[PSUBS-MAILIST] depth sonar

Thu Jul 19 17:23:01 EDT 2018

Hank,
Thinking that you will know for sure if it operates the same
under pressure by diving down.
In cave diving they have a narrow beam as well as a wide beam for
spotting things like cave walls off in he distance. If you had a narrow
beam pointed down it may be a good backup in case the sonar
failed.
Alan

Sent from my iPad

> On 20/07/2018, at 8:40 AM, hank pronk via Personal_Submersibles <personal_submersibles at psubs.org> wrote:
> 
> 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-sensing
> Deep sea power & light put out a dual laser beam device but nit for
> measurement.
> Alan
> 
> Sent from my iPad
> 
>> 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 through
>> your viewport & additionally one straight out front for collision avoidance.
>> You could buy something with a 20 meter range & could set an alarm at
>> a certain distance.
>> I am not sure how this would work in murky conditions! Be easy to find
>> out by diving.
>> If the reading diminished with murkiness then perhaps have an additional
>> range finder pointed at an object on the sub exactly 1 metre away, & use
>> it's readings to continually calibrate the main laser.
>> There are a few people on this site that could easily do that with arduino.
>> Alan
>> 
>> 
>> 
>> 
>> Sent from my iPad
>> 
>>> 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 bag
>> of water on the bottom of your boats fibreglass hull & check
>> the 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
>> 
>> Sent from my iPad
>> 
>>> 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 to
>>> the acrylic unless you put the transducer in a bag full of water & had this
>>> forced 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
>>> 
>>> Sent from my iPad
>>> 
>>>> 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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