Core Repairs

^{^Team}Wavelength

Core Repairs

Pearson utilized balsa cored construction for both the hull and deck. Cored construction provides a structure that is very stiff, and is significantly lighter than a solid glass hull of equal thickness. Cores of foam, and plywood have been utilized, but balsa wood continues to be the most wide spread coring material in use. Problems arise when water is able to penetrate the glass laminate and is absorbed by the balsa. In the case of the the Flyer, there were a couple of areas where the factory used coring techniques that might be considered questionable, and the results can be significant areas of damage. The cure for this “cancer” is radical surgery – removal of either the inner or outer fiberglass skin, removal of the rotten core, and new glass being laminated in place. In the case of “Wavelength” the medical bill was in excess of $8,000. Below are some thumbnails photos, along with a description. Click on the thumbnail for a larger view.

	This shot is forward of the port bulkhead. Sealing around the forward jib track, and chainplate had failed, allowing water into the deck core. The damage extended fore and aft of the bulkhead. Here the inner laminate and coring have been cut back to find solid balsa.
	Similar problem on the starboard side. Note the water stains on the bulkhead. This water staining unfortunately also suggests the possibility of rot in the bulkhead – which was the case. As a result, the bulkhead will also be replaced. On the starboard side, the rear genoa tracks were also leaking, so a similar area also required recoring further aft.
	Here is another shot of the keel area. Most of the water that got into the boat came from the bilge. In several areas the inner skin thickness was minimal – poor quality control during layup. These thin areas allowed water to migrate thru to the core. More commonly this occurs around thru-hull fittings where the core is not properly isolated, but that wasn’t the case on Wavelength – the thru-hulls were well sealed.
	Here is shot showing the aft edge of the keel. You can get a great idea of the laminate schedule from this view. The coring extends all the way to the centerline of the hull (which is built in two halves). A better choice might have been to stop the core several inches on either side of the centerline, and switch to solid glass in this area, particularly around the keel. The repairs to my boat will include 5 layers of glass in the area immediately around the keel.
	Here is an area of the deck after the core has been replaced. Note the greenish colored strip down the middle of the repair. In this area, solid glass was epoxied into place coinciding with the location of the jib tracks, above. The tracks were originally installed in an area cored with balsa. Many boats are built with plywood, or solid glass in areas where highly loaded hardware is to be located – not so on the Flyer. By changing to solid glass, the deck under these fittings is less likely to compress, and the glass isolates the core so any future leaks are much less likely to cause any problems.
	This shot shows the now nearly complete repairs to the area surrounding the starboard jib track and chainplate. The bulkhead has been mounted and tabbed to the hull, the chainplate has been refitted, and the jib track installed. The bulkhead still needs to have it’s finish applied, but structurally, it’s complete. The new paint on the inner hull really brightened the interior, and it looks nearly new!
	A shot of the starboard Genoa track installation. A decision was made to use aluminum bar stock as a backer instead of fender washers. This eliminates point loading of the fasteners, and results in a stronger installation. I also think it’s a cleaner looking installation. The factory originally supplied molded covers that did a nice job of covering the fasteners, but they had been removed from my boat long before I bought it.
	The new floor is in. We went with teak and holly here, like the main cabin, a part of which is just visible at the bottom of the photo. In this shot, the new floor has not yet had any finish applied, but it’s obvious that it’s going to make the existing cabin sole look pretty shabby (I needed another project?)
	Here is a shot of the keel area, the repairs now nearly complete. Note the brownish colored circular area in the upper right. This area has been faired, and is really complete. When the hull is finished, all the remaining bottom paint will be stripped, a barrier coat applied, and finally bottom paint applied once the bottom is fully smooth.
	Here the hull core repairs are completed and faired. The next step will be to strip the rest of the hull, barrier coat, and bottom paint. It's been a long road, but the result should be a sound deck and hull good for another 20 years or more of great sailing!
	Wavelength the day she came out of the shed. We went with an Interlux InterProtect 2000 Barrier coat (8 coats), which was then sanded and Interlux VC-17 Extra bottom paint. A smooth, fast bottom.
	Another example of wet core repair. A freind's Santana 35 had wet/rotted core over about 80 of the deck area. Ouch!