Rig Balance

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Nov 22, 2008
3,562
Endeavour 32 Portland, Maine
It’s raining this morning so I’m listening to music which is a good excuse to rant about something and I’m sick of politics. I just took a cruise over to the “All Discussions” forum and saw a post from the Beneteau forum, “Weather Helm” in which it was suggested by a couple of posters that mast rake was the first thing to look at. I hate to see that old chestnut whenever it appears and it’s apt to make the poor OP waste a lot of time fiddling with his rig to no detectable effect.

The whole rig balance subject is one of the most misunderstood in sailing. There is really no such thing. Reducing mast rake, thus moving the sail area slightly forward, will reduce the rudder angle; in theory. However, it would take very careful measurements and extreme care to be sure you hadn’t changed anything else to detect it.

The source of the whole rig balance myth has its roots in racing boat design. Races are won or lost on the last few percent of performance that cruisers couldn’t even detect without careful data recording or other vessels close along side. The racing boat designer wants to have an exact rudder angle in a specific condition, just before a sail area reduction or sail shape change is made. This angle will be enough to provide some lift to windward (that weather helm is pushing in the right direction, opposite leeway) and good steering feel but not so much as to create excess drag. The whole business of calculating the center of effort of the sail plan and comparing it with the geometric center of the sail plan is based on obtaining this exact rudder angle. It only works with a large data base of similar hulls, sails of known quality, and all other factors carefully controlled. The racing boat designer and owner care whether the rudder angle in this specific design condition is, say, 6 degrees instead of 5. It doesn’t matter one whit to the cruising sailor.

This whole lead calculation business has created the widespread belief (alive and well on SBO evidently) that there is a magic balance point. If the rig is exactly on the balance point, the boat will steer properly. Move the rig just slightly aft (too much mast rake) and the boat will have “weather helm” move it too far forward, and the boat will have “lee helm”. This is poppycock.

It is true that, all else being equal, moving the rig aft will increase rudder angle and moving it forward will reduce it. However, huge movements are required to create the kind of changes that would cause a cruising sailor to think of his boat as having or not having weather helm. Other factors are for more significant so that the amount of lead, which is slightly changed by mast rake, is simply a signal lost in the noise except under the carefully controlled conditions of racing boat design and tuning.

Need convincing? My boat has a strong weather helm. It was a lot more than I liked. I had a new set of sails built with a smaller jib. This, in theory, moved the center of the sail plan back which should have increased weather helm. Instead, helm force and angle were significantly reduced by the conversion from old, blown out, sails to those of proper shape. If the wind comes on hard and I’m struggling with strong helm forces and listening to the roar of water pouring over the top of the rudder at 15 – 20 degree angle, I can roll up the jib. The center of the sail plan has now been moved back a few feet and yet weather helm is reduced to almost nothing.

Heel is a major factor in weather helm. The drive of the sails is out to leeward and the drag of the hull is closer to windward. Whenever you have two offset forces, there will be a turning moment. Heeled hulls also tend to want to turn towards the high side due to the wedge of the leeward bow and other wave train effects. Rudder angle basically increases with heel if all else is kept constant. Dump your main so that it is doing almost nothing and rudder angle and helm force will decrease. This will have as much to do with heel reduction as it does with moving the center of effort of the rig several feet forward. Watch what happens if the wind keeps rising and you are forced back to the same large heel angle. Rudder force and angle will increase again. They will be less than with the full main but not by as much as the simplistic rig balance model would lead you to expect.

Speaking of angle and rudder force: much of the time when this subject is being kicked around in bars and Internet forums, no one knows which the other is talking about. It is possible to have very high helm forces and yet the rudder at exactly the optimum angle. This is a function of the steering system. Think of a boat with a very short tiller. It will take a lot of force to keep the rudder at even a small angle.

Weather helm is when the rudder is at such a large angle that the boat is slowed and the ability to make the boat go where you need it to go is compromised.

When someone with a standard boat like a Beneteau says they have weather helm, I suspect they aren’t steering the boat properly to windward. Excessive weather helm is the boat trying to tell you something. Heel is a major contributor to helm force and reefing is a lost art. People are commonly taught how to read jib tell tales but there are many of them sailing around doing it by rote without paying attention to heel. When the boat heels beyond its optimum angle, ease off on the helm pressure and forget what the tell tales look like. Let her up to the angle at which she was previously going well and the helm force will decrease. The trick is to do it very slowly without letting the boat start swinging. Think of it as a pressure reduction on the wheel or tiller instead of a steering motion.

If you are one of the many people who just strap the sails in and then keep your WindEx lined up with those stupid little indicators that come with them, forget it. You are going to think you have weather helm. When conditions are puffy and heel is large, the difference between having the boat going well and struggling with too much helm will be far too fine to identify with something on the masthead.

The basic technique for sailing to windward is very slow easing of pressure to let the natural weather helm bring the boat closer to the wind. You should just barely be able to see the bow swinging against the shore background or horizon. If there are waves, the bow should remain fixed against the background and just take a little nibble to windward at one point in the pitching cycle. You are trying to sneak up into the wind as slowly as possible. As soon as a windward tell tale breaks sharply upwards or you see a sudden slight decrease in the angle of the mast against the horizon, give the wheel or tiller an instant and decisive movement steering to leeward and hold it until the tell tale lays down and the boat takes hold again. Then resume the slow reduction of pressure to let the boat start working up again. The proper course to windward will be a zig zag with long shallow scallops to windward and quick turns back to leeward.

This assumes a steady wind. If conditions are gusty, you sail like this in the normal wind and then let the boat come up in the gusts so that the heel angle remains constant. Paying attention to the angle of the mast against the horizon is one of the best weather helm reduction methods there is. Of course, almost no one can use it now that everyone has full dodger and bimini outfits.

If your rudder angle is still too large in the wind between the gusts, it’s time for a sail area reduction. Reefing now uncommon but, if people practiced it more, they would be surprised at how often the boat speeds up when reefed. You’ll see this most reliably if you reef before the boat is over pressed. Most people put it off too long.

You might be interested in reading this article I wrote about sailing a big schooner to windward. I don’t sail Strider this way and you won’t be able to sail your boat exactly like this because the surface wind smaller boats sail in is simply more turbulent down near the water surface or near land. However, and understanding of the principles can help make you a better helmsman.

http://www.pointseast.com/template.shtml?id=EEuApppyplMkENKsEG&style=story
 
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Jan 2, 2007
131
Morgan 461 St. Thomas
Schooner than later...

Reading this, I thought of that article. Well done, in both instances...

I'm going to link this to my E43 buddy, as we just went through some major nuisances to bring his mast forward to spec (he'd had it out of the boat, and an entire project boat of 9 years, including rebuilding the mast step, before putting it back)...

This is much better reading than your other stuff of late :{))
 
Sep 15, 2009
6,243
S2 9.2a Fairhope Al
Re: Schooner than later...

thanks for sharing that with us Roger......this has solved a mental dilemma for me....i feel that the designer of my boat must have known what he was doing in setting up the mast ....haveing said that if I just set it up the way it was intended...basicly plumb or perpendicular to the water line...and practice the reefing as you refer to i will be just fine...as I have no intentions of micro tunning my boat to achieve that .05% extra that one may or may not gain...if the boat is designed to run 6 knots and i can get that then I feel if its good enough for the designer... then its good enough for me.....

regards

woody
 
Feb 26, 2004
22,760
Catalina 34 224 Maple Bay, BC, Canada
Great, thanks, Roger. We should all save this and link back to it when the darn subject comes up, yet again.

One thing to add: Most of us have masts that are like telephone poles, and NO amount of adjustment is going to "bend" them, masthead rig or fractional, doesn't matter. The only thing that I've found helpful is a backstay adjuster to help avoid the forestay droop, but unless the rig is tuned properly that won't help much either.
 

rbgarr

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Sep 10, 2011
15
Shields 30 Boothbay Harbor
...i feel that the designer of my boat must have known what he was doing in setting up the mast ....haveing said that if I just set it up the way it was intended...basicly plumb or perpendicular to the water line...and practice the reefing as you refer to i will be just fine...as I have no intentions of micro tunning my boat to achieve that .05% extra that one may or may not gain...if the boat is designed to run 6 knots and i can get that then I feel if its good enough for the designer... then its good enough for me.....

regards

woody
I feel the same way, except that when running, if I slack the backstay WAY off, enough so the forestay wobbles around loose, the boat will sail much better and faster.
 

weinie

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Sep 6, 2010
1,297
Jeanneau 349 port washington, ny
Excellent read Roger. Thank you. Any more like that?
 
Jun 17, 2007
402
MacGregor Mac26S Victoria Tx
A bit of clarification. Roger, I can understand the mast rake isn't always the cause of weather helm but shouldn't the mast rake be within the manufacturer's specs?
(To eliminate that as a possible reason) Then look for other causes?

In other words, don't try to fix the problem by making an over correction with the mast rake?
 
Nov 22, 2008
3,562
Endeavour 32 Portland, Maine
I can understand the mast rake isn't always the cause of weather helm but shouldn't the mast rake be within the manufacturer's specs?
(To eliminate that as a possible reason)
Mast rake, within any limits that wouldn't cause other boaters to say, "Whoa! What the #^%&&#%c is going on with that boat?", will never be the cause of weather helm as we are likely be discussing it here.

A racer, with a boat that, for reasons of sail cut or design, has a higher rudder angle than he feels optimum, might decrease his mast rake to zero. In this case, the boat might be carrying a 6 - 7 degree rudder angle in a specific set of conditions when the owner thinks it would be faster with 5. Taking the rake out of the mast might reduce the rudder angle only half a degree. In the racing mindset, this is an improvement and a reduction in "weather helm". Racers do many things that may never be proven to increase speed in any measurable way but it's all about margins on the race course. If he wins a race by a few seconds, as often happens, he can congratulate himself on re-raking the mast.

The context in which the too much weather helm question comes up in forums like this isn't likely to be a boat carrying a 7 degree rudder angle instead of 5. It will be a boat carrying 15 - 20 instead of 5. The tiny rudder angle changes that things like fiddling with mast rake can achieve aren't going to fix that. It's much more likely to be a matter of bad sail shape and/or poor helmsmanship combined with carrying too much sail for the conditions.
 

CalebD

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Jun 27, 2006
1,479
Tartan 27' 1967 Nyack, NY
Very nice post Roger.
This helps explain why the Lightning 19' I briefly owned had the mast raked so far aft. They wanted the boat to head up into the wind and not capsize, as a Lightning could sink if swamped.
With racing dinghies you can affect performance a lot more then with an older boat with a telephone pole mast like mine.
 
Nov 22, 2008
3,562
Endeavour 32 Portland, Maine
With racing dinghies you can affect performance a lot more then with an older boat with a telephone pole mast like mine.
In boats of any size, the shorter and higher aspect ratio the keel is, the more sensitive the boat will be to changes in fore and aft location of the geometric center of the rig. The very high performance boats with a deep, narrow, vertical keel may be able to see significant changes in rudder angle with mast rake. Typical cruising and cruiser/racer types won't.
 
Oct 28, 2008
24
Catalina 320 Lake Texoma
My usual suggestion to the novice sailor is "reef early, reef often". It might save your bacon, your boat, or your pride.
 
Jun 16, 2011
173
Catalina 350 Rock hall
bentwing60 said:
My usual suggestion to the novice sailor is "reef early, reef often". It might save your bacon, your boat, or your pride.
I am with you if there is even a question I leave the dock with a reef already in if it gets boring it is one second to shake it out
 
Apr 19, 1999
1,670
Pearson Wanderer Titusville, Florida
Outstanding piece, Roger. The part about the turning couple caused by the offset between driving force and drag when excessively heeled is so true. What's also true is that it happens even with proper sail trim, so it's not obvious. Thanks for pointing it out.

"I don't always sail fast, but when I do, I prefer less heel. Reef early, my friends."
 
Oct 28, 2008
24
Catalina 320 Lake Texoma
In boats of any size, the shorter and higher aspect ratio the keel is, the more sensitive the boat will be to changes in fore and aft location of the geometric center of the rig. The very high performance boats with a deep, narrow, vertical keel may be able to see significant changes in rudder angle with mast rake. Typical cruising and cruiser/racer types won't.
Roger,

Not to question the naval architect, but here goes. Aspect ratio is defined as the ratio of wing (keel) length vs. chord, so a higher aspect ratio keel would be a deep skinny one and a lower aspect ratio keel would be a shallow wide one. So when I read this post I said to myself, self, that is an oxymoron. Did I read wrong what you wrote right, or did I read right what you wrote wrong? I have a hard time equating higher aspect ratio with shorter keel. Some would call this splitting hairs, some would call it fundamental, I would call it I'm trying to apply it to my knowledge bank. I don't know a lot of naval architects or have a lot of experience with boats with really big keels. I rake the mast (pole that won't bend) on my C-320 about 3 degrees with a snug standing rig. Fin keel, big rudder, tender boat. Rig my own boat, bought it new in 99, and this makes me wonder if I made it more tender or less. Some success at the start line and the windward mark, the rest is a sobriety contest.
 
Nov 22, 2008
3,562
Endeavour 32 Portland, Maine
Did I read wrong what you wrote right, or did I read right what you wrote wrong?
A high aspect keel would be deep and narrow, looking sort of like a centerboard. The modern racing sleds with a nearly vertical deep and narrow keel with a bulb on the end would be an extreme example. The traditional, long keel attached rudder cruising boat is at the other end of the spectrum.
 
Oct 28, 2008
24
Catalina 320 Lake Texoma
You missed the question. By raking the mast, did I make it more tender or less. I could go back and make it plumb as Catalina designed it or, as I suspect I will do, it ain't broke so I won't fix it. Sometimes racer, mostly beer drinking sailor.
 
Nov 22, 2008
3,562
Endeavour 32 Portland, Maine
By raking the mast, did I make it more tender or less.
Rake has no measurable effect on stability. It thus will not make the boat more or less tender.

Mast bend, which will pull some draft out of the sail and flatten it, reduces the power developed. Less power will mean slightly less heel and thus slightly less weather helm when close hauled.
 
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