tolhurstorganic
Member
I have a problem of delignification of a small lengthwise piece of aft deadwood at the bottom lower end piece of deadwood.
Bottom corner of rudder showing similar patch, and outer stem on bow showing some delig. around area in line with ballast keel.
I suspect that the hull is overzinced.
Anodes (as recommended by MG Duff) after 3 seasons permanently afloat still largely intact. Shaft anode shows most wear but still more than 60% sound. Hull anodes showing crust of calcium looking material. There is no visible corrosion damage to any metal components anywhere. Anodes:
1. Keel, fastened direct to, with steel bolts and backing pad 2 x ZD78B. 4kg (MGDuff)
2. Rudder lower fitting hanging 1 x ZD59 0.5kg bolted direct to fitting.
3. Hull stern. ZD76 bolted through hull onto backing pad connected to Stern gear and bonded to 4
4. Middle rudder fitting bonded to above.
5. Sintered bronze heat exchanger to fridge fitted 2 x anodes. Wired to negative post engine battery.
6. Prop shaft fitted anode to prop nut.
7. Engine has anode fitted to raw water heat exchanger
Materials:
Keel and all frames laminated Oak. Planking cedar strip with two layers oak diagonal bonded.. Dead wood oak. Hull below waterline treated with 8 coats epoxy resin and finished with "Coppercoat" anti-fouling. Keel 12mm steel plate box filled with molten lead. Fastened 25mm 316 S. Steel keel bolts to hog and S. Steel 316 floors. Keel insulated from hull by rubber mastics.
Deadwoods and all timbers below water fastened bronze bolts. Prop shaft S. Steel, Propellor Mag. bronze (Vetus) Rudder hangings S. Steel 316 Bolted 316. Sea cocks all Bronze and bronze fastenings (Taylors) Fridge heat exchanger- sintered bronze.
Given that there is absolutely no corrosion to any components other than the oak it seems that there are too many anodes. I would rather have some corrosion on prop than decay of wood. The infected area is relatively easy to repair but I am concerned for the longer term and need to know what I should do. Maybe remove all anodes? I will speak to MG Duff but lack any confidence in their advice as it would appear to have been incorrect. I am suspicious about the fridge heat exchanger being connected to battery earth it was done on the manufactures instructions. I am not too excited about the 316 ss keel bolts.
Would welcome anybodies advice or thoughts on this problem.
Bottom corner of rudder showing similar patch, and outer stem on bow showing some delig. around area in line with ballast keel.
I suspect that the hull is overzinced.
Anodes (as recommended by MG Duff) after 3 seasons permanently afloat still largely intact. Shaft anode shows most wear but still more than 60% sound. Hull anodes showing crust of calcium looking material. There is no visible corrosion damage to any metal components anywhere. Anodes:
1. Keel, fastened direct to, with steel bolts and backing pad 2 x ZD78B. 4kg (MGDuff)
2. Rudder lower fitting hanging 1 x ZD59 0.5kg bolted direct to fitting.
3. Hull stern. ZD76 bolted through hull onto backing pad connected to Stern gear and bonded to 4
4. Middle rudder fitting bonded to above.
5. Sintered bronze heat exchanger to fridge fitted 2 x anodes. Wired to negative post engine battery.
6. Prop shaft fitted anode to prop nut.
7. Engine has anode fitted to raw water heat exchanger
Materials:
Keel and all frames laminated Oak. Planking cedar strip with two layers oak diagonal bonded.. Dead wood oak. Hull below waterline treated with 8 coats epoxy resin and finished with "Coppercoat" anti-fouling. Keel 12mm steel plate box filled with molten lead. Fastened 25mm 316 S. Steel keel bolts to hog and S. Steel 316 floors. Keel insulated from hull by rubber mastics.
Deadwoods and all timbers below water fastened bronze bolts. Prop shaft S. Steel, Propellor Mag. bronze (Vetus) Rudder hangings S. Steel 316 Bolted 316. Sea cocks all Bronze and bronze fastenings (Taylors) Fridge heat exchanger- sintered bronze.
Given that there is absolutely no corrosion to any components other than the oak it seems that there are too many anodes. I would rather have some corrosion on prop than decay of wood. The infected area is relatively easy to repair but I am concerned for the longer term and need to know what I should do. Maybe remove all anodes? I will speak to MG Duff but lack any confidence in their advice as it would appear to have been incorrect. I am suspicious about the fridge heat exchanger being connected to battery earth it was done on the manufactures instructions. I am not too excited about the 316 ss keel bolts.
Would welcome anybodies advice or thoughts on this problem.
