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Lightning Class Association
HomeBottom Jobs

Dangerous Bottom Jobs

by Mike Yates
In our business we have seen a lot of good and a lot of bad repair work. It seems that the increasing interest in wood boats in general, Lightnings specifically, has encouraged many home woodworkers to enter the wood boat restoration business. While I don't like to criticize other's work in general, several lessons can be learned from recent poor bottom jobs we've seen. This isn't to say that home woodworkers can't do good work, but those that do work for hire should not do jobs they are not qualified for.

Recently a very low-number Skaneateles Lightning was brought into The Sailboat Shop. The owner wanted several thousand dollars of work done. Unfortunately we received the boat after a new bottom job was done by someone else. What had been a perfectly salvageable hull had been ruined by the poor installation of an expensive new bottom. The net result was a bottom that warped to the point of popping off when it got wet. This would have been acceptable if the boat was going to be used as a planter or end table. But, as a boat, getting wet was unavoidable.

Regular readers are aware of our recommendation regarding the replacement of wood bottoms (see Cedar & Spruce, February 1995). Most wood Lightnings have bottoms made of western red cedar. Cedar makes a good bottom for the following reasons:

  • Cedar is rot resistant

  • Cedar's straight grain makes it unlikely to warp

  • Cedar, when wet, swells consistently

  • Cedar is light
Many other woods have one or more of these characteristics and as a results can also be used for new bottoms. Two of the most common are mahogany and spruce.
However, selection of the right wood is only one part of the equation. In this case, mahogany was used. Unfortunately, this was a double planked bottom and only the outer layer was replaced; the original inner layer was left cedar.

This mismatch of wood might have been ok if the two layers had been appropriately fastened, and if an appropriate caulking and membrane material had been used.

This particular repairman had used a black rubber material similar to roofing tar as both a membrane and a caulk. This material cured very hard. The combination of a hard caulking material with a hard wood like mahogany did not provide for the eventual expansion of the wood when wet. A more appropriate caulk would have been either cotton wadding of a polysulfide like Lifecaulk.

The unfortunate result was a bottom that expanded when wet, then popped. Since the wood couldn't expand between seams, it expanded away from the inner layer. Originally clinch nails were used to fasten the outer layer to the inner. This repairman used only screws through the two layers into the ribs. I think the black rubber was to act as an additional bonding material. However, this bond was not sufficient. The mahogany buckled out away from the bottom, creating large holes.

The sad end to this story is that after we did our work to the topsides and rig, the boat was ruined by vandals. The hull was damaged beyond repair.

For those of you interested in the final resting place for this boat—I've cut it in half. One half is being donated to a museum for a display. The other half will become a desk in my home.

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