Mast fall lessons learned
Posted: Sat Apr 02, 2011 3:21 pm
I replaced the factory shackle on the mast raising winch with a Wichard keypin shackle (
) because I wanted a slightly longer shackle to make attaching the lower fore stays easier. The two stays and mast raising winch knot were too thick to easily fit inside the stock shackle, and switching them had been the longest part of rigging for sail. I've raised the mast a number of times with this keypin shackle in the past.
Today as I was raising the mast, right at the point where the toe of the mast foot would be guided into the deck, the winch tightened a bit because the toe caught the side of the mast foot receiver and the shackle failed suddenly, sending the pin flying and dropping the mast raising winch pole onto me. The mast fell back onto the cockpit, but I was able to push it to the port side away from the starboard side where the Admiral was standing to clear stays and the spreaders.
The mast fell slot down onto the forward cockpit stanchion, and because the cockpit lifelines were down, the spreader then hit the track on the port side of the cockpit and the cockpit seat, bending it.
Inspection revealed no damage to the hull at all. The spreader took the brunt of the damage and bent. The mast is also no longer true straight, but may remain straight enough to function. There is slight damage to the mast where the slot hit the stanchion but that can likely be filed smooth. I had been worried that the foot of the mast might be bent, but it appears to remain straight. There's enough "slop" in the mast foot pin slot to allow the mast to fall anywhere onto the cockpit.
Lessons learned:
1) Keypin shackles have a sudden failure mode: If the pin bends, the keypin can come out of the shackle suddenly. This is not the case with a screw pin shackle, which will instead bend and deform before breaking, which serves as a visible warning of being overstressed. Do not use keypin shackles where a failure can cause injury.
2) Be exceptionally cautious when replacing factory hardware. Be certain (don't just presume) that the load rating of the replacement hardware is higher than the load rating of the factory hardware. I couldn't find a load rating on the keypin shackle and presumed that since it's the same size pin that it would be the same strength or better because it was forged. Obviously not the case. Also, because I replaced the factory hardware, this mast fall isn't a warranty issue, it's my fault.
3) Nobody topside aft of the mast when raising. From now on, the admiral will go below until the forestay is connected. We had believed that being to the side would be good enough, but the mast easily fell all the way to the port side of the cockpit when I pushed it that way. Just before it actually fell, I had warned her to one side and asked her to sit down, because if something happened I didn't want her to startle and fall backwards over the cockpit onto the hard.
4) Put the lifelines up when raising the mast. Had the mast hit the lifelines, I likely would have gotten away with no damage.
5) If the mast is going to fall, definitely push it to one side or the other. The best case scenario would be landing on the lifelines. Otherwise, having a spreader take the load is the least damage you're going to do.
We were really lucky in that we can probably get away with replacing one spreader. Hope this post saves someone else some grief.
Today as I was raising the mast, right at the point where the toe of the mast foot would be guided into the deck, the winch tightened a bit because the toe caught the side of the mast foot receiver and the shackle failed suddenly, sending the pin flying and dropping the mast raising winch pole onto me. The mast fell back onto the cockpit, but I was able to push it to the port side away from the starboard side where the Admiral was standing to clear stays and the spreaders.
The mast fell slot down onto the forward cockpit stanchion, and because the cockpit lifelines were down, the spreader then hit the track on the port side of the cockpit and the cockpit seat, bending it.
Inspection revealed no damage to the hull at all. The spreader took the brunt of the damage and bent. The mast is also no longer true straight, but may remain straight enough to function. There is slight damage to the mast where the slot hit the stanchion but that can likely be filed smooth. I had been worried that the foot of the mast might be bent, but it appears to remain straight. There's enough "slop" in the mast foot pin slot to allow the mast to fall anywhere onto the cockpit.
Lessons learned:
1) Keypin shackles have a sudden failure mode: If the pin bends, the keypin can come out of the shackle suddenly. This is not the case with a screw pin shackle, which will instead bend and deform before breaking, which serves as a visible warning of being overstressed. Do not use keypin shackles where a failure can cause injury.
2) Be exceptionally cautious when replacing factory hardware. Be certain (don't just presume) that the load rating of the replacement hardware is higher than the load rating of the factory hardware. I couldn't find a load rating on the keypin shackle and presumed that since it's the same size pin that it would be the same strength or better because it was forged. Obviously not the case. Also, because I replaced the factory hardware, this mast fall isn't a warranty issue, it's my fault.
3) Nobody topside aft of the mast when raising. From now on, the admiral will go below until the forestay is connected. We had believed that being to the side would be good enough, but the mast easily fell all the way to the port side of the cockpit when I pushed it that way. Just before it actually fell, I had warned her to one side and asked her to sit down, because if something happened I didn't want her to startle and fall backwards over the cockpit onto the hard.
4) Put the lifelines up when raising the mast. Had the mast hit the lifelines, I likely would have gotten away with no damage.
5) If the mast is going to fall, definitely push it to one side or the other. The best case scenario would be landing on the lifelines. Otherwise, having a spreader take the load is the least damage you're going to do.
We were really lucky in that we can probably get away with replacing one spreader. Hope this post saves someone else some grief.
