Deflector devices
View Patent ↗A deflector device ( 22 ) for use with a tow lie between a towing vessel ( 10 ) and a tow ( 16 ) in water behind the vessel, the device comprising a principal wing-shaped body ( 28 ) shaped to produce in use a sideways force which urges the tow line ( 16 ) laterally with respect to the direction of movement of the towing vessel, a boom ( 32 ) extending rearwardly from the principal wing-shaped body ( 28 ), and an auxiliary wing-shaped body ( 52 ), smaller than the principal wing-shaped body ( 28 ), secured to the end of the boom ( 32 ) remote from the principal wing-shaped body ( 28 ) and shaped so as to produce in use a sideways force in generally the opposite direction to that produced by the principal wing-shaped body ( 28 ).
1. A deflector device for use with a tow line between a towing vessel and a tow in water behind the vessel, the device comprising a principal wing-shaped body shaped to produce in use a sideways force which urges the tow line laterally with respect to the direction of movement of the towing vessel, a boom extending rearwardly from the principal wing-shaped body, and an auxiliary wing-shaped body, smaller than the principal wing-shaped body, secured to the end of the boom remote from the principal wing-shaped body and shaped so as to produce in use a sideways force in generally the opposite direction to that produced by the principal wing-shaped body.
2. A deflector device as claimed in claim 1 , further comprising remotely-operable means for adjusting the angle between the boom and the principal wing-shaped body to vary the sideways force produced by the principal wing-shaped body.
3. A deflector device as claimed in claim 2 , wherein the auxiliary wing-shaped body is secured to the boom at or near its trailing edge, with its chord extending outwardly from the boom, on the side thereof opposite to the principal wing-shaped body, at an angle to the boom substantially equal to half the angle through which the boom is adjustable.
4. A deflector device as claimed in claim 2 or claim 3 , wherein the remotely-operable means includes a hydraulically-actuated telescopic strut.
5. A deflector device as claimed in claim 1 , wherein the angle between the boom and the principal wing-shaped body is substantially fixed, and further comprising remotely operable means for varying the angle of the auxiliary wing-shaped body to vary the sideways force produced by the auxiliary wing-shaped body, and thereby vary the sideways force produced by the principal wing-shaped body.
6. A deflector device as claimed in claim 5 , wherein the remotely-operable means comprises an electric motor.
7. A deflector device as claimed in claim 5 , wherein the remotely-operable means comprises a hydraulic actuator.
8. A deflector device as claimed in claim 1 , wherein the auxiliary, wing-shaped body is provided with a trailing edge flap angled away from the boom, typically at about 35°.
9. A deflector device as claimed in claim 1 , wherein the end of the boom remote from the principal wing-shaped body connects to the tow.
10. A method of performing a marine seismic survey, the method including towing a plurality of laterally spaced seismic streamers over an area to be surveyed, wherein the lateral position of at least one of the streamers is controlled by a deflector device comprising a principal wing-shaped body shaped to produce in use a sideways force which urges the tow line laterally with respect to the direction of movement of the towing vessel, a boom extending rearwardly from the principal wing-shaped body, and an auxiliary wing-shaped body, smaller than the principal wing-shaped body, secured to the end of the boom remote from the principal wing-shaped body and shaped so as to produce in use a sideways force in generally the opposite direction to that produced by the principal wing-shaped body.
11. The method of claim 10 comprising varying the angle between the boom and the principal wing-shaped body to vary the sideways force produced by the principal wing-shaped body by adjusting a remotely-operable means for adjusting the angle.
12. The method of claim 11 comprising securing the auxiliary wing-shaped body to the boom at or near its trailing edge, with its chord extending outwardly from the boom, on the side thereof opposite to the principal wing-shaped body, at an angle to the boom substantially equal to half the angle through which the boom is adjustable.
13. The method of claim 11 wherein the remotely-operable means includes a hydraulically-actuated telescopic strut, and the method further comprises actuating the hydraulically-actuated telescopic strut.
14. The method of claim 11 comprising substantially fixing the angle between the boom and the principal wing-shaped body, remotely varying the angle of the auxiliary wing-shaped body to vary the sideways force produced by the auxiliary wing-shaped body, thereby varying the sideways force produced by the principal wing-shaped body.
15. The method of claim 11 comprising providing the auxiliary, wing-shaped body with a trailing edge flap, and angling the trailing edge flap away from the boom, typically at about 35°.