<html><head></head><body><div style="color:#000; background-color:#fff; font-family:times new roman, new york, times, serif;font-size:16px"><div id="yui_3_16_0_ym19_1_1549403565996_9206" dir="ltr"><span id="yui_3_16_0_ym19_1_1549403565996_9300">I believe it is because air molecules are not dense enough to carry the ultrasonic wave and so it is reflected back as if it were the "bottom". No different than an ultrasound on the human body, it requires a "grease" between the skin and ultrasound wand so there are no air gaps.</span></div><div id="yui_3_16_0_ym19_1_1549403565996_9206" dir="ltr"><span><br></span></div><div id="yui_3_16_0_ym19_1_1549403565996_9206" dir="ltr"><span id="yui_3_16_0_ym19_1_1549403565996_10884">Fiberglass is dense enough to pass the ultrasonic wave but there can't be any air bubbles in the area of the transducer.</span></div><div id="yui_3_16_0_ym19_1_1549403565996_9206" dir="ltr"><span>See </span><a href="http://www.raymarine.com/view/?id=199">http://www.raymarine.com/view/?id=199</a></div><div class="qtdSeparateBR" id="yui_3_16_0_ym19_1_1549403565996_9218"><br><br></div><div class="yahoo_quoted" id="yui_3_16_0_ym19_1_1549403565996_9213" style="display: block;"> <div style="font-family: times new roman, new york, times, serif; font-size: 16px;" id="yui_3_16_0_ym19_1_1549403565996_9212"> <div style="font-family: HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif; font-size: 16px;" id="yui_3_16_0_ym19_1_1549403565996_9211"> <div dir="ltr" id="yui_3_16_0_ym19_1_1549403565996_9210"> <font size="2" face="Arial" id="yui_3_16_0_ym19_1_1549403565996_10728"> <hr size="1"> <b><span style="font-weight:bold;">From:</span></b> hank pronk via Personal_Submersibles <personal_submersibles@psubs.org><br> <b><span style="font-weight: bold;">To:</span></b> Jon Wallace via Personal_Submersibles <personal_submersibles@psubs.org> <br> <b><span style="font-weight: bold;">Sent:</span></b> Tuesday, February 5, 2019 2:17 PM<br> <b><span style="font-weight: bold;">Subject:</span></b> Re: [PSUBS-MAILIST] Blue Robotics Sonar<br> </font> </div> <div class="y_msg_container" id="yui_3_16_0_ym19_1_1549403565996_10913"><br><div id="yiv7265741758"><div id="yui_3_16_0_ym19_1_1549403565996_10916"><div class="yiv7265741758ydpbd9c778fyahoo-style-wrap" style="font-family:Helvetica Neue, Helvetica, Arial, sans-serif;font-size:13px;" id="yui_3_16_0_ym19_1_1549403565996_10915"><div></div>
<div id="yui_3_16_0_ym19_1_1549403565996_10914">It just doesn't make sense to me? I thought the sound had to hit a more dense material than air to bounce back. it is great if it works- I will have to give it a try when the ice melts.</div><div>Hank</div><div><br clear="none"></div>
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On Tuesday, February 5, 2019, 8:46:00 AM MST, Jon Wallace via Personal_Submersibles <personal_submersibles@psubs.org> wrote:
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<div id="yui_3_16_0_ym19_1_1549403565996_10921"><div id="yiv7265741758"><div id="yui_3_16_0_ym19_1_1549403565996_10920"><div style="color:#000;background-color:#fff;font-family:times new roman, new york, times, serif;font-size:16px;" id="yui_3_16_0_ym19_1_1549403565996_10919"><div><span>Pretty sure the beam reflects off the water surface.</span></div><div class="yiv7265741758qtdSeparateBR" id="yiv7265741758yui_3_16_0_ym19_1_1549334288735_25596"><br clear="none"><br clear="none"></div><div class="yiv7265741758yahoo_quoted" id="yiv7265741758yui_3_16_0_ym19_1_1549334288735_25600" style="display:block;"> <div id="yiv7265741758yui_3_16_0_ym19_1_1549334288735_25599" style="font-family:times new roman, new york, times, serif;font-size:16px;"> <div id="yiv7265741758yui_3_16_0_ym19_1_1549334288735_25598" style="font-family:HelveticaNeue, Helvetica Neue, Helvetica, Arial, Lucida Grande, sans-serif;font-size:16px;"> <div class="yiv7265741758yqt8761248782" id="yiv7265741758yqt30868"><div dir="ltr" id="yiv7265741758yui_3_16_0_ym19_1_1549334288735_25597"> <font id="yiv7265741758yui_3_16_0_ym19_1_1549334288735_25602" size="2" face="Arial"> </font><hr size="1"> <b><span style="font-weight:bold;">From:</span></b> hank pronk via Personal_Submersibles <personal_submersibles@psubs.org><br clear="none"> <b><span style="font-weight:bold;">To:</span></b> Brian Hughes via Personal_Submersibles <personal_submersibles@psubs.org> <br clear="none"> <b><span style="font-weight:bold;">Sent:</span></b> Friday, February 1, 2019 10:54 AM<br clear="none"> <b><span style="font-weight:bold;">Subject:</span></b> Re: [PSUBS-MAILIST] Blue Robotics Sonar<br clear="none"> </div> <div class="yiv7265741758y_msg_container" id="yiv7265741758yui_3_16_0_ym19_1_1549334288735_25604"><br clear="none"><div id="yiv7265741758"><div id="yiv7265741758yui_3_16_0_ym19_1_1549334288735_25608"><div class="yiv7265741758ydp7b7eb433yahoo-style-wrap" id="yiv7265741758yui_3_16_0_ym19_1_1549334288735_25607" style="font-family:Helvetica Neue, Helvetica, Arial, sans-serif;font-size:13px;"><div></div>
<div id="yiv7265741758yui_3_16_0_ym19_1_1549334288735_25606">Brian, </div><div id="yiv7265741758yui_3_16_0_ym19_1_1549334288735_25610">Have you tested the Hummingbird pointing strait up? I didn't think that would work because there is nothing for it to bounce back against.</div><div id="yiv7265741758yui_3_16_0_ym19_1_1549334288735_25612">Hank</div><div id="yiv7265741758yui_3_16_0_ym19_1_1549334288735_25614"><br clear="none"></div>
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On Friday, February 1, 2019, 7:44:42 AM MST, Brian Hughes via Personal_Submersibles <personal_submersibles@psubs.org> wrote:
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In the original configuration of Harold, Maynard attached a transducer to the front of the starboard side thruster. I assume he did so as a way to easily shift direction, up to get depth bouncing off surface, spin the thruster down for depth, forward for collision
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Here's the upgrade:<br clear="none">
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1) transducer always pointed up for a Humminbird HDR 650. Basically a digital depth gauge. Small and accurate. Works well.<br clear="none">
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2) Raymarine Dragonfly 4 Pro aimed down to give depth below and detailed image of what's under me. Amazing little CHIRP sounder.<br clear="none">
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3) still debating on what to aim forward. Currently have an Interphase forward scanning sonar, but not real impressed with it. Older technology that works. Sort of.<br clear="none">
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Brian<br clear="none">
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Get <a rel="nofollow" shape="rect" target="_blank" href="https://aka.ms/ghei36">Outlook for Android</a></div>
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