in part to aspect ratio. The taller and narrower the sail the bigger the lift to drag ratio, important when most of the power developed is sideways. Low aspect sails make better barn doors for pushing when stalled off the wind.

Another point is that each sail aft operates in the header created by the sail in front of it, which makes the mizzen less effective for upwind work. Some accounts I've read for some boats is that they don't even use the mizzen for upwind work.

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Old 20-08-2009, 14:03   #4
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I understand your second point. As to the first, Is there any reason why a ketch could not have a tall, narrow mainsail?

Also, I think we should distinguish between speed and pointing ability. Is there any reason why a sloop can inherently point higher than a ketch?

A boat that can point higher doesn't have to go as fast to be just as effective sailing to windward--yes?
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Old 20-08-2009, 14:13   #5
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I understand your second point. As to the first, Is there any reason why a ketch could not have a tall, narrow mainsail?
I guess you can, but you stipulated equal sail areas for the two boats. You will have a high aspect jib and main, but with less sail area than the sloop since some area has to be in the mizzen. You can make the mizzen high aspect also, but it's still in headed bad air.

Another reason for the ketch was to increase shroud angles with shorter masts to reduce compression loads.

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Old 20-08-2009, 14:20   #6
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It seems to be accepted as a truism that a ketch will not sail to windward as well as a sloop. Why is that? If two vessels have identical hulls and sail areas, why is a ketch inherently inferior in this area?
I believe the accepted " truism " is that Gentlemen Never Sail to Weather. Who wants to go bouncy bouncy for days at a time? Down here they call it "the thorny path"...for a reason.
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Old 20-08-2009, 14:21   #7
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The Straw that Broke the Ketch's Keel

I'm sure those who really know will push me to the side, but several factors come to mind off-hand. In no particular order of effect:
  • Two masts means more weight and more drag
  • Ketchs have lower aspect-ratio sails (shorter masts) which don't point as well as sails with longer luffs & shorter feet
  • The ketch is an old sailplan, used to keep heeling moment under control in the days of internal stone ballast (shorter masts) and to divide up sail area before mechanical winches replaced back-power. They have traditionally been associated with hull types that are less efficient: full keels, deep V draft, high surface area (higher drag). So part of the ketch-rigged boat's pointing limitation is likely hidden under the surface.
  • If the sail area really is equal to the sloop, it means that you've either reduced mast height (mentioned above) or shifted canvas from the foretriangle to a mizzen by either using a smaller headsail (maybe higher cut foot) or losing it by going with a fractional rig, so you lose headsail drive, which compromises pointing ability.
  • If one is hard on the wind, by the time the wind gets to the mizzen, it's pretty turbulent from being torn up by two other sails. Maybe not a lot, but more than on a yawl with the mizzen more abaft.

When I say "several factors come to mind off-hand", I should admit that I only really thought of a couple of these factors: the rest is fortification from a very comprehensive post by Jeff Halpern here.
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Old 20-08-2009, 14:22   #8
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Do the shorter masts adversely affect pointing ability?

As to speed, once you reach hull speed, that's it, at least to windward where you can't surf. So in a stiff breeze, with two identical hulls, wouldn't pointing ability be the determining factor?
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Old 20-08-2009, 14:25   #9
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"But would the shorter masts adversely affect pointing ability?"

Would guess this is similar to a glider's wing being long and thin for great pointing ability (high glide ratio).
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Old 20-08-2009, 14:42   #10
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My Rhodes Reliant is a yawl. Back in the 60's the CCA rules for the Newport-Bermuda race seems to have generated a number of split rigs in the 40ft LOA range, Hinckley B40, S&S Finisterre, Block Island 40. Back then, before the weather patterns changed, the rhumb line for that race was commonly a beam reach, at which split rigs are at home. It allowed one to carry a mizzen staysail, the prettiest sail of all IMHO. These boats, in my experience, had the same height mainmast, with shorter mainbooms. My Reliant is built that way.
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Old 20-08-2009, 14:57   #11
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Well folks, I don't know what brand of ketches you are referring to but the go-fast racing ketch I remember from the 80s was (now I remember ) a Skye 50 (or similar) ketch and the main mast height was definitely not what I would consider "short" Google it and have look - this boat went to weather like a freight train!...

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Old 20-08-2009, 15:38   #12
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My Rhodes Reliant is a yawl. Back in the 60's the CCA rules for the Newport-Bermuda race seems to have generated a number of split rigs in the 40ft LOA range, Hinckley B40, S&S Finisterre, Block Island 40. Back then, before the weather patterns changed, the rhumb line for that race was commonly a beam reach, at which split rigs are at home. It allowed one to carry a mizzen staysail, the prettiest sail of all IMHO. These boats, in my experience, had the same height mainmast, with shorter mainbooms. My Reliant is built that way.
Ours, which was built for that race, has quite a long boom (22'). There was a rating advantage for the yawl rig (and the ability to fly a mizzen stays'l). I've found that the mizzen draws fine on a beat, but it is "way the heck back there". For a ketch with the mizzen forward, the disturbed airflow from the main doesn't give the mizzen lift if pointed too high.
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Old 21-08-2009, 07:12   #13
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The windward ability of a sloop over a ketch or a yawl is do to aspect ratio.For us it is very important to have a boat that sails efficiently upwind. Last Sunday coming home from Canada was a 50 mile beat ~ 6 hours. We always seem to have to go upwind, tonight we are going to the islands and it is predicted to be upwind with 25 knots in 6 footers.
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Old 21-08-2009, 08:13   #14
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Wow Joli, I'm envious - 50 miles to windward in 6 hours is pretty impressive!

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Old 21-08-2009, 10:16   #15
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...way the heck back there...
This is another important point. A mizzen can strongly affect the center of effort of the sail plan, and on the beat will theoretically increase weather helm pretty dramatically at the time you want the least drag from rudder, etc.

High aspect-ratio is like tall sails - the greatest amount of drive is in the forward third of the sail, just as the greatest amount of drive is in the upper third of the sail. When sail area is limited, high aspect ratio is vital. Of course, when sail area is unlimited then it's just so much added expense since it requires higher stresses, loads, etc.
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