Balance

[Roger Long]

I met with Paul Rollins and the client yesterday. We decided that the off-center board was too much of an impact on arrangement and seating. The new Yawldory centerboard is pretty far forward in the full down position but we're going to stick with it.

The board is in the right position for sailing with the main alone and, for the relaxed way this boat is going to be sailed, the mizzen is apt to be furled when helm angle and force balance is a significant issue. The board can also simply be brought back about half way with little loss in area.

However, for people who think they might like to sail this boat harder (at least in their minds) and want perfect balance, I throw out this idea:

http://www.rogerlongboats.com/images/YawldoryDaggerboard.gif

It would be mostly plugged with a short false board but fiddling with the aft board should produce perfect balance and a boat that will steer herself under most conditions.

[johngsandusky]

I like it, as long as the daggerboard can be stowed when not in use.

[Thorne]

In my humble opinion this is WAY too busy -- and I thought you were going for an overall trad look and feel?

One huge advantage to a CB and kickup rudder is that the boat can hit sand or mud shallows or even be sailed up on the beach in a pinch - all without damage.

Adding a daggerboard like that reduces that essential simplicity, puts another hole in the bottom of the boat, takes up space right where folks will want to sit, and adds to the cost and complexity of the entire design.

If you want more LR aft, the trad solution would be to build a kickup rudder that has a larger foil/blade -- or for a more modern solution use Mik Storer's push-through rudder design.
http://www.storerboatplans.com/GIS/GoatJohnsBoat1.jpg

[Brian Palmer]

I think that dagger board in the rear will probably present too much area to be overcome by the rudder. The boat will track well, but could be hard to turn and tack.

I think just pulling the main center board back when needed to shift the CLR when using the mizzen would be enough.

You could also add a small jib if needed to balance the mizzen.

Lifting the aft daggerboard will also interfere with the end of the tiller.

Brian

[Paul Pless]

I agree with Thorne on the daggerboard.

Would a alternate larger or higher aspect rudder serve the same purpose for those wanting more sailing performance?

[Hwyl]

Aarghh, I hate agreeing with Thorne.

[Roger Long]

Aarghh, I hate agreeing with Thorne.

I agree with everybody and there is no intention to put the daggerboard in the boat being built. I'm just throwing the idea out there. The boat wouldn't be very maneuverable with the board. It's something you would only put in for long legs where you wanted minimal steering effort and maximum tracking. I doubt it would be found useful enough to carry the daggerboard around inside the boat most of the time.

[Thorne]

Aarghh, I hate agreeing with Thorne.

LOL!

C'mon guys, I've been gradually hammered into shape (well, sorta) here on the Forum, and try to present as little of my ignorance in public as possible. Not smarter by any means, but perhaps craftier??

Possibly my greatest value is illustrating the Catheraine Aird quote:

"If you can't be a good example...
Then you'll just have to be a horrible warning."

[David G]

LOL!

Possibly my greatest value is illustrating the Catheraine Aird quote:

"If you can't be a good example...
Then you'll just have to be a horrible warning."

Yes, 'tis what Twins do best. All my nieces/nephews tell me I do a marvelous job of it. And... since you're the smarter twin, you must be even better at it :p

And - the rear daggerboard notion strikes me as simply Goofy. However, someone more technically savvy would actually have to do the calcs and modeling, and tank testing and prototyping and all to prove it absolutely. Have at it, gentlemen.

[johnw]

If this is about performance, don't add more wetted surface, especially in a way that will make her slow in stays. Add more sail in the form of a small jib. Tension along the head of a sprit sail tends to give you some luff tension on a jib. This goes away when you're reaching, which gives the jib a deeper shape on the reach. I've also found that cat ketches seem to pick up speed after a tack better with the aid of even a small jib.

[Roger Long]

the rear daggerboard notion strikes me as simply Goofy.

It might well be on this boat but tandem boards is a concept that hasn't been worked with nearly enough. There's more to it than just being able to fiddle with the balance. A foil near the ends of a vessel that is swept sideways through the water when the vessel yaws will resist these forces more than one near the middle that goes through less of an arc or is just being twisted in the water. Splitting the lateral plane into two separated parts increases the yaw resistance dramatically.

When you want directional stability, pull up the forward board. When you want maneuverability, pull up the aft board. You'll then have a tremendous moment arm on the rudder.

I've often thought my ideal long distance cruiser would be a large version of something like the yawldory with one board way forward and one way aft. The trunks would be away from the prime accommodations space. The boat would heave to wonderfully with mizzen set and just forward board down. Shoal draft, beachable. Running before the wind with a small jib and just the aft board down should be equally impressive.

Spaulding Dunbar of Cape Cod was a great proponent of boats of this type. He told me about being in one of his long, skinny, tandem board vessels in a Gulf Stream storm with both boards up watching her just skidding sideways down the seas just ahead of the breaking crests. Having watched my double paddle canoe do the same thing in wind driven breakers (not the same thing as waves in shoaling water) I can easily believe his account. If you think of my canoe as a big model it's a good test of a 40 ish boat in a major offshore storm.

[Todd Bradshaw]

The added daggerboard doesn't really trip my trigger either. However, I am continually impressed with the effectiveness of a fairy small and beachable drop-down skeg on some of my kayaks when I want to increase tracking power in the aft end of the hulls.

[Steve Paskey]

I'm fascinated by the opinions on this. Folks think it's too much trouble, too much expense, etc. ... yet some of the same folks would think nothing of adding a small jib.

Maybe I just have irrational feelings about jibs, but in theory I like this MUCH better than adding one of those annoying little triangular sails at the front of the boat.

[johnw]

I'm fascinated by the opinions on this. Folks think it's too much trouble, too much expense, etc. ... yet some of the same folks would think nothing of adding a small jib.

Maybe I just have irrational feelings about jibs, but in theory I like this MUCH better than adding one of those annoying little triangular sails at the front of the boat.

I think you need to re-read my post. I don't object to the cost or complexity, and I certainly would agree that the aft board helps tracking. I just think you enhance performance more by adding sail area rather than wetted surface.

I regularly sail an Egret replica that has too much weather helm. I've fixed part of the problem by moving ballast farther aft and being careful about where I position my passengers, but adding a small jib made the boat tack better and go faster.

[Roger Long]

I regularly sail an Egret replica that has too much weather helm.

Can you post or point me to a profile plan of this boat? I'd like to see what a similar boat with too much helm looks like at this point.

Would you tell me what rudder angle you are carrying at the point you feel like you have too much weather helm?

[Thorne]

Ooooh - a real, untreated case of Brevisantevelumophobia!

Jibs can certainly be a lot of trouble, but they do provide a relatively quick way to modify sail area and counter excessive weather helm.

[johnw]

Can you post or point me to a profile plan of this boat? I'd like to see what a similar boat with too much helm looks like at this point.

Would you tell me what rudder angle you are carrying at the point you feel like you have too much weather helm?

http://lh5.ggpht.com/_Qk62rRa2hGc/SuIY2-r3s3I/AAAAAAAABdc/IrVpqhu_tVo/Fullscreen%20capture%2010232009%2015703%20PM.jpg

Here you go. I generally figure at 10 degrees, it's time to let the mizzen out. It's probably acting as a brake from about 5 degrees, but you want to get something out of the mizzen. The imbalance means you often get little push out of the mizzen. I calculated how much I would have to increase the size of the main, and it was a lot. Plus, we'd need a new mast, new gaff, new boom, new sail. I added a short bowsprit and a jib from a Geary 18, and the boat sailed with a neutral helm, tacked with alacrity and went faster than it ever had. Then one of our volunteers took the makeshift bowsprit home to make it prettier, and keeps forgetting to bring it back...

By the way, this centeboard is not very effective. Some triangular centerboards are, but you need a steeper angle on the leading edge.

[rbgarr]

Like Steve Paskey I was going to suggest a skeg.

[johnw]

Just went back to the original thread and realized, you've already proposed to set a jib flying.

http://www.rogerlongboats.com/images/Yawldory.gif

I think you're right, though, even with the jib it could have some weather helm. You might think about a shorter case, so that the shorter board would sit farther aft when it's down.

If you have a jib you can back, that makes being slow in stays less of a problem -- you can back the jib to bring her around. I do think that if you go for two boards, they should both be centerboards that can kick up as you come into a beach.

[T. Traddles]

Wasn't it Landseer Mckenzie who utilized a double board on his Heathen Chinee design? He liked it enough to utilize the arrangement on subsequent boats as well.

[Roger Long]

Like Steve Paskey I was going to suggest a skeg.

And screw up that nice flat bottom? Away with thee! Besides, the hull has quite a bit of skeg. I doubt that any amount of skeg you would want to live with would effect the balance much.

[Clinton B Chase]

Ben Fuller, a guru of small boats, often mentioned to me the value of a drop down skeg in an open water rowboat oriented towards performance. I have often rowed wanting a little more bite aft to help with tracking, esp. in classically tough conditions like beam reaches in a seaway. While rowing the stern often gets blown off...especially in a dory! In my dory I added a shallow skeg to help with this.

But the Balance you are talking about is sail area...a skeg won't change balance much. I think more adjustability in the sail area and the mast position eliminates much worry. Adjust to the conditions.

[JimD]

And screw up that nice flat bottom? Away with thee! Besides, the hull has quite a bit of skeg. I doubt that any amount of skeg you would want to live with would effect the balance much.

I think the skeg suggestion is for a retractable skeg, a mini centerboard aft, so to speak. Not uncommon on kayaks to keep the stern from getting blown down wind to counter the way the bow gets anchored in the water by the bow wave.

[esingleman]

It seems to me the solution to this problem would be to make the CB box a bit longer than the CB and devise a mechanism to slightly adjust the CB position fore or aft for various sail configurations or wind conditions.

[Daniel Noyes]

Center board has a good amount of adjustability just in the down angle, if you want real adjustability keep the centerboard sized box but go with a dager board and you can slide the dagger forward or aft.

I hesisitate to use two foils as it will slow the boat in heading up in a sudden gust of wind, not a big deal on a keel boat but a consideration on a light open boat.

The Alpha with it's 18' boom carries considerable weather helm but I see this as a big pluss as it contributes to a very positive feel in the rope and yoke steering, I can steer buy holding the lee line and just letting out or taking in.
The rudder is sized such that centerline to a degree or two is sufficient angle to hold a straight course.
http://farm3.static.flickr.com/2550/3882390887_62f8234da6_m.jpg (http://www.flickr.com/photos/dansdories/3882390887/)http://farm3.static.flickr.com/2455/3883172624_c09893bd53_m.jpg (http://www.flickr.com/photos/dansdories/3883172624/)http://farm3.static.flickr.com/2624/3882378845_43e6a2f0ee_m.jpg (http://www.flickr.com/photos/dansdories/3882378845/)
Dan

[andrewe]

Not been mentioned is that some of the extreme big racers use extra aft boards for downwind. Bolger also talks about them.
The idea of a retractable skeg/board sounds good. Not the dagger board, but a shorter hinged kick up type. More work, but could produce nicer handling for longer tacks.
A

[johnw]

The more I think about this, the more convinced I am that the simplest solution is the best. Make the board and case shorter, so when the board hangs down at the angle shown it lies farther aft. You could shorten it at least a foot, maybe 18 inches, and still have an effective board.

[Roger Long]

The rudder is sized such that centerline to a degree or two is sufficient angle to hold a straight course.

If you don't have excessive helm angle, you don't have weather helm. If you are holding course with just a couple degrees of angle, the boat is nearly perfectly balanced and the steering pressure is a function of the steering gear.

See my long rant on weather helm.

[Roger Long]

Make the board and case shorter, so when the board hangs down at the angle shown it lies farther aft. You could shorten it at least a foot, maybe 18 inches, and still have an effective board.

Less board means more leeway angle and therefore more sideways flow component and more rudder pressure. Shorter moment arm between board (most of the lateral plane in this case) means more rudder angle to develop the same balancing side force. Moving the board a foot doesn't change the sail plan / hull balance very much and there are two factors working against it. I'm not sure you would get as much out of this change as you think.

See my Weather Helm rant.

[john welsford]

Some years ago I used an aft daggerboard in a successful Mini Transat design, it was though a very specialised application and my objective was to produce a boat that would be directionally stable relative to wind direction over the widest possible range of wind directions with a wide range of sail combinations. It worked extremely well, but remember that this design was 3m wide on 6.5m long so was of somewhat unusual hullform, had a rig 14 m tall, (working sail was about 450 sq ft on less than a ton displacement and 21 ft) had a canting keel which presents issues as to what happens to the center of lateral plane when its angle is altered and it also had twin "handed foil" daggerboards in the bow as well as twin rudders.
It took several minutes for the singlehanded skipper to tack her and get her trimmed and settled on a new course, but in the context of a transatlantic race that was not an issue, what was an issue was the very limited electrical capacity on board and the power hungry nature of the autohelm. Making the boat able to self steer most of the time was a large part of its success so was worth the complication. WIth that and a couple of other tandem centerboard "experiences" behind me, I can say that in most cases they are not worth the complication, but that they are in certain specialised uses, very effective and in fact I'm drawing a long range small crew cruiser at present that will have that feature.

I have though done several small boats with centerboards unusually far forward, and large balanced rudders which essentially function as tandem centerboards with the after one steerable, and that can work very well. It might Roger be worth some thought in your case.

I note your background as a professional, and your willingness to ask for input when designing these small boats is refreshing. I often tell the story of a client who left it until after I'd completed the design for a yacht tender for him to tell me that he was a Southhampton University graduate Naval Architect, but training in the design of internal compartmentation of bulk liquid carriers was not in his opinion a lot of use when trying to design an under 8 ft dinghy that would not toss his wife into the oggin when they tried to board it from their yacht.

John Welsford



It might well be on this boat but tandem boards is a concept that hasn't been worked with nearly enough. There's more to it than just being able to fiddle with the balance. A foil near the ends of a vessel that is swept sideways through the water when the vessel yaws will resist these forces more than one near the middle that goes through less of an arc or is just being twisted in the water. Splitting the lateral plane into two separated parts increases the yaw resistance dramatically.

When you want directional stability, pull up the forward board. When you want maneuverability, pull up the aft board. You'll then have a tremendous moment arm on the rudder.

I've often thought my ideal long distance cruiser would be a large version of something like the yawldory with one board way forward and one way aft. The trunks would be away from the prime accommodations space. The boat would heave to wonderfully with mizzen set and just forward board down. Shoal draft, beachable. Running before the wind with a small jib and just the aft board down should be equally impressive.

Spaulding Dunbar of Cape Cod was a great proponent of boats of this type. He told me about being in one of his long, skinny, tandem board vessels in a Gulf Stream storm with both boards up watching her just skidding sideways down the seas just ahead of the breaking crests. Having watched my double paddle canoe do the same thing in wind driven breakers (not the same thing as waves in shoaling water) I can easily believe his account. If you think of my canoe as a big model it's a good test of a 40 ish boat in a major offshore storm.

[johnw]

Less board means more leeway angle and therefore more sideways flow component and more rudder pressure. Shorter moment arm between board (most of the lateral plane in this case) means more rudder angle to develop the same balancing side force. Moving the board a foot doesn't change the sail plan / hull balance very much and there are two factors working against it. I'm not sure you would get as much out of this change as you think.

See my Weather Helm rant.


Then give the boat a leg-of-mutton mizzen. Less area and a CE that's farther forward. With the jib, you'll still have enough sail area. If the boat's not balanced, you'll have to ease the mizzen and luff most of it, as I've had to do sometimes on the Egret replica. You end up not being able to use the bigger sail, or putting on the brakes with the rudder, so what's the point of having a bigger one? Better to sail with just a couple degrees of rudder and all sails pulling right.

[Roger Long]

so what's the point of having a bigger one? Better to sail with just a couple degrees of rudder and all sails pulling right.

(Ribald opportunity let pass)

The point is that all these kinds of changes don't make the boat "balanced" or "unbalanced", they just change the wind velocity at which there is a specific rudder angle. The boat with the sprit mizzen will have the same rudder angle in a couple knots less wind so you have to reef or ease the mizzen a bit earlier.

You can reef or luff the sail you have but you can't as easily add to what you don't have. This is a large boat that isn't going to be a lot of fun to row so having that extra mizzen available should be a good thing. If you look at many traditional designs, especially catboats, from the time before engines in small boats were practical, you will see lots of sail aft. These boats would be considered nearly uncontrollable today but they reefed early and often. They needed the light air ability.

The owner is going to make her own sails and will probably have a very light mizzen staysail like kite and a larger ghosting jib. A leg o mutton mizzen might well end up in the inventory for spring and fall when winds are fresher. The owner paying sailmaker's prices might just stick with what I've drawn.

[johnw]

With the fairly straight keel, trim will make a lot of difference, too. If he keeps the weight aft, it will help a lot. The Egret trims better since I removed a bunch of ballast from under the forward cockpit. Still works better with the jib, though.

[johnw]

(Ribald opportunity let pass)


I know, I know, you're thinking, 'if size doesn't matter, why do they look so happy when they see my mizzen?'

[Canoeyawl]

My experience with smaller yawls (designed without the engine option) is as it breezes up uncomfortably beyond the first reef in the main I would always rather take down the jib. There is enough wind at this point to sacrifice the efficiency of the jib.
This keeps you out of the bow when it is becoming critical and dangerous for the boat to lose way/steerage and leaves you with a self-tending rig. If you've ever had to crawl to leeward and dive under water to cast of a jib sheet you appreciate this self-tending part! In a real seaway, the last thing you want is to be unable to steer. Better to spill wind and violently luff along than be stopped dead and unable to luff, as heading-up is no longer is an option with a heavy gust. This is from experience in the Pacific, which is anything but!
It requires a little different approach to designing the "balance"- and is a contrary sailing technique to larger yawls that were designed around a loophole in the "rules".

[aldebaran]

Just a simple one.

I f I was to sail a yawl, I would prefer a yawl which balanced with all sails set. To me the whole yawl idea is to be able sail with mizzen and jib. I have sailed big yawl like that and its very nice. Perfect control and balance with the sail center very low
I would suggest that you balanced the boat installing the center board further aft or that you completely change the rig.
To design a boat, knowing it would have weather helm with all sails set is not what I would consider a good adea or a good design

[Roger Long]

To design a boat, knowing it would have weather helm with all sails set is not what I would consider a good adea or a good design

Well, that would be all properly designed sailboats. A boat is not "balanced" or "unbalanced". Rather there is a wind velocity at which either rudder angle becomes excessive or the sail trim has to be adjusted. All else being equal, as in talking about this specific design, the farther forward the daggerboard is, the lower that wind velocity will be. No question that particular wind velocity has been lowered by the new centerboard design but I'm still trying to get a handle on whether it is too low.

It's a complex question. If this boat were being designed for 2-3 athletic young fellows to try and win the Small Reach Ragatta, the board should probably be farther aft. For the clients, two women about my age, it may be just right.

This is a long, narrow, well balanced hull with the rudder well aft of the sailplan. It doesn't have the other factors that contribute to excessive helm other than not having a lot of sail carrying power. My inclination at this point is to first look at improving the effectiveness of the rudder. The tiller will be long of necessity so helm effort shouldn't be an issue.

[Susanne@PB&F]

Tandem Lateral-Plane solutions for various balancing-challenges are reasonably developed. See cases cited below in BOATS WITH AN OPEN MIND:

- See #463 50' BARNOWL (Wishbone Schooner) for Tandem-Centerboard.

- See #561 29' WHALEWATCHER (Balanced-Lug Cat-Yawl) for amidships Leeboards with Bow Daggerboard for shallow-draft aft-rake of boards balanced by shortish bottom-raked daggerboard.

- See #478 11' DART (Spritboom Cat) for small bowish Centerboard with Big Rudder Aft; see also WB#157 Nov/Dec 2000 on #625 St. VALERIE (Balanced Lug Cat-Schooner) years back with similar geometry.

With more time more might be found just in this archive.

[coelacanth2]

WB had an article about the Massachusetts boat designer Sterling Dunbar. IIRC he was a frequent proponent of tandem centerboards.

[Roger Long]

WB had an article about the Massachusetts boat designer Sterling Dunbar.

Sterling he was but Spaulding was his name.

[Canoeyawl]

the whole yawl idea is to be able sail with mizzen and jib.
A couple of notes*
Jib and mizzen is a great way to sail, either for an easy lunch or in a hard blow as it may be the last resort. But often the jib and mizzen combination is not powerful enough to work to weather in a seaway and you need the additional power of the (reefed) mainsail.
In a hard chance the jib must be powerfully tensioned or it won't work to windward well. This usually means running backs or other powerful rigging on the mainmast and these options are not typically found on small yawls. If you are in a lee shore situation and can't fall back on an engine, you do not want to risk missing a tack. When that jib is flogging so hard that it is shaking the mast like a dog with a toy, tacking can be a dicey proposition. Roller furling is very good in this little scenario as you can roll it in; safely complete the tack with the mizzen then ease the jib back out, but my own preference is a double or triple reefed main and the mizzen. All this depends on the individual craft and its balance, with our Rosinante the mizzen is the first to go, with Sally (http://www.canoeyawl.com/images-boat/Picture036.jpg) it is the last.
I will add here that sailing these little boats in the kind of conditions I'm speaking of is dangerous and not for the timid or those with a heart condition, but occasionally we get caught out.

[johnw]

I suspect for windward work, this boat will balance fine as a sloop. I've noticed some sprit sloops have the jib lead on the other side of the mast from the head of the sprit main, so that the head of the spritsail can tension the luff of the jib.

As for rudders, a big barn-door rudder on a boat this small isn't bad. The area above the waterline becomes useful when the stern wave builds up, which is also when you need the most rudder. Or you could give up on the traditional-looking rudder and give it a big, effective kick-up rudder like some of those racing dinghies have. It would take less trouble and treasure than a second centerboard.

[Roger Long]

I suspect for windward work, this boat will balance fine as a sloop.

That's more or less the idea. The boat will primarily be used in areas where reaching will be the most common point of sail. In winds strong enough for heavy helm to be a problem, some sail reduction will be desired anyway.

A lot of schooners with their huge mains were sailed as ketches much of the time. The big fisherman only set the main once a year for the race home to market and carried a trysail for the season.

The Isle of Shoals boats didn't even have centerboards. There were fish in every direction in those days so they evidently would just reach in the direction indicated by the wind. Boats restricted in fishing direction by shore geography had centerboards.

[johnw]

With the board most of the way up, they should get some use out of the mizzen.

I was looking at boats with more or less this rig in American Small Sailing Craft last night, and I think most of them went with a substantial skeg and a short, tall centerboard case. That setup appears on the Crotch Island pinky, the Kingston lobster boats and the Erie and Huron boats. The centerboard below the hull when down was close to an equilateral triangle, which in my experience is much more effective than the long shallow shape shown on the Egret replica. I'm thinking the original Egret must have had a shorter case and a steeper angle on the leading edge of the board for the boat to have performed as well is she was reputed to. Too bad a tall case would interfere with the intended use of the yawldory.