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Dacor Constant Volume System- 1980

Discussion in 'Vintage Equipment Diving' started by sam miller, Oct 7, 2011.

  1. sam miller

    sam miller Public Safety Diver

    # of Dives: 5,000 - ∞
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    "NAUTILUS"

    Dacor Catalog - Page 18- 1980

    Constant Volume System aka CVS
    Hard shell BC - one model

    CVS--complete system
    CVSDW--Special weights
    CVSWF--Special Spacers for weights
    CVSCB-- Carring bag for complete system

    Prices not known,

    sdm
     
  2. John C. Ratliff

    John C. Ratliff Instructor, Scuba

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    Here are some photos of the Dacor Nautilus CVS from their 1977 catalog.

    SeaRat
     

    Attached Files:

  3. John C. Ratliff

    John C. Ratliff Instructor, Scuba

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    These are from a two-page ad in the 1977 Dacor catalog.

    SeaRat
     

    Attached Files:

  4. John C. Ratliff

    John C. Ratliff Instructor, Scuba

    # of Dives: I'm a Fish!
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    Here is the other part of the ad.

    SeaRat
     

    Attached Files:

  5. John C. Ratliff

    John C. Ratliff Instructor, Scuba

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    You know, the really funny thing about these catalog images show a diver using the Nautilus CVS with a shorty wet suit with almost no buoyancy. This BC was developed for people wearing a full wet suit, and not a shorty (what we used to call a 1/8 inch, but is now a 3mm). The use of a shorty wet suit with this Nautilus Constant Volume System (CVS) means that they did not realize the full potential of this device (the shorty wet suit looses virtually no buoyancy at depth). It is not for the tropics, but for cold-water diving. However, they cannot use it for under ice diving for the fear that water ballast would freeze inside the Nautilus CVS. So they kinda missed the market for this device.

    SeaRat
     
  6. Thalassamania

    Thalassamania Diving Polymath ScubaBoard Supporter

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    No, if you wore a cold water suit the CVS did not, of course, work because you had to keep adjusting for suit compression anyway.
     
  7. Luis H

    Luis H Instructor, Scuba

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    I totally agree.

    The unit only worked well if you did a true (theoretical) square dive profile.

    Every time you deviate from a constant depth it becomes a hassle to readjust the ballast chamber to compensate for wetsuit compression change. Of course, if the deviation is small, you just compensate with your lungs, but that is normally not practical with a heavy wet suit in most places where I dive.


    It says that it can have displacement of up to 60 Lb. All I can think of is that the unit would be ideal if you needed to lift an anchor and swim with it some distance. Just make sure to take the unit of your back and tie it directly to the anchor. It would be an ideal constant volume lift device (rather than a lift bag).


    This device has a lot of potential for something... I just haven't figured out what for yet... :D
    And I don't think Dacor did either...
     
    Last edited: Oct 11, 2011
  8. ZKY

    ZKY Minimalist ScubaBoard Supporter

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    Cool idea, kind of like a submarine ballast system but probably too complicated for the times and too much hassle needing to take a class just to use the thing.
    I can see that might have been the beginning of convoluted dive gear.

    The current trend is design by subtraction.
     
    Airleron likes this.
  9. Akimbo

    Akimbo Lift to Freedom Volunteer ScubaBoard Supporter

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    It looks like the small demand regulator on the end of the hose would freeflow if you tried to dump air when head-down, or was it tuned-down so a ~3' differential wasn’t enough to activate?
     
  10. John C. Ratliff

    John C. Ratliff Instructor, Scuba

    # of Dives: I'm a Fish!
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    For those of you who think the Dacor Nautilus CVS would not work with a full wetsuit, I'd like you to consider something. The wet suit looses almost all its buoyancy at about 33 feet in fresh water. In salt water there may still be a bit of buoyancy, but not much. I learned this lesson by taking my weight belt off and tying it to a butterfly knot loop in the boat's anchor line in the 1980s in Clear Lake, Oregon. I was using about 20 pounds of weight at that time, and when I took the weight belt off, I was completely weightless. I could swim down further, to about 65 feet, without any change in my buoyancy. I swam back up to the weight belt at 33 feet, put it back on and went to the surface. I regained that buoyancy as I ascended. I made a series of dives for the University of Oregon's Department of Exercise Physiology in Clear Lake in the 1960s while home on leave from the military, and did not use a weight belt or a BC at a depth of 66 feet (BCs weren't available then):
    [​IMG]

    Now, if instead I went down with that 20 pounds, and added air to a BC, I again would be weightless with about 1/3 of a cubic foot of air in my BC at 33 feet. If I went down to 66 feet, that buoyancy would decrease with the increasing pressure. If at 33 feet that 1/3 cubic foot of air represented 1/2 of the volume at the surface, it would have been 2/3 of a cubic foot at the surface (twice the volume as at 33 feet). So that would be about 0.66 cubic feet of air at the surface. At 66 feet it is 1/3 of its original volume, or 0.33 x 0.66 cubic foot, or 0.22 cubic foot of air. If one cubic foot of air is 62.4 pounds of buoyancy (64 pounds per cubic foot in sea water), then 62.4 pounds x 0.22 = 13.6 pounds of buoyancy. I have to add about six pounds of buoyancy to my BC. I'd still have to add if I went down to 99 feet too, not because of the loss of wet suit buoyancy, but because I was using air to compensate in a soft BC.

    The Dacor Nautilus CVS doesn't have that problem, and once the trim is set at 33 feet, it can be ignored with further depth changes. I have two of these units and have dived them. They are very nice BCs. They do not leak from the regulator (it takes about 12 inches to activate the regulator, a pressure differential of 0.445 pisg). The regulator does not free flow because it is feeding the air into the CVS, and not open to the water outside. This is the same principal Cousteau used to pressurize his camera housings in the 1950s (see The Silent World, the first photo after page 114, a black and white photo of Cousteau with his camera housing). The Dacor Nautilus is listed in the Dive Dacor 1977 Retail Price List as $199. The four pound lead weight was $8, a weight tract filler at $2, and a carrying bag at $32. I have a copy of the Nautilus Constant Volume System Instructor Manual, and it contains parts diagrams which I'll copy in the next few days. The system was well thought out, and does work. In my opinion, they did themselves a disfavor by picturing it with a shorty wet suit; it is best with the full Farmer John wet suit.
    [​IMG]
    [​IMG]

    SeaRat
     
    Last edited: Oct 12, 2011

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