Expansion Joint Leak Repair
First I want to thank those in HNSA who shared with me all their experiences good and bad with the expansion joint leaks that plague so many Historic Ships. Experience is the best teacher so I want to publish our technique which has held up through a Summer, Fall and Winter of Louisiana rainfall, a rigorous test.
As everyone who advised me had said, preparation of the joint is the most important part of a successful repair. We had all manner of materials slathered in the joint including epoxy cement, silicone caulk, "Blackjack" roofing cement and heavy rubber sheet glued over the entire mess with silicone adhesive.
After much trial and error we found out that an air-chisel was the easiest way to get the bulk of the material off the metal. It came off the aluminum side of the joint pretty cleanly, but the steel side was a lot more difficult to remove because the metal was pitted and all of the goo of one kind or another stuck to it. Then once the bulk of the old repair had been removed, we used a 4" angle grinder with a spiral wire brush to clean the surfaces of both sides of the joint down to BRIGHT METAL.
Our friends at Lake Charles Rubber and Gasket were generous enough to cut some strips of commercial grade reinforced vinyl tarp material to our measurements. We measured the distance between the edges of the trough which contains the joint, added enough width to allow for a dip in the center of the completed joint and had it cut into sections about 20-22 feet long. LCR&G also provided us with vinyl cement to seal the overlapping ends of each length to the next. We worked in sections of this size for two reasons: One, rain around here is frequent and we wanted to leave the ship "buttoned up" at the end of the day, and, Two, working with shorter sections was a lot easier once we knew we had the vinyl cement that was guaranteed to seal one section of the strip to the next.
We used high quality silicone seal to attach the vinyl to the surface of the metal. After wire brushing the surface, the area was cleaned thoroughly with the shop vac and then the surface of one side of the joint was wiped down with acetone. One edge of the vinyl was glued at a time, a generous amount of adhesive was applied, the strip laid on top and all air and bubbles were squeezed out with a roller or the heel of your hand. Keep the vinyl lined up with the edge of the joint to avoid pleats. This is not too hard since the vinyl is easy to move around before the silicone hardens. We allowed the adhesive to cure overnight if possible during which time we would start preparing another section of the joint. We prepared the vertical sections of the joints first since if the rain caught us, we figured those sections would let in less rainwater if they were open than the horizontal sections would. Fortunately, we didn't have to test this because it remained dry throughout the times when we had an open joint. After the first edge dried, and after preparing the surface carefully as described above, we glued the other edge of the vinyl.
Since we had cut the width of the strip about 1/2" more than the width of the groove that the joint sits in, all we had to do was line up the edges of the vinyl with the edge of the groove, and the proper slack was built in.
Because it is difficult to keep the strip lined up as you make the curve from the horizontal section to the vertical sections of the joint, we learned to use sections of vinyl about 6-8 ft long depending on accessibility of that area of work, and glue them in from bottom to top. Start with the vertical section just above the lower deck and cut your first strip to stop before the curve begins. Glue one side at a time allowing curing time between sides. It is tacky enough so that you can do the other side without disturbing the first side in a few hours depending on temperature. Then cut a strip 6-8 feet long depending on your exposure for the curved section. Apply in the same way except that you should leave 6" or so of the second strip overlapping until both edges of the upper sheet are glued, and then use the vinyl cement as per instructions on the can to glue the overlap to the lower section. Then apply the horizontal sections of vinyl on the upper deck overlapping them with the upper ends of the curved sections. Glue the vinyl overlaps last at all joints.
I am expecting a long life span on the vinyl since it is covered by the plates and is out of the sun.
Thanks again to all of you who gave me advice and shared your tales of woe with me on this. Follow our web site for any news of failure of this technique. A good time to check on it is after you see that a Hurricane has struck the USS Orleck in Lake Charles, LA.