This is probably an incredibly naive question, and I apologise if it's a
FAQ, but it's one of those things that I was pondering on in an idle moment.

Why is it that on all boats, the rudder is at the back rather than the front
of the boat? Is it:

- because a rudder at the front simply wouldn't work properly to steer the
boat?

- because a rudder at the back gives greater manoeuvrability, in the same
way that dumper trucks on building sites have rear-wheel steering whereas
cars and lorries have front-wheel steering?

Martin Underwood wrote:

- because a rudder at the front simply wouldn't work properly to steer the
boat?

It should work okay, or reversing wouldn't work on boats with rudders.

- because a rudder at the back gives greater manoeuvrability, in the same
way that dumper trucks on building sites have rear-wheel steering whereas
cars and lorries have front-wheel steering?

I think it's possibly a matter of general utility. On a dumper truck or
a fork-lift you don't want the steering to interfere with the mechansim
of the skip or lifter. On a boat you don't want your steering mechanism
to be the first thing to collide with obstacles you may encounter...

Pete.
--
Peter Clinch University of Dundee
Tel 44 1382 660111 ext. 33637 Medical Physics, Ninewells Hospital
Fax 44 1382 640177 Dundee DD1 9SY Scotland UK
net http://www.dundee.ac.uk/~pjclinch/

On Mon, 10 May 2004 10:48:22 GMT, "Martin Underwood"
wrote:

|This is probably an incredibly naive question, and I apologise if it's a
|FAQ, but it's one of those things that I was pondering on in an idle moment.
|
|Why is it that on all boats, the rudder is at the back rather than the front
|of the boat? Is it:
|
|- because a rudder at the front simply wouldn't work properly to steer the
|boat?
|
|- because a rudder at the back gives greater manoeuvrability, in the same
|way that dumper trucks on building sites have rear-wheel steering whereas
|cars and lorries have front-wheel steering?

It's to do with displacement. A displacement hull is designed to
'fend off' water whilst travelling forwards.
A rudder at the front would stop the displacement hull working
effeciently unless you are travelling in a straight line. So - it
slows the boat down.

Also, Because the boat is designed to go at maximum speed when
going forwards, the water stream passing under and around the
boat is much more stable and reliable as a medium than the water
you have not yet hit! Effectively, the water speed and direction
helps the rudder to do it's job. A rudder hinders the effeciency
of this water stream, this is how it operates. You wouldn't want
the rudder to hinder the water-stream before the hull gets a
chance to move through it!
--
Howard Coakley
e-mail... howarddot}coakleyatcoakleydot].codotuk
ICQ:4502837. (Try ICQ at www.icq.com)

"Howie" wrote in message
...
On Mon, 10 May 2004 10:48:22 GMT, "Martin Underwood"
wrote:

|This is probably an incredibly naive question, and I apologise if it's a
|FAQ, but it's one of those things that I was pondering on in an idle
moment.
|
|Why is it that on all boats, the rudder is at the back rather than the
front
|of the boat? Is it:
|
|- because a rudder at the front simply wouldn't work properly to steer
the
|boat?
|
|- because a rudder at the back gives greater manoeuvrability, in the same
|way that dumper trucks on building sites have rear-wheel steering whereas
|cars and lorries have front-wheel steering?

It's to do with displacement. A displacement hull is designed to
'fend off' water whilst travelling forwards.
A rudder at the front would stop the displacement hull working
effeciently unless you are travelling in a straight line. So - it
slows the boat down.

Also, Because the boat is designed to go at maximum speed when
going forwards, the water stream passing under and around the
boat is much more stable and reliable as a medium than the water
you have not yet hit! Effectively, the water speed and direction
helps the rudder to do it's job. A rudder hinders the effeciency
of this water stream, this is how it operates. You wouldn't want
the rudder to hinder the water-stream before the hull gets a
chance to move through it!

So there are good technical reasons for having the rudder at the back - as I
suspected, but I wondered whether was an element of "we've always done it
this way". I dare say they tried the rudder at the front in early boat
designs and found that it didn't work as well.

Martin Underwood wrote:

So there are good technical reasons for having the rudder at the back - as I
suspected, but I wondered whether was an element of "we've always done it
this way". I dare say they tried the rudder at the front in early boat
designs and found that it didn't work as well.

Kayakers and canoeists (usually without mounted rudders) will use either
bow or stern rudder strokes according to what works best in that
particular spot. Keeping on line surfing will generally be at the
stern, breaking out (or in) at an eddie will be bow. But ruddered boats
tend to work in more predictable water than places where paddlers will
use ruddering strokes.

Pete.
--
Peter Clinch University of Dundee
Tel 44 1382 660111 ext. 33637 Medical Physics, Ninewells Hospital
Fax 44 1382 640177 Dundee DD1 9SY Scotland UK
net http://www.dundee.ac.uk/~pjclinch/

"Martin Underwood" wrote in message ws.com...
Why is it that on all boats, the rudder is at the back rather than the front
of the boat? Is it ... because a rudder at the front simply wouldn't work
properly to steer the boat?

A rudder pretty much has to be at the back (behind the centre of
mass/rotation) to work. When aligned with the direction of travel, a
rudder acts like a fin (as with a rocket's tail fins or surf board
fins) and works to keep itself at the rear, thus the craft straight.
If you put it at the front would try to flip the craft around to be at
the back.

A small temporary rudder up front is great for making quick turns (as
used in a kayak or canoe), but a liability at all other times.

"Howie" wrote in message
...
On Mon, 10 May 2004 10:48:22 GMT, "Martin Underwood"
wrote:

|This is probably an incredibly naive question, and I apologise if it's a
|FAQ, but it's one of those things that I was pondering on in an idle
moment.
|
|Why is it that on all boats, the rudder is at the back rather than the
front
|of the boat? Is it:
|
|- because a rudder at the front simply wouldn't work properly to steer
the
|boat?
|
|- because a rudder at the back gives greater manoeuvrability, in the same
|way that dumper trucks on building sites have rear-wheel steering whereas
|cars and lorries have front-wheel steering?

It's to do with displacement. A displacement hull is designed to
'fend off' water whilst travelling forwards.
A rudder at the front would stop the displacement hull working
effeciently unless you are travelling in a straight line. So - it
slows the boat down.

Also, Because the boat is designed to go at maximum speed when
going forwards, the water stream passing under and around the
boat is much more stable and reliable as a medium than the water
you have not yet hit! Effectively, the water speed and direction
helps the rudder to do it's job. A rudder hinders the effeciency
of this water stream, this is how it operates. You wouldn't want
the rudder to hinder the water-stream before the hull gets a
chance to move through it!

Sounds intelligent enough and believable, but then explain canard wings on
aircraft...? That's basically a rudder in front.

I also think this question could be given a lot of insight by some sweep
boaters; they have rudders/oars at both ends, and those guys are well
acquianted with steering with one or the other against the current
differential. Any sweep-oarsmen out there?

--riverman

--riverman

"riverman" wrote in message ...
"Howie" wrote in message
...
On Mon, 10 May 2004 10:48:22 GMT, "Martin Underwood"
wrote:

|This is probably an incredibly naive question, and I apologise if it's a
|FAQ, but it's one of those things that I was pondering on in an idle
moment.
|
|Why is it that on all boats, the rudder is at the back rather than the
front
|of the boat? Is it:
|
|- because a rudder at the front simply wouldn't work properly to steer
the
|boat?
|
|- because a rudder at the back gives greater manoeuvrability, in the same
|way that dumper trucks on building sites have rear-wheel steering whereas
|cars and lorries have front-wheel steering?

It's to do with displacement. A displacement hull is designed to
'fend off' water whilst travelling forwards.
A rudder at the front would stop the displacement hull working
effeciently unless you are travelling in a straight line. So - it
slows the boat down.

Also, Because the boat is designed to go at maximum speed when
going forwards, the water stream passing under and around the
boat is much more stable and reliable as a medium than the water
you have not yet hit! Effectively, the water speed and direction
helps the rudder to do it's job. A rudder hinders the effeciency
of this water stream, this is how it operates. You wouldn't want
the rudder to hinder the water-stream before the hull gets a
chance to move through it!

Sounds intelligent enough and believable, but then explain canard wings on
aircraft...? That's basically a rudder in front.

I also think this question could be given a lot of insight by some sweep
boaters; they have rudders/oars at both ends, and those guys are well
acquianted with steering with one or the other against the current
differential. Any sweep-oarsmen out there?

--riverman

--riverman

A canard true enough is a rudder. It can turn a plane so fast as to
have it lose directional stability and in modern fighters could tear
itself apart.
At speed the canard on aircraft is controled entierly by computer.
This as opposed to the Cesna a friend let me fly . Rudder in the rear
but like the kayak the rudder was not used as much as I thought it
would be.
Control was manual and easily mastered my a relative beginner.

The Front sweep is a low speed maneuver relative to the speed of the
boat in the water. A raft flying down a river often has zero speed
relative to the water.

The rudder in the stern redirects a moving boat in the most
controlable and predictable fashion .
A front cross bow rudder in a sea kayak is a fun way to put a crowd of
beginners into the water.
Control is smooth, simple , reliable and more efficient with the
rudder at the rear of the boat.
Now boat lean and progressive sweep strokes with no rudder is much
more efficient and looses little if any speed when compared to the
drag of a rudder.

Who thought such a basic question would make us think?

In article m,
Martin Underwood wrote:
This is probably an incredibly naive question, and I apologise if it's a
FAQ, but it's one of those things that I was pondering on in an idle
moment.

Why is it that on all boats, the rudder is at the back rather than the
front of the boat? Is it:

- because a rudder at the front simply wouldn't work properly to steer the
boat?

- because a rudder at the back gives greater manoeuvrability, in the same
way that dumper trucks on building sites have rear-wheel steering whereas
cars and lorries have front-wheel steering?

Your last point first: cars and boats/planes operate differently. There is
no dynamic lift or disturbance of laminar flow to account for when steering a
motor vehicle...

Whilst travelling forwards, the centre of lateral resistance of a pure hull
without fin or rudder will be well forwards of the mid-length, its location
determined to large degree by such things as distribution of drag/unit area
along the hull surface (which falls quasi-exponentially from bow to stern).
A conventionally-placed rudder will then much reduce or eliminate the
tendency of the stern to swing sideways.

You can determine the approximate centre of lateral resistance by applying
the hanging bow rudder (or hanging draw) strokes. The bow rudders will
require considerably more resistive force than equivalent stern rudder
strokes. At certain speeds it is necessary to move the blade further
forwards in order to attain a reasonable turning effect.

The main reason for not having a rudder (or a fin) at the bow end is because
it disrupts the efficient run of the boat, and will not, generally be able to
turn the vessel about the CoLR. A stern-mounted or under-stern rudder will
be able to do this.


Allan Bennett
Not a fan of circular reasoning

--

In article , riverman
wrote:

"Howie" wrote in message
...
On Mon, 10 May 2004 10:48:22 GMT, "Martin Underwood"
wrote:

|This is probably an incredibly naive question, and I apologise if it's a
|FAQ, but it's one of those things that I was pondering on in an idle
moment.
| |Why is it that on all boats, the rudder is at the back rather than the
front
|of the boat? Is it: | |- because a rudder at the front simply wouldn't
work properly to steer
the
|boat? | |- because a rudder at the back gives greater manoeuvrability,
in the same |way that dumper trucks on building sites have rear-wheel
steering whereas |cars and lorries have front-wheel steering?

It's to do with displacement. A displacement hull is designed to 'fend
off' water whilst travelling forwards. A rudder at the front would stop
the displacement hull working effeciently unless you are travelling in a
straight line. So - it slows the boat down.

Also, Because the boat is designed to go at maximum speed when going
forwards, the water stream passing under and around the boat is much more
stable and reliable as a medium than the water you have not yet hit!
Effectively, the water speed and direction helps the rudder to do it's
job. A rudder hinders the effeciency of this water stream, this is how it
operates. You wouldn't want the rudder to hinder the water-stream before
the hull gets a chance to move through it!

Sounds intelligent enough and believable, but then explain canard wings on
aircraft...? That's basically a rudder in front.

I also think this question could be given a lot of insight by some sweep
boaters; they have rudders/oars at both ends, and those guys are well
acquianted with steering with one or the other against the current
differential. Any sweep-oarsmen out there?

Rowers don't have bow-mounted rudders or fins. One guy has mounted a fin to
the front of his scull, but has not convinced others so to do.


Allan Bennett
Not a fan of numbskullers

--