Hi Graham,
Further to my last the rounded rudder blade requires 4.5 inches adding to the outside edge at the bottom. This extra piece of wood is tapered to nothing at the forward edge and covered in fibreglass and fibre-glassed to the original blade.
When you are intending to tack, sail as fast as you can in the conditions and turn the wheel hard over but don't release the foresail until the boat is through the eye of the wind. You must however release the sheet of the mizzen or she will not go round.
You should be able to tack in any strength of wind and even light winds but use your sails to drive her round. You should not need to touch the engine.
I don't recall having a problem with this in Rouselle once the rudder was sorted and I had her for 37 years and covered over 30,000 miles in that time. You must however release the tension of the mizzen sheet.
I have just retired from 73 years of pottering under sail and in the early days we did not have an engine. We didn't miss it as no one had them. We did however learn to sail your boat in all conditions. For example I had a twenty one foot sloop that I built in my front garden. When she was in the water I could move forward when there was no wind at all. Hoist the main and the jib and sheet in. Stand on the portside deck just forward of the centre line and hold on to the mast. The boat will move slowly forward and curve to the left, then do the same on the starboard deck and it will curve to the right. Using that method you can negotiate a narrow waterway out of the harbour. I have not tried that with the seadog but I expect they are far to heavy to take any notice of a person standing on the deck!
Best wishes to you all
Brian