New range of Bob Oram designed powercats

[Alan M.]

A high quality builder has recently launched the first of a new range of highly efficient yet luxurious power cruiser / gamefishing boats. Their website has some impressive videos:

http://www.alluramarine.com.au/home

[masalai]

Nice alan, - - and bob denied any such projects - or I probably did not ask the right question.... Nice stuff though... My preference is around 12 to 15 knots and 1 litre per mile (gotta beat Robin Chamberlins' "Icecat challenge" in a 12 m version - - no flybridge)

[Willallison]

Runs very nicely doesn't it - though from my quick glance I'm not too keen on the layout...any boat that can't comfortably seat and dine all it's crew fall's short in my books.

I had a good look at the Chamberlain cat when it completed it's trip down here to Tassie - fab boat and I agree... powercats are probably a glimpse into the not too distant future for those who still want to travel quickly....

[masalai]

Will was that "Foreign Affair"? - Robin has apparently designed another (12M) for John, who said he may start the build around Xmas...

Your problem is easily fixed remove one or more cabins & one of the two toilets - saves on weight.... and I do not intend to be in the charter business, so the rest can go buy their own....

[Willallison]

Not sure what her name was (a luckier man would say that was the story of his life ) but it was the one that they wrote a couple of articles about...you know - how little fuel can we use on a trip to Tassie....

No argument the arrangement problem can be fixed. But regardless of the number of cabins, the seating arrangement looks pretty lacking to me.

I might add that this may be no fault of the designer... what the customer wants...
And BO has a good rep

[masalai]

And a nice guy... By the way you are talking, Yes Definately "Foreign Affair" and was reported in New Caledonia in the last edition of "The Coastal Passage" http://www.thecoastalpassage.com/ Foreign Affair is a Robin Chamberlin design... The ones at "Allura Marine are Bob Oram http://www.alluramarine.com.au/home....

[waikikin]

Looks nice, a vast improvement to my mind on the typical fuel guzzling flybridge style gameboat/cruiser. Good on 'em I say. Regards to all from Jeff.

[charmc]

Originally Posted by waikikin

a vast improvement to my mind on the typical fuel guzzling flybridge style gameboat/cruiser. Good on 'em I say. Regards to all from Jeff.

Agreed. Power cats are becoming more common here as small (under 10m) cruisers and fishing boats. Good speed with half the power and fuel, good ride, less rolling at rest or low speeds .. a lot to like.

[Nojjan]

55ft = 11500kg (dry) !!!, I am not convinced, I wonder what a set of calibrated scales would say? If it is correct then I am truly impressed.

I wonder, the top speed or calculated range is that with full displacement to start or maybe assuming light ship condition...

The main reason for cats being considered efficient is that low cruising speed. A monohull 55ft at 11500 kg will have very close to the same resistance curve for that WOT speed...and monohull will be more efficient at higher speeds.

My experience is that cats are almost always heavier than monohulls unless super expensive materials are used...on the other hand that can be done also for the mono...

...not a believer yet / Nojjan

[masalai]

Nojjan, What are you building boats of ?Lead?, Bobs weights are quite conservative and easily attainable by the amateur builder using standard composite techniques, some are even lighter as you must be well aware cats suffer in performance if weighted down with extra personal "crap".

[Nojjan]

Yes, I build boats of lead, is that not a good material...?

Figuring roughly 11500 lightship + 2000 fuel + 800 water + 5% "crap" = 15000 kg + crew.

The lightest 55/56ft monohull I have scale weighted was 18000kg loaded. Considering that cats tend to be heavier for the same length I still have my doubts but if you say it's true it probably is.

[masalai]

Get your passport and visas sorted and lob in to Brisbane & I can introduce you to 3 local designers who will amaze and convince you otherwise....

[Alan M.]

Originally Posted by Nojjan

55ft = 11500kg (dry) !!!, I am not convinced, I wonder what a set of calibrated scales would say? If it is correct then I am truly impressed.

I wonder, the top speed or calculated range is that with full displacement to start or maybe assuming light ship condition...

The main reason for cats being considered efficient is that low cruising speed. A monohull 55ft at 11500 kg will have very close to the same resistance curve for that WOT speed...and monohull will be more efficient at higher speeds.

My experience is that cats are almost always heavier than monohulls unless super expensive materials are used...on the other hand that can be done also for the mono...

...not a believer yet / Nojjan

What an amazing post. Cats are almost always heavier than monohulls???? The reason cats are efficient is because they are slow????

Just incredible.

Around here, ALL the fast passenger ferries are cats.

Bob Oram doesn't tell lies. If he says the boat weighs 11500kg, the boat weighs 11500kg.

It isn't built from exotic materials. But the materials it is made from have been used properly. Solid glass layups with CSM are just heavy rubbish, but many builders of "high end" boats still persist with it.

I don't know of any comparable monohull that could achieve anywhere near 30 knots with that size engines.

BTW Bob has a design for a 60' sailing cat that weighs 11200kg fully loaded.

[Nojjan]

Maybe you guys are getting confused by my statement "...almost always heavier than monohulls". I mean of the same Loa, considering that the cat has more acomodation space it is rather natural. Commercial vessels often optimize their mission, speed, load, range etc. which gives a better chance of using the potential economics in a cat, not forgetting the smooth ride up to a certain sea state for the passengers. Sailing vessels are lighter in general because they are submitted to lower loads, has less interior space and usually also contain less stuff like smaller engine(s) (please compare other sailing boats to power boats of same size and you will see what I am talking about). I don't know of any 55ft monohull that is capable at 30 knots with those engines either beacause I don't know of any that is so light (as I said before), my claim is based on a quick calculation.

I sense that I have upset you guys and that is not my intention, please forgive me.

[masalai]

first part NO, second part - sometimes, depending on size, third part so are cats - or should be. - - Smooth ride in some seas not others (see across Bass Strait ferries - Melbourne to Tasmania)

Monos are NOT lighter because they NEED KEELS to stay upright and prevent a capsize. - - With respect to power boats - recreational vessels usually need HUGE engines to get to and maintain 15 to 25 knots and exponentially larger for higher speeds (also applies to many commercial fishing monohulls as well as for "gamefishing") Small engined monohulls I have only seen on local bareboat power vessels as they are (in Australia) required to be speed restricted - around 10 knots... Here we have lots of "marina berth" size powercats with twin 200 hp and up engines capable of 50 knots (30 knot cruise) but not long range (2000 plus N Miles) which is what the specialised recent trend is doing 15 knot cruise 2000 plus mile range and 20 to 25 knot short burst max speed.

Lots of different design options and choices. no longer can they be "grouped as cats"... Read an article by Malcolm Tennant in the USA edition of Multihulls Magazine, I think August/September 2002.... Also lots of stuff on here....

Best wishes and enjoy your reading and research...