Author Topic: Plastic fish report  (Read 9063 times)

0 Members and 1 Guest are viewing this topic.

Offline Dale

  • Jr. Member
  • **
  • Joined: Feb 2010
  • Location: Melbourne Australia
  • Posts: 27
    • Parks Victoria
  • Unit(s): (4 x) 997c
Plastic fish report
« on: December 17, 2010, 07:52:03 PM »
G'day all,

As a lurker on the forum, I thought that having built and deployed a fish that I should report some results.

I've put up an initial still and a short video clip of the fish on Flickr

http://www.flickr.com/photos/miniop/sets/72157625620469360/

I'll post more on this thread as time permits.

Dale


Offline Dale

  • Jr. Member
  • **
  • Joined: Feb 2010
  • Location: Melbourne Australia
  • Posts: 27
    • Parks Victoria
  • Unit(s): (4 x) 997c
Re: Plastic fish report
« Reply #1 on: December 18, 2010, 01:21:29 AM »
Now I know how to embed video into a post...

Towfish & Video


This is the fish  on shallow tow, with a splashcam video camera in front. The reason for the shallow deployment is obvious!  I shot this clip using the rather brutal method of taping my offsiders camera to a boathook and shoving it over the side!
« Last Edit: December 18, 2010, 01:25:15 AM by Dale »

Offline Del

  • Jr. Member
  • **
  • Joined: Nov 2010
  • Location: Hamburg
  • Posts: 76
  • Unit(s): 1197 SI
Re: Plastic fish report
« Reply #2 on: December 18, 2010, 04:59:29 AM »
Hey, that looks pretty nice!

Is the transducer already mounted to the fish ? I just didnt see a cable going down. Any further informations and ofc some more pics welcome !



greetings,
Del

Offline Humminbird_Greg

  • Humminbird Helper
  • Humminbird Staff
  • *
  • Joined: Mar 2009
  • Location: Eufaula, AL.
  • Posts: 6546
  • I help because I can
    • Humminbird Web Site
Re: Plastic fish report
« Reply #3 on: December 18, 2010, 08:51:20 AM »
I could not see the transducer either.  It also looks like that is a piece of PVC without a nose on it.  Can you confirm this and maybe post some build pics and a picklist when you get it all working?

Beautiful looking beach area in the background!
Greg Walters at Humminbird
gwalters@johnsonoutdoors.com

Offline sonar2000

  • Chief
  • Global Moderator
  • *
  • Joined: May 2009
  • Location: Kerr Lake NC
  • Posts: 5970
  • It is not lost ...it has been misplaced.
  • Unit(s): (1) 1197 (1) 1198
  • Software: 6.6
  • Accessories: Tow Fish
Re: Plastic fish report
« Reply #4 on: December 18, 2010, 04:03:10 PM »
If you mounted a transducer show some pictures.  Also some comments on how well the fish tows and how stable it is. Do you get any side to side sway.
Chuck

Offline Dale

  • Jr. Member
  • **
  • Joined: Feb 2010
  • Location: Melbourne Australia
  • Posts: 27
    • Parks Victoria
  • Unit(s): (4 x) 997c
Re: Plastic fish report
« Reply #5 on: December 18, 2010, 04:33:10 PM »
Sorry all, been busy.

This is the first fish I have built, having some experience in using high end fish (Klein etc) It was whipped up out of available materials.

Stats:

PVC tube 50mm dia
Length 1200mm
Fins (4)   250mm x 130mm
aluminium channel
two 500g bar type lead diving weights
one squished 500ml plastic drink bottle
cable ties

Construction:

Fins and tow point welded to tube.
Transducer mount riveted to backing plate inside
Tow cable is waterski rope with the transducer cable threaded inside. I used three cable ties to connect the fish to the rope, after I carefully placed the shackle on the gunwhale minutes before... and I can thus confirm that the Humminbird will not resolve a shackle on the seabed.
The fish construction was finished enroute to our test grounds.

Experience:

We did just over four hours of towing with the fish, and 40 min with fish and video. Conditions where not perfect, with tide runs of 2-4Kn.

Fully weighted (1kg lead in the nose) and a nose cap, the fish tows well, in this case with almost no layback. We needed to be able to sight the fish as the area we where working had depth ranges of .5m to 14m. We removed 500g and retested.  I rammed a 500ml drink bottle down the tube to get some more buoyancy and that achieved the desired result. The nose cap was removed to make sure the nose section flooded.

The video was shot with us towing cross tide on a transect. The fish can be seen walking around slightly. We think that this is current, wake and design induced.

More sea trials are to take place very soon. We will move the tow point forward, and test in a variety of waters. (without current and with a shackle)


ila_rendered
Mount for transducer

ila_rendered
Welded fins

ila_rendered
The fish and a foot.

ila_rendered
End view


I'll post up a clipped portion of the mosiac we produced next. With our next tests we will run the splashcam pointing aft  and get some video of the fish running in a variety of configurations. 
« Last Edit: December 18, 2010, 04:45:34 PM by Dale »

Offline Dale

  • Jr. Member
  • **
  • Joined: Feb 2010
  • Location: Melbourne Australia
  • Posts: 27
    • Parks Victoria
  • Unit(s): (4 x) 997c
Re: Plastic fish report
« Reply #6 on: December 18, 2010, 05:05:59 PM »
And the results!

The data was processed using DrDepth. The image below has a 10m grid overlaid. The aim here is to collect data to habitat map large areas rather than find fish, or gold!


Offline Dale

  • Jr. Member
  • **
  • Joined: Feb 2010
  • Location: Melbourne Australia
  • Posts: 27
    • Parks Victoria
  • Unit(s): (4 x) 997c
Re: Plastic fish report
« Reply #7 on: December 18, 2010, 07:06:01 PM »
I could not see the transducer either.  It also looks like that is a piece of PVC without a nose on it.  Can you confirm this and maybe post some build pics and a picklist when you get it all working?

Beautiful looking beach area in the background!


The beach area in the background is beautiful! Every couple of years or so the bomb disposal crews come out and blow up UXBs as they show up on the same beach. The place is littered with shipwrecks just to add more interest.

The link below is well worth exploring, it shows the area we are working in. As an aside we Aussies have something the rest of the world does not, NearMap.  Have a good look at the point to the west and use the time buttons to reveal a shipwreck.

http://www.nearmap.com/?ll=-38.30653,144.662996&z=19&t=k&nmd=20101028

Offline Del

  • Jr. Member
  • **
  • Joined: Nov 2010
  • Location: Hamburg
  • Posts: 76
  • Unit(s): 1197 SI
Re: Plastic fish report
« Reply #8 on: December 19, 2010, 12:58:37 PM »
Hey Dale,
you've got some verry nice results there and your towfish looks quite simple. Nice one, thanks for sharing.


Am I correct that your transducer cable is inside the rope ? Looks like this on the pics..


Thanks,
Del

Offline Dale

  • Jr. Member
  • **
  • Joined: Feb 2010
  • Location: Melbourne Australia
  • Posts: 27
    • Parks Victoria
  • Unit(s): (4 x) 997c
Re: Plastic fish report
« Reply #9 on: December 19, 2010, 04:57:14 PM »
Del,
I rove the the transducer cable inside the waterski rope.  Topside I have the plug just protruding from the rope, and use the tail to cleat.  From what I can see so far, the transducer cable is not taking much of the tow load. I'll post up some images of both ends.

D.

Offline abraquelebout

  • volunteer rescue diver, surfer, publicist
  • Sr. Member
  • ****
  • Joined: Apr 2010
  • Location: france
  • Posts: 263
  • Unit(s): 898, 1198, helix G2
  • Software: deep,,drdepht,reef.
  • Accessories: towfish lowbird /LSS2-hdsi, 60mcable
Re: Plastic fish report
« Reply #10 on: December 29, 2010, 12:48:16 PM »
good job, congratulation
do you only want to use humminbird tranducer cable, or other for mutch longer and depht ?
 

Offline Dale

  • Jr. Member
  • **
  • Joined: Feb 2010
  • Location: Melbourne Australia
  • Posts: 27
    • Parks Victoria
  • Unit(s): (4 x) 997c
Re: Plastic fish report
« Reply #11 on: December 31, 2010, 05:53:47 AM »
I'd use a longer cable for deeper depths, down to 120m. By that stage, we would be seriously considering using a more professional grade system and fish.

My main interest is developing systems that can be used by volunteers and staff to map change in waters less than 40m deep. We also have a bunch of wrecks, both recent and older, that we wish to obtain some data.

We will be testing deeper deployments using the ski rope  in the new year. From what I've seen so far, the rope does not bind to the cable, so that the tow load is only on the ski rope.

Today would have been a good day to be out on the water, it hit 41 degrees C here!

Offline Jolly Roger

  • Hero Member
  • *****
  • Joined: Mar 2009
  • Location: Germany, Lake Constance
  • Posts: 801
  • HB Addicted
  • Unit(s): 998Cx SI
  • Software: latest (mostly)
  • Accessories: AS GR50, custom towfish and: A boat!!
Re: Plastic fish report
« Reply #12 on: December 31, 2010, 11:58:09 AM »
Today would have been a good day to be out on the water, it hit 41 degrees C here!

Hm, that makes 41 degrees more then here  :-[

Happy New Year!!

Harry
YES,......
WE SCAN!

Offline Dale

  • Jr. Member
  • **
  • Joined: Feb 2010
  • Location: Melbourne Australia
  • Posts: 27
    • Parks Victoria
  • Unit(s): (4 x) 997c
Re: Plastic fish report
« Reply #13 on: January 01, 2011, 04:51:45 AM »
Happy New Year to you all as well. Snow and ice in the amounts we see on the news in Europe and Scandinavia are not things we consider when planning side scan missions!!

Offline Dale

  • Jr. Member
  • **
  • Joined: Feb 2010
  • Location: Melbourne Australia
  • Posts: 27
    • Parks Victoria
  • Unit(s): (4 x) 997c
Re: Plastic fish report
« Reply #14 on: January 19, 2011, 07:34:00 PM »
As part of of a habitat mapping project we have just returned from three days of trialling our fish, and our mobile topside unit in three different places.

We used a 14ft rigid hull inflatable (RIB) powered by a small two stroke outboard. Two of the sites consisted of tidal mudflats, with deeper channels.  The third was a combination of rocky reef shelving to sandy flats.

The fish was towed at depths of around 1m or less. We quickly learned that we could run with swath widths of 50m a side in water depths of 2m. As the mudflats are, well, flat, clear returns from objects 40 -50m off the vessel track could be seen.  We planned our runs to cross the channels at 90deg, after initial tests showed trying to follow 2m wide channels using only sidescan was very difficult.

The vibration from the two stroke outboard was transmitted through the hull, and the buoyancy tubes to an extent that it could be clearly felt and seen! Holding the cable against any part of the hull transmitted that vibration to the fish. It thus became simple to use a leg and an arm to hold the cable and fish away from the boat.

As the fish was on a very short cable run (less than two metres) we could observe its tow characteristics. We noted that if held to short, the fish would roll, leaving the transponder with a fixed roll angle of around 10deg. By just letting out another metre, the fish would roll back to vertical.

Some detail images of the fish:

ila_rendered

Cable join detail.

ila_rendered

Nose (open as run) with nose weights





Offline Dale

  • Jr. Member
  • **
  • Joined: Feb 2010
  • Location: Melbourne Australia
  • Posts: 27
    • Parks Victoria
  • Unit(s): (4 x) 997c
Re: Plastic fish report
« Reply #15 on: January 19, 2011, 07:36:32 PM »
End view of nose with first weight installed.

ila_rendered

We ran the fish with no nose cap for about ten hours, at depths from 2m down to about 6m with no signs of pitch, roll or yaw (apart from that noted above)

Offline RGecy

  • Administrator
  • *
  • Joined: Mar 2009
  • Location: Beaufort, SC
  • Posts: 1981
    • SideImagingSoft.com
  • Unit(s): 1197c SI, 997c SI & 785c2
  • Software: 4.950 & 4.510
  • Accessories: Interlink & GRHA
Re: Plastic fish report
« Reply #16 on: January 19, 2011, 08:56:39 PM »
Dale,

The fish looks great.  Harry and I were just talking about the open ended main tube on the fish.  Looks like it flies great. 

Look forward to some more images.

Robert
Humminbird Guru and Forum Administrator

Offline Jolly Roger

  • Hero Member
  • *****
  • Joined: Mar 2009
  • Location: Germany, Lake Constance
  • Posts: 801
  • HB Addicted
  • Unit(s): 998Cx SI
  • Software: latest (mostly)
  • Accessories: AS GR50, custom towfish and: A boat!!
Re: Plastic fish report
« Reply #17 on: January 20, 2011, 05:53:32 PM »
Good to hear that Dale!

I think the longer the fish, the more stable it will be. Then there even might be no fins needed.

Regards and thanks for sharing Dale

Harry
YES,......
WE SCAN!


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo

 

Related Topics

  Subject / Started by Replies Last post
0 Replies
2413 Views
Last post May 05, 2009, 07:30:42 AM
by RGecy
0 Replies
2429 Views
Last post May 21, 2009, 11:18:39 PM
by RGecy
2 Replies
5493 Views
Last post July 30, 2011, 02:41:46 PM
by sonar2000
0 Replies
1663 Views
Last post May 24, 2010, 06:49:21 PM
by stillbear
12 Replies
6612 Views
Last post April 29, 2015, 12:52:04 PM
by ITGEEK
6 Replies
2901 Views
Last post September 27, 2012, 12:45:20 AM
by Roddy
7 Replies
3214 Views
Last post June 02, 2015, 08:00:03 AM
by ITGEEK
3 Replies
473 Views
Last post October 14, 2020, 09:22:46 PM
by rnvinc


anything
SimplePortal 2.3.3 © 2008-2010, SimplePortal