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Old 05-12-2020, 20:09   #1
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Electric motors on a Woods Flica 34' sailing catamaran

Hi guys, I am currently building a woods flica 34' sailing catamaran and I am planning out how to fit it out. I was thinking of installing an electric inboard engine (in particular, the EP-12 electric inboard by Elco motors: EP-12 Electric Inboard - Elco Motor Yachts https://www.elcomotoryachts.com/prod...ctric-inboard/) on one hull and using an electric outboard engine (the EP-9.9 electric outboard by Elco motors: EP-9.9 Electric Outboard - Elco Motor Yachts https://www.elcomotoryachts.com/prod...tric-outboard/). I want to have 4x440watt solar panels (total of 1.76 kwatt) and a lithium ion battery bank (most likely 400 AH). I want to use an electric pressure cooker/air fryer like the instant pot duo for my cooking. I plan to have a small propane or alcohol stovetop as well for backup/emergency. What do you guys think of this plan? Are there any issues with using a single inboard and a single outboard that I'm not aware of? Also would I even need to install diesel or gas tanks since I will be relying solely on electric? I want to be able to do blue water cruising and be off grid/self-sufficient as possible. What do you guys think of having a small generator like the predator from Harbor freight or honda as well to make it a hybrid boat? I actually don't want to carry it as I don't think it will be necessary so I can save on weight/maintenance issues. Would that be foolish? The other option is to go with the electric inboard (EP-12) in one hull and a diesel outboard motor in the other hull.
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Old 06-12-2020, 05:53   #2
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Re: Electric motors on a Woods Flica 34' sailing catamaran

Welcome to CF and an interesting project you have there.

You haven't said were you are or were you plan to sail. This might have a bearing on some of the later questions. For example if you are only ever going to be sailing in hot or nicely warm climates then diesel may not be required for heating which its brilliant at. So that is one less fuel.

Turning to the question of petrol, what are you going to use for a dinghy engine? and therefore will you carry petrol for this engine? If not, then perhaps you don't need a lot of petrol on board, but it would sure be nice to have a Honda 22i generator just in case. At 20kgs and say 10L of petrol even if you never have to use it, its hardly a big investment or difficult to stow somewhere. I spent a couple of days in August watching the output of our 300w solar panel in the rain. Answer 60w and the rain persisted for 3 days. With the heating to keep the boat dry the house bank was slowly going down and nothing I could do about it. In the end I ran the engine for a couple of hours to put some amps back in the bank.

How did you get to the figure of 400A LFP bank? I think that is woefully short to power those engines and run the boat. What is the minimum range you will require? Also, there is a huge price difference between the inboard and outboard, why not fit two 9.9hp electric outboards and invest the savings in more LFP?

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Old 06-12-2020, 06:51   #3
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Re: Electric motors on a Woods Flica 34' sailing catamaran

Great project to have, but I've got to wave some red flags.

Ditto on Pete7 on your talking about a whole bunch more electrical output than electrical input. Start with solar ratings being "at the equator, noon, no clouds, no boom in the way" and work from there.

Why different power on the two hulls? You're buying into asymetrical thrust.

You're going to need a genset capable of powering the whole thing. Hondas get good press on the forum, but that's gasoline in your boat, which is to be avoided if possible.

People who rely on solar alone have very restricted (and carefully measured) energy budgets, not air friers.

My recommendation is that you start at one end, either the energy that you want to use or the energy you want to produce, and work to the other, remembering percent losses in efficiency (motors get hot, for example) as you go step to step, and make the two ends compatible. You'll probably find that two small diesels are your best propulsion, that solar is best left to non-critical uses, and that a second means of charging the house bank is a good idea.
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Old 06-12-2020, 09:20   #4
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Re: Electric motors on a Woods Flica 34' sailing catamaran

Thanks for all the fantastic input everyone I really appreciate it!

I recently bought the instant pot duo crisp which is a combination air fryer and pressure cooker. It's a pretty amazing device that makes delicious food at the touch of a button I highly recommend it. It is 1500 watts and it takes about 20 minutes to cook so if you use it twice a day let's say it uses up 1500 Watt hours. The solar panels should generate enough energy to run the instant pot air fryer in an hour of sunlight if my math is correct (and please correct me if I'm wrong!). The instant pot air fryer combo is the one luxury item I really want on my boat- everything else I am willing to sacrifice. However, I would limit it's use when I don't have a lot of solar/low batteries, or I need to use the motors extensively. It would mainly be for when I am anchoring out extensively and I have plenty of solar energy.

I want to be able to do extensive bluewater cruising and to be able to go anywhere and do anything and to be as offgrid and self sufficient as possible. I will probably mostly be in the tropics but I want to be able to cruise in colder climates as well.

My plan is to rely on sailing as much as possible and I plan to fish/read a book if there's no wind. I would like to have the electric inboard for regeneration as well while underway. I am considering a diesel motor in the other hull for backup and for hot water as well.

I want to practice good seamanship by being in the right ocean in the right seasons to avoid major storms. However, I want to be perfectly capable of handling any storm that may come my way as well. If there's a storm coming, I would assume there would be good wind prior to the storm to allow me to sail out of the way of the storm? Or is that wishful thinking on my part? If I cant' sail out of the way and there's not enough batteries, the diesel motor would be the last resort.

I will probably carry a light dinghy like the origami wooden widget (https://woodenwidget.com/fliptail.htm) with a small 3.3hp outboard.

I've heard the small honda and harbor freight predator generators don't last long in a marine environment- anyone with real world experience with these generators would be very helpful!
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Old 06-12-2020, 10:18   #5
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Re: Electric motors on a Woods Flica 34' sailing catamaran

Good afternoon, Sailor Forever.

I've had a littlle time to think about your admirable goals. Maybe I can say something constructive rather than just shooting down your ideas. I do have one negative to share: stay away from alcohol stoves; they have a very poor reputation in cruising.

But then: A reasonable minimalist system that keeps you off the grid might include as much solar as you can reasonably mount, a small diesel in each hull, and an alternator on each diesel that is capable of charging the house bank when the solar system doesn't. Then in your worst case you might have to run an engine in neutral to bring up the house bank, but more usually would use solar plus charging when under way on engines. Then, adding electrical uses (don't we all) only alters the point at which you need diesel charging. Your up-front expenses are large, because diesel engines are not cheap, but your simple system gives you freedom to live as you like. You might add an inverter to the mix so you can have 110v AC as well. No gasoline.

That's my thought. I hope it gives you a starting point to further think about what you want.
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Old 06-12-2020, 10:45   #6
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Re: Electric motors on a Woods Flica 34' sailing catamaran

Thank you tkeithlu for your thoughtful post. What do you think of one diesel with alternator in one hull and a electric inboard in the other hull. I figure I can get the best of both worlds with that setup. I can get the benefits of regeneration with the electric inboard as well as the reliability of diesel for motoring as well as charging up the batteries with the alternator. Do I really need two diesels? Also with this setup would I even need a generator?

I will stay away from alcohol stoves thank you for the tip!

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Originally Posted by tkeithlu View Post
Good afternoon, Sailor Forever.

I've had a littlle time to think about your admirable goals. Maybe I can say something constructive rather than just shooting down your ideas. I do have one negative to share: stay away from alcohol stoves; they have a very poor reputation in cruising.

But then: A reasonable minimalist system that keeps you off the grid might include as much solar as you can reasonably mount, a small diesel in each hull, and an alternator on each diesel that is capable of charging the house bank when the solar system doesn't. Then in your worst case you might have to run an engine in neutral to bring up the house bank, but more usually would use solar plus charging when under way on engines. Then, adding electrical uses (don't we all) only alters the point at which you need diesel charging. Your up-front expenses are large, because diesel engines are not cheap, but your simple system gives you freedom to live as you like. You might add an inverter to the mix so you can have 110v AC as well. No gasoline.

That's my thought. I hope it gives you a starting point to further think about what you want.
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Old 06-12-2020, 11:39   #7
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Re: Electric motors on a Woods Flica 34' sailing catamaran

Youíre building one of my favorite cats. Nice! Having a cat with one central outboard as power propulsion I wouldnít want to give up dockside maneuverability that comes with two props as you are suggesting for your new build.
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Old 06-12-2020, 12:05   #8
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Re: Electric motors on a Woods Flica 34' sailing catamaran

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Originally Posted by sailor4life7777 View Post
Hi guys, I am currently building a woods flica 34' sailing catamaran and I am planning out how to fit it out. I was thinking of installing an electric inboard engine (in particular, the EP-12 electric inboard by Elco motors: EP-12 Electric Inboard - Elco Motor Yachts https://www.elcomotoryachts.com/prod...ctric-inboard/) on one hull and using an electric outboard engine (the EP-9.9 electric outboard by Elco motors: EP-9.9 Electric Outboard - Elco Motor Yachts https://www.elcomotoryachts.com/prod...tric-outboard/). I want to have 4x440watt solar panels (total of 1.76 kwatt) and a lithium ion battery bank (most likely 400 AH). I want to use an electric pressure cooker/air fryer like the instant pot duo for my cooking. I plan to have a small propane or alcohol stovetop as well for backup/emergency. What do you guys think of this plan? Are there any issues with using a single inboard and a single outboard that I'm not aware of? Also would I even need to install diesel or gas tanks since I will be relying solely on electric? I want to be able to do blue water cruising and be off grid/self-sufficient as possible. What do you guys think of having a small generator like the predator from Harbor freight or honda as well to make it a hybrid boat? I actually don't want to carry it as I don't think it will be necessary so I can save on weight/maintenance issues. Would that be foolish? The other option is to go with the electric inboard (EP-12) in one hull and a diesel outboard motor in the other hull.
Any regen capacity with that Elco engine? For weight concerns I'd try to eliminate the diesel if at all possible. You'll need gas for the dinghy outboard at least so go four stroke and get a Honda suitcase generator so the gas can be used for both. As Pete said, where you'll be sailing will have a lot to do with what you end up powering. In the tropics you won't need heat but may need some fans and opt for convection cooking to lower the heat in the galley. Calculating the solar is kind of tricky - under sail you'll have some shading issues but on the hook with the sails down you'll get heat depreciation up to 20% since you won't have the cooling convection you'd get under sail. 1,720 watts of solar would average about 430 amp hours of power on sunny days. Depending on your load requirements, you may need to consider engines with regen ability (these always cost more). The regen only works when you're under sail but can top the batteries off rather quickly if you're doing in excess of five knots which on a cat I'd assume you would be.
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Old 06-12-2020, 12:10   #9
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Re: Electric motors on a Woods Flica 34' sailing catamaran

Is that 400Ah at 12V? If so, thatís not very much if you want electric cooking, let alone to power a motor (and arenít electric motors powered by 48V?). We are trialing an electric air fryer rated at 1800W and when itís heating up it is pulling 160A through our inverter. On another site Iíve seen figures of 160-200 Ah per day (at 12V) for electric cooking alone.

Regarding different motors, as another poster mentioned, that you get very similar thrust from the two props despite on electric and one diesel. Otherwise, motoring will be a real pain with the boat always driving to one side.
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Old 06-12-2020, 12:31   #10
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Re: Electric motors on a Woods Flica 34' sailing catamaran

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Originally Posted by sailor4life7777 View Post
Thank you tkeithlu for your thoughtful post. What do you think of one diesel with alternator in one hull and a electric inboard in the other hull. I figure I can get the best of both worlds with that setup. I can get the benefits of regeneration with the electric inboard as well as the reliability of diesel for motoring as well as charging up the batteries with the alternator. Do I really need two diesels? Also with this setup would I even need a generator?

I will stay away from alcohol stoves thank you for the tip!
You'll want to keep the weight similar in each hull. The diesel engine will weigh probably twice what the electric engine will (not to mention the fuel weight.
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Old 06-12-2020, 13:19   #11
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Re: Electric motors on a Woods Flica 34' sailing catamaran

Our setup w/ 48V 240A 11.6kWh LiPo batt. bank, 460W solar has all electric utiliies: large stand-up front-opening freezer/fridge (less than 1kW/24 hrs), 1kW microwave, 800W water-boiler pot, and 2-burner non-induction elect cooktop. Also 16K BTU HVAC we rarely use. On a 700nm round trip to the Channel Is. last year w/ teen-age granddaughter & friend we never had to run the 165hp diesel just to charge. At most 3 days in a row anchored/moored (Avalon Hbr.)

The water-cooled 7/5 kW motor-gen in line with the diesel will pump out a full 5kW charge @ 2000RPM up to about 52V, then taper and shutoff @ 53.8V, Solar shut-off @ 54.4V, as does the 48V/5000W Victron inverter/charger.

Under electric motor, it will hold 7kW output for only a minute or two, then settle down to about 5.5kW for a speed 4.5-4.8kts in flat water with a range of about 10nm at that speed, and maybe 15nm @ 3.5 kW at 3.5-4kts. Your 34' cat should be as much as 50% more efficient than our "super-displacement" 32.5' WL hull.
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Old 06-12-2020, 13:49   #12
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Re: Electric motors on a Woods Flica 34' sailing catamaran

Sailor, you are a multihuller. So am I. Weight is everything on small multis. It is absolutely everything. Love Woods designs. I chose to go trailerable for a reason. I wanted portability and long distant roads to get to sailing venues.

You can look closely at Wharram cats and get a very good idea on how to effectively power a small cat. Multiple YouTube sailors like LuckyFish and many others who power up with outboards or electrics.

Some things to know that my friends have passed on to me. Yes, it can be done with electrics. It is sexy but it isn’t what you think. When you can just push a throttle and you get instant power and no smell, noise, or vibration... wow. No tainted gas... no clogged carb... no explosion compromises. Can it get any better?

But the other side of the coin... and there is always two edges to a knife, right? Have you ever seen the props on real electric motors? Let’s just say ... undersized and “really”? To say that you can compare electric to fossil fuel propulsion is a big fat ugly lie. Well... maybe not for a wealthy guy that can have 1000amp/hr bank and at least 1000 watts of solar ... and even then....

Last year I started early morning to cross from Mulege Mexico heading east to San Carlos. Crossing the Sea of Cortez is about 90 miles. I started at break of dawn. Sea breeze didn’t kick in till around 900 am. Just cat paws really. I need about 5-7 knots of breeze to put the asymmetrical up. So I was on outboard for 4 hours. I get about 7.5 mph at 75% power. Let’s just say I got 30 miles out from Mulege before I could get any sails working. Your electrics would have been tits up by 20 - 25 miles. Keep in mind this was very calm seas and wind very light.

Now fast forward. It is a 10-14 hour crossing. I have a pretty fast trimaran. Now you are sailing your Woods but your bank is hammered. Yes you can run your genset to trickle into the LiFePo4 bank. Yes you have solar to trickle in all day. But you have emptied your bank.

Now you are approaching the coast and the day breeze dies. Now you have current fighting you. Maybe the wind picks up from the wrong direction ... and it will always ... always on the nose... you have shipping to contend with... and an Anchorage that has many boats to deal with. Man... that is stress.

Electrics are fine for short trips. My buddy has an all electric Tri. When he depleted he just goes to sleep and waits for the batteries to recharge. And therein lies the danger. What if you can’t wait to close the coast? Small boats like yours and mine... have no business in heavy weather. Dangerous and scary as hell.

Woods has a lot of room for solar due to the acreage available. So, with decent size battery bank and solar you can achieve electric cooking, lighting, nav, auto pilot... but having a boat that won’t be compromised by battery storage???? Those who really know this subject are those who use it. My buddy tells me that his twin prop electrics don’t have the punch of his old 10 hp gas outboard by even 70% percent. Once you see the props in person you’ll understand.

Look into induction tops for cooking also. I have even seen monohull skippers who are full time cruisers go from diesel to electric sand then back to diesel after getting ito very dangerous situations with battery depletion vs navigation safety. Think wind against tide and it is all on your nose. Now think if you have a full bank on a flat day. Your range is 20-30 miles. What do you think your range is if wind, tide, and current opposes you? Maybe half that amount... those small props will not have the punch to get you through. Even sailing a tight beat with motors on won’t get you into safety. Weather deteriorating ... loved ones on board.... your call skipper.
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Old 06-12-2020, 15:07   #13
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Re: Electric motors on a Woods Flica 34' sailing catamaran

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Thank you tkeithlu for your thoughtful post. What do you think of one diesel with alternator in one hull and a electric inboard in the other hull.
Think you need to do more research on regen. Its great at 8 knots, okay ish at 6 knots and below that forget it, which is why we won't even try it with a cruising speed of 5-6 knots. Now, what will your average cruising speed be? or would it be better to invest the money in a bigger LFP bank which I think you will need.

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Old 06-12-2020, 16:56   #14
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Re: Electric motors on a Woods Flica 34' sailing catamaran

Blue water cruising and being self sufficient, but no mention of refrigeration. Power consumption for refrigeration goes up in the tropics. We found a slow cooker to be a better option than an electric stovetop or an air fryer. A lot less power consumption. Preparing your evening meal in the morning and having it ready to eat in the evening gives you a lot more free time to enjoy that sunset.
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Old 06-12-2020, 17:24   #15
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Re: Electric motors on a Woods Flica 34' sailing catamaran

1500 watt fryer is 12.5 amps at 120v. That would 125 amps at 12volts, not including inverter losses. That's a lot. Just saying.
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