Ketch vs sloop

[Pilot90442]

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?

[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

[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.

[nwdiver]

Amel is now building a 50 cutter, buy one of each and test out the theory........

[Dockhead]

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.

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.

[zeehag]

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.

[geoleo]

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

Its not necessilarily true but it is generally true!

[HankOnthewater]

Originally Posted by nwdiver

Amel is now building a 50 cutter, buy one of each and test out the theory........

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?

[nwdiver]

I guess a truer test would be the Fisher 34 in ketch and sloop.....

[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.

[Dockhead]

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.

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.

[UNCIVILIZED]

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