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Hose clip corrosion

7 April, 2017

Stainless steel hose clips on hose tails are fit and forget, right? Sadly not.

The problem with stainless steel is that it is only stainless in the presence of oxygen. This is because an oxide layer forms on the surface of the steel and this is what protects it from corrosion. If you remove the oxygen then the oxide layer cannot form and the stainless steel is about as corrosion resistant as mild steel.

When hose clips are clamped tight onto hose tails the underside is no longer in the presence of oxygen and the stainless steel can start to corrode. The trouble is, its not always obvious like the picture above. Normally the only way you can tell is by removing the hose clip and looking at the underside. In severe cases, gently tapping the clip can cause it break open.

Regularly inspect your hose clips and slacken one off at a time to have look at the underside.

As an aside, sometimes I find hose clips neatly lined up with the screw heads next to each other as in the above picture. This is not the correct way, the heads should be opposite each other to get a better seal on the tail.

Stanchion bases

31 March, 2017

Often I find stress cracks to the gelcoat of yacht decks around the bases of stanchions. Whilst they are not normally structural they do indicate that high loads have been applied to the stanchions and caused the deck to flex more than the gelcoat can tolerate.

The cause is normally crew members using the stanchions to pull themselves up from the pontoon to board the vessel. The length of the stanchion is long and creates huge leverage forces against the all too small backing pad on the stanchion base.

The stress cracks can be repaired easily enough but its much easier to prevent the crew from using the stanchions as levers in the first place. Use the shrouds to pull yourself on deck. The fittings here are much stronger and will not crack the gelcoat. Remember the stanchions are to support the guard rails and designed to prevent you falling overboard at sea not for pulling yourself onboard in harbour.

Ideally the backing pads should be larger to help spread the loads and make the structure stronger. Unfortunately removing the linings and panels internally to gain access can be a larger job than fitting larger backing pads so often doesn't get done.

Lastly, don't forget to fit and check the retaining grub screw or split pin to secure the stanchion post to the base plate, it's missing in the image above.

Propeller nut fastening

26 March, 2017

The end of the prop shaft is normally tapered and has a keyway in it as well to transmit the torque from the shaft to the propeller. Retaining the propeller on the shaft is done by lock nut.

The lock nut can occasionally come loose when the shaft rotates in the opposite direction to the thread. This can result in the loss of an expensive propeller and all drive!

There are many different ways of securing the propeller nut including; castellated nuts with split pins; drilled nut with split pin; cone nut with lock bolt; a tab washer bent over or; locks nuts.

Lock nuts are not so common in the UK but its worth noting that when fitted, the half nut (the thinner nut) should be fitted first with the full nut last. This seems counter intuitive but actually splits the load correctly between the two nuts.

Each method has its advantages but should never be overlooked when refitting a propeller and should always be checked when the vessel is lifted for any maintenance. Also check for play in the keyway by turning the prop by hand.

Beware of chafe

19 March, 2017

Chafe is well known as a problem for running rigging and sails but it can also affect other parts of a vessel. The photo above shows a fuel hose that was resting on a cutout through a bulkhead in the engine space. As the engine vibrated during normal running the hose gently chafed away unseen.

This one I picked up on an insurance survey and was only evident when lifting the hose to inspect the underside. The owners had completely missed it and were preparing for an offshore passage. Had the line chafed through it was positioned ready to leak fuel over the hot engine. On the same survey I found the exhaust hose was similarly worn through where it was sitting on top of a stud retaining the SailDrive ring.

Inspect the clamping and securing of your hoses or electrical lines to ensure they do not chafe either through engine vibration of movement when underway. Inspecting the hose and cable runs when running the engine on the berth should give a clue, if you see a hose or wire vibrating then its worth securing it with a saddle clamp or cable tie to prevent it wearing through and spilling its contents or shorting a circuit. Placing sheathing around the hose can help but doesn't stop the chafe, it only delays it.

Flexible gas hose

12 March, 2017

Rubber gas hose from the regulator to the bulkhead connector should be rated for LPG and marked as BS3212:1991 and also have the manufacture’s name and date on it. Many boats I come across have old pipes that are cracked and damaged such as the one in the photograph from a boat surveyed recently.

Remember to;

  • Keep the hose away from bight sunlight to avoid UV damage, damp and mechanical abrasion. They are in a harsh environment and can degrade faster is abused.
  • Check for damage to the hose such as cuts, cracks, swelling or abrasion and replace the hose if damaged.
  • The useful life for regulators and hoses is approximately 5 years and they should be replaced after this time.

Regulators cost around £20 and the hose is around £3/m. We all know gas onboard boats can be dangerous so it is worth checking and replacing these relatively inexpensive items.