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SPLANING

076
This page is dedicated
to Peter and Emily

DISPLACEMENT HULLS

​Displacement hulls displace the same amount of water whether stationary or moving.  We are indebted to an ancient Greek, Archimedes of Syracuse, for figuring out why floating bodies displace their own weight of the liquid in which they are floating. 
​
Displacement hulls are supported by buoyancy and include big, round, bulbous hulls such as you see on Dutch Barges which also include elements of the Cathederal Hull to get them to plane at speed in open water.  All canal boats use displacement and speed through the water is limited by their waterline length.  ​It is total waste to put big horses into a displacement hull as its only effect is to increase the bow wave when the power is applied.  A narrow boat is incapable of exceeding 4mph in the restriction ditch of a canal and this is best seen when approaching a bridge where you go in at whatever speed you like and exit at almost zero.  Go figure. Most boaters don't.  The ideal cruising speed in a canal boat is 2mph making almost no bow wave and optimising distance run against fuel burned.

Macho boaters do not know this and cause much aggro and bad feeling by setting up wash that wrecks canal banks, disturbs sediment, alarms wildlife, swamps nests in season.  ​Their passage  affects moored boats also in the displacement of their 20+tons of weight from before their boat to behind their boat especially in shallower reaches where water can not get UNDER the boat.

In plain language:

Go slow and stop rocking the boats

 international code of signals uses

ROMEO YANKEE

Flat bottomed Cathedral hulls need less effort to get them on the plane, but because they have a larger flat surface area they are less comfortable in chop.   They provide a very stable platform at slow speed which is a consideration when designing 9or buying!) a canal boat.
DIRECTIONAL INSTABILITY
Pentargon is very skittish under way and the helm has to be constantly watched.  Left to itself for even a few seconds it tends to steer itself and in an unpredictable manner.  Its directional stability in calm weather and still water depend on many variables such as biased loading and trim. The water tank is far forward in the bow while the twin fuel tanks are low in the stern on each side of the engine.   However this instability makes for a very manoeuvrable boat with very quick response.  In 2023, while in dry dock, I found  the [original 1973] lower rudder pin was eating away its pivot.  A welded in rudder cup tightened up the steering no end but sea trials will have to wait til the boat is back in the water.  WIP 20230425

​​A ship is directionally stable if deviation from a set course increases only while an external force is acting to cause the deviation.  A directionally stable ship requires less energy expenditure by its steering gear in maintaining a set course.  Left to its own devices it tends to 'steer itself'.

It is unstable if a course deviation happens in the absence of an external cause.  A directionally unstable ship is easy to manoeuvre but the helm needs constant supervision to hold a course.  A compromise between extremes is therefore desirable.
​​​Survival At All Costs
And At No Cost At All

[email protected]
FIND ME ON BLUESKY
© MMXXv

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  • MUDDY BROWN WATER
    • CORDWAIN
    • Colour of Water
    • Lehman Way
    • Loadsa Money
    • Floating Man Cave
    • Cunning Lists
    • Later Lists
    • letters and articles
    • by buying a boat
    • and floating away
    • with a pint of milk
    • not quite 100 percent
    • begin boating
    • Uisge Donn Salach
    • Boat Survey
    • Hide & Seek
    • Hide and Seek
    • Real Deal
    • Finding a Fix
    • Give me my Boat
    • a failed survey
  • PENTARGON'S BLOG
  • HOME
    • CURLY WURLY >
      • ARTISTIC NARROWBOAT >
        • goldfinch restaurant >
          • tearpree blink
          • tearpree veriews
    • Sail The Dream
    • Sell the Boat
    • Sail-Away
    • ULYSSES UNRAVELLED
    • Pogue Away Day
    • Sailing Away
    • CONCEPT v REALITY >
      • to live off-grid
      • ARRIVAL IN ENGLAND >
        • Original List
      • Wrong Way Round
      • epilogue criochnaithe
      • On-Grid-Ways
      • Recession
      • Slough Arm
    • RELATION ... SHIPS >
      • 12-0 humans
      • 12-1 widminter
      • 12-2 WHO
      • 12-3 WHEN
      • 12-4 HOW
      • 12-5 WHY
      • 12-6 WHAT
      • 12-7 on board
      • 12.8 comms
    • 14-0 ODORSHET >
      • 14-1 facebooked
      • 14-3 excremented
      • 14-4 excretions origins
      • 14-2 macerated
      • 14-5 composting
    • Pentargon Days >
      • 2015
      • The Original Blog List >
        • PENTARGON
        • 60906
  • PENTARGONS GALLEY
    • Pentargon Coffee
    • Off-Grid-Catering
    • Pasta Management
    • Porridge
    • Drop Scones
    • Bolognaise
    • Marinade
    • CuppaCocoa
    • Burger Stew
    • Scromolet
    • Cooking with Steam
  • SPLANING
    • 2013-0 Water Wasted
    • 2013-1 Water Heated
    • 2013-2 water costed
    • 2013-3 water not wasted
  • HOT AND COLD
    • Fuelling Fires
    • Hampshire Heat
    • Charcoal Heat
    • Boat Heat
  • SAMUEL JOHN SPRINGER
    • Operation Pied Piper
    • Sam's Harborough
    • Harborough & Rolt
    • Samuel in Expansion
    • Patience is a Minor
  • BILLY'S STORY
  • TALES FROM THE TIDES
    • ponder not how >
      • London Stones
      • down river
    • Inland Storms >
      • river creek >
        • Mapping My Village
        • Dartford Departure
    • FROM WITHOUT >
      • Just Another Day
      • Spoons on the cut
      • Between the Locks
      • TECHNICAL TALES >
        • ships husbandry >
          • hull maintenance
          • recycling
          • carpentry
        • Mitred Fire Escape
        • qualified bullshitters
        • electric enterprises >
          • Electrical Ingenuity >
            • Charge of the Light Brigade
            • wired in radio
            • charging electric
        • boatpaint
        • propellers - propulsion >
          • Leaf Mugging
      • kenya jacaranda >
        • ebb and flow
        • ship security
        • 2017 jetsam
        • 2016 sink some
      • The Bristol Channel
      • The Boat Flag Story
    • years and tears >
      • Bottle of Wine >
        • The wine travels on
      • flow and ebb >
        • Mitre Gate Lock
  • HOMENENE
    • HAVEN FOR BEWILDERED
    • COMPOS MENSIS
    • JANGLERS HAVEN
    • REPRESENTATION
    • PENTARGONS HOMENENE
  • PENTARGONS BLOGS