delrin bushing

Posted By: Seth Dabney, 2023-C, Oxford, MS
Date: 6/25/07 8:16p.m.

Report: outside forum guidelines

In Response To: Right but wrong :o) (charles pratt)

Charles, I like your idea, but see a wrinkle. The bottom of the hull is narrower than the centerboard trunk proper. A bushing that is concentric around the pin would only contact the thin edges of the hull, and not the flat sides of the trunk. There's a distinct lip about 1/8 inch. Maybe you can see what I mean here... Note how the top of the centerboard rubbed on the sides of the trunk when the original pin was in use. I think that if the pin were loose enough, this rubbing would eventually wear through the trunk, and is certainly accelerated wear on the pin, which is why I made shims and a tighter fit around the new pin. I made my polyethylene shims flat and attached them to the sides of the trunk with 5200. I had to rip them a bit thinner than shown to make the fit have a little clearance. When the board is down, the shims contact the flat sides at the top of the board, so, Gary, I don't understand how they could have caused any downward stresses in that position. They do increase force on the board while the board is raised, (for a while after I bottom painted the board they held in the up position when I didn't want it held until the paint wore off). You can see the wear marks in the photo below. On the other hand, they do take stress off the sides of the trunk so more force must be on the pin, pulling one side or the other whenever there is stress on the board. I think that the resin holding the sheet metal nut must have deteriorated with use and when I dropped the board a couple of times. The "rolling" action indicated that the screw must have been moving in a cavity inside the humps and probably progressively weakened the sheet metal nut inside it until the screw was literally hanging by a thread, which gave way. Now I am trying to figure the easiest way for me (or anyone) to make a strong fix. My thinking is that if everything is strong and snug, there will be less movement/wear/deterioration. The surest way seems to me to be to cut out the floor and work from both the top and bottom sides, drill down with into the humps through the fiberglass skin with a flat wood drill the size of washer to be used as a base of support. Inspect and remove any loose stuff. Rebuild with epoxy/glass/mat base to support a stainless washer and lock nut, more glass, etc., using the pin with lubricated 2 or 2.5" x 1/4-20 stainless machine screws to keep things aligned while curing. The other approach I am considering is drilling from the bottom a 1/2" or so hole, inserting a long slotted rectangular backup plate with a lock nut already epoxied to it. Rotate it into position, insert a bolt and then epoxy it in place. After curing, rebuild from below with glass and thickened epoxy. This would avoid having to cut the cabin floor but wouldn't be as strong and might not be feasible at all. Because of the uncertainty, I will probably work from above using either a rectangular cutout or 2" holes cut with my hole saw (these would be easier to cut and replace and would allow long pliers to assist with placement and alignment of hardware and epoxy/glass). Still considering....I welcome any suggestions or thoughts. Seth