Nelson & His World

Hello All,
Knowing that the seas off Cape Trafalgar are pretty deep, but I would like to know if any form of underwater survey has been conducted in the past using side scan sonar or Sub bottom profiling?

Cheers,

Stephen

Hello Stephen,

I have no idea whether a survey of this kind has been carried out to date, I can find no mention of one, but my guess is that it hasn't seeing the depth of water and the strong tides, which would make such a survey very difficult. However, as you may know, it is proposed by the Spanish government that a windfarm be built on the site of the Battle of Trafalgar:

http://technology4life.wordpress.com/20 ... ind-parks/

Whilst I have no particular personal qualms about this myself, it is also interesting to note that the late Colin White didn't appear to have either - I believe his view was that because the battle took place over such a wide area, as sea battles tend to do, there is no actual 'site' as such. It would, however, be interesting to know whether a survey of any type is proposed before construction commences, and I would have thought that one would have been carried out just to make sure the sea bed is suitable for installing the wind machines themselves, at the very least. If such a survey could also incorporate an archaeological survey as well, that would be ideal. I wonder however, if anyone has approached the Spanish Government with this suggestion? I am sure there are many interested parties who would be happy with this, although it seems as though the local provincial authorities and fishermen are not!

Are they really that deep??

It's just that I recall having an interesting dialogue with a guy once - about the possiblity of recovering some "Trafalgar cannon balls". We did some initial research and concluded that it was eminently "doable".

Albeit we were just 2 keen amateurs and there might have been all sorts of flaws in our research.

Suffice to say I don't have a Trafalgar cannon ball as a door stop for my living room door - which was the ultimate dream!!

MB

Anna, Mark,

I thought many might find this article on floating wind turbines of interest:

http://news.bbc.co.uk/2/hi/business/8085551.stm

The article mentions the Iberian Peninsula as a possible site and that the wind turbines can be moored in depths of up to 700 metres.

Thanks for that, Kester. Mark might get his cannon ball after all!

For archeological survey, the strength of the prevailing current may pose a larger obstacle than the depth of water. Strong currents stop divers from working and very much reduce the mission time of battery-driven diving roboters. Recovering parts of wrecks to the surface in strong counter currents may put a very damaging strain on both wreckage and recovery equipment.

http://www.windtarifa.com/eng/anavegar/corrientes/currents.htm hints that that might be an explanation here.
Another question would be the expected state of decline of the objects in question and whether the state of the seabed permits reasonable search. In deep mud or shifting sands you could search till kingdom come without any success. However, I lack the charts of the area to tell the composition of the seabed, so my statement has to remain general as it is.

Best regards

Ned

Ned,

Thanks for that. You're right, the tides could be a major problem, especially since Trafalgar is just in the area where they are compressing to pass into or out of the Straits of Gibraltar.

You sound as though you have a knowledge of oceanography/diving.

.
Would be very interesting to develop this subject further if possible.

I guess that strong currents could mean that items like cannon balls have been buried out of sight.

But our logic was that there must be tens of thousands down there.

In very rough terms - if each ship fired 30 broadsides during the battle that would mean 60,000+ cannon balls down there somewhere.

MB

Kester,

you're right - I have been spending a few years of my life clearing away the underwater debris left there by generations gone by or retired by now...

Mark,

most of it depends on the composition of the seabed. If you have enough mud to have the cannon balls sink as deep as one or two feet, you won't have the means to discover them by sonar. I don't know how capable laser detection might be by now for detecting items buried in mud. In order just to recover some iron cannon balls, you could try a strong magnet. But if this would have to extract cannon balls out of deep mud success would be unlikely.

Crucial to the efficiency of all lowered equipment is again depth of water - with regard to position keeping and position determination of that equipment and with regard to the weight of the necessary cables.

If the seabed is even and hard bottomed, it would be easier to locate items there by means of sonar. But if there's a strong enough current down there, round items might be anywhere while the same currents might have torn the ships' hulls to pieces.
Environmental conditions will also have a decisive impact on the state of rottenness of wood, hemp and iron.
However, in the absence of those data, which - at least for current and seabed composition - will be readily available in the relevant publications, my words are only the basis for mere speculation.

So long

Ned