Rudder & Steering Gear (General) — Most Asked Questions
18 questions asked about rudder & steering gear (general) across the General and Fn 3 papers, heaviest first.
Learn the system first
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1 Types of rudder
Also asked: “Name 3 types of rudders”
Answer
Rudders are balanced, semi-balanced or unbalanced by how much blade sits ahead of the stock — balance cuts torque but costs support.
- Balanced: large area ahead of the stock — spade and open-sternframe types need the least steering effort but load the stock in bending.
- Semi-balanced: part of the chord ahead, part behind, often with a horn — returns toward centre if the gear fails and suits most merchant ships.
- Unbalanced: all blade aft of the stock — simplest and strongest support, heaviest to turn, for small craft and barges.
- Specials: full-skeg, flap and fishtail types trade manoeuvring lift against complexity.
Surveyor follow-up: why does a semi-balanced rudder creep back to midships when the gear fails mid-turn?
Full theory: Rudder: Construction, Types & Support -
2 Controllable pitch propeller
Answer
CPP changes blade angle under way: hub servo through yoke and crank pin, oil fed down the shaft — thrust either way without reversing.
- Blade carriers turn on crank pins driven by a fore-and-aft yoke inside the hub.
- The yoke moves on an oil servo in the hub cone or shafting, fed through sleeve grooves and shaft drillings.
- Flange-mounted with access through the hub centre or removable covers for mechanism inspection.
- Manoeuvring wins: full astern pitch at full shaft speed — at the cost of hub complexity and oil discipline.
Surveyor follow-up: pitch stuck ahead with the shaft turning — hydraulic, control or mechanical seizure, and what do you check first?
Full theory: The Propeller — Fixed Pitch, Controllable Pitch and Cavitation -
3 Fixed pitch propeller The blades in fixed pitch propeller are permanently attached to the hub. The fixed pitch type propellers are casted and the position of the blades and hence the position of the pitch is permanently
Also asked: “Fixed pitch propeller The blades in fixed pitch propeller are permanently attached to the hub. The fixed pitch type propellers are casted and the position of the blades and hence the position of the pitch is permanently fixed and cannot be changed during the operation”
Answer
Fixed-pitch wheels are one cast block of copper alloy: blades frozen on the hub, thrust married to shaft speed.
- Pitch fixed at build and unchangeable at sea; thrust varies only with engine power and rpm.
- Robust and reliable with no hub moving parts — cheaper to make, fit and run than controllable pitch.
- Manoeuvring is poorer: stopping and backing need shaft reversal or gearbox work.
- Standard fit for ocean traders — containers, bulkers and tankers — with thrusters covering port work.
Surveyor follow-up: fixed-pitch ship makes sternway slowly with full rpm astern — normal or fouled, and what proves it?
Full theory: The Propeller — Fixed Pitch, Controllable Pitch and Cavitation -
4 These types of propellers are fitted in a ship that does not have good manoeuvrability requirements
Answer
Fixed-pitch wheels suit ocean traders that rarely manoeuvre: cheap, tough and efficient at one speed with thrusters covering ports.
- Cast in one block with pitch frozen — thrust follows engine power and rpm only.
- Robust with no hub moving parts, cheaper to make, fit and run than controllable pitch.
- Poor at berthing and crash stops without shaft reversal or gearbox help.
- Containers, bulkers and tankers on long ocean legs fit them; bow thrusters cover the port work.
Surveyor follow-up: fixed-pitch ship making sternway slowly at full astern rpm — normal or fouled?
Full theory: The Propeller — Fixed Pitch, Controllable Pitch and Cavitation -
5 Types of rudder( which rudder on ur ship)?
Also asked: “Types of rudder and what's on ur ship? Speciality about semi balanced rudder?”
Answer
Name rudders balanced, semi-balanced and unbalanced — then point at your ship’s semi-balanced skeg and say why.
- Balanced: big area ahead of the stock — spade and open-sternframe types, lightest steering, heaviest stock.
- Semi-balanced: part ahead, part behind with a horn — self-centring on gear failure, the modern merchant standard.
- Unbalanced: all blade aft — simplest support, heaviest to turn, for small craft.
- Finish with your ship: type, horn depth and why her trade suits it.
Surveyor follow-up: why does your semi-balanced rudder creep back to midships when the gear fails?
Full theory: Rudder: Construction, Types & Support -
6 Write briefly on rudder
Answer
A rudder is blade, stock and bearings turning propeller slipstream into turning force — area, balance and support decide her.
- Blade with horn or skeg support, stock through the hull, pintle below and carrier bearing above.
- Balance by area ahead of the stock: balanced, semi-balanced or unbalanced with torque to match.
- Turning force grows with speed, angle and propeller race over the blade.
- Survey points: stock seals, bearing play, horn cracks and drain-plug dryness in dock.
Surveyor follow-up: point at the stern and name stock, horn, pintle and carrier — then state the balance.
Full theory: Rudder: Construction, Types & Support -
7 Semi balanced rudder
Answer
The semi-balanced rudder splits the blade across the stock: top unbalanced for support, bottom balanced for light torque and self-centring.
- Chord part ahead of the stock balances pressure; part behind drives the turn — shallow or deep horn tunes the split.
- Top unbalanced length carries vertical support into the horn; balanced length below cuts steering torque.
- On gear failure the balanced area weathervanes her back toward centreline on its own.
- The economical merchant-ship compromise between heavy unbalanced and stock-straining fully balanced wheels.
Surveyor follow-up: shallow or deep horn on your ship — which one, and how does it change torque?
Full theory: Rudder: Construction, Types & Support -
8 How the inside of rudder is painted?
Also asked: “How do you paint inside of rudder”
Answer
Rudder interiors get float coat with the drain plug telling the truth: painted sealed, proved dry in dock.
- Inside coated by float-applied paint sloshed to every web and stiffener before sealing.
- Drain plug at the bottom opened in dry dock — water out means the shell breathes and needs work.
- Nothing out with a dry interior means paint holding and plate sound from inside.
- External wastage with a dry plug still earns ultrasonic readings — inside paint hides nothing from steel loss.
Surveyor follow-up: water from the plug with paint intact — seam, plug or plate, and what next?
Full theory: Rudder: Construction, Types & Support -
9 How to take rudder drop?
Answer
Rudder drop is weardown read at the top: measure at the tiller or upper gudgeon against build marks with the plug out.
- Open the bottom drain plug in dock — water out betrays a breathing shell before measurements start.
- Read drop at the tiller or upper gudgeon against previous figures; little or none is normal on carrier-supported rudders.
- No carrier means real drop: worn pads in the lower gudgeon earn renewal past maker limits.
- Prove pintles under 5 mm slack with nuts locked and carrier faces examined where drop appeared.
Surveyor follow-up: drop grown with water from the plug and carrier faces scored — bearing, shell or both, and what next?
Full theory: Steering Gear Maintenance — Rudder Drop, Bearing Clearances and Overhaul -
10 Difference between bearing pintle and rudder pintle? (Didn't know
Answer
Pintles share the rudder’s weight story: locking pintles hold it up, bearing pintles catch it if the carrier fails.
- Locking pintles on top with shoulders stop the rudder lifting off its bearings in a seaway.
- Bearing or bottom pintles sit on hard steel discs ready to carry the rudder only when the carrier fails.
- Normal weight rides the carrier’s greased thrust cones with the stock journal located beneath.
- Measure top, bottom, jumping and washer clearances in dock with swell limits on phenolic bushes near 1.5%.
Surveyor follow-up: carrier wiped with the bottom pintle carrying full weight and clearances grown — sail, slow or dock now?
Full theory: Rudder: Construction, Types & Support -
11 Sketch the arrangement of rudder stock, bearings, glands and method of suspension of a pintleless rudder, labeling the component parts
Answer
Sketch a spade rudder hung on its stock alone: stock through trunk and carrier with glands sealing, no pintles below.
- Stock in cast or forged steel sized by torque and bending, coupled to the rudder low by horizontal or vertical bolts.
- Carrier bearing on framed support takes the full weight on greased base and moving cones with doubling beneath.
- Journal bearing locates the stock above the trunk with glands keeping sea out of the steering flat.
- Removable coupling lets the rudder drop clear for inspection — label stock, trunk, carrier, journal, glands and coupling.
Surveyor follow-up: weardown high on a pintleless rudder with glands weeping — carrier, stock or alignment first?
Full theory: Rudder, Stock and Carrier Bearing — Weardown, Rudder Drop and Pintle Clearance -
12 How to check propeoller drop and rudder dropnclose space entry
Also asked: “how to check propeoller drop and rudder drop”
Answer
Both drops are read the same way: a fixed datum in the shaft line, a depth micrometer, and the same blade every time.
- Propeller drop: turn the engine until the propeller mark coincides with the stem boss, or keep cylinder 1 at TDC with the marked blade above.
- Remove the screw plug in the stern-frame boss and fit the plug with the central hole — the top of that plug is the datum.
- Rudder drop is read at the tiller or the upper gudgeon against build marks, with the bottom drain plug open to check the shell.
- Both are enclosed-space entries at the stern: permit, gas test, the attendant and a written measurement each time.
Surveyor follow-up: drop reading taken with the rudder to one side and the tiller lashed — which datum was that reading from?
Full theory: The Propeller — Fixed Pitch, Controllable Pitch and Cavitation -
13 Rudder aspect radio
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14 Rudder is hollow or solid?
Answer
Rudder is hollow and fabricated: the shell is a welded assembly with a cast stock, because weight at the rudder is expensive.
- A solid rudder of the required strength would be far too heavy to swing and would load the steering gear beyond reason.
- Hollow fabrication gives the same stiffness at a fraction of the weight, and the shell is a welded steel structure.
- The stock and the carrier bearings are cast or forged and bolted into the shell — the two materials sit side by side.
- That is also why the inside is painted and the drain plug fitted: the shell holds water against the plating and corrodes from within.
Surveyor follow-up: water found inside the rudder with the drain plug open on deck — is the plug, the seam or the stock the leak?
Full theory: Rudder: Construction, Types & Support -
15 Semi balance ruder why is called semibalance and how much part is located aft
Answer
A semi-balanced rudder is balanced at the centreline: half the area forward of the stock and half aft, so the torque cancels only there.
- At the centreline the centre of stock and the centre of effort coincide, so the torque is zero there and grows at other angles.
- About half the rudder area lies aft of the pivot, which is why it is called semi-balanced rather than fully balanced.
- It cuts the diameter of stock and the power of the steering gear compared with an unbalanced rudder, without a full balance.
- The angle is usually limited to about 35° each side, because beyond it the turning circle diameter increases again.
Surveyor follow-up: helm reported heavy at 30° with a semi-balanced rudder — is it balance, stock diameter or the pump?
Full theory: Rudder: Construction, Types & Support -
16 Sketch a semi balanced rudder of your choice showing
Answer
A semi-balanced rudder is balanced only at the centreline: draw the pivot, the centre of effort and the area each side.
- Draw the pintles or hinges the rudder turns on, and mark the rudder stock and tiller line through them.
- Mark the centre of effort and the centre of stock coinciding at the centreline — that is what makes it semi-balanced.
- Show the area aft of the pivot: about half the rudder, which is what the name means, and the stock ahead taking the rest.
- Note that the angle is usually limited to about 35° each side, because beyond that the turning circle grows and the torque returns.
Surveyor follow-up: sketch shows a fully balanced rudder with the whole area aft — what name does that arrangement have?
Full theory: Rudder: Construction, Types & Support -
17 Struture of rudder? Why hollow?
Answer
A rudder is a welded shell around a cast stock, hollow so the same stiffness costs a fraction of the weight and load.
- Shell plating, a stock of cast or forged steel, and the carrier or pintle bearings bolted into the assembly.
- Hollow construction gives the required moment of inertia without a mass that would overload the steering gear.
- Internally the shell is painted and fitted with a drain plug, because a sealed shell traps water against the plating.
- The weight saved at the rudder also reduces the top weight, which helps stability as well as steering power.
Surveyor follow-up: rudder shell corroding from inside with the plug missing — is the paint, the drain or the seam?
Full theory: Rudder: Construction, Types & Support -
18 Type of rudder everything related to it
Answer
Rudders are typed by support: balanced, semi-balanced and unbalanced — the difference is how much area sits aft of the stock.
- An unbalanced rudder has no area aft of the pivot, so every degree of helm throws the full hydrodynamic moment back at the gear.
- A balanced rudder has a counterbalance aft of the stock so the centres of stock and effort coincide at the centreline.
- A semi-balanced rudder is balanced only at the centreline, with about half the area aft of the pivot.
- There are also spade rudders on a carrier and pintleless rudders suspended from the stock, and foil sections for high speed.
Surveyor follow-up: rudder claimed balanced with a heavy counterbalance aft — which type is that, and what does it cost in drag?
Full theory: Rudder: Construction, Types & Support
Source: 123 written papers and surveyor oral banks, 24,613 entries, merged into 17,210 topics. Ticks are stored on this device only.