So that was a very interesting detail I discovered by chance during last edition of Boot Duesseldorf. Excess was the one and only catamaran brand exhibiting a live boat in full size and because of this there was usually a long queue at her stern with people wanting so see the boat. Being an exhibitor myself I was happy not having to wait in line, because from down walkway-level I could spot something unusual at her. There, at the boom end … can you spot it too?
Being part of the standard equipment of the Excess 11 since almost a year now, the guys from the shipyard told me that these two parts are kind of „… mainsheet fuses“. It was impossible for me to research the proper name of this part. I crawled the catalogue of the manufacturer – Corderie Lancelin – and also asked as many people as I could find. In this, the best name we can come up for these things was „mainsheet fuse“. In this I am sorry I haven´t got the real description. But anyway, I like this name because frankly, it´s basically doing exactly what we call it: It is a fuse for the mainsheet.
Instant load relief for the mainsail
Now, what are these parts good for?, you may ask. And why am I bothering to make a full article about this? Well, it´s pretty simple: The Excess 11 has two mainsheet ropes mounting to the so-called „double mainsheet system“ or „twin mainsheet system“. This may sound a bit odd but it actually has so many advantages, especially when you are sailing singlehanded or when doing maneuvers (especially the gybe) alone. If you want to know more about these twin main sheets, check out my #excesscatamaran articles. Okay, back to the boat:
As you can see on the picture above, a red and a green main sheet are put on the boom´s head. That´s so kind of the shipyard, the colors refer to the left or right locations of the sheets so you don´t get confused when working the lines later on the winch. Now, imagine a weather situation with ongoing strong winds – but still below the reefing. If a hard gust suddenly hits your boat, you want to open the mainsheet (or the traveler) to get off pressure from the main, reduce the instant hard heeling. On a catamaran that´s much more urgent as it will flip over much easier. The mainsheet fuse is your „jump to the jammer and release the main“-mechanism.
How does the „mainsheet fuse“ work?
On luxury sailing yachts this mechanism is part of a digital programming. These „panic buttons“ can be triggered either automatically or by … well, hitting the button manually. The Lancelin-fuse works purely mechanical and in this it´s automatic. You just don´t have to do anything – install and forget, basically.
The „fuse“ is a fist-thick cylinder-sized item. It consists of an outer layer which feels like some sort of neoprene. It is put over a (Dyneema?) rope that is coiled up and held together by an ordinary household rubber band. That´s it, nothing fancy, nothing that secretive. As the fuses installed at the boom end of the Excess 11 has a label stating „500 kilograms“, I suppose, there are bigger and smaller fuse. The kilogram-number refers to the breaking point, meaning the maximum load this fuse can take before being triggered. In our case, as said, half a ton.
So, when sailing in strong wind conditions with occasional gusts, you can sail the boat close hauled beating upwind without any problem. If a gust hits the rigging and you are too late in relieving the mainsheet/traveler, over a load of 500 kilograms, the rubber-band and neoprene cover will fail and the the white Dyneema is released. This, extending out for, I guess, one meter or even 1.50 metres. As I wasn´t allowed to uncoil the whole thing, that´s just an educated guess. Anyway: by extending the rope inside of the fuse the boom opens the sail instantly relieving the the boat of excessive pressure.
Could this be something for your boat?
There are several things about this mechanism which I really like. First: The length of the „fuse“-rope is finite so that the boom won´t be released fully. Often in overreaction in those gusty pressings the mainsheet is let loose completely which can cause the boom to crash into the rigging. In a grow-up gust this can damage the shrouds severly. Secondly, I love the simplicity of this system. It´s really like a fuse: Fail safe and triggers automatically.
The third cool thing about it is the fact that it will buy some time for the skilled skipper to come up on deck in those classic situations: When the unexperienced have to stand their watch and you try to catch some sleep. Now you can lay down in peace knowing that in case something happens the worst pressure will be dealt with by this „fuse“. So. Is this something for your boat? Maybe. If so, all we need would be to know the real name of this product … feel free to comment.
More interesting sailing accessories:
Offshore safety equipment: Jackstays
First Aid-kit for sailboats
Sea-sickness cure: Which type are you?