As things progress projects tend to overlap. Access to the backing plate for the bobstay tang is in the anchor locker. The bobstay tang is exposed directly to saltwater and, being a critical part of the rigging, it's good idea to check its condition. The bolts holding the fitting in place showed some signs of movement as tapered heads were slightly askew. Removing the fitting for inspection proved to be interesting. Oh but, wait after that we can take a look at the Whisker Tangs.
The backing plate was covered with fiberglass which had to be cut away. Under the backing plate wood (which was damp) was used to make a flat mounting surface. At the lowest bolthole the area was void. The wood will need to be removed and we will build up the area with epoxy to make a solid mounting point.
The condition of the bolts was better than expected even though the bedding appeared to have failed.The backing plate is made from 1/8" x 2" SS stock. We might replace this with 1/4" x 1 1/2" SS stock. This could reduce the amount of fill to make the flat mounting surface and shorten the bolts. In the first photo below you can see that one the bolts were loosened the fitting fits better about 1/16" lower.
Since we have the bobstay fitting is off the boat it would be good time to have it checked for cracks. It seems to be in good condition but it's difficult to tell.
Cleaning up the outside will require some additional work. There surface had a thick buildup of gel coat that needs to be cleaned up. There are also voids that will be filled with epoxy.
The wood block used inside the stem was teak and was partially bedded in a white fairing compound. It was wet and it only extend to the lower bolt. Cleaning out the space took some time with a wood chisel. A drill with a wire brush was used to clean most of the loose white fairing compound and/or gel coat.
The plan is to embed G-10 backing plates into the area with a thickened epoxy. This will distribute the load into the fiberglass stem. The bolts used previously were 3/8" SS. The bobstay tang, however, was drilled for 10 mm bolts. The holes in the fiberglass will also need to be cleaned up as well.
In order to do the epoxy work, the form (or jig) show below was made to act as a form when applying the epoxy and embedding the backing plates.
We've learned about a new resource, the Annapolis Makerspace so. They have various shop tools and helpful members. I've joined so that I can learn to use their CNC machine to cut the G-10 backing plates. You can also notice that we've also started cutting backing plate for deck hardware as most of the hardware leaks and does not have proper backing plates.
Once fitted, the G-10 plates replace the wood in the stem. They were glued using thickened epoxy. Once cured the wood block and dowels will be removed and we will drill the holes out from 3/8" to 10mm.
The original bobstay tang did not test well. It was constructed as a fork (rather than a single tang) and suffered from crevice corrosion where it could not be welded between the individual two tangs. A new bobstay tang was fabricated. After dry fitting, some minor adjustments and gel-coating it was finally bedded using butyl rubber.
Inside, there was a ground wire loop that was never connected to the original bobstay fitting. We took care of that and also added a screen to the drain pipe.