Posts tagged autopilot
Since starting sailing offshore singlehanded, I’ve received a number of questions about electrical setups. When I purchased Idefix, she had the minimalist electrical system of an inshore racer: running lights, a VHF radio, speed and wind instruments, and a small battery. This clearly wasn’t sufficient for what I planned to do, so I had a lot of number crunching and wiring to do. Here’s how I went about it.
There are a few basic things you need to know about electricity before reading this. If you’re an electrical genius, you might want to skip to the next part. First of all, units:
- Electrical potential is measured in Volts (V) – this is used to measure the electrical charge on a battery. Boats usually use a 12 Volt electrical system. This is only a nominal voltage, a typical battery will show somewhere between 14.4 and 12.5 Volts. More on this later, but if it’s showing 12 V, you need to charge it ASAP!
- Electrical current is measured in Amperes (A), also known as “amps”. This is the measure of flow of electricity.
- Electrical power is measured in Watts (W).
- Electrical resistance is measured in Ohms (Ω). This is typically a property inherent to electrical circuits. An open circuit (no electrical connection) is infinite Ohms. A short circuit (perfect connection) is zero ohms.
- Battery capacity is measured in Ampere-hours (Ah), also known as “amp-hours”. 1 Ah is equivalent to a 1A current drawn for one hour, or a 2A current over half an hour.
Electricity follows a couple basic laws that you might remember from your high school or college physics classes:
- Ohm’s Law: Current = Voltage / Resistance
- Joule’s Law: Power = Voltage * Current
We won’t deal with resistance much here, so focus is really on the second one. For example, a 20 Watt incandescent light at 12V draws 20/12 = 1.67 Amps. Finally, most things on boats (batteries or devices) are connected in parallel (positive to positive and negative to negative), which means that their currents add up, but voltages do not. Putting two 12V, 110Ah batteries in parallel means that you have 220Ah of battery capacity at 12V. Wiring them in series would mean that you have 110Ah at 24V.
The first step to equipping any boat’s electrical system to be independent offshore is to make a budget of all the electrical power consumed. It helps to be conservative here. Once that’s done, one can choose a scheme for power generation that adequately covers the losses for the time spent offshore. Here is my electrical budget for Idefix:
|Ah for 16 days||908.41|
Power consumption for each item on board can be easily measured using an ammeter or battery monitor, or estimated from specifications. The hardest part is to have a conservative but realistic estimate of how much you will use each item every day. The one I’m showing above was my “rainy day” budget, and most of the time I ended up running the AIS, laptop and music almost 24 hours a day. As you see, I had to figure out how to make up a little under 60 Ah per day. The total use for a 16 day trip (about how long a transpac could expect to take for a boat with an intact hull and rig) was over 900 Ah. To give you an idea how much power that is, running your standard 60W incandescent light bulb for the same amount of time would consume about 2000 Ah. the average car battery holds about 70 Ah. So on average, Idefix at sea runs at less than half a light bulb. I also came up with a second electrical budget for the 400-mile qualifier I had to do. Since this was going to be a much shorter trip, I was going to push the limits a little more, hand steer the boat most of the way, and rely more on VHF for weather:
The planned daily power consumption for my qualifier was going to be almost half of what it would be during a transpac.
My choice of batteries was driven by a couple constraints:
- Capacity: I wanted to be able to run my electrical system for the four days it would take me to do the 400-mile SHTP qualifier without recharging or damaging the batteries. Most flooded lead-acid batteries can only be discharged to about 50% without damage. This means I need a capacity of about 143/0.50 = 286 Ah. An AGM battery can withstand a discharge of up to 80%, so I could get an AGM battery of only 143/0.80 = 179 Ah.
- Space: To keep the batteries low, centered, secured, and covered, I was limited to the space under the benches in the middle of the cabin. This meant a maximum battery size of about 16″ x 9″.
- Safety: for redundancy, I needed two batteries that I could isolate in case one failed. I also wanted a sealed lead-acid or AGM battery that wouldn’t spill acid when the boat heeled.
- Budget: you’ve probably understood by now that I’m a cheapskate. I wanted the least expensive batteries that met my criteria.
- Weight: I wanted my batteries as light as possible for a given capacity.
With these criteria, I ended up buying two Universal UB121100 110Ah AGM batteries. They’re about 70lbs each, and fit nicely under the benches. They ended up providing plenty of power, and with my meager electrical consumption I could run for 4 or 5 days without any charging.
The batteries alone wouldn’t suffice for crossing the Pacific, so I had to think of a way to charge them. The Olson 30 has no inboard engine, and therefore no alternator. A gasoline-powered generator would’ve been about $1000, and I didn’t like the idea of flammable fuel and a loud and stinky mess on the boat. Wind generators were a little more expensive, and I ruled them out because they’re also noisy, heavy, and don’t put out enough power downwind. I pretty quickly focused on solar power, as it was quiet, clean, low weight, and cheap compared to other options. There are a couple things to know about solar panels. For one, they rely on weather, which is a notoriously unpredictable thing. Clouds will cut down on solar power production dramatically. So will the shadow of a sail, mast or rigging. So will a solar panel that’s not pointed directly at the sun. One can dedicate a lot of effort to calculating what the output of a particular solar installation would be on a given day in a given latitude, but since I was going to be cruising from the cloudy environs of 38 North to the mottled skies of the tropics, I simply came up with some rough figures: an efficiency of about 50% to account for controller losses, shadows and angles, and an illumination of 8 hours per day to account for nighttime and low sun angle. A solar panel typically isn’t wired directly to a battery, but through a device called a charge controller. There are several types of charge controllers, the most popular of which are PWM and MPPT. I selected an MPPT charge controller as they are significantly more efficient than PWM controllers. The charge controller losses were factored in my 50% efficiency.
If we go back to our transpac power consumption of 56.77 Ah/day, that gives us a requirement of 56.77 * 12 = 681 Wh/day. With 8 hours of power-generating sun a day we need 681/8 = 85 Watts, and at 50% efficiency that means 170 W of installed solar panels. I found a reasonable deal on a 135W panel and a 40W panel, so I ended up with 175W installed, with the two panels in parallel. I wanted to have two separate panels in case one cracked, and the 40W panel would’ve allowed me to run running lights and send out a message. I didn’t really know where to put it, so it ended up forward of the companionway under the boom, which means it was in the shade most of the time.
Interestingly, solar panels have become much more affordable and much better since I first equipped Idefix in 2010. The lightweight, flexible panels in particular are very attractive, and it’s only a matter of time before we see sails capable of gathering power.
Other Means of Generation
Solar was the clear choice for what I wanted to do, but there are other options to consider. Of course if your boat has a diesel engine, you have a fair bit of power at your disposal already. Fuel cells can be attractive too, being clean, quiet and powerful, although they are expensive and methanol fuel can be difficult to find. Finally, hydrogeneration seems to make leaps and bounds, with many of the IMOCA 60s now using hydrogenerators for power. Watt&Sea makes one that sells for a little under $4k.
A good battery monitor is a critical part of the installation. The monitor simply counts the current flowing in or out of the batteries and integrates current flow over time. It can therefore display the state of charge of the batteries at any given point in time, which is extremely useful. Like I mentioned earlier, most lead-acid batteries cannot tolerate being discharged past 50% of their capacity. I have seen several sailors deep-discharge their batteries and pointlessly ruin them. Most monitors have alarms set to prevent this. It’s also critical that everything be wired through the monitor to get an accurate picture of the state of charge of the batteries.
Our final power budget adds the power generation and subtracts the consumption to come up with a daily figure. Obviously we want this to be positive.
|Ah total (16 days)||24.92|
Tips for saving power
One of the greatest things about sailing is that we have virtually unlimited range. However, on a small boat with no inboard engine, electricity can be a bit of a stretch. If you’re singlehanding, the amount of power burned by an autopilot running over twelve hours a day starts to make things tricky. But it’s also a great opportunity to show that you can do more with less, and there are quite a few benefits to being frugal with energy. Lowering the power draw helps lighten the boat (panels and batteries add up), free up real estate (panels take up a ton of space), preserve your wallet (panels and batteries are expensive), keep your boat from looking like a solar farm, avoid the noise of a wind generator and the smoke and fuel of gas or diesel, keep you independent of marinas and fuel docks, and most importantly, keep you from ending up in the dark offshore. For that you have to be willing to forgo some of the power-intensive habits that are so easy to acquire on land. The most important part is to spend a little bit of time thinking about where your electrons are going, and discipline yourself while underway, keeping things off unless you really need them, and hand steering when you can. Here are a couple tips for lowering your power consumption:
- Ditch all your incandescent bulbs for LED lights. LEDs use up a fraction of the power. This is especially important for running lights, which are on all the time. As for cabin lighting, now you can find warm white LEDs that have that pleasant glow, so there’s no reason to stick to incandescents. I used a $5 red trailer LED to light up Idefix‘s chart table and cabin while underway.
- Ditch refrigeration. It is the single most power-hungry piece of equipment on a boat (except for a windlass, but you don’t run that all day while underway). I lived on Idefix for many months without refrigerated food. Here are some of the things I ate: cured meats, dried sausage, hard cheeses, eggs, bread, tortillas, cabbage, citrus, bananas, potatoes, onions, peppers, pineapple, fruit juice, UHT milk, dehydrated veggies of all kinds, pasta, rice, every canned food imaginable, and of course fresh fish! When you get back to land your loved ones will think you a rock star for keeping your eggs out of the refrigerator and eating things you left on the kitchen counter overnight.
- Look for mechanical alternatives to some of your electrical systems. I’ve never used a wind vane before, but I’ve heard they’re like a magical autopilot, and they use no power! Where many boats have a depth sounder, I got by with a lead line.
- Laptops are big power hogs. Look at battery life and power rating to get an idea before you buy. The netbook I used for AIS, chartplotting, email and weather was the least power-hungry on the market. I swapped out the hard disk with a solid state drive and brought the power consumption to under two-thirds of an amp.
- Inverters waste a lot of power. Get a 12V power supply for your laptop, MP3 player or cellphone.
- Make it a ritual to turn off running and instrument lights when the sun comes up.
- Understand your system and know what your big consumers are. Autopilot and laptop were mine, and I shut these down whenever I felt stressed about power.
- Most importantly, keep an eye on your power consumption. Use the battery monitor, and note the battery state of charge in your logbook. This will help you track trends, and tell if you’re running a deficit before things get hopeless.
On the 2012 SHTP we were in overcast for ten days and I noted early on that I was never coming up to full charge and started rationing power. I also kept an eye on battery voltage and realized at one point that my MPPT controller had been set to the wrong output voltage and wasn’t topping off my batteries, which allowed me to reset it to get even more power out of it. Not far away, my friend Ronnie on US101/Hope for the Warriors was in the dark, hand steering for 20 hours a day and unable to check in with his position. In the weeks before the race he had installed some high-tech lithium batteries that required a significantly higher voltage than lead-acid batteries, with a lightweight flexible solar panel that put out a little over 100W, and had a top-of-the-line but power-hungry autopilot. Unfortunately he was running short on time and hadn’t had a chance to test his setup, and the weather caught him off-guard and left him without power. Being a stupendous badass, he simply shut everything off, leaving just enough power to send the message that we wouldn’t hear from him for a while, and pulled out every ounce of human endurance to hand-steer his boat to a division win. While it makes for a great story, thoroughly planning and testing your electrical system is a good start to having a more relaxing trip.
I’m finally getting around to cutting some of the footage from the 2012 Big Pacific Adventure, and I thought this little clip might help some of the people preparing for this year’s Singlehanded Transpac and Pacific Cup races, so it’s the first to go up. I threw in a few gratuitous sailing scenes just for fun!
Idefix has finally arrived in Australia. There’s a problem with the wiring for the HF modem so I apologize for the previous update posting late. If you’re interested in me digressing on a bunch of topics, you should just scroll down and read it.
Being only a few hundred miles from Bundaberg, I felt that it wasn’t worth the time to troubleshoot the modem wiring to get a weather update. Because Shirley was somewhere between sea-sickness and actual illness, I had been hand-steering almost continuously for the last two days, with only a break here and there. The last forecast had shown mild winds for the rest of the trip. On Sunday, a line of convergence clouds obscured the horizon to the south-west of us. I knew there was a zone of convergence, but didn’t expect it so close. About mid-day, lightning started flashing in the clouds, which were clearing getting closer. At nightfall the clouds were almost on top of us, and around midnight we sailed into the thunderstorm. Lightning was almost continuously flashing all around us, but there was surprisingly almost no thunder. I tried not to think too much about what could happen if we suffered a direct strike. More worrisome was the fact that we were at precisely that distance off the coast where freighters like to cruise when we were surrounded by rain and the visibility dropped to only a dozen feet or so. But the only thing that hit us was heavy rainfall. I took cover in the cabin and steered the boat with our rope contraption, until the downdraft hit us and the boat heeled over dramatically, pinned hove-to with the jib aback. I ran back out to the tiller in the pouring rain and straightened out the boat, heading due south for a bit. The wind then veered another ninety degrees and I jibed and pointed the boat back at Australia, making six and a half knots. Just as the seas started building, the wind shifted another sixty degrees and started easing. By the end of it all I was completely soaked and getting cold, so I hove-to and changed to dry clothes while Shirley made me hot tea. We somehow managed to avoid the other storm cells, and around dawn we sailed past Sandy Cape and into Hervey Bay. The land is so flat here, and the water so shallow, that we had to stand off far enough from land that we couldn’t see any of it. Only about 3 or 4 hours later did the first sign of land appear: “The Hummock”, the only hill in Bundaberg. By early afternoon we had completed our last ocean crossing of this trip and were docked at the marina, which is a little hike away from town, and cleared in with customs. The boat is confined to Bundaberg until the importation paperwork is completed, which will hopefully take less than a week.
In addition to the mainsail and trysail, we have many headsails on board Idefix: a 150% genoa (#1), a 140% light-air drifter, a jib top for reaching, three 100% jibs (#3), an 85% jib (#4), a storm jib (#5), two 1.5-oz spinnakers, and two 1/2-oz spinnakers. I used almost all of them during the race from San Francisco to Hawaii, but in the 7000 miles since then, I think it’s fair to say the #4 jib has carried us at least 5000 miles, and the dacron #3 a fair bit of the rest. The jib top did its fair share before delaminating in Fiji. So much for having lots of fancy racing sails while cruising… Nevertheless, because the boat sails so well with little wind, the sail-handling is fairly easy, and our engine is not very powerful or easy to use in a seaway, we sail a lot more than most of the other boats we’ve met up with. We’ve only purchased about 20 gallons of fuel so far. There’s 5 or 6 gallons sitting in our tanks right now, and I expect at least half of what we’ve burned has been when we’ve had the motor on the dinghy. The only extended motoring we’ve done while underway was a night of particularly light wind shortly before getting to Niue, and a day of motoring while navigating the reefs of Viti Levu. 400 nautical miles traveled per gallon of gas isn’t bad!
The wind lightened up to a gentle breeze last night, and at first light this morning I hoisted the big genoa. When I was done I turned to watch the sunrise, and was treated to not one, but two green flashes, as the sun was hidden by a swell and then re-emerged. Right now we are close reaching at about 5 knots in a 7 knot breeze and flat 1-meter swells, close reaching, 200 miles away from Sandy Cape. Shirley is sleeping before her night shift. I’m clean as a whistle after shaving and showering this afternoon. The cockpit is a tangle of bungees and lines in an effort to get the boat to steer herself. The contraption seems pretty well balanced because I’ve managed to type a couple sentences without getting up to adjust something, and the boat is still pointed at Australia.
“When are you leaving?” was the question on everyone’s lips on the visitor’s dock in Port Moselle. It seemed like about half the boats were headed to New Zealand (Opua or Whangerei), and the other half to Australia (Bundaberg or Brisbane). Most of them were under pressure from their insurance carriers to be out of the tropics by December, when cyclones supposedly start rearing their ugly heads. On the flip side, every week of waiting brings us closer to the more clement weather of summer. So there’s a lot of scanning the weather charts for a good window during November. Luckily for us, the trip to Australia is quite a bit easier than to New Zealand.
We’d had enough of waiting and were about to leave when another yachtsman shared his professional routing advice to wait for another three or four days for a hypothetical developing low to pass. We did, and probably avoided some unpleasant seas as a result. We set out on the 13th and got soaked beating out of the lagoon, before we could reach off towards the West. Shirley was hit with seasickness as usual, but this time it seemed like her stomach was in a permanently upset state, so I had her lie down and decided to singlehand the boat, leaving the autopilot on most of the time and taking short catnaps.
We moved fairly quickly for about three days, with winds and seas slowly subsiding, and Shirley started feeling well enough to relieve me of checking on the sails and scanning the horizon periodically. Yesterday, I was sitting in the cockpit reading when I felt the temperature drop a couple degrees, and it got a little dark. I was surprised, because the sky was almost perfectly clear. I looked up and saw a couple little clouds in the vicinity of the sun. I figured one of them must be sitting right in front of the sun, and went back to my reading. The sky kept getting darker, yet the shadows cast by objects in the cockpit were still crisp. Sure enough, there was no cloud in front of the sun. Something felt odd. For a moment I thought I might be sick, or maybe the sun was going out – wait a minute… pull out the nautical almanac… yep, total solar eclipse of November 15th, visible in the South Pacific. I guess the solar goggles for sale in the pharmacies in Noumea should’ve tipped us off! We didn’t think to buy any, but in a pinch the solar filters on the sextant allowed us to see the moon almost completely blotting out the disc of the sun.
This morning, the 16th, as I was rummaging in the lazarette to pick out the bilge pump handle, I put a bit of pressure on the tiller and the autopilot drive immediately shut down. I tried restarting it and troubleshooting, to no avail. Our third and last drive unit has given up the ghost, leaving us to hand-steer the boat to port. I thought I’d managed to fix one of the other drives, but it is only capable of working for a couple seconds before its motor locks up too. Thankfully, conditions are pretty mild and Shirley and I are well rested, so this shouldn’t be too difficult, but it is annoying to have to stay glued to the tiller for hours at a time.
As a result of this, and because weather to the South is a bit unsettled, we are heading for Bundaberg – still 350 miles away – instead of Coffs Harbour, yet another 350 miles down the coast. We should get there sometime Tuesday.
Idefix is in Hanalei, rafted up to Green Buffalo (thanks Jim!). Got in shortly after midnight last night. The last day was an incredible white-knuckle ride. During the night I’d taken down the spinnaker in a squall, just left main up and gone to sleep for 5 or 6 hours. I woke up on Friday and the wind had finally arrived. The waves had picked up quite a bit too. The boat was moving at 6 or 7 knots with just the main. I did some quick time-distance-speed calculations and was faced with a conundrum. I was 150 miles away, and I could slow down some and get there early Saturday morning, as planned, but I would’ve felt stupid trying to slow the boat further. I didn’t want to arrive in the pre-dawn hours, because I’ve been falling asleep at 3am like clockwork. But I see that if I average 8 knots, I can get there at midnight. So I decide I’m going to put the pedal to the metal and try to get there as early as possible. The catch is that there’s no way the autopilot is going to handle the boat with a chute up in 20-knot winds and messy 10-foot seas. So I finish breakfast, toss an armful of snacks and drinks into the cockpit, crank up the music, hoist the chute and am off on a wild ride that’ll last 16 hours. I was doing mental math the whole way and calculated an average 10 knots for the first hour, and 9-9.5 for the rest of the day. I got drenched by waves breaking into the cockpit within the first 10 minutes, so needless to say it was not a comfortable ride. I managed to leave the tiller 5 or 6 times to fuel up on food, water or caffeine, but that often ended in a broach or accidental jibe. At some point I went past the research ship Kilo Moana, which was hoding station 85 miles from Hanalei, and chatted them up on the VHF. They mentioned they’d seen another sailboat go by five days ago, by the name of Truth, and he was hauling like me. I was pretty flattered that they thought I was anywhere near Truth in speed! Eventually the sun went down, and the Kilauea lighthouse came into view. Then it was down to the last few miles, and soon I was trying to pick out the lights of the condo, and trying to reach the race committee on the VHF, and getting run over by squalls. Last time I had cleaned up and shaved before the finish. This time I took one last big gulp of coffee and managed to spill it all over myself. Oh well. Finally just pulled out my cellphone and called the race deck. Last couple miles the wind shifts a ton. I’d been expecting it, but then forgot. Fighting to keep the chute up, eyes riveted to the GPS to make sure I cross the line without hitting the reef. Finally I’m there.
Sent at 2012-07-13 15:50 UTC from 23°11.21’N 156°57.58’W