Getting the Arch Back on Solid Footing

One of the boat projects this summer was to fix our arch, or rather figure out what was wrong with it. Last year an audible squeak developed near the starboard side deck mount. We tightened the bolts, but it kept returning. The arch also had more play in it as it came under load (some is normal, but this seemed to move more than it had in the past) and I kept thinking I could see the deck flex a little. Uh oh. 

Let me back up. We first put the arch on the boat in late 2011. It's a Beneteau factory arch, but for a 423 model. It mounts with two feet on the top deck and two on the transom, and uses four bolts on each foot. It was shimmed to fit the angle on our 393 model transom and made our boating life so much easier. We had to take it off/remount it in 2017 as part of a cross-country move. And it was probably fine until we started cruising full time, loading more crap into the dinghy while it was on the davits, and sailing in rougher conditions. We keep the dinghy with the engine on it on the davits for our little offshore hops, tying off the dinghy so it doesn't swing in seas. The issue started in the spring of 2020. 

By the end of this winter cruising season we knew we had to really look at it. Being at a dock this summer afforded us the opportunity to do the work ourselves (saving money and accepting a hard job!). First step was to remove the arch and see if we could identify an issue. This involved removing the solar panels so they wouldn't get damaged in the process and disconnecting a bunch of wires. With the arch off and dangling off the back of the boat, Frank was able to get in and see what was up. 

The 1st Mate helps out with lazarette boat yoga as much as she can while taking the arch off. Solar panels were stored on the foredeck throughout the project and we suspended the arch with the topping lift.

We did get some good news! Seeing a deck flex brings fears of a rotted core and a big, involved repair to get the mushy wood out, but the section of deck we are dealing with is actually solid fiberglass! Yay! And it wasn't cracked that we could see. Now we always knew where the bolts came through the deck was a little weird, with some bolts just going through the layer of deck and 3 of 8 total deck bolts going through a wood backer/other component of the deck structure. Removing the whole arch also revealed that where the bolts went through the deck the fiberglass was only 3/8" thick whereas where it was mounted on the stern the fiberglass was almost 1" thick. And we found that one of the 16 bolts that mounted the arch was bent. Sooooo....our issue was likely a combination of the thinner top deck, the heavy load in the dinghy, and maybe taking some big lateral loads in waves at some point. 

Since the deck was solid fiberglass we decided to reinforce and level the mounting surface for the deck feet. Frank started by building up fiberglass blocks that would be used to level out the deck mounting areas. This took a lot of layers of fiberglass, then cutting to shape, then more fiberglass to get them the right thickness.

Arts and Crafts time on Lehe Paine with! Building and shaping the blocks was a multi-day process, but it was worth it. 

And that was the easy part! Then he had to wedge himself into the lazarettes multiple times to place the fiberglass blocks and then coat the entire mounting area with layers of fiberglass to ensure it was one complete, solid structure. This whole process stretched over a few weeks with curing times, weather delays, and other fun. 

More boat yoga! We had some really hot days that made this task miserable; fitting the blocks.

When the deck was reinforced he went a step further and epoxied 1/4" G-10 fiberglass board as a backing plate at each of the four mounting locations for the arch. And because Frank doesn't underbuild anything he also went with beefier, longer bolts.

Trent drills through the new layers; the bolt upgrade; G-10 backer boards in place.

With the deck beefed up the guys drilled through the new layers of glass, we slapped some 3M 4200 sealant/adhesive all over the place and remounted the arch! Ok, it wasn't actually that easy...4200 got everywhere, I was terrified we would drop the shim in the water, the rubber mallet was used extensively to push bolts in, and a few of the bolts were actually too long to clear the arch legs as they were going in and had to be cut. But it is back on and better than ever! The deck mount actually looks way better and more flush than when the rigger put it on in 2017. Add in the many gelcoat cracks that Frank fixed as part of the project and it really looks fabulous! (FYI, spider cracks in gelcoat are common, especially on a boat that's as old as ours.   It's usually just a cosmetic issue.)

The "car" is back in the "garage" and the deck was SOLID!

We feel pretty confident that this should solve the issues we were having (or will rip the entire stern to pieces)...guess it's about time to head out and test it out on the ocean!