Wednesday, 5 June 2013

The new 300 boom

A post that I fear will only be of interest to 300 sailors!

I bought a new boom for the 300 a month ago, the class has moved to full carbon spars and updated the aluminum section boom.  Unfortunately the first fitting of the boom wasn't great, it transpired that holes had been drilled in the wrong place by the manufacturer, so I've been having a dialogue with LDC about the best way forward.  Anyway, I've been given carte blanche to drill holes in the boom to make it work, previously a problem as the boom came with a sticker saying "Drilling holes invalidates warranty". And LDC are discussing with Selden and looking at a replacement in the longer term.

So this is what I've done.  First the vang arms needed to be moved forward:

The bolt is now in the middle of the local reinforcement on the boom.  Relocating the bolt gave me cause for concern, due to the proximity of the old holes.  But I've maxed out the vang and it seems OK - there is a lot of carbon in that part of the boom.

Next I relocated the block that takes the vang and downhaul at the front of the boom. Rather than drill holes for a new eye, I ended up going with some rather precise brummel splicing to use dyneema to hold the block in place, thereby distributing the loads over the full cross section rather than two rivets.  The outhaul eye under the boom keeps the dyneema place.  The vang and downhaul control lines are aligned to the mast.  Also took the strops to the Frankenstein bolt as opposed to holes on the boom, again minimising local stresses on the boom.

This is the final set up :

Much less travel is required on the mast to get the same mast deflection, which will hopefully translate into more space under the boom.  Downside is that I'll have to work out new vang settings, but thats not such a hardship.

First outing on Thursday at TISC.

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