Results 1 to 12 of 12

Thread: In hull transducer and graphite bottom

  1. #1
    Join Date
    Dec 2011
    Posts
    112

    Default In hull transducer and graphite bottom

    Would an in hull transducer be negatively affected by a bottom coated with graphite laden epoxy? Being a sonar signal I'd think not, but I'm no expert.

    Thanks in advance,
    Bob

  2. #2
    Join Date
    May 2012
    Location
    UK. Cornwall, Suffolk.
    Posts
    4,519

    Default Re: In hull transducer and graphite bottom

    In hull, ie shooting through the hull? Yes quite possibly.

    Ultrasonic beams are affected by attenuation (degradation of the waves) through scatter, beam spread, reflection, and absortion (from elasticity of the mediums' particles). Depth sounding transducers, as with all transducers, need a good coupling to their medium, this is why for medical ultrasound a gel is used, so air, which is terrible at transmitting sound, is eliminated.

    A through hull transducer is directly coupled to the water, so it can focus it's beam and only have to deal with it's own beam spread and absorption, as is normal in deep water. When a beam exits a transducer, the beam is chaotic for a certain given distance (according to frequency and diameter of the excited element), but this chaotic beam, called the 'near field', eventually sorts itself out into a focal point, and then continues diverging beyond that until the energy eventually dissipates. I imagine the scatter effect from graphite particles in the near field will affect the beam by elongating the focal point distance, never allowing it to focus properly, or at least as it was intended, and attenuate the signal such that you will get a weak return signal.

    Shooting through the hull, made of spongey wood, paint, filler, and graphite particles etc, all of which will absorb, scatter and spread the beam in the near field, is always less than optimal; is there no way to put it where it will give the best results, straight into water? If you absolutely have to have it shooting through through your hull, use a lower frequency transducer, which will have more penetrative power, but be prepared for a less sensitive return signal, where you might not be able to tell what the bottom is made of, and will miss some detail.

    I am not a marine sonar expert, but an ultrasound tech.

    Hope this helps.

  3. #3
    Join Date
    Mar 2007
    Location
    East Quogue,NY
    Posts
    16,248

    Default Re: In hull transducer and graphite bottom

    In practical terms it will work, provided there are no air bubbles or delamination (air spaces) in the laminate. Sonar does not work through air. As Lupossonic states, signal strength will be degraded, but usually not be enough so that it wont work. If its for a fish-finder, you want get quite the detail and it may not read quite as deep. But its will work, and if its just for a digital depth display, you'll not notice any difference in performance.

    Before you commit to a location, test it first, by smearing some grease or vaseline on the 'ducer and sticking it in place. Connect to the sounder or display. If it works, great; if not, you probably found a void/ air bubbles try a different location. Once you find a good spot, glue it down with slow cure epoxy that doesn't create exothermic bubbles ( air again) during cure.

    Wood or plywood cores are always hit-or-miss as to whether the air in the cells will stop the signal from transmitting. So test before you glue in place

    I have installed many shoot-through transducers, and currently run two on my fiberglass powerboat.

    Kevin
    Last edited by Breakaway; 05-19-2016 at 05:41 PM.
    There are two kinds of boaters: those who have run aground, and those who lie about it.

  4. #4
    Join Date
    Nov 2011
    Posts
    5,606

    Default Re: In hull transducer and graphite bottom

    I believe they work better through glass hulls than through wood hulls.

    On my small boats I mount the transducer on the end of a shaft that can slide up and down through guides on the transom. A set screw (plastic knob bolt) holds it in place.

  5. #5
    Join Date
    Jun 2000
    Location
    Madison Wisconsin
    Posts
    9,090

    Default Re: In hull transducer and graphite bottom

    The ladies at Lowrance once told me that the best goo for testing was Dipity-Do! Unfortunately, you have to be fairly old like some of us to even know what Dipity-Do is, but it's an early brand of hair gel. After the test, you can even give yourself a duck-tail with what's left over, hop in your 55 Chevy and go to the Steak and Shake for a burger.

  6. #6
    Join Date
    Dec 2011
    Posts
    112

    Default Re: In hull transducer and graphite bottom

    Thanks guys for the responses. I've made no decisions yet, but am weighing my options. I'd prefer to use an in hull transducer and only need it for depth sounding, not for fishing. The hull (clc pocketship) has a glassed 1/4" plywood bottom. I've read that in hull transducers often work good enough through thin plywood. I'd like to give it a try, I think.

  7. #7
    Join Date
    Dec 1999
    Location
    Oriental, NC USA
    Posts
    4,731

    Default Re: In hull transducer and graphite bottom

    Most of us are only interested in knowing the depth in shallow areas and not in 1000 foot depths where attenuation of the signal could be a problem. Some attenuation of the signal is usually of no consequence to us. Your transducer will work OK through quality 1/4 ply and the graphite will not keep it from giving good results. If you attempt to measure electrical conductivity in epoxy that has graphite powder in it, you will find that it is relatively non conductive. Anyway its not a very good shield to sound at all. Mount the transducer with silicone or similar solid (no air) and it will be fine.

    If you need optimum results you can grind out a hollow on the inside and fill with glass/epoxy before mounting the transducer. I have done this as well as cutting a hole in thick plywood and filling the hole with epoxy/glass. Both work fine, even in deeper water. Main thing is to make sure there is no air between the transducer and the water.
    Last edited by Tom Lathrop; 05-19-2016 at 09:00 PM.
    Tom L

  8. #8
    Join Date
    Dec 2012
    Location
    High plains drifter
    Posts
    8,264

    Default Re: In hull transducer and graphite bottom

    Im sure that any contamination on the transducer face retards its efficiency. If you are using your transducer for scientific work , this could be a problem.

    for normal work its insignificant.

    I have a backup depth finder and transducer. The transducer now has twenty three years worth of antifouling paint buildup on its face. This is A very thick film of paint .

    Its work just fine

  9. #9
    Join Date
    Dec 2011
    Posts
    112

    Default Re: In hull transducer and graphite bottom

    Just thought I'd follow up. Yesterday, I epoxied a transducer to the inside of my plywood boat. It works fine. I tested it first by putting it in a plastic bag filled with water. Neither the glassed 1/4" plywood hull nor the graphite/epoxy bottom finish proved to be an issue. It's a Lowrance transducer designed primarily as a transom mount device with the option to use as an in hull (in a non-wood hull). I installed it while on the water so that I could see it working as I pressed it into the epoxy. Anyway...it worked.
    Thanks all for the advice.

    P.S. My research found that some people have had success mounting their transducers in melted toilet wax.

  10. #10
    Join Date
    Jan 2009
    Location
    se pa (Bristol PA)
    Posts
    3,104

    Default Re: In hull transducer and graphite bottom

    Having used if a few times.. I can say graphite bottoms aren't worth the effort. Black it is.. skid over rocks and sand.. not really any better then paint.
    Denise, Bristol PA, Oday30, Anchor Yacht Club, On tidal Delaware River. my current project; http://forum.woodenboat.com/showthre...0-Ducker-Resto

  11. #11
    Join Date
    Apr 1999
    Location
    Now, there's a long story...
    Posts
    1,562

    Default Re: In hull transducer and graphite bottom

    Quote Originally Posted by Todd Bradshaw View Post
    After the test, you can even give yourself a duck-tail with what's left over, hop in your 55 Chevy and go to the Steak and Shake for a burger.
    I thought I was supposed to take the Chevy to the levee...
    Heute ist so ein schöne Tag...

  12. #12
    Join Date
    Jun 2005
    Location
    Seymour, TN
    Posts
    10,231

    Default Re: In hull transducer and graphite bottom

    Quote Originally Posted by Todd Bradshaw View Post
    The ladies at Lowrance once told me that the best goo for testing was Dipity-Do! Unfortunately, you have to be fairly old like some of us to even know what Dipity-Do is, but it's an early brand of hair gel. After the test, you can even give yourself a duck-tail with what's left over, hop in your 55 Chevy and go to the Steak and Shake for a burger.
    Got a can of this when it first came out and was fascinated by the way it "rang" when you tapped the can top while holding the can to your skull... (Yeh, I was a weird kid)

    The "Thun-n-g" sound... MY sound of bygone youth.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •