What is a stern-mounted rudder?

[longshore lubber]

Hello,

I need help on definition and terminology. What is a stern-mounted rudder and in what way does it differ from a so-called stern-mounted steering oar? Do English speakers realize that other languages such as French and German have only a single word for these two types? The medieval pintle & gudgeon rudder has been described as "median, vertical and axial". What do these terms mean actually?

Here are three different sets of steering gear mounted on the stern. In what way do they differ? Can they all be subsumed under the generic term "stern-mounted rudders"?

http://commons.wikimedia.org/wiki/Image:Maler_der_Grabkammer_des_Menna_013.jpg?usela ng=de

http://commons.wikimedia.org/wiki/Image:Rudder_of_a_Roman_Boat_(RG_Museum_Koeln%2C_G ermany).JPG?uselang=de

http://commons.wikimedia.org/wiki/Image:Pintle_and_gudgeon_rudder_system_scheme.svg? uselang=de

[Ian McColgin]

A steering oar is still an oar, blade symetrical or nearly so around it's shaft. It may be mounted near the stern over one side, normally starboard (hence the name deriving from 'stear-board') or right off the horn, as in the second picture.

The third pic shows the essence of a rudder. However hung, it pivots on a fixed axis supported by two or more hinges, typically the depicted pintles and gudgeons though a spade rudder is hung on it's own shaft that's supported by a tube through the boat. Some rudders have a bit of lead, but most have the pivot point at the leading edge.

All rudders are at or near the stern, though you may see some spade rudders and even a few on a keel's trailing edge that are as much as 1/3 of the way from the aft most part of the boat. THis is especially true of boats with long overhangs.

In English there's a specific term "transom hung" rudder for a rudder that's affixed to the transom above the waterline and carries on down along the deadwood (back end of the keel).

G'luck

[Thorne]

As you may know, absolutely no word or phrase in English has an absolute single-definition meaning -- there is a certain amount of fuzziness on inexactitude in all language elements.

Outside of governmental agencies producing reams of paper defining things, few words can be clearly quantified when used in "real life".

Terms from the past, particularly those for nautical concepts, have an even greater amount of generality, depending on how you try to define the usage. Try to absolutely define "ship", "skiff" or "dory" for example...

That given, I'd say that anything attached to the aft stem or transom by pintles and gudgeons qualifies as a "rudder", and foils attached to the top of the aft stem or railing, usually with a long spar/handle continuing in the same plane as the foil would qualify as a "steering oar".

[outofthenorm]

The three images all show stern mounted steering gear or systems, but not all three are IMO rudders. The third image is a typical "modern" - as opposed to "ancient" rudder. It's mounted on a set of pintles passing through gudgeons and its turning axis is almost, but not quite vertical. The key difference between it and the first two is that the axis of rotation for the "shaft" of the third one passes through multiple points, which must be perfectly in line for the system to work properly.

In the first 2 systems, the rotation axis is multi-directional - more in the nature of a pivot than a hinge. In the Roman example, it appears that lines or supports have been rigged to limit the range of movement. The blade is "balanced" meaning there is equal area (more or less) on either side of the shaft - in fact, it looks more like an oar than a rudder. Compensating for that, it is crossed by a tiller that the helmsman is using to control rotation. To me, that makes it a rudder, rather than a steering oar. The Egyptian example is definitely a steering oar, not a rudder.

It is unusual (even for the period) for a steering oar to be mounted on the extreme stern as this one seems to be. Steering oars are usually seen mounted on the quarters. The Egyptian helmsman has his arm wrapped around the shaft and is using body lean to shift the oar in the water. It appears that he's also holding onto a line of some sort - maybe a relieving line to take some of the load.

- Norm

[outofthenorm]

PS - if you're studying this Lubber, don't overlook the "Yuloh" - a steering varient that is a lot like the Roman example, but with some very oar-like characteristics.

http://www.simplicityboats.com/1Scullings.jpg

[Kaa]

The Yuloh is not for steering -- it's for propulsion.

Kaa

[Thorne]

Like regular oars, the Yuloh can be used for both but is primarily for propulsion.

I think Norm has it figured out, it's the axis of rotation -- which takes into account pipe rudders and the like that are not mounted on pintles/gudgeons...

Bob S's Gunning dory rudder -
http://pic3.picturetrail.com/VOL12/1104763/7711190/101677609.jpg

[Canoeyawl]

There are "inboard" rudders like Bob's shown above.
This would not qualify in my book as a "stern mounted" rudder.

[longshore lubber]

Thanks for your views so far. Keep them coming. :-) I am going to add later some more interesting pics of ancient stern mounted steering gear which are again different from the above.

A steering oar is still an oar, blade symetrical or nearly so around it's shaft.

Alright. But why then is a steering oar mounted on the side of the ship, so readily called in English a quarter rudder? Since quarter rudders have a very similar shape to steering oars mounted on the stern, it makes no sense to change the whole term, only because the steering oar changes its mounting place on the ship, doesnt it? The terminology seems inconsistent.

[outofthenorm]

As said earlier, I believe that the difference isn't in the shape of the blade, but in the nature of the rotational arrangement. A rudder is axial, a steering oar isn't. Hence an oar, mounted axially on the quarter could be deemed a rudder, despite it's original purpose as an oar. But to me, the real "turning point" (forgive the pun) is when the steering shaft is fitted with a tiller of some sort. Tillers only work on a system that rotates axially (if there is such a word), and that makes it a rudder IMO.

BTW, the reason I mentioned the Yuloh eairlier is that is is somewhere in the middle. It often has a tiller-ish sort of cross-stick attached that is used to twist it about, but we would never call it a rudder. If you hoisted a sail or were being towed, it becomes a steering device, on it's own it provides both steering and propulsion, same as an outboard.

Take note that there are two concepts included in your question: one is "Is it a steering oar or a rudder", the other is about the mounting position - what is meant by "stern mounted". The first is about the nature of the mounting. The latter term is about the position of the mounting.

The position of the device isn't a clear indication of its definition as either an oar or a rudder. Both systems could be used astern, on the quarter, or underslung like the photo posted above - although that would be unlikely with an oar. Possible, but unlikely.

- Norm