Building a boom

The Sage 17 boom, made by Dwyer Aluminum Mast Company, arrives at the shop as a 8’3″ long anodized aluminum tube.

The boom begins as a aluminum tube.

The boom begins as a aluminum tube.

Before installing hardware I first  identify the boom ends, gooseneck and aft, and the top using tape and a marker.  Doing this assures I don’t install hardware in the incorrect location.

The first part installed are the bails, made by Garhauer Marine, for the vang and mainsheet.  These fittings work really well to align the rest of the hardware, and keep the boom from rolling as a drill the mounting holes.

Boom bails installed.

Boom bails installed.

Mounting holes for the outhaul and main’s clew reefing lines are cut & drilled.  The hardware used is from Harken, Sea Dog Garhauer, and Forespar.

holes for fasteners

The boom is cut and drilled so the hardware can be mounted.

Sage 17’s outhaul is internal to the boom.  The system uses a two Harken blocks, a length of wire and a length of 1/4″ double braid line.

Outhaul line goes into the boom after being lead through a bock.  the block will be pop-riveted in place.

Outhaul line goes into the boom after being lead through a bock. the block will be pop-riveted in place.

At the aft end of the boom the outhaul line is lead through a block.  this block is attached to a wire that is lead through the block that is installed at the aft-top portion of the boom.

At the aft end of the boom the outhaul line is lead through a block. this block is attached to a wire that is lead through the block that is installed at the aft-top portion of the boom.

This headboard shackle is attached to the main's clew grommet.  The black strap keeps the clew close to the boom and slides easily as the main's draft is adjusted.

This headboard shackle will be attached to the main’s clew grommet. The black strap keeps the clew close to the boom and slides easily as the main’s draft is adjusted.

The outhaul line is shaken down the inside of the boom and once it reaches the gooseneck end is tied off using a figure-eight knot.

The outhaul line is shaken down to the gooseneck end of the boom.

The outhaul line is secured at the gooseneck/mast end of the boom by running it through a hole and then tying in a figure-eight knot.

The outhaul line is secured at the gooseneck/mast end of the boom by running it through a hole and then tying in a figure-eight knot.

Once all the mounting holes have been made the hardware is installed using stainless pop (blind) rivets.  Stainless rivets must be installed using a pneumatic pop rivet gun, as their strength is to great for the usual hand riveter.

After the hardware is installed the boom ends are assembled.  Sage 17’s boom end fittings are custom and manufactured by Spyderco.

The assembled boom ends.  The black portions are aluminum and hard black anodized.  The attached hardware is stainless steel.

The assembled boom ends. The black portions are aluminum and hard black anodized. The attached hardware is stainless steel.

The boom ends fittings are inserted into the boom and then pop riveted in place.  It is important to first shake out all the metal scrap before putting on the last end fitting.

This is the boom end that has the universal hardware installed.  The allows the boom to twist when attached to the mast's gooseneck fitting.

This is the boom end that has the universal hardware installed. The allows the boom to twist when attached to the mast’s gooseneck fitting.

After the last end fitting is installed the boom needs to be shaken to assure all the scrap has been removed.  If not you will hear clinks and clanks as the metal bits roll from one of the the boom to the other.  During the ‘hole making process’ I drill an ‘extra’ opening at the bottom of the aft end of the boom so I can shake out any last bits of metal.

The boom is now done and ready for sailing!

A completed boom wrapped in plastic for protection during delivery.

A completed boom wrapped in plastic for protection during delivery.

 

– Dave

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