[PSUBS-MAILIST] Depth Sounder

[Alan James via Personal_Submersibles]

 Jon, What I had proposed was making a view port that is maybe 1" in diameter & securing a 1/2" thick disk in this. The minimum diameter of the disk or port it sits in would be determined by the beam angle of the sounder. We may get away with a thinner disk than 1/2".This can all be tested off a boat! Hang off the back of a boat holding the shoot-through-hull transducer against a piece of fibreglass. You could glue a 1" metal ring to the back of the fibreglass as a simulation of the fibreglass retaining port, to check it is not interfering with the transducer signal. Would be good to see the minimum sized port you could get away with! You may even be able to test this on a lake from a jetty by angling the transducer across the lake. You would have to lug a battery etc there though! Alan

    On Tuesday, March 30, 2021, 02:38:51 AM GMT+13, Jon Wallace via Personal_Submersibles <personal_submersibles at psubs.org> wrote:  
 
  Alan, just terminology.  When someone says "hull" I think pressure hull, not a viewport or a specialty port like the fiberglass one you describe.  By the way, how are you calculating failure on the fiberglass "port"?  Airmar told me they think 1/2 inch is limit for shooting through plexiglas but that was a guess on their part.  Regardless, I don't have a bottom viewport to shoot through and probably won't add one to the K-600.  I was considering a 1-ATM housing of some kind to hang outside, but Cliff had no problem taking Airmar DST800 to 400 feet without any modification so I'd much prefer that route.
I've been concentrating on finding a NMEA-0183 transducer that can sound at 600-1000 feet reliably and that is proving to be difficult.  Cliff's DST800 is suppose to sound up to 300 feet but he has found it is limited to about 170 feet.  I talked to an Airmar rep at length last week and he confirmed that the sounding ratings are not empirical, as well as stating that feedback from actual installations fall in line with Cliff's observations.  The issue, as always when acoustics are involved, is water density, quality, blah, blah, blah.  So seems like 50% effectiveness of stated sounding rating could be a realistic expectation.
For some of the deep diving subs we are seeing pop up, a depth sounding transducer that can reach max depth is starting to sound like a luxury.


    On Sunday, March 28, 2021, 05:05:57 PM EDT, Alan James via Personal_Submersibles <personal_submersibles at psubs.org> wrote:  
 
  Jon, No they can't shoot through steel only fibreglass. I had suggested making a tiny view port witha fibreglass disk in it to attach the transducer to from the inside of the hull. Not sure whether Hank is doing this or just fibreglassing the whole transducer and putting it in the water. I was told by a rep that the shoot - through-Hull transducers can shoot through up to 1/2". I did hear 1"from another source. Just important not to have any air gap or bubbles! Alan

   
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