I have completely filled all the hull joins including removing all the tabs and filling the gaps left under them. I did this work yesterday (4 hours until the heat got to me) and today I have started on the gap in the keel. I started by selecting an appropriate off-cut and then measuring the gap and marking the off-cut to suit. I started at 5mm wide, figuring any thinner would be both too hard to cut and too hard to glue in place, all the gap less than that will get some filler. I measured the gap at 1mt intervals and transferred the gap sizes to the off-cut and then just marked a straight-line between the points (the gap was 12mm at 1mt, 20mm at 2mt, 25mm at 3mt, 25mm at 4mt, 20mm at 5mt, 15mm at 6mt, 12mm at 7mt and 6mm at 8mt). Then it is a simple job to cut along the line with a jigsaw. A tip here (thanks Sean) is to cut at a slight angle so that the piece is slightly narrower at the bottom so it fits into the gap better, you can fill the gap from the inside when you turn the hull and glass the inside. In the photo of the jigsaw I have exaggerated the angle to show the angle but only a few degrees are needed to make the piece easier to fit. Here and there the pieces were still too wide, I marked them with a felt pen at the wide spots and removed them with the jigsaw and I then had a fairly tight fit.
Once I had cut the pieces I needed (I needed 2 pieces as the gap narrowed to nothing then flared again, I started gluing the first piece in. I mixed some glue (403 powder, resin and hardener) and pasted the inside of the gap, and then once I had pushed the piece down into the gap I filled the rest of the gap with glue by pressing it in with a spatula as if it were filler. And the result you can see is a fairly tightly filled gap that will harden as if it were one piece again. I ran out of time on Friday so it is a fairly simple (remember Murphy’s law!) job to glue the other one in and then fill the remaining gaps with filler.
The Duflex is acting as a core for the sheets of glass that are going to be laid both sides of the hull (inside and out) under the waterline so there is no loss of structural integrity by cutting strips of Duflex and filling in this way. Some boats are made entirely of strips of Duflex or other material such as ceder. I am just making a smooth bed for the glass to adhere to. I am happy with the job I have done. Just like a bought one!
Next job is to spot fill any remaining gaps and all the screw holes with a 50mm syringe full of not so thick filler, then when dry, sand all the filler away to a smooth surface for the glassing. I am in Melbourne for a family wedding this weekend so I will get back to it Monday. The keel gap filling was a lot easier than I thought it would be and I am now ahead of schedule by a day or 2 so I am fairly confident I can have it all sanded ready for glass by the end of the week.