Sloop vs Ketch upwind

[double u]

swaged new standing rigging the other day for a nauticat 38 ketch: no way this maze of wires with it's windage, weight & costs can offer any advantages over a single-stick-rig on a boat this size

[Dockhead]

Originally Posted by wedivebc

While perusing my daily "boat porn" sites I cam across an ad for a 41' sloop where they stated the sloop was easier to handle and can sail closer to the wind than the similarly appointed ketch.
In my limited sailing experience that doesn't make sense to me that a ketch with the same keel and hull configuration can't sail closer than a sloop.
What am I missing?

All other things being equal, a sloop rigged boat will indeed sail closer to the wind, and faster, than a ketch.

That's because:

1. A split rig with the same sail area has more windage, which is the arch enemy of sailing upwind;

2. When you are close to the wind, or sailing DDW or nearly so, the sails on one mast will be working in the turbulence made by the sails on the other mast; and

3. Aspect ratio of the sails will usually be less, which makes the sails less efficient when they are operating in lift (like when you're going upwind).


That being said, ketches have a lot of other advantages, and I LOVE them, personally.

They were popular because before good winches, deck hardware, and furling gear, it helped a lot to make a boat practically sailable to break up the sail plan into smaller sails.

Now that's not so important.

But the flexibility of the sail plan is a huge plus (same advantage of a cutter over a sloop, but more so). You get to use cool sails like fishermen and mizzen staysails. The mizzen is a great place for mounting different hardware. AND -- they just look beautiful. On a reach, they work great, allowing you to spread out more canvas with a lower center of effort. And the sails are cheaper and last longer, if they are smaller.

The disadvantages are reduced, if the masts are further apart from each other (that is, on a larger boat), and the advantages greater if the mizzen is not too small.

The main reason why they are hardly made any more is simply because they are much more expensive to build.


I consider a ketch rig for my next boat, which will be big enough (about 65 feet) to get the masts a reasonable distance apart from each other.

[Mozzie]

Originally Posted by Dockhead

They were popular because before good winches, deck hardware, and furling gear, it helped a lot to make a boat practically sailable to break up the sail plan into smaller sails.

Now that's not so important....

The main reason why they are hardly made any more is simply because they are much more expensive to build.

I would imagine it is a confluence of better deck hardware, greater simplicity, lower cost and furlers being useful for reducing sail area as opposed to changing sails, plus maybe some other factors.

A number of relatively small technological factors can combine to make something obsolete.

It's like biplanes became obsolete due to a combination of thicker (and therefore stronger) airfoils, higher power to weight ratio engines, availability of longer runways, use of stronger materials, improved streamlining etc.

[billknny]

Originally Posted by Mozzie

If my understanding of aircraft aerodynamics transfers over to sailing, two or more sails would act like slotted flaps, which are the things on the back ends of wings that pilots deploy on landing and takeoff to improve lift at low speed.

Slotted flaps not only increase lift, but also reduce the lift to drag ratio. That is, they increase drag more than they increase lift. The more slots the more lift and drag.

Moreover, lift to drag ratio determines the glide ratio of an aircraft, which is how closely it can be held to horizontal flight (analogous to how close a boat can be held to the eye of the wind). If a pilot tries to fly a plane at more than its best lift to drag ratio, it will stall and fall out of the sky, kinda like a boat 'stalls' and becomes dead in the water when you pull it too close to the wind.

So the extra sail on a ketch acts like an extra slot, which makes the 'lift to drag ratio' worse. However, when a ketch is sailing more off the wind, and the sails are not pulled so tight the greater lift and even the greater drag act in the ketch's advantage.

I think that is an excellent summary!

Sailing upwind is all about maximizing lift over drag. As you turn more and more downwind, drag becomes more and more helpful, until you are dead downwind, when pretty much everything useful happening is drag.

Ketches also have the advantage that once they crack off a bit they can fly a mizzen staysail and really increase sail area for a significant boost.

It's not the subject of the OP, but optimizing lift to drag of the keel and rudder is just as important in getting upwind. Without the lift of the keel, the boat would go sideways (at best!) The difference is that underwater, all drag is bad all the time because it is always directed 180 deg to the forward motion of the boat.

[Mozzie]

Originally Posted by billknny

It's not the subject of the OP, but optimizing lift to drag of the keel and rudder is just as important in getting upwind. Without the lift of the keel, the boat would go sideways (at best!) The difference is that underwater, all drag is bad all the time because it is always directed 180 deg to the forward motion of the boat.

Oh yeah... I hadn't thought about the keel. The drag of the keel and would play a part as well. A poor lift to drag ratio would reduce the critical angle beyond which it is not possible to point into the wind.

A long high aspect ratio keel would have a high 'lift to drag' ratio, whereas a short stubby one would have a lower lift to drag ratio. A hull without a keel like a traditional square rigged sailing ship would produce 'lift' but with a terrible lift to drag ratio.

In aerospace, there are things called lifting bodies - wingless aircraft which none the less produce lift. Even capsules like the Apollo command module produce lift and can be flown towards a target.

Also I guess the winged keel on Australia II was a an end plate or winglet.

This all has me intrigued. Are there equivalent terms for lift and drag for boats, or are the terms the same? Oh well it seems like I need some books.

[Pete7]

Originally Posted by DerekKelsall

With simple rotating mast systems, I believe in rotating for cruising and racing. Happy boating, Derek.

I believe you have had an interesting career and thank you for the contributions to the forum.

http://kelsall.com/TechnicalArticles/KCForTheRecord.pdf

[james247]

Originally Posted by wedivebc

While perusing my daily "boat porn" sites I cam across an ad for a 41' sloop where they stated the sloop was easier to handle and can sail closer to the wind than the similarly appointed ketch.
In my limited sailing experience that doesn't make sense to me that a ketch with the same keel and hull configuration can't sail closer than a sloop.
What am I missing?

There is no doubt that a sloop is generally faster than a ketch. I learned to sail a 1912 gaff rigged yall.
I have owned a 65 ft aluminium sloop go fast racer.
But to cruise I'd have the 53foot swan ketch everyday.
Easy to rig easy to sail. compare it to having two engines when berthing. There are so many variations in rig.
Lower mast heights. Less healing more comfort. You give up a bit in speed but you will get 200 miles everyday in the trades
No stress no aches no rush. Cook easier sleep easier. I could write a book on the benefits for cruising with a ketch rig.
The mizen should be proportionately tall. A 60 foot main mast with a 45 foot mizen. Lots of edges to gather power. Lighter sails and less mass could hoist the main without a winch other than halyard tension.
Like I said I could write a book.

[double u]

shorthanded & above a certain boatsize 2 masts make sense, at 38' not so much...

[billknny]

Originally Posted by Mozzie

Oh yeah... I hadn't thought about the keel. The drag of the keel and would play a part as well. A poor lift to drag ratio would reduce the critical angle beyond which it is not possible to point into the wind.

A long high aspect ratio keel would have a high 'lift to drag' ratio, whereas a short stubby one would have a lower lift to drag ratio. A hull without a keel like a traditional square rigged sailing ship would produce 'lift' but with a terrible lift to drag ratio.

In aerospace, there are things called lifting bodies - wingless aircraft which none the less produce lift. Even capsules like the Apollo command module produce lift and can be flown towards a target.

Also I guess the winged keel on Australia II was a an end plate or winglet.

This all has me intrigued. Are there equivalent terms for lift and drag for boats, or are the terms the same? Oh well it seems like I need some books.

This book is the classic text from 1987: http://amzn.to/2yzccOp

I think it is out of print, but still kicking around of course!

[billknny]

Originally Posted by Peregrine1983

Nice post. I agree.

Lots of ketches tend to be heavy cruisers - which of course won't sail as well to windward as a light sloop with a deep draft. In the "ketch vs sloop" argument you're often comparing the equivalent of a Toyota Land Cruiser to a BMW coupe.

And if you took all that "stuff" stuffed into the cruising ketch and (somehow) put it in the coupe, you'd have four blown tires and be rolling on the rims...

[billknny]

Originally Posted by UNCIVILIZED

Mast in front of sail = 0 drive from 15-25% of that sail's sail area. Main or Mizzen, when the wind is forward of the beam. The math ain't complicated. Plus of course you have close to double the drag, given 2 masts & sets of standing rigging.

Sloop vs. Ketch. If spreader lengths on the 2 boats are equal, then the sheeting angles on the sloop will be tighter, thus enabling you to sail closer to the wind, as the J component of the sheeting angle on the sloop's jib will be longer than the ketch's.

Sloop = Main (only) operating in jib's lee.
Ketch = Main operating in jib's lee, & mizzen in both jib & main's lee.

Sloop with a proper reefing setup = quick, easy reefing. From the cockpit should you so desire it. As opposed to having to reef 2 boomed sails.
And if you need to luff up in order to reef, you'll likely need to do so for longer with 2 boomed sails than with one.

Sloop reaching or downwind = 2 sails to trim vs. 3 or 4 with a ketch.

How many ketch's do you see with vangs? As without one sail shape will suffer at almost all wind angles.

Ketch = much smaller overlapping genoas or Code 0's. Ergo poorer performance.

Ketch = generally far less mainsail shaping controls available, & even less for the mizzen. Given that it has no permanent backstay, nor baby stays & headstays, or cutter stays, with which to control mast bend.

More difficult to mount a wind vane for self steering on a ketch, if at all. And if you do then sail area on the ketch may be further reduced. Especially as compared to a sloop.

Some of these are good valid points, some are over stated, others are wrong.

I have owned several ketches, and every one had vangs on the main and the mizzen. And the idea you can not fit a wind vane to a ketch is just plan WRONG. Look around the world's cruising grounds... there are ketches everywhere with windvanes.

A ketch typically does not have mast bending controls, true. But many cruising sloops do not either. So that's not a reasonable point of difference. That's more the difference between a high performance racing boat and a cruising boat.

Some of us actually consider having more sails to trim and adjust a BENEFIT because it lets us balance the boat a lot better. How many sloops can you sail hands off (no autopilot) on a beam reach???

The only problem with your post is that it lacks the balance a good ketch would have. Of course there are things a sloop is better at. You seem unwilling or unable to see there are things a ketch is better at.

If my plans were to sail upwind most of the time, I'd have a sloop. I happily wait a week and good far out of my way to sail downwind--because I can--so a ketch is perfect for ME. You need a different kind of boat than I do, and that is good for you, and for me!

[Peregrine1983]

Originally Posted by billknny

And if you took all that "stuff" stuffed into the cruising ketch and (somehow) put it in the coupe, you'd have four blown tires and be rolling on the rims...

Hah. I'll take the Land Cruiser most days of the week, but that's just me.

And you can absolutely mount a self-steering vane on a Pearson 424 ketch.

The real question is... can you mount a self-steering vane on a Land Cruiser.

[james247]

Originally Posted by StuM

All good points. Plus a sloop will generally have higher aspect sails = more efficient for the same sail area.

I generally agree with the comments with respect to older ketches but none are are a design failure of a modern ketch. My current boat is a sloop. Only because my requirements are now for a modern lighter boat built of carbon fibre and the lack of ketches built in such materials

[james247]

Originally Posted by billknny

Some of these are good valid points, some are over stated, others are wrong.



I have owned several ketches, and every one had vangs on the main and the mizzen. And the idea you can not fit a wind vane to a ketch is just plan WRONG. Look around the world's cruising grounds... there are ketches everywhere with windvanes.



A ketch typically does not have mast bending controls, true. But many cruising sloops do not either. So that's not a reasonable point of difference. That's more the difference between a high performance racing boat and a cruising boat.



Some of us actually consider having more sails to trim and adjust a BENEFIT because it lets us balance the boat a lot better. How many sloops can you sail hands off (no autopilot) on a beam reach???



The only problem with your post is that it lacks the balance a good ketch would have. Of course there are things a sloop is better at. You seem unwilling or unable to see there are things a ketch is better at.



If my plans were to sail upwind most of the time, I'd have a sloop. I happily wait a week and good far out of my way to sail downwind--because I can--so a ketch is perfect for ME. You need a different kind of boat than I do, and that is good for you, and for me!

Agreed if cruising to windward is ones goal then a sloop is appropriate . But as allllll cruisers agree every day to windward is a day in hell.
All sailing routes of the world are off the wind. It's all about comfort and efficient off wind sailing. But there are the days when we must win ground to a windward location and to sail at 40 degrees is a sad and wasted experience. 32 degrees is acceptable. But 22 degrees is fantastic

[svfinlandia]

Originally Posted by Kenomac

Amel is the only remaining manufacturer still offering a ketch along with their new Amel 50 which is sloop rigged.

Kenomac
I'm sure that there are still other yards building Ketch rigged boats - Nauticat for one.

Al, S/V Finlandia