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-   -   Gemini 105mc conversion Diesel to EV? (https://www.cruisersforum.com/forums/f48/gemini-105mc-conversion-diesel-to-ev-227198.html)

storx 01-12-2019 03:59

Gemini 105mc conversion Diesel to EV?
 
Hello All,

I am curious if anyone has converted a Gemini 105 to EV yet? I am asking because yesterday I went and walked 1996 Gemini 105 that needs a bit of work, but within the price we talked about is looking to be a decent starting point. I know there are many videos of people scraping the diesel engine in favor of a gas outboard, but with my background of building electric bicycles for fun and owning a tesla model 3, the idea popped in my head of going the EV route. While looking at the boat, the owner was able to start the diesel engine, but it ran very poor and shook pretty violently and while looking at it i noticed there was a leak coming from the side of the engine block and closer inspection appears to be a hairline crack in the block of the engine near the head, so the engine is shot basically. After talking to the owner about that and a few other things i noticed, he threw out the price of 35k on the purchase and i told him i would get back with him after giving it some thought and also told him i gotta talk it over with the other half (don't have a other half at the moment, so a bit of a fib), but just wanted to buy time to think this over.

So the idea i was thinking was pulling the diesel engine, but leave the prop head and attach the electric motor to it for propulsion instead of re-inventing the wheel completely. I also looked into the company i buy my electric bike motors from and they offer a 96v 50kw max/25kw continous Motor/Controller kit for $2400, which could be combined with 4s x Tesla Model S battery modules for bare minimum battery pack for $3600.

harlem24 01-12-2019 04:05

Re: Gemini 105mc conversion Diesel to EV?
 
Hi,

take a look at some yt channels like Sailing Uma, Rigging doctor or Beau and Brandy sailing. They all converted sailboats to electric. Beau and Brandy used the batteries of a Chevy Volt in a 48V config.
Sounds interessting, please keep us updated.

storx 01-12-2019 04:36

Re: Gemini 105mc conversion Diesel to EV?
 
Quote:

Originally Posted by harlem24 (Post 3026884)
Hi,

take a look at some yt channels like Sailing Uma, Rigging doctor or Beau and Brandy sailing. They all converted sailboats to electric. Beau and Brandy used the batteries of a Chevy Volt in a 48V config.
Sounds interessting, please keep us updated.

I will check those out, the chevy volt cells are very cheap, but extremely heavy compared to tesla cells and i would imagine on a boat, weight is KING....

I guess i was more or less curious whats a good target amount of kw of power needed for power cruising if not sailing... The owner told me in the past he would only cruise @ 50% throttle and based on that knowledge and the diesel engine maxing at 20kw output, in a "oh ****" situation i was thinking around 20kw continous would be needed to hopely get out of danger...

harlem24 01-12-2019 04:40

Re: Gemini 105mc conversion Diesel to EV?
 
Not sure, but if you check the electric beke vids of sailing Uma, they test their electric motor somewhere in a channel in Florida and afair they needed 20-30A with a 48V system to go around 4-5kn.
They have a 36ft 70s mono.

Sparx 01-12-2019 05:05

Re: Gemini 105mc conversion Diesel to EV?
 
I am thinking a 50kw max/ 25 kw continuous is a very nice size to push that boat. Evaluating propeller sizing and the impact of the transmission system is warranted, given the electrical motor may be quite happy turning at lower rpm than the diesel.

harlem24 01-12-2019 05:22

Re: Gemini 105mc conversion Diesel to EV?
 
Have a look at this, some interessting insigts.

https://www.sailinguma.com/the-motor

storx 01-12-2019 05:26

Re: Gemini 105mc conversion Diesel to EV?
 
Quote:

Originally Posted by harlem24 (Post 3026898)
Not sure, but if you check the electric beke vids of sailing Uma, they test their electric motor somewhere in a channel in Florida and afair they needed 20-30A with a 48V system to go around 4-5kn.
They have a 36ft 70s mono.

That seems very low... thats only about 1.5 to 2.0kw output if those numbers are real.. thats very low power usage to do 4-5knots.

Since the origional drivetrain is designed for low rpm engine, a DC based motor would benefit in this case, since DC motors are more effecient at low rpms and produce more torque vs AC motors, which are more effecient at higher rpms, thus why electric cars are AC based or some sort of dual DC/AC based like the Tesla, which uses DC for low-end and low speeds on the Model S and AC side of the motor for higher speeds.

storx 01-12-2019 05:31

Re: Gemini 105mc conversion Diesel to EV?
 
Quote:

Originally Posted by harlem24 (Post 3026915)
Have a look at this, some interessting insigts.

https://www.sailinguma.com/the-motor

Ah, i see... they went with an old forklift motor.. very very old technology, but very reliable due to how tuff they build them to withstand high amp spikes... That motor maxes at only 4.8kw, which is far less power than i expected to do 4-5 knots...

The motor kit im looking at is from a china based electric 2 seater car with max speed of 75kmh. Maybe something smaller could do the job based on the Uma setup results.

harlem24 01-12-2019 05:36

Re: Gemini 105mc conversion Diesel to EV?
 
Just looked at their website: Electric yachts says that they need 5.7kW to go 5.6kn.
With a 7,5to 36ft boat.
And they actually have now a 4.8kW motor with direct transmission.

harlem24 01-12-2019 05:38

Re: Gemini 105mc conversion Diesel to EV?
 
And most of the time they sail, cos it's a sailboat...;)

storx 01-12-2019 06:00

Re: Gemini 105mc conversion Diesel to EV?
 
Another option is something like this... if that little of power is really only needed for propulsion... these kits can be had for around $3k... but I kinda like the inboard motor route better...

https://youtu.be/QsH6QKBuz1g

storx 01-12-2019 06:11

Re: Gemini 105mc conversion Diesel to EV?
 
Quote:

Originally Posted by harlem24 (Post 3026923)
Just looked at their website: Electric yachts says that they need 5.7kW to go 5.6kn.
With a 7,5to 36ft boat.
And they actually have now a 4.8kW motor with direct transmission.

hmm, if that is the case, then its probably a 10 to 15kw motor, because 5.7kw continuous is typically a 1/3rd to 1/2 of the max power on most motors I see...

harlem24 01-12-2019 06:25

Re: Gemini 105mc conversion Diesel to EV?
 
Electric yachts proposed a 20kW motor for their boat.

StuM 01-12-2019 08:02

Re: Gemini 105mc conversion Diesel to EV?
 
Quote:

Originally Posted by storx (Post 3026896)
I guess i was more or less curious whats a good target amount of kw of power needed for power cruising if not sailing... The owner told me in the past he would only cruise @ 50% throttle and based on that knowledge and the diesel engine maxing at 20kw output, in a "oh ****" situation i was thinking around 20kw continous would be needed to hopely get out of danger...


"power cruising"? What sort of range do you want? How are you going to recharge your batteries? Battery bank size and energy sources are the major constraints with EP. You need to clarify your use case.

Semloh 01-12-2019 08:28

Re: Gemini 105mc conversion Diesel to EV?
 
I would think your system would need to be similar in size to this boat.

https://www.youtube.com/channel/UCj0...XZzyKqZz4cu-yg


He is estimating 11 hour run time at 3 knots. No feasible way to recharge while cruising that I can see.

Semloh 01-12-2019 08:38

Re: Gemini 105mc conversion Diesel to EV?
 
search for his Facebook page with lots of info about his system

alvejakten

captlloyd 01-12-2019 09:01

Re: Gemini 105mc conversion Diesel to EV?
 
Quote:

Originally Posted by StuM (Post 3026987)
"power cruising"? What sort of range do you want? How are you going to recharge your batteries? Battery bank size and energy sources are the major constraints with EP. You need to clarify your use case.

Exactly and with a 105 you would probably being doing a fair share of motor sailing too. :whistling:

skipmac 01-12-2019 09:08

Re: Gemini 105mc conversion Diesel to EV?
 
Hi Storx,

Sorry if I missed this point but can you post the source for your 50kW bike motor and controller?


Thanks

dperchlik 01-12-2019 11:50

Re: Gemini 105mc conversion Diesel to EV?
 
Remember that 20kW at 48v is over 400amps!
You will never get 20kW if your system and internal battery resistance is more than a few milli ohms. 1mOhm x 400amps = 0.4V and I2R = 160watts.

Cadence 01-12-2019 12:32

Re: Gemini 105mc conversion Diesel to EV?
 
If the engine is bad how is the rest of the boat as it pertains to sailing?
I could be wrong but believe the drive was through a leg. I've read have problems hence the OBs.
FYI

zstine 01-12-2019 12:36

Re: Gemini 105mc conversion Diesel to EV?
 
just thinking outloud....

50kW = 67Hp way more than you need. The OEM motor is 27Hp per sailboatdata.com and owner says 50% throttle @ cruise... 20kW max motor (=27Hp) seems big enough. EVwest 27Hp moto model AC-9 is $2,625

EVwest model S battery spec 5.3kWh, 22.8V, $1580 each (4x 21.2kWh & $6,320)

so cruising at 50% OEM HP ( = 10kW draw) you will only be able to run 2 hours before you kill 4 model S batteries! that's about a 10 mile range, which is fine if you are willing to wait for wind to go any significant distance.

Charging is a big issue too. What's the point of running EV if you need a generator to charge the batteries. Are you going to be a dock queen and recharge via shore power? If not, you need a lot of solar. assuming you can get rated output for 5 hours (eg. tropics), you need 4000 watts of panels, or about 14 of the big 60 cell roof panels. That's certainly more real estate than you have... and again, that's for a 10mile range.


Cost of panels ~$1/watt or $4,000 plus mounting, charge controller, wiring... maybe $6-$8k if you DIY. plus the above batts and motor add ~$9k. So you are looking at least $15,000 probably closer to $20k all said and done.

KP44 01-12-2019 13:31

Re: Gemini 105mc conversion Diesel to EV?
 
I was talking to another sailor in the yard yesterday about an electric boat. The sailor says it has a huge solar array and seems to be OK. I don't remember where he said it is. There are others. But I don't know of any ocean cruisers except experimental vessels that have (almost) unlimited funding and support.

If given the opportunity, I would have repowered with a motor instead of an engine. The extra weight could be made up with batteries, and maybe a diesel gen-set.
If the technology has improved, it's probably the way to go.

harlem24 01-12-2019 14:19

Re: Gemini 105mc conversion Diesel to EV?
 
As I said, look at the Sailing Uma website.
For them it seems to work. They been in all of the caribean, up the east coast and just crossed the Atlantic to England.
They have two solar panels and about 14kWh of LiFePo4 batteries.
Not sure if they have working regen.

harlem24 01-12-2019 14:21

Re: Gemini 105mc conversion Diesel to EV?
 
Quote:

Originally Posted by KP44 (Post 3027201)
I was talking to another sailor in the yard yesterday about an electric boat. The sailor says it has a huge solar array and seems to be OK. I don't remember where he said it is. There are others. But I don't know of any ocean cruisers except experimental vessels that have (almost) unlimited funding and support.

If given the opportunity, I would have repowered with a motor instead of an engine. The extra weight could be made up with batteries, and maybe a diesel gen-set.
If the technology has improved, it's probably the way to go.

Sailing Uma and Rigging doctor both crossed the Atlantic and both are non-professional sailor with electric engines and very limited funding...

warrior 90 01-12-2019 15:27

Re: Gemini 105mc conversion Diesel to EV?
 
Here are my 2 cents

First of all
The Westerbeke engine is a marine conversion of the Mitsubishi L3E engine. This engine was used in tractors, construction machines and what not ?? all over the place and replacement engines to spares are easy to find and dirt cheap. This is a very good engine if maintained properly and fuel consumption is close to nothing. The two 18 gallon fuel tanks will give You a very nice range for Coastel, ICW and Caribbeans.

THE EV ROUTE
Following is the web site from Sillete, the manufacturer of the Sonic Type 2 drive that is installed on the Gemini together with the 27 Hp Westerbeke engine.
https://www.sillette.co.uk/sonic_typ...ran_drive.html

Watch the rated HP ratings = Torque Loads !!!
A 50 Kw motor has way too much torque and even with 25 KW you are getting close to the upper limits.
As You can see they also have an electric sail drive version but itīs a little different then the outdrive version. However the parameters as far as motor sizing, torque loads, reductions and prop size to match with the Sonic drive are similar.
https://www.sillette.co.uk/sonic_ele...saildrive.html
They are working with Lynchmotors in the UK and they use a very cheap and high efficient DC pancake motor. Even so the motor has not a high IP insulation rating in case of the Gemini 105 with a totally dry engine compartment this will not be a problem. This lower IP rating on the flip side will give You a much better heat dissipation/cooling, which is Your mayor concern for electro motor efficiency. It is also a brushed motor but here are YT videos to give You an idea what You are up to in case of trouble shooting and repair......
In any case.... since these motors are so cheap and easy to repair and replace. I would always keep a complete spare motor on board.....
The Lynch Motor
A very unique design with a lot of history in racing and DIY and definitely a legend
https://www.youtube.com/watch?v=rmdamS2bjYc
https://www.youtube.com/watch?v=U13r_tkHxuY

What You also definitely wanna evaluate on a Gemini is the weight of the motor, weight of the total installation and weight distribution. The Westerbeke with the transmission according to spec sheet is 274 Lbs + 36 gal of fuel

So here is the Lynch motor Mod. LEM 200 up to 15 KW.....
https://lynchmotors.co.uk/pdfs/lmc-lem-200.pdf
As You can see the best efficiency rate is around 4100 RPM. That is way higher then the Westerbeke shaft power curve. So with the proper reduction You should have no problem to match the Sonic drive to Your desired spes even without changing the prop which is a lot cheaper. Here is a close up photo on the bottom that shows the easy principles of designing Your own motor mount set up with the proper gear.
https://lynchmotors.co.uk/marine_mar...ive-boats.html
and also here
https://www.youtube.com/watch?v=uwa1M85q8Ao

Here are some suppliers for the " TIMING PULLEYS & BELTS " which is a lot more flexible and simpler power tran then using gears > easy change, no lube, no maintenance, cheap .......
https://www.motionindustries.com/tax...leys/browse/en
You can also check on Amazon...
https://www.amazon.com/Boston-Gear-D.../dp/B006R9AH5Q

However depending on where and how You wanna use the boat. You can also go to a higher KW motor.
Here is the Mod. LEM 2x2.....
https://lynchmotors.co.uk/pdfs/lmc-lem-2x2.pdf

This is the same motor but with two identical motors mounted on the same shaft.
This will give You two motors in one for added safety when one motor fails but the mounting to the Sonic Drive will be still as simple as with only one motor.
Of course now You also have double power but with less heat.

If You should decide to go with Lithium here are my preferd sources for reasons of price
Winston Battery, CALB, LiFePO4 Battery - Evlithium
https://www.ev-power.eu/Winston-12V-sets/
I like the BMS 123 Smart from EV-Power for itīs simplicity. Also has Bluetooth
https://www.ev-power.eu/Battery-Mana...tooth-4-0.html

Carefully watch the details on this YT channel and form Your own opinion
https://www.youtube.com/channel/UCRq...QdaU_ePXfMD9xA

He did an of the shelf conversion with those motors many years ago and now upgraded to 72 Volts with a new controller with way much better results.
As You might realize he built this system by himself. Now go to all them beautiful YT channels here mentioned and ask Yourself. What are You going to do if there is a problem. Can You fix it Yourself ? Where do I get the spare parts. What tools do I need on board ? What will Your situation look like if You canīt fix it Yourself ?

!!! Further considerations...... there is different legislation "DEPENDING ON COUNTRY ".... in ref to boat safety ,insurance cover etc. for EV installations on boats for up to 48 Volts and over 48 Volts.
In regards You should also pay VERY SPECIAL ATTENTION to the facts that standard in the Gemini the propane gas bottle sits right next and all open to the engine compartment and standard the fridge also is 110 V /propane with a constant open flame.

Of course there is also the less spectacular but very valid conversion to an electric outboard engine as You mentioned.

And of course there is always the big question. How will You charge the batteries ???

On the Gemini there is comfortable space for ca. 400 w of latest solar tech + maybe some additional panels on the life lines. Thatīs barely enough for consumers on board. I donīt see space for a lot more green dreams without the help of some dino fuel on board.

So things are adding up. If You wanna start a YT channel I am sure there will be a lot of attention. However if You wanna get on the water and go sailing I am sure the Mitsubishi lawnmower engine might be worth while thinking.

Further more ..... make a VERY VERY deep inspection of the Sonic Drive. There are issues with the reverse release and other little tricky tid bits. Sillette has a good customer Service but spare parts for the Sonic Drive are unique and expensive. I also heard some unconfirmed rumors that Sillette will stop to manufacture the Sonic Drive.

Good Luck and Cheers

Scaramanga F25 01-12-2019 15:31

Re: Gemini 105mc conversion Diesel to EV?
 
At way below hull speed on catamarans with modern electric propulsion, you are lucky to ger 3 hours of operation and these have 8 solar panels and more than 8 batteries. Their weight is much more than a diesel engine.
It will not get off in a grounding. Fix the diesel or use an outboard(s).
Big mistake. Experience.

mikedefieslife 01-12-2019 16:54

Re: Gemini 105mc conversion Diesel to EV?
 
Quote:

Originally Posted by harlem24 (Post 3027236)
As I said, look at the Sailing Uma website.
For them it seems to work. They been in all of the caribean, up the east coast and just crossed the Atlantic to England.
They have two solar panels and about 14kWh of LiFePo4 batteries.
Not sure if they have working regen.

I'm not sure it does. Well maybe now but originally, it seemed a very poor system. slow and extremely limited range saw them struggling a lot, and having to spend hours tacking up estuaries and the like. They talked about how light the motor was, and ignored the fact the lead acid batteries they put in at the time weighed more than the engine and fuel combined.

I've not really seem them use since the sponsored switch to an LFP bank. That is has possibly made it more practical.

In answer to the OP's question, there are undoubtably some Gemini's that converted to EV, years ago I saw a YT video on one running a LFP bank. Again it was limited.

Personally, I would love an electric motor as auxiliary power. On a cat it would be possible to have both. Outboard or dropdown pod mounted electric motors and an outboard as a backup

johnny AoB 01-12-2019 16:57

Re: Gemini 105mc conversion Diesel to EV?
 
You already have 26 replys so this is a hot topic. Besides the links above take a look at: https://www.adventuresonboats.com/ma...ic-motors.html There are close to a hundred links on EV.
Good luck and have fun or it ain't worth doing.

Mr B 01-12-2019 17:49

Re: Gemini 105mc conversion Diesel to EV?
 
The Sonic drive has now stopped production,
They still have spares for it, But not sure how long they will last,

My Westy 30B uses 3/4 US gallons per hour,
Its a Mitsibishi engine, Buy one from a Mitsubishi dealer ( Tractor dealer) and put your existing heat exchanger on it,

Heat exchanger replaces Radiator, = Marinised,

Brewgyver 02-12-2019 13:44

Re: Gemini 105mc conversion Diesel to EV?
 
Quote:

Originally Posted by harlem24 (Post 3027241)
Sailing Uma and Rigging doctor both crossed the Atlantic and both are non-professional sailor with electric engines and very limited funding...

If you actually watch all of Rigging Doctor's videos, you'll see that they spent MANY MANY days drifting on their Atlantic crossing. Once into the doldrums, they're basically flotsam.

They spent a significant amount of time running a Honda generator attempting to recharge their bank to make some headway...

warrior 90 02-12-2019 14:38

Re: Gemini 105mc conversion Diesel to EV?
 
Quote:

Originally Posted by Mr B (Post 3027375)
The Sonic drive has now stopped production,
They still have spares for it, But not sure how long they will last,

My Westy 30B uses 3/4 US gallons per hour,
Its a Mitsibishi engine, Buy one from a Mitsubishi dealer ( Tractor dealer) and put your existing heat exchanger on it,

Heat exchanger replaces Radiator, = Marinised,

Thatīs right and go sailing in 2-3 weeks with a sweet new engine if that is all it takes.
Any decent farm garage can handle this job.
And with the saved money upgrading the boat to fair market value.
Here check it out... brand new in Germany 3500 $.
https://www.motorencenter.de/industr...-neumtor-im-at
and here factory rebuilt 3100 $
https://www.motorencenter.de/industr...ohne-pto-im-at
Canīt be much more in the USA
For that money I would not even bother to repair. Hell with the Marimafia the labour alone might cost more.
That should give him some 10-15.000 $ to play. Goes a long way on a Gemini if You know what You are doing.and donīt have two left hands.

Jeannius 03-12-2019 01:36

Re: Gemini 105mc conversion Diesel to EV?
 
Quote:

Originally Posted by warrior 90 (Post 3028077)
Thatīs right and go sailing in 2-3 weeks with a sweet new engine if that is all it takes.
Any decent farm garage can handle this job.
And with the saved money upgrading the boat to fair market value.
Here check it out... brand new in Germany 3500 $.
https://www.motorencenter.de/industr...-neumtor-im-at
and here factory rebuilt 3100 $
https://www.motorencenter.de/industr...ohne-pto-im-at
Canīt be much more in the USA
For that money I would not even bother to repair. Hell with the Marimafia the labour alone might cost more.
That should give him some 10-15.000 $ to play. Goes a long way on a Gemini if You know what You are doing.and donīt have two left hands.

Wish I'd thought of that before spending $3500 having my Northern Lights generator engine (Mitsubishi L3E) head rebuilt after poor installation caused sea water to sit in the exhaust and then corrode the valves. Especially since a year after the crank failed and I spent around $10000 on a new Westerbeke to replace it.:frown:

valhalla360 03-12-2019 01:52

Re: Gemini 105mc conversion Diesel to EV?
 
Quote:

Originally Posted by storx (Post 3026882)
Hello All,

I am curious if anyone has converted a Gemini 105 to EV yet? I am asking because yesterday I went and walked 1996 Gemini 105 that needs a bit of work, but within the price we talked about is looking to be a decent starting point. I know there are many videos of people scraping the diesel engine in favor of a gas outboard, but with my background of building electric bicycles for fun and owning a tesla model 3, the idea popped in my head of going the EV route. While looking at the boat, the owner was able to start the diesel engine, but it ran very poor and shook pretty violently and while looking at it i noticed there was a leak coming from the side of the engine block and closer inspection appears to be a hairline crack in the block of the engine near the head, so the engine is shot basically. After talking to the owner about that and a few other things i noticed, he threw out the price of 35k on the purchase and i told him i would get back with him after giving it some thought and also told him i gotta talk it over with the other half (don't have a other half at the moment, so a bit of a fib), but just wanted to buy time to think this over.

So the idea i was thinking was pulling the diesel engine, but leave the prop head and attach the electric motor to it for propulsion instead of re-inventing the wheel completely. I also looked into the company i buy my electric bike motors from and they offer a 96v 50kw max/25kw continous Motor/Controller kit for $2400, which could be combined with 4s x Tesla Model S battery modules for bare minimum battery pack for $3600.

We had a 1996 3400...switched from 40hp outboard to 25hp. Some have gone down to 15hp. In normal conditions 15hp works but we've been flat out fighting strong winds only able to make about 3kt headway with the 25hp...so would argue the 25hp is a nice sweet spot for enough HP without overkill.

In calm conditions, it doesn't take a lot of power to hit 4kts...if you want to get up to more typical cruising speeds for a gemini (6-7kts) it takes a lot more power.

They are small boats, so throwing a 1000lb of battery on the stern will push the stern down noticeably. If you just want to get out of the marina until the sails are up, this is very much viable. If you want to cruise 50 miles in 7-8hr under power...much more difficult.

valhalla360 03-12-2019 01:53

Re: Gemini 105mc conversion Diesel to EV?
 
Quote:

Originally Posted by Cadence (Post 3027161)
If the engine is bad how is the rest of the boat as it pertains to sailing?
I could be wrong but believe the drive was through a leg. I've read have problems hence the OBs.
FYI

A lot of people have converted to outboard due to the wonky stillete drive leg. That's one reason we went with an outboard version.

Tupaia 03-12-2019 02:17

Re: Gemini 105mc conversion Diesel to EV?
 
This might seem stupid and I don't know the boat but what about installing 2 x 9.9hp Yamaha high thrust outboards. Lots of much bigger cats make do with these. Installing 2 would mean they won't need to be steerable so could be installed a s far apart as possible.

valhalla360 03-12-2019 02:21

Re: Gemini 105mc conversion Diesel to EV?
 
Quote:

Originally Posted by Tupaia (Post 3028396)
This might seem stupid and I don't know the boat but what about installing 2 x 9.9hp Yamaha high thrust outboards. Lots of much bigger cats make do with these. Installing 2 would mean they won't need to be steerable so could be installed a s far apart as possible.

It's been done but the boat is already set up so the outboard/drive leg is steerable.

There's only room to get twin outboards about 6ft apart, so working them against each other isn't as effective as on wider boats. Plus once you learn to use the directional thrust by steering the outboard, it's darn near as good as twin engine designs.

Dirk01 03-12-2019 22:55

Re: Gemini 105mc conversion Diesel to EV?
 
Quote:

Originally Posted by storx (Post 3026882)
Hello All,

I am curious if anyone has converted a Gemini 105 to EV yet? I am asking because yesterday I went and walked 1996 Gemini 105 that needs a bit of work, but within the price we talked about is looking to be a decent starting point. I know there are many videos of people scraping the diesel engine in favor of a gas outboard, but with my background of building electric bicycles for fun and owning a tesla model 3, the idea popped in my head of going the EV route. While looking at the boat, the owner was able to start the diesel engine, but it ran very poor and shook pretty violently and while looking at it i noticed there was a leak coming from the side of the engine block and closer inspection appears to be a hairline crack in the block of the engine near the head, so the engine is shot basically. After talking to the owner about that and a few other things i noticed, he threw out the price of 35k on the purchase and i told him i would get back with him after giving it some thought and also told him i gotta talk it over with the other half (don't have a other half at the moment, so a bit of a fib), but just wanted to buy time to think this over.

So the idea i was thinking was pulling the diesel engine, but leave the prop head and attach the electric motor to it for propulsion instead of re-inventing the wheel completely. I also looked into the company i buy my electric bike motors from and they offer a 96v 50kw max/25kw continous Motor/Controller kit for $2400, which could be combined with 4s x Tesla Model S battery modules for bare minimum battery pack for $3600.

Take a look at fmt-kempen.de
Make it retractable.
And DON'T USE EV-batteries! They are not imanent safe and in case of a thermal runaway they not burn the boat only. Due to temperature above 1.200°C it produces hydrogen gas if it get in contact with water (and there is plenty around). That quickly solves the problem to be toasted slowly...
50 kW is much overpowered! It has more torque than 100hp Diesel!
I plan to go electric driven for a Seawind 1190 or 1260 and found out that 2x11kW + 2x400Ah@48VDC (LFP !!!) + 15kVA genny suits perfect for cruising.
Cheers
Dirk

bouncycastle 06-12-2019 10:54

Re: Gemini 105mc conversion Diesel to EV?
 
Electric power efficiency versus fuel is more to do with large losses of I/C engines .
Roughly speaking the global efficiency of I/C is about ~5%.

The screams from the roof tops are that Diesel engines are 30% efficient can already be heard the far side of the moon .

However when you put the ~ 30% power through the gearbox and then the prop shaft and then the prop the drive train losses are high so ~5% tends to global norm for many small boats
Example is gross 10 HP inboard will after all losses return 0.5 HP net power pushing the boat .

A electric 48 volt power unit using Lithium such as LiFePO4 types might return a global efficiency of ~10% or about double that of the I/C engine
There fore a ~5 HP electric solution might match a 10 HP diesel solution and return the same 0.5 HP global efficiency to the boat to push it along


The problem is power density of Diesel fuel versus battery .

Diesel fuel is about 11.6 kilowatts power per kilo which in global power to a Diesel engine makes ~0.6 kilowatts of power after losses the normal 5% global efficiency

The power density of electric power from Lithium is about 150 watts per kilo at best or ~ 1.5 % the power of the diesel fuel at best
Lead acid is worse again around 50 watts per kilo so less than 1% the power density of Diesel fuel

A example of this issue would be Narrow 4 ton 1970 era mono hull 9 metre boat with ~ 18 HP engine at ~1800 rpm and fixxed two blade prop at about 60% power in Ideal calm waters with no adverse currents would move at ~5 knot and could return ~.1.5 liter fuel used per hour or about ~ 14.5 nautical mpg UK 4.56 liters.
We could say 10 liters of fuel = 7.5 kilos = 10 hours= 150 N miles .

The rule of thumb is 0.4 liters per ton per hour

From the power density of Diesel at ~11.5 kW per kilo we can say for 7.5 kilos fuel makes ~8500 watts fuel used per hour which at ~5% efficiency makes 400 watts global power to work to push boat or about 0.5 HP or 1/2 HP to motor along

Others will say but it was a 18 HP engine so that makes ~1 bhp not 1/2 HP
At 60% gas the 18 HP engine is probably making ~8 HP which with losses will come closer to 1/2 HP

To get electric to give the same range we require 7.5 kilos to be increased a lot closer to ~40 times the weight at about ~300 kg with today's battery types . Also the battery costs go orbital per kilo compared to diesel fuel at $1 a kilo

Therefore the electric boat solution tends to be decrease the range to keep costs and weight issues down .

Extreme boats will choose to use solar panels to keep battery working longer periods of the day and use diesel generators to drive the electric engines at night but most budget cruising boats are better served with diesel only solutions .

Boat craft that always hook into the marina shore power and require short ranges to do a few hours sailing each day can more effectively utilise electric solutions .


Multi hull electric solution are more severely impacted by the the wetted hull issues than a narrow mono is
Effectivly the Cat is two narrow mono hulls .

The experimental Solar craft chose to use Trimeran solution went with one big narrow main hull and two very small outrigger hulls to keep stability and reduce wetted hull issues

Yes electric boat power solutions will one day be best cheapest lightest systems but it looks to be s good few years away if not decades away.

Bear in mind rough waters will reduce both fuel and electric power effecientcy dramatically and diesel engines effecientcy can drop a lot closer to 1%

mikedefieslife 06-12-2019 11:14

Re: Gemini 105mc conversion Diesel to EV?
 
Quote:

Originally Posted by bouncycastle (Post 3030502)
Roughly speaking the global efficiency of I/C is about ~5%.

Since the efficiency of an ICE is around 30-37% you're saying 95% of that is lost in the gearbox and final bearings?

Axel Rappe 06-12-2019 11:27

Re: Gemini 105mc conversion Diesel to EV?
 
Hi,

I am designing a tesla s powered catamaran myself and I think it is a good idea. Ideal on a cat like the gemini. I would, however, advise against going as high in voltage as you were thinking of. I intend to stick to 48v. And 2 x 10 or 15 kW machines on a 44 foot very light catamaran. I will, at times, quite possibly, be underpowered but the idea is to use the sails as my main propulsion. And honestly I think the occasions where I wish I had more power will be few and far between and probably due to poor seamanship on my part. :)

48v is a fairly simple voltage to work with. Going as high as 96 has huge advantages in some ways, but drawbacks on the equipment side. Chargers, solar panels and such become hard to find at voltages above 48. I have managed, but struggled, to find options at 48. I believe as you go higher it becomes more difficult. Not at all impossible, but give it a hard look.

I believe you can quite comfortably stick to 10kw, perhaps even less on a small and light boat like the gemini. On the other hand, an electric motor is pretty happy to run on lower power than it is designed for, so having the extra umpf when you need it might be a good idea.

I'm guessing you intend to go with 4 tesla packs. That is 21kW of power. The amp draw to occasionally power 2x50 kw peak is also something you want to think about.

Have a look at these kits:

https://www.thunderstruck-ev.com/ele...oard-motor-ev/

There are many more options out there, but this is a good way to get started.

Wish you all the best with your project! I like it.

/ Axel


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