Boom & blocks

Question: Mike, what do you mean by "Best attached on webbing loops" ? Do you mean that all blocks of the main sheet on the boom should be attached with webbing loops which it is not currently the case on our boats
Answer: The webbing loops support the blocks - they wrap around the boom. The early aluminium booms have a small metal fitting attached on the underside of the boom with rivets. In extreme conditions the metal can fail between the rivets and the boom breaks.
The webbing alternative is simply a loop to which the blocks are attached and takes the load over the top of the boom.
I'll take a photograph this weekend and send it to you.
As an alternative you can use rope wrapped around the boom a couple of times and with each end knotted through the existing metal fitting - but with the block suspended.
Again I'll try and find a boat with this method to photograph.
Regards - Mike Lyons

Carbon Boom failure

Have not suffered personally and there should be no reason if the end fittings are properly fitted. The Superspars end pieces are certainly fit for purpose and I think much better than the Proctor ones as they allow you to stow the halyard inside the boom if you want.

I think the problem arises because when made up hard 'monel' rivets are frequently used to attach the gooseneck boom end fitting into the end of the carbon tube. The added pressure needed to 'pop' them crushes the laminate and in time this leads to tube failure. This heavy duty type of rivet is simply not needed for strength.
All that is needed is a way of locating the item into the boom end - none of the loading is through these rivets - its through the end of the boom tube and through the fitting into the gooseneck / mast. The trouble is that these particular fixings reduce the strength of the carbon tube in the area where the load is transferred. I'm of the view that monel rivets are used simply because they are used elsewhere
It must be worth trying either the use of 'soft' alloy rivets which will not lead to crushing of the carbon or a couple of small self-tappers with guide holes carefully sized. These approaches will not lead to crushing.
If this is insufficient then the lay up needs a bit of carbon reinforcement to increase the 'hoop' strength at that end in future standard issue booms. It should be possible to fix or improve pre-existing tubes by using epoxy like SP or West and some glass fibre tape looped around the tube end (on the outside).
As for alloy tubes - there have been hundreds of failures and the insurance company's must wonder about the supplier of them as they are of inferior design. If you have an alloy tube (Mk1 boats only) check to see if its one of the earlier types with beckets for the mainsheet blocks riveted on the underside. They WILL cause the boom to break at some point - my opinion is that this practice was always wrong. In strong winds the underside of the boom is in great tension (and the top in compression) The tube is then compromised by drilling two bloody great holes in it about 2 cm apart - in the exact area of maximum compression to attach the beckets. This was always asking for trouble.
These rivets are inevitably made of a dissimilar metal to the boom and any becket and when the holes are drilled the anodising protection is removed - result very rapid corrosion and mechanical 'working' of the fastenings leading to eventual breakage. No real problem with rivets in the top - that area is in compression and all the single rivet is asked to do is locate the webbing in these later booms - not support the full boom.
Those who have suffered carbon boom breakage's - please forward any info regarding manufacturer (Topper have used THREE different boom suppliers in the past 2-3 years !) also type of end fitting, rivets used and whether your boat has a cascade kicker or 'strut' type - we'll see if there are any patterns or common factors.
Regards - Mike Lyons '654'