Optimal hull and keel shape for electric propulsion

[argosail]

Originally Posted by Pete7

I think he means Delphia Boats, but yes 10Kw is about 13Hp although they are not directly compatible and you won't be motoring fast with an electric yacht conversion in an existing hull. A Macgregor 26x might be interesting

Pete

I spoke with a rep of a Polish boat company at the boat show">Annapolis boat show, they said they can do an electric version of any of their size boats. The company was VIKO I believe, are there a lot of Polish makers out there or just different names under one group??

[Pete7]

Originally Posted by argosail

are there a lot of Polish makers out there or just different names under one group??

Erm yes

A lot of older boat moulds were moved to Poland, and launched as new boats because the labour rates are much lower than the rest of Europe and they have a good work ethic. The problem can be quality, but that also applies to other manufacturers too.

If you look at power wall or server rack 48v LifePO4s, they are going to weight in at 50kgs (110 lbs) for 5Kw of power. So 10Kw ought to be doable for a similar weight to your diesel engine.

[Rumrace]

Contrary to all the nay sayers electric boats go like stink and range is increasing everyday. Like I suggested check out the pro builders not the yacht clubs backyard mechanic with a slide rule. My Tesla is coming up on its 5th year no worries
Rand boats went from a go fund me to being acquired and financed. They have a 28’.
The same negative folks will tell you Hydrogen is not a fuel. Toyota is producing liquid hydrogen on a Tri hull. Yanmar has a 3 cylinder hydrogen Yamaha Toyota have a 400hp marine V8 hydrogen and Yanmar Toyota have a straight 6 Hydrogen in a 28’ hardtop. The entire Japanese automotive and marine industry are working together on new hydrogen zero emission drives.
Delhi boats claim they will have zero emissions 2023. They make big yachts and people are going to pay 1.6M for them. They probably won’t read the maths which tell them 7 minutes. What suckers huh.

[Pete7]

Originally Posted by Rumrace

Contrary to all the nay sayers electric boats go like stink and range is increasing everyday.

Hang on, the OP (and others) wants to convert an existing 30ft sized yacht, not spend serious cash on a speed boat. Subtle difference.

Pete

[Rumrace]

Do you remember that old joke where one lost fella asks an old man at a gas station how to get to Chesterton. The old man ponders for a minute and says “ you can’t get there from here”

Cigarette must be the dumbest boat maker on the planet and I’m special stupid cause I’m a huge naive fan.
Sold out! All electric very very fast Cigarette. Wee fit two in their new yacht

[boatpoker]

Originally Posted by Rumrace

Do you remember that old joke where one lost fella asks an old man at a gas station how to get to Chesterton. The old man ponders for a minute and says “ you can’t get there from here”

Cigarette must be the dumbest boat maker on the planet and I’m special stupid cause I’m a huge naive fan.
Sold out! All electric very very fast Cigarette. Wee fit two in their new yacht

When will they actually produce one for sale ?

[Adelie]

Originally Posted by argosail

Thanks for the info! I see typical house/starter batteries are 12V and if you run 4 of them in series then that should power the 48v electric motor, and if there is space add some more?

OK, time to discuss battery categories.

There are 2 major battery chemistries: Lead Acid and Lithium Ion.

Lithium ion has multiple sub chemistries. The only one you want on your boat is Lithium Iron Phosphate, LiFePo or LFP. The other sub-chemistries have various advantages and disadvantages compared to LFP, the key disadvantages are
A. LFP has better cycle life, like twice the life.
B. Greatly reduced risk of thermal runaway, i.e. won't spontaneously catch fire and burn your boat to the waterline with you in it.


Lead Acid (LA) has 5 construction types:
Flooded Lead Acid (FLA) which is what most vehicle batteries are. They require checking fluid levels approximately every 3 months.
Gel - which uses a thickening agent in the liquid acid to make it a gel. Generally there is price premium for gels. Run of the mill gels will have very good cycle life for an LA battery. They are touchy about charging voltage. No maintenance needed or possible.
Absorbed Glass Mat (AGM). The acid electrolyte is absorbed in a fiberglass layer between electrodes in the battery. Capable of relatively high discharge rates. Require relatively high recharge rates or cycle life with suffer. Need to be fully recharged most days. If the battery is regularly operated in Partial State of Charge (PSoC) cycle life will suffer significantly.
Carbon Foam, (AGM-CF, Firefly) - A variant of AGM this is much more tolerant of PSoC operation and has a significantly higher expected cycle life as long as the high rate of recharge can be met.
Carbon-FLA - A variant of FLAs that seems to have much higher cycle life.

Lead Acid also has 3 or 4 use types which is really a category of construction type but it's easier to discuss in terms of use.
Starting - These have many thin plates that will provide very high amperage output. If they are discharged very deeply capacity and cycle life suffer.
Hybrid/Marine - A battery that has somewhat thicker plates that can be discharged more deeply without compromising cycle life and still has pretty good amperage for starting. 2 of these should be able to start a large engine and provide house power overnight. These are good for motor vessels where the engine is run daily or almost daily.
Deep-Cycle/Golf Cart - Relatively thick plates, generally good to be discharged to 50%, if there are 3-5 of them in a bank, should be able to start a large engine.
Railroad, Telephone, Solar - Very thick plates, very good cycle life, generally can be discharged below 50%.

For a house bank you want deep-cycle or solar batteries. Keep in mind that a lot of so called Deep-cycle batteries are really hybrid batteries or starting batteries with a deep-cycle sticker plastered on them. Getting golf-cart FLAs is a good way to make sure you are getting real deep-cycles.

For plug-n-play batteries Golfcart FLAs provide the best bang for the buck. AGMs cost more up front and don't last as long. If you have restricted access to the battery that prevents checking water or you know that you will not be good about checking water, then get GELs, similar price to AGM but last a lot longer. Or get LFP.

DIY LFPs are actually cheaper over the long term, but involve learning how to build your own.
Since LFP is in the process of coming off all the important patents this year, prices should come down more for both DIY and Plug-n-Play versions.

You asked about making 48v by using 4-12v batteries in a string, that is correct. Or 8-6v batteries. The string will have the same Ahr capacity as any single battery in the string. To get more Amp-hr you need to add more strings of 4 or 8 batteries.

Do not mix Lead acid battery types, uses and/or capacities, electrical weirdness will happen and it will generally cost you money even if nothing dangerous happens. There is ongoing discussion about mixing Deep-cycle LA and LFP. I'm waiting on more history for this before I have an opinion. As a newbie, don't go there, wait for the kinks to get ironed out.

[Jim Cate]

^^^^

Good summary, so OP, pay attention to the above!

Jim

[Don C L]

Back to boats for a second: Hobie 33.

[Adelie]

Originally Posted by Don C L

Back to boats for a second: Hobie 33.

Alas Hobie 33's use outboards. The motor the OP discussed at the boat show is a replacement for an inboard.

The H33 is a 4000lb boat so it would take significantly less power to propel than the 7k-9k boats the OP mentioned. https://sailboatdata.com/sailboat/hobie-33

Another option would be a C&C Mega-30 which again uses an outboard.
https://sailboatdata.com/sailboat/mega-30-od-cc

Both of these boats are very light weight meaning less power is needed to propel them to the same speed but they are also weight sensitive which would mean that LFP batteries would be required and you still wouldn't be able to carry as many as a heavier displacement sailboat so range and speed would probably be a wash.

There are electric outboards that could be used but the tradeoff is that they use small propellers which sacrifice efficiency. Given that electric motors are involved it would not be unreasonable to vastly increase the diameter (1.5x-2.0x) of the prop and pitch it up a little to increase efficiency. The motor would not be running at optimum and load and RPM and may die an early death. Hard to tell.

[Rumrace]

“According to Watercraft Journal, the E-Jet will include multiple powertrains, including the choice between a forced-induction gas-powered engine or a full electric motor. In typical Cigarette fashion, performance reigns supreme with the gas-powered engine generating a top speed of 75 mph, and the electric option generating a comparable 64 mph. It should be noted that U.S. Coast Guard regulations currently stipulate that PWC manufacturers should not build craft that exceed 65 mph, and Canadian manufacturers follow suit. The electric motor is expected to have a runtime of about 2 hours and can recharge with 30 minutes of runtime after just 2 minutes of charging“ Boat Blurb

Yup the power boaters are doing it. These idiot manufactures architects and engineers should have consulted the doctors lawyers dentists insurance salesmen backyard mechanics at the local sailing club instead of wasting all their time.

[valhalla360]

Originally Posted by Pete7

I think he means Delphia Boats, but yes 10Kw is about 13Hp although they are not directly compatible and you won't be motoring fast with an electric yacht conversion in an existing hull. A Macgregor 26x might be interesting

Pete

If you want to plane a Macgregor, they usually do it with a 50hp outboard. Maybe if you strip the interior completely out and remove the rig 10kw, might get on plane but I doubt it.

Just about any traditional keel boat will be pretty efficient at low speed. Just really low speed if you want more than a few miles range.

[argosail]

Originally Posted by Adelie

Alas Hobie 33's use outboards. The motor the OP discussed at the boat show is a replacement for an inboard.

The H33 is a 4000lb boat so it would take significantly less power to propel than the 7k-9k boats the OP mentioned. https://sailboatdata.com/sailboat/hobie-33

Another option would be a C&C Mega-30 which again uses an outboard.
https://sailboatdata.com/sailboat/mega-30-od-cc

Both of these boats are very light weight meaning less power is needed to propel them to the same speed but they are also weight sensitive which would mean that LFP batteries would be required and you still wouldn't be able to carry as many as a heavier displacement sailboat so range and speed would probably be a wash.

There are electric outboards that could be used but the tradeoff is that they use small propellers which sacrifice efficiency. Given that electric motors are involved it would not be unreasonable to vastly increase the diameter (1.5x-2.0x) of the prop and pitch it up a little to increase efficiency. The motor would not be running at optimum and load and RPM and may die an early death. Hard to tell.

Well I did see an awesome outboard electric provider at the show called "electric paddle" but of course they're all out of stock... I haven't look at Hobie, maybe worth an idea but being so light I wonder if it would be an OK ride from Philadelphia down to the Caribs. I like an exciting ride and weather helm doesn't both me much but sailboatdata says they are really really uncomfortable if one believes their ratios (which I know are not always based in reality). The headroom is 44 inches which I can't imagine is fun long-term. I've been cooped up in tugboats a few time but it was never fun.

[Rumrace]

I saw a McGregor on plane. Wow
It’s a water ballast boat ?
Wouldn’t a centre board with a nice brow or swing keel be best?
The optimal hull for power doesn’t include many Sailboats if any.

[argosail]

Yes they're water ballast and from what I read you adjust the ballast for planing.