Definitive yacht - Power/sail catamaran opinion

You might have a look at this posting, and some others in this subject thread.
Gamefishing for Sail Under Sail (and power)

There was a time in the past when I was following this 'diesel-electric' subject very closely. And you can probably find a lot of those older discussions via a google search.

Realize that I am still very challenged with 'electrical subjects and designs'. You might be able to tell that from some recent postings I have made on this forum here...
http://www.yachtforums.com/threads/diesel-electric-propulsion.2229/page-15
...where I am seeking out the latest available products to power up a rim drive propulsion system for a catamaran under 40 feet. (BTW, that fellow member Karo offers some very insightful electrical knowledge that might help explain some of the pitfalls to overcome when developing these diesel-electric systems)

I'm currently researching some of the state of the art in DE propulsion for 2 reasons.
1) there has been a lot of talk about alternate (single outboard or twin outboards) to power up catamarans smaller than 40 feet.
2) I have a good friend who is looking into the subject for a new 50 foot cat he wishes to build.

And even after the experiences a friend of his and mine had with a custom 45 cat he had built down in Peru a number of years ago,.... with a Glacier Bay OSSA DE system onboard. He had lots of problems with that new system and sold the boat. And that company (that I thought was most promising at the time) dropped out of the business not long afterwards. (I think their technology dreams outraced them).

Bottom line, I remain cautiously optimistic about the tech even today. In other words, I think there are lots of reasons to think it will work in many instances, but remain cautious of inflated claims.

Hmm, looks like dead discussion...I will add my comment never the less.....interesting though , with prices for that tech coming down, tech getting better..and new developments arriving....
Still, caution is advised. El.RimDrivrs in all sizes...
I am just looking at buying a Cat 45 to 55ft ...and looking to make it as energyefficient as poss.
It is totally clear that diesel cant be left out of the plan...but...thanks yo cheaper LiFePo batteries (sourced from the People's Empire)..one can use a generator, or better, powerful beltdriven ones..directly from drivemotors..and rapidly charge the LiFePo's at 1C ...

With lead batteries one had to charge slooowly...wasting a lot of fuel with a synchronised 50hz genset revving at 1500 or 3000rpm....lead batt. having a cycle loss of min 20%, LiFePo 5%,....

LiFePo...makes a huge difference.

Then, PV costs 0.3 $/W....so 2kW on a Cat shld be poss. x 5h/d....

Cost of this: 30kWh Batteries w BMS is 10 to 12k$
PV of 2kW with mppt is 800$

You can go parallel hybrid with 10kW motor/gen , beltdriven...if theres enough space, 15k$ + batteries

Or serial hybrid ready made by Ocean. Volt.....using their computercontrolled vp prop "Servodrives"...15kW and up to 3kW generating power @10 to 12kt....so they say.....but for a 2 pod system.for Catamaran.with all necessary equipment and a rather wimpy batterypack....I think it was quoted as 130k+EUR, and that was not including consultancy and installation....

There are other Podmakers with generating options....but one must keep in mind that a prop is made to perform in ONE direction only...
From some tests a Norwegian institution did for a new hybrid sailing brig...they measured 30 to 35% of thrust was the generating capability, fixed pitches and 2 diff diameters were tested.

As a prop is a set of rotating wings meant to create the max poss lift...in one direction...it wont be good in the other.

A symmetrical profile would do better as compromise...maybe not a bad approach for a sailing boat needing more regeneration than thrust.
In aviation a super efficient motorglider has a distinctly assymetrical wingprofile whereas an Aerobatic plane, meant to perform in any poss. inclination, upsidedown too, has a symetrical profile.....it will not get you to your destination with the same fuelburn though!

The only way i see a prop doing both well is:
It needs to control pitch AND rotate the pod...once it faces the other direction it only has to change the angle off the rotationplane towards the flow by the pitch angle it had in thrust config (pitch +angle of attack) + 2x angle of attack....now we have a watermill...chk under Kaplan hydro turbine....a propeller

I still very much like the idea of a counterrotating pais of blades in a RimDrive Pod....pushing my boat and baking my bread!....retractable of course!!!!
does tht make sense?

I wonder what this relatively new work on SSBT (solid state battery technology) might bring to the equations?

PS: I must admit to not knowing a great deal about the technology at this time

gday ,
there are a few developments cooking, supposed to be much safer and have higher e-density.....
You should also have a look at Li Sulfur batteries, a UK company has seemingly started to sel them, claiming already 400 W/kg expecting 50% more in next 2 years. Lighter and robustrr than LiFePo too....still work with a nail driven through them...or bullet.

I can look up the Co name...but sure youll find it.

adding to RimDrivePods, I jst recieved an answer from a German Company making them up to 20 or 30kW....theyre not considering regeneration for time being..
I have looked at Pods a bit closer again and suspect that the shroud eith its inner profile is even less usefull in reverse/regen than an open thruster prop ....you cant rotate it facing rear forwards....so you only can have the waterstream power the blades...
If you have a look at that shrouded water generator..forgot name...not watt to sea...that shroud looks different to the propulsion pod shrouds....more of an inverted funnel...decreasing pressure and waterspeed behind prop to increase efficiency...like in a kaplan hydro turbine...those get well past the limit for open turbines of 59% of kinetik flow energy.

to you idea of 4 serial gendets driving boat and house loads...to gain quite a bit efficiency I would have 2 diesels driving the shafts with parallel mounted gen/motors with clutches...and the other however sized gensets that could work for house only or help out the diesels by powering the parallel motor/gens....You just have to figure out yhe power sizing of all together.
Not too difficult in general...but the devil surely hides in all thise details..esp yhe electric/tronic ones!!!!!

adding to RimDrivePods, I jst recieved an answer from a German Company making them up to 20 or 30kW....theyre not considering regeneration for time being..
I have looked at Pods a bit closer again and suspect that the shroud eith its inner profile is even less usefull in reverse/regen than an open thruster prop ....you cant rotate it facing rear forwards....so you only can have the waterstream power the blades...
If you have a look at that shrouded water generator..forgot name...not watt to sea...that shroud looks different to the propulsion pod shrouds....more of an inverted funnel...decreasing pressure and waterspeed behind prop to increase efficiency...like in a kaplan hydro turbine...those get well past the limit for open turbines of 59% of kinetik flow energy.

to you idea of 4 serial gendets driving boat and house loads...to gain quite a bit efficiency I would have 2 diesels driving the shafts with parallel mounted gen/motors with clutches...and the other however sized gensets that could work for house only or help out the diesels by powering the parallel motor/gens....You just have to figure out yhe power sizing of all together.
Not too difficult in general...but the devil surely hides in all thise details..esp yhe electric/tronic ones!!!!!

sorry for numerous typos....my fat digits tackling a phone screen!

This is mostly too deep for me and Brian is definitely the go to guy on this, but two things struck me. 1) those pod drive would produce a huge drag while under sail even if you managed to find folding props for them. 2) it sounds like a lot of equipment you're planning to put in the hulls, and I wonder how much living space will be left. Cats have great salons and deck space, but the hull space for staterooms, heads and sometimes galleys is limited.

poddrives, saildrives and standard shaftdrives (with their 15 to 20degree angle) all have similar drag...of course a feathering/folding prop helps

and, to accomodate those 4 gensets one would need a rather large Cat....more than 100ft?!

It can be done and has been done before. Just google Planet Solar.


This is the solar powered boat that crossed Oceans only under solar and battery power. The picture was taken at Port Adriano at Mallorca, Spain.

yes indeed...I ve followed the progress of that boat.....but to create that large surface area without too much weightpenalty....$$$$$$$$!!
I remember the budget for that boat was in the millions...over 10m?... but close anyway......but tenniscourt and a Helipad can be provided for.

Turanor Planet Solar was built in 2010 at the Knierim Yard on the Kiel Canal in Germany. This yard is famous for very innovative one off projects.



This project was the combination of a lot of the state of science regarding solar technology, electric energy storage and electric propulsion. Especially the large, slow turning surface propeller were top notch technology.

A two masted Dyna rig combined with this technology could easily make up for a app. 24 meter pollution free long range motor sailor. And this boat would even be usable under the practicable point of view.

Slow turning surface prop...never heard of that application.
I had just posted on the dieselel. thread...that theres intense renewed interest in freepiston linear generators as range extenders. Very efficient, fuel to el. conversion at 45% where best diesel in up to 500kW range get to 40%...mechanical, not yet electric.
Plus they can burn all kinds of biofuels by altering compression ratio, it seems.
Imagine destilling coconut moonshine in Kiribati to continue your safari!

If these motors get on the market they surely would be the way to make hybrid powered yachting more feasable, even for smaller boats.

You have added too much complication to those rim drive propulsion units,...asking them to regenerate. Forget regeneration with vessels, it works with autos, but doesn't make sense with vessels.

It will be a chore just to get those rim drives to work efficiently and with less complication. Tuck them in when not in use, and forget the drag they produce to gain regeneration.

Have you looked thru this subject thread,..

https://www.boatdesign.net/threads/new-age-trawler-motorsailer-kite-assisted-poweryacht.20319/

and particularly this Humphrey design idea

You might even refer to it as a stabilized monohull'

Concerning ducted regeneration,You are right....the ducts are circular wings with a camber working only in one direction, plus a propulsion duct has a smaller diameter in the rear.....So if you want any kind of regen from your prop it be an open one. Regen seems to be app. 10% of engine power at same speed.
I guess for a sailboat , one that doesnt need to motor often, a light one, such a propblafe with cp function might work eell as generator and propulsor...being averagely efficient at both. But a light sailboat will draw more benefit from it?
Do I have a point , or am I getting something wrong?