New Rig #3 The Mast Base

The new mast is 4" by 1/8" T6061 aluminum as specified by the Wharrams. It is 25' in total length, as opposed to 21' in the plans, to give me a bit of clearance under the main for general comfort, and to allow me to fly a large spinnaker in light air. Aluminum tube comes in 20' lengths, so the completed mast is in two sections sleeved together.

 

This first picture shows the arrangement inside the mast base. A one inch aluminum tube is welded to 6 inches of mast section that has been cut to fit tightly inside the mast. Rather than weld it all together (which causes hard spots and other issues), the welded sleeve is riveted with 1/4" 316 rivets through the mast and additional 1/8" aluminum plates on the outside of the mast. So the 1/4" rivets are going through a total of 3/8" of aluminum on each side of the mast pivot.

 

This picture shows the mast mountings which were made with hand tools from 1/2" by 5" T6061 aluminum angle. They are bolted through the center beam with 5/16" 316 bolts. The mast pivot pin is made from a 1/2" 316 bolt and is secured with split pins. You can just see the nylon washers that are on the pin to stop the mast working against the mount. You can also see the outside plates supporting the pivot tube in the mast in this picture.

 

Here you can see the new mast base mounted. Note the rear of the mast bottom is cut away to allow the mast to rotate without hitting the beam and to give space for the mast wiring to exit.

Here the mast base is revealed as a short 5' section that will be sleeved to the rest of the mast after the base is installed. You don't often see a torque wrench on a Wharram.

 

The base fitting is all done and lifted up. The slots are for the yet-to-be fitted internal halyard roller fittings and the numerous holes are the pre-drilled mountings for the halyard horn cleats. Yes, it is a very robust set up, but is still light in weight.

 

Here is how it looks in action