Twisting of the hull from rough water torques the frame joints, leveraging the screws at the topside/bottom frame "knee" joint, causing them to loosen. And as the bottom planks swell, they expand and push the chines outward from the frame landings, taking the topside frames with them. Notice the 4 screws of this frame station are loose, the bottom one backing out quite a bit.
The seasonal swell/shrink cycles of the bottom planks works the frames and brass screws at the knee joint back and forth, elongating the screw hole in the frame or breaking the screw. The chines are attached to the topside frames with a ¼”-20 carriage bolt and a screw at main frames. The chines are attached only with a screw at the intermediate frames. Bottom swelling, pushing on the chines, will pull the screw from the wood at the intermediate frames, or break the screw, creating a gap.
When the boat was built, these intermediate frame joints were tight against the chine. The restoration process must bring the chine and frame back into alignment. Over time, this spreading of the bottom planks causes leaking, structural weaknesses and failure of components. After getting the boat leveled and blocked, it is time to pull the topside frames back into position for bracing. Using pipe clamps at the topside frame, the clamp is hooked to the bilge stringer and tightened until the intermediate frame is tight against the chine.
With the joints tight, 1”x4” pine braces are screwed to the topside frames below the knee to hold the frames in position. With the all joints tight, we reconfirmed the chines were still level. With everything set, the keel and chines were removed in preparation for frame inspection and replacement.
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