Boom vang repair

[Danny Jo]

On to the next job - repair of a seriously corroded boom vang.

The picture shows the lower end of Freestyle's twenty-year-old boom vang. Both the tube and the casting are aluminium alloy, very susceptible to corrosion under the right (or rather wrong) conditions. But what conditions have caused this? The brown staining is presumably ferrous/ferric oxide. Is iron the catalyst for this corrosion? And where has the iron come from? The rigger suggested that the steel mandrel in the blind rivet is the culprit, and reported that he always knocked this out with a punch. What does the panel think?

 

[Ian_Edwards]

Hi,
The tube and casting look exactly like the one I’ve just repaired on my Dufour 40, they are made by Sparcraft (France) and the UK agent is Eurospar in Plymouth. If it’s the same as mine there is a steel coil spring inside the tube which supports the boom, it looks like the steel spring has corroded, it’s just painted, and set up a corrosion cell with the Al tube.
If you drill out the pop rivets and pull it apart you’ll soon see what’s wrong, mine has a tube within a tube, with the spring in side that.
I’d also talk to Adrian Hood at Eurospar +44 (0) 1 752 550 550, I’d guess that most of the components are still available, especially the Al tubes.

 

[Danny Jo]

Thanks for the suggestion and the contact details.

This may not be the same type as the one you describe - the tube shown slides inside a large tube attached to the boom in such a way that the vang prevents the boom falling much below the horizontal. Only the line around the blocks prevents the boom from rising. Since I've had the boat it has not had any functioning shock absorption mechanism.

 

[Ian_Edwards]

Hi,
I've posted some pictures, it looks very similar, even down to the detail of the casting. It’s a very common design, with larger tube at the top, which slides over a smaller tube, but it’s actually has 4 tubes to keep the whole thing concentric. I found it very easy to open it up and fix it, Adrian gave very good advice on how to make the Boon Vang more robust, and I covered the spring with waterproof grease to help stop the corrosion.
http://www.sparcraft.com/uk/main.asp?url...ult.asp&f=2,93,,120,a
Hope this helps.

IMG]http://i296.photobucket.com/albums/mm165/Eynhallow/IMG00227.jpg[/IMG]