Just how thick should the rudder be?
QOur rudder is about one inch thick which is making the tiller hard to handle. Is there a guide or chart giving an idea of the size and thickness of steel that boat builders use so that we can check ours?
ALAN THORNTON, via email
ATONY REPLIES: I am far from sure that rudder thickness is your problem. If you are a new boater and only have problems when underway, it might mean you are trying to drive the boat too fast for the canal. It’s possible to lose control at higher speeds when the water flow around the hull interacting with the canal bed overrules the rudder
The balance part of your rudder (the bit in front of the stock) looks rather small – it’s said that it should be about one third of the size of the rest of the rudder. This would tend to produce heavy steering when underway but less so when stationary. It will not be easy to correct this because there is also a minimum ideal distance between prop and rudder.
If it is difficult to turn (and possibly noisy) even when stationary, the stock could be binding in the rudder tube – either because it has rusted, the rudder has been caught on a lock cill at some time, or the boat has reversed into something solid, bending the stock. If the upper bearing uses ball bearings, these could have rusted and partially seized. If it is made of a plastic material and allowances haven’t been made for swelling up when wet, that would also cause a stiff tiller.
Having said that, one inch does sound rather thick to me: there is no guide but 10mm to 12mm is more usual (one inch is 25.4mm). As your bottom bearing is just a cup on the skeg, a heavy rudder would create friction and stiffness.
You could try putting a brass or copper washer in the cup under the stock as a kind of bearing, but I suggest you consult an experienced boatyard to find out what the problem really is.