PS Advisor September 2008 Issue

All Plywood Not Created Equal

Marine-grade plywood does have its advantages.

I was wondering if you folks have ever the various kinds of plywood for use in marine environments. Needing to replace a bulkhead, I went plywood shopping with a friend. It’s his belief that there’s little difference between regular plywood and marine plywood, other than the price. He says it’s all the same glue, and that different glue wouldn’t matter because wood is wood and it all delaminates the same when exposed to water. What are your thoughts?

Scott Fraser
Hunter 31
Key West, Fla.

Brunzeel, marine-grade plywood, is preferable over ordinary plywood for many reasons, but one of the main reasons Practical Sailor recommends it for boatbuilding is that it has fewer voids than ordinary plywood. Compare the edges of the two types and you’ll see the difference. You can get by with non-marine plywood for interior projects, but we’d still opt for marine grade.

Pedestal Painting

have been a Practical Sailor subscriber for over 10 years and read the publication religiously. I have a 1984 C&C 29 sailboat. The original flat, black aluminum Cenkle pedestal is corroding. How can I clean it up, stop the corrosion and apply a flat black paint by brush without removing the entire pedestal? What preparation and products would you suggest I use?

Paul Kelly
S/V Irish Ayes
Staten Island, N.Y.

The Edson website features a detailed description of the steps we would generally follow, as well as some advice as to how to avoid further paint failure. (Go to www.edsonmarine.com and search for "Repainting instructions for Edson pedestals.) They recommend Interlux coatings for the project and we have had good luck with these. An experienced painter could use similar automotive paints, but the guidance of Interlux’s technical support people is well worth any dollars

Selecting Plywood for Boatbuilding Projects
When selecting plywood for boatbuilding projects, be sure no voids are visible. Marine-grade plywood typically has fewer voids than ordinary plywood.
you might save. Preparation of aluminum is essential to achieving a good paint bond, so you will want to follow their advice to the letter. As much as possible you will want to remove any hardware, fasteners and accessories for painting, and then, during reassembly, try to isolate them from the painted surface using a Duralac (good for threads), a bedding compound (polysulfide, silicone or polyurethane caulks will work), or plastic washers.

Shackle-Pin Search

have a Tripp 47 fractional rig I use for racing. I would like to replace the lose-able pin-style shackle on the mainsail. I’m considering one with a 4,000-pound working load and 8,000-pound breaking strength, but don’t know if it’s of sufficient strength. My sailmaker says to ask a rigger, the shackle manufacturer says to ask a sailmaker, and the rigger says to ask the sailmaker. Everyone is concerned with liability! How do I pick the right shackle?

Dale Cohen
Tripp 47
Chicago, Ill.

We suggest you contact the boat’s designer Bill Tripp at 203/838-2215. Ultimately, these specs should come from the naval architect based on the load factors for all the related components on the boat, in this case your rig, as well as your sails. Some designers omit this vital spec on their drawings, leaving it up to sailmakers. The David Pedrick-designed Navy 44 MkII reviewed in the July 2008 issue, for example, took this approach.

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