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Systems:  Mast Step

I decided to install the mast step on the keel, rather than engineer a deck step.  Since I wasn't using an existing spar, I didn't have to worry about the extra length required to extend to the bilge, since I could just account for that when ordering a mast later.  A keel-stepped mast made the most sense for this application.

One of the pitfalls of bilge-stepped masts is that the continuous presence of water, or at least dampness, often wreaks havoc with the typical aluminum or stainless steel mast steps.  To counter this, I planned to build up the step rather high above the bottom of the bilge.  For strength, and to prevent any possibility of corrosion  (if metal) or rot/deterioration (if wood), I chose to built the basis for the step out of solid fiberglass, molded in place.

The area in which the mast will step was narrow, and with the built-up step there was the real chance of bilge water ending up trapped on the forward side of the new structure with nowhere to go.  Therefore, I had to plan for limbers to pass beneath the new step.  I would have used lengths of PVC pipe, similar to what I did on the midships bulkhead, but all I had around was the large 1-1/2" ID pipe, which was too big for the application.  Therefore, I improvised, and decided to simply mold the limbers in place.

To do this, I cut some strips of foam into 1" square rectangles, each about 12" long, and rounded over the corners with some sandpaper to make roughly circular profiles.  I glued these in place at the corners of the bilge in way of the mast step.  The point of this exercise was to basically mold the limber openings around the foam; when all is said and done, the foam would be removed, leaving only the 1" diameter openings passing beneath the outer edges of the new mast step platform.

With some thickened epoxy, I filled in the gaps on the outer and inner edges of the foam, and then cut several layers of 24 oz. biaxial fabric to fit the trapezoidal shape between the foam, over about 7" of its length (the length of my built-up step area).  I wet out a number of layers of the material and rolled them out in place between the foam.  I let this cure overnight.

Over the next couple days, I added layers of fiberglass to the area until the center step area was built up nearly to the tops of the foam limber forms.  Then, I made some thickened epoxy fillets as needed, and laminated some wider strips of biaxial fabric over the entire area and up the hull several inches on each side, thereby beginning the encapsulation of the foam.

Over the next couple weeks, I slowly built up the mast step base.  Once I had a solid base of fiberglass cloth, I used some epoxy filler to smooth and begin to level the surface, eventually achieving a level laminate from side to side across the foam limber molds.  Then, I applied more fiberglass over the entire area, and then began to work on leveling the platform fore and aft.  I did this by applying thinner strips of fiberglass to the aft end, and filling in the area forward with fiberglass and, eventually, more epoxy putty.

When at last I had the platform level in both directions (I lost track of how many layers), I applied four final layers of 24 oz. biaxial cloth over the main platform, and then covered these with two additional overlapping layers of 24 oz. biax, which I ran up the sides of the hull to tie everything together.

Finally, I smoothed the edges of the platform and limbers with epoxy putty for a clean, finished appearance.  After a final sanding, the platform was ready for painting.

Many moons later, I prepared to install the aluminum mast step provided by the mast builder.  It was a  simple 3/8" aluminum plate to which were welded a pair of aluminum tabs that approximated the inside shape of the spar section.  First, though, I used the step to locate the cutout in the coachroof above for the mast to pass through.

With the hole cut, I immediately made a measurement and then went outside to compare the actual height inside the cabin to the extra length of the new spar.  I was thoroughly relieved to find that it was just as I had expected, and that I had apparently measured correctly in the first place. 

Next:  final installation of the mast step, and finishing off the mast partners.  More about the mast itself is at this link.