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 typically include big, round, bulbous hulls such as you see on those Dutch Barges. 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.
Macho boaters do not know this and cause much aggro and bad feeling by setting up wash that wrecks canal banks, disturbs sediment and wildlife, swamps nests in season. Their passage affects moored boats also in the displacement of their weight from before their boat to behind their boat
In plain language this means:
Go slow and stop rocking the boats
international code of signals uses
ROMEO YANKEE
Flat bottom 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. But they provide a very stable platform at slow speed which is a consideration when designing a canal boat.
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 typically include big, round, bulbous hulls such as you see on those Dutch Barges. 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.
Macho boaters do not know this and cause much aggro and bad feeling by setting up wash that wrecks canal banks, disturbs sediment and wildlife, swamps nests in season. Their passage affects moored boats also in the displacement of their weight from before their boat to behind their boat
In plain language this means:
Go slow and stop rocking the boats
international code of signals uses
ROMEO YANKEE
Flat bottom 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. But they provide a very stable platform at slow speed which is a consideration when designing 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.
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.
