Cruisers Forum
 


Join CruisersForum Today

Reply
 
Thread Tools Rate Thread Display Modes
Old 21-08-2015, 15:46   #46
Registered User

Join Date: May 2015
Location: Muskegon, Mi
Boat: Columbia 36
Posts: 187
Re: Electric Inboard

Electric powered boats have the same limitation as electric cars. If all you ever do is drive back and forth to work and have it plugged in at night, all's good. Want to take it out of town? You can't.
Diesel-electric propulsion is supposed to be more efficient than straight diesel. Most trains and many large ships are powered this way, but they still have diesel engines to run the generators. No real advantage in a smaller boat.
__________________

__________________
capt jgw is offline   Reply With Quote
Old 21-08-2015, 15:58   #47
Registered User
 
Wireless1's Avatar

Join Date: Jan 2012
Location: Southern California, USA
Boat: Beneteau 473
Posts: 145
Re: Electric Inboard

Quote:
Originally Posted by TacomaSailor View Post
Can we determine the power needed to move a Freedom 32 through still water?

The Yanmar Prop curve for the 3GM20 shows the following power at the prop for a given RPM:

2.0 HP 1800 RPM
2.9 HP 2000 RPM
3.0 HP 2100 RPM
3.3 HP 2200 RPM
3.9 HP 2300 RPM
4.5 HP 2400 RPM
4.9 HP 2500 RPM
6.0 HP 2600 RPM

What speed did the boat move at various RPMs - then we can determine the power the batteries need to supply for a given boat speed.

We can then use simple arithmetic to validate the various power and range claims being thrown around in this discussion.

Numbers - the truth!
You will probably want to look up the torque specs on the 3GM as this will give you the HP range that will best compete with the 10.5Kw PMAC motor. The PMAC will exhibit way better torque throughout it's range, in fact it's constant and even produces it's maximum torque at zero RPM, or what is called stall torque, and that is 60 Ft. Lbs. on the shaft but it's reduced 40:24 so...? Regarding "given boat speed"; although my system will do hull speed, max speed is not one of my requirements. If you want, or need to motor around all day at hull speed electric propulsion is not for you. Try to think of my philosophy as being more like this; Im a Lynn & Larry Pardey kind of a sailor. I don't mind going slow, waiting for the wind, and the only difference perhaps would be that I don't want to ask for a tow into the harbor when I get somewhere! I'll just flip on the switch and motor on in. LOL!

Now, the "truth" is that when at last the diesel was giving me hiccups I got it running good again, but I didn't get any detailed "numbers" on my boat because there was already good data from numerous other installations that were heavier than my boat and had less battery capacity then my system that I could look at. Also there are quite a few blogs where owners are reporting thier performance under electric power so I know I am better than "in the ballpark". However, I do know my Yanmar did move the boat at hull speed of about 6.5 knots + (1.37 * sq. rt. 26' LWL) at around 2,800 to 3,000 RPM which I felt was uncomfortably high for the little Yanny, so I usually motored around 5 Kts at 2,400 RPM or so, and was happy with that. The Freedom 32 displaces about 8,900 Lbs dry. Maybe you can work some numbers from the displacement and LWL of 26' and come up with something? BTW, there is a Nonsuch 30 named Bianca (sp?) that has a great website showing his installation and how it's all worked out for him over the last six or so years. His Nonsuch 30 displaces about 11,000 Lbs, a couple of thousand more than mine. He also has a small Honda generator as a backup in case he needs it---I may consider that too if a certain trip warrants it. However, I think he is running on AGM batteries, so I've got it all over his system with range because I'm using the LFP batteries.

There are lots of boats using these conversions now. Not because they are better than diesels but because they 'quietly', 'cleanly' and with less maintenance meet the owners requirements and desires. I gather this is totally not for you... But heh, no problem at all. Electric auxiliary sailboats are not everybody's cup o' tea, but I'd be wiling to bet that there are a LOT of people that use their diesels that would not lose any benefit in range or habitual use with switching to electric. With most weekend sailors they power out of harbor, day sail, and power back to the slip. Those would be the perfect candidates for electric conversion IF they were into it.

Anyway, if you want to run some projected numbers on my installation you are going to have your work cut out for you. You are going to have to compare a Yanmar 3GM30 with a KM3P gearbox at 2.36:1 using a 14x14 "inch" TWO blade propellor to a 10.5KW PMAC electric motor with cog belt drive reduction of 40:24 and a 16.5" THREE BLADE Kiwi variable pitch prop with pitch settings from 21 to 24 "degrees" (notice; NOT inches pitch---degrees pitch!). Maybe you can deduce a starting point on the pitch of the Kiwi prop? Or, how about how many amps I can generate at say 6 knots sailing while the Kiwi prop and Sevcon controller are putting amps back into my batteries? Now THAT would be cool!! But I rather think those numbers will be left up to actual data under sailing conditions rather than crunching numbers.

Anyway, we're sure having some fun with this project and I can't wait to get it completed and running! I've still got to do some of the dumb stuff now like glassing in a flooring under the dinette seat area for the batteries where the diesel fuel tank used to be. Then I have to fabricate compression end plates for each of the LFP battery packs. You need to have a moderate amount of compression on the battery pack so the individual cells can't swell up if they are charged at too high of a rate, or if they go into an overcharged state. Anyway, thanks for your interest and it will be interesting to see what you come up with.
(keep in mind, I'm interested in a 4 knot boat speed target @ 20AH discharge rate for maximum range, not water skiing! Ha!)

Fair winds and lots of bright solar sunshine!
__________________

__________________
s/v "Bamboleo" - Freedom 32 (Hoyt)
Farrier Trimaran -- Morgan 41 Classic,
Rawson 30
Wireless1 is offline   Reply With Quote
Old 21-08-2015, 16:22   #48
Registered User
 
Wireless1's Avatar

Join Date: Jan 2012
Location: Southern California, USA
Boat: Beneteau 473
Posts: 145
Re: Electric Inboard

Quote:
Originally Posted by capt jgw View Post
Electric powered boats have the same limitation as electric cars... ...Want to take it out of town? You can't...
Can't take it out of town? Maybe true with electric cars, or big power boats, but hey, this is a sailboat. I can take it anywhere in the world. And on a long passage, power regeneration under sail with a spinning prop shaft, (3 to 4 AH using the motor controllers regen mode ) plus the 600 watt solar panels (72 volts @ 8AH using MPPT chg reg.) can take their own sweet time charging the 48 volt propulsion battery pack to 100%. Thus it's possible to arrive in port with full batteries. Now THAT's something electric cars can't do. BTW, with a 48V DC to DC converter you can have a HUGE house bank in an emergency if your house batteries need some help, just cut in your propulsion bank to power the house...a nice backup.
YMMV
__________________
s/v "Bamboleo" - Freedom 32 (Hoyt)
Farrier Trimaran -- Morgan 41 Classic,
Rawson 30
Wireless1 is offline   Reply With Quote
Old 21-08-2015, 16:44   #49
Registered User
 
TacomaSailor's Avatar

Join Date: Nov 2012
Location: Burnt Store Marina, SW Florida
Boat: Caliber 40
Posts: 1,148
Re: Electric Inboard

I am astounded at the "head in the sand" and Pie in the sky" attitude amongst the electric boat advocates. They seem to think that electric motors driving propellers in the water can revoke the laws of physical motion.

"(keep in mind, I'm interested in a 4 knot boat speed target @ 20AH discharge rate for maximum range, not water skiing! Ha!)"

Simple electrical formulas show that 20 amps at 48V is 960-watts or 1.27 HP. That is half the horsepower of a small single cylinder Suzuki 2-stroke outboard. So - you propose to move your 8,900 pound boat with a 25' 3" waterline at 4-knots with just a little over one horsepower, or my tiny Suzuki running at half throttle?

Do you really think that putting a one cylinder 2-stroke on the back of your boat will move it at 4-knots while running half-throttle? Half throttle on my 2 HP Suzuki moves my 12' Portebote (320 pounds with me in it) at only 4-knots with me in it.

Something here does not compute!

I recently hooked my 2 HP outboard to a 32’ catamaran that weighs 3,200 pounds. At full throttle it moved the boat at 3-knots in still water. Trying to return to the dock into 10-knots directly on the nose was unsuccessful – we went backwards!

The formulas used to determine the MINIMUM power needed to move a displacement boat thru still water have been well known for decades. There can be little doubt as to the accuracy of those formulas, which describe the power needed at the propeller to move a boat thru the water. The Propeller does not care what the power source is: diesel, electric, human, or hamsters in a cage.

If a person knows their boat displacement and LWL they can calculate, with some assurance, the prop power needed to propel their boat. Given that number they can calculate, with great accuracy, the battery capacity and the electric motor size required to move a specified distance at a given speed.

That is not nay-saying and is not being a being a conservative proponent of the status quo - it is good engineering based on much measurement and experience.

Why in the world would a person spend tens of thousands of dollars to install a propulsion system without knowing the speed and range to be achieved with that system?

A Freedom 32 needs about 5 Prop HP (3.75 Kw) to move at 4 knots in still water. That power pulls 80 amps at 48V from a 320 Ah battery system. If you pull the battery down to 100% discharge you have a 16-NM ONEWAY range.

Those are facts, which describe the current state of energy storage in even the best LiFePO4 batteries. Wishing it were different is wishful thinking.

I love new technology and made a lucrative career designing and implementing that state of art stuff. But, I worked with scientists and engineers who made decisions based on data and proven formulas.

Good luck to all and I hope things work out as you wish.
__________________
TacomaSailor is offline   Reply With Quote
Old 21-08-2015, 17:02   #50
Registered User
 
micah719's Avatar

Join Date: Jul 2012
Location: Somewhere in Germany
Boat: OEM, proportional
Posts: 1,436
Re: Electric Inboard

Here are some conversion stories from Electric Yacht:

Conversion Stories | Electric Yacht

The same site has a motor sizing table (Tacoma is correct...):



The other threads on CF that I listed in my first reply in this thread contain much more info...let's keep it real, from both sides, so that folks can choose based on truth. Apples vs apples, oranges vs oranges.
__________________
Ps 139:9-10 If I take the wings of the morning, and dwell in the uttermost parts of the sea; Even there shall thy hand lead me, and thy right hand shall hold me.
micah719 is offline   Reply With Quote
Old 21-08-2015, 17:28   #51
Marine Service Provider

Join Date: May 2012
Location: New Orleans
Boat: We have a problem... A serious addiction issue.
Posts: 3,940
Re: Electric Inboard

Micah,

The stories for the most part confirm what has been said. There is no doubt the systems work, but they lack range. Which is absolutely fine if that works for you (did for me on my electric conversion), but for most cruisers is doesn't.

It isn't discussed, but it often brought up. Solar panels simply don't provide enough power to effect propulsion on most boats. It simply isn't realistic to install enough solar panels to make much of a difference to power demands while motoring.

Finally, regeneration... Absolutely works, and boats with high average speeds can make massive amounts of power this way. But you have to be able to maintain high average speeds. Knocking around at 3-4kn isn't enough, you need to be routinely in the 6-7kn range. Few boats are capable of these high average speeds. But if you can, go for it.
__________________
Greg

- If animals weren't meant to be eaten then they wouldn't be made of food.
Stumble is offline   Reply With Quote
Old 21-08-2015, 17:28   #52
Registered User
 
TacomaSailor's Avatar

Join Date: Nov 2012
Location: Burnt Store Marina, SW Florida
Boat: Caliber 40
Posts: 1,148
Re: Electric Inboard

“And on a long passage, power regeneration under sail with a spinning prop shaft, (3 to 4 AH using the motor controllers regen mode ) plus the 600 watt solar panels (72 volts @ 8AH using MPPT chg reg.) can take their own sweet time charging the 48 volt propulsion battery pack to 100%. Thus it's possible to arrive in port with full batteries.”


Here is another example of wishful thinking that ignores physical reality. Numbers do not lie!

I have a Ferris towed generator that produces 180 watts at 7-knots or 15 amps at 12V at 7-knots boat speed. That power production slows the boat about ľ knot. However, at 5-knots boat speed the Ferris only delivers 3 amps and slows our 40’ sailboat almost 0.4 knots. I have big solar panels and have used them at sea for over 6,000 NM. I know the reality of these processes.

Let’s assume you run the motor for 12-hours during a 5-day passage. Assuming the boat needs 4-HP (3 Kw) to move while at sea then a 48V motor would pull about 62-amps per hour or a total of 750 amp hours.

The regen process can provide 72 Ah per day or 324 Ah for the 4.5 days the electric motor is NOT providing power.

If the 600-watt panels average 50% power for 10-hours a day they produce 62 Ah per day or 310 Ah for the five day voyage.

If we assume the boat used 18 AH (48V) per day while under way for radar, lights, autopilot, refrigerator, radio then 375 Ah are consumed during the five day voyage.

Here is the result of a 5-day ocean voyage where you sail at least 4-knots for 90% of the time (everything is in 48V Ah):

-750 Ah motoring
- 90 Ah boat operations
+324 Ah motor regen process
+310 Ah Solar panel output

At the end of five days the batteries are down 205 amp hours or about 25% discharge on an 800 Ah battery bank.

Is there anything wrong with the calculations above?

Please remember I have lived with solar panels providing all the boat energy for 15-years including 6,000 NM at sea and over three years full time living at anchor. I have also skippered two other boats with big solar arrays for over 4,000 NM at sea.

I love alternate energy systems and that is why I am so obsessive about details and numbers.
__________________
TacomaSailor is offline   Reply With Quote
Old 21-08-2015, 19:23   #53
Registered User
 
micah719's Avatar

Join Date: Jul 2012
Location: Somewhere in Germany
Boat: OEM, proportional
Posts: 1,436
Re: Electric Inboard

If d-e were inherently inefficient it wouldn't be so popular with the big ships which really pinch pennies....they have the best opportunity to get optimum efficiency at constant speeds, it is their bread and butter.

If you want range, it's in diesel; how you get it to the prop can be done with a mechanical gearbox or an electric drive. I notice the thread isn't touching real-world efficiency of power transmission from generator to motor, to grabbing for straws in the form of re-gen and panels and ignoring the giant oily elephant trumpeting range! range!

Being able to re-gen even a small amount simply by letting the prop freewheel is another feather in the cap...it is enough to recharge for using a radio or nav system, and no extra towed gear needed. I can live with a knot less speed if that's what it took to get some charge when everything else was gone, especially when it is a free side-effect. It isn't a main consideration for me, but I'll take it since it comes with the package.

I'll say it again...it isn't for everyone, but the advantages are enough to make it attractive for some, and they aren't dolts or unrealistic dreamers. Thanks for trying but the arguments you are putting up aren't logical or cohesive...I can and have been convinced out of hare-brained schemes here on CF, but you're not making any headway on this one; ergo it isn't hare-brained. I'll grant you one has to go carefully about implementing it; the more experience is gathered with small-scale d-e, the easier and cheaper it will become. The folks with electric aren't chiming in....they've probably had enough in the various other times this has been "discussed". Some fresh links...

Diesel Electric Drive | Yachting Magazine
Diesel-electric propulsion pushes ahead - Professional Mariner - October/November 2007
The Quiet Alternative
__________________
Ps 139:9-10 If I take the wings of the morning, and dwell in the uttermost parts of the sea; Even there shall thy hand lead me, and thy right hand shall hold me.
micah719 is offline   Reply With Quote
Old 21-08-2015, 20:32   #54
Registered User
 
ozskipper's Avatar

Join Date: Aug 2010
Location: NSW Australia
Boat: Traditional 30
Posts: 1,981
Re: Electric Inboard

There is a lot of great info in this thread. But it really comes down to the intended use of the motor. If its just to get a boat on and off a mooring or marina I can see an electric motor as a really sensible alternative to Diesel-eg. for a club racer who never goes to sea or does long journeys.

On the other hand, I certainly wouldnt want to rely on an electric system on coastal journey of several days. As the need to generate extra sparks is so high, it would still require the installation of some sort of combustion engine. Thus, negating its advantages. .
__________________
Cheers
Oz
...............
ozskipper is offline   Reply With Quote
Old 21-08-2015, 20:33   #55
Marine Service Provider

Join Date: May 2012
Location: New Orleans
Boat: We have a problem... A serious addiction issue.
Posts: 3,940
Re: Electric Inboard

Micah,

There is no doubt that in some applications DE makes a lot of sense. But none of those really apply to a small yacht. Unless you are planning on installing multiple diesel generators that can be ganged together a direct drive is almost always more efficient.

Testing has proven that the only efficiency gain for recreational boating can be found for those people who are just motoring out of the harbor and then turning off the engine. But the gain here is so small that it will never be economically justified. And you pay heavily if you want to operat at cruising speed for any distance.

See Power | PassageMaker | | PassageMaker for the three articles by Nigel Calder

Below is the actual efficiency chart comparing a direct diesel drive and a hybrid. As you can see there is a very minimal efficiency gain at low speeds, which is quickly lost as speed increases.
Attached Thumbnails
Click image for larger version

Name:	image.jpg
Views:	116
Size:	68.4 KB
ID:	107747  
__________________
Greg

- If animals weren't meant to be eaten then they wouldn't be made of food.
Stumble is offline   Reply With Quote
Old 21-08-2015, 21:20   #56
Registered User
 
Kokanee's Avatar

Join Date: Jan 2013
Location: Adelaide Australia
Boat: Cuddles 30ft Motor Sailer
Posts: 216
Re: Electric Inboard

Quote:
Originally Posted by Stumble View Post
Micah,

The stories for the most part confirm what has been said. There is no doubt the systems work, but they lack range. Which is absolutely fine if that works for you (did for me on my electric conversion), but for most cruisers is doesn't.

It isn't discussed, but it often brought up. Solar panels simply don't provide enough power to effect propulsion on most boats. It simply isn't realistic to install enough solar panels to make much of a difference to power demands while motoring.

Finally, regeneration... Absolutely works, and boats with high average speeds can make massive amounts of power this way. But you have to be able to maintain high average speeds. Knocking around at 3-4kn isn't enough, you need to be routinely in the 6-7kn range. Few boats are capable of these high average speeds. But if you can, go for it.
Nice summary, Greg.

When I needed to replace my old Volvo plus my fuel tanks, I came up with similar conclusions after much research.
I really wanted to go electric, and it was certainly do-able, but to get the range I required was going to cost more than double what it cost to replace the diesel as well as the tanks. I couldn't justify the additional expense.
__________________
Kokanee is offline   Reply With Quote
Old 21-08-2015, 21:45   #57
Registered User
 
TacomaSailor's Avatar

Join Date: Nov 2012
Location: Burnt Store Marina, SW Florida
Boat: Caliber 40
Posts: 1,148
Re: Electric Inboard

"I'll say it again...it isn't for everyone, but the advantages are enough to make it attractive for some, and they aren't dolts or unrealistic dreamers. Thanks for trying but the arguments you are putting up aren't logical or cohesive"

SO - Show me where the numbers are wrong! If the arguments are illogical or incoherent then it should be easy to provide NUMBERS that show my calculations are in error.

This discussion is not about emotion or feelings - it is about mechanics and physics - rules and formulas that have been in use for many decades. If I am not applying the formulas correctly or properly - then show me where my use of the rules and arithmetic are incorrect.

The ONLY advantage is QUIET operation. Otherwise, DE in a small boat is more expensive, less efficient, and provides far less range and flexibility of usage.

Show me, with numbers - NOT "I wish it were true ideas" where lie the advantages of DE in a small sailboat.

IF - there are such obvious advantages - why hasn't Hunter, Beneteau, or Catalina ( high efficiency and low cost manufacturers) implemented DE and gained market share thru those obvious advantages?

I've provided detailed numbers that should be easy to refute if incorrect - have at it!
__________________
TacomaSailor is offline   Reply With Quote
Old 21-08-2015, 22:12   #58
Registered User
 
Wireless1's Avatar

Join Date: Jan 2012
Location: Southern California, USA
Boat: Beneteau 473
Posts: 145
Re: Electric Inboard

Quote:
Originally Posted by TacomaSailor View Post
I am astounded at the "head in the sand" and Pie in the sky" attitude amongst the electric boat advocates. They seem to think that electric motors driving propellers in the water can revoke the laws of physical motion.

"(keep in mind, I'm interested in a 4 knot boat speed target @ 20AH discharge rate for maximum range, not water skiing! Ha!)"

Simple electrical formulas show that 20 amps at 48V is 960-watts or 1.27 HP. That is half the horsepower of a small single cylinder Suzuki 2-stroke outboard. So - you propose to move your 8,900 pound boat with a 25' 3" waterline at 4-knots with just a little over one horsepower, or my tiny Suzuki running at half throttle?

Do you really think that putting a one cylinder 2-stroke on the back of your boat will move it at 4-knots while running half-throttle? Half throttle on my 2 HP Suzuki moves my 12' Portebote (320 pounds with me in it) at only 4-knots with me in it.

Something here does not compute!

I recently hooked my 2 HP outboard to a 32í catamaran that weighs 3,200 pounds. At full throttle it moved the boat at 3-knots in still water. Trying to return to the dock into 10-knots directly on the nose was unsuccessful Ė we went backwards!

The formulas used to determine the MINIMUM power needed to move a displacement boat thru still water have been well known for decades. There can be little doubt as to the accuracy of those formulas, which describe the power needed at the propeller to move a boat thru the water. The Propeller does not care what the power source is: diesel, electric, human, or hamsters in a cage.

If a person knows their boat displacement and LWL they can calculate, with some assurance, the prop power needed to propel their boat. Given that number they can calculate, with great accuracy, the battery capacity and the electric motor size required to move a specified distance at a given speed.

That is not nay-saying and is not being a being a conservative proponent of the status quo - it is good engineering based on much measurement and experience.

Why in the world would a person spend tens of thousands of dollars to install a propulsion system without knowing the speed and range to be achieved with that system?

A Freedom 32 needs about 5 Prop HP (3.75 Kw) to move at 4 knots in still water. That power pulls 80 amps at 48V from a 320 Ah battery system. If you pull the battery down to 100% discharge you have a 16-NM ONEWAY range.

Those are facts, which describe the current state of energy storage in even the best LiFePO4 batteries. Wishing it were different is wishful thinking.

I love new technology and made a lucrative career designing and implementing that state of art stuff. But, I worked with scientists and engineers who made decisions based on data and proven formulas.

Good luck to all and I hope things work out as you wish.
Uh, Mr. engineer? You are tipping your agenda driven hand when you lump all electric boat advocates into one group as "pie in the sky" "head in the sand" people. I am sorry if I give you that impression, I don't mean to, but there are many VERY qualified engineers, even more knowledgeable and qualified than you that are putting out proven designs that work. Of course they don't measure up to someone's "driving at hull speed" for days requirements, but many people such as myself are fine with the limitations as we feel there are other things that outweigh the installation of a new diesel.

As to your engineering numbers? I see one number in your mentioned "laws of physical motion" that you say all the electric advocates are all revoking, and yet you left out any reference to it and that word is torque. I see no mention of torque in your calculations. Why? It's one of the most important things an electric motor has to offer. It allows you to get similar performance out of a much smaller HP motor when compared to a diesel. You have not mentioned that or calculated for it. I am going to be able to swing a much bigger prop than the Yanmar diesel could swing. So, how can my little 60 Lb electric motor do that? Don't you think torque is worth mentioning and factoring in to your calculations? You simply cannot equate the horse power from an ICE (internal combustion engine) and say it is the same as an electric motor.

Also, your calculations don't even come close those of the "real world" factory numbers. The Electric Yachts company has calculated their performance curves for my boat. These curves were taken from data of over 300 installations to date, and one of those installations just so happens to be a Freedom 32 just like mine. So I will defer to the engineers that actually make these things and have tested the real world data being produced.

I hope the numbers below will give you some food for thought in your calculations. Here you go >> (it's from a graph so I will interpolate as best I can).
Motor: 10Kw PMAC @ 48 Volts
Shaft HP: 9 with 40:24 reduction
Prop: 15" x 12" (I have gone up to a 16.5" variable pitch Kiwi feathering prop)

Amps vs. Speed Graph
10 amps - 2.4 knots
20 amps - 3.2 knots (hoping to squeeze another .8 knots our of my variable prop?)
40 amps - 4.5 knots
65 amps - 5.0 knots
80 amps - 5.5 knots
120 amps - 6.3 knots
180 amps - 7.0 knots

RANGE calculated @ 90% depth of discharge for my 380AH LiFePO3 48 volt pack
(Electric Yachts calculated my range using only 240AH (useable) of LFP, but I have 342AH useable LFP)
So I am using their amp/speed numbers but my AH capacity and recalculating;
90% DOD of 380 AH = my 342 useable Amp Hours.
(342AH) / (amp draw) = (motor hours of running)
(hours of running) * (boat speed) = distance
Therefore range =
2.4 knots - 82.8 miles (34.2 hrs @ 10A)
3.2 knots - 54.7 miles (17.1 hrs @ 20A)
4.5 knots - 38.5 miles (8.5 hrs @ 40A)
5.0 knots - 26.3 miles (4.2 hrs @ 65A)
6.3 knots - 17.9 miles (2.85 hrs @ 120A)
7.0 knots - 13.3 miles (1.9 hrs @ 180A) Crazy inefficiency, maybe only needed in panic mode...

So sorry, but your numbers don't add up to what the manufacturers are getting from these high torque electric motors. I suggest you factor in the torque these motors provide, as most people like to re-prop upward after electric motor installations.

Now, since you love numbers, I suggest you left out some serious ones in your flawed Suzuki 2 stroke outboard analogy. Not only did you leave out torque, but you have left out prop slip calculations on your hi-reving Suzuki 2 stroke engine. Two strokes love and need their hi-revs to get horse power and that's great for certain things like go karts. But, your little Suzuki didn't have the torque (a word I don't hear you mention ever) to swing a pusher type prop, so the little Suzuki sat there going nowhere, engine screaming, prop slipping like crazy. As to real world? Now listen up: I have moved my Rawson 30, 12,500 Lbs full keel displacement sloop at 4 knots (in harbor, flat water) with my little 2 HP Honda 4 stroke outboard. And that was even with the extra drag from my dinghy because I had the Honda on my dinghy and rigged as a yawl boat on the stern quarter. I would think that the Honda 4 stroke had way more prop thrust form its torque than your little Suzuki, so the Honda could swing a properly designed prop more for pushing than high revving. (The downfall of your hi-reving Suzuki two stroke?---low torque and prop slip under load!). And on top of that; what about the enormous windage loads on that big cat you were trying to push upwind versus a monohull? If you want to correct those windage and prop slip factors and re-calculate the efficiencies or lack thereof between the 4 stroke Honda pushing the Rawson 30 at 4 knots not at full throttle, versus 2 stroke 2 HP Suziki screaming wide open pushing the hi-windage 32 foot catamaran to weather, I'll be happy to look at them, but for now? I'll take your Suzuki analogy for what it is, a funny story, and I more than get your agenda on this subject. But remember; your agenda, is not MY agenda and I hope that's OK. So for now, enough apples and oranges.

Now, I will be sure and report back in as to what I find out with my own tests on my Freedom 32. I know based on others real world examples and the manufacturers test data that I can do better than your projected 16 mile range (one way), as long as I don't put the pedal to the metal. And in any case I am sure I will enjoy my setup way more than my old unreliable smelly noisy diesel. (There are no range/speed numbers for smell and noise factors), so I will love the "pie in the sky" quiet, no diesel smell, and no noise. So basically we can see that under electric power the range is a function of speed, and therefore you can turn the range up or down as the conditions permit. Perhaps even adding in a little silent motor sailing too when it gets to be light air with cats paws on the water. Anyway, I anticipate that I will be somewhere close and in the ball park of the factory projections rather than yours. It will be interesting too when I add in the 600 watts of solar dedicated solely to the propulsion bank. Even adding about 450 watts throws another 2/3 HP into the propulsion battery mix, but I'm not going to add that in until everything else in the installation is completed and working properly.
Cheers!
__________________
s/v "Bamboleo" - Freedom 32 (Hoyt)
Farrier Trimaran -- Morgan 41 Classic,
Rawson 30
Wireless1 is offline   Reply With Quote
Old 21-08-2015, 22:30   #59
Registered User
 
Wireless1's Avatar

Join Date: Jan 2012
Location: Southern California, USA
Boat: Beneteau 473
Posts: 145
Re: Electric Inboard

Quote:
Originally Posted by micah719 View Post
Here are some conversion stories from Electric Yacht:

Conversion Stories | Electric Yacht

The same site has a motor sizing table (Tacoma is correct...):



The other threads on CF that I listed in my first reply in this thread contain much more info...let's keep it real, from both sides, so that folks can choose based on truth. Apples vs apples, oranges vs oranges.
I'm seeing the info on the graph just fine, but I don't get what you are seeing that makes TacomaSailor "right" and what? Me wrong? I'm using the Electric Yacht Systems 10.5Kw PMAC motor. It's slightly over sized for my 8,900 Lb. displacement Freedom 32. So what do you see that is not right about my system? What am I missing here?
BTW, my LFP battery pack is oversized at 21kWh capacity and per their chart more typical of a 45 foot boat installation. So would you mind sharing what is wrong with any of this in your opinion?

Thanks!
__________________
s/v "Bamboleo" - Freedom 32 (Hoyt)
Farrier Trimaran -- Morgan 41 Classic,
Rawson 30
Wireless1 is offline   Reply With Quote
Old 21-08-2015, 23:09   #60
Registered User

Join Date: Apr 2015
Location: NC
Boat: 1974 Morgan Out Island 33
Posts: 552
Re: Electric Inboard

Quote:
Originally Posted by valhalla360 View Post
If you are willing to accept 3.5kt crusing speed, you need to drop the diesel down to maybe 3-5hp and take into account the improved efficency to do a comparison. Now you might be talking about 45miles on a couple gallons fuel. A fairly typical 100 gal tank would provide ocean crossing capability.

Of course, if you get into a storm and your sails blow out, your system will be SOL trying to hold you in place. Or if you take it up to a half way reasonable cruising speed and your range drops back the 5-10miles we've been talking about.

For a die hard doing it just to prove they can use electric, 3.5kt cruising speed is fine. For a cruiser looking for the best all around propulsion system it's not viable and that's why retail systems haven't taken off.
Do you have something to prove? Do you feel challenged by this conversation? You don't want electric, we get it. You seem very determined to convince people who already use it that it doesn't work for them.

I was just watching a very long video by a highly esteemed source about using stay sails and para anchors to heave to in storms. So there ya go on that argument.

You see what I am doing? The same thing you are doing.

What I have learned from this forum is that there is no "a cruiser". There are about a bajillion cruisers, each unique individuals with unique ideas. You are one.

We get that Diesel has a bajillion to one edge on calories / lb over batteries. That is soooooo old news. How many more times must we hear that?

The way I read it Wireless1 one loves his system. He has admitted it is not for you. You have beaten the crap out of everyone else. Every time this subject comes up the "pro diesel" crowd beats the crap out of the electric crowd. I personally am interested in the subject of electric propulsion, and so have read every thread, and have watched the beating take place. It would be humorous if it weren't so sad. It almost feels as if the diesel crowd is personally afronted that their propulsion choice not desired by some.

</Soapbox>

Let the beatings resume.
__________________

__________________
Order tends to Chaos. On the ocean it happens twice as fast.
jwcolby54 is offline   Reply With Quote
Reply

Tags
electric

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
For Sale: Sailboat inboard electric motor system for sale lazystar@aol.com Classifieds Archive 9 12-03-2015 10:01
For Sale: PAR Electric System Water Pump and JABSCO Electric Bilge Pump hanks Classifieds Archive 3 05-03-2014 20:03
For Sale: Electric Motors and hydraulic electric lifter arms 4 sale Sea Shoes Classifieds Archive 0 25-03-2012 08:46
Replacing Inboard Engine with Electric Motor boat_alexandra Engines and Propulsion Systems 10 30-12-2009 21:50
Electric consumption of Inboard autopilots. Tonick Monohull Sailboats 7 10-01-2009 05:21



Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 14:50.


Google+
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.