Most Weatherly Schooner

I've been thinking about the schooner rig and its reputation for poor windward performance.

I have tried to come up with a theory for why this is so.

The best I could come up with is that the tip vortice of the fore sail spoils the effectiveness of the aft sail. And this is an issue mainly when sailing upwind.

To test this theory, I have dreamed up a class of schooner rigged dinghies. It has the following design limits:

1.) Max Hull Length = 4.0 m,
2.) Max Sail Area = 7.0 sm,
3.) Aft sail must make up at least 45% of the total Sail Area,
4.) Fore Sail must have at least half the area of the Aft Sail,
5.) Fore Mast must have at least 1 sail,
6.) There must be a sail between the Fore Mast and the Aft Mast,
7.) The Fore mast can be no taller than 90% as tall as the Aft Mast, and
8.) The Fore Mast must be stepped at least 0.25 Hull Length in front of the Aft Mast.

These 8 rules are to limit the size of the boats, their Sail Area, and to insure that they are really schooners.

I have come up with 3 rig design strategies to get the most Weatherly schooner.

1 a.) Use Bermudan sails,
b.) Rake the Fore Mast aft until its head nearly touches the Aft Mast, and
c.) Have no jib.

2 a.) Use Bermudan Sails,
b.) Make the Fore Sail a staysail, and
c.) have a jib.

3 a.) Use a Bermudan boomless Fore Sail,
b.) Place the Fore Mast as close to the Aft Mast as these rules allow,
c.) Have the Fore Sail overlap the Main Sail, and
d.) Have no jib.

Which of these three strategies is likely to produce the most Weatherly schhoner?

My guess is that Strategy 1 would be the winner

 

All three look like the worst possible setup for going upwind. If you want a development class why so many constraints.

 

Option 1 sounds like a sloop rig with extra steps.

 

Alternatively, it is the usually quite low aspect ratio of schooner rigs. If you had a main and two foresails of the same aspect ratio on the same hull, would there be any difference to a stereotypical schooner rig?

That seems to assume that a sloop is always the most close winded. Results from A-cats and C-cats suggest otherwise. Also, I think I read that you can make a schooner more close-winded by separating the sails as much as possible, which matches what I remember reading about biplane wings (Kang et al., 2009, Gap and stagger effects on biplane wings with end plates). Your strategy 1 reduces separation (stagger).

 

I invite you to re read my post.

My objective here is not to make the most Weatherly sailboat.

We know how to do that. Just use a tall Bermuda main and a deep fin keel.

A fractional sloop will go faster but maybe not point as well. But it's extra speed more than makes up for that. This is probably why just about every high-performance sailboat has a fractional sloop rig.

But what I'm looking for here is the most weatherly schooner.

So, in order to comply with my quest, the boat in question must have a schooner rig.

This is the reason for six of the eight rules I laid out. The first two are to limit the size of the hypothetical vessal.

The other six are to insure it is actually a schooner.

 

I suppose that would work.

I thought of having only a jib on the fore mast and having only a main on the aft mast, leaving a gap between them.

But I then added a rule that prohibited that. It stipulates that there must be a sail between the two masts.

It doesn't have to be bent to the fore mast. It can be a staysail hung from the aft mast. But, if it is such, the fore mast must have its own jib.

So, to get the separation you have in mind, and comply with all my rules, you can put the fore mast at the very bow of the boat, with a main only, and put the aft mast as far back as possible, with a main only as well.

This would likely work even better if both sails were actually high aspect ratio wings (which would still comply with my rules).

IIRC, Class-A cats had wings for sails, which were in effect single-sail boats. Or was that the Class-Cs?

 

That's exactly what it is.

But it complies with all my rules. It is still technically a schooner.

Some might call it a rule-beater, as it would be considered a schooner (and get a schooner rating handicap) while having much of the aerodynamics of a sloop.

 

Whether A and C Class cats are a suitable model for a 4m dinghy seems to be pretty arguable. Because they are stable, low-drag platforms they can have very high-aspect rigs and very flat sails that are at their best at higher apparent wind speed and closer angles. It's a lovely low-drag rig, but it's not necessarily the best for a 4m dinghy has much less stability and much higher drag. To poorly paraphrase Mark Drela, what matters is not the lift/drag characteristics of the rig, but the lift/drag characteristics of the entire boat. A low-drag/low power rig is not much use on a high-drag unstable hull, just as a high lift/high drag rig is not much use on a fast cat.

Look at the development dinghy classes that have the same sort of hull as your proposed boat. That means 12 Foot Skiffs, R Class dinghies from NZ, perhaps Renjolle, Australian NS14s and old '1960s Moths (the newer ones are not really comparable due to their high righting moment and very slender hulls). Several of those classes have tried cat rigs, and all of them (save the Moth where it's the only legal rig) have dumped them because the single-element rig doesn't generate enough lift and has too much heeling moment. The International Canoes have also tried and dumped cat rigs.

The most popular small schooner classes are now dead. The first was the US predecessor to the International Canoe. Uffa Fox proved that the sloop was faster, by using the foremast as a rigid forestay and sloping it back to meet the aft mast, therefore essentially creating a sloop.

The other popular small schooner was the Division 3 windsurfer class of the '80s. The later ones were round-bottomed like the Olympic Div 2 Lechner boards, and seriously quick around a triangle. The sailor at the front tried to lean the rig as far aft as possible, while the sailor at the back tried to lean the aft rig as far towards the bow as possible. I think the front sailor tried to keep the mast vertical, in the athwartships direction, while the aft sailor leaned his rig to windward. This created the maximum overlap, fore and aft, while keeping the slot wide.

Years ago, in response to a question of mine Tom Speer said that the true or effective aspect ratio of a rig was the height/length measurement of the whole rig, not the various elements. So a schooner is an inherently low aspect rig and therefore inherently slow to windward, compared to a sloop.

 

Why do you think simulating a sloop with headsail instead of keeping both masts parallel, would work better?

I grew up aboard a 56 foot three masted schooner designed by Clark Mills. She went to windward pretty well.
I was young, didn't know all that much about it, but my father who has sailed around the world in a J44 seemed to think she did pretty well.

Maybe not as well as a J44, but her 12 foot beam, 3/4 keel with 5' draft and three 46 foot Marconi sails served her well.

-Will

 

All three proposed rigs are inferior to the traditional designs. With modern materials it is possible to reduce windage and weight. I have re-read your post, and it states you have a theory to test. What is the theory and how do the proposed rules test it?

 

Filling the area between the masts with efficient sail has always been the biggest problem. Wishbone schooners seem to have been the best at doing this, but they are a tad fussy to live with on a daily basis. Gaffs are not quite as efficient as a pair of triangles, and you can't overlap the aft mast with a traditional fores'l gaff like you can with the wishbone's staysail (but loose-footed, overlapping gaff fores'ls were common on small working schooners in the US). Staysail plus gollywobbler is also very good (fisherman's rig). Particularly the ones that attach to the foremast with slugs or a jackstay.



But optimizing a schooner for windward performance only is a pretty silly. It's like optimizing a pick-up truck for street racing.

 

Good point.

The advantage may not have been all aerodynamics, or some of it may have been an indirect effect. Joining the two masts has some structural advantages, so they may have been thinner, lighter, and the foremast's mass would be closer to to the centre, reducing pitch inertia.

I will have to read that biplane paper again, it may deal only with 2D flow, minimising wingtip vortices. I have not the faintest idea why the spacing you describe turned out to be the best. It does suggest another configuration for sharpii2: mount the foremast with some slop, so that it always falls off to lee a bit.

My decidedly non-expert interpretation of a sloop is that near the deck, the downwash from the jib means the mainsail must be sheeted in more, but that the jib's wingtip vortex means the top of the main should twist off. On the whole, that means put more twist in the main than would be good for a unarig, which is a very good thing if you can't control twist that well anyway. So perhaps the sloop's reputation for upwind performance is partly a historic relic from times when sails and spars were made from weaker materials.

 

My theory is that the mast top vortices from the fore sail spoil much of the lift of the taller aft sail. And this happens mainly when the schooner is sailing upwind.

If this theory is correct, rig design strategy 1 should handily beat the other two upwind.

This is because the top vortice of the fore sail has no chance to form, because it is blocked by the aft sail.

Now that I think of it, I should have offered a 4th choice.

This one would have the aft sail as a stay sail and the jib as the fore sail.

Anyway, I am somewhat disappointed that no one voted on which of my three choices would be best for sailing to windward (that means better than the other two).

 

I don't buy his reasoning at all.

To show you why, let's do a little thought experiment.

First, we will start with a schooner that meets my eight rules.

And to keep it simple, we'll use triangular sails, with no roaches. And we will use no stay sails or jibs.

We'll keep the masts as close in height as my rules allow, so the fore mast will be 90% of the height of the aft one.

The foot of each sail will be half the length as its luff.

The fore sail would then have a luff of 3.62 m. It's foot would be 1.81m.

The aft sail's luff would be 3.86m and it's foot would be 1.93m. This will give us the 7.0sm allowed by my rules.

Now, let's suppose I want to make a similar boat but with a cat rig.

I want to keep the Heeling Arm within reason, so I choose a luff length that is which is an average of that of the old fore mast and aft mast.

This gives me a luff length of 3.75m.

Since I want this sail to be triangular like those on the schooner, the sail foot on this cat rig will be nearly 3.74m.

Now the foot is nearly as long as the luff.

Finally, let's suppose these two boats have the same hull design.

Now, which of these two would go to windward faster?

My bet is the cat rigged one will, despite its much lower aspect ratio, single sail.

What do you think?

 

You are comparing a cat rig to a poorly designed schooner rig. The options you posted are much worse than a typical schooner rig.