Monday, August 24, 2009
Rudder and Steering
The rudder on my trawler is a rather large device. The approximate dimensions are 2.5' wide by almost 5' tall. Having installed the rudder a few times I'm going to guess it's weight at 200+ lbs. The rudder looks more like a wing and is constructed in such a way as to have two skins wrapped around the wing shaped frames. It is very sleek looking and more reminds me of a sailboat rudder vs a rudder you would see on a work boat. Compared to the rudders I see on house boats around my home port, this rudder has a tremendous amount of square footage to aid the steering of the boat. By looking at the rudder alone, I would guess this boat will be very responsive to the steering wheel. Becuase of the way the rudder is fabricated it is impossible to paint the inside to protect the steel. Because of this type of rudder construction I air tested the rudder to 10 psi to insure that no oxygen gets inside of the rudder and speeds up rust corrosion.
The rudder is connected to the boat via a large skeg or shoe that is an integral part of the keel. The rudder has 2" stainless stock welded to itself that is flanged on both the top and bottom of the stock. The bottom flange bolts to another flanged piece of 2" stock that sits in a bearing in the skeg. The top flange bolts to piece of 2" flanged stock that passes through a bearing that goes up into the lazzarette of the boat ( rear room) and connects to the steering gear. The flanges for the rudder system I fabricated out of 3/4" stainless stock and bored them to accept 5/8 bolts to hold them together. I'll have to design some sort of locking ring to retain the nuts or use a castle type nut with a key to hold the nuts fast. The bearings for the rudder in the skeg and where the rudder stock enters the boat @ the lower end of the rudder log ( rudder tube) are made from a material called Vesconite. Vesconite is designed just for this application and is claimed to be top of the line material for what I'm trying to do with it. I will not have any galvanic worries with this type of rudder bearings.The rudder tube terminates inside of the boat about 8" above the water line. I added another bearing at this point of termination for a total of three rudder bearings. With the rudder installed I'm able to move it with just a little pressure from my finger tips. I'm totally happy with the bearings and the rudder alignment. Because of the mix of a stainless steel rudder shaft and mild steel boat I will add a zinc or magnesium annode to the rudder to slow down any galvanic corrosion.
The actuall steering system on the trawler will be what most would consider a power steering system. My main engine has a port on it to accept a pump that will power the steering helms that in turn will power the hydraulic rams connected to the rudder shaft. I will have two helms on my boat; one helm in the wheel house, and another helm on the roof as a fly bridge. In case of a catastrophic failure of the steering system, I have an emergency tiller device in place to steer with ( see my earlier post " emergency tiller"). The hydraulic rams are more a heavy duty set up I purchased from Hydro Slave Co. The steering gear consists of a heavy cast bronze quadrant, two hydraulic rams, and an integral arm to limit travel of the rams. If you look at the first picture posted you will notice my attempt at rudder stops welded to the hull. I know they look a bit odd, but at least I made some attempt at aero dynamics and they also wont increase any corrosion issues. The quadrant connects to the rudder shaft via a heavy clamp and a 1/2" stainless key way and key. I went with this type of dual ram set up becuase it causes zero side load on the rudder shaft. I am totally pleased with this piece of equipment, and while it was pricey, I feel it was money well spent. I'll be adding to this blog once the steering system is fully connected and operational with the helm pumps in place along with the hydraulic lines.