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How do I fix a saggy boom?

2019 May 1

Dear Boat Doctor,

My Selden boom vang doesn’t seem to hold up my boom any more. It was OK before I installed the main, but now the boom just sags. For now, I have resigned myself to holding up the boom with a spare halyard but I’d like a more permanent solution.

Gary Krieger

s/v Freed Spirit

Dear Gary,

This problem in which the vang is just strong enough to carry the boom but the weight of the main puts it over the edge isn’t uncommon. Every rigid vang has what is effectively a spring in it. In some cases this is an actual spring, but in the case of the Selden Rodkicker there is a gas strut. This gas strut is very much like the strut that holds up the hatch on a hatchback car. Over time the seals in the strut wear out and it loses strength. The fix is to replace the strut.

The easiest place to get a new strut is directly from a Selden dealer. If you’re a little more adventurous and looking to save a few pennies, you can source a strut from the industrial market. You just need to match the physical specifications of the cylinder with one from a site like McMaster-Carr. You can save some money with a non-Selden strut, but needless to say you’ll get no further support from Selden.

Next you need to remove the vang from the boom to work on it. Support the boom and remove the upper clevis on the vang. To separate the vang tubes just push in on the little black “buttons” on the top and bottom of the vang and pull the smaller tube out. You will see the gas strut attached to the end of the smaller tube. Remove the strut from the smaller tube in the same way by pushing the buttons.

The strut should be free of the aluminum tubes and you’ll see a black plastic fitting on each end. Just unthread the fittings and put them on your new strut.

You can now replace the strut and reverse your steps, being sure to put the strut in with the big end of the strut attached to the smaller aluminum tube.  

You’ll find that the vang is longer with the new strut in it. In order to reattach it to the boom you’ll need to compress it with the tackle.  The new strut will be pretty strong and you may need to use a winch. Then replace the clevis pin.

If you need more guidance, there are several videos online that cover the process.