Lateen Sail Question, I’m Sure There’s a Reason

[blackislandben]

New poster here with a question.

I sail small boats and favor the simplicity of the lateen rig. I am currently converting a boat to a lateen rig and wondered why I have never seen one with the spars mounted to the mast at the apex(or very front of the yard/boom). This would certainly eliminate the “bad side of the mast” issue. Would be easy to do. What am I missing here. Please excuse any misuse of terminology, feel free to correct as necessary.

 

[walmsleyc]

maybe a sketch of what your thinking?

The boom part would/might be fine, but the yard part of a lanteen rig gets its support (in order to get proper sail shape) from being supported, part way along, by the mast.

I suppose what your suggesting is just a gaff rigged boat, with a "zero" length luff?

Chris

 

[dlochner]

Most likely it is to balance the sail plan and make it easier to control the main sail. The sail area forward of the mast, although small, exerts a force to counter the force of the section behind the mast.

On larger boats rudders are often designed so that part of the rudder is forward of the rudder post for the same reason. It makes it easier to steer.

 

[capta]

Though I don't have a lot of first hand experience with the lateen rig, I'm pretty sure it is an important part of its design that there is the correct amount of sail in front of the mast for balance. It is even possible that this can be shifted for the point of sail one intends to be on.

 

[blackislandben]

Thanks so much for the reply!

The yard is drawn up into a yoke/gallows on the mast. The mast is in an outer tube socket, sits on a sealed bearing and is free to rotate with the sail. The yoke stays the yard. If you think about it when a lateen is on the good side of the mast is unsupported except by the halyard. The yoke will stay it in both directions. Disregard the squiggle . Please excuse the crude drawing but you get the idea I’m hoping.

 

[dlochner]

Thanks so much for the reply!

The yard is drawn up into a yoke/gallows on the mast. The mast is in an outer tube socket, sits on a sealed bearing and is free to rotate with the sail. The yoke stays the yard. If you think about it when a lateen is on the good side of the mast is unsupported except by the halyard. The yoke will stay it in both directions. Disregard the squiggle . Please excuse the crude drawing but you get the idea I’m hoping.

You'll need Popeye arms to control the main. Too much pressure on the sail.

The sail area in front of the mast counter acts the pressure on the aft end of the sail.

 

[blackislandben]

Thanks for all your replies and thoughts.

The yard/boom only extend 12” past the mast. I don’t see a lot of area there to balance the forces. Here’s a pic of the sail a 66sf Sunfish. (not my boat) On my rig the boom is level leaving little past the mast. Plan to use at least a 2:1 purchase. Main Idea is to eliminate bad side of the mast. I sail long runs on the return it’s all bad mast. I have over come this by having a mast eye on both sides of the boom. I just pull the mast and swap sides. Bad thing is the yard won’t fully come back next to the boom and easily fit in the sail bag.

 

[dlochner]

The yard/boom only extend 12” past the mast. I don’t see a lot of area there to balance the forces.

It doesn't take much.

The sail area forward of the mast is only part of the equation. The other part is the lever arm. The goal is to reduce the force on the mainsheet not eliminate it.

Moving the sail aft will also increase the force on the lower boom. The boom may not be able to handle the force, that could cause the boom to fail.

It will be a challenge to keep the upper gaff close to the mast. The forces will tend to push it away from the mast which will degrade the upwind performance of the sail.

Good luck.

 

[rgranger]

Something similar to what you are describing already exists. I forget what they call this rig but you essentially turn the yard into a mast by pulling it straight up like this....

A real advantage I see to this sort of rig is if you live in a place where getting under a fixed bridge is an issue.

 

[Joe]

I'm not getting it. Why would you want to move the center of effort so far back... you'll be fighting the tiller whenever you get gusted. If you don't like the way the latteen rig is set up, then convert to a cat rig. A gaff rig, might even allow for an additional staysail above the yard... but heck... now you're getting complicated. Your mainsail power will be in the back half of the sail, so what air is disturbed when the yard is to windward... I can't really see how it will affect performance.
I've owned both Lasers (a cat rig) and a sunfish (lateen) and I prefer the cat rig for performance. The lateen's advantage, imho.. is easier to handle and balance due the rig's low aspect ratio.
Bottom line........ make the change... if you like it.....cool.... if not... convert it back to original. It's that simple. there's no right or wrong.

 

[blackislandben]

Thanks y’all for all the input. I know there is a massive amount of knowledge and experience within the forum
and I appreciate your opinions.
I like to experiment with ideas. I can make easily reversible mods to the rig to check the concept.

Joe
The boat involved actually needs the center of effort moved back due to some previous mods that moved the mast forward. The boat is an on going experiment of sorts in its own right. I probably should not have gotten involved with it but the price was right(free), and it was just too darned cute to let it get cut up.

 

[All U Get]

The book I have on my shelf is OFFSHORE YACHTS desirable and undesirable characteristics by John Rousmaniere. It has more answers than you have questions but the ones that stick out would be spin on axis and righting moment. Since it’s off the shelf, I’ll be reading it later.

Is this a small boat?

 

[dlochner]

After thinking about the proposed modification to your rig, there is one huge issue that hasn't been addressed, sail twist.

All sails twist. The upper leach will fall off to leeward. This is expected and because the wind at the top of the mast is different from the wind at the bottom a desired characteristic as it improves sail performance. Like all good things, too much twist is bad and impairs sail performance.

On a lateen rig, the location of the mast connection serves 2 purposes, as noted earlier it provides a small section of sail ahead of the mast which helps to balance the rig and reduce pressure on the main sheet and makes steering easier.

The second and probably more important function is to stabilize the upper section of the sail so that it does not twist. The mast, the upper and lower spars form a triangle this prevents the upper spar from twisting more than the aluminum pole will twist (on a small boat, that's not much). The upper and lower spars will be in the same vertical plane. In the proposed modification, this triangle will not exist which will allow the top spar to fall off to leeward significantly reducing sail efficiency. The line (topping lift) used to support the upper spar will only keep the upper and lower spars in the same vertical plane when head to wind or in irons.

The design proposed by @rgranger over comes this limitation by drawing the upper spar close to the mast, essentially making it an extension of the mast. Depending on how it is rigged, the amount of twist can be controlled by how close to the mast the upper spar is drawn. This design is very similar to the standard triangular mainsail most of us use. The lateen sail you have will need modification to work with this design. The tack will need to be close to 90° and the lateen sail is probably closer to 60°. Using the lateen sail in this configuration will move the center of effort much higher and cause the boat to be more tender.

 

[blackislandben]

It’s kinda small, 17ft. It’s one of those things that evolves from a set of unforeseen circumstances.
The poor thing had been stripped of all rig and abandoned behind an abandoned house. I after a few years ran down the owner and was given it. The only logical thing to do with it was to make it a motor launch, which it has proven to be excellent at.
I also love land sailing and built a great sailing land yacht. Unfortunately as the beach became more crowded each year wizzing around tourists at 25+ began to be frowned upon. So I reluctantly dismantled the sailer.
So lm left with a complete but way too small sail rig. What to do, combine them into a motorsailer.
In a 12-15mph breeze it does sail leisurely along which my wife loves. Case closed, done deal, it is what it is.
Im now about firming up the rig. Hoping to get a Neil Pryde 83sf sail. That’s is as far as it goes. Was just considering the modded rig maybe to improve performance a tad?

So you can see how it’s evolved into an esoteric assemblage. Things gotta go where they gotta go now.
Its odd but does work reasonably well. It does have its quirks, but most quirky things are interesting.

Before and now evolving pics And my deceased landsailer.

 

[dlochner]

She cleaned up nice!

The sail is too small for the boat. But I suspect you knew that already.

Keep your eye out for a boat of similar size that has a bad hull and good mast and boom. That will give you the best performance.

 

[blackislandben]

dlochner, thanks for that insight! Will just leave as is and motorsail leisurely around the tidal creeks to the beach. As they say it’s not the destination but the trip.

Thanks everyone for all your input!!

 

[PaulK]

Sliding Gunter rig. Been around a while.

The Sliding Gunter: A versatile Traditional Sailing Rig

 

[dlochner]

Sliding Gunter rig. Been around a while.

The Sliding Gunter: A versatile Traditional Sailing Rig

That's the name for the sail plan @rgranger mentioned. Thanks for finding the name.

 

[blackislandben]

Had a W W Potter 14 with that rig. Was a near little boat. Like the hard chines sailed pretty flat.

 

[shemandr]

An excellent article. I will chew on that for a while. The dory I built had a sprit sail arrangement. I have to say the snotter was not as adjustable as said because I would have to go to forward in the boat while the main would be flailing out of control. It wasn't safe. I never got the hang of the snotter/sprit arrangement. But I didn't have instruction. Years later a friend told me of the old time expression, "Cheese down the snotter." We got a kick out of that. Traditional rigs are a hoot.