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Multi-hull ships (vessels, craft, boats) comprise a great variety of types, sizes and applications. At the present time, the main interests in shipbuilding and shipping industries of multi-hull vessels are focused on engine-powered ships. Today thousands catamarans are used as racing, sailing, tourist, fishing boats. Hundreds (about 70%) of fast passenger and car-passenger ferries are catamarans. About 300 semi-submersible drilling and auxiliary platforms are exploited
in the sea. Some ships with outriggers are built, including the experimental ship
“Triton” (UK) and the first and second sister-ships of the series of Littoral Combat Ships, USA . About 70 SWA ships of various purposes and displacement are built.
According to 'monograph' the entire breed of multi hull ships can be classed by the number of
hulls and by the mutual arrangement of the hulls which
includes the shapes and sizes of the hulls.
A very specific and important sub-group of multihulls is Small Waterplane Area
(SWA) multihulls, a twin-hull version if this subgroup is commonly known as
SWATH = Small Waterplane Area Twin Hull.
Fig.1
and
Fig.2
Joint classification is seen in Fig.1 and Fig.2 showing some arrangements of hulls for conventional and SWA
multihulls, both reproduced from.
Numbers in Fig.1 stand for: 1 – catamaran: two identical conventional hulls, 2 – the same with non-symmetric hulls, 3 –
trimaran, with three identical symmetric hulls, 4 – the same with flat outer boards of side hulls, 5 – catamaran with shifted hulls, 6 – proa or a vessel with bigger main hull and smaller side added hull, an outrigger, 7 – ship with
outriggers which is a triple-hull ship with its side hulls being significantly smaller than the central hull. Fig.2 shows a waterplane sections of SWA vessels, here the numbers stand for: 1 – twin-hull SWA ship, each hull consists from the under-water volume ("gondola" or "under-water volume" or "pontoon") and one long strut; the type was named as the first built ship:
"duplus"; 2 – twin-hull SWA ship with two short struts at each hull, the type was named as
"trisec", 3 – triple-hull SWA ship with identical hulls, was named as
"tricore"; 4 – SWA ship with (two) outriggers, 5 – a vessel with a conventional central hull and SWA outriggers, 6 - a monohull SWA vessel with foils. Each type of multi-hulls differs from the other and from the
monohulls. For example, a catamaran has a biggest transverse stability of all ships of the same displacement. A duplus has biggest transverse stability from all SWA ship types. A trisec can have smallest area of water-plane of all
multihulls and monohulls of the same displacement. A
catamaran with longitudinally shifted hulls and any triple-hulled ships can ensure the most favorable interaction of wave systems are generated by the vessel at speed. A ship with
outrigger(s) (proa or trimaran in Western sense) can have smallest relative mass of hull structures. Engine-powered multihull terms. Sometimes, the term “catamaran” is applied to any ship or boat, which consists from two hulls. But a deeper understanding needs for more detail terminology.
The other twin-hull ships are
proa, duplus, trisec. The history of commercial catamarans began in the 17th century in England. Some separate attempts of steam-powered catamaran application were carried out up by the middle of the 20th century. But such ships need for better materials and more developed hydrodynamic for successful application. The second half of the 20th century was the time of wide and in the main successful application of various catamarans on the base of developed science. Sometimes the term “trimaran” is used for any triple-hull ships or boats. But a deeper understanding of ship type characteristics needs for more detailed definition the types. Than hereafter the term “trimaran” is used only for a ship or boat from three identical hulls of traditional shape (the definition is usually for
Russian science since 70-th years.) The other triple-hull ships or boats are outrigger ship,
tricore. The main own specificity of a trimaran is biggest from all possible interaction of wave systems are generated by hulls at speed. The interaction can be favorable and not favorable ones, in dependence from relative arrangement of hulls and relative
speed. Today the built trimarans are absent, only there are some results of model tests and corresponded estimation of the power of the full-scale ships; the calculations show big enough possible advantages at a defined band of the relative speeds. A new type of super-fast vessel, the “wave-piercing” trimaran,
WPT, is known as air-born unloaded (up to 25% of
displacement)vessel, which can ensure twice bigger, as achieved today, speeds with a permissible relative power. Proa is a ship or boat from one hull and one outrigger (small side hull).
The engine in the main hull is more convenient, evidently, but not obligatory one. A ship with one main hull of converntional shape and two side small hulls (outriggers) is named as "outrigger ship". The same type is named as "trimaran" in English language publications. SWA ship Each hull, which has smaller beam at the level of design water-plane, than below it, can be named as a hull with decreased - or small - water-plane area. But more often the term “small water-plane area hull” means a hull from the under-water volume (“gondola”) and one or more thin
strut(s), which connect the gondola with the above-water platform. Any ship or boat, which consists from hulls of small water-plane area, can be named as “small water-plane area ship” or “SWA ship”. Any twin-hull SWA ship is named as “SWATH”. A triple-hull SWA ship is named as “tricore” –today without dependence from the number of struts on each gondola. A ship or
boat from two hulls with one long strut on each hull was named as “duplus” (by the name of the first drilling ship of the type).Today the duplus are most spread type of built SWA
ships. The term “trisec” is used for a twin-hull SWA ship with two struts on each gondola. A trisec can have a minimal area of water-plane, therefore, minimal motions in waves and higher effectiveness of motion control.
An outrigger ship can have the main hull, and/or outriggers of small water-plane area. Mutual arrangerment of hulls. The hulls are connected by the above-water structure, which is named as “platform” or “above-water bridge”. The structure can be watertight partially or as a whole, or can consist of separate frames. The distance between the hulls is named as “transverse clearance” and can be measured by various methods: between center planes of hulls or between the inner boards. The distance between the design water-plane and the bottom of the above-water platform (“wet deck”) is named as “vertical clearance”. The longitudinal distance between a triple-hull ship is named as “longitudinal clearance” and can be measured between the middles of hulls or between their fore perpendiculars. Specificity of
multihulls. The difference of geometry defines some sufficient differences of ship characteristics. Some differences ensure some technical and exploitation advantages and disadvantages for ships of various purposes. All multihulls have the following common specificity: - Widest possibility of geometry variations; - Relatively bigger, than in the comparable
monohulls, area of decks, upper and inner ones. - It means the possibility of relative bigger inner volume of watertight above-water platform, which connects the hulls. - Independence of transverse stability from single hull lengthening; the stability strongly depends from the transverse clearance. - It means a possibility of simple enough ensuring of transverse stability of any multihull type. - Besides, it means the possibility of a wide variation of hull lengthening for higher performance. - Higher
non-sink-ability because of big enough volume of the above-water platform. - Higher safety and survivability of energy sources because of power engine dividing by parts are distant each from the other. - Relative bigger overall beam. - More or less higher (in the dependence of the multihull type) seaworthiness in the comparison with the monohull of the same displacement. All ships with small-water-plane area, SWA ships, have smaller motions of any kind and external wave forces and moments, except the case of sailing in following waves. All systems of motion mitigation are the most effective ones for SWA ships.
ADVANTAGES and DISADVANTAGES of MULTIHULLS
As follows from, the specificity of multi-hulls can be an advantage for defined purposes, as below. The greater range of geometric variability allows to designers wide possibilityes of characteristic optimization in accordance with practical needs; the possibility of lower wave-making resistance (as a sufficient part of towing resistance ) is a sufficient advantage for high-speed and fast ships; the towing resistance can be significantly decreased by a rational selection of hull aspect ratio (twin-hull ships) and arrangement of hulls to take the most benefits of the interference between the wave systems generated by each hull (triple-hull ships); significantly greater area of decks and volume of closed (including watertight) and open spaces for payload; as a result, a multi-hull vessel can be a preferred choice for shipping high-volume and light-specific-weight payload (passengers, automobiles, etc.); transverse stability is independent of the aspect ratio of any hull, but depends on the transverse distance between the hulls at degree two; as a result, the transverse stability can be comparable with longitudinal stability, or even exceed it in some cases; it means wider possibility of dimension optimization without any restrictions by the transverse stability; a possibility of increasing the
non-sinkability of the vessel by providing watertightness to the volume of the above-water platform and its rational dividing by water-tight bulkheads; it means higher safety of all multi-hulls in a comparison with the
monohulls; higher safety and survivability of power plant machinery due to greater variability of the safest accommodation of its main components; it means higher survivability of all multi-hulls, especially - of combat ones; higher seaworthiness means higher part of time of sailing, when all needed demands of passenger and crew comfort are fulfilled.
The main disadvantages of multi-hull ships, as compared to
monohulls, are the following:
*
the wider overall beam of a multihull vessel is often a problem for conventional docking;
*
the relatively greater total wetted area increases the frictional component of water resistance of the vessel, and thus the total resistance at low
speeds (though this may balance out if eliminating wave
resistance significantly;
*
the weight of hull structures per ton of displacement is greater than that of
monohulls;
*
assembly of a multi-hull vessel in a shipyard takes a wider area;
*
as a result, the construction cost and maintenance (in dry dock) can be
greater - but careful design can actually decrease
construction costs.
Marine
& Boat Insurance Providers Table
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Company
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Type
of Insurance
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Website
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24
hour dinghy insurance
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Dinghy
& Sailboard Insurance Immediate insurance
premiums displayed by clicking onto the class
of craft.
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24
hour dinghy insurance
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ABG
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We've
teamed up with Boatinsure.co.uk to provide our
clients with a competitive online marine
quote: DINGHY, SPEED BOAT, SMALL YACHT, CABIN
CRUISER.
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ABG
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Affinity
Insurance Brokers
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Official
Brokers to the Irish Sailing Association.
Affinity Insurance Brokers, the premier source
for insurance coverage and risk management
advice for Ireland's sailing and fishing
communities.
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Affinity
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Amilcroft
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Cargo
INSURANCE. Take advantage of capacity and
services through the London market and other
specialist insurers. Our arrangements include
insurers able to write surplus lines in most
of North America.
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Amilcroft
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Arden
Insurance
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Arden
Insurance Services are able to arrange cover
on all craft from the smallest of dinghies to
the largest ocean going vessels. Discounts are
also available for: RYA Qualifications, Policy
excesses up to 1,000GBP, Craft in Marina
Berths, Craft with alarms. Many of our
standard policies include: Third Party
Liability up to 2,000,000GBP, 12 Months in
commission cover, Underwater Machinery Damage,
Protected No Claims Bonus, Road Transit Cover,
Legal Protection Cover.
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Arden
Insurance
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Edwards
& Associates
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We
offer marine insurance to cover pleasure boats
such as yachts and cabin cruisers, as well as
larger private boats. Whether you are looking
for personal or commercial marine insurance,
we have a large base of insurers who we use to
make sure that you get the best possible deal:
Personal and Commercial Marine Insurance.
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Edwards
& Associates
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BC-Marine
Inurance
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Set
the right course to solve your Marine
Insurance Requirements. Marine Craft
Insurance, Legal Protection, Foreign Travel,
Boat SalesAccident & Medical, Loss Of
Earnings, Marine Finance, Marine Tradesmen,
Crew Liability, Instalment Plans, Boat
Builders & Repairers, Public Liability,
Recovery & Assistance, Product Liability.
UK, Ireland, Scotland, Wales & the EU.
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BC-Marine
Inurance
|
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Bishops
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We
have particular expertise in the following:
International Marine, Cargo, Inland Goods in
Transit, Hauliers Liability, Freight
Forwarders Liability.
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Bishops
plc
|
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Alfred
Blackmore
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Alfred
Blackmore Group Ltd UK insurance broker
specialising in bloodstock, classic car,
construction, financial services, healthcare,
international motor, marine, professional
indemnity, reinsurance and special accident.
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Alfred
Blackmore
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Blythin
& Brown
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Loughborough
brokers provide online quotes for marine
insurance, and also offer a full range of
financial advice.
|
Blythin
& Brown
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Boatinsure
|
Marine
insurance underwritten by Lloyd's of London.
Discover what is covered by the policies, read
the FAQs, get an online quote or claim online.
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Boatinsure
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Business.Insurance-Site.co.uk
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Covers
most commercial risks in the following
industries: manufacture, motor trade, haulage
supply, farms, shops, offices, clubs, pubs,
hotels and marine (ONLINE APPLICATION FORM).
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Business.Insurance-Site.co.uk
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Craftinsure
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German
marine insurer provides boat-insurance
services throughout Europe. Select a boat
type, get a quick quote, and track a claim.
20% internet purchase discount.
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Craftinsure
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Newton
Crum
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Dinghy
- Narrowboat - Motorboat - Sailboard- Yacht -
Marine Insurance. FREE INSURANCE QUOTATIONS no
charge or obligation. Dinghy Insurance,
Sailboard Insurance, Inland Waterways
Insurance, Yacht - Motorboat - Speedboat
Insurance, Stolen Boat List.
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Newton
Crum
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Engine
Breakdown Cover Ltd.
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Offers
unique insurance policies for marine in-board
engines.
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Engine
Breakdown Cover
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Fairmont
Insurance Services
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Super
Yacht Insurance for yachts in excess of $1
Million to over $125 Million. Coverage
includes Liability, Loss of Charter, and Crew
Personal Accident and Medical.
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Fairmontinsure
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Lucas
Fettes & Partners
|
Marine
Insurance: Hull and accessories of a vessel,
passengers and worldwide cargo movements.
|
Lucas
Fettes
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Navigators
and General
|
Navigators
and General has been at the forefront of yacht
and motorboat insurance since 1921 and has
been the market leader in this field for over
70 years. Navigators & General is part of
the Zurich Financial Services Group and
Financial Ombudsman Service, providing
policyholders with world-class security.
Today, Navigators provides cover for vessels
with a total value in excess of £750,000,000.
Underwriting insurance for all types of
leisure craft, from dinghies to £5,000,000
vessels, has provided us with the breadth of
experience to understand even the most
individual requirements.
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Navigators
and General
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Giles
Insurance Brokers
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Marine
Insurance. Dinghy, Power Boat, Yacht, Cabin
Cruiser, Jet Ski, Charter Boat, Commercial
Fishing Boat, Yacht Yard
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Giles
Insurance Brokers
|
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SHW
Group
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Marine
Cargo Insurance. Cover is arranged with
specialist insurers and the individual
policies are written to suit your business
requirements including if required Warehousing
for distribution during export or import.
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SHW
Group
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LONHAM
GROUP LTD
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Freight
legal liability for both UK and international
domiciled companies. Freight legal liability
insurance, Cargo insurance, Charterer's
Liability insurance. Delegated authority to
deal with claims matters relating to marine
insurance.
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Lonham
Group
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Mardon
Marine Insurance Brokers
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boat-insurance.co.uk
and yacht-insurance.co.uk are the websites of
Mardon Marine and maritime Underwriting
Agencies Ltd. (Including Maritime Underwriting
Agencies Ltd)
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Mardon
Marine
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Noble
Marine
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Noble
Marine are specialist insurance brokers
dealing with all classes Yacht insurance,
rowing insurance, laser class, dinghy
insurance, sailboard insurance.
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Noble
Marine
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Rob,
Perry Marine
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Need
Insurance? We are agents for one of the most
competitive insurance brokers in the country
who specialise in marine insurance.
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Rob,
Perry Marine
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Pendleton
May
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We
operate a scheme for the insurance of yachts,
motor boats and small craft. Our expertise,
experience and number of clients insuring
their boats enables us to provide you with
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Pendleton
May
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Terra
Nova
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Terra
Nova Protection & Indemnity provides fixed
premium P&I cover for the Owner / Manager
/ Charterers of commercial ships operating in
domestic, coastwise or short-sea trades.
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Terra
Nova
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Oban
Insurance Centre
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Read
about the insurance schemes covering marine,
holidays, business, motoring and agriculture.
Offers an online quote system.
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Oban
Insurance
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B
Portwood & Co.Ltd
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Marine
and boat insurance. On-line insurance rates
are provided for dinghies, canoes, sailboards,
small craft, inflatables, speedboats, yachts
and motorboats for use in the uk and in
Western Europe for up to 60 days.
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Portwood
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Alexander
Brooks & Stevens Ltd
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Marine
Insurance providers
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Alexander
Brooks & Stevens
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Graham
Sykes Insurance
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Graham
Sykes Insurance insure a variety of boats. Our
polices cover you for use on inland and costal
waterways between May and September. Smaller
craft usually have to be laid up ashore over
the winter months. For larger vessels we can
provide cover for them all year round. For the
water skiers out there we can usually extend
your policy to include liability for towing
water skiers.
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Graham
Sykes
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Craig
& Suttar
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In
most cases we can provide all risks cover
including third party liability for you and
your craft. Polices cover you for use on
inland and costal waterways between May and
September. For the waterskiers out there we
can usually extend your policy to include
liability for towing waterskiers. In some case
we can add your boat onto your house contents
insurance which is sometimes cheaper.
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Craig
& Suttar
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Tyser
(UK) Ltd
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Marine
and boat Insurance
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Tyser
(UK) Ltd
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Yachtsman
Marine Insurance Ireland
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Yachtsman
Marine Insurance Ireland. Sports boats, Yacht
cruisers, motor cruisers. We offer yachtsmen
an exceptional insurance package at a highly
competitive price. We are constantly reviewing
our policy wording to provide the most up to
date terms and conditions to ensure that our
clients have the most appropriate cover.
|
Yachtsman
Insurance
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Meeting
Your Needs
Offering a range of services to most business sectors
the providers below specialise in insurance design, risk
placing and risk management for UK and international
concerns.
They have considerable experience in the development of
solutions for both Marine and Commercial risks. With
access to Lloyds of London and a range of ABI registered
Insurers they can secure the most competitive premiums
and terms. All of the above is a very good reason
to click through from us to obtain your online
quotation, and it doesn't cost you a penny more to do
so.
LINKS
http://www.mocra-sailing.co.uk
The Multihull Offshore Cruising & Racing Association
http://www.catamaran.co.uk/main.htm
The UK Catamaran Racing Association
http://www.mycq.org.au/
The Multihull Yacht Club of Queensland (Australia)
http://multihullboatbuilder.org
Multihull Boatbuilding Information / Community
http://www.multihull-maven.com
Articles and news on multihulls, profiles of boats, designers, yards, etc.
http://www.sailing.org
International Sailing Federation
http://www.multihulls-world.com/us/
The multihulls reference magazine
http://www.multihull.com.au
The multihulls reference magazine (Australia)
Fleet
operators might reduce insurance costs if their ships have
autonomous
capability, which system promises safer
seas.
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