Converting a 97-ton steel ketch to electric propulsion

[Capt. Ray]

International Rescue Group's flagship is a 78-foot LOD (length on deck), 75-foot LWL (waterline length) ketch at 97 tons full displacement vessel. We are hauling her out in Rio Dulce, Guatemala in a month and wish to take out her old Volvo 450HP diesel (always stupidly overpowered!) and replace with an electric or diesel-electric hybrid system.

We are a charity run by 100% unpaid volunteers so we don't have much money, but some donations have been earmarked for a refit. Cost is a major factor, but we do have an IRG T-shirt, IRG cap and lots of public kudos for the design winner, WHOO-HOO!

Feel free to discuss here but please submit your ideas on our design web page (link below). PLEASE keep contentious debate of electric, hybrid or direct drive to the other topics, this decision is already made - we're looking for the best ideas on how to achieve the project.

Here are the design specifications and objectives:

1. In light air we have determined using hip-towing and outboard motors (small propellers) that 20HP thrust moves the vessel at 1.8kt and with 50HP thrust at 3.5kt which is 84nm per day and quite satisfactory for a blue-water sailboat. In experimenting we find that 20HP is enough to motor-sail in light air.
2. In another experiment, in light air we reached 3kt being towed by another 40-foot sailboat with a single 35HP diesel engine at less than full power. Our guess is that if that 35HP was driving our boat alone we would reach 4kt and possibly more.
3. When power is applied through the single propeller shaft rather than inefficient vectored hip-towing using small propellers, we expect better speed than in the above experiments.
4. As a charity we do not expend fuel while there is wind. If we cannot make VMG progress due to adverse wind direction we heave-to rather than burning fuel.
5. We apply sound seamanship to avoid lee shore or adverse current situations rather than apply power and burn fuel.
6. Power propulsion is generally only required when maneuvering into ports or anchorages, motor-sailing or when on mission making way in light or no wind conditions.
7. When we remove the Volvo engine and transmission it will open up a 7-foot stand-up almost rectangular engine room of 12 feet wide by 8 feet long and a very deep bilge in the center 4 feet deep by 3 feet wide, 6 feet long which could house a large battery bank keeping weight low.
8. We have two 240v Northern Lights diesel generators, one is 16kW and the other is 20kW. We require at least one generator to drive large watermakers for disaster relief missions.
9. The vessel has a large cockpit over which we can install a 2kW solar panel farm. This could be possibly extended to 4kW.

DESIGN COMPETITION - converting 97-ton sailboat to electric propulsion - International Rescue Group

[atoll]

steam engine fed by woodchips from drift wood collected by volunteers that need plenty of exercise beach combing..........

[Capt. Ray]

And... the first reply has nothing to do with electric propulsion!

Originally Posted by atoll

steam engine fed by woodchips from drift wood collected by volunteers that need plenty of exercise beach combing..........

[Fiveslide]

Atoll is a funny fellow. Alas, sometimes his jokes miss the mark. I'm certain he would love to see someone succeed with electric propulsion of this size. A lot of us would.

Good luck, Ray.

[roland stockham]

Have you looked at the type of pod drives used in tugs. A stearable pod sound ideal for your purpose. Never looked at the detail as this is outside my scale of experience. The other issue you may want to look at if you have not already done so is regulation. I am presuming you come under commercial shipping rules and expect there are regulations regarding min auxillary propulsion requirements.

[Capt. Ray]

I think you're referring to Azimuth thruster drives, an interesting idea becoming more popular with large commercial shipping though at an initial search very expensive, compared with a simple AC electric motor running off our generators... we are just a small charity with limited funds for this refit. In a small way, Torqueedos are electric azimuth pods!

We do not fit under commercial shipping rules so the regs we work to are frankly leisure boating.

Originally Posted by roland stockham

Have you looked at the type of pod drives used in tugs. A stearable pod sound ideal for your purpose. Never looked at the detail as this is outside my scale of experience. The other issue you may want to look at if you have not already done so is regulation. I am presuming you come under commercial shipping rules and expect there are regulations regarding min auxillary propulsion requirements.

[jmorrison146]

Don't forget total weight differences and how it will affect stability.

[Oceandeep]

Hi Captain Ray
Have you looked at examples of diesel electric propulsion systems that the Navy has developed? Maybe their are some design ideas you could repurpose or even find some Navy surplus systems that you could use
Best regards!

[roland stockham]

Originally Posted by Capt. Ray

I think you're referring to Azimuth thruster drives, an interesting idea becoming more popular with large commercial shipping though at an initial search very expensive, compared with a simple AC electric motor running off our generators... we are just a small charity with limited funds for this refit. In a small way, Torqueedos are electric azimuth pods!

We do not fit under commercial shipping rules so the regs we work to are frankly leisure boating.

Not seen anything fron Torqueedos at that size but have you seen these https://www.fischerpanda.de/azimutin...on-systems.htm

[Cadence]

Originally Posted by Capt. Ray

International Rescue Group's flagship is a 78-foot LOD (length on deck), 75-foot LWL (waterline length) ketch at 97 tons full displacement vessel. We are hauling her out in Rio Dulce, Guatemala in a month and wish to take out her old Volvo 450HP diesel (always stupidly overpowered!) and replace with an electric or diesel-electric hybrid system.

We are a charity run by 100% unpaid volunteers so we don't have much money, but some donations have been earmarked for a refit. Cost is a major factor, but we do have an IRG T-shirt, IRG cap and lots of public kudos for the design winner, WHOO-HOO!

Feel free to discuss here but please submit your ideas on our design web page (link below). PLEASE keep contentious debate of electric, hybrid or direct drive to the other topics, this decision is already made - we're looking for the best ideas on how to achieve the project.

Here are the design specifications and objectives:

1. In light air we have determined using hip-towing and outboard motors (small propellers) that 20HP thrust moves the vessel at 1.8kt and with 50HP thrust at 3.5kt which is 84nm per day and quite satisfactory for a blue-water sailboat. In experimenting we find that 20HP is enough to motor-sail in light air.
2. In another experiment, in light air we reached 3kt being towed by another 40-foot sailboat with a single 35HP diesel engine at less than full power. Our guess is that if that 35HP was driving our boat alone we would reach 4kt and possibly more.
3. When power is applied through the single propeller shaft rather than inefficient vectored hip-towing using small propellers, we expect better speed than in the above experiments.
4. As a charity we do not expend fuel while there is wind. If we cannot make VMG progress due to adverse wind direction we heave-to rather than burning fuel.
5. We apply sound seamanship to avoid lee shore or adverse current situations rather than apply power and burn fuel.
6. Power propulsion is generally only required when maneuvering into ports or anchorages, motor-sailing or when on mission making way in light or no wind conditions.
7. When we remove the Volvo engine and transmission it will open up a 7-foot stand-up almost rectangular engine room of 12 feet wide by 8 feet long and a very deep bilge in the center 4 feet deep by 3 feet wide, 6 feet long which could house a large battery bank keeping weight low.
8. We have two 240v Northern Lights diesel generators, one is 16kW and the other is 20kW. We require at least one generator to drive large watermakers for disaster relief missions.
9. The vessel has a large cockpit over which we can install a 2kW solar panel farm. This could be possibly extended to 4kW.

DESIGN COMPETITION - converting 97-ton sailboat to electric propulsion - International Rescue Group

AC or DC generators? If DC, diesel electric makes sense if AC replace the propulsion diesel with a small one.

[billknny]

Your design specifications are incomplete, and more information is needed.

You want electric propulsion to do two things:

Enter a port or anchorage,

AND

To make way toward your destination when "on mission in light or no wind conditions".

Those are fine, but the following bits need to be added to your design brief, because they are vital to any design. Anyone who can not address these questions is not technically capable of designing your dream boat.

Under what conditions do you wish to be able to "enter port"? In no wind you could do it with a 10 HP outboard clamped on your stern, in 40 knots you'd need something very different. SOOOO... What wind strength do you need to be able to make way into?

That question tells the designers what maximum thrust they need to design for.

When you are "on mission" and you wish to "make way" toward a destination in light wind you need to answer two questions: How fast? and for how long?

The thrust needed for Problem #2 is much lower than for Problem #1. But it does tell the designer what kind of endurance you need to have.

Finally, do you have a "model boat"? One your design team have looked at and said "One of those, Please!" If not, be aware that you are building something completely new and different and there will be many risks.

[atoll]

Originally Posted by Capt. Ray

And... the first reply has nothing to do with electric propulsion!

steam engine fed by wood chips running a gas turbine,turning an a/c or dc generator,charging batteries and direct supply to electric propulsion when motoring,ticks all the boxes,as long as you have a ready supply of wood collectors

steam condenser for making large amounts of fresh water from salt water for disaster relief

[hpeer]

Ray,

I’m a bit confused. You have a 20kw (26hp) diesel generator and a 16kw (23hp) generator and you need a fairly large generator for water making. And you are near broke.

It sounds simple to me, install a large battery bank and a 40ish HP drive motor. The gens can charge the batteries and the batteries drive the motor.

Keeping it simple either gen drives the charger to charge the batteries and batteries drive the motor. You then run up to 26hp to the shaft so depleting batteries. If you run over 26 hp you deplete batteries. Bigger the bank longer you can run at high HP. Presumably you only need high HP for short duration anyway.

When you get more cash you can install more batteries and/or add more solar. Maybe upgrade you ground tackle?

I think you pretty much have the info you need.

[roverhi]

a 75' boat and electric/diesel propulsion and little money don't go together. The conversion will cost a bundle and, without the proper design, be a very very poor replacement for straight diesel power. Think we have eco idiot thinking overwhelming the practical. Best solution, if this is a war on Carbon, is use the sails exclusively. If you have to get into a harbor with no wind, have a dinghy with a big enough motor to tow or push the boat in. As someone up the line said, you could maneuver in light wind conditions with a surprizingly small boat/outboard. Don't use the dinghy motor for getting around when anchored. Get the oars out.

Is the diesel busted beyond repair?? Will be way cheaper to replace the huge diesel with something a 1/4 that hp if you want to be truly eco responsible.

Atolls solution makes as much sense as a diesel electric set up. Converting diesel fuel into elctrons to power an electric motor is not conservation responsible. A smaller direct drive diesel will be more energy efficient. Yes, I know they power trains with hybrids but they do it for the instant torque of the electric motors and no gearbox.

[billknny]

We have "run into" this boat before....

And one more thing...