GB2190633A

GB2190633A - Towed underwater sledge

Info

Publication number: GB2190633A
Application number: GB08711689A
Authority: GB
Inventors: Marshal Ernest Albert Bloxham
Original assignee: UK Secretary of State for Defence
Current assignee: UK Secretary of State for Defence
Priority date: 1986-05-20
Filing date: 1987-05-18
Publication date: 1987-11-25
Also published as: PT84905B; AU7323087A; PT84905A; GB8711689D0; GB2190633B; EP0246853A1; GB8612281D0; NZ220363A

Description

1 GB 2 190 633 A 1 SPECIFICATION provide directional stability.

Preferablythe keel and skegs extend belowthe steering and elevation Towed underwater sledge means such thatwhen the sledge is out of thewater and lying flat, it rests on the keel and one of the skegs The invention relatesto a sledge on which a diver 70 and thus avoidsthe riskof damaging the steering can be towed underwater by a vessel particularly, and elevation means on the ground.

but not exclusively,to enablethe diverto observethe Advantageously the keel and skegs areformed in sea bed. one piece with the wing. Alternatively they may be In many situations there are advantages in having attached to the wing.

a divertowed by a vessel. Avessel can towthe diver 75 The upper deflector screen deflects the flow of at greater speeds and over greater distances than a water overthe diver while the sledge is being towed.

diver can swim. Furthermore, the diver remains in Preferably the upper screen is of a size such as to contactwith the vessel. ensure thatthe pressure of the water flow is kept off Sledges known in the prior artwere originally the diver's body atthe maximum desired towing made of wood and were large and heavy, making 80 speed. Advantageously the upper screen keepsthe them awkward to handle on land and difficuitto waterflow pressure off the body of the diver up to a manoeuvre in the water. In use they become satura- speed of at least 5 knots. Above the maximum design ted with water and lost buoyancy, making them un- speed, turbulence will begin to affectthe diver.

suitable for long periods of use. Awooden screen The lower deflector screen def lects the f low of was fitted to the front of the sledge, to deflectthe 85 water underthe sledge, creating an area of low pres waterflow overthe diver riding on the sledge,which sure (hereinafter referred to as a "rnoonpooV) ben greatly restricted the visibility for the diver. Lighter eath the viewing section down through which the sledges of metal tubing frames with transparent diver can then see clearly. Preferably the lower def screens are also known butthese still have the pro- lector screen is secured to the lower edge of the blem of restricted visibility due to the buoyancy mat- 90 upper deflector screen. The securing means should erial and the material used forfastening the screens be such that it does not adversely affect the diver's to the sledge. These sledges also lack manoeuvr- visibility. Preferablythe lower screen extends far en ability and stability when towed by a vessel. Additi- ough down to create a moonpool up to the max onally it is difficuitfor a diverto keep himself on the imum desired speed. Preferably the lower def lection sledge underwater and it is very dangerous for a 95 screen does not extend below the keel and skegs so diverto be tied to a sledge or attached by any means that it is protected from damage and does not adver that is not instantly releasable if necessary. sely affectthe flow of water pastthe keel and skegs.

The object of the invention is to provide a sledge, Advantageously the screens are made of a strong on which a diver can be towed underwater by a transparent plastics material such as perspex vessel, which provides good visibility down towards 100 (R.T.M.) or any other suitable strong, transparent the sea bed. material.

The sea bed is here taken to include the bed of any Preferably the screens are curved to form a more body of waterthrough which the sledge can be hydrodynamic shape and to avoid problems caused towed eg sea, lake or river. byf lexing which occurs when a flat screen is subject It is a further object of the invention to provide 105 to the pressure of the waterflow.

such a sledge which is lightweight, portable, easily Preferably the screens are detachable for easier manoeuvrable in water and which does not lose transportation of the sledge on land.

buoyancy during use. Advantageously the sledgewing is a "dished The invention provides a sledge on which a diver delta" shape in that it is wider at the rearthan atthe can be towed underwater by a vessel, comprising: 110 front and is curved upwards towards the sides.

a) a positively buoyant sledge wing; Preferably the sledge wing is made of plastics mat b) means to attach the sledge to a towing vessel, erial and is hollow. Preferably it is filled with a high which means includes two towing lines from the density, buoyantfoam material. Advantageously the sledge attached one on each side of the sledge wing plastics material is glass reinforced plastics (GRP).

at a pointforward of the lateral centre of pressure 115 Alternatively the wing may be made out of keviar and the centre of gravity of the sledge; (R.T.M.) or any other suitable material. The material c) steering and elevation means; must be suitable for forming the sledge wing and d) a transparent upper deflector screen atthe must be able to withstand the environment of use front of and extending above the said sledge wing; without damage such as corrosion. The high water e) a viewing section through the said sledge 120 pressures experienced by the sledge at depth mean wing at its forward end; that it is very difficult to make a completely leak-free f) a transparent lower deflector screen atthe sledge, however the foam fill i ng ensures that not front of the said viewing section and extending much water can enter the wing body and hence that belowthe said sledge wing; and the sledge does not lose its buoyancy.

g) means by which the diver can hold his body on 125 Advantageously the wing contains one or more the sledge. drain holes and plugs such that any waterwhich has Preferablythere is provided a keel on the under- been forced in under pressure while the sledge is un- side of the sledge wing, running foreto aft. Advan- derwater can be allowed to drain outwhen the tageouslythere are also provided two skegs, parallel sledge is removed from the water. Convenientlythe to and on either side of the keel. The keel and skegs 130 keel and skegs also contain drain plugs.

2 GB 2 190 633 A 2 Preferably the wing is of a length and width to en- The thigh post has an additional advantage in that able a diver to lie comfortably on it. Conveniently, so it is easy for the diver to release his grip on the post if as to retain maximum strength of the wing material if he wishes to leave the sledge.

a material such as GRP is used, the wing shape is Alternatively afoot rest can be provided in the such that all the surfaces are in shear stress and not 70 form of a bar across the rear of the sledge under in tension stress. which the diver can position his feet.

Preferablythe means to attach the sledge to a tow- Preferablythe sledge is ballasted such that it has a ing vessel comprises two towing lines from the desired amount of reserve buoyancy. Preferablythe sledge to a towing foil and then towing lines from the reserve buoyancy is about 1 Okg. Normally a diver is foil to the vessel. Preferablythere is one line from the 75 weighted to zero buoyancy so he will not affectthe foil to the vessel. Preferablythe towing foil is posi- buoyancy of the sledge. Conveniently the ballast is tively buoyantto compensate forthe weight of the used to trim the sledge. Advantageously the ballast tow line. Preferabiythe towing foil is made of hollow is secured to the steering gear atthe rear of the glass reinforced plastics and is advantageouslyfilled sledge. Convenlentlythe ballast comprises lead with a high density, buoyantfoam material. Conveni- 80 weights.

entlythefoil has about 1 kg reserve buoyancy. Preferablythere is included a grab rail atthefront Advantageously the towing lines are attached to of the sledgeto protectthe upper deflector screen.

towing brackets mounted on eitherside of the sledge Additionallythe grab rail enablesthe sledgeto be wing. Preferablythe attachment pointisjust in front steadied on land orwhen it is placed in thewater of the lateral centre of pressure and of the centreof 85 withoutthe upper deflectorscreen being held,which gravity of the sledge. Preferably the towing position would bring the risk of damaging the upperdeflector is such asto give maximum controllability of the screen. Preferablythe grab rail is of hollowtubing.

sledge. Preferablythe distance apart of thetwotow- Preferably it is of glass reinforced plastics material ing points on thetowing foil is the same as the dis- and conveniently it is filled with a high density, tance apart of the towing points on the sledge. 90 buoyantfoam material. Conveniently the rail is det Preferablythe steering and elevation means com- achablefor easier transportation of the sledge on prise elevons controlled by means of control rods. land.

Advantageously there are two elevons controlled by Preferablythe lower deflector screen does not ex means of two control rods. Preferablythe elevons tend below the level of the keel.

are atthe rear of the sledge and are connected by 95 Preferably there are provided crash/skid bars atthe means of linkages to the control rods atthe front of front of the sledge to protectthe sledge and the the sledge. Convenientlythe elevons are attached to lower deflector screen on land or if the sledge should the sledgewing by means of steering gear brackets. hit an obstacle in the water. The crash/skid bars Advantageously the elevons have a hydrodynamic cause the sledge to slide over an obstacle, reducing form. Convenientlythey are made of plastics mat- 100 the chance of damage to the sledge or injuryto the erial, advantageously GRP. Advantageously the el- diver.

evons are hollow and holed and are free-flooding. Preferably a communication device is provided to Preferablythe linkages are made of stainless steel enable the diverto communicate with the towing and advantageously they are formed of hollowtub- vessel. Conveniently a voice communication device ing, where possible, to increase the buoyancy of the 105 is provided between the diver and the vessel. Altern sledge. atively the communication device may comprise a Preferablythe control rods control the elevons push-button type switch on one of the control rods such that pushing the control rods forward causes and a continuous cable linkto the surface vessel ter the sledge to dive, pulling them back causes itto minating in an indicator unit. Conveniently com climb and pushing one forward and pulling the other 110 munication may be by means of a simple code of the back causes itto bank. In this way the divercan con- number of signals sent from the diverto thevessel.

trol the steering and elevation of the sledge. This The indicator unit is conveniently arranged to dis steering arrangement is simple and cheap to make play the signals by means of visual or audible signal and fitto the sledge. It can also be used for long per- displays.

iods of time bythe diverwithout being overtiring. 115 Conveniently there are hoisting points on the Alternatively steering may be by means of a single sledge so that it may easily be lowered to and lifted joystick control connected by means of linkages to from the water surface. Preferablythe hoisting the elevons atthe rear of the sledge. This arrangepoints comprise four "D" rings attached to the ment has the advantage that the diver is left with one sledge wing to which ropes or other lifting means hand free for other purposes. 120 maybe fastened. Advantageously the "D" ringsare Preferably the diver holds his body on the sledge attachedoneon eachtowing bracketand oneon byrneansofathigh grip post on the sledgewing. each outboard bracket of the stern steering gear.

Preferablythe post is moveable in various positions Conveniently the "D" rings are made of welded along the length of the sledge so that it can be adju- stainless steel.

sted to the most comfortable position forthe diverto 125 Advantageously the M" rings on the stern steer grip with his legs to hold himself on the sledge. ing gear brackets may also be used as anchor points Convenientlythe post is moveable in three posi- for detachable straps to hold the elevons in a "tail tions. It has been found that a range of about 20cm up" attitude to preventthe sledge from diving so that between theforemost and the rearmost positions it can be towed along the surface without a diver on will enable most divers to grip the post comfortably.130 board.

3 GB 2 190 633 A 3 Conveniently the sledge may also carry marker moon pool". This allows the diverto see clearly floats, with sinkers, which the diver on the sledge can downwards. The screens 8, 10 are curved so that deploywhilst submerged or on the surface so that he they do not deflect underthe pressure of thewater can mark a particular spotfor himself orforfuture flow. With flat screen the water flow causes them to divers. 70 deflect and this may cause them to break, part Advantageously a miniature closed circuittelevi- icularly in colder waterwhere the plastics material sion camera may be mounted on the sledge. Con- may become more brittle. The curving gives max venientlythe monitor is on thetowing vessel. This imum strength for minimum weightof the screens.

will enable people on the surfaceto view picturesof Theviewing section 9 combined with the deflection the sea bottom, controlled bythe diver on thesledge. 75 screens 8, 10 encourage the diverto lookforward So that the time taken to reach the diving area can and down in a natural sweep of the eyesforoptimum be reduced,the sledge can preferably be adapted so visibility.

that a diver can ride on it, in the manner of water Crash/skid bars 11,12, 13 extend in front of and skiing, onthe surface. Preferably a quick release rein belowthe wing 1 to protectthe sledge in the eventof is attached tothetowing brackets on thesledge 80 a collision with an obstacle.

wing.The diver holds onto this rein while standing Agrab rail 14, supported by bars 15,16, is posi- up asthe sledge istowed bythetowing vessel. Con- tioned overthetop of the upperscreen 8to protect it venientlythe rein is removed from the sledge once and to enablethe sledgeto be steadied when it is the diving area has been reached. placed in the water, without risk of damaging the In orderthat the invention may be more fully un- 85 upper screen 8.

derstood, itwill now be described, byway of ex- Referring nowto Figure 3 aswell, control rods 17, ample only,with reference to the attached drawings 18 atthefront of the sledge are connected by means of which: of linkages 19,20 to elevons 21, 22 mou nted atthe Figure 1 is a plan view of a sledge according to the rear of the wi ng 1. The control rods 17,18 are pivoted invention; 90 on the cross-bar 23 such that pushing the control Figure2 is a cross-section along the line X-X of the rods 17,18 forward pulls the linkages 19,20forward, sledge shown in Figure 1; and which rotates the elevons 21, 22 clockwise to a "tail Figure 3 is an end view of the steering gear atthe down " position via the linkages 24,25, thus causing rear of the sledge, as shown in Figures 1 and 2. the sledge to dive. Pulling the control rods 17,18 Referring to Figures 1 and 2, a sledge according to 95 backwards pushes the linkages 19,20 back, thus the invention is shown. The sledge body comprises a rotating the elevons 21, 22 in an anti-clockwise direc solid wing 1 which is of a "dished delta" shape in that tion to a "tail- up" position and hence causing the it is wider atthe rearthan atthe front end and is sledge to climb. Banking to port or starboard is effec curved up towardsthe edges. A "dished delta" ted by pushing one control rod, 17 or 18, forward and shape has advantages over a flat, rectangular shape 100 pulling the other back. The elevons 21, 22 are of a for stability both on and below the watersurface. hydrodynamic shape so that they reduce the hydro Towing brackets 2,3 are attached one on each side dynamic performance of the sledge by as little as of the wing 1 at a position forward of the lateral possible.

centre of pressure and of the centre of gravity of the Athigh grip post 26 is positioned along the centre sledge. If the towing position is too farforward the 105 line of the wing 1. When a diver lies on the sledge he sledge will not be manoeuvrable and it will be very grips the post 26 between his legs and this enables difficult to make it dive. The furtherforward thetow- him to remain in bodily contactwith the sledge. A ing point is, the greaterwill bethe tendencyforthe support 27 assists in holding his legs in place. If the sledge to rise towards the surface when it is towed, diverwishes to bale outfrom the sledge he need only which makes itvery difficuitto control. On the other 110 release his legs from the post 26 and float awayfrom hand, if the towing position is behind the lateral the sledge. The sledge buoyancy will then cause itto centre of pressure or the centre of gravity of the floatto the surface.

sledge, the sledge will tend to stall and will dive ver- The post 26 can be positioned in any one of three tically in the water. holes 28a,b,c in the wing 1 so that it is in the most Towing lines 4,5 are attached to the brackets 2,3 115 comfortable position forthe diver.

and terminate at a towing foil 6. A singletowing line A keel 29 extends belowthewing 1 and two skegs 7 passesfrom thefoil 6to a towing vessel (not 30,31 run parallel to the keel 29 along thewing 1. The shown). keel 29 and skegs 30,31 provide directional stability An upper deflector screen 8 of transparent plastics forthe sledge. The depth of the skegs is such that material is attached atthe front of the wing 1. This 120 when the sledge is on land itwill rest in the keel 29 screen 8 deflects the waterflow over a diver riding on and one skeg, 30 or 31, such that the steering gear the sledge but still allows forward visibility. Aview- does nottouch the ground, as indicated bythe dot ing section 9 is formed in thefront of the wing 1, ted line 32. Additionally the lower def lection screen down through which a diver on the sledge can view 10 does not extend belowthe keel 29 orthe skegs 30, towards the seabed. 125 31 and thus there is no interference in the flow of Attached to the lower edge of the upper deflector water between the keel 29 and skegs 30,31 so that screen 8 is a lower deflector screen 1O.Thisscreen10 the directional stability and manoeuvrability of the deflects the water flow below the viewing section 9 sledge are maintained leaving an area of low pressure beneath the viewing The elevons 21, 22 are attached to the rear of the section 9 where the water is still and clear, like a 130 wing 1 by means of brackets 33,34,35,36. Ballast, in 4 GB 2 190 633 A 4 the form of lead weights, can be attached to the wing means such that when the sledge is out of the water 1 atthe mounting points 37,38,39,40. and lying flat, it rests on the keel and one of the skegs The wing 1, keel 29 and skegs30,31 are made of and thus avoids the risk of damaging the steering glass reinforced plastics filled with a high density and elevation means on the ground.

foam material 41. 70 5. A sledge according to anyone of the preceding Hoisting rings 42,43,44,45 are attached to the claims wherein the upper screen is of a size such as sledge on the towing brackets 2,3 and the steering to ensu re that the pressure of the waterf low is kept gear brackets 33,36 for easier lifting and lowering of off the diver's body at the maximum desired towing the sledge from and onto the water surface. speed.

The sledge of the invention has many advantages 75 6. A sledge according to anyone of the preceding overthe prior art in that is is very controllable, man- claims wherein the lower deflector screen deflects oeuvrable and stable. It has good hydrodynamic pro- the flow of water underthe sledge, creating an area perties and is easy, comfortable and non-tiring to of low pressure beneath the viewing section down ride and steer. It is protected against damage on land through which the diver can then see clearly.

orthe seabed. It is very robust and easy and cheapto 80 7. A sledge according to claim 6 wherein the maintain. lower deflector screen is secured to the lower edge The sledge is ideal for use in searching or scientific of the upper deflector screen.

observation of the seabed, forwreck searching and 8. A sledge according to claim 7 wherein the sec surveying orfor pleasure use such as looking atJor uring means does not adversely affect the diver's example, coral reefs. A vessel can towthe sledge fas- 85 visibility.

ter and over greater distances than a diver can swim 9. A sledge according to anyone of the preceding by himself and also has the advantage, particu larly claims wherein the lower deflector screen does not for less experienced divers, of continuous contact extend belowthe level of the keel and skegs.

between the diver and thetowing vessel. 10. A sledge according to anyone of the preced The thigh post device by which the diver holds 90 ing claims wherein the screens are made of a strong himself on the sledge is easy to release should it be transparent plastics material.

necessaryforthe diverto leave the sledge suddenly. 11. A sledge according to anyone of the preced This increases the safety of using the sledge as it can ing claims wherein the screens are curved.

be very dangerous fora diver to be tied or otherwise 12. A sledge according to anyone of the preced attached to the sledge by a means that is not in- 95 ing claims wherein the screens are detachable.

stantly releasable. The buoyancy of the sledge 13. A sledge according to anyone of the preced means that it will return to the surface making it easy ing claims wherein the sledge wing is a "dished to retrieve. delta" shape in that it is wider atthe rearthan atthe One or more sledges can be towed by thevessel front and is curved upwards towards the sides.

and the sledge can also be adapted to carry more 100 14. A sledge according to anyone of the preced than one diver. ing claims wherein the sledge wing is made of plas tics material and is hollow.

Claims

CLAIMS 15. A sledge according to claim 14wherein the sledge wing is filled

with a high density, buoyant 1. A sledge, on which a diver can be towed under- 105 foam material.

water by a vessel, comprising: 16. A sledge according to anyone of the preced a) a positively buoyant sledge wing; ing claims wherein the wing contains one or more b) means to attach the sledge to a towing vessel, drain holes and plugs such that any water which has which means includes two towing lines from the been forced in under pressure while the sledge is un- sledge attached one on each side of the sledge wing 110 derwater can be allowed to drain outwhen the at a pointforward of the lateral centre of pressure sledge is removed from the water.

and the centre of gravity of the sledge; 17. A sledge according to claim 16 wherein the c) steering and elevation means; keel and skegs also contain drain plugs.

d) a transparent upper deflector screen atthe 18. A sledge according to anyone of the preced front of and extending above the said sledge wing; 115 ing claims wherein the means to attach the sledge to e) a viewing section through the said sledge a towing vessel comprises two towing lines from the wing at its forward end; sledge to a towing foil and then towing lines from the f) a transparent lower deflector screen atthe foil to the vessel.

front of the said viewing section and extending 19. A sledge according to claim 18 wherein there below the said sledge wing; and 120 is one line from the foil to the vessel.

g) means by which the diver can hold his body on 20. A sledge according to claim 18 or 19 wherein the sledge. the towing foil is positively buoyant to corn pensate 2. A sledge according to claim 1 wherein there is for the weight of the towline.

provided a keel on the underside of the sledge wing, 21. A sledge according to anyone of claims 18to running fore to aft. 125 20 wherein the distance apart of the two towing 3. A sledge according to claim 2 wherein there points on the towing foil is the same as the distance are provided two skegs, parallel to and on either side apart of the towing points on the sledge.

of the keel. 22. A sledge according to anyone of the preced 4. A sledge according to claim 3 wherein the keel ing claims wherein the attachment point is just in and skegs extend below the steering and elevation 130 front of the lateral centre of pressure and of the GB 2 190 633 A 5 centre of gravity of the sledge.

23. A sledge according to anyone of the preceding claims wherein the steering and elevation means comprise elevons controlled by means of control 5 rods.

24. A sledge according to claim 23 wherein there are two elevons controlled by means of two control rods.

25. A sledge according to anyone of claims 1 to 23 wherein steering is by means of a single joystick control connected by means of linkages to the elevons at the rear of the sledge.

26. A sledge according to anyone of claims 23 to 25 wherein the elevons are at the rear of the sledge and are connected by means of linkages to the control rods at the front of the sledge.

27. A sledge according to anyone of claims 23 to 26 wherein the elevons are attached to the sledge wing by means of steering gear brackets.

28. A sledge according to anyone of claims 23 to 27 wherein the elevons are hollow and holed and are free-flooding.

29. A sledge according to anyone of the preceding claims wherein the diver holds his body on the sledge by means of a thigh grip post on the sledge wing.

30. A sledge according to claim 29 wherein the post is moveable in various positions along the length of the sledge so that it can be adjusted to the most comfortable position for the diver to grip with his legs to hold himself on the sledge.

31. A sledge according to claim 30 wherein the post is moveable in three positions.

32. A sledge according to anyone of claims 1 to 28 wherein the diver holds himself on the sledge by means of afoot rest in theform of a bar acrossthe rear of the sledge under which he can position his feet.

33. A sledge according to anyone of the preced- ing claims wherein there is included a grab rail atthe front of the sledge.

34. A sledge according to claim 33 wherein the rail is detachable for easier transportation of the sledge on land.

35. A sledge according to anyone of the preced ing claims wherein there are provided crash/skid bars at the front of the sledge to protect the sledge and the lower deflector screen on land or if the sledge should hit an obstacle in the water.

36. A sledge according to anyone of the preced ing claims wherein a communication device is prov ided to enable the diverto communicate with the towing vessel.

37. A sledge according to anyone of the preced- ing claims wherein means are provided to hold the elevons in a "tail up" attitude to prevent the sledge from diving so that it can be towed along the surface without a diver on board.

38. A sledge as hereinbefore described with re- ferenceto the accompanying drawings.

Printed for Her Majesty's Stationery Office by Croydon Printing Company (1.1 K) Ltd, 10187, D8991685. Published by The Patent Office, 25 Southampton Buildings, London, WC2A lAY, from which copies may be obtained.