Core rot. The bane of many owners around here. I took the less-popular repair approach of coming from the top. Given the condition of my deck, I figured either way, I need to refinish this area. Plus, I couldn't bear the unholy mess it would make on the inside. The deck had noticeable give to it when I lightly stepped on it; I was afraid to put my full weight on it. Being a potentially high traffic area, I've wanted to fix it since I bought the boat last year.
Up-front, here's what I used: Divinycell 4lb density scored foam (1/2" is the correct thickness based on measurements of the balsa - 3/8" was just a bit too thin); TotalBoat High Performance 2:1 epoxy; milled glass fibers, cabo-sil thickener, 1708 cloth, TotalBoat Thixo. I used a Dremel oscillating saw for cutting (it worked like a dream).
Here's what I had to start with. I suspect the water is mainly getting in from the two cheek blocks on the deck. However, I suspect the water is ALSO getting from the hole where the wires penetrate the deck (under the mast). It might also be around where the handrails attach - I haven't dug into that yet (but will). I'm viewing this as an iterative process.
After removing the hardware, the holes were very much unsealed. I was later amazed at how far the water had traveled. I marked off the first area I wanted to cut (after tapping around with a plastic mallet listening for changes in sound). The skin peeled off easily and I saw formed pieces that were all saturated.
I found a flat bar to be very effective at removing material. Here it is mostly cleaned out. I used the flat bar to scrape up under the areas you can see of the non-skid and pulled out mushy balsa from there, too.
I noticed that the mush seemed to extend further forward. After more tapping, I drew another shape. I did clear out the little "bridge" between the sections, but wanted to break up the skin pieces into smaller chunks to make them easier to work with.
Again, scraping with the flat bar as far as I could. I'll note that as I got closer to the mast, I did encounter plywood. It was wet, but not rotting. That was encouraging. I left everything completely open to dry (in 80-85 degree sunny days) for about a week. Upon my return, I found it to be quite dry.
Like a big puzzle, I worked hunks of Divinycell into the space. In the areas where I dug under the intact skin, I slid the pieces under to cover the areas as best as possible. I used narrow strips to test the depths here and there and I think I got pretty good replacement this way using odd-shaped pieces where you can't see them.
I'll mention again that I bought 3/8" foam when I should have bought 1/2" for this area. To compensate (and bring some extra strength), I put a layer of 1708 cloth down under the foam layer.
The pictures get sparse here because I was in the middle of mixing batches of epoxy and getting things in place. I used thickened epoxy with milled fibers in it to "thicken" up remaining gaps. For the foam pieces I had to slide under the intact deck, I generously buttered them up with thickened epoxy before sliding them in. I went back with a tube of Thixo and pumped it into remaining gaps on the blind edges. I let that sit for a couple of hours to cool.
Another layer of thickened, strengthened epoxy on top of the foam, and then I put the skin back in place. I estimate about 10 pumps of the TotalBoat 2:1 thickened epoxy (peanut butter consistency) per layer, per opening.
After both panels were in place, I put some thick plastic over the top and weighted it with some sandbags. I tried starting with the larger bags of sand, but I didn't have enough to completely cover the whole area evenly, so it was actually bowing the ends up. I filled small bags with the sand and placed them around the edges. It held them down sufficiently without excess epoxy squirting out the edges.
Here's the final pictures with them removed after a few hours. Since I was going to be leaving it for the week, I decided to leave it open to take advantage of the warm days for good curing.
Next steps are to grind proper margins and put some cloth on to strengthen the joints, fairing, primer, then gelcoat. I'm going to sand this entire section of non-skid and use SoftSand in between coats to replace the molded-in non-skid. Eventually I'll make it uniform on all the non-skid up front, but for now, prioritizing function over looks.
Thanks to all of you here that have documented this process in the past so I could learn from it. Extra shout-outs to @trickdhat and @gargrag for their recent advice and encouragement.
Up-front, here's what I used: Divinycell 4lb density scored foam (1/2" is the correct thickness based on measurements of the balsa - 3/8" was just a bit too thin); TotalBoat High Performance 2:1 epoxy; milled glass fibers, cabo-sil thickener, 1708 cloth, TotalBoat Thixo. I used a Dremel oscillating saw for cutting (it worked like a dream).
Here's what I had to start with. I suspect the water is mainly getting in from the two cheek blocks on the deck. However, I suspect the water is ALSO getting from the hole where the wires penetrate the deck (under the mast). It might also be around where the handrails attach - I haven't dug into that yet (but will). I'm viewing this as an iterative process.
After removing the hardware, the holes were very much unsealed. I was later amazed at how far the water had traveled. I marked off the first area I wanted to cut (after tapping around with a plastic mallet listening for changes in sound). The skin peeled off easily and I saw formed pieces that were all saturated.
I found a flat bar to be very effective at removing material. Here it is mostly cleaned out. I used the flat bar to scrape up under the areas you can see of the non-skid and pulled out mushy balsa from there, too.
I noticed that the mush seemed to extend further forward. After more tapping, I drew another shape. I did clear out the little "bridge" between the sections, but wanted to break up the skin pieces into smaller chunks to make them easier to work with.
Again, scraping with the flat bar as far as I could. I'll note that as I got closer to the mast, I did encounter plywood. It was wet, but not rotting. That was encouraging. I left everything completely open to dry (in 80-85 degree sunny days) for about a week. Upon my return, I found it to be quite dry.
Like a big puzzle, I worked hunks of Divinycell into the space. In the areas where I dug under the intact skin, I slid the pieces under to cover the areas as best as possible. I used narrow strips to test the depths here and there and I think I got pretty good replacement this way using odd-shaped pieces where you can't see them.
I'll mention again that I bought 3/8" foam when I should have bought 1/2" for this area. To compensate (and bring some extra strength), I put a layer of 1708 cloth down under the foam layer.
The pictures get sparse here because I was in the middle of mixing batches of epoxy and getting things in place. I used thickened epoxy with milled fibers in it to "thicken" up remaining gaps. For the foam pieces I had to slide under the intact deck, I generously buttered them up with thickened epoxy before sliding them in. I went back with a tube of Thixo and pumped it into remaining gaps on the blind edges. I let that sit for a couple of hours to cool.
Another layer of thickened, strengthened epoxy on top of the foam, and then I put the skin back in place. I estimate about 10 pumps of the TotalBoat 2:1 thickened epoxy (peanut butter consistency) per layer, per opening.
After both panels were in place, I put some thick plastic over the top and weighted it with some sandbags. I tried starting with the larger bags of sand, but I didn't have enough to completely cover the whole area evenly, so it was actually bowing the ends up. I filled small bags with the sand and placed them around the edges. It held them down sufficiently without excess epoxy squirting out the edges.
Here's the final pictures with them removed after a few hours. Since I was going to be leaving it for the week, I decided to leave it open to take advantage of the warm days for good curing.
Next steps are to grind proper margins and put some cloth on to strengthen the joints, fairing, primer, then gelcoat. I'm going to sand this entire section of non-skid and use SoftSand in between coats to replace the molded-in non-skid. Eventually I'll make it uniform on all the non-skid up front, but for now, prioritizing function over looks.
Thanks to all of you here that have documented this process in the past so I could learn from it. Extra shout-outs to @trickdhat and @gargrag for their recent advice and encouragement.
