Installing the new, hinged mast-step
The new hinged mast-step with the 1 year old Aluminum mastbase, prior to installation.
The part is a
M30 hinged mast-step from Ballenger
Spar Systems.
The bottom half of the hinged deckstep installed
The hinged mast step is anchored into Threaded Stainless
Steel Inserts
The threaded inserts were cast into the deck with strengthened epoxy
resin.
The inserts are 5/16-18 THREADED INSERT 316 STAINLESS STEEL made by Fasco Fastener company, part #33217
In order to use flathead machine screws, and have sufficient strength to handle the shear loads of lowering and raising the mast, I "cast" threaded stainless steel inserts into the 3/4" diameter holes that I drilled in the cabintop.
The shear strength of the four stainless bolts was more than adequate, and I wanted to be sure the fasteners would stay anchored under the increased loads of raising and lowering the mast.
I enlarged the original four holes (for the old 5/16" lag bolts) and prepared to use flathead 5/16" machine screws to anchor the new hinged mast step.
The "Casting in Place" Process
The casting process ensured that the threaded inserts would be perfectly aligned with the holes drilled in the mast step. The threaded inserts were "cast in place" while assembled on the machine screws which were inserted through the mast step. The "cast in place" method
Before I drilled out the existing 5/16" holes to a larger diameter to accept the threaded inserts, I positioned the new mast step on the cabintop by lining up the holes and traced the position precisely. Then I inserted the new machine screws though the the maststep and screwed the threaded inserts onto the screws sticking out the underside.
I coated the bolts and hinged step in releasing agent, but carefully avoided getting any releasing agent on the outside of the threaded inserts.
I filled the holes in the deck almost full with epoxy thickened with microfibres and fumed silica (cabosi)l for structural strength and adhesion. Next, I positioned the whole assembly on the deck, with the screws and threaded inserts sticking down into the epoxy.
I taped the mast-step carefully in place and left it there to cure for 12 hours or so. After the epoxy had cured fully, I unscrewed the machine screws and removed the hinged mast step to inspect my work. That's the picture you see above.
Read more details on the "casting hardware in place" technique here
I also filled in the old thru-deck holes for the VHF coaxial cable, the OEM mast wiring (which was not marine grade), and the deck hardware the previous owners had installed -- I filled them all with thickened epoxy, after cleaning the out old sealant with a drill bit.
I found no rot under the old maststep or around any of the holes I filled. It's all quite solid under there, even though the old screw went directly into uncoated plywood core with some polysulfide caulking.
There is no exposed woodgrain now under the mast step. All fasteners are seated in solid epoxy and fiber fillets. There should be virtually no chance of core rot in the future.
Finally, I used waterproof epoxy putty to fair the area resonably flat.
Another shot of the bottom plate of the hinged mast step.
It's cosmetically ugly right now, but I'll fix all that when I repaint the boat with LPU this coming winter. At least all the old holes are sealed with epoxy and there's virtually no chance of future core rot.
For now, I've painted the surrounding area with white enamel paint to protect the epoxy from UV. So we can go sailing as soon as I get enough of the new hardware on her to actually sail her!
It'll be really nice to be able to easily remove the whole assembly for final fairing and repainting.