Newbie Trawler Question???

Might have an answer
My boat a fast planing type @ 1000 rpm ( out of 36-3800) does around 7-8 knots consuption around 4 LHour each engine so 8 ltrs for 7-8 miles?
There you are
I often tuna fish 6 knot 6 miles out for 6 hours
Even less just above tick over , tick over is 4 knots
Its a Sunseeker approx 37 ft about 8-9 tonnes , has a sharp / fine entry ,deep V no drag from shafts rudder , p bracket
Duoprop ( efficient ? ) streamline outdrives ,
Min surface area in the water, compared to a trawler = less drag
I think there is something in these type of boats " poolting " and using v little fuel
It's not what they are primarily designed for , more an accidental and pleasant positive side effect .
A pair of 3.7 ltr diesels @ these speeds the supercharger ( 1700 rpm ) and the turbo ( 2650 rpm) are not working
 
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Economy

The last post I have got to challenge it's accepted that displacement hulls are more efficient at low speeds
Impuls is 60 ft x 13'6" weights around 25 tones 200 hp, top speed of around 10 kts cruises at sea 6-8 kts at a max of 3 gph in my book thats somthing over 2.5 mpg I'd challenge any planning hull to come any where close and comfort is far far better in lumpy waters just don't have to be in a hurry!
The answer is as already stated in the wash generated that's where all the power / fuel is going so light wash equals low fuel consumption so will a planing hull make a big wSh at 8 knots

So economy is in a full displacement hull anything else needs huge amounts of power
 
Impulse said:
The last post I have got to challenge it's accepted that displacement hulls are more efficient at low speeds
Impuls is 60 ft x 13'6" weights around 25 tones 200 hp, top speed of around 10 kts cruises at sea 6-8 kts at a max of 3 gph in my book thats somthing over 2.5 mpg I'd challenge any planning hull to come any where close
Click to expand...
Well you've only got to scroll further up the thread to see my post in which I said that my Ferretti 53 (55' x 15' 4" weighing 24t with 1320hp) does 3.5nmpg at 7.7kts. Sorry and I'll say it again but it is a fallacy to believe that a heavy displacement trawler yacht can achieve better economy at displacement speeds simply because it is designed to operate in that mode. I'm not arguing about comfort; I fully accept that a full displacement hull is more comfortable than a planing hull at displacement speed but this thread is about economy
 
LittleShip said:
because they run relatively small engines and I'm talking about true trawlers

Last year I did 1300 miles and averaged 1 ltr per mile.... name any compatible sized planing boat that will compete with those figures.

Tom
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MBM test July 2012 Bavaria 31 with twin engines 1000rpm 6.1kts 4.7nmpg. I'm happy to trawl thru more old mag reports if you want but I'm off to my own boat tomorrow and I haven't really got time
The size of the engines has little or no bearing on fuel economy except insofar as they add weight to the boat. It's a generalisation but all diesel engines of the same basic design have approximately the same specific fuel consumption in terms of grams per kWhr. What counts is how much power is required to push the boat through the water and that power depends mostly on weight and hydrodynamic drag
 
I contemplated the idea of buying a displacement / semi displacement boat before settling on the Princess P50 planing boat. I was on a bit of downer, fuel prices, would there be anyone to buy it off me come re-sale and so on.

Having used it a bit now I can happily confirm that at tick over the thing runs on thin air whilst still pushing 6 or 7 knots, obviously more with a fair tide. We have made a number of journeys just pottering along when time and weather permits. Indeed a recent cruise back from Cowes to Portsmouth saw us shadowing a Nordhaven and we matched speed knot for knot. I actually arrived a bit sooner because I used the inner channel as we came round Gilkicker, he wasn't so confident of the tides (it's our home Port so we know it to within an inch or two!).

Of course the advantage we have is that when time is short or the weather not so good we can press on at up to 30 knots. So the best of both worlds. Some might argue that in a force 8 the displacement boat would fare marginally better (you had better be holding on to something) but of course we wouldn't be out there having out run the weather front or not set off in the first place. 2 or 3 hour weather is much easier to predict than 12 hour weather.

So if you want them to be fast planing boats can be very frugal.

Henry :)
 
Galaxy said:
Hello all,

Wondering if anyone here can enlighten me a bit about the Trawler fuel economy compared to other MoBos. Are Trawlers really the best on fuel consumption? Are they good on fuel because they move slower? If you buy another type boat and cruise it slowly will you get the same fuel consumption as the Trawler, or not at all because of the design or something?

Are there any other spacious (traveling with kids) long range seaworthy boats that will also give very good fuel consumption?

Thanks for your help. Trying to sort this all out before I make my big move :)
Click to expand...

Hey
You will by now have read two oposite opinions. Those who favour planning boats, and those he favour displacement boats.
Fact is that going slow is generally more economic, and if you go slow enough it makes not difference whether the boat is of displacement type or planning type.
Trawlers, trylestyle or trawler alikes are not more economic than other boats - I would even claim them to be rather thirsty. Most trawlers are a like a 4x4 car - it has more power than nescessary - it has often twin engines (sry Littleship) and spent more fuel than nescessary. Not sure whether boats like Nordhavn, Selene and others want to be compared with boats like Grand banks, Flemmings but any of them can be run slow and with low fuel consumption.

There are many good reasons for buying a Trawler, but fuel economy alone is not one of them....

:confused:
 
Lets just agree to disagree :)

There are trawlers and then there are trawlers the difference being some are only look a likes and in real terms they are semi displacement at best.

Nordhvens, (old style) Grand banks and a few others are true displacement boats which run low Hp engines most with singles although some have small twins..... Benni Swifts, Traders and the like normally run large twins and are not displacement in the real term of the word.

In short if it has a top speed of more than 10knts its a lookalike :rolleyes:

I'm not posting anymore on this thread we are all entitled to our opinions, I know which I think is the most efficient and have stated so.

Tom
 
LittleShip said:
Lets just agree to disagree :)

There are trawlers and then there are trawlers the difference being some are only look a likes and in real terms they are semi displacement at best.

Nordhvens, (old style) Grand banks and a few others are true displacement boats which run low Hp engines most with singles although some have small twins..... Benni Swifts, Traders and the like normally run large twins and are not displacement in the real term of the word.

In short if it has a top speed of more than 10knts its a lookalike :rolleyes:

I'm not posting anymore on this thread we are all entitled to our opinions, I know which I think is the most efficient and have stated so.

Tom
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Hello,

Well I fully agree with you, but One thing is 'LittleShip' and the other a Grand Banks 42 with twin 420 hp cats - and for many this is still a real Trawler.

And honestly, if the 42 wasnt so thirsty, I would like one myself :o
 
Hi All,
Don't forget displacement hulls roll like pigs. You will need stabilizers (£££££...). Semi displacement might suit you better, but eat fuel above 8 kts. Problem with cats is that they are very heavy (two hulls) and very expensive (50% more)= very little payload.
 
LittleShip said:
Lets just agree to disagree :)

There are trawlers and then there are trawlers the difference being some are only look a likes and in real terms they are semi displacement at best.

Nordhvens, (old style) Grand banks and a few others are true displacement boats which run low Hp engines most with singles although some have small twins..... Benni Swifts, Traders and the like normally run large twins and are not displacement in the real term of the word.

In short if it has a top speed of more than 10knts its a lookalike :rolleyes:

I'm not posting anymore on this thread we are all entitled to our opinions, I know which I think is the most efficient and have stated so.

Tom
Click to expand...

Sorry Tom,

But your boat is semi-displacement, I was fairly sure as have been a fan of GB for many years.

Just checked with GB in the USA and they have confirmed it.


REPLY
We never built a displacement boat. Semi Displacement.

TW

Sincerely,

Tucker West
Grand Banks Yachts
North American Sales Manager
206.352.0118 ext 130



-----Original Message-----
From: @@@@@@@@@@@@@@@@
Sent: Tuesday, August 21, 2012 11:25 AM
To: Tucker West
Cc:@@@@@@@@@@@@
Subject: Displacement


Hi Tucker,

Sorry to trouble you, but I am hoping that you or someone in GB can settle a long standing argument.

My question is, did GB at any time make a true displacement hull, in particlar the old wooden GB32?

Hoping that you can hekp.

Kind Regards
JimG
 
jimg said:
Sorry Tom,

But your boat is semi-displacement, I was fairly sure as have been a fan of GB for many years.

Just checked with GB in the USA and they have confirmed it.


REPLY
We never built a displacement boat. Semi Displacement.

TW

Sincerely,

Tucker West
Grand Banks Yachts
North American Sales Manager
206.352.0118 ext 130
Click to expand...


this thread suddenly just got very interesting!
 
jimg said:
Sorry Tom,

But your boat is semi-displacement, I was fairly sure as have been a fan of GB for many years.

Just checked with GB in the USA and they have confirmed it.
Click to expand...

Oooh I know I said I wouldn't but............ she is hard chine and cant get above 9knts, it's designed as a displacement boat :p :)

I will admit that she has quite a flat bottom once past half way but as for semi displacement......... come on? This is the best picture of the bottom does it look semi to you/anybody ??

I don't know why I'm bothering.


Tom
 
LittleShip said:
Oooh I know I said I wouldn't but............ she is hard chine and cant get above 9knts, it's designed as a displacement boat :p :)

I will admit that she has quite a flat bottom once past half way but as for semi displacement......... come on? This is the best picture of the bottom does it look semi to you/anybody ??

I don't know why I'm bothering.


Tom
Click to expand...

That's defiantly a planning hull if ever I saw one...... And I see it's fitted with the latest design of IPS drives..... Cunningly disguised as oil drums!!

:D
 
LittleShip said:
Oooh I know I said I wouldn't but............ she is hard chine and cant get above 9knts, it's designed as a displacement boat :p :)

I will admit that she has quite a flat bottom once past half way but as for semi displacement......... come on? This is the best picture of the bottom does it look semi to you/anybody ??

I don't know why I'm bothering.


Tom
Click to expand...

She cannot get above 9 knots because she has tiddly engines! :D:D

You may find this link interesting as it is all the line drawings for your boat:- http://www.grandbanks.com/images/discovery/ownership/retiredmodels/32se/factorySpecs.zip
 
LittleShip said:
she is hard chine and cant get above 9knts, it's designed as a displacement boat
Click to expand...
Hang on LS, you're mentioning hard chine as if that would belong to displacement hulls, but it's actually the opposite.
Even if there are indeed some steel fishing trawlers designed with hard chines (for various reasons), THE pure displacement hull by definition has round chines - just look at sailboats.

Re. your boat, based on that pic I'd call it more a SD than a full D hull, though it's true that it has a less "planing-alike" shape towards the stern, if compared to most modern SD boats.
Trouble is, if D is white and P is black, SD is grey. And grey has an endless number of shades... :)
 
Hi Piers,
I'm on a 60' steel barge at the moment, but I'm planning a 'round the med trip, that is until I calculated fuel con. This is my reckoning.. 2hrs morning, two hrs afternoon. 4hrs at 7g/h 300hp=120 day, call it £1000 wk fuel. (10m planning hull, 5ton?) plus mooring fees etc. Maybe displacement is the only answer. 8 kts is the magic number for any boat under 60'.
 
rustybarge said:
Hi Piers,
I'm on a 60' steel barge at the moment, but I'm planning a 'round the med trip, that is until I calculated fuel con. This is my reckoning.. 2hrs morning, two hrs afternoon. 4hrs at 7g/h 300hp=120 day, call it £1000 wk fuel. (10m planning hull, 5ton?) plus mooring fees etc. Maybe displacement is the only answer. 8 kts is the magic number for any boat under 60'.
Click to expand...

Given Play d'eau's max theoretical hull speed of 9.55kts, the moment I start to go much above 8.5kts you just know the fuel is starting to flow. At 8, or even 7 at times, fuel is sipped at such a slow rate, I have only had to re-fuel 19 times since new in 2003!
 
Piers said:
I cruise at 8kts in my Fleming 55 and an getting around 1.8nm to the gallon. Far, far better than my previous planing boats.
Click to expand...

Hey,

Just a matter of curiosity - do you sometimes cruise on one engine ??

I know my own boat is a lot cheaper on one engine, but even then I very seldom use only one engine.
 
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