Situations and Solutions
Whether you replace broken frames or decide to sister them, you should make changes so the new frames or sisters don’t develop the same problems. If the bend is too severe, you can ease it by decreasing the frame’s molded dimension with a corresponding increase in its siding. But usually, cutting saw kerfs in the frames before bending thus halving the severity of the bend is necessary. When the frames are too narrow to take fastenings properly, or when complete tension breaks indicate an insufficient frame cross section, an increase in sided dimension should accompany the kerfing. With the saw kerfs, the original molded dimension can be maintained.

6—A number of adjacent frames are broken along the same plank seam, and a knuckle or “chine” has developed in the planking. The only suitable way out of this problem is to remove and replace all the frames in the problem area. If there’s a bilge stringer in the way (and more often than not it has contributed to the problem), it should be removed for access. If the frame broke behind the stringer, don’t put the old stringer back in. Instead, use a wide, flat stringer, or several wide, flat strakes of ceiling. If you go about the repair conservatively, removing and replacing one frame at a time, you’ll probably find the unwanted knuckle is still there when you finish and that the new frames have conformed to the unfair spots rather than pulled the hull back into shape. The only way to treat such an extreme case is to take out a number of adjacent frames and at the same time completely reef out the offending “chine” seam so the planking can be drawn back in to its proper place. Before you fasten in a new frame in a situation like this, you should always remove at least a couple of frames between it and the old broken ones. An adjacent broken frame will retain its knuckle shape and prevent the planking from pulling in against a pre-bent fair frame. And when new frames are bent right into place in the boat, they have a tendency to duplicate any unfairness in the planking.

Of course, situations arise when a boat owner, faced with this frame problem, has no other choice but to “funk it out.” In such a case, sister frames again come into the picture. However, if the unfair area is only sistered and no other changes are made, there won’t be any improvement in shape, and the sisters are very likely to take the unfair, severely bent shape and break after a year or two. There are two possible approaches to the problem. First, sister the frames, kerfing the sisters if necessary to ease the severity of the bend, and let the sisters line fair over the hard spot, shimming behind them for solid fastenings. Second, cut back part of the original frames the width of several planks each way from the break, sister the frames, and pull the planks back into shape, letting the sisters do all the work of the original frames over the problem area. If the unfair spot is under the bilge stringer, either of the above methods may be impossible without removing the stringer.

7—Frame heels are split or broken where they bend down into the bilge, but the rest of the frames are sound. Here, the cause is almost always the severity of the bend. Known as the “Novi-boat syndrome,” the problem is very serious in ballasted sailboats. With split or broken heels, the frames are generally unable to carry the ballast load up into the hull above the floor timbers, resulting in split planks or opened-up garboard seams as the load falls on the planking. The only way to restore such a boat to its original strength is to replace each flawed frame entirely, eliminating the cause of the problem at the same time. Where the frame heels are socketed into the keel, it may be physically impossible to install a full-length replacement frame. Since the tight bend that was needed to get the frame heel into its socket in the first place probably caused the problem, it is usually preferable to abandon this technique in the repair. If the floor timbers are properly fastened to the ballast and backbone, and if the frames are properly connected to the floor timbers, socketing the frame heels gives little or no structural advantage. Cutting a saw kerf to ease the severity of the bend in frame heels may compromise the effectiveness of the floor-to-frame fastenings. A better, and in many cases only, strategy here is to let the frame run out onto the face of the floor timber. This eases the severity of the bend, makes full-length frame installation possible without removing any planking, and places the floor-to-frame fastenings inboard away from the end grain of the floor timber. The old frame can be cut off flush at the top of the keel if socketed in, or, if not rotten, cut off higher so that the new frame lies on top of it. Where the new frame is close to the planking but not in contact, wedges can be inserted between frame and plank to allow solid fastening. Where the new frame runs well away from the planking, the plank fastening can go into the floor timber, into the bottom of the old frame if it’s still there, or into a sawn cleat fastened to the edge of the floor timber for this purpose.

Boats built by Herreshoff never had socketed frames, and, in many cases, the fastenings in the lower planks went only into the floor timbers, because the frames ran out onto the floor-timber faces as described above. Of course, longer screws should generally be used where the plank fastenings go into the end grain of the floors.

In very mild cases of frame heel splitting, where the splits haven’t loosened the floor-to-frame fastenings, a metal strap on top of the frame will keep matters from getting any worse by holding the splits from lifting. If the splitting is more serious, but you can’t replace the top part of the frame for financial reasons, you can bend in a new bottom, preferably in place of the old one, with a scarf joint connecting it to the original top. This joint should be located where the frame has little curvature, with metal splice plates fastened on one side and on top of the joint to allow transfer of tension, and a sister frame next to the joint, fastened to both pieces of the frame.

In summary, frame replacement is always the best repair method from a structural viewpoint, and, although more expensive initially than sister framing, it is usually more economical in the long run. In certain situations, however, sister framing is suitable, particularly when the boat has other serious problems that make the expense of reframing impractical. Specific techniques will be examined in a future article.