Day 83 – Boom Topping Lift Down – Again
Sun 6 Mar 2022 13:49
Course: NE Speed: 6 knots
Wind: WSW, F6 Sea: rough
Swell: WSW 4 m
Weather: mostly cloudy, mild
Day’s Run: 155 nm
I had a little afternoon siesta late yesterday afternoon to catch up on some sleep. I did not arise until close to sunset and on looking around was disheartened to see the boom topping lift once again trailing astern of the end of the boom. It was and is too windy and rough to contemplate going aloft to repair it but the forecast is for the winds to ease tomorrow and hopefully the seas will subside along with the wind to make the job manageable. For now I will leave things be.
Clearly, we have a problem with this topping lift, with one shackle failure, one block failure, and this time I believe the shackle has failed again. The first failure I attribute to the shackle pin working its way loose, the second due to corrosion in the block’s cheek, and this time I have little idea. I suspect that it was due to the shackle overloading and failing when the end of the boom drags in the water when Sylph takes a heavy roll. Normally when this happens the boom wants to drag aft and from my observations wants to lift up out of the water. This upward movement does not load up the topping lift, rather it places a big load on the vang-preventer. This strain on the vang-preventer has in turn caused me concern because the vang-preventer is attached to the boom about a third of the way aft from the gooseneck, which puts huge force on the boom at this point and I worry that is might fracture the boom. To relieve this load I attach a separate preventer from the end of the boom to a cleat on the foredeck. It is made of nylon so it acts like a big rubber band and the theory is prevents any excess shock loads when the boom does drag through the water. So what has gone wrong?
My suspicion at this stage is that I have miscalculated the geometry of the loads on these various lines and that as the boom drags through the water, with the preventer attached, instead of the boom lifting out of the water, the preventer perhaps pulls the boom down and thus loads up the topping lift. I had checked the load on the topping lift several times during the day and it was relatively loose with the triple reefed mainsail taking most of the load. However, regardless of the cause, I am glad that the shackle failed rather than an excessive load damaging the mast (though I won’t know for sure whether the mast hasn’t suffered any damage until I can get aloft to inspect it). Re-attaching the block to the masthead is going to be another of those challenging moments (i.e. right royal pain ...), moments I would rather do without, but importantly it isn’t a ship stopper provided I don’t damage the crew in the process of going aloft. But that is a problem for tomorrow.
For now we are heading in somewhat the wrong direction, NE rather than ESE. I have been contemplating a gybe for some time, but figure if I continue more to the north than we will likely get back into the influence of the high pressure system that little bit sooner, and hopefully lighter winds and smoother seas. Ultimately, it does not matter that much just yet. We are still a fair way from South Africa and the Agulhas current which I want to steer well clear of, including staying south of the large-scale cyclonic meanders known as ‘Natal pulses’. To do this I reckon I need to pass Cape of Good Hope south of 42 S. So, taking all this into account, I reckon I can continue NE for the next day, fix the topping lift tomorrow, and then gybe and continue ESE to pass well south of Cape of Good Hope and hopefully still remain within the westerly air stream.
As long as no critical systems are broken, including the crew, then the loss of a few hours in passage time is not going to make any difference to the success of our voyage.
All is well.