Ships – Anchor – Sea anchor
Patent
1989-08-17
1991-05-21
Swinehart, Ed
Ships
Anchor
Sea anchor
114294, B63B 2148
Patent
active
050165569
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a drogue or sea anchor.
It is known from International Publication No. WO84/02111 to construct a sea anchor or drogue in the form of a generally hollow body having a conical front portion and a frustoconical rear portion from which extends stabilising vanes. A number of movable doors are provided in the front part which open at higher towing speeds as to expose the forward edges of the rear part of the body. This permits water to enter the interior of the body and considerably increases the drag of the device.
It is also known to construct a device similar to that described above in which the doors are fixed in an open position and a water outlet port is provided in the centre of the rear part. As the sea anchor is towed through the water, the exposed forward edge of the rear part directs water inwardly of the rear part and is expelled from the port.
The object of the invention is to provide a novel construction of sea anchor or drogue which is simple, effective and robust.
According to the present invention there is provided a sea anchor or drogue comprising: generally frustoconical in shape; for towing the body in a forward direction; located adjacent to the rear end of the front part.
In one form of the invention, the water outlets are formed in the front part and are located adjacent to the rear end of said front part. Thus, the outlets of the invention are located, generally speaking, in positions corresponding to the inlets of known devices described earlier. In the device of the invention, the outlets are therefore located near the widest diameter part of the device and the water emerging therefrom as significant components in the radial direction. This tends to create considerable turbulence around the device and therefore increase the drag which it exerts on the towing line.
Preferably, the sea anchor or drogue includes secondary outlets which are located in the rear part of the device for permitting escape of streams of water in a generally rearward direction so as to stabilise the device as it is towed.
It is thought that at lower speeds of towing a relatively small volume of water enters the water inlet openings and a significant portion of water so admitted passes through the secondary outlets. In this mode the main drag exerted by the device is caused by water flowing over the external surface of the front part of the device. At higher speeds, more water enters the inlets and the major proportion of the admitted water will be expelled through the outlets located adjacent to the front and rear parts. This increases the drag exerted by the device. It is also thought that the streams of water passing through the outlets have the effect of deflecting streams of water passing along the surface of the front part further outwardly. This deflection is therefore functionally equivalent to increasing the diameter of the device and hence the amount of drag which it will exert on the towing line.
In an alternative embodiment, the rear part is movable relative to the front part. In one position, the front and rear parts engage one another whereby a relatively small amount of water will pass through the device and the drag exerted will be correspondingly low. As the speed increases, the rear part separates from the front part so as to open the main water outlet and in this mode the drag exerted will be higher.
The invention will now be further described with reference to the accompanying drawings:
FIG. 1 is a side view of a sea anchor or drogue constructed in accordance with the invention,
FIG. 2 is a longitudinal section through the device,
FIG. 3 is a frontal view of the device,
FIG. 4 is a rear view of the device,
FIG. 5 is a longitudinal section through a second embodiment of the invention,
FIG. 6 shows the embodiment of FIG. 5 with the main outlet open,
FIG. 7 diagrammatically illustrates the operation of the device at low towing speeds, and
FIG. 8 diagrammatically illustrates the operation of the invention at higher towing speeds.
The sea anchor or drogue illustrated in FIGS
REFERENCES:
patent: 3064613 (1962-11-01), Hubick
patent: 3310257 (1967-03-01), Price
patent: 4562788 (1986-01-01), Abernethy
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