navigation on a river/how a rudder works...

[bikesnotbush]

Hi, My name is Eric.. This is my first post.
I don't know very much about boats yet.. but I want to learn, and thats why I came here.
I have a question that might seem stupid.. but I don't know, and I figure it doesnt hurt to ask.

I'm in the process of making a small plywood pontoon boat.. one that I can take down small rivers here in michigan.. and to fish off of in a lake.
obviously I would need propulsion for the lake.. but is there a way to navigate a river without propulsion? so what im really asking is..
will a rudder steer a boat that is riding the current?
and if not.. is there another way to keep to boat facing forward.. and steer around obstacles without a motor? any help is appreciated.
-E

yes in short a rudder will
Sometimes I see 3000 tonne ships coming down the Rhine, the engine is in gear, the current does 9 knots,and the rudder, has a job to do
pontoon boat? um, what about a wide beam rowing dory?

[SamSam]

Originally Posted by bikesnotbush

.. but is there a way to navigate a river without propulsion? so what im really asking is..
will a rudder steer a boat that is riding the current?
and if not.. is there another way to keep to boat facing forward.. and steer around obstacles without a motor? any help is appreciated.
-E

Welcome, Eric.

A rudder without propulsion won't work when drifting at the same speed as the current any more than it will work when sitting in a currentless lake. You have to have water flow past the rudder so it has something to react with, so you have to be going faster or slower than the current.

If it's shallow, you can use a pole to maneuver, otherwise a paddle or oars will work.

[eponodyne]

I currently work as a deckhand on riverine towboats on the US. Mississippi (what a fun word to type), Ohio, Illinois, Missouri, Tennessee, Tennesaw, Tombigbee, Black Warrior, WHite River... rode 'em all.

The boats vary in details, but they are essentially a very deep-chested jonboat type with considerable tuck aft (for zero shaft angle and room to swing a wheel 6 feet or more across). They have enormous rudders behind the wheel, and pairs of smaller rudders forward of the wheels to provide control when backing down. We may come downstream just idling, but the engines are always turning and the gears are always engaged. I've never, in 12 years of doing this, seen a boat knocked out of gear for very long.

The thing to remember about them is that there has to be water flow over the rudder for it to be effective. You don't necessarily have to have speed over ground but water has to be moving past the vessel.