Motorised Catamaran

One always wants as much speed as possible, but there is a practical side also. Even if I can do the 80kn I probably won't go there , but if I can get 20 to 30kn it should be fine.

So maybe the question - without redesigning the hulls - should be, can I make 30kn on sailing hulls with outboards...

 

why does a sailing hull NEED rocker, except for quick tacking?

what about planing sailing dinghies?

 

No other main reason as far as I know. May enhance behaviour if the propulsion is done on a lever from a miship position, like a sail for instance. May also allow a better hull entrance angle into the water. Could be many more, it looks nice too


So maybe the question - without redesigning the hulls - should be, can I make 30kn on sailing hulls with outboards...

 

It is quite feasible to fit big outboards on a sailing catamaran and exceed the hull speed.

On my 2008 Year Review pages of my website I include an email from a Lebanese owner who has an open deck version of my 32ft Eclipse sailing catamaran. He reports 14 knots using twin 60hp outboards without the rig.

Over 20 years ago we fitted twin 90hp outboards to one of my 35ft Banshee catamarans. There is a photo on my website of it towing a waterskier at 22 knots. Earlier I had sailed the same boat at 19 knots.

Fuel consumption is a problem though, as is maneuvering slowly with big engines

Richard Woods of Woods Designs

www.sailingcatamarans.com

 

Hi Richard,

I had a brief look at your website, thanks.

If I understand correctly the sailing hulls does offer more speed with larger motors but is rather unefficient due to hull shape and hence is heavy on fuel ?

 

You are right, power boats operating at their design speed will be more efficient. That is because their design speed is known, unlike sailing boats where one has to design for a much greater range of speeds. So a fast power boat will tend to have a higher prismatic coefficient than a sailing boat. Furthermore a powerboat tends to have more buoyancy aft, to help compensate for the inevitable stern squatting.

There are a number of other motorsailor power cats. The Iroquois Chieftain built for a while in the US is one. Another is the Star 43 built by the Multihull Centre. I have motored one at 18 knots (twin 110hp inboards) and it later sailed from the UK to New Zealand via the Roaring 40's

Hope that helps

Richard Woods of Woods Designs

www.sailingcatamarans.com

 

Ok thanks. I think I know what the options are. I am going to put bigger outboards on, say 30-40hp. Operate them at lower rpm to motor ecnomic at hull speed. yet have the extra power when needed.

Seems I'm not going to make the 30kn though.

 

Most probably not Fanie.

But don´t be too sad.
30 nodi on a cat can make a rather uncomfortable ride.

And 18 is a good speed too.

Richard

 

I feel like slitting my wrists now never mind sad. My friend has a small 5m500 boat and het gets 35kn with it. I've been on it too, nothing uncomfortable about it.

Sounds to me like they would be heading back with fish when I haven't even reached the spot yet. And I thought bigger was better. You guys on the forum made me believe this was the boat to go for, yet look at what I'm ending up with, a slow and uncomfortable ride

 

cruel life............

 

Very. And you're supposed to sulk with me

No probs. When they have to leave tonight I'll just stay on the fishing spot, BBQ, catch some more fish bla bla bla... wait for Jaws

 

Here's another motorcat
http://www.youtube.com/watch?v=pMv_8uHepV8
The thing even has a compass

Where do they get these calm waters Must be in the US, you get everything there

 

Jaws?

You know, when there are sharks there are no crocodiles. (at least in Europe)

They have a powerful navy, they make swell all around the world, not at home.....

 

Not here buddy, check OUR crocks

You should have been a politician...

 

We don´t have crocs in Europe dimwit.........