Need PTO / Design Help

[Sully]

Hi Everyone.  I'm new.  This is my first post.   I'm usually on marine/boat related forums, but the people there really don't know much about designing a custom system. 

Every time I do a Google search or PTOs, flywheels, etc... this forum comes up.  So, I figured this is the place to ask questions.  Please forgive the length of this post.  There is a lot of background information to explain. 

The main point of the post is to ask you guys how you would design a PTO system, given the equipment I have.

Personal Background
I am a charter captain.  My wife and I take people out on boats for vacations.  We are currently building our new charter boat and we're selecting engines and power generation. 

Boat Background
We are building a 45' x 25' fast sailing catamaran. We take a max of 6 people out for a week at a time on it.  I'm going to describe it in non-nautical terms to make it easier for people who aren't into boats.   There are 3 bedrooms and bathrooms.  There is also a professional kitchen doing 3 meals a day as well as drink service.  Of great importance is having the guests be comfortable.  So, we have air conditioners and heaters to run, as well as hot water to make, microwaves to run, guest hair dryers to account for, etc... etc...  HUGE power demands compared to normal boats.  Other than all these house systems, the boat must be kept as light weight as possible.  The less the boat weighs, the better it sails.  For this reason, every single choice made is made considering weight. 

The entire 45' x 25' boat weighs only 5.5 tons.  It can be loaded down to 9 tons with gear, but the less it weights the better it sails and the more people will want to go on it.  (because it's fast)

Engines
I have pre-selected Yanmar 3YM30 engines because they are fuel efficient and light weight.  They are also the gold standard marine auxiliary engine.  I'm open to other engine suggestions, so please feel free to make some.

Power Requirements
I have air conditioners to run as well as electric heaters.  I need the chef (wife) to be able to pop something in the microwave while a couple of small air conditioners are cycling on and off.  That's about a 10KW Generator Head, I'd say.

First Question
Starting from scratch, with everything described so far in this post, how would you design a system to both propel the vessel and generate the power needed, keeping the weight of the designed system at a minimum?

My Thoughts on System Design

1)  Get a couple of Yanmar 3YM30's.  One in each hull.
2)  Attach a 10KW generator head to a *real* PTO at the rear of the engine - no idea how to do this. 
3)  Use the engine with generator head attached to propel the vessel sometimes, other times disengage the propeller and use the same engine to make 10KW of electricity. 
4)  Attach an automotive aftermarket cruise control unit to the mechanical throttle linkage on the fuel injector pump with pickups on the shaft or flywheel.  Gear things up to run the 3YM30 at 1800RPM while turning a 2 pole generator head at 3600RPM.  I should go with 2 pole for weight purposes.  I notice 4 poles are very VERY heavy. 

I was thinking it might be best to separate the engine from the transmission and put a pulley in between the two (with bearings surrounding it) and strap that 10KW generator in that way.  It's a huge load and an RPM sensitive load, so I figured a notched drive belt would be best. 

In that configuration, I could just put the transmission in neutral when I needed to de-couple the propeller and use an electric clutch on the generator head to engage or disengage it. 

If you think my idea stinks, let me know!   

If you thing this idea is workable, where do I get the parts for something like this and how do I make sure not to destroy things with vibration and alignment? 

Thank you very much in advance for any help.  I know you guys know how to put this type of thing together from a lot of reading I've done before I signed up here. 

[Apogee]

Hi Sully,

Welcome to the forum.  I hadn't seen your post until today.

It's an interesting design issue.  One thought that immediately came to mind was why not use electric propulsion motors?  Since the primary motive force is the sails, I assume this is for backup in the event of no wind as well as harbor navigation.  Hence, one would not need huge motors.

You could purchase a pair of 10 or 20KW Yanmar powered pancake generator sets that would be fairly light that would supply all of your power and propulsion needs and allow redundancy to boot without a complicated mechanical coupling system.

http://www.hardydiesel.com/marine-diesel-generators.html

Yes, the propulsion motors might be heavy, but perhaps not any worse than the transmission and possibly v-drive that a mechanical system would require.

Again, welcome!

Steve

[Ronmar]

I think an electric clutch that will support a 10KW generator head(20HP?) is going to be an issue...

[vdubnut62]

I think an electric clutch that will support a 10KW generator head(20HP?) is going to be an issue...

I don't think so, Woodmizer does it on mills diesel and gasoline powered and better than 40hp.
Ron

[squarebob]

$229.00

WARNER ELECTRIC PTO CLUTCH
WARNER #5218-31

NEW OEM REPLACEMENT PARTS

Specifications:

    175 Ft/lb Rating at 3000RPM
    CCW Rotation
    Groove/Flange Type: A/B
    Pulley/Flange OD: 6.000
    ID Bore: 1 1/8"
    Mounting Style: Standard
    REPLACES: ARIENS 92327
    GRAVELY 092327 09266700 00389900
    GREAT DANE GDA10112222
    WOOD MIZER P604
    STENS 255-627

[Sully]

When I didn't get replies right after I posted, I didn't look back here.  Now, I am actually looking to build a microcogen unit.  (I went with outboard engines for weight considerations and no prop drag). 

Will start a new thread about it... and ask for pointers.