Tug compared to trawler as cruisers

[Wckoek]

Originally Posted by Pelagic

The important issue on power yachts is really the underwater design and performance curves

You can have two identical looking tug-trawler-yachts in every respect above the waterline but very different shape and lines underwater which can make one far superior in a seaway and more fuel efficient with less wake for a given HPand speed than the other.

Of topic really, I wondered if you have a view on which of the trawler type monohull displacement hull are fuel efficient? I mean non production designs and plans one can have it build by a yard.
LWL hull like those designed by Dashew is of course more efficient but they roll so terribly without stabilization and have much less carrying capacity for their given length.

[ZULU40]

Originally Posted by Pelagic

The important issue on power yachts is really the underwater design and performance curves

You can have two identical looking tug-trawler-yachts in every respect above the waterline but very different shape and lines underwater which can make one far superior in a seaway and more fuel efficient with less wake for a given HPand speed than the other.

that would be so if it werent for the featureset one would find visiting boats at the dock, or perhaps on video. The Boatest.com video version of the same boat gets 134k views. For their footage these boats are feature packed

https://www.youtube.com/watch?v=8Bu1Lgiup7M

[Pelagic]

Wckoek.....That is quite a complicated topic as you need to understand that performance is not just fuel efficiency.

You measure different aspects in a variety of load conditions wave height and wave period against a chosen speed to properly assess the design for the type of cruising you will be doing and the shaft HP needed.

It is a balance of priorities from load capacity, roll conditions, stern immersion without drag and at optimum shaft angle that determines the hull form

This explains a little
http://www.nordhavn.com/models/fundmentals/numbers/

[boatpoker]

When asked, we just tell folks our Benford 38 Fantail is a "trawler" for simplicity. In reality we just think it's a boat.

[Pelagic]

If fuel efficiency for a power yacht was the biggest priority I would look at Malcolm Tennant designs.

He was the best!
Here is one example

http://www.tennantdesign.co.nz/index...e=globetrotter

[Wckoek]

Originally Posted by Pelagic

If fuel efficiency for a power yacht was the biggest priority I would look at Malcolm Tennant designs.

He was the best!
Here is one example

Malcolm Tennant Multihull Design Ltd - Globetrotter

I have seen a similar concept. Ghost
But I feel that it is small in interior space for a 50 feet boat, and for 5 tonne, the pay load probably wasn't enough for extended cruising, something like 1 tonne including fuel and water?
Malcolm Tennent's design would be more practical, but not as long a range as McGowan's I see.

In my country diesel only cost $2 USD per gallon, unless you travel like more than 10,000-15,000 miles per year it is far cheaper than the cost of maintaining sails and rigging per year and sailboats need an engine running too.

The problem with powered cruiser is always range, I don't see that much designs that can run more than say 3,500 miles on a single tank, unless it's those ultra expensive behemoth that carries 1,500 to 2,000 gallons of fuel and very expensive to run.

[rwidman]

Originally Posted by sv Grateful

If you are asking about using a conversion of an actual working tug as a yacht, I'd say that unless our have a real thing for tugs, you'd be making a mistake in choosing one as a cruiser.
..

For fifteen years or more there has been a tug being converted to a cruiser docked along the ICW north of Daytona Beach, FL. It was never finished and never moved.

Apparently the owner passed away and the family didn't know what to do with it.

This spring it began leaking fuel and partially sank. The government had to come in with a crane and barge and get rid of it.

Trying to convert a tugboat to a cruiser is a very bad idea. It would cost more than buying a new cruiser and you could hop aboard and cruise right now.

[Wckoek]

Originally Posted by rwidman

For fifteen years or more there has been a tug being converted to a cruiser docked along the ICW north of Daytona Beach, FL. It was never finished and never moved.

Apparently the owner passed away and the family didn't know what to do with it.

This spring it began leaking fuel and partially sank. The government had to come in with a crane and barge and get rid of it.

Trying to convert a tugboat to a cruiser is a very bad idea. It would cost more than buying a new cruiser and you could hop aboard and cruise right now.

Whittles Publishing - Books
There is this book about the delivery of 2 tugs, I can't imagine how much the fuel alone would cost.

[Cadence]

Originally Posted by boatpoker

When asked, we just tell folks our Benford 38 Fantail is a "trawler" for simplicity. In reality we just think it's a boat.

A good looking boat. With the fantail, put a bollard just behind the cabin and tell them she's a tug.

[ZULU40]

Originally Posted by Wckoek

I have seen a similar concept. Ghost
But I feel that it is small in interior space for a 50 feet boat, and for 5 tonne, the pay load probably wasn't enough for extended cruising, something like 1 tonne including fuel and water?
Malcolm Tennent's design would be more practical, but not as long a range as McGowan's I see.

In my country diesel only cost $2 USD per gallon, unless you travel like more than 10,000-15,000 miles per year it is far cheaper than the cost of maintaining sails and rigging per year and sailboats need an engine running too.

The problem with powered cruiser is always range, I don't see that much designs that can run more than say 3,500 miles on a single tank, unless it's those ultra expensive behemoth that carries 1,500 to 2,000 gallons of fuel and very expensive to run.

Displacement multihulls are the next big thing

The whole purpose of the exercise is to considerably reduce fuel burn vastly increasing range by cruising at hull speed which is how trawlers operate. This also means less investment in engines and of course there wouldn't be a rig deeply minimising costs and upkeep.

Whether trimaran or catamaran they are super long range. However I suspect ft for ft cats will offer more usable space as the inherently narrow hulls will not affect the bridge deck but still provide for services and utility space. Tris on the other hand will be much narrower beam than sailing versions with the possibility of collapsing into a monohull berth further reducing costs at destination.

[Wckoek]

I don't know much about displacement multihull, you mean crafts like SWATH?
The regular cat and trimarans didn't carry load too well, of course there are new type of Chinese warship, catamaran with bulbous bow, but I didn't see anything like that for leisure craft and yacht.

[ZULU40]

Originally Posted by Wckoek

I don't know much about displacement multihull, you mean crafts like SWATH?
The regular cat and trimarans didn't carry load too well, of course there are new type of Chinese warship, catamaran with bulbous bow, but I didn't see anything like that for leisure craft and yacht.

These are boats with very narrow hulls meant to cruise at their hull speed, roughly the root of the waterline length x 1.34. These hulls are in the area of 13:1 to 15:1 L:B instead of the existing 8:1 for presently popular multihulls. Such a vessel as a mono would be very uncomfortable but can be afforded with either tris or cats.

I cant provide a measurement or rule for displacement at this time its pretty much trial and error, in some cases perhaps trial by ordeal. But my feeling is that the equipment reductions make up the best part of the reduced weight sought.

Swath boats in my view lack the utility of shallow draught, in situations where for the cruising sailor the intersect between land and sea is really the most interesting, but its a space worth watching.

[Stumble]

How long is a piece of string? I mean that seriously, if we are going to discuss the ideal long range boat then we first need to define what that means. What are the constraints you want to model around?

1) Maximum length?
2) Minimum beam?
3) Sq foot of living
4) Roll period/magnitude underway and at anchor
5) Fuel efficiency
6) maximum range
7) sea keeping ability
8) Cost to keep it in a slip
9) Cost to build
10) Max displacement

The way in which you weight these against each other, as well as a few more factors, will heavily influence the type of vessel you wind up with.

There really isn't an ideal here, just a lot of competing factors that all need to be balanced against each other to design a boat for the end user. And because many of these factors work opposite to each other there will always have to be a balancing act in the equation.

[Wckoek]

Originally Posted by ZULU40

These are boats with very narrow hulls meant to cruise at their hull speed, roughly the root of the waterline length x 1.34. These hulls are in the area of 13:1 to 15:1 L:B instead of the existing 8:1 for presently popular multihulls. Such a vessel as a mono would be very uncomfortable but can be afforded with either tris or cats.

I cant provide a measurement or rule for displacement at this time its pretty much trial and error, in some cases perhaps trial by ordeal. But my feeling is that the equipment reductions make up the best part of the reduced weight sought.

Swath boats in my view lack the utility of shallow draught, in situations where for the cruising sailor the intersect between land and sea is really the most interesting, but its a space worth watching.

I have not seen designs or proposals of these type, does Adastra counts as one?

Agree with SWATH, and the only the stability yacht proposal I read wasn't that impressive, and even more complicated to build and maintain.

Still monohull trawler, as we earlier mention the cruising long range type is pretty hard to beat for fuel economy, space, carrying load and weight. Range regardless is still a tough nut to crack even with the advancement of fuel economy as it is difficult to find a balance between carrying capacity of fuel, weight, power, stability and a lot of things.

I have seen a tunnel semi-planing monohull capable of 7mpg, but it wasn't a bluewater long range design.

[Wckoek]

Originally Posted by Stumble

How long is a piece of string? I mean that seriously, if we are going to discuss the ideal long range boat then we first need to define what that means. What are the constraints you want to model around?

1) Maximum length?
2) Minimum beam?
3) Sq foot of living
4) Roll period/magnitude underway and at anchor
5) Fuel efficiency
6) maximum range
7) sea keeping ability
8) Cost to keep it in a slip
9) Cost to build
10) Max displacement

The way in which you weight these against each other, as well as a few more factors, will heavily influence the type of vessel you wind up with.

There really isn't an ideal here, just a lot of competing factors that all need to be balanced against each other to design a boat for the end user. And because many of these factors work opposite to each other there will always have to be a balancing act in the equation.

Say for a owner operated yacht, we are limited to under 24m or 72 feet at the waterline and under 80 tonnes in displacement, regulation wise.
Beam and sq ft of living open, but ideally 3 cabin plus 2 berth for crew, a berth for watch keeping at pilot house.
Fin stabilizer is a must.
Maximum range above 5000 nautical miles.
The few boat I know that fit most of these criteria is Watson 60, it cost about 2 to 3 million to build I remember.