Tuesday, October 15, 2013

Water in the Bulkhead!

While installing the anchor washdown pump, I had to drill a hole in the bulkhead that separates the salon from the forward lockers. There are already holes in the bulkhead for the fresh water supply and for the battery cables to the windlass. Imagine my surprise to find water coming out of the hole as I drilled. A fair amount of water came out of the hole over the next day. Darn! Something else to add to the list of things to do.

When I had time to look at it, I drilled a set of exploratory holes in the bulkhead from the locker side. That told me the extent of the delamination. I then used a hole saw to drill a set of larger holes through which I could extract the rotten balsa. The holes that found good wood were definitely balsa and not something else like plywood. The affected area is about 9 inches wide by 12 inches high and is about 1/2 to 3/4 inch thick.

Mike suggested using polyurethane foam to fill the void, recalling that polyurethane glues tend to be aggressive. However, my investigation showed that there are vast differences in foam characteristics and that the insulating foam at home improvement stores is definitely not a good candidate. It crushes too easily to be used here. The bulkhead helps distribute the loads from the mast and stays and is not where we want to have a poor choice of materials affect the vessel's integrity.

Background documents that informed me about the choice of materials:

http://forums.iboats.com/boat-restoration-building-hull-repair/foam-core-vs-balsa-core-no-stringers-404079.html (see posts by erikgreen)

http://www.fiberglasssupply.com/Product_Catalog/Core_Materials/core_materials.html (source of core materials)

I understand from some of the members on the Yahoo Groups Leopard mailing list that good construction foams are available in liquid form. I also know that there are foams that result in very solid structures that survive being hit with a hammer. However, I would want to consult with a structural engineer or naval architect before using them to make sure that the foam has all the characteristics that are needed for boat construction (compression, sheer, and tensile strength for starters).

How did water get into the core in the first place? I suspected that it was related to the stamoid cloth that is held in place with Keder track under the aft end of the anchor locker. It is in this cloth holder that I put the coiled hose for the washdown pump - very handy. (The washdown pump install is a future blog.) While I was working removing the rotten balsa, we had some rain and I found that water made its way into the forward locker. More water than I thought was reasonable. The aft end of the anchor windlass locker has an oval hole that the locker hatch cover doesn't cover. Any rain that comes down at a slight angle, or spray from forward, can easily fall into the hole. The stamoid cloth then holds and directs the water. A significant amount of water is directed onto the fresh water fitting that penetrates the bulkhead. No caulk was used in the installation of this fitting, so the water wicked its way into the bulkhead core.

There are several solutions to the source of the water. First, we plan to make a stamoid or vinyl cover for the oval hole, to direct water away. Second, we will be using caulk to make sure that any water on the bulkhead doesn't wick into the core. Third, we'll be sealing the bulkhead penetrations with epoxy to make sure that no water can get to the core.

We recommend that Leopard owners look for similar problems on their boats. We know that the early L40 has this flaw. (LUX is hull number 009, Nov 2004, according to identification written on the backs of various boat parts.) It is relatively easy to disconnect the fresh water hoses on the salon side of the bulkhead, and remove the fitting from the locker side. Check the balsa around this opening. If it is in good condition, remove some balsa and fill the edges of the holes with epoxy or polyester resin, to seal the edges of the balsa. Then use caulk when reinstalling the fitting.

The old balsa was removed using bent pieces of wire. We have three sizes, ranging from clothes hanger to 1/8 inch steel wire. We used a heat gun on its low setting to help dry the balsa so that we can make sure that we remove all the balsa from the fiberglass panels - this way whatever we install will adhere well to the walls.

While the bulkhead core is drying, we're discussing how to effect the repair. Our current solution is epoxy with microballoons, which creates a light, strong, and moderately flexible core that will self-adhere to the existing bulkhead fiberglass panels.


1 comment:

Terry said...

See the followup post: