Fitting a Wind Generator on a Solway

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Fitting a wind generator: Fitting a wind generator on Astonel: a Solway This article was published in PBO in 2013. That makes it at least five years old as the gennie was fitted in 2012. Why put a generator on top of the mizzen mast? This article applies to those who would like to fit a generator at the top of their mizzen mast. The reasons are simple: it is out of the way and won’t tangle with anything so that you can fly a mizzen staysail without catastrophe, it will generate more power at that height than if it is half way up the mizzen, or even worse at deck level. A list of Westerly ketches: Here is a small range of Westerly yachts that this can be considered for: the rare ketch Centaur may find the weight of the generator too much. Otherwise the Pentland, Longbow 31, Renown 31 and Berwick, the W33 and W36 (Solway and Conway) seem suitable. There are other ketches.

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Agonising over which kind of charging - wind or solar

It seems that if you are cruising in the Mediterranean, you should use solar panels, and if you are anywhere north of Portugal, use a wind generator. Ideally have a bit of both. Solar panels take up large amounts of deck space, don’t work at night or under snow, and cost an awful lot to produce the same amount as a wind generator. So it was already clear that solar on its own was insufficient. Wind generators aren't infallible either. They don't work on hot still days, and on a ketch, sailing downwind often means a wind generator that is idly swinging about because the apparent wind has died to almost nothing. They are inefficient when they swing about, because they constantly accelerate and decelerate. Vertical axis gennies may be more efficient, but lack output. Horizontal axis generators can possibly be noisy, but those days are passing. Blades can be broken by sheets or halyards getting in the way, and they can be difficult to service on a mizzen mast. If minor damage to blades occurs, they become unbalanced. If they are mounted at deck level, they can scalp people (the blades are aerodynamic and very sharp) and wind speed is reduced at that level. The best power output for long distances seems to be from a towed generator because it is doesn’t fluctuate with pitch, roll, wind direction, gusts, lulls, daylight and darkness - there are two or three types - against an unnoticeable cost in speed. They are, however, dependent on speed, won't do much in an anchorage (but the manufacturers have answers for that), and can be clogged by weed.

Sweating over which type of genny to fit

Power consumption: On board Astonel are a Wallas heater and a Waeco fridge, radar, weatherfax, AIS, autopilot, water pressure system, instrumentation, plotter, radios, and interior and navigation lighting. For a time a laptop was providing the chart plotter, but its high current consumption and vulnerability took it off the boat and it was replaced with something less demanding. The boat is easy to balance and the autopilot is consequently never very busy. But if everything were working all at once, there could be an approximate 210 watt draw on the batteries, just over 18 amps. The present battery capacity is 360 amps without the starter battery, which is exclusively dedicated to the engine. It might be possible to have 30 hours of power without any recharging.  
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Astonel on mooring, opposite Tilbury power station.

Hugh Morrison Fitting a wind generator: Whatever you do with batteries, the rule of thumb is to have 24 hours of power without recharge. Realistically this comes down to about 40 watts under sail if the draw is intermittent during the day, and up to 90 watts if the draw is full at night - that’s with the lights, fridge, radar and heater on, a range of between 4 and 8 amps. The batteries are three 120Ah in parallel, and a separate starting battery. But I doubt if that would be the case in reality because we really don’t use that much power, and batteries get old, and aren't always as the labelling suggests, but it does seem to cover needs, and the engine can support the charge if needed. Work out how long your batteries would last without any topping up. Remember that we all like to be a bit optimistic and that batteries reach a kind of cliff face that they fall off rather suddenly - around 11.5v - and after that they may not be recoverable. To help out, all bulbs on the boat except two rarely used fluorescents, have been changed for LED. One tungsten bulb, at 10 watts, was the equivalent of five LED cabin lights. Existing power: There are already two solar panels - one 10 watt connected permanently to the starting battery, and one 20 watt, connected to the house batteries. The 20W sustained the battery charge during a recent failure of the wind generator when it blew its thermostat in the very cold and gale ridden spring of 2018. I have to say that this was an unexpected problem as the gennie fitted as a reputation for longevity - ten years is suggested by other users. There is also the 120amp alternator on the recently installed Beta 38. Previously there had been an inscrutable alternator controller that caused a battery to boil because it blew the alternator’s diode. That was recycled. The generators: there are at least twenty different types available, and there are more on the way - especially from the far east. Sometimes they seem very similar both in appearance and output. The parameters for choice were output, axis, blade diameter, weight and price, not necessarily in that order. Output: this is fairly obvious, but wind speed is important. Most wind generators begin to make useful power at about 10kt, with suggestions that cut in speeds of 6kts are common. The average wind speed in the UK is around 8 to 9 knots. Having motor-sailed almost the entire distance from Gravesend to Lezardrieux and back over a period of four weeks, I can believe this, although it is clear that at the moment wind speeds are being affected by atmospheric heating. Vertical axis generators are good, and fitting them is exceptionally easy. Output is generally described as ‘trickle charge’, and under sail a wind generator must be able to do most of the work in retaining battery charge. Horizontal axis generators: Some horizontal axis wind generators have blade diameters of over a meter, and this was a consideration. The fewer blades, it seems, the noisier the generator might be. And there are weights of more than 15Kg, which may be about the same as three cases of wine.

Suffering while deciding how to fit it

Having decided on a horizontal axis generator, and almost decided on which one, the next point in the deliberations is where to put it and how, the choices, for a ketch, being at deck level, half way up the mast or at the mast head. On a previous boat, a lovely Peter Duck, we had had an LVM on a very simple bracket a little over half way up the wooden mizzen mast. It was a bit noisy, and in a blow created quite a symphony below decks. A wooden boat is rather like a giant violin. We charged two batteries by using a simple pair of 10A diodes, one to each battery, with an LVM heatsink regulator. One day I caught a halyard in it, and we had a shower of broken blades. 4. Listening to umpteen caveats. Another Westerly nearby ours has a very elegant mizzen fitting half way up its mast, a kind of swan neck in stainless. This was more like it. But the most important part was researching what others had all around the world - YBW, Cruising Forum and other sites were invaluable. Then I came across a sailor who had fitted a generator on top of the mizzen mast. Following that, there were more, all of whom had agonised, listened to the critics, and gone ahead. There were even boats with the gennies mounted at the top of the mainmasts. Well, says someone, what about all that extra weight up there? Well, says I, the mizzen isn’t that high, only slightly more than half the main mast. Its roll ‘arc’ on this boat is much less than on a smaller lighter boat. It never wets the decks close-hauled, and has an easy, long-legged motion at sea. It isn’t stressful. And I’m mindful of the back and forth torsion applied by a mount on the front of the mast as the boat rolls. A mount at the top creates no torsion. That may not be a ‘fair exchange’ for the extra leverage of a top mounted gennie, but it is a consideration. What about servicing, then? A once a year inspection is recommended. I go up the mizzen mast that often anyway, and it is a very good thing to do so. A useful set of mast steps helps this, but a decent bosun’s chair is always used. The advantages are: clear air, little if any possibility of fouling halyards, the ability to use a mizzen staysail without fear of sharp blades being broken and falling into the cockpit, height - far more energy available at eight metres above the deck, and no clutter. The gennie would have to be close to the top of the mast. There is already a radar scanner and a radar reflector halfway down the mast. The disadvantages of course are in its height - whether it is easy to service, mount and dismount, and its weight - the equivalent of seven large bags of flour (or just over 10kg or ten bottles of wine) waving about as the boat pitches and rolls, testing the rigging and the inherent strength of an oldish aluminium mast. The lateral loading could be high. It’s not the sort of consideration that leads to easy sleep, but requires careful thought and well made fittings.

Painfully researching other yotties installations

More research on how to mount it brought to light some sloops with gennies on the top of their main masts, and some carefully made fittings carved from solid aluminium that clamped on either side of the mast, were through bolted and had a compression tube built in. More research, this time using old fashioned eyeballs, revealed that almost all radar, wind generators and suchlike were riveted to the masts of the boats I looked at. The mechanics of rivets is, apparently, that once in, they don't move. When bolts are in, they tend to move. There is a difference, and most of that comes down to the thoroughness of the fitting. 5.

Doing arithmetic, even some maths to figure out theoretical battery useage and the amount needed to ‘keep up’

I felt that for the price, the test results (Yachting Monthly) and the size of the blades (that was important), a Rutland 913 with a reasonable f3 output of about 3A would do the job. It has a reputation for being quiet, and a charging system that allows it to be slowed down to almost a stop by a switch at the chart table. The regulator is fairly common in function to other wind chargers, and it would also regulate the solar panel.

Realising that unless you have an actual genny sitting in your living room to measure, weigh and stare at, you aren’t going to get anywhere: so fork out the cash

The January 2013 boat show produced a bargain - the Marlec stand were offering the Rutland 913 with a regulator for a few pennies short of £450. I paid up, and in the snow I caught various bits of public transport and trollied the boxful of wind gennie back to the living room so that I could stare at it. I think that the first thing one does is to connect a 12v bulb across the leads and spin the generator hub to see if it works, and quite satisfying it is when it does. Money well spent, one can say to oneself in those moments of hopeful justification after laying out yet more cash on the sophisticated bucket that is your yacht.

Deciding to build your own bracket, but eventually doing the drawings so that someone competent can do it

Now, the huge responsibility of getting it right. The mast has to be dealt with carefully, and not end up damaged by clumsy fitting, and the strength of the whole mount must be absolute. It must also be dismountable without the heavy weight of the gennie upending the mounting post and crashing to the deck, or even overboard. Looking through pictures on the web has shown some pretty and well made mounts - and a couple of terrifying ones involving what looked like a single scaffold clamp and two jubilee clips at the masthead. Yes, seriously. The brackets would hold a mounting pole against the top of the mizzen mast. It would be through bolted at the bottom to a bracket that would allow it to hinge downwards. The top bracket would allow a through bolt to hold the mounting pole in place. The mounting pole would rise higher than the mizzen by an amount equivalent to slightly more than the radius of the blades.

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Plaster mouldings

I took some castings of the mast at the bottom in order to start fabricating the stainless steel mounts. Because it is an oldish design by Proctor, it isn’t tapered and saved the problem of making a casting at the top - sitting in a bosun’s chair. I used some plaster of paris bandage to create a mould . I wrapped a clear section of the mast in cling film, applied the bandage, allowed it to dry off then cut it free at the sail slot and at the front. At home I bound the two pieces together again, lined them with cling film again, and filled the mould with plain plaster of paris. I pushed two scraps of wood in to the wet plaster to act as handles. When it came out, it was a bit wrinkled where the cling film hadn’t smoothed out, and this was smoothed with quick set wall filler. I took it to three companies in Gravesend - one said that it was outside their usual remit. The next showed me pictures of work that they usually did, most of it about the size of a three tonne truck, and then said that there was someone who could do it. I was pointed in the direction of Roger Turk, who had already received a phone call by the time I got there. He would be able to do it. I had designed two brackets to retain the mounting post at the top of the mizzen mast, placed about 90cm apart and riveted to the mast on 3mm thick shaped backplates: each provided a through bolt. The bottom bracket also carried a lower bolt to be used as a hinge for lowering the whole unit. Right up at the top a small saddle was welded on in order to retain a line for raising and lowering the whole assembly. Roger cut a strip of 3mm stainless about 2cm wide and bent it to match the mast moulding. The result was a very close fit, and required one more adjustment. The following fitting was of the full plates with the lugs welded on. Welding distorts the mounting plates, so extra time had to be taken for fine adjustments. Once finalised, the plates were polished, drilled for monel rivets, and fitted to the mounting pole without the gennie. Anti-corrosion gaskets were made of pvc to go along with the zinc chromate paste the mountings would be bedded on. The gennie was fitted without lowering the mizzen mast. Without the gennie attached, the brackets and mount were hoisted up the mizzen, strapped to the mast with gaffer tape and adjusted for height and fit - and the first rivets installed, working from the insides of the fittings to the outside to ensure even pressure on the mast, and to help avoid any distortion. A powered riveter, rechargeable, was hired for this as monel rivets are quite hard, and applying pressure whilst sat in a bosun’s chair is not easy. The mounting pole was then lowered, the generator fitted to it with the wiring fed through the tube. The charge regulator was switched off. The cable tail from the generator was only about 30cm long, so had to be extended, and an additional connector placed just below the bottom of the mounting tube so that the mounting tube could be lowered to the deck when necessary. The two connectors used at first were 2.8mm waterproof connectors, very similar to Superseal connectors - with silicone rubber gaskets at each end and in the joint, and dosed with Contralube to help prevent corrosion as well as aid dismantling when necessary. During servicing, these connectors seemed rather reluctant to come apart, so they were replaced with chocolate block, Contralube and self amalgamating tape. The cable was 2.5mm 17.5A automotive cable. To avoid voltage drop use a cable that has as many thin wires making it up as you can find. It’s surface area on the copper that carries the current.

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Mountings drawing

The blades must be immobilised for safety and electronic reasons. A lanyard was put around the blades and the charge regulator switched off. The cable from the base of the mounting pole was continuous to the regulator and already in place. The whole generator assembly was hoisted to the masthead. The mounting pole was secured to a halyard by a harness so that it would remain horizontal as it was raised - one end of the harness around the base of the generator itself, and it was held clear of shrouds, halyards and gadgets on the mast as it went up. The bottom of the pole was located in the ‘hinge’, and from there the pole was raised to align with the mast with the blades over the top. Once the securing bolts had been fitted and tightened, the halyard was removed, allowing the gennie to rotate freely. The regulator was switched on, and the indicator LED’s on the regulator checked to show normal operation. These kinds of regulators slow the generator down as the batteries reach top voltage, and will do so whether it is the gennie, the solar panels or the alternator doing the charging. Dismounting the gennie is the reverse of this: it is secured by a halyard at the top after the blades are immobilised, and the halyard is used to lower the gennie on the base hinge. Once horizontal, a harness is attached to keep it horizontal, the lower hinge unbolted and the whole assembly lowered to the deck, with the slack cable being fed up through the conduits. The final checks were to photograph the fittings and the gennie as a reference to track any changes in the mounts, and to switch on the regulator and watch its led indicators to be sure that it was charging

What I’ve learned doing this

•The position of a wind generator is vital: the higher it is, the more wind you get. Following that come the other decisions on type, weight, diameter, price and mounting.

• If you want to fit a vertical axis gennie, then you can put it almost anywhere: the mountings that come with them are your choice, and it would be simple to fit one on the main mast just above and vertically over the spreaders, or on a mizzen mast very close to the top. Some have base plates and could be fitted on the top of the mast. And like horizontal axis generators, they can be fitted on a short mast of their own near deck level. Output is relatively low compared to the bigger horizontal axis gennies. They are also much safer - you won’t have your head or hand cut open by one.

• If you are ready to have a horizontal axis gennie near deck level, then this is the simplest and most maintenance-friendly solution. It could take a day to fit. The disadvantage may be having the extra deck stepped mast in the way during manoeuvres and the possibility of having a line caught in the blades. You’d probably only do that once. The commonest accident with generators is a stray line in the blades. A generator with an even number of blades can often be temporarily rebalanced by removing the opposite blade to the broken one - if it is only one blade broken. We do have a club member who may have walked in to one that was stepped too low for safety. The blades are horribly sharp. On a sloop, the feeling is that a stern mount is a necessity. But there are only a few reasons why you shouldn't mount the gennie on the main mast. Where do the aerials, windex and lighting go, then, and what about maintenance? The aerials could go on the spreaders, or on projecting mounts a metre or so below the masthead, the windex on a bracket, the light where it has always been, but taking into account the possibility of the blind spot from the mounting pole. Maintenance of a wind generator may be less frequent than changing the masthead bulbs, or servicing the sheaves at the truck. Some gennies have legendary life-spans, but it is true that there have been failures. At the top of the mast, there is plenty of wind, almost no chance of anything being tangled in the blades, and only the consideration of weight, anywhere from less than 6kg to more than 15kg on a pole that will clear the blades (between 600 and 1200mm in diameter).

• On a ketch, the obvious and almost traditional place is a tailor made bracket about two thirds to three quarters of the way up the mizzen. This may seem to be less of a problem in terms of maintenance, but is a halyard magnet. My own experience with this setup was sudden and unexpected, a result of a lack of concentration in a f6 when the mizzen halyard met the blades and they showered the deck in pieces. I installed a set of tubes (kitchen drain pipe) up the mast to take the halyard downhaul after that. The other problem is when sailing off the wind as apparent wind lessens and the wind patterns around the mizzen create dead zones - most noticeable on a run - and the wind generator begins a bit of a rotating dance without generating much power, just when the autopilot is working its hardest. And one more thing - hauling up a mizzen staysail isn't impossible with a genny two thirds up the mast, but it is definitely high concentration time - the head of the sail must be hauled up with great attention, with the tack eased only enough to allow the sail to go up.

• If a mount is fabricated for a position on the leading face of the mast, then blade diameter or sweep is crucial. The larger the sweep of the blade, the further the gennie protrudes over the deck, and to some extent the more torsion there is on the mast as the boat rolls. There are one or two significant examples of large bladed turbines being mounted on brackets that won't allow continuous 360˚ rotation and have stops on them to prevent the blades colliding with the mount and anything else. These look self defeating. How could the generator face any breeze that is a few degrees aft of the beam, especially when running or making ground by quarter reaching down a course in a series of gybes? Another point that is often made is that yachts always lie to the wind when at anchor. Well, that's clearly not true: a tide with a bit of power in it will drag a boat around - but won't necessarily affect what wind there is if you have a 360˚ mount. And boats aren’t always at anchor. They may be alongside with a wind up the stern.

• We bought a Marlec Rutland 913 and are pleased with the purchase. If we had the money, it would be the legendary Ampair 300, made in the UK, with feathering blades that will stand up to the hooley of all hoolies. It was getting on for three times the price, and our ambitions are modest. It’s worth finding their installation instructions and reading them through, though. We also noticed that its cut in speed was lower than any others.

• It is worth saying something about the noise: when the gennie is loaded, it sings quite loudly down the mizzen and across the after cabin coach roof. We ten to switch it off when sleeping. The saloon and the forepeak don’t suffer from the noise - which isn’t deafening, just noticeable. There would have been, with hindsight, ways of reducing noise.

• And finally - the quality of the brackets must not be compromised, and the fixings must be absolutely secure. Your drawings must be accurate, and your engineer must understand them. Roger was exemplary - he asked the questions, explained what he thought I meant, made me do the fittings methodically, and kept to time. A wind generator needs to be seen as a fit and forget item and it needs the best quality that you can muster if you are to do it yourself - with a little help, of course. I hope I’ve designed this one to stay put, and if it has to come down, then it needs one person up the mast, one down below, and a halyard with harness to let it down to deck level in an easy going way.

It seems, from reading between the lines, that manufacturers generally test their generators in wind tunnels: i.e. fixed conditions. These don’t take into account the constant variations of wind when sailing. There also seem to be no particular standards for measurement, although 10m/s seems to be one benchmark. That’s a force 5, approaching force 6. I feel that we need a standard around cut-in speed (i.e. when it starts charging), f3, f5, and maximum charge. These may be the speeds that yotties are most likely to relate to. The powercurve from Silentwind shows how wind power increases exponentially. At about 9Kt, there is an output of about 25W, at 18Kt it has risen to about 140W, and at 27Kt it is producing 400W. Doubling the windspeed produces nearly six times the power, and trebling it produces about sixteen times the power. This reflects the power of the wind, not the generator, which at the time of writing this was an exceptionally powerful gennie, designed for extended periods under sail.

Westerly provided two eyes on the rear end of this boat at the pushpit, and these come in useful for fitting a couple of running backstays, which I did in order to add some stiffening to the top of the mizzen mast. I don’t think that this is absolutely necessary, but it seemed to be a ‘good idea’. The backstays attach at the mizzen masthead, and come down to a 4:1 set of blocks at deck level, with the line coming forward to the cockpit where there are cam cleats installed. They are made up of pre-stretched polyester and are not heavily loaded, and can be clipped to a shroud to keep them out of the way when short tacking.

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