Sea-Dweller and it's depth rating...

2449 Views 12 Replies 10 Participants Last post by  Mike295855
I'm going to throw out a couple questions. As I said in a previous post, I'm definitely not the physics maybe you folks can help me out with this. First of all, before I get to my MAIN question, just as a sidebar, if you have a watch, for example, the Sea-Dweller, which says it's good to 4,000 feet, does it literally mean 4,000 feet beneath the surface? Or is that 4,000 feet of pressure? Or is it the same thing?? I guess what I'm trying to ask is, lets say you're underwater 20 feet below the surface, and you're stationary. Then you start swimming. Once you start, does your motion, because of the resistance of the water, thereby exert MORE pressure on the watch, even though you're still at the same depth of 20 feet? You folks see what I'm getting at? Just kinda wondered exactly how that worked. As far as the main question thought...I was curious...why do we need the new Deep Sea to be rated at almost 13,000 feet? And I ask because, and maybe I'm wrong here, someone please correct me if necessary, but since no one will ever be going down that deep unless you're in a pressurized submersible, then technically, it wouldn't matter what the depth rating is, because the submersible is pressurized, isn't that true? That would mean that, in a pressurized submersible, at 10,000 feet below, a day date is as good as a GMT-Master is as good as a Deep Sea. Or is there something that I am seriously overlooking here?? I'm not here to do any bashing, you folks know that I do love my rolexes, and I appreciate the impressive statistics of the new Deep Sea...I'm just trying to figure out some physics here...any one have any thoughts on this????
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To attempt to answer Sea-Dweller and bolster ScottD's frustration......

Yes, watch companies are not standardized in how they rate their product's water resistance. First of all, none of them actually place the watches in a crate and lower them into the ocean to their rated depth. Its all simulated in a high pressure machine. So right off the bat, its not 100% realistic. This frustrates people like Scott and myself. Mathematically recreating the textbook pressure conditions at 3900m is not the same as being at 3900m as depending on the test machine it doesn't take temperature, motion, and other factors into account.

And to Sea-Dweller's assertion that movement at a given depth can create additional pressure on the watch, you are correct! Were I swimming at 3900m and moving my arms back and forth, there would be eddies of current around the watch that create points of pressure that would be greater than the latent pressure at 3900m at the leading edge of my swim motion. Likewise, there would be points on the watch where there would actually be less than 3900m of typical pressure. The effect is similar to that of a wing on a plane whereby a pressure differential is created unequally to achieve lift. Having both areas of higher pressure and lower pressure on the same watch is more stressful to the watch. (Imagine play-doh in your hand and clinch a fist ... portions under greater pressure compress and the portions under lesser pressure such as between your fingers squirt out). This is the mechanical stress the watch being used for work under water would be subject to and it is more and less at the same time.

Most manufactures rate the watch to the depth the testing machine claims. Some manufacturers such as Seiko produce watches that handle far more than the claimed rating to take actual movement (and its additional stress into account). Thus I have no doubt a Seiko MarineMaster rated to 300m can actually handle 450m at rest. This is their safety margin and better reflects the watch's useful "working" depth.

We aren't sure what criteria Rolex uses for the DeaSea. Possibly this is why they made it so extreme. Rolls Royce never quotes the horsepower of their auto engines. They just claim power is adequate. INHO, the DeapSea may or may not hold up to work at 3900m, but it certainly is adequate.
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