Entries Tagged 'Engines and propulsion' ↓
July 12th, 2008 — Boat Maintenance and Repairs, Engines and propulsion
Although the dripless shaftseal has been around for many years a lot of boats still have the old stuffing box.
The stuffing box is an old solution to the problem of allowing the prop shaft to turn and exit the hull without letting to much water in.
The advantages of this system are that it is cheap and reliable. Maintenance is easily performed with basic tools and skill level. The packing is cheap and at a pinch it can be replaced on smaller craft whilst the boat is in the water. Though obviously it easier to do this whilst on the slip.
The down side of this system is that whilst underway the seal must be allowed to drip to keep the seal lubricated and cool whilst in use. Obviously this allows a small but steady trickle of salt water into the hull which then must collected and disposed of. Also as the packing material is compressed against the expensive shaft it wears a groove into your expensive prop shaft overtime. Eventually the shaft diameter is reduced so much that seal cannot be maintained and the shaft must repaired or replaced.
To overcome the disadvantages of the stuffing box two types of dripless shaft seal have been developed.
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February 18th, 2008 — Engines and propulsion
Many yachts in the 25 to 35 foot range are used on sheltered waterways and hardly clock up any engine hours. The motor is mainly being used for a short time at the beginning and end of each trip. Small inboard diesels have well known downsides in this context. Short operating periods and long periods of neglect are bad for these engines.
Faced with replacing the inboard motor on his Catalina 27, American sailor and electrical engineer Scott McMillan installed a self built electrical propulsion system. Impressed with the performance he decided to develop the Electric Yacht System as a commercial enterprise.
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February 15th, 2008 — Boat Maintenance and Repairs, Engines and propulsion
Every boat owner with an inboard engine should carry out these quick and simple checks prior to starting their engines. Mostly they will prove unnecessary but performed regularly they will familiarise you with the engine and just may prevent inconvenient and costly damage.
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January 30th, 2008 — Boat Handling, Engines and propulsion
Many people find berthing their boat stressful, especially in adverse weather conditions or coming into an unfamiliar berth or marina. While watching people come into berths, I am often amazed by their apparent lack of preparation and forethought.
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January 23rd, 2008 — Engines and propulsion
What are the advantages of having one engine or two?
Single Engine
Pros
- Cheaper purchase/installation costs
- Less maintenance
- More efficient
- Propeller and rudder usually better protected by keel
Cons
- No back up against engine failure
- Less low speed manoeuvrability
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January 18th, 2008 — Engines and propulsion
These days there are a variety of propellers around, so which is the right one to use? Here’s a description of the types of propellors with pros and cons of each.
Fixed propellers
Fixed propellors are relatively cheap and efficient at their designed parameters, i.e. at one particular point in the rpm range, but under or over pitched under all other conditions. Not so efficient in reverse and cause drag on sailing boats under sail.
Folding Props
Folding props are similar in performance but less efficient than fixed props. They are mechanically more complicated and more expensive. There can be a delay after engaging gear while the prop opens and “bites”. They cause the least drag when sailing but this will be diminished if there is a large deviation in shaft angle from horizontal. If changing from a fixed prop more clearance will be required behind the prop to accommodate the folding blades.
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January 16th, 2008 — Engines and propulsion, News
Sea trials of the wind assisted 10,000 tonne cargo vessel Beluga Skysail whilst on route
from Germany to Venezuela will commence this month. Once the vessel is in the open sea it will launch a giant sail similar to a kite, conditions permitting one would imagine. The pulling power of the sail will not replace the engines but reduce fuel consumption, saving fuel costs and reducing air pollution. The sail on the Beluga Skysail is 160 square meters and it is anticpated it will reduce fuel usage by 10% - 15%. Skysails are are also targetting the superyacht market.
Interestingly I came across another company Kiteship, who have been developing the same idea. They also have a smaller version suitable for leisure boats. It will be interesting to see if we get any power boaters brave enough to hoist a sail.
