concept for an electric launch

Recently I made a concept for a launch.


Launches are very popular here in the Netherlands to make daytrips on the lakes and canals. Nowadays you see more and more of these launches being fitted with electric propulsion.
But I wanted to design a boat that is specifically designed for electric propulsion.
A boat wich was sligthly bigger then the average boats of these type, but also a boat to be used in demanding coastal waters that could stay out of a marina for an extended period and provide a couple with a perfect (campstyle) accomodation. All this in a more contemporary styling then usual.
To use the electric propulsion as efficiënt as possible I designed a sleek boat for minimum resistance.



As the boat is intended to stay out of a marina for several days in remote coastal waters it was not possible to use only batterypower. I had to come up with a small generator to recharge the batteries if needed. In the end I was able to work out a sufficient layout but it meant that the propulsion system was 3 times as expensive as a standard diesel propulsion.

But the concept of the lean hull with the generator powered electric drives can be scaled up easily. At the moment I am busy with scaling this design up to a 50 foot liveaboard trawler. On a bigger boat the relative cost of the propulsion system is lower. But these are considerations for a new concept.

I would love to have some feedback on this design.

 

The boat design is ok but I don't agree with the propeller and foil speed (bad for the fishes, beavers, etc) besides probably materials

As a suggestion I can tell that both catboats and sharpies were developed by dutch people to sail at relative speed with low draught, you can find plenty of designs besides sandbaggers and Paolo Bua light wooden boats to check and design one and add electric propulsion.

In laptops the major consumption is the battery system, if you unhook the battery the laptop will consume a fraction and a used PV panel will bring propulsion to a DC trolling motor just with a voltage converter all the output that generates

Still you also should check rowing dinghies and the solar thermal propulsion thread, also pedaling propulsion using the bike transmission

 

Welcome to the forum Johan:

Electric boats have interested me for decades, I attempted a research project for a client about a hybrid live aboard motorsailer using diesel electric power a few years back. Storage capacity back then was an impediment, but with improved battery systems this may be less an issue. Nigel Calder wrote about hybrid systems a few years back as well. I think he suggested that (at the time) hybrid propulsion wasn’t efficient enough to justify unless house loads were a part of the overall system.

I am interested to see how your design scales up.

 

For economical/efficient low speed propulsion you need a hull that's quite slender for its length and a prismatic that's on the low side, (none of those fat/slab-sided/high PC hulls).
A stern that's double-ended at the WL, an emersed transom is a big drag, (no pun intended,) your transom stern is a big no-no for an efficient hull at displacement speeds.
Look at a "Rangeley" hull form, or even some old-time steam launches from ~1900.
Something that can move at a S/L ratio of 1 with very little power.

 

Thanks for your usefull feedback. interesting point about the batteries. I started this design with a classic dutch rowing vessel but along the way I found out that a modern vessel could have a far better performance. The rowing part I reserved for the tender that is integrated in this concept,

Regards, Johan van Dijk

 

Thanks Rangebowdrie for your reply,
I was aware of this problem.To overcome this the transom of this boat is kept above (on) the waterline. Doing it like this means that I could use a bigger propeller to improve efficiency.


Further I planned the main weigths (motor and batteries) well forward to prevent the stern to sink in under speed.

Regards, Johan van Dijk

 

Good to know I checked these dutch boats and they are mostly good atemporal designs and can be brought back

While I usually try to bring "modern" lines however the thing is that "performance" is a sort of marketing buzzword to try to give importance to some aspects of sailing boats like that or internal space while not mentioning motion stability or stability curve among others, and that's where most of classic boats have their advantage while also they can be redesigned

Most of old sailboats were built with sturdy wooden construction to transport plenty of cargo and people and bring structure safety, and these same designs can have weight reduction with other recent wooden structural and hull skin methods, besides fabric on frame and so using less resources to build boats and making easier to climb in beachs.

You could check Paolo Bua wooden lightweight boats for inspiration

 

It won't matter, as soon as the boat starts to move the horizontal transom will produce a given width of turbulent/disturbed water which causes much drag.
As I mentioned, study the lines of a classic steam launch, or an Elco electric launch to see the preferred shape of stern sections, (actually all sections,) to have a hull with low drag.
Elco Classic Launches | Elco