What is a cable gland?
It is a sealing part that prevents water from entering through the propeller shaft. There are several models and if some ensure a perfect seal, for others it is normal that they let some drops of water pass.
Why cable gland?
Tow is the fibrous component produced, among other things, during the combing of linen or hemp. In the old navy, oakum was mainly made from hemp and lint from old ropes and was used to choke and caulk ships.
With the advent of motor ships with shaft lines, a problem of water entry arose and the stuffing box, previously soaked, was the only known seal. It was held in place in a stuffing box. This generic word has been retained to designate rotary joints and other sealing systems.
What about today?
Many boats are equipped with a motorization with shaft line* and the stuffing box is necessary.
The propeller shaft line is composed of
- of a propeller shaft (1)
- a journal to connect the propeller shaft to the inverter and thus to the motor (5)
- a cable gland for sealing (3)
- a stern tube to guide and hold the propeller shaft (2)
- a hydrolube ring which will limit the vibrations of the propeller in rotation and cool the shaft by letting water pass through the shaft seat (4)
Two main families of cable glands
There are 2 main families of cable glands:
- With oakum
- With swivel joint
The rubber gasket gland is a popular product for sailboats. Water circulation lubricates the seal. The seal on the propeller shaft is made by a lip seal. On some installations, it is necessary to provide a water supply for better operation.
A little maintenance and vigilance
Before launching your boat and after a long winter, it is recommended to slide the seal on the shaft and check everything. First of all, have the necessary tools and products on hand.
ATTENTION this operation is only to be carried out with the boat out of the water!
Step 1 unscrew the clamps that secure the joint to the stern.
Rotate it to check its condition. There should be no cracks or splits.
Step 2 clean and grease the outer part of the stern and the shaft.
(This allows the seal to be replaced without difficulty)
You can also use a syringe to grease the bottom of the stern.
Step 3 reassemble and rotate the shaft by hand to make sure everything is in place.
Checked and maintained, your gasket will provide between 500 and 600 hours of trouble-free engine operation.
While your boat is dry, take the opportunity to check the clearance of the hydrolube ring in the shaft chair. If a play of 1 to 2 mm is normal, beyond that you risk to have strong vibrations damaging the shaft and the motor. It is therefore preferable to change the ring.
Once in the water and before starting, make sure that the rubber bellows of your stuffing box is well filled with water. This is determined by pushing the bellows slightly apart to allow water to pass through. For boats that run aground or just after a launch, it is very important to squeeze the gasket so that the water replaces the air in it.
