The photos sure help in many ways. That was severe core disruption you found by the screw holes. Had the boat been through a number of freeze thaw cycles? Especially if the boat was left out in freeing areas. Was the boat run hard? I realize that you cannot answer these questions, and if you cannot find out, then are rhetorical.
How wide is this gap between the new balsa and the remaining core at the very edges--or is there remaining core outside of the new core? You can fill these areas with a light filler and epoxy mixture. For example microballoons come to mind. I have seen failure in micro balloons on outside fairing after many years--I don't think that would be an issue here, and my recollection is that the microballoons were with a polyester resin in all cases--I might be conflicted here by the choice of polyester for the filler combined with microballoons and cabosil...because of the much higher cost of the epoxy. I would mix some cabosil in with the microballoons.. Both of these are appropriate repairs. I would limit this balsa unfilled area to less than 1/2" in width if possible.
An aside: often when putting structural bulkheads onto a boat, foam is cut in a trapezoid shape to stand the bulkhead off the hull for about 3/8" to 1/2" so the bulkhead is not a hard place in the hull, and could cause fiberglass fatigue. We then would build the filet and put in 3-4 layers of tabbing of cloth/mat to secure the bulkhead on both sides. You might consider the floor, in being somewhat similar to a bulkhead, and bring the top layers of glass concentrically up the side of the hull (in our Caracal, we will be leaving 2 to 3" of the old "floor" along the sides, and then sweep the new top layer over this and up the sides of the hull.) For building bulkheads we would first use a "tic board" to find the rough contours, then make a cardboard template, double check its fit before cutting the marine ply we were using as the bulkhead. One could use a laminate panel as a major bulkhead, as I believe Tom Hurby noted that his new C Dory 22 is being built with a hollow core material in at least part of the construction.
Does anyone know what the original laminate schedule of the C Dory 16 floor (inner aspect of the hull) was? Today I would probably go with a of layer of 1708 and 1808 each. That would be a very strong floor-perhaps stronger than the initial laminate. This series of laminates use bi-axial fibers: 1708 bundles of fibers are at 45 degrees. The 1808 fibers are at 90 degrees. The 1708 goes around corners more easily. But there is difference in panel strength between the two.
In the past the builders might use a layer of roving (18 to 24 oz) in the inner aspect of the floor (hull bottom), The outer laminate should have at least one layer of 18 to 24 oz roving when first built. Today with the biaxial and tri axial cloths there may be a different laminate schedule and a good chance the boat would be lighter as well as stronger.
How wide is this gap between the new balsa and the remaining core at the very edges--or is there remaining core outside of the new core? You can fill these areas with a light filler and epoxy mixture. For example microballoons come to mind. I have seen failure in micro balloons on outside fairing after many years--I don't think that would be an issue here, and my recollection is that the microballoons were with a polyester resin in all cases--I might be conflicted here by the choice of polyester for the filler combined with microballoons and cabosil...because of the much higher cost of the epoxy. I would mix some cabosil in with the microballoons.. Both of these are appropriate repairs. I would limit this balsa unfilled area to less than 1/2" in width if possible.
An aside: often when putting structural bulkheads onto a boat, foam is cut in a trapezoid shape to stand the bulkhead off the hull for about 3/8" to 1/2" so the bulkhead is not a hard place in the hull, and could cause fiberglass fatigue. We then would build the filet and put in 3-4 layers of tabbing of cloth/mat to secure the bulkhead on both sides. You might consider the floor, in being somewhat similar to a bulkhead, and bring the top layers of glass concentrically up the side of the hull (in our Caracal, we will be leaving 2 to 3" of the old "floor" along the sides, and then sweep the new top layer over this and up the sides of the hull.) For building bulkheads we would first use a "tic board" to find the rough contours, then make a cardboard template, double check its fit before cutting the marine ply we were using as the bulkhead. One could use a laminate panel as a major bulkhead, as I believe Tom Hurby noted that his new C Dory 22 is being built with a hollow core material in at least part of the construction.
Does anyone know what the original laminate schedule of the C Dory 16 floor (inner aspect of the hull) was? Today I would probably go with a of layer of 1708 and 1808 each. That would be a very strong floor-perhaps stronger than the initial laminate. This series of laminates use bi-axial fibers: 1708 bundles of fibers are at 45 degrees. The 1808 fibers are at 90 degrees. The 1708 goes around corners more easily. But there is difference in panel strength between the two.
In the past the builders might use a layer of roving (18 to 24 oz) in the inner aspect of the floor (hull bottom), The outer laminate should have at least one layer of 18 to 24 oz roving when first built. Today with the biaxial and tri axial cloths there may be a different laminate schedule and a good chance the boat would be lighter as well as stronger.