Here is my fix for the prevalent mast support post problem as I outlined in the Big Boat Forum. Mine had not yet degraded to the point that the beam above the post had cracked but there was as it turned out a semi circular hairline crack in the head liner just forward of the post above the head door and slight bulging in the aft side of the beam near the liner as well. When a straight edge was laid on the deck from side to side just in front of the mast there was slight compression of the cabin roof evident and when laid fore and aft a noticeable space was evident from 2/3 of the mast base length forward. The rig tension on all shrouds and stays was decidedly loose. This coupled with all that I’ve read on this site and others prompted me to do this job now rather than wait for the problem to get worse. The short pipe raceway for the wiring was loose and the silicone seal had given up years ago. I only go on about this so that other owners have some signs to look for.
Anyway, the first thing I did was make a plan for the structure as accurate as possible so my machinist had a clear idea of what I was up to. I used a drawing program called Viso as I could scale it to 100% and it was convenient that the foot print fit nicely on an 8 1/2 X 11 sheet of paper. This was used as a pattern. There was tweaking along the way but having a good paln is crucial. I used 304 stainless for all pieces. I was able to use the drawing of the mast step from the online Rig-Rite catalogue to give me the basic shape for the 3/8 plate that the mast was to sit on. By the way the mast that I have is listed at the Rig Rite site, but a 4873 is very close. My mast is a 4871 while the 4873 is 4.8 inches wide by 7.3 inches long. To give plenty of support and spread the weight, I had it made one inch larger all round that the aluminum step. This was welded to the 2 inch schedule 40 pipe. A gusset was also welded to the underside so that the mast is supported for more of its base length. The bottom plate was fabricated with a short centering post welded vertical to it in the appropriate spot and is fastened to the main rib on the bottom. (It is interesting that while the mast was originally placed perfectly center on the beam on the cabin roof, it was only supported by the post on the front half) As well, it is always interesting working on a boat as nothing is square or seems to line up as in the case of the beam and the main rib on the bottom. In order that the new post land on the rib, it had to come through the beam as far forward as possible) I used the forward jamb of the head door to line the post up fore and aft vertical as it was exactly parallel to the original post. (Surprise)
The pictures show the 2.5 in hole drilled completely through the cabin roof and beam after wiring had been removed and a sloped slot for the gusset. (I was able to access the antennae wire and mast top weather station wire from the 12v surface mount reading light mounted on the port side of the beam over the shelving to pull them back with a fish tape attached). The mast-head light wires and ground wire were simply pulled down and out. It was necessary to cut the antennae connector and light wire connector. I made the access hole near the bottom of the mast for the re install. I learned of this little innovation from this forum as well. You can buy the stainless inspection cover from Rig Rite but I made my own). I don’t know how the mast was originally stepped with the wires pre connected, must have taken steady hands and a lot of crane time. There was some evidence of wires crushed but not severe.
All exposed edges from the drilling were coated and sealed with West Systems 2 part epoxy to prevent any possible rot in the future. A ½” hole was made in the pipe to line up with the wiring in the beam and another made near the bottom to exit to the settee as original. Note: when I pulled the wiring back out of the beam, I attached short piece of electricians’ fish tape to it previously mentioned as this is crucial and will save a lot of time and swearing. I only pulled it back far enough that it could be pushed into the pipe after installation. If you bend a hook in the end in the pipe you can easily fish it out the top with another piece of fish tape. There is also a ¾ in threaded hole through the top plate, inside the pipe far enough forward to miss the cross structure in the bottom of the mast(holds the exit pulleys) Into this I threaded a short ¾ in plastic nipple from Home depot. I sealed this up with fresh silicone once the post was installed.
Moving to the bottom end I had to prep the bulk head and lower part of the head door threshold by sawing a ¼ in space next to the rib so the bottom plate could slide underneath them. Once this was done I dry fitted the whole unit to see how much there was to trim for an exact fit. I actually applied a little pressure to the beam with a jack to raised a tiny bit so that some of the distortion to the cabin roof was corrected. It didn’t seem to make much difference but it made me feel good. The top plate holes were drilled and tapped at this time, 6 new ones and 2 originals. In order that the bottom fit perfectly I had to scribe the slope of the bottom rib on to the pipe and cut it at this angle. Once my machinist and I were happy with the dry fit, I fastened the bottom plate with 4200 and 4 # 12 SS wood screws. Then, after lathering up the deck with 5200, I dropped the post into place and screwed it down tight with 6 1/4-20 SS bolts and 2 slightly longer than original 3/8 bolts through the original aft slots in the mast step. I should mention that there is (as described by another forum member) a ¼ in thick aluminum plate laminated into the deck. I’m not sure how big it is but I hit it with all new bolt holes. New holes were dilled for the forward holes in the mast step as the originals disappeared when the 2 ½ “ hole was drilled. The front 3/8 SS bolts are threaded into the SS plate only. I re-fished the wires, sealed them and re-stepped the mast the next day. My machinist wants to weld the bottom plate to post and the beam support plate to post and this is not shown but will be completed as time allows. I don’t think it will matter too much but is a finishing touch. This whole process took about 3 days total working time but as you know it was longer in the planning stages. I will finish the project off by re installing the teak wrap once I get the old 4X4 out of it. I found the Sched 40 and plate at a Metal Mart down in Vancouver around 200.00, Crane time was 300.00, machinists time 500.00, miscellaneous stuff 100.00. I got very good pricing on all areas. I was hoping to do this upgrade without cannabalizing that main beam. I think that with any beam if you make big enough holes in them you will weaken them. This and the fact that there was no glassing to do made me happy. I do have some more pics and can make them available.