Boat handling: how to use your yacht’s hull shape to your advantage

Ask any sailor to explain the differing characteristics of hull shapes and they will be full of opinions about the advantages and disadvantages of one boat or another.

But these views are usually clouded by past experience and bias.

To a degree the vast array of opinions on offer about any given design choice support the need for such a variety of hull shapes, keel choices, rudder types and so on.

Every yacht ever designed is right for someone out there in the world.

Given these deeply held biases, it can be difficult to get accurate representations of what the compromises and benefits that come from certain boat designs actually are.

Taking a data-driven approach to this question can be a very difficult task indeed, so naturally YM set out to do just that.

We set an objective to take three types of boat, broadly reflecting eras of design, and put them through their paces on the water in an attempt to find the idiosyncrasies inherent in each design and measure them.

Although far from a comprehensive overview of all design options available, the three representative styles we settled on were: a long keel with keel-hung rudder, a medium displacement fin keel and skeg, and a modern, wide hull with twin rudders.

We felt these gave a representation of the broad direction in design over the last 50 years, though there are many permutations of hull and keel that were not included.

In an ideal world, we’d have three boats built to the same length at the same time, by the same designer with only the differences listed above to speak of.

However, our proposal for commissioning, designing, building and sailing three brand new yachts for a comparative test was inexplicably shot down by senior management, so we did the next best thing and called up three owners, each with different style of boat to come to Lymington for the day.

We ended up with a Contessa 26, Rustler 37 and Jeanneau 389, and took our chances with the weather.

Boat handling: The three yachts:

Jeanneau Sun Odyssey 389

High-volume hull with lift keel, twin rudders and sail drive

• Name: Windcatcher
• Owner: Flexisail.com
• Year: 2015
• Designer: Marc Lombard
• LOA: 11.75m/38ft 6in
• LWL: 10.40m/34ft 1in
• Beam: 3.76 m/12ft 4in
• Draught: 1.10m-2,25m/ 3ft 7in-7ft 4in
• Displ: 6,920kg/15,256 lbs
• Ballast: 1,769kg/3,900 lbs
• Sail area: 70 m2/754 sq ft
• SA/disp: 19.68

Rustler 37

Medium displacement, fin keel and keg-hung rudder

• Name: Andrilott II
• Owner: Tim Stevenson
• Year: 2016
• Designer: Stephen Jones
• LOA: 11.28 m/37ft 0in
• LWL: 9.07m/29ft 9in
• Beam: 3.76 m/12ft 4in
• Draught: 1.91m/6ft 3 in
• Disp: 8,845kg/19500 lbs
• Ballast: 3175kg/7000 lbs
• Sail area: 81 m2/ 871 sq ft
• SA/disp: 19.31

Contessa 26

Long keel with keel-hung rudder

• Name: Brizo
• Owner: George Smith
• Designer: David Sadler
• Year: 1965
• LOA: 7.77m/25ft 6in
• LWL: 6.10m/20ft 0in
• Beam: 2.29 m/7ft 6in
• Draught: 1.21m/4ft 0in
• Disp: 2,449kg/5,400 lbs
• Ballast: 1,043kg/2,300 lbs
• Sail area: 22m2/244 sq ft
• SA/disp: 12.15

How hull shape affects boat handling: methodology

Our aim was to try to make comparisons between the styles of boat without comparing the boats themselves.

Our interest was not in finding out if a Contessa 26 outpoints a Jeanneau 389, rather trying to get to grips with the key characteristics of the different styles, what they delivered in data, and also to evaluate each style of hull with as unbiased a gaze as we could muster.

Sailing the boats against one another is always going to be difficult as the sail setup and rig has such an impact on performance.

For the sailing portion of our test we chose to measure each boat’s apparent wind angle; apparent wind speed; compass heading; course over ground; and speed over ground, both up and downwind. We also set out to record heel and pitch, but in the light airs, these numbers weren’t that revealing.

This data should give an idea of how each boat was performing in the conditions and to see how close-winded each boat was and what their relative leeward drift might be.

For other factors we were more subjective and based it on how we felt each boat performed.

For the manoeuvring both in open sea and a busy marina, the data should be less subject to other forces and should give a better steer as to the differences inherent in the design choices of each boat.

How the boats sailed

On the day of our test, the NNW wind was light – in the high single to low double digits all day – and coupled with a flood tide, gave a very flat, wind-with-tide sea state.

Long, slow upwinds, and downwinds dominated by a significantly reduced apparent wind as the tide washed the boats toward our leeward mark were the order of the day.

YM editor, Theo Stocker, and I rotated through each boat noting the data, upwind and downwind, and trying to get a feel for the performance of each boat.

Downwind

Clearly sacrificing so much waterline length to the other two boats, the Contessa 26 was always going to struggle in terms of outright pace.

Boat speeds were surprisingly close, however. Clearly in these conditions none of boats were reaching hull speed, so all the boats were being blown directly downwind at a relatively even speed.

Additionally in the light winds, the Contessa almost certainly benefitted from less wetted surface area than the other wider, heavier hulls.

Sailing under white sails, we decided to test each boat goosewinged dead downwind and then on a deep broad reach, replicating an easier downwind course.

In these conditions, the speed over ground for each boat is almost identical downwind.

Continues below…

Thanks to the conditions, none of the yachts could really pick up their skirts.

Downwind it was surprising  that the Jeanneau was slower to accelerate than the other boats and was, in most conditions, closer to the Contessa than it was to the Rustler, despite having the longest waterline.

Clearly the wide hull, winged stub keel with swing keel extension and the twin rudders increased wetted surface area and drag, which was significant.

She also offered less feedback through the helm, with response to helm inputs being less clear, making her less positive to steer and respond.

Though it is not reflected in the table (below), there were enough moments that the Rustler struggled to get as deep as the other two boats, possibly due to her large main blanketing the headsail, that we concluded she certainly felt more comfortable sailing a slightly tighter angle under white sails alone.

Upwind

It’s worth noting that in the table (below), the Rustler was sailing in much lighter conditions than the other two boats, so though her speed is broadly within the range of the Jeanneau, she was clearly the fastest on the water.

As the data shows, the wind was oscillating through a significant range, and thus the angle of tide as compared to heading varied too.

This does give us some difficulties in terms of making hard and fast statements.

What is clear, however, across all the data is that the Rustler had the least leeway consistently, presumably a product of dynamic lift from her keel.

It is probably less of a surprise to see that the Contessa was losing little leeway when the tide was not a significant factor, but the large surface area of her keel possibly left her more at the mercy of the tide.

It was surprising to analyse all of the data and see the Rustler losing much less leeway across all the upwinds, as on the water, and anecdotally we all agreed that the Contessa had felt much more close- winded than the Rustler in particular.

The Contessa may have benefitted from being sailed slightly freer, but it could be a symptom of her keel shape.

Where the Rustler should be sailed at pace, allowing dynamic lift from the keel to help the boat to windward, the Contessa would lose less ground to leeward as a product of inherent drag but made up for this through being closer winded.

The drawback for the Contessa, of course, being the benefit from her keel in terms of leeward drift becomes her achilles heel in terms of tidal drift.

For her part, we all agreed that the Jeanneau sailed similarly close to the wind as the Rustler, but was also consistently closer winded on starboard – either a factor of the tide, or her instruments needed calibrating.

With little feedback through the helm in these light conditions, she was hunting for the breeze a little more and rarely felt in the groove. It could be this that caused the Jeanneau’s results from the day to offer the highest rate of discrepancy in her numbers, a feature we saw throughout all the data sets.

There are two conclusions to draw from this. Firstly, were it my boat, I would be having a good look at setup in terms of rig tensions, how vertical the mast is and the like.

Secondly, it seems relatively clear that in these light winds the boat just does not perform all that well.

Her wide transom and twin wheels require a little more breeze to develop heel before she would be likely to pick up her skirts and really get going.

Boat handling: how the yacht sailed

Contessa 26

This was the most close-winded on test, but with a slower hull speed and large keel, was most affected by the tide.

Surprisingly quick particularly downwind in the light weather, a product of narrow hull shape with less surface area and the light winds not allowing the other boats to use their length and reach hull speed.

Jeanneau 389

Twin wheels and rudders damped the feel on the helm in light winds. As such she was hard to sail in her groove.

We’d expect her to perform much better in more breeze, so she could exploit her more powerful hull shape.

Rustler 37

Despite her heavy displacement, pointing to a boat designed to perform well in heavy seas, she sailed very well in light winds and for a medium displacement boat is much more easily driven than similar boats of earlier decades.

Needed to be sailed reasonably free to get the best from her.

Felt slightly less comfortable than the other two sailing very deep downwind, though with time to pole out her headsail and set up for a long passage this might be less of an issue.

Boat handling and manoeuvring

Boat handling: Heaving to

Our first manoeuvring test for the day was to set each boat up hove-to, in order to get some sense of how each might perform.

The results were relatively surprising in their similarities.

All boats behaved similarly in terms of their leeward drift, here defined as SoG.

There was a difference in how the boats lay relative to the wind, and thus how comfortable they may feel in a seaway, but we were expecting to see larger disparities here than we saw in general.

Boat handling: Carrying way

With sails down we started with some open water tests, firstly motoring in a 360° circle with engine a touch over tick over to see how quickly she would spin.

Then motoring at 4 knots, we dropped into neutral and let go of the helm.

We timed how long it took each boat to decelerate to 2 knots while also measuring how much each deviated from their course without helm inputs as it slowed.

We were not too surprised to see that the Contessa required more relative space in order to complete her turn. Without a central keel to pivot around, she is always going to struggle.

It also seems relatively clear that she completed her manoeuvre quicker than the other two thanks to being significantly smaller and lighter and thus responding more quickly to engine input.

Perhaps the most surprising outcome from this test, in fact, was that of the Jeanneau. We tried the circle with both keel down and keel lifted and her time to complete the manoeuvre and the distance required were almost identical.

As for the momentum test, we conducted this into a 5-knot headwind and into tide. The relative weight of the Rustler is clear, both taking longer to slow and deviating the least.

The Contessa was a surprise in just how much it deviated from course with no helm input. We had assumed that the long keel would offer the best directional stability.

Given that the Contessa had offered impressive directional stability in the sailing tests, this was clearly only an issue without the sails up.

Ultimately, we believe – and have spoken to a couple of boat designers who agreed – that this is a product of several factors.

Essentially much of the boat’s lateral resistance is well aft with a long forefoot ahead. This could be working to almost trip the boat up over herself.

Secondly, with this lateral resistance aft and relatively more weight aft once the boat does start to turn, which is relatively easy with little bow drag and significant aft drag, she can end up offering more and more keel to the turning force of the water as she turns, further accelerating the turn.

With sails up and driving or engine in gear there is more water flow over both sides of the keel to remove this problem.

Boat handling: In harbour 

Manoeuvres around the Lymington Yacht Haven pontoons did throw up possibly the most significant differences.

Though trying to be as data-driven as possible, it is difficult to go into these situations without some preconceptions and I was expecting the Contessa to be the trickiest of the three boats to steer in tight situations.

In order to see how the hull and rudders performed on a twin keel boat, we opted not use the Jeanneau’s bow thruster.

This is perhaps a little unfair then, but does show more clearly the impact of hull design, ignoring additional manoeuvring aids – the Rustler 37 did not have a bow thruster fitted.

Boat handling: 180° turn 

Each boat entered a narrow gulley between pontoons, performed a 180o turn and then motored back out, and repeated turning both ways.

The Contessa managed her starboard turn in a single shot, without any adjustments of the helm or engine, though this is more a measure of her relatively short length.

Even when she needed to go astern, the Contessa performed similarly to the other two boats in terms of number of helm and engine inputs and time taken.

The Contessa did take longer to come round with the helm hard over, but there was always an indication she was starting or ending a turn.

She gave plenty of warning that she was starting to turn and so was not at all alarming. In astern, we did not see a significant amount of prop kick from the Contessa, which we had been expecting.

The Rustler, though requiring a larger space to turn, felt controlled and deliberate. Keeping the speed low was the order of the day, with a light touch on the wheel and throttle and allowing enough space to complete her turn, largely thanks to her heavy displacement.

However, her combination of fin keel and single rudder meant she was very predictable, and controlled even at low speeds, making her manageable even in confined waters.

The Jeanneau, particularly without the use of the bowthruster required a particularly brave and steady hand on the throttle.

Here, the twin rudders really did work against her.

Stick a bit of throttle on and even with the wheel hard over, but without direct prop wash over the rudders there is little reaction until the boat has almost 2 knots of way in order for the rudders to provide positive steerage.

This means that, although she conducted her turn in a similar time and in a slightly smaller area than the Rustler, some of the sections of her turning required significant pace, heading in the direction of other moored yachts before the steering would kick in and she would veer away.

In anything other than benign conditions, the bow thruster would be fairly indispensable.

Boat handling: Steerage astern

Remaining within the pontoon berths we wanted to test how long it took each boat to have positive steerage astern from a standing start.

We conducted this test both stern to and away from the wind. The results show the relatively higher boat speed the Jeanneau needs before she gets positive steerage.

It is also worth noting that with bow into the wind, (as with the momentum test performed previously in the day) the Contessa once again picked up a significant course deviation.

Boat handling: Springing 

Our final test of the day was to look at springing off a pontoon with the engine ahead and then turning round (in an attempt to be working against the wind) and trying the same thing with the engine astern.

We timed how long it took until each boat had sprung out to its maximum angle and how big that angle was.

Here we were expecting a degree more variation from boat-to-boat. Ultimately, though, we found that all the boats can spring off, but for different reasons.

The Contessa and the Rustler had prop wash and could use this to lever their stern out, whereas the Jeanneau did not have the benefit of prop wash, but its width and resultant distance of prop off the pontoon gave it more simple leverage.

Springing back in was the tell for this – the single rudder boats could use prop wash to push the stern back in, but the Jeaunneau’s twin rudders could not do this.

In the Jeanneau, if you want to drive your stern in, in an offshore wind, you will need to warp in, or put her stern in first, then use the bow thruster.

How the boat handled

Contessa 26

• Much more receptive to helm input astern than we imagined.
• Drifted furthest off course in both the momentum and motoring astern tests. Lateral resistance of the keel well aft probably responsible for this without drive from engine or sails.
• Had largest turning circle.

Rustler 37

• Responded well when manoeuvring at low speed.
• Her mass meant she was somewhat slow to manoeuvre but was the most deliberate in her response.

Jeanneau 389

• Relatively lightweight and twin rudders require active engine control.
• Occasionally unpredictable until moving at pace.
• Not able to spring back in under prop alone.
• A bow thruster (fitted but not used for the testing) does much to relieve all of the above.

Get to know your yacht for better boat handling

The biggest surprise was how similar the data from three different designs were.

The gulf between the boats lay rather in the way they needed to be handled to achieve similar results.

With each of the skippers familiar with their boats’ quirks, the same tasks could be completed, but knowing how much to sheet in, put the helm over or push the throttle was the key.

The Rustler clearly had the best pace upwind and only needed to foot off a little compared to the more closely winded Contessa, but this pointing difference felt significant onboard.

The Jeanneau lacked pace in light airs, but this should improve as the wind builds.

We had hoped to measure heel and pitch, but in light airs and flat water, this wasn’t possible.

How the boats feel in a seaway would help separate the designs further.

In harbour, we expected the long-keeled Contessa to be more of a handful manoeuvring astern under engine, but she was relatively well behaved and took a similar time to turn as the other two, though of course she is much smaller.

While the Contessa’s long keel gave her a mind of her own astern initially, as long as she had a little way on with the occasional nudge of the throttle she was entirely predictable. The Rustler also rewarded factoring in prop walk.

With a sail drive, the Jeanneau did not suffer from much prop walk, but lacked steerage under two knots, which would be enough to fray nerves on a windy day.

Better to line up using the bow thruster, then go for it.

Close quarters is much less stressful at one knot than at two knots, and mitigating for a lack of low-speed steerage requires forethought.

Understanding how long it takes your boat to achieve, and lose, steerage and what she will do before then is key to mastering your boat in harbour.

Harness what your boat wants to do naturally rather than fighting against it, and boat handling becomes much less stressful.

With thanks to Royal Lymington Yacht Club, Lymington Yacht Haven, boat share membership company Flexisail.com and all the owners, crew and rib driver who helped make this article and photoshoot possible.

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