Hybrid sailing trimaran with electric outboard and regenerative capability

Hello all,

I own a f 27 corsair racer cruiser trimaran. The boat is lightweight, incredibly fast under sail( capable of 20kts) and will do 7kts under motor with an 9.8 tohatsu outboard.

I have been intrigued with regenerative electric drives since reading about Solomon technologies electric wheel.

I plan to build an electric outboard with regenerative capability under sail. I feel a performance trimaran like mine could be incredibly comfortable with a strong supply of electricity while under sail and won't miss a kt or speed the way a monohull might.

I have been told I need to use an ac motor to gain regenerative capability
And have the following questions.

What size motor would give me comparable or better performance than my 9.8 tohatsu?

What rpm range would make sense for such motor to be efficient ?
What propellor size would be the best for efficency both in propulsion and regeneration?

I intend to run a small battery bank powered by optima blue top and backed up by a small generator and a small solar panel

What challenges might we encounter with such a project and how should we handle them?

 

You can replace the Tohatsu with a Torquedo electric outboard and have very good performance by going electric propulsion. You can keep the batteries topped with solar cells and a small generator. Westerbeke makes a real (as in installed instead of portable) marine gas genset @ 3Kw that weighs 170 lbs and with a good soundshield and muffler you would never know it was running.

http://www.torqeedo.com/us/hn/home.html

http://www.westerbeke.com/Products/productdetailLanding.aspx?id=1194

I don't think regenerating power will be effective for coastal cruising. You have to go so fast for so long for water power to generate enough energy for it to be:

1 effective
2 cost effective

I raced F27's in Bisacyne Bay many years ago, great boats. Biscayne Bay was the perfect venue for racing them.

Steve

 

I understand the benefits and limitations of electric propulsion. My last boat was an 18 ft trimaran that I equipped with an electric trolling motor and a gel cel battery. It was quiet and provided all the power I needed to get clear of the dock and raise the sails.

I'm really interested in developing a working regenerative system to keep the batteries topped off while cruising. We sailed the boat from Ponce Inlet to St Augustine( 60 miles) over Memorial day and between running the auto pilot and making frozen boat drinks we ran the battery dead. (9 hours sailing)

I have since replaced the single battery with two blue top optima gel cells and I am working on a new solar panel and generator. I beleive with the massive power provided by the F 27's rig that a water based generator would make sense. If I have to build a separate generator I wil but I figure I can save weight and space with a hybrid propulsion / generator.

The F 27 won't care about a little drag. Losing a knot means a lot to a monohull doing 5 knots but less to a racing tri doing 10. Making an outboard using the tilt up mount means I can pull it out of the water to race anyway.



I miss the silence of my old boat

 

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I'd be interested in hearing how you work this out-I love the concept but don't know much about the electrical technology. Good Luck-and keep us abreast of developments.

 

http://www.christieengineering.com.au/PBCgallery.asp

These are good little battery chargers.... I think ideal for topping up AGM's quickly and using about half a cup of fuel.

 

The torquedo is not a trolling motor, it real electric propulsion for a boat like the F27 and by far the best I have ever seen. It would move you almost as fast as the Tohatsu and with more thrust.

http://www.torqeedo.com/?id=271&L=2

There are several ways to do water generation. There is a new product I've seen introduced in the marine trades but I can't find the piece. It looks like a small outboard motor with a funny prop and the intro picture showed two mounted on what looked like an open 60. The claims were pretty good even in the lower speed ranges.

Something else to look at might be a towed water generator. These are units that tow a propeller on a line like an old fashioned log and the line connects to a generator typically mounted to the pushpit. These have been used by cruisers forever and the technology is pretty good, the units deploy and stow easily, are small and reliable. Problems are with weed fouling and sharks eating the spinners.

You haven't mentioned wind power yet. Some love them, some hate them, but you can't have an "off the grid" conversation without adding a chapter on wind which would charge underway and at anchor.

I have not seen a motor/generator unit sized appropriately for an F27, especially one that mounts like an OB which is what in my opinion would be the best style for an F27, but there are a variety of good and proven units in electric propulsion, water, wind, solar and genset power that are off the shelf that could get you there quickly and easily.

Steve

 

keysdisease has it correct... I was keen on a pair of Torqeedo R4000 for my boat but charging and batteries caused me to defer for the present - several boats have since gone Torqeedo - contact the Australian distributor Claude Desjadins for more information on the local installations... You should use the supplied LiFePO4 batteries from Torqeedo too as they are light and should be kept near each engine as they use PCM control and that does not like long power lead runs...

If you just use the Torqeedo's to get into port, then solar panels may suffice - else get a small 3hp Honda 4 stroke petrol to drive a 48v battery charger for emergencies... (that will give you about 1800W maximum for about a third power)... The Torqeedo R2000 is a 24V system and 1800W is close to maximum, (2000w), for that engine... The difference between diesel/Petrol and Electric is that electric can deliver maximum torque from "zero rpm"...

http://www.christieengineering.com.au/Products.asp?PCat=Petrol battery chargers 24V 45AMP BATTERY CHARGER $1485.00 AUD inc GST Freight not included
This 24V model is best suited for larger charging requirements, such as the marine industry, backup for solar powered sites, motor-homes, earthmoving ... Not really cheap, but good for the R2000 but delivers 1000W - about half power if the battery was flat...

http://www.christieengineering.com.au/Itemdetail.asp?PC=GX16024V80A will give 2044W continuous or half power for twin engines? or allow near full power for an hour or so...

 

I am aware of the capabilities of the torqueedo and some of the towed generator options. I had looked at a dual water/ wind generator called DuoGen, I really liked everything but the $4200 price tag

I was hoping to find some expertise in electric motor tech to assemble what doesn't seem to already exist. A combination electric propulsion unit that doubles as a water based generator when under sail.I want to assemble it in an outboard style format.

Thanks for all the input so far, I really appreciate your time. I have already investigated most of the other options and I believe there is a market for what I proposed.
Do we have some prop design and electric motor expertise on the forums here?

 

What you seem to be seeking is to fit a supercharged V8 engine on a roadbike...

The Torqeedo's and others use PCM to get the huge amounts of energy to the motors, leaving the motors in the moving water-stream to harvest electricity may destroy the motors... Some have "promoted" regenerative capability and is not workable or effectively useful...
Think:
- a different set of stresses on the bearings,
- a different set of loads on the seals,
- an electrical incompatibility (square wave in the PCM and digital return control signals and you want DC back for recharging?)
- The engine is underwater - do not push your luck...
- On the Torqeedo's the propellers are optimised for forward thrust...

A different shape on the propeller is needed for harvesting energy from the water-flow... and a propeller to push is incompatible with the 'harvest' option...

I found the best option was PV 'solar-panels'... and some go for wind, I considered this but at 400W peak output only good to trickle charge house batteries to maintain charge from anchor-light and occasional bilge-pump and a call-base-alarm system use...

In emergencies, a petrol charge capability when fully electric powered, is a sensible standby... anything else just unnecessarily adds to complexity and things that may go wrong, or lack in cost-benefit-reliability...

Ask Claude Desjardines: claude@torqeedoaustralia.com about fitting to a Bob Oram 44C "Schools Out" and to another large trimaran... Also see page 14 of the catalogue, "Current Sunshine" is one I have had a ride on when he was buying/testing Torqeedo...

 

Is the Torqueedo an ac or dc motor? I am under the impression that only ac motors can act as generators.

I
Plan on an outboard design with only the shaft and prop in the water.

 

There are significant losses in gears, fwd & reverse and turning the drive shaft 90 degrees... Electric engines, because of their weight handicap and other factors are best set up 'inline' with a planetary gearbox to reduce the rotational speed of the propeller for greater efficiency... With the motor (petrol outboard fashion), up high, water cooling requires a pump (more energy wasted)...

Do a (google / wikipedia) search on "PCM" it is DC but pulsed to control the rotational speed and to deliver optimum power - I think PCM is the correct 'term' - memory is unreliable sometimes - Also, relying on failing memory, diodes ensure that "plus" is fed one way and "minus" is fed the other to deliver DC... A small alternator does not need brushes as the magnetism is usually delivered by "rare-earth-permanent-magnets"... Large commercial generators usually utilise "exciter coils / circuits"...

 

Last time I saw "Schools Out" was at a boat building yard in the Redlands having the Torqeedo's removed and 60 hp 4 stroke Yamaha fitted.

 

I'm suspicious about one of the assumptions that you seem to be making about regeneration, Stan. You say that regenerative systems take about a knot off the speed of a keel boat so you expect the same from your trimaran. I doubt that equivalence holds. The trimaran gets a lot of its speed advantage from the fact that it has less resistance than the keel boat, so if the regenerative system adds, say 5% to the resistance of the keel boat it will add, say 20% to the resistance of the trimaran (I'm just making these numbers up for an example, I have no idea if they are reasonable).

 

That may be true, but I believe the only way to truly find out is to build it and test it. I beleive weight is a bigger factor thn drag but I'm not a hydro dynamics expert

 

Next time your out sailing stick the tohatsu down, leave it in neutral, and see how much speed reduction you get. Put it in gear to stop the prop and see if there is a difference. If there is then somewhere in between will probably be close to waht you could expect for speed loss.

What Masalai is telling you about losses from gearboxes and belts is true, thats why almost all electric motors for boats are direct drive to the prop shaft from trolling motors to torquedo to Azipods for ships. The power loss from gearing and / or belting is too high an energy price to pay for a system thats generating small amounts to begin with.

I seriously doubt you can cobble something together that will mount like an outboard, both power and regenerate, be efficient at both and cost something reasonable.

Steve