Raising and lowering the centerboard on my Bristol 35.5 became progressively more difficult last season. I seized the opportunity to inspect the system whilst suspended in the Travelift slings at Bridge Marina, Salisbury, MA last weekend. Not pretty.
At first I thought the cable which is used to raise and lower the board had jumped off the lowest of the three sheaves which direct the cable tension from the deck worm gear to the board itself. I saw some keyholing where the cable had begun to saw away at the centerboard trunk. My attempts to put the cable back on the sheave from below were unsuccessful; I decided to dig deeper. I ended up conducting a root canal on the system.
After grinding away the fiberglass cap which covers the sheave, I was horrified to find that not only was the sheave eaten away but also the sheave axle was nearly cut through by the cable. See the photo below. I couldn’t find a bronze replacement at my local West Marine but I did find an aluminum sheave which I installed. I then covered everything up with epoxy and fiberglass taking care to overlap the glass to the surrounding centerboard trunk. This all was accomplished while hanging in the slings. I’m grateful to Alan at Bridge Marine for letting me stay suspended in the slings for 24 hours and for the use of his crimping tool to attach the replacement cable.
What’s next?
Later this season, I intend to replace the aluminum sheave. I can source or have a new bronze sheave made. However, perhaps I should consider a different material. What about using a Monel sheave and a Monel cable? What about using a delrin sheave and a high modulus, synthetic cable? The cables are easy enough to replace; the sheaves are not. I’d like to find a material that will stand up to 25+ seasons of immersion in salt water. Any suggestions?
At first I thought the cable which is used to raise and lower the board had jumped off the lowest of the three sheaves which direct the cable tension from the deck worm gear to the board itself. I saw some keyholing where the cable had begun to saw away at the centerboard trunk. My attempts to put the cable back on the sheave from below were unsuccessful; I decided to dig deeper. I ended up conducting a root canal on the system.
After grinding away the fiberglass cap which covers the sheave, I was horrified to find that not only was the sheave eaten away but also the sheave axle was nearly cut through by the cable. See the photo below. I couldn’t find a bronze replacement at my local West Marine but I did find an aluminum sheave which I installed. I then covered everything up with epoxy and fiberglass taking care to overlap the glass to the surrounding centerboard trunk. This all was accomplished while hanging in the slings. I’m grateful to Alan at Bridge Marine for letting me stay suspended in the slings for 24 hours and for the use of his crimping tool to attach the replacement cable.
What’s next?
Later this season, I intend to replace the aluminum sheave. I can source or have a new bronze sheave made. However, perhaps I should consider a different material. What about using a Monel sheave and a Monel cable? What about using a delrin sheave and a high modulus, synthetic cable? The cables are easy enough to replace; the sheaves are not. I’d like to find a material that will stand up to 25+ seasons of immersion in salt water. Any suggestions?
