[PSUBS-MAILIST] depth sonar

Thu Jul 19 19:32:48 EDT 2018

 Brian,I am glad the meter made it safely.  The towel is a rental fee lol.  Hank    On Thursday, July 19, 2018, 5:04:27 PM MDT, Brian Cox via Personal_Submersibles <personal_submersibles at psubs.org> wrote:  

 My transducer in my sailboat is siliconed directly to the fiberglass.  When in Catalina harbor I was in the free anchorage area, which is only about 8 feet of water.  We had a minus tide of 1.4 when I was there, so at 3:45 in the morning I was listing about 10 degrees !  I looked at my depth sounder and it showed no blue, only various stratifications of red, orange and some other colors.  But prior to that when I was just barely touching it did show a stripe of blue.  So it seems to go through the fiberglass pretty well.  Finally made it back !   was stranded with no crew to get back, finally found someone.  Left at 9:30 in the evening and arrived at my harbor at 8:30 in the morning !   No headwind at night and no sunburn to deal with as well ! BTW  Hank,  Thanks for the dish towels ! Brian 

--- personal_submersibles at psubs.org wrote:

From: hank pronk via Personal_Submersibles <personal_submersibles at psubs.org>
To: Alan via Personal_Submersibles <personal_submersibles at psubs.org>
Subject: Re: [PSUBS-MAILIST] depth sonar
Date: Thu, 19 Jul 2018 20:40:23 +0000 (UTC)

 Alan,Intersting, but I just examined the transducer and it is potted solid.  I think it is possible to send one to 3000 feet.  I will pressure test one to 3000 feet before I get too  involved in an alternative solution.  Stay tuned......Hank
    On Thursday, July 19, 2018, 2:17:29 PM MDT, Alan via Personal_Submersibles <personal_submersibles at psubs.org> wrote:  

 Hank,did a bit more googling & blue laser is the way to go.Here's an article.https://electronics.stackexchange.com/questions/55804/underwater-distance-measurement-sensingDeep sea power & light put out a dual laser beam device but nit formeasurement.Alan

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On 20/07/2018, at 7:39 AM, hank pronk via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

 Alan,That is an interesting idea, hmmmm I am going to investigate that.Hank

    On Thursday, July 19, 2018, 1:21:53 PM MDT, Alan via Personal_Submersibles <personal_submersibles at psubs.org> wrote:  

 Hank, all,wonder if a laser distance sensor would work pointing down throughyour viewport & additionally one straight out front for collision avoidance.You could buy something with a 20 meter range & could set an alarm ata certain distance.I am not sure how this would work in murky conditions! Be easy to findout by diving.If the reading diminished with murkiness then perhaps have an additionalrange finder pointed at an object on the sub exactly 1 metre away, & useit's readings to continually calibrate the main laser.There are a few people on this site that could easily do that with arduino.Alan

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On 20/07/2018, at 6:27 AM, Alan via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

Hank,one trick I saw on a forum was to put the transducer in a bagof water on the bottom of your boats fibreglass hull & checkthe readings through the hull & then in the water.This eliminates any air gap between transducer & hull.This may be of benefit if you have a fibreglass boat!Be interested in any test results.Alan

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On 19/07/2018, at 10:40 PM, hank pronk via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

 Alan,Thanks' for the input, I like the sphere idea.  That could be made pretty easily.Jon, I was wondering the same thing, so I read a bunch of comments about transducer mounting.  There seems to be a lot of disagreement about what can work in terms of material.  I will have to test it out with acrylic for myself.  According to the acrylic calculator I can get away with 1\2 inch acrylic if it is 2 in dia.  I could make a housing with a acrylic bottom and even fill the housing with epoxy. 
Hank    On Wednesday, July 18, 2018, 8:54:28 PM MDT, Alan via Personal_Submersibles <personal_submersibles at psubs.org> wrote:  

 Jon, Hank,here's a bit of info pasted below.I am not sure about acrylic. You would have to attach the transducer tothe acrylic unless you put the transducer in a bag full of water & had thisforced against the acrylic. Again someone could try hanging the transducer in water while pushing it against a piece of acrylic.Alan
In-Hull Transducers

In-hull (a.k.a. shoot-through) transducers are epoxied directly to the inside of the hull. These are only used in fiberglass hulls. In-hulls will not work with wooden, aluminum, or steel hulls, or in foam sandwich/hulls that have air pockets. Any wood, metal, or foam reinforcement must be removed from the inside of the hull.

With an in-hull transducer, the signal is transmitted and received through the hull of the boat. As a result, there is considerable loss of sonar performance.

In other words, you won't be able to read as deep or detect fish as well with an in-hull transducer as with one that's transom mounted or thru-hull mounted.

Fiberglass hulls are often reinforced in places for added strength. These cored areas contain balsa wood or structural foam, which are poor sound conductors. The transducer will need to be located where the fiberglass is solid and there are no air bubbles trapped in the fiberglass resin. You'll also want to make sure that there is no coring, flotation material, or dead air space sandwiched between the inside skin and the outer skin of the hull.

Advantages

   - No holes drilled in hull
   - Excellent high speed performance
   - No obstructions in the water
   - Low maintenance

Disadvantages

   - Reduced maximuum depth reading
   - Reduced fish detection
   - Can only be used with fibreglass hulls

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On 19/07/2018, at 1:52 PM, Jon Wallace via Personal_Submersibles <personal_submersibles at psubs.org> wrote:

Can it shoot through acrylic?

      From: hank pronk via Personal_Submersibles <personal_submersibles at psubs.org>
 To: Personal Submersibles General Discussion <personal_submersibles at psubs.org> 
 Sent: Wednesday, July 18, 2018 6:55 PM
 Subject: [PSUBS-MAILIST] depth sonar

Hi all,I am looking for ideas on how to make a depth transducer survive to 3,000 feet.   I am thinking about a 1 atm housing with a fibreglass bottom that the transducer can shoot through. Alan, were you working on this idea?Hank_______________________________________________
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