End of 2021, I bought a Lightning from the 80s (13929) that was in pretty nice shape as a good boat to go race in. The first time I saw big breeze in it was in Burlington Vermont for the Spring Regatta at Mallets Bay Boat Club. Last race of the first day - wind clocked to the northwest and picked way up (probably was hitting 20 or so). We had the kite up on the first downwind and I thought the spinnaker halyard blew or something when it started to come down but then the rest of the sails went forward over the bow with the entire mast above the deck. As it ended, the backstay block on the stern ripped up and the backstay fitting on top of mast blew, not sure which caused which. Either way, we lost any backstay tension and the entire mast whipped forward and snapped at the spreader and then at the deck.
Looking at the damage after the fact it was pretty obvious that a) the mast had a lot of salt water corrosion on the inside, probably from a capsize and not being fully washed or something, and b) the backstay block must have done the same thing in the past and was repaired with a pretty thin layer of fiberglass, which ended up blowing out under pressure. Solution: I recruited my friend Aidan to help me re-glass the deck.
Step 1: Cut out broken fiberglass
After removing the block and sanding off the gelcoat, we took a Fein tool oscillating saw and cut out any of the glass that was broken or cracked, which ended up being almost a 5 inch diameter circle. Then we made sure to take off any of the gelcoat around the hole on the top and underside of the deck to give new fiberglass something to hold on to.
Step 2: First fiberglass layer
Next we laid out one large piece of woven glass mat on the underside of the deck to cover the entire hole. This needed to be formed to the right angle of the deck and transom to really get enough hold area.
Step 3: Fill hole in deck with fiberglass layers
The next few layers of glass mat were cut to the size of the hole, and then used to fill the entire gap. The layers in the stack switched up their orientation to have some 90 degree layers, and some at a 45 degree angle. This step got a little messy - I would have liked it to be a little smoother / also to have gotten the resin a little more consistent in some spots.
Step 4: Last fiberglass layer
The last mat layer was over the entire top of the hole, the goal being to bind the new glass in the filled hole to the deck the same way the bottom layer does, making almost a sandwich. This didn't really look the prettiest since there's now a bump above the rest of the deck where the new glass is, but it seemed like the best way to make sure the block was going to have the strength it needs, and didn't have last time it was repaired.
Step 5: Prep for epoxy deck layer
The deck had been done a year before I bought the boat with Petit EZPoxy, an epoxy that gets painted on instead of gelcoat. After sanding down the new fiberglass, and using the fein tool to re-cut the hole to mount the backstay block, I primed the whole area.
Step 6: Epoxy the deck
Epoxied the repaired area.
Step 7: Deck is done!
When we did this part of the repair, it was the night before the New England Districts at Lake Massabesic in New Hampshire, so we actually got it done a little later in the night then I would have liked, and had to pack up and cover the boat before the epoxy was 100% dry, so it ended up getting a little dirty. Just cosmetic, but if it wasn't rushed, probably would have looked better.
Step 8: New mast
The last piece of the puzzle - new mast! Well, really I was given two older masts, and between these and my broken one, I pieced together a good mast. This was all credit to some great lightning sailors who spread the word that I was looking for a mast and helped connect me with these.
Results
We sailed the rest of the year (another 4 regattas) with the repaired deck and the new (to us) mast and it all help up well. There were a few days of heavier winds and everything seemed to be good. At least, good enough that it couldn't be an excuse for bad results!