Replace Stemhead Fitting


  1. Notes:
    1. The stemhead fitting at the bow of the boat was cracking badly where the forestay attached, requiring replacement.
    2. Didn’t inspect the halyards at the mast head.
    3. Added caulking under screw/bolt heads, THEN tightened 48 hours later.
    4. No water drain added to the welded chainplate.
  2. Tools required:
    1. Bosun’s chair.
    2. 1 ¼” adjustable crescent wrench.
    3. Large Philips head screw driver.
    4. Vise grips.
    5. Penetrating oil (PB Blaster).
    6. Rubber mallet.
    7. Black permanent marker.
    8. Rigging tape for cotter pins.
    9. Need nose pliers for cotter pins.
    10. Blue masking tape.
    11. Razor knife.
    12. Caulking gun.
    13. Polyurethane 4200 caulking (1 tube).
    14. 80 grit foam sanding pads.
    15. Acetone.
    16. Paint Scraper.
    17. Flathead screwdriver for scraping the small corners.
    18. Replacement screws, nuts, washers from Hawaii Nut and Bolt.
    19. If head stay needs more loosening:
      1. Power screwdriver with allen head fittings.
      2. Spike to pry the Harkin lock nut off.
  3. Disconnect the head stay at its lower connection.
    1. Inspect the halyard condition at the mast head.
    2. Mark all turn-buckles with black permanent marker.
    3. Use a crescent and screwdriver (as a prying tool) to loosen the backstay as much as possible.
    4. Tie two halyards to the forward deck cleats to support the mast and winch tight.
    5. If the fore stay is not slack enough, loosen the two, aft, lower stays.
    6. Try tightening the halyards a bit more to take up the slack from the other stays.
    7. If more slack is required, slack the head stay using the Harkin fittings.
      1. Follow the Harkin instructions to disassemble the system, but basically:
      2. Loosen the sail a bit to access the allen bolts.
      3. Remove the bolts and slide the fitting up.
      4. Now you can access the vertical bolts to remove the two halves of the Harkin furler.
      5. Once the halves are off, you gain access to the upper lock nut. Loosen it all the way.
      6. On the bottom side of the furler, loosen the lower lock nut an inch or so.
      7. Pry out the lock washer and slide it down to the lock nut.
      8. Spin the assembly up to loosen the fore stay.
      9. Note there is no need to remove the sail.
    8. Once the fore stay is slack enough, tie a rope to secure the soon-to-be swinging forestay and prevent it from scratching the deck in the process.
    9. Try to minimize the amount of bending of the aluminum roller furling track when the forestay is disconnected by tying the rope as tight as possible to the pulpit.
    10. Pull the cotter pin and hammer out the steel clevis pin connecting the stay to the chain plate.
  4. Remove the stemhead fitting.
    1. Empty the anchor storage to gain access to the chain plate nuts.
    2. Spray penetrating oil on both sides of all bolts.
    3. Use the vise grips to secure one of the nuts.
    4. Use the large screw driver and attach the crescent wrench to the handle to provide leverage. Do NOT strip the screws!
    5. Undo the screw while the vise grips prevent the lower nut from rotating.
    6. The through-bolted nuts should have some sort of backing plate to tighten up again. If they aren’t there now, get some to prevent fiberglass damage. Large washers were used as backing plates for each nut.
    7. Once all the bolts are removed from the chain plate assembly, carefully pry it up and out without damaging the teak.
    8. If the assembly will not move, hit it up/down/left/right to unstick it from the deck. Use a heat gun on the chain plate to help loosen the glue if required.
    9. Protect the holes from rain using putty or a plastic bag while the chain plate gets fixed/replaced.
  5. Fix the stemhead fitting.
    1. The stemhead fitting is made of 316 stainless steel.
    2. Diamond Welding welded the crack in the old ¼” chainplate and added a new strip of polished ¼” chainplate on top of the old from the lowest bolt up to the tab, essentially doubling the thickness.
    3. The angle was also adjusted to prevent future cracking.
    4. Total cost was $340 cash.
    5. Note: There is a gap between the old chainplate and the new. Something should be done to prevent water from eating the chainplate from the inside out.
  6. Reinstall the stemhead fitting.
    1. Clean out the old polyurethane, gunk, and screw holes using paint scrapers and flat head screwdrivers.
    2. Sand the surfaces to remove the rest of the gunk using 80 grit foam sanding pads.
    3. Acetone all surfaces to be stuck together.
    4. Use blue masking tape to tape off areas outlining the areas of caulk for cleaner lines and easier cleanup.
    5. Use a caulking gun to dispense polyurethane 4200 on both the fiberglass and the steel.
      1. One standard sized 10 oz tube is just enough.
    6. Apply about a ¼” of polyurethane using the caulking gun and paint scraper.
    7. Install the forestay fitting, trying not to push the caulking too much while leveraging it into place under the teak toe-rail.
    8. Screw the screws and bolts into place (don’t forget the backing plate and/or washers) and tighten just enough to allow the caulking to dry at about 1/8” thickness.
    9. Add more caulking to anywhere water may get in.
      1. The new chainplate had a small gap along the length of where it was welded to the old chainplate. 4200 was applied to the full length of the seam as well as to the inside of the cleavis pin hole.
      2. A small water drain may need to be added to the bottom of the chainplate but was not done.
    10. Let sit for about 4 or 5 hours to set enough to remove the excess caulking.
    11. Use a razor knife, screwdriver, and paint scraper to remove excess caulking.
      1. Try to remove all caulking that would show in daylight, since the sun will deteriorate the 4200 material.
    12. Let sit for 48 hours.
    13. Unscrew the bolts/screws about ½”.
    14. Squirt a small amount of 4200 into the gap beneath the screw/bolt heads to create a seal.
    15. Tighten the bolts all the way and wipe away the excess caulking.
  7. Reattach the forestay.
    1. Loosen the Harkin assembly as much as possible, leaving enough threads holding the bolt to keep it from stripping (1/2” of threads?)
    2. Insert the clevis pin and cotter pin.
    3. Tighten the stays and tune the rig. (See ‘Tune the Rig’)

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