Author Topic: Towfish  (Read 10204 times)

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Offline keizerh

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Towfish
« on: August 30, 2009, 01:52:24 PM »
It was a windy day, so I decided to clean up the yard and garage.

I found 3 feet of rain(drain)pipe 75mm
A clamp to fix a rainpipe to a wall
30 metres of double shielded low impedance SFTP CAT6 twisted networkcable.


A Sailkeg





Some hollow rope
ila_rendered


My tru-hull 262/455 transducer
Tools, glue and imagination

Hope something usefull comes out of it.

hendrik





Offline wizzo86

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Re: Towfish
« Reply #1 on: August 30, 2009, 03:42:56 PM »
Good luck with it hendrick....  I made one 3 years ago when i was trying to get a old lorance paper graph to work as a side scan. Was never able to make it work. I'm not thinking about dusting the fish off and mounting my 987 transducer on it. Made it out of pvc and turned a nose cone on a lathe out of wood. The fins are made of plexiglass and I painted it all yellow. It looks professional but the proof is in if i can get it to work. I made a front fin out of led to keep it level in the water. Will take a couple pictures of it and add them here.... This is a good thread you started. I'm sure there will be plenty of intrest.

Offline Humminbird_Greg

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Re: Towfish
« Reply #2 on: August 31, 2009, 03:25:38 PM »
Hendrik,
I’ve got a few pdf files of towfish that others have built and agreed to share info on.  Just send me a direct e-mail and I’ll e-mail the files back to you.

Greg Walters at Humminbird
gwalters@johnsonoutdoors.com

Offline keizerh

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Re: Towfish
« Reply #3 on: September 15, 2009, 03:10:09 PM »
It's is getting in shape.
Pulled 30 metres of wire trough te line.
Now I need a nosecone for the 3" pipe.
Anybody any ideas?

Hendrik

Offline Rickard

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Re: Towfish
« Reply #4 on: September 15, 2009, 04:14:54 PM »
Nice project!

I didn't know hollow rope existed. I use pvc-coated steel wire parallel with the cable but your arrangement looks simpler. How flexible is the rope? I think it must be pre-streched to avoid tension in the cable inside when the fish is towed at high speed or if you collide with something. I use the same type of cable and it works great. No crosstalk but the attenuation in 50 cable is clearly noticable.

At some point you have to make the fish heavy. Perhaps you could make the nose cone out of lead, molded or forged from sheet. I found pure 5 mm lead sheet to be very easy to hammer into any shape. A cone should be no problem and it's beneficial to put most of the mass at the front of the fish.

Regards,
Rickard

Offline keizerh

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Re: Towfish
« Reply #5 on: September 15, 2009, 04:42:33 PM »
Rickard,

The rope is beig used as towline for waterskie-ing.
It is 10 mm hollow on the inside.
Even when I put 100 Kg on it, there is no big stress on the wire.

At the boatend boat there will be 6 metres of cable sticking out, so while stretching there must be enough cable to go in to the  rope.

The tube will have holes in it to let water in.
For the weight I will use PVC coated diverbelt lead.

The cone can be from melted led, a good idea!

Hendrik


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