ADDENDUM TO: AN EXPRESSION OF DOUBT – HOW CAN HYDROVANE SELF-STEERING REALLY BE ANY GOOD?
I’ve written this post as an addendum to my earlier piece, An Expression of Doubt – How can Hydrovane Self-Steering be any good? in part because someone questioned whether it was fair for me to criticize a product with which I have no experience. And in principle I wholeheartedly agree. Yet in my defense, I made it clear I had no personal experience a Hydrovane. I confessed that I could not understand how it could work very well. The questions I raised were based not on pure speculation but on the promotional material of the product itself – they are the kinds of questions that I would like to have resolved before I would purchase such a unit.
But I do so much prefer talking about stuff I really know about, so I’m taking a different approach this time. I’m revisiting the Hydrovane promotional material again, but this time I’m looking at the way it represents its primary rival, namely servo-pendulum self-steering gear. Hydrovane makes some rather grandiose claims about its superiority vis-à-vis servo-pendulum gear, but they are based on gross misrepresentations which bring up basic issues of credibility.
A major claim that they make repeatedly is that servo-pendulum gear doesn’t work well in light air. They say, for example, “we have too often heard owners of servo pendulums that are very proud of their units but advise that they only work, when off the wind, in a minimum of 15 or 20 knots of wind!!” But this can hardly be true, or at the very least it is the product of extremely selective hearing. If the servo-pendulum is set up correctly, it should not require any more wind to steer the boat than a Hydrovane. In fact, the windvane on a servo-pendulum actually does less work than the windvane on a Hydrovane. On the Hydrovane, the windvane has to turn a rudder – a rudder that’s smaller than the boat’s own rudder, but which is nonetheless much larger than the steering oar of a servo-pendulum gear. After all, this rudder is steering the boat. On a servo-pendulum gear, the function of a windvane isn’t to steer the boat but to turn a small, balanced oar, which in turn harnesses the power of the water rushing past the boat. In effect, the windvane on a servo-pendulum only needs enough wind to send a signal to the steering oar; the windvane on the Hydrovane needs to get all of its power to steer the boat from the wind. Indeed, this is why the windvane on a Hydrovane is significantly bigger than on a servo-pendulum gear.
A boat with a servo-pendulum needs to be moving through the water for the gear to work. I would estimate that once our boat reaches, say, 2 ½ knots, the gear can steer the vessel without any problems. I can imagine that a Hydrovane might be able to steer a boat that is moving slower than this, though this would also mean that there was very little wind. But a more likely scenario would feature a boat sailing dead down wind in light conditions. The faster the boat moves, the less apparent wind is experienced by the boat and by the windvane. In such conditions, a servo-pendulum will have plenty of power to steer the boat – the tricky part is having enough wind to send a signal to the steering oar (sometimes we’ll increase the area of our vane by clipping on a piece of cardboard). But I imagine that the Hydrovane would have an even more difficult time, for it needs the wind not only to send a signal but also to power the rudder.
Another point the manufacturers of Hydrovane repeatedly stress when comparing their windvane with servo-pendulums is that their unit has “very little friction” and thus performs better in light air. They add, too, that if there is any “excess friction in the system – stiff rudder, arduous connecting lines” then the servo-pendulum unit suffers all the more. This is most certainly true – but it is also misleading and largely irrelevant. To meaningfully discuss of the role of “friction” in a servo-pendulum system, one must distinguish between that part of the system powered by the wind and that part powered by the water. If anything, the part of the servo-pendulum system powered by the wind should generate less friction than the hydrovane – it performs less work. The part of the system that is powered by water – from the lines through the blocks, to the tiller/ wheel, from the wheel, to the cables, to the rudder – obviously generates a lot more friction than the Hydrovane. But it shouldn’t matter. Given the amount of power generated by the oar in the water, that friction should be easily overcome. If “excess friction in the system – stiff rudder, arduous connecting lines” – is really limiting the effectiveness of the gear, then something is seriously wrong.
A third misleading point made by Hydrovane is that “all servo pendulum systems, when matched against a Hydrovane, are comparatively unsophisticated. Once engaged they do a meandering sort of course correction without any means of tuning or straightening its course.” Frankly, this assertion is so divorced from reality that I hardly know what to make of it. The manufacturer at this point in its promotion is really trying to emphasize Hydrovane’s own “sensitivity adjustment” of its vane axis and its three different “rudder settings.” To set up a striking contrast, the manufacturer wants you to imagine that its servo-pendulum rival has “no means of tuning.” How ridiculous. Our Sailomat (which like all decent servo-pendulum gear begins with a sophisticated geometry) can be “tuned” (from the top down) as follows: changeable windvane sizes, moveable counterweight, adjustable windvane lever arm, adjustable push rod, adjustable lever arm at the steering oar, selection of line attachment points at the pendulum, a wide range of block configurations for the lines, adjustable lines for balancing the helm. Some of these things are adjusted when one sets up the gear; others can be used to adjust the gear for different sailing conditions. I will concede the point that “all servo pendulum system lack this [namely Hydrovane’s specific vane axis] adjustability for sensitivity,” but we are talking about different kinds of systems here. Kinda like criticizing an orange for not having apple seeds.
A fourth misleading point made by Hydrovane pertains to the way the boat’s rudder is utilized by the Hydrovane and by a servo-pendulum unit. The Hydrovane needs to set the main rudder in a certain position that balances the boat so that its own auxiliary rudder is effective. The manufacturers then criticize the servo- pendulum system because it cannot balance the rudder in the same way, but they misrepresent the way the system actually works:
A servo system cannot match the configuration of locking your main rudder to render your boat perfectly balanced. … A servo pendulum system must perform a lot of steering that a Hydrovane does not have to do. … On every turn it must deal with the forces of any weather helm or lee helm – not so for an auxiliary rudder system which has no weather or lee helm to deal with as the positioning of the locked main rudder compensates for such ‘pulling’ by the positioning of the main rudder – neutralizes any weather or lee helm! … a servo pendulum can struggle with the forces of weather or lee helm on every turn. … Comparatively, a servo pendulum configuration requires a lot of extra steering.
Hydrovane wants you to believe that a servo-system oversteers because it cannot balance the rudder. But in fact, trimming the lines that connect the servo-pendulum to the wheel/ tiller – that is to say, balancing the rudder – is a critical part of properly setting a servo-pendulum gear for the sailing conditions. The rudder is trimmed to balance the boat, neutralizing weather or lee helm, and the lines to the gear are trimmed so that the gear is a neutral position. The servo-pendulum then steers the boat by moving the rudder in relation to this “balanced” position. What Hydrovane has done here is to describe the wrong way to use a servo-pendulum unit and then criticized its operation. They might as well be telling you that shoes don’t protect your feet because you wear them on your hands.
And this misrepresentation leads nicely to the next one, in which servo-pendulum gear is portrayed like some kind of savage brute. The passage is worth quoting at length:
If you have ever had the chance to see a servo pendulum operating in bad weather you would better appreciate where that comment about its power comes from. Its activity can be described as perhaps violent as it wrenches the wheel/tiller from one course to the next. One certainly wants to stay clear of that section of the cockpit. We do suggest that there is some overkill in that performance. … The comparison [between a Hydrovane and a servo pendulum] is like the difference between the less skilled hard working rookie and a skilled athlete that makes a play look so easy …
Now, I actually have seen our servo-pendulum operating in bad weather. And I never noticed that it “wrenches the wheel/tiller from one course to the next.” Properly trimmed, it ticks gently back and forth, keeping the boat on course. But when boat get smacked or falls of a wave, and veers in the wrong direction, the servo-pendulum shows its strength, vigorously spinning the wheel to bring the boat back on course, making good use of the boat’s own rudder – an athlete to be sure. At this point, I imagine the Hydrovane would be calling out for help from the autopilot (although I confess I wouldn’t know, because I’ve never used one).
I’ll close with final quote from Hydrovane’s website that attempts to portray a stark contrast between the pathetic inadequacy of servo-pendulum steering gear and the magnificent superiority of the Hydrovane:
A servo pendulum cannot be adjusted for conditions. It cannot help but to over-steer or under-steer. The activity of the main rudder flapping back and forth exacerbates the steering difficulties of a heavy sea. If the same boat had its main rudder fixed it would be far more stable. These issues are complex and hard to understand. I am guilty of a bit of hyperbole in making my point but the concept of the stability of auxiliary rudder systems is well worth appreciating. It alone makes the auxiliary rudder concept superior to any other method of self steering. Adding to that the sophistication and the unmatched versatility of the Hydrovane……….[sic]
Guilty of a bit of hyperbole? You betcha!! I can almost hear maniacal laughter.
Bernhard Heise NZ
AN EXPRESSION OF DOUBT — HOW CAN HYDROVANE SELF STEERING REALLY BE ANY GOOD?
During the past few weeks, two different friends — one here in Whangarei, New Zealand, the other in Boston, Ma. — announced that they had purchased Hydrovane self-steering gear for their boats in preparation for off-shore cruising. I generally like to be encouraging, but news like this always makes my heart skip a beat — just before it falls into my stomach. And while I fumble for an appropriate response, the homunculus behind my eyes shakes his head and mutters: “those guys have made a big mistake.”
In the interest of full disclosure, let me be perfectly clear. I have built my own self-steering gear in the past, I’ve modified the one we’re using now (because I like to tweak), and I have helped others get their self-steering gear under control. But I have no personal experience with a Hydrodvane. You don’t see them very often compared to other kinds of systems. The only one I’ve ever fondled was on a Waterline 50, and the owner expressed displeasure because it didn’t do the trick. The Waterline 50 is admittedly a large boat — it is heavier than Hydrovane recommends. But the makers of Hydrovane shamelessly encourage the use of their product for boats that exceed their own recommendations, noting that they “know of and even provide many installations for boats in excess of those limits.” They might indeed be willing to “tell you about the many 50,000 lb. or 23,000 kg boats that also have glowing reports of their Hydrovanes,” but the fellow I know clearly isn’t one of them.
My skepticism arises mostly from a theoretical assessment of the gear and from an utter inability to understand how it could possibly work very well. If you want to hear about how wonderful the Hydrovane is, I refer you to their website. But much of what I’ve read there sounds like half-truths. Thus, for example, when you follow the link that takes you to the testimonials of “famous sailors,” you’ll be greeted by a photo of Jimmy Cornell’s “Aventura” sporting a Hydrovane. But what they won’t tell you is that Cornell currently touts the servo-pendulum by Windpilot. “I switched from Hydrovane to Windpilot,” he writes, “because I felt that the Hydrovane system may not be powerful enough for a 43 ft. boat.” Or perhaps Windpilot just pays him more — who knows.
In any event, my purpose here is simply to raise a few doubts and encourage prospective buyers to perhaps think twice before spending “25-40% more than good of servo-pendulums” (for some reason, Hydrovane subscribes to the “if-you-charge-more-they-will-buy-it” philosophy) on a mechanical self-steering device that might very well prove to be a major disappointment.
Something I do know for certain is that robust and effective self-steering gear is the key to happiness. I know this from our own experience and from the experience of watching the tribulations of others. On our passage to Hawaii, our Sailomat servo-pendulum gear kept us on course as we bounced around in the nastiest cross swell we’ve ever experienced in forty knots of wind for days on end; meanwhile, we were in radio contact with a skipper not very far away, whose autopilot (which was supposedly more than adequate) gave up so frequently that he couldn’t get away from the wheel long enough to pee. Another skipper we know on a Valiant 50 from our stay Mexico experienced a thirty-knot blow as a “survival storm” because his autopilot couldn’t do the job. For a short-handed crew, decent self-steering gear – whether it’s a mechanical windvane or an autopilot – makes the difference between heaven and hell.
With respect to mechanical windvanes, there are a number of ways to skin this cat. Most crews rely on servo-pendulum gear. Ours is made by Sailomat, but Monitor is the most common, and there are other manufacturers as well – Aries, Windpilot, Cape Horn, Fleming, Voyager. While we might debate their finer differences, in principle they work the same. A windvane is positioned so that when the boat is on course, the vane is vertical. When the boat veers off course, the shift in the apparent angle of the wind causes the windvane to deflect. The deflecting windvane turns a balanced oar that is in the water. As the oar presents a face to the water rushing past the boat, it is forced to swing like a pendulum. The energy from this swing is transmitted by lines and blocks to the boat’s steering system – either to the wheel or to the tiller – and the boat is brought back on course. Servo-pendulums are not practical for all boats, particularly those that rely on hydraulic steering instead of cables or those with a center cockpit. But there are also other kinds of windvane devices that by-pass most the boat’s steering system and effect the rudder more directly. They use a windvane to deflect a trim tab on the boat’s rudder, which in turn causes the rudder to swing. In all these cases, the power of the wind (which is quite weak) mechanically adjusts the gear so that it harnesses the power of the water (which is immense) to steer the boat.
The Hydrovane, on the other hand, relies solely on the power of the wind to steer the boat. And unless that little magical box which links the windvane to the rudder somehow manages to transcend the laws of thermodynamics, that power isn’t very much. This is why the key to the Hydrovane’s successful operation is balance. As the manufacturer points out, “the trim of the sails and balance of the boat determine how well the Hydrovane can do its job.” And under the “causes of poor performance,” the makers list an “unbalanced boat” (they suggest retuning the rig, changing the rake or position of the mast, cutting the boom — that’s some pretty drastic surgery); “unbalanced sails”; “baggy sails”; and a “main rudder locked on the centerline” instead of in the “balanced position” (this a draws attention to the fact that fiddling with the Hydrovane to set one’s course also requires fiddling with the main rudder)
Now, I have no doubt that the Hydrovane will steer a nicely balanced boat, but that isn’t saying much, because a nicely balanced boat virtually steers itself. Anyone who has struggled with a wheel or tiller to counter weather-helm knows that a balanced boat is easier to steer than an unbalanced one – this applies equally to biological, electronic, or mechanical pilots. Our youngest daughter can steer the boat in perfect conditions; when the sea picks up and conditions get gusty, we let someone else take the wheel. The measure of an effective pilot is not its performance under “balanced” conditions, but “unbalanced” conditions. And on a boat that is being smacked around by waves, conditions can change from “balanced” to “unbalanced” in a heartbeat – the key is having a pilot with the strength to get the boat back on course and “balanced” again
Let me reiterate this point with another quote from the makers of Hydrovane. They say that a “perfectly balanced” boat “leaves a lot less work for the Hydrovane to do — or put another way: makes the Hydrovane’s rudder much more effective.” But the logic of this statement is faulty; it really works the other way around: because the Hydrovane is not very effective, it cannot do a lot of work, so the boat must be perfectly balanced.
Another way the manufacturers turn vice into virtue is when they stress that you can use the Hydrovane and an autopilot at the same time, something that they point out you can’t do with a servo-pendulum gear.
In major storms many have used this technique [that is, using an autopilot in tandem with the Hydrovane] when the Hydrovane appears to be challenged to the maximum and needs all the help it can get. That is often the case in the early hours of a storm when the seas are square and chaotic. Once the storm has blown for a while and the seas become more regular then the autopilot can be turned off.
Sure, it is true that you cannot use your autopilot and a servo-pendulum gear at the same time. But the more important point is that you don’t have to. And what the makers of Hydrovane construe here as a virtue (namely that the Hydrovane and autopilot can work together) is in fact a pretty way to dress up a liability: in fact, the Hydrovane needs an effective autopilot in adverse conditions. Again, they note that an autopilot is “comforting to use in storms when uncertain — [it] can [be] turn[ed] off once control is regained.” Frankly, a priority for me in bad weather is to not loose control in the first place.
As for their criticisms of more conventional servo-pendulum gear, they only make me wonder what the makers of Hydrovane are smoking. “We have too often heard owners of servo pendulums that are very proud of their units,” they write, “but advise that when off the wind they only work in a minimum of 15 or 20 knots of wind – not all, but some!!” This can only be true of the most dysfunctional gear and would be evidence of serious problems. Our own gear works in pretty much any wind (on any point of sail) that is sufficient to bring boat speed up to 2.5 knots. Likewise, I wonder about their drug intake when they make the power of servo-pendulum sound like uncontrolled violence:
If you have ever had the chance to see a servo pendulum operating in bad weather you would better appreciate where that comment about its power comes from. Its activity can be described as perhaps violent as it wrenches the wheel/tiller from one course to the next. One certainly wants to stay clear of that section of the cockpit.
Damn right! We tell our kids all the time to keep their fingers away from the lines, blocks, and wheel. We also teach them to be wary of the loaded sheets and winches. There are a lot of forces at play on a sailboat, especially in nasty weather. But when I look out at our servo-pendulum gear as it navigates our vessel safely through a gale, I don’t see violence but grace, and I feel for it a fondness that approaches true love.
The best book I have ever read on self-steering gear for sailboats is Bill Belcher’s Wind-Vane Self-Steering. Belcher examines an number of different types of mechanical windvanes. His theoretical discussions are incredibly clear. He provides an honest appraisal (untainted by any affiliation with a specific product) of the capabilities and limitations of such gear. And the whole point of the book to help readers construct devices of their own — the book includes detailed plans for a number of different types of gear. Given the outrageous price of self-steering gear, it is reassuring that anyone with moderate skills can make a decent and effective self-steering device for, say, five-hundred dollars. I believe the book is out-of-print, so it may be hard to find. But it’s worth looking for.
Posted by Bernie