Power Catamaran vs Power Foil vs Walkaround

[AndyJ]

I am designing a craft for inner and outer harbour cruising in all weather conditions for max 10 passengers at 30ft length. They will not need to be super fast, just very stable, secure and efficient.
Have seen some exciting stuff on dual propeller foils recently but am concerned with drawbacks for lower speed areas and debris danger.

If you have any preference based on experience, I will be very grateful to hear!

 

[TANSL]

... stable, safe .... seem to point towards a catamaran.
Efficient: describe to the best of your ability what efficiency you are referring to.
At what maximum speed are you thinking?

 

[AndyJ]

... stable, safe .... seem to point towards a catamaran.
Efficient: describe to the best of your ability what efficiency you are referring to.
At what maximum speed are you thinking?

Thanks for the comment. For efficiency, I am looking for power output to weight as I am working with an electric motor and am hoping to get maximum time I can. Which leads me to,
Max speed 20 knots. Would be more often operating under 15. Thanks

 

[Mr Efficiency]

Sounds ambitious, 30 feet is smallish, and 15 knots requires a bit of power. What is the distance to be covered between recharging the batteries ?

 

[AndyJ]

W

Sounds ambitious, 30 feet is smallish, and 15 knots requires a bit of power. What is the distance to be covered between recharging the batteries ?

Was hoping for a little over 30nm/60km before recharge. The power will definitely be much less than the 15 knots usually. Would say (based on harbour restrictions) that it would be more often under 10 knots. Thanks

 

[TANSL]

Does that mean that you should recharge the batteries every 2-3 hours?.

 

[AndyJ]

Does that mean that you should recharge the batteries every 2-3 hours?.

Was hoping for something that lasted longer. Around 5 hour mark. With solar and possible harbour docking quick charges. Still tinkering. Thanks

 

[TANSL]

Think that, perhaps, the boat will be more time stopped recharging the batteries that sailing, which does not make sense.

 

[AndyJ]

Would you say that is due to intended power output to required distance? I am interested on your take just so I can reset my design/expectations. Thanks

 

[TANSL]

It is not due to power output (that I do not know) but because you want to travel "30nm / 60km before recharge". That is, at a speed of 10 knots you take 3 hours to travel 30nm, after which you have to recharge batteries. Batteries take a long time to recharge (how long will it take a harbor docking quick charges?), so you must be stopped for all the time necessary to recharge them.
I do not know if I'm doing something wrong. What do you think?

 

[AndyJ]

That sounds embarrassingly (for me) right. Will look at battery capacity and weight with that. I think smaller catamaran is the design for this but the other elements I will need to more properly consider. Thanks for the thoughts!

 

[xellz]

Do i understand right, you're thinking about fully electric boat? If yes, i'm in same boat, yes, kind of Currently planning on building 30ft cat with electric propulsion. I bought plans for Jazz 30 by Woods Design, which is wide beam 30ft power cat. Quite light and more or less efficient. From info i could gather, even this cat will require quite a bit of power to move above 10knot mark. Rough estimation would be at 6-7knots something in the 4-6kw/h, 12 knots 18-22kw/h, 16knots 28-30kw/h. With 10 passengers it might drop even lower. To get noticeably better efficiency you would have to go for custom design and use lighter, stronger materials, but price of course will dramatically increase.

 

[AndyJ]

Thanks so much for the working sums - much appreciated. I was considering powering with twin water jets but am not sure if they can be run on electric or what power might be necessary for that. Just wanted something highly manoeuvrable but still lasting in terms of charge. Will check out Woods too. Thanks!

 

[TANSL]

@fallguy, will not you say it seriously, or will you?

 

[TANSL]

Maybe I've been a little rough, I'm sorry. I mean that, without knowing anything else about the OP ship, without knowing its SOR, it is not possible to recommend any specific type of ship. Personally I have the impression that Richard Woods designs, which are very good, will not work in this case.