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TOPIC: Stern mount compared to bow mount

Stern mount compared to bow mount 6 years 3 months ago #5582

  • hakan
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Hi,
I've been testing different setups to get good range and low noise with the LSS-2 sensor. My first test was to use dual LSS-2 sensors and an Y-cable but that was a disaster since the data processing on the Lowrance assumed that all 3 transducers where at the original position in the LSS-2 sensor.

My next test was to use a bow mount instead. That was a success and I get better range, less noise and can survey at 5-6 knots without any notisable decrease in quality. The next step would be to make the pole tear drop shaped so it travels smoother through the water.



Stern mount

Bow mount








/hakan
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Stern mount compared to bow mount 6 years 3 months ago #5583

  • Luke
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Nice :-)

Can you please show me images with more details ?

How did you build the mounting bracket for the LSS2 ?
Luke
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Stern mount compared to bow mount 6 years 3 months ago #5584

  • hakan
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Hi,
it's an aluminum tube with 30 mm outer diameter and the inner diameter is just enough to get the connector through (with some minimal sanding on the connector).







/hakan
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Stern mount compared to bow mount 6 years 3 months ago #5589

  • JK4U
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  • Because it must be scanned...!
Great mount you have created there. Impressive.
May I ask why you don't operate a small towfish with those great skills? The supplied cable would be more than enough for a 2m deep tow, which would really smooth out the heave and steering offsets.
Bow mounts are so uncommon because of the great offset both from heave and from minimal steering corrections, since most boats don't run perfectly straight.
Additionally, corners can be tracked much, much more smoothly, since the fish will follow the boat in a soft and predictable arch.
I attached a picture of my latest mod to my small towfish, the mini ray. It's enough for waves up to 1.5m, since I elongated the cables to 10m,so it tracks at around 3m under the surface at 3.5 kph and gives me a range of around 60-80m to both sides in 15-20m of water. Running both a LSS2 and a P66 on the fish.
Attachments:
LOWRANCE HDS 7 Gen2 Touch.
Raymarine Dragonfly
100m SI&DI HDS Towfish.
8m Rayfish (SI, DI & HD Sonar)
Last Edit: 6 years 3 months ago by JK4U.
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Stern mount compared to bow mount 6 years 3 months ago #5599

  • hakan
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Thanks!
I focus on shallow water measurement and waves are seldom a problem for me in the archipelago here in Sweden. I towed fish would be tricky when you have depth between 2-5 meters and you make short runs with a lot of stop/turn/start. For long straight runs in deeper water the towed sonar is much better and as you say it removes the wave action and errors between heading and COG.

If you use heading and have the sonar fixed to the boat you can remove wind/current and other sources of error so you position objects correctly and makes the mosaic much better. I evaluated a test version of sonarwiever from Matt that used high resolution position and heading with 10Hz from a separate file instead of the low res data in the sl2 file, that gave us excellent data even in turns!

I was inspired by the setup we have at work on our small boat when I made this setup.
On that boat we have a bow mount with Swath sonar, sound speed measurement, depth measurement, MRU (for high speed heave, roll, pitch and yaw) and a forward looking sonar. On the pole we have a RTK GNSS receiver which gives us ±2 cm position in x,y,z with 10Hz.
We can survey in quite large waves and it will compensate for all the motion and produce smooth bathymetry.







Cheers
Hakan
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Stern mount compared to bow mount 6 years 3 months ago #5600

  • hakan
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I just bough a 50kHz transducer that I will attach aft of the LSS-2 so I get better bottom classification. I will test that in a week and hope to get a bit better penetration of the seabed than the stock 80kHz transducer.

/hakan
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Stern mount compared to bow mount 6 years 2 months ago #5829

  • hakan
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The 50kHz transducer actually managed to get some penetration in the top bottom sediments, more than I expected! I added the 50kHz transducer at the bow mount to get it out of the turbulense and also have it close to the sidescan to get good bottom tracking for the mosaic.



Here is the complete bow mount with a streamlined pole to get rid of some more noise.


Close up of the installation


The result in reefmaster where the penetration of the sea bed can be seen.

/hakan
Last Edit: 6 years 2 months ago by hakan.
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Stern mount compared to bow mount 6 years 2 months ago #5830

  • AnglingCharts
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Hakan,

I reckon I see about 1ft (30cms) through the silt in the area between the boats side and 20ft out in about 20ft of water. This has been confirmed on numerous occasions by video and subsequent survey. Its quite impressive for a relatively cheap bit of kit (compared to commercial equipment).

T
http://www.anglingcharts.com/

Mucking about in boats
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Stern mount compared to bow mount 6 years 3 weeks ago #6142

  • cootcraig
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hakan wrote:
I was inspired by the setup we have at work on our small boat when I made this setup.
On that boat we have a bow mount with Swath sonar, sound speed measurement, depth measurement, MRU (for high speed heave, roll, pitch and yaw) and a forward looking sonar. On the pole we have a RTK GNSS receiver which gives us ±2 cm position in x,y,z with 10Hz.
We can survey in quite large waves and it will compensate for all the motion and produce smooth bathymetry.

Wow. Thanks for posting this. I will be looking at your setup if I ever do an upgraded system.
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Stern mount compared to bow mount 6 years 3 weeks ago #6145

  • hermes
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..... Just mentioned that I was going to rig something up and test it in the other post! Looks like you already have something for me to copy :-) right, off to the welding workshop !
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Stern mount compared to bow mount 6 years 3 weeks ago #6146

  • hermes
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Just an after thought, but with a simple MRU in iPhones etc can it be used on top of the pole? is there any way of outputting pitch roll and heave? ..... Matt, RM with PRH corrections from an iPhone ?? A tad too ambitious perhaps :-)
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Stern mount compared to bow mount 6 years 3 weeks ago #6147

  • Matt
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Hi Hermes,
That is something we are already playing with :) In fact we are looking at the idea of logging all positional data independently of the sonar recording device; location and attitude (including heading). Some of this could indeed be recorded on a mobile phone or by using relatively inexpensive hardware, which could also open up the possibility of recording raw GPS data that can later be post-processed to greatly improve accuracy.
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