26 Dec 20:
Time to reattach the forward port side internal structural foam block, which also serves as flotation. We turned WAVE on her side today so we could pour the adhesive foam in and let gravity do the work of moving it between the structural block and the fiberglass hull.
Found some artifacts rattling around inside the hull, on of them Capn Jack's bow handle backer plate. Video: Flotation Block and Hull Repair https://youtu.be/dNZZ6dT6jpc
The Sunfish made from 1960-2020 have 6 internal extruded polystyrene (XPS) structural foam blocks inside, 3 forward of the cockpit and 3 aft. These blocks are made from closed cell foam to resist water intrusion, and are held in place by 2 part marine grade flotation foam. The 2 part foam was at first poured, in the 1960s and early 70s, then a foam gun was brought in and as our friend, who worked at Alcort, Howie relates, "foam went everywhere."
Today we used TotalBoat 2 Part Polyurethane Flotation Foam. It is 94% closed cell, so it can get wet but should not be immersed for extended periods...neither should the innards of a Sunfish :)
A couple of notes about pouring foam, small amounts are best for us with multiple pours as needed:
-A LITTLE GOES A LONG WAY (ALGALW), the foam will expand easily to 10 times the amount poured.
-CAUTION: Wear protective gear, long sleeve shirt, gloves, long pants, the foam is a tenacious adhesive. The only time I thought I might need to go to the emergency room for building projects was when I got a lot of foam on one hand, I couldn't get the foam off for several hours, it dries hard, and I knew how the ER folks would want to deal with it. The product that took off the last of the adhesive was Harco's Miracle Wipes for Paint, lots of unpronounceable chemicals, so proper protective equipment would have been a better way to go.
There is strategy involved with a foam pour:
-The foam expands quickly, so how will you get the foam to the area you want in an expeditious manner? Some folks tape a small cup to a paint stick to reach remote areas, but place that cup outside on the concrete with done, and not the good concrete, the cup will probably melt.
-How much time do you have with the foam? Once it starts to expand, even a little, there is only a few minutes to get it poured, as it skins over quick. We also can feel the mixing cup start to get warm, time to pour.
-Work from the farthest area back to the closest.
-Orient the work piece so that the foam will run into the desired areas, strategic pieces of blue tape can help channel the foam until it skins over. One of Howie's tricks was to make little blue tape walls around the top of a flotation block to hold the foam so it doesn't run down the side of the block, then clamp down the deck while the foam expands.
-Speaking of blocks, they need to be held in place while the foam expands, or they can get moved out of position. We hold them for a few minutes when we can, or have used tape and paint sticks to hold them. At the factory they would pour the bottom of the block first and place bars over the top of the blocks, so they didn't rise above the deck crown. When they poured the top of the block, it seem like they may have inverted the boat, as there is not much foam running down the side of factory boats. But once the top of the block is poured, the deck/hull seam needs to be clamped shut while the foam expands, or else you might not be able to close the seam later.
Before we mixed foam I tacked the flotation block in place with Great Stuff insulation foam. We don't use Great Stuff for the entire block because it is not closed cell and can absorb water quickly. Next I poured TB Flotation Foam Part A Resin and Part B Activator equal amounts in 2 separate cups, then mixed in one cup. You could also pour in one mixing cup using the mixing ratio index marks on the side of the TotalBoat cups, which come with the Foam Kit. I poured to the lowest 2 mark on the 1:1 index, not much product, but as mentioned, ALGALW.
First pour, runny enough to get into the void but starting to expand.
Leftover foam. There is a photo below that shows how much it expands in just a few minutes.
We used this stick wedged against the daggerboard trunk to hold the aft end of the flotation block in place while the foam expanded, then removed it before the foam fully hardened. There are some boats out there that still have little stick remnants in them :)
First small pour, foam still expanding.
After about 5 minutes the cup is full, started off with just a little skim of foam on the bottom.
We let the foam tack up for a few minutes then finished rolling WAVE over, time for some finish sanding on the hull. We used 60 grit pads on a DeWALT random orbital sander to remove excess thickened epoxy and whatever bottom coating that had been applied to SALLY's hull. Dust collection system is a Dust Deputy cyclonic separator attached to a ShopVac.
Faired the seam with the sander, the new section was a bit proud along the seam.
Filled in the bigger nooks and crannies with TotalBoat THIXO Wood thickened epoxy. Why Wood? Because that's what we had. Even though the seam is water tight and there is a fiberglass seam plate inside the hull, we wanted the structural component of THIXO for the larger gaps. Faired over small nooks and crannies with TotalFair
We'll let this dry, smooth it down and go over the whole area with another coat of TotalFair.
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