Mast

The last two months have been occupied by getting work done on the house, and with a few house projects looking good, I found a bit of time to delve back into the boat.

Having accumulated some parts for the mast over the last few months, I felt I owed it to myself to do some work  fabricating the mast. The mast will be used for hoisting our tender to the roof along with any other heavy item we might want to lift. The radar dome and some other electronic gear will find a home in the mast. The mast will also support the future paravane rig along with a possible steady sail.
 
The mast is being fabricated out of six inch schedule 40 aluminum pipe with the boom being four inch schedule forty aluminum pipe. The six inch mast will be deck stepped with a fore stay and two shrouds on both port and starboard. Because their will be no back stay, two of the shrouds will be aft of 90 degrees to on both port and starboard, working with the fore stay to hold everything up. All the heavy framing and reinforcing was done on the super structure during the build.

The mast will be pinned to the step using two 1.25" stainless pins. The load bearing pin will support the mast with heavy bushings welded in to the mast while the locking pin will just lock through a bore in the mast. Because the mast will have the ability to quickly be laid down, clearance needs to be left under the mast between the mast and deck so it can pivot. While there wont be much of a compression load on the mast until a paravane rig is installed, I still plan on creating easily removed solid blocking under the mast to deal with future loading.

The first order of business was turning the bushings for the load bearing pin that will be  used in the mast step. The pins are 1.25" SS, and like I said above, the bushing will be welded in to the  mast. For bushing stock I found some heavy walled tube with an ID of 1.23" and a wall thickness of 3/8". Realizing the bore of the bushings are going to distort due to welding them in the mast, I found myself guessing at how far over I had to bore the bushings. Settling on .006 ( six thousandths ) over I have a feeling in my gut Ill have to re bore after the welding. The bushings are 1.5" long.

The next item to be fabricated is the joint that allows the mast to pivot up and down along with left to right. I think the proper name for this part is called a mast car. All the parts were made on my lathe including boring the 1.25" round bar to create the 3" long tube for the part. The leaf for the part was cut from 1/2" stainless plate and was TIG welded to the tube. Having bored the tube to a final dimension of .003 over ( the pin is 3/4") I was not surprised when the pin was not fitting well after I welded the part. Chucking the part back in the lathe to clean up the bore was expected and I ended up having to bore about .003 from the bore to get back the nice fit I had before the weld ( Im sitting here wondering how Im going to clean up the bore for the mast step bushings after that weld).

The hinge ears for the boom are fabricated from 1/2" aluminum plate. I notched the 4" boom to accept the 1/2" hinge ears using a circular saw and cleaned the notch up with rotary burrs and disc grinders. The bores for the hinge pin was drilled in my mill and reamed to a final diameter of 3/4". The hinge pin was turned to .001 under for an nice fit. Because I dont have a spool gun, all the welds are TIG, and required heavy clamping, and lots of tacking to keep alignment true due to the high heat TIG creates.

Once I can get back in to the boat yard ( their closed until the 5th) to measure the step, and how long the boom will be, Ill cut the boom to length and begin welding in the bushing for the mast step. Depending on how creative I get with the aft handrail on the roof deck, I can almost handle a 13 tender. 12 will be a better fit, and Im pretty sure thats the size tender we want. That being said, the boom will be somewhere in the neighborhood of 14 long. The beam of the roof is about 15 8", so that leaves me about 6 2" of boom to unload a tender with a beam of 5.

As of today, the plan to do all this hoisting is with two electric winches. One winch for the load, and another winch for the boom. 2000 lbs electric winches pull about 100 amps under full load. Instead of trying to run heavy cables to the winches, Ill probably build a battery box and locate it next to the mast step. We could have a small charger in the wheel house, and run leads from the wheel house to the winch battery to keep the charge.
 
So far this is a fun project and like all things boat build, much more work than Id anticipated. I have to do some research on cable and cable connectors to source some more parts, but that shouldnt be to hateful. I can for sure say its been nice getting to do some lathe work and TIG welding on nice clean metal.

Cheers

   

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