Simple down and dirty towfish design help needed

[hobbit]

OK, so I bought a used Humminbird 1198c si. I currently have the transducer transom mounted and I must say I am fairly impressed. I also realize the deeper I can get the transducer, the more sonar shadow I will get from smaller, less pronounced targets.

I would like to build a towfish to accommodate the transducer, and was wondering if any forum members have done this themselves. I know there are several towfish construction threads on the Humminbird site and others, but I hoped to get some input from some of the pros on this forum.

I am primarily interested in working shallow water (say 60 feet or less). Any help, advice and experiences on potential cable lengthening issues are also most welcome. Thanks in advance.

 

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[Salvor6]

I built a towfish for my 1198 so I can use it on different boats. Look on Ebay for the 30 foot extension cable. It's real easy to make. I will post a pic tomorrow.

 

[ropesfish]

and look here:
Humminbird Side Imaging Forums - Index particularly this sub forum: DIY - Side Scan Sonar and towfish
RGecy may still run this site...

 

[Salvor6]

Here is a pic of the towfish I made from PVC tubing.

 

[hobbit]

Here is a pic of the towfish I made from PVC tubing.

View attachment 1465982

It looks funky, yet functional. I like !

A couple of questions:

On what sort of pvc fitting is the transducer and tow cable attached ? I don't recognize it as a normal pvc fitting.

Can you explain, at least partially, how you made and mounted the fins ?

I can figure the rough dimensions from the measurements of the transducer, but what did you use for weight and roughly how much weight did you use ?

My assumption is that it is balanced at the tow cable attachment point ?

Thanks in advance for your help.

 

[Salvor6]

The transducer is attached to a block of aluminum that is just bolted to the 1-1/2" PVC tube. It helps if you work in a machine shop. The fins are just 1/4" PVC glued to the tube. I filled the tube with sand and glued end caps. I don't know what it weighs but it sinks in water. "Balanced"? What balance? I just drop it in the water and because of the fins, it tows straight. I saw the tow fish made by another guy on the Humminbird forum. Talk about overkill! It is aluminum tubing with a stainless steel end cap and he has four 30 foot extension cables. That would cost hundreds of dollar$ to make. You don't need all that. Down and dirty. Just get your fish a few feet underwater where it is not affected by waves and it will give you a sharp image. My towfish cost less than $10.

 

[aquanut]

I can vouch for the one Salvor6 made. It also can be deployed to avoid the prop wash. Worked great for us.

 

[ropesfish]

Pete and John...tow speed 4-5 kts or just slow or fast enough to get the fish towing at the right depth?
Does the fish take out all the surface wave effect or just most?
On my inboard boat I have to run a transducer on each side of the prop to get sidescan on both sides...I'll pull one off and put it on the fish instead. I can get Down Imaging and normal depth finder functions out of one transducer as well as side imaging on that side...this will work.
With some luck the new band saw blades I ordered will be here at noon...I could have one done by dark.
Nice one, Pete..

 

[aquanut]

Pete and John...tow speed 4-5 kts or just slow or fast enough to get the fish towing at the right depth?
Does the fish take out all the surface wave effect or just most?
On my inboard boat I have to run a transducer on each side of the prop to get sidescan on both sides...I'll pull one off and put it on the fish instead. I can get Down Imaging and normal depth finder functions out of one transducer as well as side imaging on that side...this will work.
With some luck the new band saw blades I ordered will be here at noon...I could have one done by dark.
Nice one, Pete..

If you want to go faster, you could try a planer you probably already have with your fishing gear. Rigged properly, it would also act as a safety if you happen to run into a reef. The fish got rid of surface noise for us.

 

[Rüdiger]

Hi Hobbit

I have built this towfish for my HB898;
120cm PVC pipe, three extension cables and spare ballast.




mvh
Rüdiger

 

[seekerGH]

When people are talking about a downrigger, it is like this concept.



These setups allow for you to set the depth much more accurately, and even tow at different speeds while the fish remains level. Bands too far apart, or overlapping, just raise or lower the main feed line.

Another positive of a downrigger system is that you can make the fish a little buoyant, that in the event of a disconnect, or hang on the downrigger, you can disconnect the weight, and the fish can float to the surface and be found.

This is light duty for fishing, but you get the concept.


For the towfish, you may want to consider a larger diameter tube, that the unit can be flush mounted in. This will avoid towing a virtual hook that gathers up weeds and can cause a potential snag. Keep the fins to 3, level and up to avoid snags.



Keep in mind that discontinuity in the fish means noise, and that can degrade the signal processing with white noise in the return.

 

[seekerGH]

Was trying to find some pictures, but I have see fish with a camera mounted in a clear nose, done right, that would be really slick.

 

[Rüdiger]

Hi Seeker

Do you mean based on this camera system?
Sea View Seamaster 600 Underwater Camera System

mvh
Rüdiger

 

[hobbit]

Hi Hobbit

I have built this towfish for my HB898;
120cm PVC pipe, three extension cables and spare ballast.

View attachment 1466686
View attachment 1466687

mvh
Rüdiger

I love it, Rudiger. But I'm not sure I would call it down and dirty, LOL

Realistically, with the time I have available , I probably have a year or so of search areas where I would be deploying the fish at 10 ft. or less.

Your fish looks fairly large and I am not sure I would need the option of flexible ballast weight.

Your rigging set-up, while super cool, would attract way too much attention in my area.

I am looking for simplicity and portability. I plan to use the fish on several different vessels, but predominately on a little 14 foot Whaler.

I am interested in your fin design, though. It looks really simple to construct. It looks straight forward, but would you have any more photos or construction tips ? Do you think it drags more noticeably more traditional fin designs ?

Thanks in advance.

 

[seekerGH]

I probably have a year or so of search areas where I would be deploying the fish at 10 ft. or less.

at 10 feet, I would not bother with a towfish, just use a mount attached to the side of the boat.