Rudder and Steering
In the last chapter we examined and discussed the Adventure 40 hull form. Now let’s dig into the rudder and steering gear.
Those of you who were in on this a few years ago, while we were discussing the de Jong Adventure 40 design, will remember that Erik settled on a transom-hung rudder, either kick-up or cassette.
A popular decision with advantages, most notably ease of inspection and maybe even replacement with a spare at sea, but perhaps not the optimal one. Let’s dig into why:
While they gave a transom rudder serious consideration, the French team have decided against it for the following reasons:
- A kick-up or cassette rudder adds complexity and many more potential failure points.
- The actual practicality of replacing a rudder blade at sea is suspect, and what if the pintles and gudgeons fail or get damaged?
- Having the rudder right on the stern makes it very vulnerable to accidents in harbours and anchorages.
- I can confirm this. Over our years of cruising we have been hit at least twice on the transom by other boats trying to dock behind us, and have also backed into unseen obstructions a couple of times.
- Placing the rudder in the transom slot as Erik did will somewhat reduce the above risk, but at the price of limiting rudder angle.
- By moving away from transom hung, and because the boat has a tiller (more on that in a minute), it will be possible to allow very large rudder angles, which is a simple and effective way of substantially increasing the manoeuvrability—be great in the ever more congested marinas we are seeing these days, particularly for a boat with no bow thruster.
- While possible, it is difficult and more complicated to build a transom-hung rudder that is partially balanced—part of the area being forward of the pivot point.
- Partial balancing is great since it reduces load on both autopilots and vane gears as well as making the boat easier to steer generally.
- Ease of steering is doubly important on a tiller boat where we can’t make up for an inefficient rudder by fitting a powerful wheel setup.
- The stern is already a busy place on an offshore voyaging boat what with vane gears and maybe water generators. Adding those two to a transom-hung rudder would be a mess, and maybe not even doable.
- It’s difficult to install an underdeck autopilot on a boat with a transom-hung rudder, at least in a seamanlike way.
All that’s pretty convincing, but the deal breaker for transom-hung rudders is that they are much more vulnerable to stalling and cavitation, and that gets way worse as the boat heels.
The other issue that exacerbates this problem, is that we want to have at least some overhang aft to provide reserve buoyancy, which reduces and softens pitching, but that in turn would move a transom hung rudder even further aft than on a boat without any overhang.
These problems with transom hung can, to some extent, be fixed with twin rudders or a very narrow stern. On the latter, although we don’t want a big-ass boat, not enough buoyancy aft can be just as bad, so we don’t want to hamstring Vincent from designing the best stern he can by insisting on transom hung and a single rudder.
And a single rudder is not negotiable for the Adventure 40 since twin rudders are more vulnerable to floating debris, expensive, and get us into needing a bow thruster, since we lose the power of prop wash.
The result of this analysis by the French team is that the Adventure 40 will have a spade rudder with:
- A partially-balanced design for easy steering.
- A composite shaft and no metals inside so we don’t get the water ingress and corrosion problems that rudders with metal shafts in composite blades are always prone to.
- By the way, our new-to-us J/109 has exactly this kind of rudder with no metals, and that’s one of the reasons Phyllis and I selected the boat.
- Massive shaft and bearings to take the loads reliably.
- A sacrificial lower part that will break off without damaging the shaft, bearings, or hull in the event of a grounding or collision with debris.
I was a big fan of the transom rudder idea, but after reading the French team’s white paper on the advantages of a spade rudder (the basis of the above) I’m convinced they are right.
What About Skeg Rudders?
What about a skeg-hung rudder, that much-loved alternative of traditionalists and forums?
I used to be a fan, and, like many, believed it was the only seamanlike alternative, but after years of thought and discussion, I’m now satisfied that the superiority of skeg over spade is more myth than fact.
Or, as some wag said, many skegs are held on by the rudder, not the other way around.
The point being that rudder reliability is far more about good engineering and construction quality than type.
The other two disadvantages with skeg-hung rudders are:
- Can only be slightly balanced.
- Generally far less efficient than spades, both when sailing and manoeuvring—our J/109 with a spade rudder steers in reverse as well as she does in forward; the McCurdy and Rhodes 56 with skeg rudder, not so much.
What About Backup?
But wait, any rudder can get damaged, and rudder loss is one of the most frequent reasons boats are abandoned at sea. That said, I think that the best practical answer is a drogue as a steering backup, rather than any sort of backup rudder.
Again, for those of you who were not in on earlier Adventure 40 discussions, it’s important to know that the Adventure 40 will be steered with a tiller, not a wheel.
Tillers have fallen out of favour in recent years, mostly because many modern designs have too high steering loads as a result of designing for large interiors rather than good steering manners under sail—think fat sterns to cram in big aft cabin(s).
I also suspect that a big reason for the dominance of wheels these days is that standing behind one gives us guys a feeling of power—women seem to be immune from such silliness. I often joke these days that buying a J/109 with her huge and cool-looking wheel means that I now don’t have to buy a motorbike.
When we design a boat that’s all about sailing, particularly a fairly small one like the Adventure 40, tillers make a lot of sense.
Here are some of the reasons:
- Much less expensive. In fact, the savings over a wheel, of several thousand dollars, will more than cover the costs of, for example, up-strengthening the keel-to-hull joint and the rudder.
- Removes the problem of designing the cockpit so that a crew member can get around the wheel without the dangerous, and far too common, need to jump up on the seat (see photo below).
- This in turn allows the cockpit seats to be longer for a given cockpit length, since on a boat with a wheel the only right way to solve the above problem is to cut the seats away in the way of the wheel—as J/Boats have done (really well) on the 109, see photo above—which on a boat the size of the Adventure 40 would almost certainly make them too short for comfortable lounging.
- Much easier and more efficient to use with a vane gear.
- If the tiller is hinged where it joins the rudder head, it can be lifted into a vertical position, thereby freeing the cockpit for entertaining or just generally moving around more easily.
- Much easier to design and install an emergency tiller.
- The fact is that most emergency tillers on boats with wheels are a joke that will never work in real life offshore, or at least not for long.
- Intrinsically more reliable than a wheel—far less to break.
- More effective and faster to move the rudder back and forth from lock to lock when manoeuvring in tight spaces.
- Frees up a huge amount of room in the aft end of the boat by removing the quadrant and associated cables.
- Removes the danger of a loose piece of gear fouling and jamming the steering gear, an all too common and dangerous problem.
- The underdeck parts of wheel steering gears should be completely boxed in to prevent this, but most are not.
- Much easier to reach the winches than from behind a wheel.
- I’m thinking the French team may opt for a main sheet system that leads to winches on the cockpit coamings (often known as a German or European system) and, if so, all sheets will be to hand without leaving the tiller.
- Way more fun to steer a boat with than a wheel. You have to experience steering a well-balanced tiller boat to get this, but I promise you it’s true.
As you can see, I’m a huge fan of tillers, but, of course, like anything, there are downsides:
- No binnacle to mount a cockpit table or engine controls on.
- Mounting the controls intelligently high up on the coaming pretty much solves the latter problem.
- When underway, the sweep area for the tiller must be kept clear, which reduces the number of people who can sit in the cockpit comfortably.
- If steering with a powerful underdeck autopilot, we must be careful that the tiller does not pin someone to a seat or coaming. This one is probably the biggest tiller problem, and one we will need to think about.
- Perhaps we can solve this by allowing the tiller to hinge up to vertical and lock, although that might cause mainsheet interference issues, depending on where Vincent decides to place the main traveler.
- If you have bright ideas to eliminate the risk, please leave a comment.
That’s all I can think of on the downside, so a clear win for a tiller.
Now let’s turn our attention to self steering.
The Adventure 40 will come standard with a vane gear installed. This is an unusual step these days, but in keeping with the mission of offshore cruising, and achieving that in the simplest way possible while spending money on construction quality not fancy gear.
That said, I know that there will be owners who will prefer to install an underdeck autopilot as well, so I would recommend that the Adventure 40 rudder shaft be designed and built to take an autopilot tiller arm, and a strong point be glassed in to take the other end of the autopilot ram.
It will also be important to make provision in the design for adding more batteries to the standard bank the boat comes with to support an autopilot.
Bottom line in all of this is that those thinking of an underdeck autopilot for their Adventure 40 should budget US$15,000 to US$20,000 for the pilot and electrical system upgrades to support it.
For the rest of us, who decide to keep that money in the cruising kitty, a simple tiller pilot will do when sailing inshore, when setting up the vane gear is too much of a pain, and when motoring (in or offshore), particularly now that there seems to be a quality option offered—if it were me buying an Adventure 40 that would be my preferred choice.
This article covers some big changes to the Adventure 40 as well as two differentiators from most all of the boats we see out there these days (vane gear and tiller). Let’s talk about it in the comments.
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