Which is more efficient, main or jib?

[sandy stone]

Originally Posted by hamburking

your best configuration relies on the slot effect of having the jib accelerate the wind over the lee side of the main

This is an unfortunate myth that was believed (and taught to all beginners) for decades. It wasn't until the 1970's that wind tunnel tests showed that air flowing through the slot actually decelerates. The perceived benefit of the slot was shown to be a consequence of the jib & main working together, the jib helping the airflow to stay attached to the lee side if the main, and the main deflecting the incoming airflow so that the jib is sailing in a permanent 'lift'.

Relating to the OP, it seems to me there was a maxi boat back in the '70's rigged as a ketch with substantially equal masts, and jibs on both masts. Sort of two sloop rigs on the same boat. Can't recall the name.

[sandy stone]

I think it might have been Equation, designed by Britton Chance.

[markpierce]

Originally Posted by darylat8750

... Off the wind the old gaff schooners would be quite competitive with the modern rigs. And they look so cool.

Yes they are.

[Scotty Kiwi]

Originally Posted by reed1v

depends on size of jib, cut of the main, point of sail, sea conditions, and strength of the winds. Also what kind of boat are you talking about. For us with a heavy blue water ketch, we used all our sail inventory as conditions changed.

The jib normally gives drive while the main gives direction, with the mizzen giving stability. Hard on the wind the mizzen is useless; direct downwind everything but the jib are more or less useless(assuming you changed to a 160 or more cut jib. In between, they all add something.

In a blow(45+ knots), then jib+mizzen, beyond 55knots then just the staysail(inner jib) and reefed mizzen. Hurricane conditions then either nothing or a tri sail off the mainmast to keep steady.

No wind or very little wind, go with very light jib.Or if you are motoring, then put up all three sails since they do help conserve fuel and will add about a knot to the boat. Hope that helps.

This seems about right to me, based on my time with a heavy blue water ketch.

But in general, as you take sail off, I reckon the Genoa was in general the most effective sail, by far.

Also in 5 to 9 knots reach, with everything up, I'd add a big mizzen staysail, (except I don't think it really was a staysail as it was around 140%, so maybe it was actually a mizzen Genoa??). In those airs, that sail would increase speed from 3 - 4 knots to 5 to 6 knots. Would the 2 knot increase make that the most effective sail at that point of sailing? Nope, because with a mizzen Genoa? on its own nothing much would happen. It was about the sails all working together.

So the answer is still if you had to pick one, it'd would be Genoa.

[Laughing Buddha]

Years ago, Ted Bett designed the So-Do-It. An a fram rig with single sail - roller furling jib. Saw one race in lte 90's in Long Beach. Was pretty quick up wind - but really smoked tacking downwind. Study plans here:
Boat plan SDI study

Makes we want one.

[knockabout]

most boats are designed to sail with both to keep the boat balanced / for perfect trim they would need to be equal though with care you can sail with either headsail or main on their own / on most boats the main on it's own will point higher / that doesn't make the main more efficient it's position is further back on the boat and naturally causing the boat to round to windward thus needing the jib to balance the boat

[StuM]

ISTM that most of the responders here didn't actually read the OP's question.

The question is about replacing the main on a ketch with a mizzen jib, so that you are carrying two jibs in line astern, not about the efficiency of using different single sails

[peter57]

Originally Posted by UNCIVILIZED

How do you define a junk rig as being efficient? Low cost maybe, but not efficient. Especially when compared with the Bermudan rig, in it's many variations.
Speciically, I'd love to see the Polars for a boat fitted with a junk rig, as compared to those of a Bermudan rigged sistership or cousin. And yes, this is coming from a genuine, unflinching, Pete & Annie Hill fan. Since about 1990. Meaning their junk rigged dory, Badger.

There's always been a strong temptation to build a similar boat myself. But then logic kicks in, & grabs me by the neck. Firmly telling me to tilt at a different windmill.

A Junk sail is efficient. Efficient to ease the amount of work for the controller (sailor) and tension of the crew. Annie Hill would know that is about all there good for though in sail efficiency.Pro; Dropping and raising panels downwind with ease. They last much longer ect, ect. Con; but do not point.

There are efficient Junk type sails, it is that you have not seen them. Complicated to make but easy to trim and change camber and do point well.

[david knowles]

one hand washes the other

[zeehag]

seems to me that a mizzen jib would be a yankee--i have been tossing that idea around of late with my rig.
my main is smaller than original, my 14 ft (at foot) mizzen both adds kts and stabilization to the rig and boat, genoa drives and steers.
i am also considering an inner headsail, self tending, no kneebreaker. so far, the inner headsail is the only thing i am definite on gaining.
may end up with a spinnaker and sock, as well.
might be able to handle light airs after these changes...

as for the mizzen yankee vs mainsail question--each sail does a different job and works best in different winds. rig for it--then experiment is only way you know what your boat will do under each.
i will know how mine behaves after i rig and try.

[charliehows]

well a jib instead of a main on my boat would be a much smaller sail given most ketches have a considerably shorter mizzen mast. On a schooner with a shorter fore mast it might be a reasonable idea.

[FranklinGray]

Originally Posted by StuM

ISTM that most of the responders here didn't actually read the OP's question.

The question is about replacing the main on a ketch with a mizzen jib, so that you are carrying two jibs in line astern, not about the efficiency of using different single sails

Exactly. I am sure the OP has the question because of boats that are for sale out there with a mizzen jib instead of a main. The boat has a Mizzen jib and a stay sail of equal size on a schooner with a 130 Genoa. One boat has a mizzen main but another doesn't. Odd.

So, the OP didn't get a good answer but it seems there are two options:

1) slot on main = greater
2) no mast to disturb the wind = greater.

You would think that because 99.9% of ketches are with a main instead of a mizzen jib, that there would be test results backing it up as the most efficient sail plan. Or is it just because most ketches were made a long time ago and the 'myth' of the slot ruled the day?