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  • Writer's pictureTom

Too close for Comfort: Tonga to New Zealand via Minerva reef

Updated: Mar 31

Skyfall flying the New Zealand Flag and Q flag prior to entering the By of Islands
Skyfall flying the New Zealand Flag and Q flag prior to entering the Bay of Islands

The final leg of our 2023 season, the passage from Tonga to New Zealand, was potentially the most difficult one of the year. Instead of being blown along by the southern trade winds, we must head south into areas where the winds are determined by weather systems emanating in the Southern Oceans. Low pressure systems regularly form over Australia or the Tasman sea and, as they pass over NZ, can generate storm conditions with 7m waves and 40+ knot winds (see GRIB below). The worst thing to do is to get caught out off the NZ coast and hammered by one of these. It takes circa 10 days to sail from Tonga to New Zealand and these lows appear with a frequency of every 5-10 days!

GRIB  file showing low pressure hitting the northern tip of New Zealand
GRIB file showing low pressure hitting northern New Zealand (Different colours indicate different wind strength. Blue is no wind. Sailors like to sail in 'green and orange', red is problematic and dark red is very bad)

The sailing time can be reduced by sailing from Tonga to New Zealand via Minerva reef. This unique lagoon sits in the middle of the Pacific circa 800nm from New Zealand. Leaving from Minerva, the required weather window is only about six days. The reef has now become so popular as an interim stop that it is now nick-named 'The parking lot'!

We decided to employ the services of John Martin, a sailor and meteorologist, who is one of the premier 'weather routers' for the South Pacific. We would report position, speed and conditions and we would get daily 'general' instructions as to which direction to point the boat. It turned out to be a very wise investment.

Sunrise over Nuku'alofa anchorage
Early morning departure from Nuku'alofa

We left Nuku'alofa on Friday early. The sun was just beginning to rise over the anchorage. Minerva reef was around 280nm away. The first day, we were close reaching in good wind and managed 160+ nm. The second day the wind died out, although we ended up getting within 50nm before turning on the engine. We regulated our speed to arrive at the reef at first light on Sunday. It was a windless morning and the sea was almost glassy. At around 3.5nm we got our first sighting; the mast of a yacht anchored there. Searching closely, I then persuaded myself that I could perhaps see waves breaking. At 2nm the reef was obvious, although we were probably within 1nm of the entrance before I was satisfied that I knew where we were going. The GPS waypoints in Navionics were spot on.

There is only one area within the reef where you can anchor: the south east corner and north of it for around one mile. Most of the rest of the reef is 'foul' with rocks and bommies. Fortunately, there is no problem (obstructions) sailing (or even tacking) across the reef to the anchorage. The 'book' advises anchoring in around 10m. Go shallower and the sand is thinner and holding less certain. We found large areas of sand and only isolated, small bommies so anchoring was easy. There is space for 40+ boats, although the 'prime' position is in the SE corner where the reef is higher and protection from E, SE winds is slightly better.

We spent Sunday morning doing boat jobs before retiring for a few hours sleep. The front was due to pass through that night so, in the afternoon, we discussed with the only other boat there, Gary (SV Manxman), our best options. As the front moves through, one should expect 15-20 knots from the north west, swinging around to the south west. In those conditions the anchorage is on a 'lee shore' (wind blowing you onto the reef, not away from it). Even though the 'fetch' across the lagoon was only 1.5-2nm, this is enough to allow a swell to build up. We would be in for a 'bumpy' night. As it is not possible to anchor on the western side we moved a bit further from the reef, anchoring in13m and let out a lot of chain. To quote Gary, 'If it is in your anchor locker it ain't helping you'. Gary joined us for food and a game of cards. He was most anti-social, winning all the games. In these situations Annick's solution is to introduce different Belgian card games, preferably ones where the rules change on every round (and with the weather if she is really losing). But it did not help. He just kept winning.

In the middle of the night the anchor alarm went off. As we get older our reaction times and speed of movement get dulled - except when the anchor alarm goes off! In a flash I was on deck assessing what had happened. False alarm. I had just forgotten to increase the allowed movement for the excessive (70m) amount of chain used. As the wind had moved from NW to SW the boat had swung around, moving more than the permitted 40m I had set. The anchor was rock solid. The holding is excellent.

Monday morning was rather windy and we stayed on the boat. Our priority was to talk with John, our weather router, and to understand when we might get a weather window. Before we left Tonga we knew there was a weather front coming through on the Sunday evening. The usual strategy is to wait a few days and depart as soon as the wind is in the south. Then we should have a nice sail (heading SW with the wind backing further on subsequent days) For us that would have been Thursday evening or Friday. John dashed those hopes. There was a new 'nasty looking' low developing over Australia which was expected to cross the Tasman sea and hit New Zealand late the following Tuesday. If we left Thursday evening or Friday then we would not have time to get to NZ before that low. And we did not want to be hit by a weather system as shown above. He suggested we would be waiting around 10 days for the next opportunity of a 'good weather window' unless....

The alternative was to leave almost immediately (the next morning), knowing the waves would initially still be large (almost 4m) and we would be sailing straight into them. As time passed the wind would diminish and we would be light wind sailing (upwind) supplemented with a decent amount of motoring. Far from ideal. We discussed Skyfall's fuel reserves and motoring range and there seemed to be margin. Annick had booked a flight home on November 2nd and she would likely miss it if we waited. So we agreed to leave on Tueday early. John had defined our inital route with an 'Aim Point' (longitude and latitude). Our passage to New Zealand, including a ‘dog leg’ to the west, totalled 840nm from Minerva. We had seven days to do it and therefore needed to average 120nm each day, or an average speed of five knots.

The first day, we were expecting 11-16 knots of wind. Although close-hauled, according to the forecast we should have been able to point within 20 degrees of our Aim Point. The next day was going to be motoring and we could correct then. This is not what we experienced. Instead, we had only 8-12 knots and the wind was 'bang on the nose'. We would be tacking all day. With the large waves and light airs we had to sail free to keep the boat moving. Averaging only 4-5 knots through the water and having to do almost double the distance as we zig-zagged upwind, after fourteen hours we were only 40nm closer to the Aim Point. Before the day was done Gary, on SV Manxman, gave up and turned round to sail back to Minerva Reef. Two days later, it became clear that this would have been the safest decision and we were wishing we had followed his lead!

Skipper geared up for a cold evening watch
Skipper wrapped up for a cold evening watch

As the afternoon wore on, the temperature dropped. The contrast with the months spent closer to the equator was absolute. At night we needed thermal underwear, shirt, fleece and sailing jacket and trousers. We had not worn so much since - well I cannot remember when.

By 20.00 the wind was even lighter and, to get close to the daily average, we turned on the motor. The recommended cruising speed for our Volvo Penta is 2000-2100rpm. The ‘official’ diesel consumption at this rpm is 3.8l/ hour but, in reality, it is somewhat worse. With a 450 litre tank, we assumed a slightly conservative 4.5l/hour or 1% per hour. It was relatively certain that we would be able to sail the last 280nm but that still left 520nm to cover, mainly motoring but with uncertain opportunities to sail. Assuming these opportunities did not materialise then, averaging six knots we would need 87 hours motoring, consuming 87% of a full tank. And we left Minerva with 84% of a tank. We really did need to find some wind and do some sailing!

Wednesday morning the stress levels increased. The speed at which we motor depends on the sea state and headwind as well as the rpm. Instead of six knots, Skyfall had only averaged five knots through the night. The heavy swell (still 3.5m) left over from the front was slowing us considerably. At this speed, with 470nm left to the Aim Point, we would need 94% of a tank to reach the expected wind for the last stretch. But now we only had 75%. The 'gap' to cover with uncertain spells of sailing had grown to 21%. We discusssed this with John and we studied the table of fuel consumption versus rpm. Generally you get better mileage if you go slower. We agreed to run the next 24 hrs at 1700 rpm, aiming to average 4.5 knots and consume 0.6% per hour. The poor first day (95nm) and this slower speed would take away all our ‘reserve’ time margin to beat the ‘nasty low’ developing over the Tasman sea and due in NZ late Tuesday or early Wednesday. But, in principle, we should be OK.

Thursday morning arrived and we had now travelled slightly less than 200nm from Minerva in 48 hours. Only 360nm to go to wind. Fuel consumption had dropped dramatically and I had 64% left. Unfortunately, we had just hit an adverse current and we were now only doing 4.1 knots through the water. However, even at 4 knots that meant 90 hours motoring and with the lower fuel consumption at lower rpm we had the range. In addition, with the new forecast, there was now a good chance of some sailing on Friday. Therefore, before our communication with John, I felt encouraged. John’s reaction killed that optimism very quickly.

The slow speed was a huge problem. Firstly, by arriving later than planned at the Aim Point the expected wind might not be as favourable. Secondly, we would likely not get in before the storm. He was clear that this current plan would not work. Period. The options were to either return to Minerva reef or…. Well he would have to work on that!

After an hour of extensive modelling, two emails and three phone calls we had a new plan. John had told us that he was currently dealing witth forty seven yachts either on passage or waiting a weather window. Forty seven skippers expecting answers. It was comforting to know that, when we needed it, John was prepared to invest so much time in finding a solution for us. (It was rather less comforting to realise that he felt our predicament warranted such a high percentage of his time!)

grib of high pressure north of NZ
High pressure north of NZ; The old plan (O) was to follow the wind around the high. The new plan (N) was to motor straight across it

There was a large high pressure system sitting North of New Zealand. There is wind outside the big, flat, centre of the high and this wind circulates anti-clockwise. A sailor would normally aim to stay on the sides or ‘slopes’ of the high which have wind and ‘follow the wind' anti-clockwise around the high pressure zone. This had been the original plan (marked 'O' in diagram above). But the distance is significantly longer than the direct route and we were out of time.

The new plan (marked 'N') was to head directly for Bay of Islands (once we had cleared the adverse current). This took 50nm off the distance (which saved 9 hours) and 20nm off the distance needed to motor before we got to the wind on the ‘other side’. John also wanted more speed, 2000 rpm minimum. We would be back to fuel consumption of 1% per hour. Crucially though, the waves were reducing and Skyfall should start to make more speed for the same rpm. -At least, as soon as we got out of the current. So now we had 340 nm before we found wind. At 5.5 knots that was 68 hours or 68% of our fuel tank if we motored all the way. We had 64%. However, it was now clear that we would be able to sail on Friday,on the northern edge of the high. Therefore, if we assumed we could sail 44nm on the ‘slopes’ as we entered the high, then motoring time became 60 hours (or 60% of the tank).

So assuming,

a) we really could do 5.5 knots at 2000 rpm

b) Friday sailing materialized

c) we found wind on the other side of the high at the new Aim Point

d) there was no error in the fuel guage

then we would make it to New Zealand with a few fumes left in the tank to dock the boat.

If we failed? We would be stuck off New Zealand riding out a storm with 40-50 knot winds and 7m waves in conditions similar to those depicted in the top 'GRIB' file (diagram depicting wind). Over two days into the passage, and it was still too close for comfort.

We took the decision to go for it. Increasing the rpm to 2000 rpm, Skyfall’s speed increased to – only 5.1 knots! Time to take a deep breath. We were still in an adverse current. We should wait until dinner time to re-evaluate. All afternoon we plotted our speed. Gradually, remorselessly, the needle edged up first to 5.5 knots (by teatime) and later 5.6 knots. Crucially (I believe), the new routing kept us further east. The waves and swell were decreasing, not just due to the weather and time since the last front had gone through, but also because New Zealand has a ‘shadowing effect’ on the waves and there are usually smaller waves further east when the wind is in this direction. It was still ‘nail-biting stuff’ but maybe, just maybe this plan would work.

Then Friday happened. In a good way.

The wind arrived at 02.30 and the sails went up. We motor sailed (low rpm so low fuel consumption) the first two hours, sailed for ten more, then motor sailed for another two in the fading wind as we approached the flat, 'no wind' centre of the high. In fourteen hours we had sailed 84nm closer to the 'other side' and used very little diesel. Further, by sailing fast (we averaged almost 6 knots), we had saved time, allowing us to motor more economically if required. We now had only 200nm to motor. At 5.5 knots that would be 36 hours or 36% and we had 45% left in the tank. The situation had been transformed and we knew we would not now run out of fuel.

Consequently, I slept much better that Friday night. Further, by Saturday it became clear that, without the adverse wind and waves, at 2000rpm we could motor at close to 6 knots. We did not need to go that fast so, by mid-morning I had throttled back to 1800rpm to reduce fuel consumption. We found enough wind to turn off the motor just before midnight. Instead of running out, we had reached the wind on the 'other side' with almost 20% fuel left!

In Nuku'alofa we had provisioned for 7-10 days on Minerva reef. We had left after two days. We were aware of the biosecurity rules entering New Zealand and it pained me to think of good food (meat, eggs, fresh vegtables) going in the bin. Since Friday I had started adding a cooked breakfast of bacon, eggs, sausage and tomatoes after completing the early morning report to John and before Annick surfaced. Then, around 10.00 we would have the healthy 'porridge and fruit' breakfast. Saturday's lunch was a quesedia with six slices of cheese and three rashers of bacon. Annick's priority was different. She had a huge cache of chocolate for special occasions. I told her it was not on the confiscation list but she did not listen. Every time I look in the fridge another half bar was gone!

The early hours of Sunday were slow sailing but we reached the Aim Point, with 260nm to go, by 0300. As dawn arrived so did more wind and soon we were broad reaching at good speed. Skyfall was 'home free'. Through the day, all was close to perfect. Blue skies,12-15 knots of wind, sailing with apparent wind angle (AWA) 110-120 ( a fast point of sailing), and Skyfall ticking off the miles as we basked on deck, taking it in turns to doze and catch up on sleep. No need to trim sails.

As dusk approached, the wind was forecast to go round to the west so we added a 'preventive' reef for the night. Annick had just retired when I decided that the menacing clouds approaching deserved a second reef (even though we only had 13 knots of wind at that point). Within 30 minutes we were reaching in 22-24 knots. For about an hour we were over canvassed, barelling along between 8-9 knots, playing the mainsheet and once even bearing off 20 degrees to get through a gust. Great fun and not normal cruiser sailing.

Then an hour of normal 2 reef sailing, an hour with one reef. But by 2300 the wind had dropped to below 8 knots.

Therefore, at first light we dusted off 'Little Pinky', our light wind secret weapon. (Skyfall's sail warderobe includes a huge, fluorescent pink asymmetric). We wanted to get home! Although the wind was frustratingly light until around 1400, the afternoon sail made up for it. The wind filled in and Little Pinky was bringing us home in style

Skyfall braod reacching with asymmetric downwind sail
Skyfall with 'Little Pinky' taking us home

The last job of the day was to raise the New Zealand and Q flag before reaching Bay of islands (top picture). We passed TikiTiki Rock and into the shelter of the Bay of islands in the dying embers of Monday. It took a further two hours before we were safely tied up at the Customs Q dock in Opua. John had advised, in the event of little diesel, that we could carry sail as far as Okiato Point. After that the density of moored boats either side of the channel increases, reducing space for manoeuvre. We afforded ourselves the luxury of dropping sails slightly earlier, just past Brampton Buoy and before entering the river channel to Opua. The marina is on a river and there can be significant current.

We had made it! The crossing had been more stressful than I would have liked but, eventually, we arrived with diesel to spare and Annick will make her flight. We may have burned 300l of diesel, (more than we used from Panama to Tonga), and we had a lot of upwind and light wind sailing but we had made it with little stress on Skyfall and no breakages. John had done his job.

Some might say that we had 'cheated' by employing a weather router. Perhaps. But I am risk averse. One of my 'bucket list' items was (is?) to climb the Matterhorn. After all, 7000 people succeed each year. Unfortunately 70 die each year trying. 1 in 100. Alternatively, employ a Swiss Mountain Guide (SMG). Nobody had ever died when accompanied by an SMG. There are mountaineers who are skilled and experienced enough to eschew such services. I would not. I have similar views about the difficult ocean passages on our RTW odyssey. In addition, I do not think we would have attempted this particular weather window without the support and guidance from John.

What have we learned from the experience? Firstly, never get yourself into a situation where you are 'sailing to a schedule'. Booking Annick's flight in advance was a mistake. Secondly, allow enough time for a weather window to develop. I believed that 'budgeting' two weeks wait time was sufficient. It turns out that the 'perfect window' should materialise soon (October 23rd) - but a full twenty days after we arrived in Nuku'alofa and started waiting.

After customs, immigration and Biosecurity the following morning, we were free to enjoy New Zealand and reward ourselves for a successful crossing. What better way than comfy chairs, great views and a nice bottle of crisp, New Zealand white wine?

Celebrating a successful passage with a nice, crisp bottle of chilled NZ white
Celebrating a successful passage with a nice, crisp bottle of chilled NZ white

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