MODIFICATION ON A RUDDER FOR BOATS AND SHIPS

Abstract: A modification on a rudder for boats and ships, comprising a channel disposed rearward of the screw which is rotatable about a substantially vertical axis. The channel has a closed, circular cross-sectional configuration. Two V-shaped notches are provided in the rearward end of the tunnel, the V-tips lying in the central vertical plane through the tunnel, such that on each side of this plane, a curved tongue (17) is formed. In one embodiment, the channel can be arranged in connection with a conventional plateshaped rudder (9), one halfsection of the channel being arranged on each side of the rudder.

Description: Modification on a rudder for boats and shins The present invention relates to a modification on a rudder for boats and ships, comprising plates disposed on both sides of the rudder and parallel with the rudder surfaces. Many boats have poor steering capabilities, especially at slow speeds. This is particularly true for small boats, such as the Norwegian "snekke" (a 16- to 24-foot open fishing boat, pointed at both ends, most often clinker-built), and for other types of boats having a relatively deep bottom, a long keel and driven by an inboard motor, where the propeller turns about the same axis at all times and thus cannot participate in the steering. Such boats have especially poor steering capabilities when reversing. In fact, some boats do not answer the helm at all when reversing at slow speeds. Some other boats can answer the helm when reversing by turning only in the one direction. It is obvious that this deficiency presents great problems in situations in which precise manoevering is required, for example, when sailing out of or into a harbor or in other situations where it is necessary to steer the craft while reversing. The problems with such boats can be so great that the owner of the boat simply ^ r:no-. risk taking his boat out of harbor if the winds and sea are blowing toward land. The effect of a boat rudder is to deflect the flow of water relative to the longitudinal direction of the boat, whether this flow results from the speed of-the boat or from water which has been set in motion by the screw. The propeller " flow, however, is far from laminar, and it therefore has a relatively bad effect on the steering of the boat. Therefore", a boat traveling at slow speed will have poorer steering than the same boat traveling at higher speeds. In some cases, the screw will reduce the steering properties of the boat. This is particularly true when reversing, because the laminar flow of water which moves along the hull of the boat will be broken up by the propeller, which has poor screw properties when reversing, the blades of a propeller being constructed first and foremost with forward propulsion in mind. On boats which have poor steering capabilities in reverse, there¬ for " -., one must often set the boat in motion backwards and then cut out the propeller before the rudder will have any steering effect. OMPI - Several different types of aids have been tried in attempts to improve the steering properties of boats of the above type. Thus, various types of guide plates on both sides of the rudder surface have been tried. A modification on a rudder is known from Norwegian Patent 59,795, in which plates that are parallel with the rudd surface are provided on each side of the rudder, the leading edge of the plates projecting forward of the middle leading ed of the rudder. The primary object of this modification is to balance the rudder, in that one thereby obtains steering surfa which lie in front of the rudder shaft. A similar modificatio is known from US Patent 3,181,492. It is known from US Patent 2,328,0 1 to mount arch- shaped guide wings on both sides of a conventional plate rudde in such a manner that the guide wings are disposed radially exterior of the propeller when the rudder is in the neutral position. However, the modifications of this type known hithert have not had the desired effect, and at present no.effective a exists for increasing or improving the steering capabilities, especially when reversing, on boats of the type defined above. The object of the present invention is to provide a modification on a rudder for boats and ships which comprises plates disposed on both sides of the rudder and parallel with the rudder surfaces, which improves the steering properties of the boat both when reversing and during forward propulsion. This is obtained according to the invention by means of a modification on a rudder for boats and ships which compri a channel or tunnel, disposed rearward of the screw, which is rotatable about an axis substantially parallel to the rudder a and its characterizing features are that the channel has a clos circular cross-sectional configuration, and that at the rearwa end of the channel two V-shaped notches are provided, the tips of the V's lying in the central vertical plane through the cha such that on each side of this plane, an arch-shaped tongue is formed. _ OA1PI Numerous trials have shown that this configuration of a channel-shaped rudder provides quite superior steering proper¬ ties, especially when reversing. This is very important, as reversing. with boats having a pointed bottom configuration, such as the Norwegian "snekke" fishing boat, has always been problem¬ atic. With a rudder having the configuration defined above, such a boat will answer the helm equally well in both directions, while it would normally answer the helm only in the direction of rotation for the propeller. The steering properties of the boat will also be improved in the forward direction, especially when moving forward at very slow speeds. A practical embodiment of the invention is character¬ ized in that the tongues constitute approximately one-half of the total length of the channel in the longitudinal direction of the boat. A special embodiment of the invention is characterized in that the channel is arranged in connection with a plate-type rudder, the channel being arranged symmetrically on both sides of the rudder plate. Such an arrangement will be practical for a boat which is equipped with a conventional plate rudder, as it permits one to attach a half-section of the channel on each side of the rudder. The invention will be elucidated further in the following with reference to the accompanying drawings, which illustrate two different embodiments of the invention. Figure 1 shows a first embodiment of a rudder according to the invention, mounted on a small boat, in perspective, and Figure 2 shows the same embodiment seen directly from above. Figure 3 shows a second embodiment of the rudder accord¬ ing to the invention, in perspective, and Figures 4 and show the embodiment of Figure 3 seen straight from the back and directly from above, respectively. In accordance with the embodiment illustrated in Figure I, a circular, channel-snapped rudder 1 is provided between the stern 2 of the boat and a lower rudder support 3 * The rearwardly- projecting support 3 s the most common construction on small boats, but one also finds types of boats in which this support is not present, in which case the rudder is supported solely b the rudder post - The boat illustrated in this example is driven by a three-blade screw with reversible directions of rotation. The rudder shaft is attached to the channel 1 forward of the middle of the total length L of the channel. Two V-shaped notches have been cut into the tunnel at its rear ward end, the tip of each V lying in the central vertical plan through the channel 1. In this manner, respective arch-shaped tongues 7 > 8 are formed on each side of said plane, the total length a of the tongues in the longitudinal direction of the channel being approximately equal to one-half the total length of the channel. Figure 3 shows an embodiment which is well.suited for rebuilding the rudder of a boat which is already equipped with a conventional plate rudder 9 > placed between the stern 2 of t boat and the lower support 3« T n this example, also, the boat is driven by a three-blade screw 5 with reversible directions rotation. The rudder is rotated by means of a rudder shaft 4 » which is placed a distance behind the leading edge of the rudd plate i n order to obtain a certain balancing effect. Attach to both flat sides of the rudder 9 are arched guide plates 11 and 12. The curvature of the plates is in accordance with a circular line in the crosswise direction of the boat, such that the two plates 11,12 together form a circular-shaped channel. The lateral marginal edges -13 of the plates 11,12 (Figure ) ar parallel with one another and with the rudder surface on the plate rudder 9» The plates 11 and 12 are attached at their upp and lower edges 14 and 1 to the respective upper and lower edg of the rudder surface. The forward edge 16 on the plates 11,12 is disposed somewhat astern of the rudder shaft * . The plates 12 have a curved rearward edge 16, such that the outer- marginal edges 13 of the plate project somewhat astern of the plate part which are attached to the rudder at 14 and 1 . In this way, "on c υes or overhangs 17 are formed. The diameter of the channel which is formed by the two plates 11 and 12 is larger than the screw diameter of the ( - °M ~ propeller « ^ n regard to the dimensions of the plates 11 and 12, the length a of the overhang 17 is approximately equal to the remaining length b of the total length L (see Figure ) > i.e., the length a of the overhang 17 is approximately equal to one-half of the total length of the plates 11 or 12. The ratio of the length L (= a + b) to the diameter lies between 3:4 and 3:6. A rudder modification in accordance with the exemplified embodiments was tested on a small fishing boat which had extremely poor steering properties, especially when reversing. At slow speeds, this "snekke" boat did not answer the helm at all in one direction during a reversing operation. The boat's berth was situated such that the sea and wind often blew toward land, and it often happened that the owner could not take his boat out for the sole reason that it was not sufficiently manoeverable, as it was impossible to steer the boat in reverse. After the modification according to the invention was installed, the owner claimed that the boat was as easy to steer as an automobile, and that it answered the helm when driven in reverse both at slow speeds and at full speed. In addition, the turn radius during forward propulsion had also become substantially smaller. Another effect of the modification according to the invention is that it also prevents or greatly reduces the downward drag on the stern end of boats of this type. This is a common phenomenon, and it reduces speed or increases fuel consumption rather significantly. In order to prevent this, some boats have a hull built with an expensive support plane or support fins in the region of the screw. Such hull modifications can be rendered unnecessary with the use of the invention, and the price of the hull correspondingly reduced.

Claims: Patent_Glaims 1. A modification on a rudder for boats and ships, com¬ prising a channel, disposed rearward of the screw, which is rotatable about a substantially vertical axis, characterized that the channel has a closed, circular cross-sectional confi uration, and in that two V-shaped notches are provided in the rearward end of the tunnel, the V-tips lying in the central vertical plane through the channel, such that on each side of said plane an arched tongue (17) is formed. 2. A rudder modification according to claim 1, characte ized in that the tongues (17) constitute approximately one-ha of the total length L of the channel in the longitudinal dire 3. A rudder modification according to claims 1 or 2, characterized in that the ratio of the total length L of the channel to the diameter of the channel lies between.3^4 and 3 4. A rudder modification according to one or more of th preceding claims, characterized in that the channel is arrang in connection with a conventional plate-shaped rudder, one-ha of the channel being arranged on each side of the rudder plat OM

Inventors: BRAA O
Applicants: BRAA O
Application year: 1980
Main classification: B63H25
IPC codes: B63H5, B63H25