How fast can our electric catamaran motor... forever!?!

[@jims5338]

That was really great to see! I've often wondered if with sufficient solar go could motor for a loooonnngggg time at moderate speed. Add in the ability to regen and you have an infinity device! Really confirms what I'm going to do when the old diesel finally gives up the ghost.

[@SailingElectra]

Yeah, I was chatting to a sailor doing a large ocean crossing, and he once ran out of fuel so now carries way more fuel than he needs. I was saying he should get an auxiliary electric motor and a few more panels, because I consider my boat to have an unlimited range! Of course it all depends on speed, but so does diesel consumption, the speeds are just higher.

[@run14me]

Great to see y’all getting on with it:-)

[@SailingElectra]

Thanks Chris, yeah enjoying it so much!

[@DavidMozingoREALTOR]

Thank you for sharing! Can you tell us how much your boat weighs approximately? I have a cat sailboat that is 6 tons & plan to use your same setup.

[@SailingElectra]

Hi David, we're 5 tons. I know a much heavier boat that does similar speeds with similar power levels, so in my opinion drag is far more important than weight.

[@markusspeetzen9505]

I don't recommend that, but it also depends on the area you're sailing in and the purpose you're using it for. I have a similar project, a 10 metre catamaran with two 7kw e tech motors (Poland). Kraütler or Aquamount (Austria) also work well. You've seen for yourself that at 6 knots the propellers are already taking in air because they're too small. I have 15-10 inch bronze propellers. The difference is the much higher torque; the 1kw more doesn't matter. The bigger the propeller, the better the power transfer. Don't confuse this with the pitch, which is for speed. For the large propeller diameter you need motors with a lot of torque, which doesn't use more power; in fact, the opposite is true because it's more efficient.

[@cemyalcin3062]

How many kn does full throttle cost in a calm sea? Why didn't you measure full throttle speed?

[@SailingElectra]

I don't have anti-cavitation plates on the motors yet, so at full throttle I am getting cavitation which makes it difficult to do for long periods to make measurements. From the tests I have done, it looks like it's just about 7 knots at full power, 12kW.

[@run14me]

I sold my Catalac to save for the circumnavigation vessel:-). Trusting and Believing for it (TAB)

[@SailingSquib]

You missed the chance to be the forst circumnavigator to do it in a catalac?

[@LostYogi]

what is that clanking sound? is it waves hitting the hull or ?? it stop when you stopped the boat around 6 minutes in

[@SailingElectra]

It's the autopilot. I've serviced it over the winter and replaced the belt. I suspect I also need to turn the sensitivity way down. It'll still be noisy but should sound more like an electric motor and come on less often.

[@LostYogi]

Thank you @@SailingElectra I was afraid it was the sounds of waves as I have never sailed a catamaran before

[@CaptainShack]

Do you find yourself solar motoring "not really sure what to call it" as often as sailing? :D

[@SailingElectra]

My sails don't work yet, I still need to raise the boom to clear the panels, so I'm just motoring at the moment.

[@CaptainShack]

@@SailingElectra Oh Gotcha. Don't get me wrong I think is very cool you can run off solar. Has me re-thinking the amount of panels I can fit on my prout.

[@SailingElectra]

@@CaptainShack I'm dying to get the sails working, but I couldn't find an available rigger, and didn't want to miss the sailing season. My view is always to maximise the amount of solar you can fit. That way you could have an auxiliary solar motor for those sunny windless days. It takes very little power to move a boat in smooth water, so there's very little to lose. My Dinghy uses a 12V motor that can put out 720w. I suspect that even that little motor would move the boat quite well at low speeds. I'll figure out a way to mount it and test at some point.

[@ot1k]

Can you show speed and power consumption using a single motor?

[@SailingElectra]

So I'm guessing you're asking because you're curious if it's more or less efficient. I'll do a video on this at some point, but I have done some testing and found that it is always more efficient to run two motors rather than one. At high speed it seemed to be at least 5% more efficient to run two motors, maybe even 10%.To people with diesel or petrol engines this sounds weird, but it is definitely the case with electrics. I believe this is because the motors are so efficient, that what you lose in friction and other running losses, you gain far more in a larger surface area moving the water at lower prop speed, and less cable loss with lower amps running to each motor.

[@bluemu]

Very interested in yr observations on 1 v 2 motors. Look fwd to your future episode on it

[@SailingElectra]

@@bluemuhopefully I get a windless day soon, otherwise definitely next season. I have no doubt two is more efficient though, it's just a question of how much.

[@jorgeizquierdo7583]

Isn't possible to reduce the sensitive of your autopilot? look like it is way too responsive to small deviations. With low sensite, motoring at 4kt without waves, the autopilot should only do very few and small corretions.

[@SailingElectra]

Definitely on my to do list! If I can figure out how 😊

[@marviwilson1853]

All vessels both mono hull and catamaran have complex underwater shapes and curvature. I wonder how much of that shape is to eek out a bit more speed for a given power and how much is for stability, seaworthiness and comfort. The thought would be that if solar boats only want to be cruising around at 4-5 kts then why would you include the cost of creating complex shape if the only real reason for complex shape is to allow the hull to go faster through the water! A custom solar catamaran could surely be made much, much cheaper if built as a simple welded aluminum box section tapering at the bow and some thought given to shape at the back to minimize wake turbulence drag. Your not going that fast anyway. All necessary thought off course given to structural integrity. Very quick to build as well. Welded flat panels, simple frames and beams.

[@markusspeetzen9505]

welded flat plates are you serious?. Look at Richard Wood's design, there is nothing complex and it works perfectly.

[@marviwilson1853]

@@markusspeetzen9505 Looked him up. All designs have complex underwater curves that are time consuming and expensive to manufacture.

[@PeteGerard-p2f]

Sorry but your efficiency on a glass calm day is simply not relevant. The bottom line for any boat is, can it get me out of trouble? If that boat had to head into 30+ knot winds it would be out of power in a matter of hours and into a whole world of trouble! Therefore going out on a calm morning, you'd be hoping all day that it remained calm otherwise there's no guarantee you'd be able to get back to port without assistance.

[@SailingElectra]

It is a sailboat, so hopefully when the wind is up we can sail out of trouble. We are planning some sort of backup though, either a small generator or a small outboard. Purely as extra insurance.

[@markusspeetzen9505]

yes, not entirely wrong, but you can take the best course for the wind and waves. In an emergency with a sea anchor. Besides, it still has sails and if not, you have a backup generator. So what's the point of painting it all in a negative light? It should be clear to everyone that the speeds and consumption are no longer appropriate. A car with a heavy trailer needs twice as much. So if you don't plan for reserves in a boat, you only have yourself to blame. Again, it depends on the area you're sailing in.