Imagenex fish stability

[stealthdive]

I just aquired an imagenex yellowfin sonar and tryed it out for the first time today. I was using it in a shallow river where I know there is a tugboat that sunk. The river is about 20ft deep and I had the fish about 10ft down. The images I got were very poor. I believe this is due to the fish "swimming" back and forth while underwater. All the images were very wavy. I tried moving the tow point forward and back on the fish as well as adding and removing more weight but nothing seemed to help me get any better stability. Can anyone with experience with an imagenex sonar give me any pointers?

Thanks,
Dan

[Unregistered]

longitudinal stability

I just aquired an imagenex yellowfin sonar and tryed it out for the first time today. I was using it in a shallow river where I know there is a tugboat that sunk. The river is about 20ft deep and I had the fish about 10ft down. The images I got were very poor. I believe this is due to the fish "swimming" back and forth while underwater. All the images were very wavy. I tried moving the tow point forward and back on the fish as well as adding and removing more weight but nothing seemed to help me get any better stability. Can anyone with experience with an imagenex sonar give me any pointers?

Thanks,
Dan

Basically, it sucks. Anyone using the Imagenex units successfully have highly modified the towfish because of this. The longer the cable length the less severe the problem. If you only have 10 ft. of cable out have a lot of work to do.

[Unregistered]

longitudinal stability

I just aquired an imagenex yellowfin sonar and tryed it out for the first time today. I was using it in a shallow river where I know there is a tugboat that sunk. The river is about 20ft deep and I had the fish about 10ft down. The images I got were very poor. I believe this is due to the fish "swimming" back and forth while underwater. All the images were very wavy. I tried moving the tow point forward and back on the fish as well as adding and removing more weight but nothing seemed to help me get any better stability. Can anyone with experience with an imagenex sonar give me any pointers?

Thanks,
Dan

Basically, it sucks. Anyone using the Imagenex units successfully have highly modified the towfish because of this. The longer the cable length the less severe the problem. If you only have 10 ft. of cable out you have a lot of work to do. In a river I would recommend you look at a rigid mount to the boat.

[stealthdive]

imagenex Mods

Thanks, I actually have 300ft of cable but I was not aware that the condition could be reduced by letting out more cable. I should be able to make modifications to the fish at some point. I have read through the old posts and found one that where someone has modified a sport scan. Can anyone that has made mods to or seen successful mods of an imagenex sonar tell us about them? I should be able to make mods but would like to see some successful mods first so I do not have to reinvent the wheel.

[HydroGrafx]

I have a sportscan that is the same general towfish design. I have added a small aluminum vertical fin that basically extends the existing fin above the body of the fish. This helped dramatically with wobble, especially when cable out was very short. Also, I keep the weight balance where the fish is slightly tail high when in the water.

I think I have about 12-15 pounds of ballast, with all the weight near the front and bottom of the fish. Initially, I had more weight, but when the fish was shallow it tended to "pendulum" port and starboard.

I am away from my equipment at the moment, but I will take a picture of it later today to give you an idea for a fin. Also, I can confirm the attachment point with the photo.

Patrick

[stealthdive]

Imagenex mods

Thanks HydroGrafx,

I can't wait to see the pictures! How do you manage to get weight up front in the fish? Also do you use a depressor for deeper searchs and if so did you make it or buy the factory one.

Thanks,
Dan

[HydroGrafx]

The sportscan plastic nosecone is removable, I had assumed the Yellowfin was the same, but maybe it isn't. I also have a bag of lead shot in the nosecone itself.

All my work is in relatively shallow water and I never use the towfish with more than 30 feet of cable out. Usually, it is with 10-20 feet out.

Patrick

[Unregistered]

The sportscan plastic nosecone is removable, I had assumed the Yellowfin was the same, but maybe it isn't. I also have a bag of lead shot in the nosecone itself.

All my work is in relatively shallow water and I never use the towfish with more than 30 feet of cable out. Usually, it is with 10-20 feet out.

Patrick

I have much better luck with the towfish mounted in front of the bow when doing shallow water <20' searches. This avoids turbulence from the hull and propeller. Agreed the fish should be nose heavy in the water. Be careful with the attachment point. They are known to "flop" on their sides and drag through the water with one side pointing almost straight down and the other side pointing to the surface. The nose of the fish canted off to the side at an angle. This will show up in the display with little to no detail on the surface side and very strong signal return from the first bottom echo on the down side.

[HydroGrafx]

I also tow from the front for the same reasons. The lower frequency is very telling of orientation problems in the sonar record since surface reflections are much more pronounced than in the high frequency mode. Sidescanning by a large straight object like a barge or seawall also reveals if the fish is wobbling side to side.

I have attached a few images. Hopefully they will work ok.

Patrick

[stealthdive]

Thanks for the pictures of the modifications. I will be attempting something similar to them soon and will post pictures of whatever I end up doing.

Does anyone have any recommendations for deeper towing modifications with an imagenex?

Dan

[Clart]

fish stability

Another modification suggested to me by two people who should know about these things (equipment hire and sales people) is the use of a 'depressor wing' for supposed deep tow and stability.

It's a wing shape, sort of looks a bit like a Stingray, but made of lead and attaches to the tow cable in front of the fish. The idea is it sinks the fish and prevents the fish from rolling and yawing by damping the cable ahead of the fish.

I've yet to try it but should be able to report back within a month how it goes. My gut feeling is a preference for the body modification mentioned earlier in the thread ie to go for an extended body filled with lead and i'll be trying that out also as I have two Yellowfin to play with.

[Clart]

I also tow from the front for the same reasons. The lower frequency is very telling of orientation problems in the sonar record since surface reflections are much more pronounced than in the high frequency mode. Sidescanning by a large straight object like a barge or seawall also reveals if the fish is wobbling side to side.

I have attached a few images. Hopefully they will work ok.

Patrick

What is the metal you used to extend the body? Is it a standard sized pipe?