Ignition on or motor on is not a big deal, as in previous page above I've calculated assuming car was driven into ocean;
- force on the car entering the water at 60km an hour off the groyne (4,800 N
- driven off the boat ramp (800 N
- compared to 1968 Fiat 125 in controlled testing of 12 year old cars in 1980. Force applied in a rollover at 100km/hr is a minimal 8,000 N
(assuming it didn't touch ground until final crash) to 11,000 N
where it touches ground 9 times in the rollover, and there is a summation of 9 smaller forces.
The pictures in the above previous posts show no damage
to the car body in this rollover, even after 11,000N
. There looked like there was damage to the wheels and it could been unable to be driven.
This car was a tank and incomparable to old bashers in the field which could be tin cans with no comparative variables. JC's Fiat was 18 to 20 years old, not 12 years old like the Fiat 125 in the controlled tests, so I accept a margin of error or ball park figures.
I am only stating facts and I always assumed the car was driven off the groyne before doing this analysis. No method or speed of the Fiat going into the ocean from the beach come two or three times near the force needed to cause the damage that occurred.
- force of car banging against groyne F=ma F = 1100kg x 2m.s.s F = 2,200N
This assumes the force is applied to the roof of the car when it hits the groyne, and any current or rip is taking it to the groyne, which is probably not the case.
- I have a calculation for the car being dropped off a cliff or higher. F = ma F = 1150kg x 9.8 (acceleration due to gravity) = 11,000 N
I also looked at the force of the car being hit by a locomotor engine with known variables except the weight of the engine. Force was 30000 N (100 ton engine) to 65,000 N
(192 ton engine). The resultant damage was huge with the force applied to the side of the car, except that the roof and roof supports were undamaged.
- force of waves hitting car is harder to calculate but the force is being applied by each wave to a 1,100 kg car and IMO would be less that the car hitting the groyne while in the water. I agree with met that if there was a rip it would be in the position she is showing for the swell and wave conditions at the time. If you have a rip current like met shows you don't have waves but have current in that area. The most force applied would be if the car was on the sand and the waves were breaking on the car. The force would have to be applied directly to the roof to get the damage that resulted, so you are looking at at least 6 foot waves dropping directly down on car. Picture of 4 WD, (quoted in Car V Ocean pages), driven into large waves at Lancelon, stayed in this wave drop zone for 2 hours and sustained no damage. Car being found 35 to 50 m off the beach it would be below waves.
Buoyancy calculations (below) show a buoyancy factor of 10 which would mean it would sink very quickly and remain close to where it went in the water. It would also be filling up with water as it was sinking and sink even quicker. Any current from a rip would be much less under water and wave effect negligible under water.
Car was winched into shore and there has been suggestion that the damage to the roof may have been caused then. Towing mechanics is applied, where the man force is on the rope and has been previously discussed as 2000N or less. If the car roof got caught on reef it could either peel the roof off like a car opener or break the rope/chain. Pictures (Olsson 2004) show mid beach reef not a huge factor before 2000. Also I was waiting for conformation from photos taken in the water that damage occurred before the tow. The main forces applied in towing are horizontal and not vertical needed to cause damage to roof.
Rust could have been a factor and I think this is why the roof was crushed on an angle, if there was any weaknesses in the roof supports.
From my calculations the force applied to the roof of the car would have to be conservatively 30,000N or more to cause the damage that occurred. This is three times more than the car being tossed off a cliff, three times more than in a rollover at 100km/hr or more than 6 times more than going off the groyne at 60km / hr and many times more that being bashed by waves IMO. I welcome comment by met with expert wave data as I could calculate forces by each wave more accurately but from my calculations it would have sunk very quickly. Even if my margin of error is 40% the damage to the car could not have been caused by any natural means IMO. Damage to car and car entering at Cott IMO was two separate events. This is not what I have assumed for the last 30 years but the only conclusion I can come to by looking at the facts.