Tuesday, February 11, 2014

Pivot bushings installed

After the oversized, epoxy-filled pivot holes in the rudder and centerboard cured, I drilled them out with a forstner bit to the right size for the bronze bushings, and proceeded to prepare the bushings.  My local hardware store didn't sell bushings long enough for the full width of the parts, so I bought them in pairs.  I used one full length (1 1/8 inches) and shortened the second one to make up the length required.

I first cut the bushing to rough length with a hacksaw, then chucked it up in the metal lathe and faced of the end.  I was having fun, so decided to spend the time turning a shoulder on one part and boring a recess in the other for a nicer job.  I then turned some coarse threads on the outside to give the epoxy something to grip.

Can hardly see the joint when these go together.  Nice to have a lathe... 

Here's a shot showing the threading in progress on one of the bushings that goes in the centerboard case.

However, to save time on the rudder pivot I just used a butt joint.  

I put a piece of tape across the bottom of the holes, coated the outsides with unthickened epoxy, and inserted them in the holes.

When I installed the centerboard case bushings, I combined two steps.  Instead of drilling the holes oversized, filling them with epoxy, and then drilling them out again, I instead drilled oversize and then cast the bushings in place.

To hold them in perfect alignment, I used a spacer block that fit exactly inside the case.  I taped both sides, and drilled a 1/2" hole on the drill press.  Here's the spacer block installed in the centerboard case.

I then could put a greased 1/2" rod through the bushing and block to ensure the bushing was perpendicular.

I coated the inside of the hole with unthickened epoxy, then coated both the inside of the hole and the outside of the bushing with thickened epoxy and inserted the bushing.  Then poked around with a toothpick to try to make sure there were no air bubbles in there.  If I were doing this again, I would drill the oversized hole larger to make it easier to get the epoxy in there.  The bushing is 3/4" outside diameter, and the hole is 7/8", so just 1/16" gap.

I filled the top hole, then the next morning turned the part over and did the other side.  After the epoxy cured I removed the rod and was able to drop the pivot bolt in with no binding, so I was pleased with my success in getting these bushings aligned with each other, and perpendicular to the surface.

I liked doing this work on the flat vs. trying to install these after the centerboard case was in the boat.  Other than dealing with large parts it was fairly easy to keep holes perpendicular on the drill press, checking alignment with a small square.

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