# 22m cruising cat design concept

Discussion in 'Multihulls' started by Becaris, Aug 3, 2008.

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### AlikSenior Member

And this is what You have said before:
So You run electrical motors from generator, or You have no clear idea how? If You do so, it is a 'serial' system.

2. Joined: Jul 2003
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### AlikSenior Member

Propeller diameter - optimum shafr RPM - speed data

I have done quick estimate for one of our designs - 60' catamaran with twin 75HP engines. For propeller diameters from 0.4 to 2.8m we found optimum RPM and corresponding speed. There are few conclusions (they are evident):

- After certain limit, there is no advantage of increasing prop diameter and reduction of RPM;
- Propeller diameter is limited by draft of boat; 60' sailing cat with draft of 1.06m (fully loaded) is likely to have prop diameter limit of about 0.6m.

Calculation result, using multiple speeds for optimum RPM
Propeller data
Diameter :0.400 Metres
Pitch :0.381 Metres
BAR :0.800
Efficiency :50.1

Engine data
Number :2
Power :55.000 kW
RPM :1690.729
Reduction :1.000
Shaft RPM :1690.729
Shaft torque :0.3106 kN.m

Vessel data
Speed :10.7 Knots
Thrust/shaft :4.838 kN

Calculation result, using multiple speeds for optimum RPM
Propeller data
Diameter :0.800 Metres
Pitch :1.107 Metres
BAR :0.800
Efficiency :68.1

Engine data
Number :2
Power :55.000 kW
RPM :481.718
Reduction :1.000
Shaft RPM :481.718
Shaft torque :1.0903 kN.m

Vessel data
Speed :11.8 Knots
Thrust/shaft :5.939 kN

Calculation result, using multiple speeds for optimum RPM
Propeller data
Diameter :1.200 Metres
Pitch :1.663 Metres
BAR :0.800
Efficiency :72.6

Engine data
Number :2
Power :55.000 kW
RPM :281.430
Reduction :1.000
Shaft RPM :281.430
Shaft torque :1.8662 kN.m

Vessel data
Speed :12.1 Knots
Thrust/shaft :6.166 kN

Calculation result, using multiple speeds for optimum RPM
Propeller data
Diameter :1.600 Metres
Pitch :2.228 Metres
BAR :0.800
Efficiency :72.0

Engine data
Number :2
Power :55.000 kW
RPM :193.656
Reduction :1.000
Shaft RPM :193.656
Shaft torque :2.7121 kN.m

Vessel data
Speed :12.1 Knots
Thrust/shaft :6.143 kN

Calculation result, using multiple speeds for optimum RPM
Propeller data
Diameter :2.000 Metres
Pitch :2.779 Metres
BAR :0.800
Efficiency :67.9

Engine data
Number :2
Power :55.000 kW
RPM :144.990
Reduction :1.000
Shaft RPM :144.990
Shaft torque :3.6224 kN.m

Vessel data
Speed :11.8 Knots
Thrust/shaft :5.931 kN

Calculation result, using multiple speeds for optimum RPM
Propeller data
Diameter :2.400 Metres
Pitch :3.325 Metres
BAR :0.800
Efficiency :61.9

Engine data
Number :2
Power :55.000 kW
RPM :114.195
Reduction :1.000
Shaft RPM :114.195
Shaft torque :4.5992 kN.m

Vessel data
Speed :11.4 Knots
Thrust/shaft :5.590 kN

Calculation result, using multiple speeds for optimum RPM
Propeller data
Diameter :2.800 Metres
Pitch :3.771 Metres
BAR :0.800
Efficiency :52.7

Engine data
Number :2
Power :55.000 kW
RPM :93.775
Reduction :1.000
Shaft RPM :93.775
Shaft torque :5.6008 kN.m

Vessel data
Speed :10.8 Knots
Thrust/shaft :5.010 kN

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### BecarisJunior Member

Alik, Yes, I said in 'rare' situations.

This is what the word 'rare' means. It is a word as opposed to normal operation, or 'the majority of the time'. So, if during a rare time I must motor more than three hours, and there is an efficiency loss compared to diesel during that RARE time, I can live with it for all the benefits I feel I am gaining the majority of the time as a hybrid operation.

You have never explained to me how I'm supposed to refuel those diesel engines you love so much once I'm out of fuel and no where near a dock. Hmmm. Or... how to avoid those fumes, or that noise? These are important points to me, ones that you cannot challenge with a diesel propulsion system.

As for your comment of 'the whole quote', I said, clearly, that I will be one of those usage patterns, and therefore, electric propulsion is very attractive. In other words, since you didn't get it, my patterns will NOT be recreational usage .

Finally, this is a thread about my project, not yours. I've stated clearly to you multiple times now that we will have to agree to disagree when it comes to the propulsion system I will likely choose for MY boat. Do you see me coming to your project and trying to argue with you about your choices? Finally, do you really believe you are going to convince me to use diesel over electrical propulsion at this point, or are you just barking up the wrong tree? Good luck with that.

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### brian eilandSenior Member

I will have to go back and re-read that article again myself (likely several times, to absorb it all), but if I recall the jest of it Nigel was being candidly honest about the somewhat over-hyped new diesel-electric systems for small craft. He is obviously a fan of the concepts, but he is not going to over-sell the ideas at this point of time.

I really appreciate Nigel Calder's thorough anaylsis of these subjects in his series of articles....and his honest conclusions that I'm sure he wishes were more positive.

I saw another short summation he did on wind generators on boats, and it did not look encouraging at all. I'll see if I can remember where I saw it.

As the Chinese say we live in interesting times, and it will be interesting to see the many new developments that our limiting supply of petroleum fuels forces us into. Too bad we have to battle such a poor economy with its restrictive development funds at this same time.

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### AlikSenior Member

As to the use of boat, believe me that 99% of 'boatdreamers' dream of long ocean passages, but end up sitting in marina most of time with short trips to nearest island. This is well proven by statistics

Don't You think critics benefit Your concept more than just applause? If not, just put Your concept on the wall of Your room, don't put it in public forum...

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### SpivAncient Mariner

Mast lowering

Becaris,
when I said continents away, I meant phisically, not ideologically (USA-AU).

My last single mast was 17.5m tall, two guys could move it around the yard on their shoulders. With spreaders, s/s wires atc we astimated it was 250~280kg.
The pictures attached show how I used to lower it. An electric winch would do the job in 45~50 seconds. Set up time (from Sailing) before and after about 10min.
The poles for the A frame could be used as (oversised) spinnaker poles.
With the frame up I could go under 6.5m bridges, with the mast flat on the roof and the frame down, 3.8m.
I designrd the system looking at what others had done and using more that une good idea together.
If you cannot lower your mast, you miss the beauty of Perth.

In my new boat I seeked to solve a few problem I had with the Marconi rig:
1. Mainsail,I dislike more than any other piece of sailing development. You see, my old boat woulg go very well with the jib only, while the main was just a real pain. Granted, not all boats behave the same, nevertheless there are also several other reasons I don't want a conventional main with boom. See my and Brian Eiland 'mainless' forum threads.
2. Unless you have dozens of wires, if you loose one stay, you loose the mast (happened to me)
3. The lee shroud is always slack. If you overtighten the rig in a cat you risk serious structural damage.
4. When you release the forestay (or the backstay) to lower the mast, the mast becomes very unstable and waves or power boats can cause distress or even damage.
The solution that fits me best is the "A" frame with 3 furling sails. Like i said two will be selt tacking.
This way I will have an infinite range of sail area for all situations.
Some people say: "yea, but you'll loose speed, pointing ability bla bla".
well I have enough 'practical' experience to know that they are wrong, in any case I don't care and I have no intention to beat around the world to windwards!!
I'll show you some drawing later.

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7. Joined: Jun 2007
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### SpivAncient Mariner

Diesel Electric

As far as Nigel Calder, he is very much PRO diesel this from the [FONT=Arial,Helvetica,Geneva,Swiss,SunSans-Regular]European Union hybrid-electric drive project [/FONT][FONT=Arial,Helvetica,Geneva,Swiss,SunSans-Regular]site:
[/FONT]

[FONT=Arial,Helvetica,Geneva,Swiss,SunSans-Regular]"Calder brainchild
HYMAR is the brainchild of Nigel Calder, boating journalist and marine electrical systems expert. He wrote the funding proposal with assistance from Ken Wittamore of EURMIG.
[/FONT]"

and:

"[FONT=Arial,Helvetica,Geneva,Swiss,SunSans-Regular]EU partners
European partners in the HYMAR project are Bosch Engineering - Germany, Malo Yachts - Sweden, Steyr Motors - Austria, Victron Energy - The Netherlands, Bruntons Propellers - UK, Enersys - UK and INSEAN (L'Istituto nazionale per studi ed esperienze di architettura navale) - Italy.
EMP will participate through a newly established European firm, E motion Special Projects (ESP), headquartered in Plymouth, UK, with research facilities in Bordeaux, France, near CNB-Lagoon."

In San Carlos, Ca, the Telsa Roadster does 0 to 60MPH in 3.9 sec and can drive for up to 244M on thousands of little richargeable Lithium batteries connected in series (laptop like).
[/FONT][FONT=Arial,Helvetica,Geneva,Swiss,SunSans-Regular]
So, good things are coming from all different angles of the globe.

And, this street legal
[/FONT][FONT=Arial,Helvetica,Geneva,Swiss,SunSans-Regular]electric [/FONT][FONT=Arial,Helvetica,Geneva,Swiss,SunSans-Regular]drag racing car holds the world record!!
Guess what: it's all to do with TORQUE.

The future in near!
[/FONT]

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### AlikSenior Member

2Spiv
http://www.electricmarinepropulsion.org/Pages/Technology_hptorque.html
This is good sample of promotional publication!

Because both horsepower and torque in a diesel drop sharply at low rpm, the propeller turned by a diesel engine must be undersized. A large prop that a diesel would in theory have enough torque to turn at high rpm would stall the engine at low rpm, when the torque is much less. And of course, below a diesel's idle speed, typically from 600-1,000 rpm, torque and horsepower disappear completely because the engine stops running.
Why are they talking about running diesel at idle speed??? Is there any practical use of running engine at idle speed?

That doesn't happen with E motion electric motors. Their torque curve is flat. Torque doesn't drop off at low rpm, and there's no minimum idle speed. An E motion motor spins as slowly as you want it to and still turns as big a prop as it can at its maximum speed of 1,000 rpm
OK, how big can be the prop? 1m, 1.5m or 2m? How to fit this prop in the boat? (see my calculation posted before). If we are talking about common propeller with its diameter limited by boat's draft, there is absolutely no problem to power it from diesel.

Definitely there are some advantages of electrical propulsion for certain types of boats for certian applications (big displacement boats with considerable housing loads, trawlers and tugs, etc. - those are used for decades already!). But there are a lot of disadvantages also, lower reliability is the biggest issue.

9. ### apex1Guest

Spiv
>>>>As far as Nigel Calder, he is very much PRO diesel <<<<

How can one be named biased when he was building his own yacht to become a test platform for a hybrid system? (And a Bus system too).
Calders results by so far are pretty clear and his statements are the best proven in his (most common) size of sailing yachts.
The "Tesla Roadster" btw was not a good example, car applications are worlds away from marine systems.

Alik
>>>>believe me that 99% of 'boatdreamers' dream of long ocean passages, but end up sitting in marina most of time with short trips to nearest island<<<<

Absolutely true! As is the size of the boat premature dreams create. ALL are dreaming too large to be affordable or sensible.

And why does it happen here on every second thread that the amateur calls the professional biased?

I know the answer, and I´m sure when I say how it is, we have the next fight here with all the premature statements about ones integrity, education and skills.
But I do!

Almost every amateur "boat dreamer" opening a thread here is looking for a confirmation of his dreams and applause, not for a critical scrutinizing or constructive critics or denials. And because they are not willing to leave their point of view and follow good advice they ALL end up having no boat! As long as I contribute to this Forum there was not a single one of these "dream designers"** coming to a point where building (of a then mature design) took place! NOT A SINGLE ONE !!!!
** a pretty bold claim btw. none of them was able to "design" a vessel, not one....

So, do we waste our time here?
Sometimes yes, when the stubborn kid starts fighting with the pro´s.
Usually not, when we can provide enough valid advice in general, to let other readers have a profit of the thread.

Regards
Richard

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### AlikSenior Member

That's a good point, however sometimes these posts are getting lost among boatdreamers' insinuations

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### yipsterdesigner

another new boat dreamer eyeballing propulsion

like to hear you experts opinion on steyr's integrated solution

STARTER MODE
In Starter Mode, the combustion engine can be started with the
electric motor. The conventional starter motor can be eliminated
or will remain redundant.
GENERATOR MODE
In Generator Mode, the extended battery pack is optimised and
charged.
ELECTRIC CRUISE MODE
In Electric Cruise Mode, the boat is driven purely by the electric
motor. The battery pack is constantly monitored on its state of
charge and battery condition. This is brought to the attention
of the driver through the STEYR CONTROL CENTER (SCC).
BOOST MODE
In the lower speed range, depending on dynamic requirements
of the driver and the battery condition, the Boost Mode is used
and the combustion engine is then supported by the massive
torque of the electric motor. The e-motor supports the coupling
and decoupling of the combustion engine. An improved response
of the drive unit occurs through the boost mode.

http://steyr-motors.com/products/pdf/hybrid.pdf
http://www.steyr-motors.com/products/images/ifg.pdf
http://www.steyr-motors.com/products/pdf/ifgpower.pdf

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### AlikSenior Member

2yipster:
This looks promising, becasue they have diesel always available for backup!

If they deliver 7kW from each electrical motor, probably they can run about 6kts on 40' cat in calm weather.

13. ### apex1Guest

Hi Yipster
Mature concept and proven in the scale it was invented for (developed of course).

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### yipsterdesigner

yes yes, thougt it sounded good, thanks for opinions!

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### SpivAncient Mariner

Alik;
"This is good sample of promotional publication!"
Agree, they want to sell their stuff, so one must read with caution, however the fact is that a directly coupled diesel/ prop engine has some drawbacks to a diesel/ electric drive.

Trains are driven by diesel-electric, the AU navy is spending several billions on diesel electric ships.
Why do submarines and tugs have been using them for decades?.... I could go on for half an hour with examples.

Clearly electric motors have an advantage. Now, one must create the electricity, here is where diesel are good: run them at constant rpm and charge batteries. No gearboxes, no prop-shafts.
If you have enough stored electricity you don't need to start your diesel, if not then you start it. To me it's the best outcome.
Yes, more expensive, but I can live with it.
Lastly, you can place the diesel and the motors anywhere on the boat, for instance the motors could be placed out of the boat, even on the side (bridgedeck side in a cat) rather than under the hull, hence no more running aground problem; in most cases, one would be able to pull himself out of a grounding.

Apex1,
"Almost every amateur "boat dreamer" opening a thread here is looking for a confirmation of his dreams and applause, not for a critical scrutinizing or constructive critics or denials."

Not true, I have seen Becaris changing his design and evolving it, and others on other threads too.
I also have owned boats designed by "Professionals" that turned out to be real dogs. The ocean bed is full of sunken boats designed by "Professionals" that have lost their keel and sunk as well as boats built by sub-standards "professional" boat yards.
So the argument can be easily turned around: how many "professional" designers actually go to sea to understand that what they promote doesn't actually work out there?
How many heavy catamaran with low bridgedeck are sold to naive prospective sailors to eventually regret their purchase?

How many flat bottomed monos are still designed to 'beat the rule' and bounce from wave to wave till they develop some fatigue and fail?

On this forum, a real "Professional" should be able to give advice without cutting with a knife.
Bot you and Alik must learn to give advice without cutting if you want to earn the label of "Professional".

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