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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.

maststep1.jpg (54310 bytes)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.

maststep2.jpg (60724 bytes)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.

maststep3.jpg (62404 bytes)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.


maststepaft.jpg (43867 bytes)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.

finalglassstep.jpg (48802 bytes)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.

mastlimbers.jpg (51306 bytes)With the glasswork complete, I ground the forward and after edges to begin to smooth the rough edges.  Then, I reamed out the Styrofoam molds in the limbers on each side; this was fairly easy using a triangular file to remove the bulk of the material, and then a dowel wrapped in sandpaper to clean out the small remaining amount.  


maststepdone.jpg (42671 bytes)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 new step located in the correct place on the fiberglass base in the bilge, I used a level and a straightedge as an extender to mark the center point of the mast step on the overhead above, marking directly plumb above the step centerline.  I marked it both transversely and longitudinally.  Then, I drilled a small pilot hole from inside out to mark the spot.

Next, I used a piece of cardboard to trace the shape of the mast section, which I then expanded by 1/2" all around to allow some leeway and room for the spar to rake forward or aft.  After cutting out the shape, and locating the center point of the spar according to the mast step, I used the drill to make a hole in the center, and placed the template over the hole in the coachroof, using the drill bit as a guide.  After ensuring that the template was properly aligned, I traced the outline, and then cut the opening with a jig saw.

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.

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