Which is more efficient, main or jib?

[DavidLGCrawford]

Given two sails of identical size, which would be more efficient, a jib with an angled leading edge or a main behind a mast?

Imagine a ketch. Typically, from the bow to stern, you would have:
jib, main mast, mainsail (on boom), mizzen mast, mizzen sail.
But what if you did:
jib, main mast, jib 2, mizzen mast, mizzen sail.

Assuming the mainsail and "jib 2" where identical size, would there be a difference?

[StuM]

My first thought is that you won't get the slot effect with two jibs that you would with jib+main.

[FSMike]

Go find someone with a staysail ketch and ask them what they think; or, look up an owner of one of Chris White's new Mastfurl rigs (I think that's what they're called).

[UNCIVILIZED]

If you're adept at searching, I'm fairly certain that this one's been discussed before. Though beyond a certain point the discussion's entirely academic, even when building a boat from a blank sheet. Well, unless one cares little about resale.

[darylat8750]

It sounds like you may be describing a stay sail schooner. I believe typically not as efficient as a modern double head sail cutter type rig. I have lusted after a Cherubini Yacht 48 for years... Cherubini Yachts 48 Staysail Schooner

[Stumble]

It gets very complicated very quickly and there are no pat answers. Aspect ratio, drag distribution, sail shape, all play a part.

The only short answer is that if you restrict only sail area the best use of it is a single high aspect main ala A-Class Catamarans. If you restrict mast height and total sail area then you get the largest main possible with the excess used for the jib.

But if you only restrict mast height then you tend to get the largest main possible and the largest jib possible.

[darylat8750]

It seems to me that unless racing you should only limit power available for a given amount of healing moment. Off the wind the old gaff schooners would be quite competitive with the modern rigs. And they look so cool.

[dlymn]

Originally Posted by darylat8750

It seems to me that unless racing you should only limit power available for a given amount of healing moment. Off the wind the old gaff schooners would be quite competitive with the modern rigs. And they look so cool.

Do you lust after Maltese Falcon?

It's not a whim that the overwhelming majority of cruising and racing boats are bermudan sloops with a gennaker (sort of) Ease of management, minimal crew, reliability and more importantly most efficient transformation of the wind at all angles IMHO
On OP, wind angle and speed will determine choice of sail or if you use one or both sails. One hopes that the boat designer created the best combination of boat and sails. The sail size and shape is a product of contemporary thinking about sail physics and hull design. Even so, sailors will add a genoa as fast as you can blink if they think that the boat can sail faster in some conditions. Any racer will tell you that the size and shape of the sail is dependent on sailing conditions. That's why they spend so much effort changing them.

[El Pinguino]

My money... on most points of sailing... would be on the jib.

I think I read somewhere, Marchaj perhaps, that the crab claw was the most efficient of all sails.

Dunno why you wouldn't get good slot effect with two jibs..

[Cap Erict3]

My old hank on deck sweeping 150 Genny pushed my tub better alone than the main until a close reach. Now that I normally fly a Yankee and staysail on furlers, my main provides the most. Sheeting angle is going to be better on the main. IMHO

[DavidLGCrawford]

Originally Posted by StuM

My first thought is that you won't get the slot effect with two jibs that you would with jib+main.

You would, it would just be between jib 2 and the mizzen.

[DavidLGCrawford]

Originally Posted by FSMike

Go find someone with a staysail ketch and ask them what they think; or, look up an owner of one of Chris White's new Mastfurl rigs (I think that's what they're called).

Oh, actually it's Mastfoil, and yes, that is exactly what I was thinking. And he does it for all the reasons I was thinking about (ease of handling roller jibs over mainsail, etc).

[DavidLGCrawford]

Originally Posted by darylat8750

It sounds like you may be describing a stay sail schooner. I believe typically not as efficient as a modern double head sail cutter type rig. I have lusted after a Cherubini Yacht 48 for years... Cherubini Yachts 48 Staysail Schooner

Wow, that's a gorgeous boat. I can certainly see why you lusted one.

Pretty much just what I was thinking but interestingly they put jib 2 on a boom. Not sure why they would do that... it would limit you to a 100%, while without a boom you could go 120 or more. Still, I'm not an engineer so what do I know!

[DavidLGCrawford]

Originally Posted by Stumble

It gets very complicated very quickly and there are no pat answers. Aspect ratio, drag distribution, sail shape, all play a part.

The only short answer is that if you restrict only sail area the best use of it is a single high aspect main ala A-Class Catamarans. If you restrict mast height and total sail area then you get the largest main possible with the excess used for the jib.

But if you only restrict mast height then you tend to get the largest main possible and the largest jib possible.

I wasn't really saying we needed to restrict sail size, I only specified they needed to be the same area so we could compare the two more equally. Pointless saying compare a jib over a main if someone then says their jib is x sq ft and the main is y sq ft and x is greater/less than y so one is better.

My only real restriction would be mast height. Thinking of getting the most sail, while being easy to control single handed, with a boat that can still go under bridges when needed. This would be for cruising, not racing.

[DavidLGCrawford]

Originally Posted by Cap Erict3

My old hank on deck sweeping 150 Genny pushed my tub better alone than the main until a close reach. Now that I normally fly a Yankee and staysail on furlers, my main provides the most. Sheeting angle is going to be better on the main. IMHO

On our cat the 120 genny seems to be so much better than the main, and it is a lot easier to work with. Though both of those points could be due to my lack of experience... time will tell.