Building Solar Electric Propulsion (Motor Katamaran)

Thank you SolGato.

Yes. The trolling motors are branded "Haswing Protruar 3.0", the underwater part is "Caroute". I cut the steering heads with the tillers off to make it remote steerable from the wheelhouse. For this reason I added some electric and mechanic parts, which are not elegant at all (will be covered later on).

Superstructure is part of design and already completed and will for sure cause a lot of windage. But: In our northern Europe climate we will be on the water not only on lovely sunny days, but often also at cold and rainy days. So we need a cabin as weather shelter. And for old age reasons it must provide standing headroom, a separated toilet and a galley, table, seats, bunks and so on. Our waters to navigate on are small canals, small lakes, small rivers with low current, so it will fit.

The core of the electrical system consists of fitting parts stemming from the (in Europe) well known and regarded as hight quality brand "Victron energy". Each battery tells me via bluetooth the voltage of each of its 8 cells and will close off in case of overtemperature, under- or overvoltage if any cell. Additionally the 4 batteries have a line to communicate with an battery management system build for up to 6 of those batteries. If I decide later to go by a 48 V system, the same BMS and batteries can be set up in this arrangement.

 

Your boat looks great Heinfried!

A lot of windage, yes, but as you said should be manageable in your waters.

I have no doubt it’s going to be a comfortable and quiet cruiser that you and your wife will thoroughly enjoy.

Great choice on the Victron components. Their stuff isn’t cheap (especially the batteries), and some are reluctant to spend the money and instead take the DIY/no brand route, but the Victron stuff is well worth the extra investment for safety and complete system integration, and their ability to network, monitor, and control the system is their biggest strength IMO.

With their products, all you will really have to do is occasional software and firmware updates which typically introduce very useful features.

Nice job on the remote steering modification of the motors.

Will you keep independent steering control of each motor or tie them together?

I guess it depends on placement and spacing and hull style, but with independent steering and independent thrust control, there may be an opportunity to use the motors as thrusters for increased maneuverability which may be handy in narrow waters, current, when docking, etc.. especially given displacement and windage. Something to think about.

I’m not sure if those Caroute/Haswigs have all the same features as Caroute’s line. If they do, they have low and high voltage protection built in and a “limp mode”, and with their PWM ESC design their peak efficiency will be around 80% throttle.

Hopefully you will retain the transom mounts and be able to remove the motors from the water during prolonged mooring anchoring. The finish does not hold up well, especially in saltwater, so the cleaner you can keep them the better.

If your waters are known to cause a lot of growth or there’s a lot of debris that could damage the finish, I would suggest coating the motors with another protective layer of finish.

I have had to replace housing components and have experienced seal failures due to corrosion. An Oring only provides a good seal if it has a good sealing surface, and once the aluminum starts to corrode the sealing surface is compromised. In an effort to minimize this, I have started using grease on the Orings to better protect the surface, and have suggested Caroute do the same.

Truth be told, Caroute did not properly design their Oring seals. They have made some improvements, but the basic design is still not ideal. They are not the only motor manufacturer to mess this up BTW.

If I bought a new pair of motors tomorrow, I would coat them for added protection, probably with something like PlastiDip which can be easily removed for servicing and touched up or recoated when needed.

The good news is Caroute encapsulates their ESC in silicone and they use gold plated connectors, so minor water intrusion or condensation should not affect the electronics if caught in time, and they can/will supply replacement parts.

From my experience, the only time I have run into trouble with my boat which is smaller but has the same amount of propulsive thrust, is when navigating river mouths with strong current, and when crossing the prop wash of very large and powerful boats. The small propellers will slip and suck air and being as small as they are, lack the bite they need in those situations. I now run larger 2-blade props which has helped.

One great advantage to the electric motors and their instant torque is the ability to use the motors as “brakes” in that you are able to go from forward to reverse very quickly with instant torque that produces a responsiveness that makes controlled maneuvering a breeze.

Anyway, I’m just making these suggestions as a way to protect your investment and to improve reliability so you can focus on enjoying your boat as much as possible once complete.

I have been building solar/electric boats since before they became popular and am always trying new things and have learned a lot in the process that I’m happy to share.

I’m certainly not trying to be a backseat designer, it’s your boat and you know how and where you intend to use it and what decisions need to be made to meet those goals.

Hopefully my posts are not misinterpreted as being critical and are coming across as supportive.

 

Thank you SolGato, your posts are valuable and very appreciated. My range of boating is only in fresh water, but corrosion is also to me a point to watch out.

The steering is projected as independend for each motor (direction and rpm). I did not yet decide what device I will use to handle the 4 potentiometers at helm.

The pic shows the back side of the sockets for the control lines for each motor.
The boxes are fitted at the inner side of the transom near the motors to allow the motor plugged/unplugged.
Motor power lines run separately through the grey tube.

 

While reading SolGato's encouraging post I am reminded of the electric Gondolas I drove, commercially, one summer.
They had a pair of similar motors, one frwd and one aft.
They rotated 360 degrees as well.
All controlled from two foot pedals.
Very, very maneuverable.

 

A motor and generator can be the electromechanical device. When the energy conversion is electric to mechanical, it's a motor. When the energy conversion is mechanical to electrical, it's a generator. This is how an electric vehicle's motor recharges batteries during braking.

 

Known to many as regenerative braking.

 

Re (in water) generator recharging or regenerative breaking. I don't think this will be a point to my "application" because of the low speed. I'm not sure, if the electronic of my Haswing motors are capable to feed electric current back to the batteries if they are driven by water current. Additionally the fitted prop has a low pitch which is not advantageous for this purpose.

In the last years, when I was projecting the drives I bought three sets of electric motors (all brushless permanent magnet), thinking to construct and build the drive myself. As time went by I realised that I will not have the time to tinker with all the things I wanted. So I turned to the trolling motors as a first solution which can eventually be replaced someday with a better system.
For these other motors I have external ESCs and tey are capable to recover electric energy.


Maneuverability: There is a third Haswing Protruar 2.0 (960 Watt) waiting to be placed as a "bow thruster" for box maneuvers (not in a tube, crossing the bow, but open between the demihulls).

 

From Sol Gato,

Most fast flowing River mouths and river Rapids that I have encountered will have Eddys that run in the opposite direction of the strong flow. Those counter currents usually run pretty close to the land Riverfront areas and sometimes are only inches away from the river/ land border. I usually manage to find those Eddys and can ride them Upstream when I can't overpower the main flow. I think that kayakers also use the same principle when paddling Upstream against a current.

It's nice to have the maneuverability to turn a boat within its own length, especially when operating in close quarters or in very narrow streams. It also comes in handy when you have to quickly point into a boat wake so that it doesn't hit you broadside. I use a single trailing shaft e-motor similar to those in Asia which are used in racing with very small propellers, as it allows me to run at a very shallow Draft that a larger prop can't do. I can also quickly pivot the trailing shaft to get extreme turns quickly and also go deeper so that the prop doesn't suck air when the wake bumps come along.. Of course that requires my manual control which isn't as easy / effortless / luxurious as when two Motors are used. Of course, my methods may not work for everyone, just another idea that works well for me anyway.

 

Regenerative braking is extremely inefficient when involving a boat, compared to a no slip land vehicle, the way I understand it. Lots of losses due to slippage and losses because of the different propeller designs required when optimizing propelling versus optimizing when generating from a braking boat.

 

Hey, that sounds better than one of my first boat jobs -running houseboat owners out to their houseboats with a patio boat that had an outboard with an untrusty idle that just loved to cut out at the last second just as you made your approach!

I learned a lot on that job about predicting the momentum and inertia of loaded boats and how to best approach houseboats swinging around their moorings.

Crashing into an owners boat always made for an awkward weekend and extra anxiety on the rest of the shuttle runs, so you had to develop skills quickly, skills that have stuck with me ever since.

I have found Independent thrust steering to be an excellent cure for boat maneuvering anxiety

 

SolGato, curious if your boat be run (in a limp home mode) if one of the motors fails?

 

If one of my BMS’s go into over/under voltage or temperature protection and disconnects, then both motors go into “limp” mode since my bank is 2 x 12V in Series for 24V, but ONLY because my solar system will continue to supply enough voltage to allow the ESC’s to continue to operate.

When this happens, depending on how strong the sun is, the motors have very little power as increases in throttle cause the voltage to drop as the MPPT tries to figure out what’s going on as it converts power from the panels.

It’s basically enough power to barely get to shore. If there is too much wind or current, forget about trying to get to a particular spot.

Normally the way “limp” mode works is if voltage falls below 20V (if I remember correctly) the ESC limit the amount of current draw to protect the batteries as they were likely designed before Lithium became a thing.

However with the solar chargers it behaves a differently because the motors end up thinking there is enough voltage, but aren’t able to draw much current so their power output varies as they are basically running off the sun.

Hope that makes sense. It’s more complicated due to the solar chargers always being connected to the bank.

Now if power is just plain interrupted, the motors would cut out and need to be returned to neutral to reset before propulsion is restored.

If the batteries disconnected due to a BMS disconnect, then the master power switch has to be cycled so the BMS’s can reset AND the motors “rebooted” which takes about 5 seconds.

But, after writing all that, I’m wondering if I misinterpreted your question and maybe it was related to loosing a motor or full power of one motor and how it affects ability to steer?

 

It's related to steering with only one motor being possible. I thought maybe having the original swivels unlock might help if the two Motors can be operated independently, or easily converted to do that (or using a backup rudder, long paddle, etc.).. It might not be relevant because of the way you use your boat, mostly in the protected river area? Obviously there's all kinds of backup systems if the boat can't operate properly, like volunteer or paid Towing from other boat traffic, Coast Guard if you are offshore, etc.

 

Funny story about that and you bring up an important point.

I learned the lesson of just how effective having one motor on each hull is for steering a boat both ways early on very late one night while I was cruising around the mooring field under a Summer full moon.

The trades had died out and I decided to hop on SolGato which I had tied up to my Farrier Tri on mooring in our Bay. I set out for a cruise not being able to resist the conditions, and I was a few rows deep in the morning field away from my Tri after cruising about a bit, when one motor cut out and all she would do is tight donuts like a balloon that gets away from you as you try to blow it up.

I knew I was in trouble because I wasn’t prepared and it was late and anyone on their boats were asleep, and just as I realized Houston had a problem, the wind kicked up and switched off shore. Now I was really in a bind. No anchor, no sweatshirt, no beer!

I was drifting and knew my last resort was to try to maneuver as I drifted out through the mooring field over to a friends 40’ steel monohull. So I used the wind, current and single motor thrust to work my way back and over up alongside my friends boat and proceeded to bang on it, but he likes to drink rum, and well there was no hope of waking him.

My boat is very low to the water line compared to his, and there was no good way to tie up without his trying to pick mine up, or the two slapping together, so I just hung onto his gunwale with one hand and started troubleshooting my motor with the other.

At that time I had each motors ESC wired up underneath each hulls corresponding hatch with their own master power switch, and I ended up discovering an intermittent faulty switch that was making poor contact that I was able to fix so I could restore power to the motor.

In the end I made it back to my Tri, but the experience had me brainstorming the rest of the weekend on how to handle/minimize this in the future, which ultimately lead to designing an onboard anchor and a removable rudder which I already knew I wanted to incorporate for sailing purposes.

I also spent some time figuring out if the boat could be steered with my weight strategically positioned while using a paddle which it can, but only slowly and in calm waters.

So now when I venture out (not up rivers) in the ocean I take the rudder with me, the rest of the time the paddle.

And of course with the anchor now onboard and easily deployable, I can hold myself in position without the use of a hand while I assess the situation.

So in short, the lesson learned is that a pair of motors are incredibly effective at steering their respective hulls when one, the other, or both are working, and if you are going to use the independent thrust of two spaced apart motors to steer a multihull like mine, you better have a backup plan!

 

Back to Heimfried’s build with a hopefully a few more helpful suggestions…

Regarding the motors, if you decided not to add a protective layer of Plasti-dip I would highly recommend removing the housing bolts that hold the x3 sections together and applying Tef-Gel to the threaded portions and the underside of the heads now before the motor are put into service. You will thank yourself later if/when you have to service the motors.

The reason? Well, due to the design of the bolts and the threaded holes being exposed to the water at all times, and the bolts being stainless and the motor housing aluminum, the bolts will seize due to corrosion from the dissimilar metals and the threads filling with sediment. If you’re lucky, you will be able to remove them with only stretching occurring, but they are more likely to break if you aren’t very careful. Either way, they will likely not be reusable. It only took a few seasons of use for my bolts to seize and my boat is trailered and spends half the time in fresh water and the other half in salt.

I ended up swapped all my bolts for American made versions which have a consistent overall diameter (slightly larger and stronger) versus the necked down shank style that is common with a lot of Chinese made hardware and how they form the threads. This eliminates the stretching and twisting so they can be re-used, and the addition of Tef-Gel as described above combats seizure and corrosion while sealing up the threads keeping the water, crud and salt out.

Keeping these areas protected (where the bolts pass through/seat in the housings) is very important because the corrosion that develops due to dissimilar metals will otherwise creep in toward the Oring sealing surface from these points, and may lift the finish or corrode the metal enough to disrupt the Oring’s seal allowing for water intrusion. And as I mentioned previously, I would also suggest adding grease to the Orings which are installed dry. The grease will keep the sealing surface in direct contact with the Oring from corroding. BUT, pay attention to the Oring material and use an appropriate grease. Real silicone seals need an appropriate grease, synthetic seals work with a wide variety of greases. The grease also allows the Oring to roll and squeeze preventing damage during assembly which can be tricky when you take the motor completely apart as the armature wants to stick to the housing, making centering and seating everything a bit more challenging.

If you sprayed a few layers of PlastiDip over the whole motor assembly, you could probably avoid the need for Tef-Gel as it will seal up the intrusion points.

I have included a few photos below to show why I am advocating for this preventative maintenance. The first shows the corrosion creep from the threaded holes in the end cap and the second if you look closely shows the finish lifting in the sealing surface area which allows for water to get past the seal. Removing the finish and using grease with the Oring sealing directly to the machined surface is more ideal for long term reliability. And the last shows the silicone thermal potting used to encapsulate the ESC to protect the components from vibration and moisture and to draw heat away from the circuit boards and transfer it to the motor housing. If you do experience a leak, this will protect the ESC. Now I can’t say for sure your motors are built to the same standard, but I can tell you there are some big brand name motor makers that don’t do this and have housing designs that are prone to leaking, with more than a few customers experiencing failures.

Regarding motor control, when I originally started designing my motor system for independent thrust for steering, I planned to incorporate and program a joystick for control, but after using my prototype wired remote, I decided I much prefer true independent control of each motor as it makes a difference in situations where there is strong current, winds, uneven weight distribution on the boat, etc., by allowing for very subtle or aggressive adjustments. It’s also easier to manipulate potentiometers with knobs in various helming positions than a joystick, and with less chance of someone bumping it or getting caught up on it. I actually steer by decreasing the throttle on one motor allowing the other to overtake, rather than increasing one to overtake the other. This produces much better results since the each hull always has drag, and is a more efficient way to maneuver although in general using the independent thrust of each motor to steer is less efficient than a rudder. I’ve been using this concept long enough now, that I get frustrated having to babysit a tiller controlled motor whenever I have to. I don’t mind it when sailing because you get a lot of feedback from a tiller/rudder, but holding onto a vibrating handle by hand with my arm behind me while facing forward to sight what’s ahead while in close proximity to the noise and fumes of an an ICE motor is a bit of a bothersome affair now.

Anyway, if you are considering the joystick option, take a look at the 4 axis Arcade style sticks. They are designed to take a lot of abuse and usually have a rubber boot option (soda proof!) and can be sourced with standard potentiometer values. The tough decisions are things like should it return to center, should it not and have some friction drag, should control be linear, etc..

My Caroute motors use a 10kohm potentiometers and I imagine yours are the same, with half the value for forward and the other half for reverse. FYI, doesn’t matter which way you wire them (some motors it does). At the moment, mine are wired opposite than factory because I’m running props that are reverse rotation from stock. Before that, I had one wired wire opposite so the potentiometers were mirrored in operation. The one thing I would still like to add to my remote is a lock out switch. Usually I am seated right next to my master disconnect, but sometimes when I dock or beach I’m out on the forward trampoline, and it would be handy to have a “kill” switch on my remote so I can set it down without worry.

And on the solar panels, it typically best to use a backing material that allows for ventilation, especially if they are a back contact design. The material (I like multiwall polycarbonate or a suitable corrugated plastic) will not only allow for better cooling of panels which will increase longevity and performance, but most importantly it will keep the panels from damaging your boats finish.

If you haven’t seen or read about Yamaha’s Harmo drive system you might check it out.

Developed for uses similar to yours with efficiency and low speed high traffic maneuverability (canals, water taxis, etc..) in mind, the system also has features like trim, steering and joystick control. I think it’s going to be a while before it’s available for the DIY builders, and no word about pricing that I’ve seen, but it may be of interest if you see yourself upgrading your motor system as you mentioned.