G30 Halyard Sheave Replacement

I went for a late summer sail and the halyard jammed while hoisting the main. She wouldn't go up or down. This had happened before and a gentle tug on the sail would free the jam. I initially thought the problem was jammed slides. Once back in the marina I gave a mighty pull on the 30 year old main and ripped it completely off. I finally isolated the problem to failed masthead sheaves. I decided to replace them without stepping the mast.

Sheave replacement on a Grampian 30 without stepping the mast.

The sheaves on Yellowbird appear to be original. They are glass reinforced Nylon 2 5/8 across, center hole 3/8 and 9/16 wide. because of the tight fit, I would recommend downsizing to 1/2 inch wide to avoid future jams.  

 If one halyard jams, assume the other is as well. Yellowbird has a masthead cap with the backstay attached aft and spinnaker halyard on the front. Using a bosun's chair is not possible. A 40 foot ladder is perfect size. Because the jib halyard was starting to jam we hoisted the ladder using the spinnaker pole topping lift. We set the base of the ladder on deck in front of the forward hatch and extended the ladder. We secured the ladder base with ratchet straps. On the initial assent we used the Spinnaker halyard as a lifeline attached to a utility belt. Two lines secured the top of the ladder to shrouds. The ladder was rock solid. Once aloft secure your belt to the mast and remove the spinnaker halyard. On the mast cap, remove the forward 1/2 inch bolt and raise the cap. Remove cotter pins from the sheave pins and spray some penetrating lubricant on both sides. With a hammer and Philips head screwdriver punch out sheave pins. If they are completely jammed, sheaves will remain in place. Using hammer and screwdriver, gently tap the bottom of the sheave and they will come out. Thoroughly clean the area. For replacement I used a short length of electrical wire around the new sheave and lowered it in place pushing the pin halfway through. Install the second sheave the same way reinstalling the pin and replacing the cotter pin. Pull down the masthead cap and reinstall the forward bolt. Complete the masthead inspection/repair. Once replaced, I used the jib halyard as a lifeline as I didn't trust the spinnaker halyard to support my weight. 

 Now we are ready for some fall sailing on the Potomac and Bay!

Greg Weisiger
Yellowbird, Kinsale, VA