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Tesla Sailboat

LotusFan

Member
Jun 24, 2015
13
3
Bay Area, CA
Most catamarans do not have the same hull speed limitation. Their sail power is translated into speed. Putting drag on the system by charging the batteries slows the boat, which is not usually acceptable to the cat owner in most cases -- that's part of why they own a catamaran -- speed.

BerTX, you are correct in your comments, but I would offer another perspective. Lots of multihull owners buy for stability, square footage per hull length and shallow draft rather than speed per se, (although they don't mind the speed) and I bet those owners would gladly trade an 8% speed penalty for being able to have electrical power underway without a generator running ruining all the ambiance. I love the idea of having an electric motor driven prop that can motivate or charge a battery source, thereby negating the need for constant generator running.

On a side note, no one would want a pure electric sailboat more than me, but as you correctly point out, weight is critical in multihull boats, and any weight-acceptable battery system would likely only be adequate for short distance propulsion or negating generator usage.
 

JRP3

Hyperactive Member
Aug 20, 2007
20,517
47,960
Central New York
Maybe not. A good keel should be narrow and deep, or a wing keel, which is an upside down "T", as well as very strong to survive impacts.
 

Red Sage

The Cybernetic Samurai
Jul 6, 2014
3,033
2,121
Los Angeles CA
Narrow and deep? A properly shaped battery pack, constructed of 18650 battery cells could fill such a space. Remember, the Model S battery pack is only 4" thick, and less than 8'-0" long. As I understand, most keels go further below the water than a mast pierces the sky above deck. That should allow plenty of room.
 

JRP3

Hyperactive Member
Aug 20, 2007
20,517
47,960
Central New York
No, keels are no where near as deep as a mast is tall, not even close. A 30 ft boat might have a 4-5 ft keel but a 35-40 ft mast. Also, keels need to be heavy, they are lead or steel. Using much lighter batteries means the keel would need to be even larger, which equals more drag. Plus, again I'll mention impact protection, keels hit things, like rocks. As a life long sailor I can tell you it's a bad idea.
 

BerTX

Supporting Member
Supporting Member
May 2, 2014
3,505
3,568
Texas/Washington
BerTX, you are correct in your comments, but I would offer another perspective. Lots of multihull owners buy for stability, square footage per hull length and shallow draft rather than speed per se, (although they don't mind the speed) and I bet those owners would gladly trade an 8% speed penalty for being able to have electrical power underway without a generator running ruining all the ambiance. I love the idea of having an electric motor driven prop that can motivate or charge a battery source, thereby negating the need for constant generator running.

On a side note, no one would want a pure electric sailboat more than me, but as you correctly point out, weight is critical in multihull boats, and any weight-acceptable battery system would likely only be adequate for short distance propulsion or negating generator usage.

Thanks for expanding on this. My next paragraph, which you did not quote, says: "Sure, there are times when a cruising cat would not mind charging while underway."

If I were to own another cruising cat, I'd definitely try to do electric propulsion. There are some benefits of fuel propulsion, like using waste heat to heat water. I have toyed with the idea of having a "hybrid" system of sorts, with one engine being diesel and the other electric. in many cases, only one hull's power source is enough to drive the boat. One could still use both when maneuvering, or electric when sufficient charge is available and diesel when it is not. Still doesn't get rid of the stink, though...
 

TheTalkingMule

Distributed Energy Enthusiast
Oct 20, 2012
7,214
27,574
Philadelphia, PA
I have toyed with the idea of having a "hybrid" system of sorts, with one engine being diesel and the other electric. in many cases, only one hull's power source is enough to drive the boat. One could still use both when maneuvering, or electric when sufficient charge is available and diesel when it is not. Still doesn't get rid of the stink, though...
Why not just have the diesel component be a backup generator that charges the propulsion batteries in the rare instance it's needed? I have to think that with the combination of floating thin film solar and regenerative prop charging you'd almost never run out of charge.
 

snort

Member
Jun 27, 2015
164
74
Seattle, WA
..they are displacement boats, meaning that the speed of the boat is limited by factors of the hull that will not allow it to go any faster, no matter how much power (sail) is applied. When this limit is reached, the excess power can be used to charge the batteries without sacrificing performance of the boat.

Most catamarans do not have the same hull speed limitation. Their sail power is translated into speed. Putting drag on the system by charging the batteries slows the boat, which is not usually acceptable to the cat owner in most cases -- that's part of why they own a catamaran -- speed....

Close, no cigar. Displacement hulls are sort of limited by their wavemaking properties. The so called "Hull Speed" of any object in water is the speed at which its bow wave becomes long enough that to go any faster would involve lifting the whole object onto its bow wave. This effect is called "Hydroplaning" or just "Planing". The size and shape of the bow wave are affected by speed and also by the shape of the part of the boat that's in the water. For a wide class of normal boat-like hulls, this is pretty close to H = 1.34 * sqrt(LWL), where LWL is the waterline length measured in feet, and H is Hull speed, measured in knots. so a "normal" boat with a 25 foot waterline has a hull speed of 6.7 Knots or about 7.7 mph.

Planing boats are designed to be light and plane easily. This means they have high power to weight ratio, and hull shapes that are good at supporting the boat and keeping it stable while planing. There are plenty of sailboats that plane. I raced 505s for many years, for example...they're all about planing.

monohulls get their stability from hull shape and positioning of weight--either in a keel, or the positioning buoyancy outboard. there are limits to this, which put limits to the amount of power you can apply.

catamarans get their stability by moving buoyancy way outboard, with a second hull. this is much more effective than a monohull, so they can hang a lot more sail area for a given size and weight. This artificially high stability also means a very narrow hull shape is possible. There are more hulls, but they individually produce a lot less drag and make a much shorter wave. They have a hull speed too, but it's more like 3 * sqrt(LWL) (so a 25 foot cat doesn't start to plane until it's going over 15 knots)

big ships have very long waterlines. sqrt(500) * 1.34 = 29 kts or 35mph. that's faster than they want to go anyway.

--Snortybartfast
 

Red Sage

The Cybernetic Samurai
Jul 6, 2014
3,033
2,121
Los Angeles CA
OK. Just checking. I thought I remembered seeing a rendering for an America's Cup keel that would have had similar proportions to what I spoke of... But that was ages ago, I was probably in Junior High School. Come to think of it, I may be confusing that with some of the spacecraft designs from Star Wars movies...
 

MassModel3

Member
Aug 19, 2014
907
254
MA South Shore
I have been an early adopter in this area also, taking delivery of my custom-configured electric Alerion Express 33 sailboat just two months after our Tesla Roadster, in July of 2010. I now have 1,000's of nautical miles on the boat, including quite a lot of silent motoring miles when the wind was just not there. Like terrestrial EV's, I would not own anther ICE boat again. A sailboat is meant to be nearly silent, and when the wind is not available, the stink and rattle of a diesel power train is just so 20th century.

The power train is sourced from MasterVolt, and has a 7.5 kW AC motor, and 19 kWh of LiFePO4 batteries. While I originally had a feathering prop fitted to the boat to enable regen, it never worked very well, due to suboptimal motor controller firmware, which MasterVolt had promised to improve, but never did. So recently, I switched to a folding prop, because I race, and wanted the lowest sailing drag possible. To my surprise and delight, the folding prop's drive efficiency is so much higher (15+%) than the feathering prop, that I now have more effective range (30-40 nm) than before, plus being faster under sail in light wind.

Here are a couple photos of my water-borne EV:

- - - Updated - - -

Oh, I forgot to mention that last fall I also added 100W of low-profile solar panels, directly bedded into the stern decks. They do not contribute to the propulsion, but power all the onboard electronics.
Wow... Just wow!
 

electricboat

Member
Apr 28, 2019
55
8
Hong Kong
If you guys are still interested. I am thinking of doing a start up for putting Tesla motor(s) on a like 15m flybridge cruiser with around 7-10 sets of battery hoping to give it a range of 200km to 250km range.

At first I am thinking of converting a existing boat with diesel engine to keep the cost low and then later on start building brand new boat with motor and battery in it..

If you are interested please PM with your contact detail. I am based in Hong Kong..
 
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tander

Active Member
Jul 23, 2012
1,512
1,502
I don't think this is feasable at all unless you are talking about small sailing vessles staying in costal waters. Don't underestimate the amount of power it costs to have Radar, fridge, freezer, computers, heating, washing machine, pumps, long range radios/phones for internet etc running (and warming water if you dont have a gas boiler). Yes you can connect an alternator to the propeller but that will generate only about 200 watts at decent sailing speed from my own experience (+some extra kw you get from solar and wind power). And in an emergency you need to have enough power to have bilge pumps constantly running. A good diesel engine is extremly reliable and there is a reason crusing yachts carry much more fuel than they really need.
Oil is pretty amazing stuff, hard to best it. A while back I ran the numbers on what it would take to do a solar/electric/wind container ship and was surprised that it's already pretty much feasible if there was not a battery shortage, but nobody had put them all together yet, kind of like Tesla ten-ish years ago. Same principles apply to big ships as cars, and like cars, it eventually just makes more sense in pretty much every way. Interesting thing is instead of charging, the cargo ships may end up going back to sails
, and ironically there may come a point in 10? years when cargo ships still carry oil, but don't run on it.
 

tander

Active Member
Jul 23, 2012
1,512
1,502
I don't think this is feasable at all unless you are talking about small sailing vessles staying in costal waters. Don't underestimate the amount of power it costs to have Radar, fridge, freezer, computers, heating, washing machine, pumps, long range radios/phones for internet etc running (and warming water if you dont have a gas boiler). Yes you can connect an alternator to the propeller but that will generate only about 200 watts at decent sailing speed from my own experience (+some extra kw you get from solar and wind power). And in an emergency you need to have enough power to have bilge pumps constantly running. A good diesel engine is extremly reliable and there is a reason crusing yachts carry much more fuel than they really need.
Oil is pretty amazing stuff, hard to best it. A while back I ran the numbers on what it would take to do a solar/electric/wind container ship and was surprised that it's already pretty much feasible if there was not a battery shortage, but nobody had put them all together yet, kind of like Tesla ten-ish years ago. Same principles apply to big ships as cars, and like cars, it eventually just makes more sense in pretty much every way. Interesting thing is instead of charging, the cargo ships may end up going back to sails
, and ironically there may come a point in 10? years when cargo ships still carry oil, but don't run on it.
 

tander

Active Member
Jul 23, 2012
1,512
1,502
I don't think this is feasable at all unless you are talking about small sailing vessles staying in costal waters. Don't underestimate the amount of power it costs to have Radar, fridge, freezer, computers, heating, washing machine, pumps, long range radios/phones for internet etc running (and warming water if you dont have a gas boiler). Yes you can connect an alternator to the propeller but that will generate only about 200 watts at decent sailing speed from my own experience (+some extra kw you get from solar and wind power). And in an emergency you need to have enough power to have bilge pumps constantly running. A good diesel engine is extremly reliable and there is a reason crusing yachts carry much more fuel than they really need.
Oil is pretty amazing stuff, hard to best it. A while back I ran the numbers on what it would take to do a solar/electric/wind container ship and was surprised that it's already pretty much feasible if there was not a battery shortage, but nobody had put them all together yet, kind of like Tesla ten-ish years ago. Same principles apply to big ships as cars, and like cars, it eventually just makes more sense in pretty much every way. Interesting thing is instead of charging, the cargo ships may end up going back to sails
, and ironically there may come a point in 10? years when cargo ships still carry oil, but don't run on it.
 

snort

Member
Jun 27, 2015
164
74
Seattle, WA
Many ships built in the last decade or two have been diesel electric. For example, recent passenger liners use a device called an Azipod, which is an electric motor and propeller in a pod that hangs below the hull, and can be turned in any direction to go forwards, backwards, steer, go sideways, etc. There's a group of diesel engines running generators to power this and everything else in the ship. Tug boats and many others, such as Ferrys, do this or something similar. There was an experiment in Europe where they used batteries instead of the diesel. It worked, but was expensive. It would be most practical for a situation like a municipal ferry, where the ship spends over half its cycle at the dock being loaded and unloaded where it could be charged with the ferry version of a supercharger, with a relatively short trip. There's no opportunity for regenerative braking on a boat.

Solar power is at best a trickle charger on a ship, it's nowhere near enough to move it at anything like a reasonable speed.

Wind, on the other hand, has some potential, although from experiments so far it looks like it's more likely to be something that will save a few percent on fuel economy rather than a major source of propulsion.

-Snortybartfast
 

ZoomsansVroom

Supporting Member
Supporting Member
May 3, 2019
184
68
29577
Interesting concept in the sails. I'm a bit confused on the design being considered so efficient, though. (It might be much simpler to add to a cargo ship. It seems like if it was more efficient, the high-speed ocean racers would have switched.)

The man in the youtube video was a bit of a goof - whining that folks won't switch over to a much more expensive process, in a very cost-competitive industry, is a bit odd.

The electric ferry idea is interesting.
 

Ludus

Member
May 1, 2013
367
126
Michigan
A8BA4F3E-0E1E-49B8-84DE-628BF16C0B8D.jpeg
Black Pearl (yacht) - Wikipedia


This yacht is almost there. Still has Diesel engine though. Bigger battery packs and the next iteration could be all electric. It does have PV on it’s black sails and generates power from its props when under sail.

It’s a bigger, newer variant of the sail system on Maltese Falcon.
 

ZoomsansVroom

Supporting Member
Supporting Member
May 3, 2019
184
68
29577
Its nifty, but at a certain point, a square rig of that size really needs the ability to deliver a broadside, and holes in the deck for the peg-legged to stomp around on it. (Hell, I'd love to have it, if I had a hundred billion or so to throw away - just seems like its the kind of thing for "Sailing the Spanish Main.")
 

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