I knew I was in trouble when I tried to unbolt the mast step on my Columbia 26. I had been working on a complete restoration and needed to remove the mast step to repaint the deck. A Columbia 26 has a deck stepped mast. The mast rides on a cast aluminum mast step. That was the start of the problem.
An aluminum mast step coupled with an aluminum mast sounds like a good idea and it was. That is, until a PO (previous owner) decided to add a stainless steel mast base organizer under the aluminum mast step casting.
A mast base organizer is a piece of stainless steel with four ears, one on each side of the rectangular center. The ears are turned up at an angle and have holes spaced in them. The holes are for attaching turning blocks for the various lines coming off the mast. The turning blocks then aim the lines at their respective winches or cleats.
While they are handy things to have, the combination of aluminum castings, stainless steel and saltwater is not a good combination. The less noble metal, in this case the cast aluminum mast base, corrodes. And this one had done so. My first inkling of trouble was the fact that the fasteners were locked in corrosion and had to be cut away.
Once the mast base was free, I could tell the extent of the corrosion. The center of the casting was designed to fit inside the base of the mast. The bottom edge of the casting was a lip about a quarter of an inch thick and about three-eighths of an inch wide. The full weight of the mast is born by this lip. As I removed the mast base, the majority of the lip fell away in white powder and small pieces of aluminum. It would have to be replaced.
Although the boat was built in 1965, I have found many of the replacement parts I needed for the restoration still available. I found exact replacements spreaders, for example. So the search for a replacement casting began. I checked every Internet rigging site I could find. I found many similar castings but couldn’t find the exact one. I would need to modify an already expensive casting to fit my mast.
While I certainly won’t own this boat forever, I didn’t like the idea of replacing the aluminum casting with another that was sure to start corroding as soon as saltwater hit it. I decided to design a new mast step, one that would be compatible with the stainless steel mast organizer (which I liked and wanted to keep).
My first though was a product called Micarta. This is a material that was developed in the early years of plastics, before WW-II as a mater of fact. Micarta is composed of many layers of canvas or other fabric, impregnated with Bakelite plastic and cured into a solid sheet. It is available in a wide variety of thicknesses, colors and specifications.
My first design, on paper, utilized a piece of quarter inch thick Micarta as a base with a thicker piece of Micarta cut to the inner profile of the mast. This thicker piece would center the mast while the thinner piece supported the weight of the mast. Instead of being a single piece, the two pieces would be bolted, along with the mast base organizer, through the cabin top as was the original set-up.
I didn’t want to buy the Micarta from a regular distributor as they only sell large size pieces, far larger than I had any need for. So I turned to my old friend eBay. A search on Micarta turned up several sellers who offered small off-cuts of the material at very reasonable prices.
While surfing one of this sites, I found a reference to another material, G-10 fiberglass. It turns out that this material is made much the same way that Micarta is only with different materials. G-10 is made from fiberglass cloth instead of canvas or linen and uses epoxy resin as a binder. The result is a strong, dense sheet with excellent compressive strength, just what you need with a mast sitting on top of it.
While there was a plentiful supply of inexpensive quarter inch thick pieces at rock-bottom prices, the thicker pieces, of either Micarta or G-10, were harder to find and much more expensive. Then I realized that the compressive strength of G-10 or Micarta weren’t needed for the center of the step, the piece that located the mast.
So I changed my search and quickly found a small piece of StarBoard marine lumber. It was an inch and a half thick and would be ideal for the center piece and easy to work to boot.
The actual building of the new mast step was almost anticlimactic. The quarter inch G-10 was easy to cut to size with a metal cutting blade in my Bosch saber saw. A few quick licks with a belt sander smoothed the edges and rounded the corners.
I had traced around the remnants of the mast base to get the outline of the center piece. After cutting the tracing down to size, I drew in the center lines to locate the fastener and wiring holes and then glued the paper template to the StarBoard. I switched saber saw blades to a coarser toothed one that was long enough to cut the full inch and a half thickness of the StarBoard.
I had to cut the StarBoard very slowly to allow the chips to clear the deep cut. After I had it cut out, I sanded the edges to remove the saw marks and generally smooth up all the edges. I made a few trial fits to get a good tight fit in the mast base.
Probably the hardest part of construction was drilling straight holes through an inch and a half of StarBoard with out a drill press. In fact, I ended up making the mounting bolt holes into slots so I could get the piece properly centered. Once centered, I temporarily bolted the three pieces together and then drilled the center hole for the wiring.
All-in-all, it took me about half a day to cut the parts out and assemble the unit. It took far longer to locate the materials and get them shipped in. However, the end result is a mast base that won’t corrode and at a price of about a third what the aluminum casting would have cost, not counting the machine work required to modify the casting.
Capt’n Pauley
Mitt, Glad you found the post helpful. Tried to view the pics but it said they were private and wouldn't let me access them, I'd like to see them and maybe post some to show others what you've done.
Take care!
Capt'n Pauley
Posted by: Capt'n Pauley | July 26, 2009 at 12:55 AM
Paul, many thanks for your article, I could not have done this without you, thought you'd like to see my version:
http://www.flickr.com/photos/mittdawson/3752982401/sizes/l/in/set-72157621810991518/
Posted by: Mitt Dawson | July 26, 2009 at 12:24 AM