Tanks & Bulldozers Project Brief July 2008
Aim of the survey • We are looking to produce a site map which identifies & records the position/orientation of artefacts at the dive site. • Known Items • 2 Centaur CS IV Tanks • 2 Armoured Bulldozers • 1 Ammunition sled – “Porpoise” • 1 Field gun + Ammunition • Note: No items to be removed from the site
Top Gun 10m Hard boat with lift & toilet 12 Divers + 2 Crew Skippered by Dave & Liisa Wallace Cruising at 20knots
Boarding & Loading Top Gun On Saturday from Southsea Marina Other days probably from the Ferry Pontoon as normal Allow AT LEAST30 min before boat leaves Bring food and drink We will return to Langstone Harbour between dives.
Diving Safety Medically fit to dive Equipment serviced, working + suitable for the task Plan your dive and have it written on a slate with any deco stops Air & Gas – make sure that you have enough (rule of thirds) I would suggest leaving stages at home for this type of diving Using 32% will give you a 56minute No Stop Dive Monitor your air regularly Risk register – be aware of the risks Visibility – fining techniques Buoyancy control – be precise DO YOUR BUDDY CHECKS
Typical Dive plan Dive 1 Air – Assuming 25 SL/min Dive 2 Air
Enriched Air Dive Plan Dive 1 Nitrox 32 Dive 2 Nitrox 32
Air consumption • Dive Plan 32 mins at 20m = 3 bar Absolute • 15L x 232 bar = 3480L free air • 80 bar reserve = 1200L reserve • 2784 – 1200L = 2280 available air • 3bar x 25 SLM x 32 mins = 2400L • Leaving -120L into reserve, 1080 reserve left
How will we conduct the survey? Various techniques can be used………….
Underwater Site Survey Techniques • Datums • Trilateration • Datum Offset • Planning Frame (possibly)
Archaeological Survey TechniquesDatum offsets Datum offset is about making measurements at 90° from a base line
Planning FrameThe planning frame is used to record artefacts in detail in their exact position
Recording artefacts To make accurate detailed recording the diver should be positioned directly above the frame and requires precision buoyancy control
TrilaterationIs about making angular measurements from a control point
Trilateration Measuring from a control point to an artefact or another control point
Overall Survey Plan • Day 1 – Mark out the site+ Permanent buoys • Day 2 – 3 Site Measurements • Day 4 – Perimeter search & Wreck measurements • Day 5 – SeaSearch + Final measurements + site clear up
Marking out the site • Base Points – Boundary of the site – useful for measuring outer items • Control Points – positioned at points which will allow meaningful measurements to be taken, both at lowest & highest levels • Depth of CP – Use Depth gauge – on sane dive ( state of tide)
Measuring Site For overall site Between Base Points & CPs Between CP’s (base level) For each item Between CP’s Specific points of interest 3 or more measurements from each CP will give a strong confidence in each measurement
Centaur CS IV Tank Fact File 114 produced 80 given to the RMAS Group for D Day Were mounted on ramps & fired over bow of landing craft to provide Close Support 28 made it to the beach 2 are surviving in France Fitted with a 95mm Howitzer Gun (51 rounds of ammunition) 1x BESA machine gun 28 tons – 27 mph 5 crew
Caterpillar Armoured Bulldozer Fact File Caterpillar D7 or D8, but were modified with armour in England Know as “Hobarts Funnies” No known details of the modifications Only surviving ones known 23 to 34 Tons each
Porpoise – Ammunition sled Fact File Towed behind tank carrying ammunition (waterproofed) One found near bulldozer Anticipate finding one more Likely to have ammunition nearby
Anchor Fact File Found almost underneath tank Most likely from a landing craft Weight & Size unknown
Willy’s Jeep Fact File Little remains Engine block Axels & wheels & Tyres Willys is pronounced as ' willis - not ' willies' !
Field Gun Fact File Position unknown?