In the first of our Cruising Clinic series, Rachael Sprot steps aboard to help Tracey Hindmarsh and her crew improve their pilotage skills to explore with confidence
Pilotage, like many sailing skills, is both an art and a science.
Successful pilotage relies on accurate planning and calculations but also on having a feel for where you are.
I joined Tracey Hindmarsh, owner of a Bavaria 32 based in Queen Anne’s Battery, Plymouth, to see if I could help her improve her pilotage skills and move them to the next level.
Tracey and her husband, Nick, have owned Solid Aire since 2018.
They usually cruise out of the harbour – across to Cawsand Bay, over to the River Yealm or west to Fowey.
They’ve both crewed extensively abroad on larger boats, including trips to Norway, Svalbard and Cuba, but they admitted that the inner reaches of Plymouth Harbour remained unfamiliar territory.
Improve our Pilotage skills to explore with confidence: Diagnosis:
Her choice of cruising destinations suggested that she was sticking well within her comfort zone and needed some gentle encouragement to step outside it.
I set her the task of piloting us up the drying River Lynher inside Plymouth Harbour to see if we could set her back onto the slopes of the learning curve.
Also on board was experienced crew member Erika, daughter Abigail and grandson Arlo.
At less than a year old it was Arlo’s first time out on the boat and as it coincided with afternoon nap time a smooth execution was vital!
Lying six miles from the marina, Dandy Hole is a deep pool surrounded by rolling fields and wooded slopes.
It’s a much hallowed spot amongst the local cruising community and a world away from the shipyards of the Tamar, however, at low water it’s completely surrounded by mud.
This provides an impenetrable barrier and a perfect pilotage exercise for aspiring Yachtmasters.
Tracey quickly identified the key information: it was Springs, HW Plymouth was 1906 BST and there was very little difference in the tide times and heights at the River Lynher.
She approximated that we’d have enough rise of tide by late afternoon.
She had good instincts, but when I pressed her about how she’d arrived at the late afternoon timing I felt that her broad brush approach was masking a reluctance to tackle the technical details.
Rule of Twelfths vs Tidal Curve
Tracey had used the Rule of Twelfths to work out the tidal height.
This rule breaks up the six hours between high and low water and states that for each hour a certain proportion of the overall tidal range is gained or lost.
It’s a quick to use if you’re numerically minded:
Work out the range by subtracting the low water height from the high water height
5.6 – 0.7 = 4.9m Range
Divide the range by 12 to work out your twelfths
4.9/12 = 0.41m
On a flood tide work out the number of twelfths for each hour of tide towards high water, multiply that by 0.4m and add that on to the low water height.
The indication is that we’ll have a 4m height of tide before 1700. However in many areas the way that the tide moves in and out won’t match the rule of twelfths model.
This is true in places like the Solent or Poole Harbour, which have complex water movements and lopsided tidal curves.
But even in a harbour such as Plymouth, where a tidal calculation is critical, you should use the proper curve.
It was surprising to find there was almost an hour’s difference in calculations: on the tidal curve we predicted we’d have 4m at 1606, rather than just before 1700.
If we’d relied on the Rule of Twelfths we’d have had to wait an extra hour to make our approach.
It’s better to undertake pilotage exercises on a rising tide, with a generous tide remaining. If you do go aground, there should be enough rise left to get off again
Required height of tide
To establish when you can access any shallow area, first you need to identify how shallow it is.
In this instance the final approach to Dandy Hole dries to 1m.
To calculate the rise of tide required to transit this hump, we need to follow the following formula:
Height of tide required = Draft + Safety Clearance + Charted Drying Height
or if the shallows don’t fully dry:
= Draft + Safety Clearance – Charted Depth
In this case we had a 2m draft, we wanted a safety clearance of 1m and we had a drying height of 1m, and had a drying height of 1m, so in total we needed a 4m rise of tide.
Making a pilotage plan
With the approach time calculated we then needed a pilotage plan. This stage involves close scrutiny of the charts to identify hazards and develop an avoidance strategy.
I recommended that Tracey did the exercise without the chartplotter to hone traditional skills whilst she had the support of an instructor on board.
I’m normally a firm believer that skippers should use all available means, including navigation apps and GPS – I wouldn’t want to explain to an insurer that the plotter was turned off when the boat ran aground… In training though, it’s useful to flex the muscles of traditional navigation which are often neglected in our digital age.
The buoyage up to Dandy Hole is frugal but adequate.
Tracey drew the distances and bearings between marks onto the chart and wrote them into her notes.
I showed her a diagram I’d made earlier which is my preferred planning technique.
A sketch map gives you something to hand in the cockpit whilst your charts remain safely below, but for me it’s more the process of making the plan that’s important than how polished the product is.
Reading a chart properly is time consuming, so by carefully identifying each hazard and feature in advance you’ll become familiar with the route and be able to spend more time on deck once underway.
Ultimately how you make a pilotage plan is up to you, but it should include the following information:
- Minimum under-keel clearance expected
- Identification of hazards and the avoidance strategies you’ll use (staying within a buoyed channel, clearing bearings, transits, minimum depth, distance off etc.)
- Details of the route with bearings, distances and important features highlighted along the way
- Any local regulations
- VHF channels to monitor
The final preparation we did was to focus on scale. Scale is often overlooked in chartwork, but it’s key to understanding how things will look in real life.
I asked Tracey how far off the bank we’d be once we’d dropped the hook. The deep water anchorage at Dandy Hole is half a cable off the southern shore.
Most of us couldn’t gauge half a cable by eye so we need to relate it to something closer to home: boat lengths.
A nautical mile is 1853m, so a cable is 185m, call it 200m for ease. Half a cable is 100m, so 10 boat lengths in a Bavaria 32.
Once we’d brought the scale home to a perceptible level, she could start to visualise what this new place would be like.
We set off in glorious sunshine and apart from negotiating the set of three chain ferries at Torpoint, the pilotage up the lower part of the Tamar was straightforward.
We arrived at the mouth of the Lynher a little early and picked up one of the empty moorings for a quick brew and a briefing from Tracey.
Once underway in the river there was a strong flood tide which swept us along at 6 knots over the ground.
Tracey had a tendency to spend slightly too long below decks checking the chart, probably because we hadn’t allowed enough time for the planning process that morning.
In a narrow channel it’s important not to take your eye off the ball, especially if travelling at speed, so I suggested we slowed down.
Approaching Sandacre point one of the first things I noticed was that neither Tracey who was in the companionway or Nick on the helm, were focused on depth – they were both absorbed in finding the next mark.
The location of the echosounder low down on the helm station didn’t help. This was rectified by asking Erika to call out critical depths.
The headings that had been plotted between each mark were helpful given the long distances between buoys and large expanse of water in which to find them.
However, in the early stages Nick obediently followed the compass and we encroached quite close to shore. I had to ask him to bring us back into deeper water.
Headings must not be relied upon in a narrow channel– any inaccuracies can be critical at this scale, whether that is of the helming, the original measurement or the position within the channel that you started from.
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Furthermore, it doesn’t take much of a cross wind or tide to set you off track. Use a heading as a rough guide and then ‘eyeball it’ to adjust for all the real-world factors.
In today’s modern yachts with fin keels and matrix constructions you need to be particularly vigilant about groundings.
Repeated minor impacts can cause structural damage and even keel failure.
This was tragically demonstrated by the loss of Cheeki Rafiki and her crew in the North Atlantic in 2014. Having a well-calibrated echo sounder is essential.
There was no lead line on board and although Tracey was confident of the sounder’s accuracy, they should invest in one or make one themselves.
Depth is a key indicator of position in a narrow channel and one that’s often overlooked during a busy approach. Tom Cunliffe’s advice in the Shell Channel Pilot is to ‘feel your way up’ the river.
This means keeping a constant eye on the echo sounder and reacting quickly to unexpected readings.
Dot-to-dot pilotage doesn’t work in a tortuous river: you need to add in the nuances of the contours by asking the helm to gradually come around towards the next mark instead of going straight there.
Using a distance off is also a useful technique – give instructions such as ‘Stay within 10 boat lengths of this bank, it’s shallow further off,’ or, ‘Stay a couple of boat lengths off that mark, it dries out.’
Skippering techniques for pilotage waters
Communication and delegation are the foundations of good leadership, which is no less important during pilotage.
The skipper needs to describe the route so that the helm isn’t just blindly following instructions.
Tracey regularly checked in with the crew, explaining that we’d need to alter course shortly but not until we reached a certain point.
Precise instructions such as, ‘Turn 30º to port if the depth drops below 2m,’ give the crew agency and take the pressure off you as a skipper to be juggling all the balls yourself.
She was also good at double checking herself and not jumping to assumptions.
As the most experienced person on the boat it’s essential that a skipper is their own critic.
Although too little confidence can be disabling, I’m a firm believer that it’s the voice of doubt which keeps us safe.
Pilotage is a dynamic process: we need to assess the information around us constantly, ensuring that the depth is as expected, that we’re well positioned within the channel, actively reading the landscape, matching it to the chart and monitoring current when passing a fixed object.
As soon as things don’t add up, it’s time to stop and reassess. We made it over the shallowest point with a whopping 2.5m under-keel clearance – much more than expected.
The difference was probably due to a few factors: we were half an hour later than expected; we’d planned for the worst-case scenario which was a 1m drying hump that we’d probably skirted around; and there was some discrepancy between the minimum depth on the Admiralty chart and on Navionics.
The Navionics showed more water in the final approach, so perhaps the paper chart was slightly out of date.
Recording the actual minimum depth is always useful – write a note on the chart to inform any subsequent visits.
Dandy Hole was soon conspicuous thanks to the handful of deep draught boats anchored on the outside of the tight meander.
There isn’t much space in the pool, so if you’re thinking of spending the night it would be worth checking on AIS to see how busy it is before setting off.
But it is worth the effort: the wonderful backdrop of the St Germans viaduct is the only sign of civilisation.
Our most important crew member clearly approved of the location’s seclusion: baby Arlo was sleeping soundly. Tracey could breathe a sigh of relief, her grandmother and pilotage duties were well and truly complete.
Pilotage Lessons Learnt
Invest time in the planning stage so that you’re free to be on deck once the pilotage starts.
- Always allow a generous safety margin in unfamiliar waters.
- Good communication is key, especially between the helm and the navigator.
- Don’t rely on the compass: the compass is king when passage-making, but pilotage is the realm of the echo sounder.
- Check your echo sounder calibration with a lead line.
- You don’t necessarily need to go far from home to try something different.
Prescription: Tracey’s skippering style is calm and effective. She had good command of the boat and crew and coped well with the pressure of the pilotage exercise.
Most skippers would baulk at juggling the demands of an instructor, Yachting Monthly photographer and young grandchild, but she took it all in her stride.
She was an active navigator, always looking ahead for the next mark and double checking herself as she went along.
Like many boat owners with limited time for cruising she’s slightly stuck in the rut of the old routines.
Her theory was quite rusty because she hasn’t needed to use it.
Despite that I’m confident she would have found her way up to Dandy Hole without me.
My prescription is to throw in a few new places into her cruising repertoire.
The Tamar, the River Erme and Polperro are all interesting places to explore within easy reach of Plymouth.
This will push her to employ those technical skills which fade with time and give her the confidence she needs to move her skippering to the next level.
Thanks to: Royal Western Yacht Club for providing the RIB and University of Plymouth Yacht Club; Bertie Sorensen-Pound for driving; Queen Anne’s Battery Marina for the mooring for the day.
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