There are many variables to consider when it comes to the longevity of the rod rigging being used with todays modern mast systems.
The most prominent factors are:
The amount of time and/or miles the yacht has been in service
as a general rule, complete Level C inspection for Category I and II boats (see Inspection Tables), of mast and rigging systems after a maximum of 40000-60000 sailing miles or 6 years, whichever comes first. The comprehensive maintenance schedule would include inspection of all the rod heads and end fittings. If any of the heads are cracked or worn, the rod must be re-headed.
This doesn’t mean that the complete rod section must be replaced, that would depend on whether the turnbuckles had enough stroke to compensate for a shorter section of rod.
At the same time the rod is re-headed, replacing the turnbuckle screw is recommended. The screws could last for many additional years, but it is less expensive to replace a few rigging screws than to replace the mast and all of the rigging.
One other rigging fatigue scenario to be aware of is winter storage with the mast system in place. This storage option causes cycling loads (the wind «whistling in the rigging»), which is frequently overlooked because the yacht isn’t in service.
What loads are put on the rod in comparaison to its breaking strength
Racing yachts generally use minimum rod sizes to keep rigging weight and windage as low as possible. As a result of cost constraints, this sizing issue can also be encountered with the rigging of production built cruising boats.
Using a smaller rod size tends to shorten its working life, as maximum sailing loads may approach or exceed 50% of the breaking strength of the rod. Larger custom cruising yachts tend to have a higher safety factor because the chosen rod sizes are typically more conservative, so the rigging loads would only be 15-25% of breaking strength during maximum sailing conditions.
Smaller rod sizes for a given application tend to yield shorter rod life, as the overall safety factors for that application are reduced.
The yachts predominant sailing condition
If the yacht is predominantly sailed in heavy air conditions, the life of the rod will be shorter than if the boat was sailed infrequently or in lighter wind conditions. The higher the rigging is stressed on a regular basis, the shorter its life span will be.
The amount of care and maintenance given to the rigging
If the rigging has been periodically checked, the end fittings rinsed with fresh water, and general care and maintenance have been employed, it will last longer.
How environmental conditions can affect the rigging
A major consideration in the longevity of the rigging system is the environmental conditions the yacht is subjected to. If the yacht spends most of its time in an environment with substantial air pollution, contaminants in the air will generally shorten the mast systems life span, and frequent cleansing and inspection routine (Level A – see Inspection Tables) should be a part of your regular schedule.
Routine inspections with no rod problems
After a thorough inspection (Level C: 40000-60000 miles or 6 years – see Inspection Tables) with no evidence of damage, it may be reasonable to expect the rod to last an additional 20000-30000 miles. However, rod re-healing is recommended, and this is when a maintenance and inspection schedule becomes of paramount importance.
Monitor those T-hooks
One popular fitting that requires more diligent survey and potential replacement is the T-hook. Due to its design, it is typically one of the few fittings with a life expectancy dramatically less than the rod or wire. When inspecting the T-hook, look for cracks on the iside of the sharp bend, as this is a typical spot for fatigue cracking. T-hooks must be diligently monitored and depending on the application should be replaced approximately once per year depending on usage, mileage and sailing conditions.
WHAT TO LOOK FOR WHEN INSPECTING ROD RIGGING
Cracks in rigging components, especially cracks that are orientated transverse to the load, are sign of impending failure. Cracks can be found using visual inspection, a magnifier, or by dye penetrate testing. This techniques are recommended, but other professional testing techniques available are X-ray testing, eddy current testing and ultrasonic testing, which allows you to inspect rod heads for transverse cracks in closed fittings.
For visual inspection, the rod or fittings must be cleaned or polished to expose the cracks. Rusty areas frequently indicate cracks underneath. In addition to cracks, you should look for corrosion, pitting, black streaks, rust and visible wear. Any areas showing discoloration or potential corrosion should be thoroughly cleaned and inspected. If any evidence of pitting, corrosion or wear remains after this cleaning, please consult us. Pitting, corrosion or visible wear could require re-heading, replacement of the rod or replacement of associated fittings.
Proper alignment to the load is also very important to generate a good working life for any rigging. Misalignment of fittings, caused by intereference or bends, should be checked. Kinks or bends in rod rigging result in increased local stress and can dramatically reduce its life. If a fitting or rod has operated in a bent, kinked or misaligned condition, is recommended to replace it, as a damage due to cycling cannot be easily evaluated. If a rod is bent and then straightened before further service, depending on the severity of the bend, it could be used again to provide a normal working life. This is a judgment call, and you should consult us considering this issue.