Coming from the unibody I had kept the habit of putting, on Tao, a hoist used boom by wind. It was struck between the central cleat and a bridge to the 2/3 the back of the boom... until the day when the cleat pulled out... and a buddy has folded its boom with the same technical!!! As you learn by mistakes and especially what they cost us, this to triggered a reflection on the adaptation of this technique for a catamaran... which does not cash the oversales and other gitant errors! So here is 6 months I'm sailing downwind with a "Bungee" boom...
The problem to be solved by wind:
a) moderate wind and seas: the boom has jolts from the bottom up, and back and forth, What is noisy, but especially prematurely use the Mule lives and all parts that wriggling in the process.
b) strong wind and rough sea: a best-selling in a low point... the sail deflates, mollie listening and the boom down... then at the top of the next wave, then the boat to idle, the wind comes back with force which inflates the sail suddenly, tightens violently listening and gives a great shaking in the rigging.
c) Despite the safety cap and adjustment of auto-pilot you are never safe from a start to the surge or stall driver which would cause a jibe... and Hello damage!
Therefore, a system for:
1) dampen the movement of the boom, but without blocking them in order to allow the boom go back and let escape the sail from the top
2) prevent a hinged jibe
My solution is a "Bungee" shock absorber / restraint of boom:
An elastic cushion... and a strop to restrain the boom. So several elastic large-diameter tips (bungee) with parallel a strop in Dynema which serves as safety stop. This will need to be struck between a cleat to the back of the boat and a secure bridge (or strap) on the boom, the closest possible to listen hoist.
Realization of the "Bungee":
What it takes:
– 5 meters from end elastic 10mm diameter (the biggest I found in St Martin)
– 2 meters from end to Dynema diameter 8mm
– two shackles lyre of 8mm
– 50 centimeters of diameter 4centimetres protection sheath (enough to pass 7 the elastic end strands) -the one in the photo was not large enough!
– Restraint of boom hoist
– Textile shackles and hanging systems adapted
1) Make an eye at one end of the elastic end.
For this, fold it inward on a length of 20cm and make 3 surliures with big wire to sail by taking care of stung several times through the two layers of the elastic end.
4) Adjust the length of the loops so that at rest they exceed a few centimetres of the sheath.
5) Pull on the 5 strands to get them out of the sheath of 20 30 cm. While keeping tension on the elastic, with a piece of 8mm to tie a capstan autour of 5 possible closer strands of the sheath. Hit the other end of the line on a point fixed and tender. Release the tension on the elastic.
8) Pass each end of the strop in a Manila lyre.
This is the "Bungee" is ready.
It remains more to hit one end on a textile Manila passed twice on a rear stop and put your hoist of restraint of boom between the other end of the "Bungee" and BOOM (as close as possible to listen to great sailing).
Of course, your comments, ideas to improve this system and other suggestions are encouraged...