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01-10-2017, 09:19
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#1
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Registered User
Join Date: Jul 2017
Posts: 9
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Ketch vs sloop
Tha Admiral and i were watch a youtube video of the Amel 55. She noticed something and asked a question I'm not sure how to answer.
It was sailing along very nicely and wasn't heeled over much. It was on a beam reach. Since a ketch has 2 shorter masts my logical mind says the mast has a shorter arm so it wouldn't heel as much as the taller mast of a sloop. Am I thinking correctly?
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01-10-2017, 09:25
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#2
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Moderator Emeritus
Join Date: Sep 2007
Location: Eastern Tennessee
Boat: Research vessel for a university, retired now.
Posts: 10,406
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Re: Ketch vs sloop
It's true that the shorter the mast and the less sail area that there will be less heeling given all the other factors remain the same. The sum of both sails center of effort will be partially related to how much your boat heels at a given wind velocity. The other major factor will be your boats righting arm at a given angle of inclination. The amount of righting arm relates to the vessels center of buoyancy, its center of gravity and its beam.
So to answer your question, it's not necessarily true that a ketch will heel less than a sloop. There are other factors which make that determination as well.
http://righting-moment.html
__________________
David
Life begins where land ends.
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01-10-2017, 10:15
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#3
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Registered User
Join Date: Jun 2014
Location: Up the mast, looking for clean wind.
Boat: Currently Shopping, & Heavily in LUST!
Posts: 5,629
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Re: Ketch vs sloop
Yes, all other things being equal, a ketch which has the same amount of sail area as a sloop will heel less, since the sailplan's center of effort (CE) will be lower. This assumes the same hull, & keel, etc.
__________________
The Uncommon Thing, The Hard Thing, The Important Thing (in Life): Making Promises to Yourself, And Keeping Them.
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01-10-2017, 10:32
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#4
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Registered User
Join Date: Aug 2011
Location: Vancouver, BC
Boat: C&C Landfall 38
Posts: 821
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Re: Ketch vs sloop
Amel is now building a 50 cutter, buy one of each and test out the theory........
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01-10-2017, 10:41
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#5
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Moderator
Join Date: Mar 2009
Location: Denmark (Winter), Helsinki (Summer); Cruising the Baltic Sea this year!
Boat: Cutter-Rigged Moody 54
Posts: 33,865
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Re: Ketch vs sloop
Quote:
Originally Posted by UNCIVILIZED
Yes, all other things being equal, a ketch which has the same amount of sail area as a sloop will heel less, since the sailplan's center of effort (CE) will be lower. This assumes the same hull, & keel, etc.
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Yes. But all other things are not typically equal, because boat designers design in a certain righting moment as a fundamental design parameter. So a ketch will normally have correspondingly less ballast in order to maintain the same righting moment.
This might not be the case for some small ketches which are really just sloops with a vestigial mizzen. When there's a big difference in the size of main and mizzen, it doesn't make much difference. The mizzen of the Amel 54 is only about 16% of the total sail area, so it's not a big deal. If you chopped off the mizzen and increased the rest of the sail plan by 16%, without changing the ballast, you wouldn't notice a huge difference.
I like ketches, but in my opinion they start to really make sense only when the masts are pretty far apart, and the mizzen forms a significant part of the sail plan.
__________________
"You sea! I resign myself to you also . . . . I guess what you mean,
I behold from the beach your crooked inviting fingers,
I believe you refuse to go back without feeling of me;
We must have a turn together . . . . I undress . . . . hurry me out of sight of the land,
Cushion me soft . . . . rock me in billowy drowse,
Dash me with amorous wet . . . . I can repay you."
Walt Whitman
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01-10-2017, 10:43
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#6
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cat herder, extreme blacksheep
Join Date: Jul 2008
Location: furycame alley , tropics, mexico for now
Boat: 1976 FORMOSA yankee clipper 41
Posts: 18,967
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Re: Ketch vs sloop
i sailed and owned sloops allmy life(since 1955, when i was a 7 yr old kid.) until i lived with a guy fro a few months on a ketch. that perked my interest in ketches. another friend built a cargo schooner from what was in his yard. yes wood with fg overlay. good boat.. he has put many thousands of miles under her keel, including 2 round trips thru panama canal .
i bought this ketch and continued to cruise opb, including a sloop. ok. so when we watched a ketch handle our same weather only much easier i was convinced that my choice was the best one. bashing in seas and against winds as opposed to sliding thru same in a ketch under jib n jigger--what a beautiful sight. yup.
and ketch is a much easier boat to sola than is a sloop, especially in heavy winds and weather. the 60plus kt chubasco would have overpowered my ericson 35, but my formosa took the bone in her teeth and flew nicely under jib n jigger. tracks with impressive stability.
before you go out buying your cruising boat, sail everything to see what you like best.
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01-10-2017, 17:35
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#7
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Registered User
Join Date: Feb 2006
Posts: 2,771
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Re: Ketch vs sloop
Quote:
Originally Posted by David M
It's true that the shorter the mast and the less sail area that there will be less heeling given all the other factors remain the same. The sum of both sails center of effort will be partially related to how much your boat heels at a given wind velocity. The other major factor will be your boats righting arm at a given angle of inclination. The amount of righting arm relates to the vessels center of buoyancy, its center of gravity and its beam.
So to answer your question, it's not necessarily true that a ketch will heel less than a sloop. There are other factors which make that determination as well.
http://righting-moment.html
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Its not necessilarily true but it is generally true!
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01-10-2017, 18:57
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#8
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registered user
Join Date: Dec 2012
Location: back in West Australia
Boat: plastic production boat, suitable for deep blue water ;)
Posts: 1,096
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Re: Ketch vs sloop
Quote:
Originally Posted by nwdiver
Amel is now building a 50 cutter, buy one of each and test out the theory........
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Yes, Amel has already launched this sloop (I think staysail is an option) earlier this year here http://amel50.com/en/
Pilot, when you follow Nwdiver's advise, you need crew/skipper for the other boat. Can I volunteer?
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02-10-2017, 10:21
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#9
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Registered User
Join Date: Aug 2011
Location: Vancouver, BC
Boat: C&C Landfall 38
Posts: 821
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Re: Ketch vs sloop
I guess a truer test would be the Fisher 34 in ketch and sloop.....
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02-10-2017, 10:26
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#10
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Registered User
Join Date: Jun 2014
Location: Up the mast, looking for clean wind.
Boat: Currently Shopping, & Heavily in LUST!
Posts: 5,629
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Re: Ketch vs sloop
With the exception of sailing purely upwind, or deep downwind angles, the masts on a ketch can be set surprisingly close together, & yield quite good performance. As has been done by quite a few ketches in the Transpac over the years. Including on boats with large mizzens.
One such example I know of has about 1' between the end of her main boom & her mizzen mast. This on a 48' boat.
__________________
The Uncommon Thing, The Hard Thing, The Important Thing (in Life): Making Promises to Yourself, And Keeping Them.
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02-10-2017, 10:35
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#11
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Moderator
Join Date: Mar 2009
Location: Denmark (Winter), Helsinki (Summer); Cruising the Baltic Sea this year!
Boat: Cutter-Rigged Moody 54
Posts: 33,865
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Re: Ketch vs sloop
Quote:
Originally Posted by UNCIVILIZED
With the exception of sailing purely upwind, or deep downwind angles, the masts on a ketch can be set surprisingly close together, & yield quite good performance. As has been done by quite a few ketches in the Transpac over the years. Including on boats with large mizzens.
One such example I know of has about 1' between the end of her main boom & her mizzen mast. This on a 48' boat.
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Of course, reaching is all good on any ketch.
And even gooder than good, for all the cool reaching sails you can rig between the masts -- fishermen, mizzen staysails, etc. etc. -- love it!!
The whole issue is upwind, and here the distance between the masts is crucially important. Read what A64 wrote about biplanes and the aerodynamics of this. I don't think it's the distance from the boom end to the mizzen -- it's the distance between the masts, which is important.
__________________
"You sea! I resign myself to you also . . . . I guess what you mean,
I behold from the beach your crooked inviting fingers,
I believe you refuse to go back without feeling of me;
We must have a turn together . . . . I undress . . . . hurry me out of sight of the land,
Cushion me soft . . . . rock me in billowy drowse,
Dash me with amorous wet . . . . I can repay you."
Walt Whitman
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02-10-2017, 11:15
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#12
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Registered User
Join Date: Jun 2014
Location: Up the mast, looking for clean wind.
Boat: Currently Shopping, & Heavily in LUST!
Posts: 5,629
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Re: Ketch vs sloop
All I know is that I'd go for a ride/crew on Mari Cha IV any day of the week. Several times most days
__________________
The Uncommon Thing, The Hard Thing, The Important Thing (in Life): Making Promises to Yourself, And Keeping Them.
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