GB2530550A - Improvements to boats when slamming - Google Patents

Abstract

A boat comprising a hull having flaps 2 pivotally mounted on its base, wherein the flaps can move between a streamlined position under normal cruising conditions and a position in which their movement is constrained such that when the boat slams they produce a forward thrust on the hull. The pivots 3 are preferably set normal to the hull. The constraining angle of the flaps can preferably be adjusted for different conditions from both inside and outside the hull. The flaps may be spring loaded.

Description

Patent Application: Improvement to Motor Boats when slamming.

This patent relates in particular but not exclusively to fast motorboats.

In wavy conditions of heavy swell or chop, last motorboats travelling over the crest of a wave the hull initially rises and after traveling over the crest drops heavily and makes contact with the downward slope of the wave. This is commonly known as TMslammlng" and is uncomfortable for the occupants of the boat and heavily loads the structure of the craft. On slamming, the boat also experiences a deceleration as the bow noses into the water causing further discomfort and stress to the hull.

this invention improves the slamming phenomenon by reducing the deceleration and can actually achieve acceleration during the slam alleviating discomfort and reducing hull loads.

Using the same principals of this invention improvement in the performance of a boat can be achieved in normal running conditions by harnessing the energy of the bow waves into useful forward thrust.

Description:

Figure 1 shows one embodiment of the invention by way of an example only where the view is an underside ala typical speed boat which has a deep-V entry, turning into a relatively shallow V at the stern common to the art. The hull 1 has elements 2, hereInafter called flaps placed along or near the chines or in between the strakes or a position found most beneficial. The flaps are pivotally mounted on pivots 3 shown also in Figure 2. The pivots are set normal to the hull surface and in a position towards the front of the flaps so that the flaps freely pivot to take up the angle of the water flow in a streamline.

In figure 2 SectIon A A' a side view of the pivot 2 in this embodiment are attached to plate 4 which is attached to the hull baseS of the boat with screws.

bolts or glue or mounted directly to the hull following the principles herein.

In normal running conditions, these freely pivoted flaps would settle at a water flow direction approximately longitudinal to the hull, wIth a slight outward angle as the hull parts the water throwing it with a sideways component On slamming the water flow would have a sudden greater angle from the centerline of the boat there being a large outward component olthe water flow. It is at the greater outward component of water flow, that the flaps would be constrained to pivot less than the outward component of the water, thereby their reaction giving the boat substantial forward thrust dependent on the chosen angle of constraint and the size and shape of the flap coupled with the angle of slam flow which produces an angle of attack on the flap.

Figure 2 shows ip Position (a) and Position (b one embodiment by way of example only a way of constraining the flap. Position (a) the flap Is in a normal running state and Position (I,) its position alter the slam. Flap 2 has lug 6 (Section A N) which nestles in slot 7 in the mounting plate 4 which allows flap to pivot until it reaches end of slot at 8. This constraint allows the flap to produce the forward thrust from the slam.

Figure 3 shows at (c) the direction atwater flow 9 during a slain and angle or flap 2 In its constrained position thereby producing vector 10 with a forward thrust component vector 11 created by the angle of attack of flow 9 on flap 2. This illustrates the basic principle of the invention.

A more detailed analysis is shown In Figure 3 at (d) where vector B Is the slam resultant of lilt vector Land drag vector D of the flap, here drawn with Lift to Drag ratio of 124 The forward component of thrust Is vector T which drives the boat forward.

A further embodiment of the invention is that the flaps are spring loaded to increase their resistance to rotate giving a incremental forward reaction rather than the sudden force on hitting the stop. The flap would then return aided by its spring to its initial position creating extra thrust by virtue of its stored energy which would be dependent of the stiffness of the spring. Furthermore this also produces a forward thrust at lesser Intensity of slam in the case where the stop position Is not reached. By not having a spring loaded flap or soft' stop to the slot could be damaging to the system.

Figure 4 shows two methods of springing, by way of example only, where spring 12 Position(a) and Position (b) gives lateral resistance to the flap creating a forward thrust at lesser angles than the flap hitting the stop. The springing can be done in various ways known to the art such as coil or rubber or as a concentric coil spring 13 fixed to flap 2 at one end and base 4 at the other as shown around the pivot post 3.

A further embodiment of the invention has flaps set on the hull at or near the bow wave at such an angle to increase the net forward thrust to the hull by harnessing the momentum of the bow wave.

This is shown in figureS where hull 14 has flap 15 rigidly mounted to the hull at an angle such that the bow wave spray 16 produces vector lift L on the flap which has a vector thrust T in the direction of travel.

In further embodiments of bow flaps the set angle of the flap can be trimmed for maximum forward thrust and it's position altered upwardly or longitudinally inside the boat and also the number of flaps can be increased. It should be noted that the lift L produces a beneficial effect on hull drag.

In further embodiments of the invention: A boat where 1-the length and depth and thickness and profile of the flaps on the base of a hull can be altered to suit the characteristic desired.

2-the size and shape and number of flaps can vary at different positions of the hull.

3-the angle of constraint can vary with respect to their position on the hull.

4-the angle of constraint can be altered both from the underside of the hull or from inside the hull whilst underway.

the flaps are sprung to produce forward thrust at lesser intensity of slam, 6-flaps which can be adjustable from outside the hull or inside the hull and trimmed from the helm.

8-flaps that can be retracted into the hull to maintain an orthodox hull surface *

Claims (1)

1. CLAIMSWhat I claim is: 1-pivotally mounted flaps on the base of the hull of a boat, which are free to pivot In such a way that their angle streamlines with the water flow over them under normal cruising conditions but their movement is constrained such that when the boat slams, they produce a forward thrust on the hull.

   2-pivotaily mounted flaps on the base of a boat, where their angle of constraint and shape and number can vary with their position on the hull4 3-the constraining angles of pivotally mounted flaps on the base of a hull can be adjusted for different conditions from both outside and inside the hull.4-plvotally mounted flaps on the base of a hull where the flaps are spring loaded to produce a forward thrust at lesser angles than the constrained flaps as In Claim 1.S -bow mounted flaps which produce a forward or forward and upward thrust to a boat created from the boat's how waves.6-the bow flaps in ClaimS can be adjusted and trimmed from inside the boat.