Bow Rudder Possible?

[Wynand N]

Would a bow fitted rudder be feasible or do we just take an aft mounted rudder as granted

Some aeroplanes have rear mounted propellors (pushers) and fly just aswell and in some cases better than a conventional layout.

Same with cars engines. Some front, mid and rear mounted. Who is wrong, Porsche or all the other manufactures? Then again, can anything touch a Porsche

Please, do not crucify me, just some thoughts though.

Wynand Nortje

[redcoopers]

It's a question of stability.

IACC rules allow for the possibility of different configurations, and they have been tried.

For an airplane as well as a sailboat, one problem is balance. In a plane, the moments from CG and CL need to equate as well as satisfy some degree of stability so that the pilot can concentrate on other things. In a sailboat, the CL from the sails needs to balance the CL from the hull. Typically, a platform is more stable when your control surface is to the rear.

It can be done for a sailboat - but this is usually a fore rudder in tandom with an aft rudder. The reason it's not done is usually for practical reasons including 1) you need long linkages between the helm and the rudder 2) because you can't see every rock underwater, I'd rather hit it first with my keel vice my control surface 3) when manuevering into a slip, I can use the prop to put velocity over my rudder thereby increasing my turn.

So anyway, the answer is sure. By the way, the Minis in the 1960s Monte Carlo rallys showed that a front engine transverse layout was superior to Porches... Paddy Hopkirk rules!
-Jon

[B. Hamm]

It's a bit different in an aircraft than a boat, the problem with an aircraft is the stern rudder adds load to the wing actually pulling the tail down, the CG is forward on purpose. In a stall the main wing will then always stall first. With a canard (forward rudder) the canard carries a percentage of lift adding to the lift, something the rear rudder can't do. But the canard has to stall first, so it has to have more positive incidence than the main wing. If the main wing were to stall first in this instance, the plane would fall completely out of control, bad thing.

On a boat, if the bow rudder stalls first you at worst might broach, a bit less dangerous, though it's something to consider.

No reason it can't work on a boat, though unless the cockpit were in the bow the linkages would be at minimum interesting

Bill H.

[Wynand N]

Hi. B Hamm,

No reason it can't work on a boat, though unless the cockpit were in the bow the linkages would be at minimum interesting

I am going to be devils advocate and ask; why don't we have forward cockpits.
Except for the occasional drowing by waves imagine how easy you can navigate your boat into tight spaces, see reefs before you hit them for starters.

Wynand

[PAR]

Forward rudders have been used and designed by the greats. Used in light air for lee helm correction or hove to in a slosh. It also has good steadying properties in a seaway and the advantages in tacking quicker and without as much loss of way are reasonably clear. Herreshoff did some on narrow river barges or scows, I think, with the ability to swing 360 degrees, allowing them to slide sideways into or out of a spot, even working a flow or ebb to advantage. Pretty sweet making a contrary current work for you.

That said, they are about as practical as antlers on a Great Dane. They'd be out of order pretty quick with reasonable usage, snagging every sliver of plastic bag and weed you could find. Just what every sailor wants, not being able to claw off a rocky lee shore because a six pack ring thingie jamming the forward rudder . . .

Wynand N., there are forward cockpits too. The have decided advantages for certain efforts needing be preformed afloat. They are typically work craft and a dodger, dog house or small pilot house installed for obvious reasons. The classic (at least in this country) bow rider with the walk through windscreen certainly qualifies as a forward cockpit. Some of the saltiest craft I've seen are cold water fishing boats with large open aft area for the crew to work the gear and catch plus the small sometimes off center dog house to keep the pilot dry.

Again, Wynand, Your material is still in route, I called them yesterday and they said it was on the loading dock (whatever that meant) I'll call them Monday and light a fire under their butt, before the holiday rush gives them too good an excuse. You'd think South Africa, a strong, modern country would have a better mail delivery system. Keep in touch . . .

[SailDesign]

Bow rudders or foils on any boat that may ever pound are a structural nightmare just waiting for you to fall asleep Think about it...

[JEM]

This is a neat "what if" idea.

Trolling motors are mounted on bows of boats. Although a rudder is different in that it requires water to flow past it in order for it to work.

If you're using a bow rudder to supplement the aft rudder, it might make for some very responsive steering. A bow rudder would have to go in the opposite direction of the stern rudder and probably best to be a much smaller foil than the stern rudder.

As stated, lots of rigging. It, however, would be a fun and somewhat inexpensive experiment to conduct on a smaller craft.

But a bow rudder as a substitute for a stern rudder, I'm thinking no way.

[tspeer]

Using aircraft as the analogy, all the studies that have looked at the relative efficiency of canard vs tandem wing vs aft tail configurations have found the aft tail is more efficient.

Here's one example (from http://aero.stanford.edu/Reports/MultOp/multop.html)


The trim situation for a keel and rudder are different from an airplane becaue the centers of effort are arranged to produce weather helm, whereas most aircraft with an aft tail are balanced to produce the equivalent of lee helm. So these results have to be applied with caution to boats.

When I was a lad, I remember getting into disagreements with my brother as to which way our canoe was to go. However, there was no disputing whether the bow or the stern end was more effective in controlling the boat...

[B. Hamm]

There are advantages and disadvantages in any change to a design, there will be quite a few things to consider using a bow rudder/bow cockpit, none I suspect that can't be overcome though. Boat design is basically evolutionary, perhaps this is an idea that's time has come?

Bill H.

[SailDesign]

Originally Posted by B Hamm

Boat design is basically evolutionary, perhaps this is an idea that's time has come?

Here's a mental image for you. You rbow-ruddered boat is in heavy seas, heeling considerably. You exit one wave with a little more speed than usual, or perhaps it's just a steeper wave than usual, and your whole bow emerges from the water, ready to smack down into the next wave. What hits first? Can you engineer a rudder to take this kind of abuse, while still keeping excess weight out of the ends? Have you ever seen a boat do this to it's stern-mounted rudder?

Steve

[tom28571]

To be most effective, a rudder needs to be well away from the center of lateral resistance (keel), so the rudder should be at one end of the boat or the other. For best control, the rudder should always be immersed in the water.

Which end of the boat best fits these requirements?

No contest.

[B. Hamm]

Hi Steve,

Not every boat is designed for the open ocean. The odds of this happening in more protected waters is remote at best.

Bill H.

[B. Hamm]

Again, you're only considering open ocean use. Heck some workboats on the inland waters of this country have as many as 8 rudders in various locations on the boat, though usually not in the bow.

Bill H.

Even the much-derided IOR actually had at least one cockpit-first boat; a Brit Chance 1/4 tonner (Honky Tonk Woman???).

But for small boats there are problems. If you have say a 15' performance dinghy weighing 200 lb, you have to support a crew weight of about 330 lb. If you have to float that much in the bow, you'll have to have incredibly full, bouyant sections and therefore the boat will absolutely bark upwind. Downwind it will also be impossible to handle because it will nosedive and you'll never be able to get the bow up to reduce wsa.

Even for say a 24 footer, the weight of four people in the bow would be a major problem. Most boats pitch around 2/3 of the way aft, which puts the crew around the centre of pitch so they have the minimum slowing effect. A boat with the crew right forward would bounce terribly even in a harbour chop. Again, most boats tend to sail bow-down when running at speed so what could you do if you couldn't get weight aft?

Canard centreboards were tried in 18' skiffs in the '70s and '80s. As mentioned, the bow was a terrible place to put extra weight. And in many areas, even inshore a boat will get its bow out and slamming in harbour chop or even powerboat wash, bringing all the structural problems already mentioned.

Fun ideas, but.......

Canting Ballast Twin Foil boats such as the two 86'maxZ86's, Genuine Risk, the Schock 40, and soon on the 115'Maiden Hong Hong plus numerous cruising or semi cruising designs have proven the viability(and speed) of a forward rudder combined with an aft rudder. The forward rudder is about 25% of the LWL aft of the bow and the aft rudder a little more than 75% aft of the bow.
Using two foils in this way allows both normal steering and "collective" steering where both foils turn a little in the same direction virtually eliminating leeway.
In this case the twin foils also provide all the lateral resistance since the keel strut provides none at all....