Spars, Mast Hinge, Part 9: Cutting the Mast

The base of the mast, just after the cut
Having installed the new G-10 mast step and the appropriate hinge components on Oystercatcher, my Ericson 25, I now needed to cut the base of the mast. This subtraction, so to speak, from the base of the mast would account for the height I had added to the deck of the boat through the installation of the G-10 and the hinge components.
To make the cut, I began by setting up a temporary cutting table in the yard.
Before setting the miter saw on the table, I made sure that it was level in all directions.
I then double-checked my earlier measurements.
An important factor that I had had to consider all along was the location of the cutout for the centerboard line.
I needed to cut off enough of the mast to remove entirely this original, centerboard line cutout. Otherwise, it seemed to me, the base of the mast would be structurally compromised.
Fortunately, according the calculations I had made before I ever ordered the G-10 for the new mast step, if I constructed a new step at least 1.5 inches in height, then I could remove 2.75 inches from the base of the mast. The top of the centerboard line cutout was at 2.75 inches, so this was one important reason why I decided to construct the new step to this 1.5 inch height. The other important reason, which I discussed in an earlier posting, was that I needed to build up the step enough to where the mast would clear the forward hatch when it was in the process of being stepped.
The silicon bead that the previous owner had applied around the centerboard line cutout was an annoyance, so I did my best to remove it before making the cut. This guy apparently thought that the silicone would help divert rainwater from entering the mast. I remember that he also had some plastic flap sloppily taped in this area.
If you click on the picture below, you'll see my pencil mark notes: "with 1/2 inch G-10," "with 1 inch G-10," and "with 1.5 inch G-10."
Another thing that I did before making the cut was to create a pattern for the new centerboard line cutout that I would need to make.

2.75 inches.
2.75 inches. I only had one chance to get it right.
Before making the cut, I decided to take a picture of these markings that would be forever removed from the mast. I've never been able to decode them.
The time had now come for me to put the miter saw on the table. Again I checked for level.

I also checked to make sure that the mast itself was level. It of course was not. Notice the stack of scrap pieces of 2 x 4 material on the second sawhorse.

Without a doubt, I did more preparation and more thinking about this cut than any other in my entire life. My boatyard owner friend who works with aluminum on a daily basis had assured me that my approach to cutting the mast in this backyard, makeshift fashion was a sound one.
Reining in my concerns, I slowly gripped the mast with my left hand, and with one resolute motion I pushed the saw blade through the aluminum from one end to the other.
The cut was clean. All evidence of the old centerboard line cutout was gone.
I deburred the aluminum with a piece of sandpaper.

Now I prepared to create the new centerboard line cutout.
I decided that the best way to replicate the original cutout would be to use a hole saw. Therefore, I pulled out my homemade gauge and scribed a circle.
I used a center hole punch to mark it.
Then I drilled a small pilot hole.
I used this to guide me in my cutting of the hole with the hole saw. For some reason we call this thing a hole saw, even though it's more of a large drill bit.
The hole was clean in appearance, but it had a significant number of burrs.
I first used my fiberglass cutting bit on my Dremel to deburr it.
This wasn't the right attachment for the job. The small grinding wheel did better, but it was still not ideal.
Now I needed to create the lower part of the cutout. It felt awkward trying to do it with the jigsaw.
Therefore, I decided to use the drill. Again, I marked the spot with the center hole punch.

I could only drill so far before the drill bit started to walk into the large hole.
The jigsaw was now more cooperative. I used a Bosch T118B blade for this, just as I did on other projects that required me to cut aluminum.

I finished off the job with the fiberglass cutting bit in the Dremel.
The small, 50 grit sanding drum was better than anything else at deburring the aluminum.
Now that these tasks were behind me, I could focus on the installation of the top of the mast hinge to the new base of the mast. I address this part of the project in my tenth and final posting.

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