Rudder design

[Csail]

Our boats rudder is or seems to be a one off design (as all the Colvics are diferent) so i am thinking of getting a bigger one made to give better steering . The current one is mild steel and is corroded and very stiff to turn so i'm thinking of ss steel. Any points i need to think of if i do change it for something bigger?

 

[Bajansailor]

Does it need to be bigger, and if so, how much bigger (height and length wise) can you make it?

Re how it is very stiff to turn - this could be that it has rusted (hence expanded) a bit inside the bearing, or maybe the bearing has expanded a bit by taking up water (?) and is pressing on the rudder stock?

If you add some more area forward of the stock on the new rudder, this will make it less unbalanced, and hence easier to steer (is your steering via a quadrant on the rudder stock?).

Most of the commercial fishing boats here have S/S flat plate rudders, with about 15% of the plate area forward of the stock, and they seem to work quite well. Some have anodes on them, some dont.

If you wanted to be very sophisticated, you could build a nice hollow aerofoil shaped S/S rudder, but that would be getting rather complicated and expensive.

 

[hmm]

Can you go for a semi-balanced rudder?

Doesn't ss suffer corrosion if submersed for long periods? (It needs air to remain rust free)

 

[roly_voya]

When you say better steering what is the problem currently - heavy, stiff or dosn't steer the boat?

 

[Evadne]

[ QUOTE ]
Doesn't ss suffer corrosion if submersed for long periods? (It needs air to remain rust free)

[/ QUOTE ]

It needs oxygen, which is present in the surface layers of seawater. If it is enclosed, the water can become anoxic, for example in the thread between a nut and a bolt, and crevice corrosion can occur. A s/s plate, with pivot bars top and bottom into bearings, might be susceptible at the bearings, but I don't see that it would be any different to, say, a propshaft, and I know my 21 year old rudder stock is stainless, and seems ok at the end of each season. A hollow fabricated rudder, with flooded nooks and crannies, may be another matter.

 

[Csail]

Current problem is the stock is mild steel and i think corrosion has made it stiff. The current rudder has about 10% forward but still could do with being a bit bigger.Also where the hyd. ram joins quadrant the hole is worn so thats why i think i might aswell change the whole setup.

 

[Caer Urfa]

The rudder on my Colvic Watson 24' is stainless steel but it was then built up by coating in GRP to about 10mm thick each side.
Works well and no corrosion! Just gets a coat of antifoul.
If you need pic e-mail

 

[William_H]

A rudder on a yacht is asked to do a lot of work when the boat is over powered because the boat wants to turn to windward. This is just the time when the rudder is approaching 45 degrees to vertical so that the rudder is only 50% effective. The rest of the effort is trying to lift the stern.
This then is a time for a deep rudder that has a decebt anount of balance balanced to ease helm loads.
If the rudder hangs down in the water below the bottom pintle or bearing then you could try a fibreglass and foam extension to the bottom of the rudder. This can have a large area forward of the shaft to increase balance and the added depth will give better effect.
The f/g and foam is designed to break off if anything gets caught or you hit rocks etc so no damage is done to the original rudder.
The extension may not last that loing but should be good enought o give you experience of whether an extended rudder is worth having.
All this assuming you can fix the old rudder. good luck olewill

 

[Csail]

Can't really go down as we dry out but i was thinking of making more surface area by going fore / aft. I'll try and find a pic , that will help.