Humminbird 987c

[Ingemar Lundgren]

Have anyone used this sounder http://www.humminbird.com/products.asp?ID=512 ?

Looks interesting but i get a bit suspicious about "cheap" products such as this. Anyone got real world experience with it?

[jluttichau]

Hi,

It says on the specs page that:

Depth Capability: 100 Feet Down, 240 Feet to Each Side (262kHz)

Is that enough?

Cheers

[Ingemar Lundgren]

Duhh i missed that part, that is far from enough. Thank you for pointing that out.

[jluttichau]

Hi,

The side scan feature has a reach of 1000 ft. so maybe that is only the echo sounder that is rated for 100 feet. So you could combine it with an ordinary echo sounder or something, I'm not sure how this stuff works.

Cheers
Jonas

[Ingemar Lundgren]

I’m not sure either, sound like a gimmick. I will give it a try anyway.

[jluttichau]

Hi,

I would love to hear about it when you've tried it. What kind of boat are you going to mount it on?

Cheers

[Ingemar Lundgren]

On our diving boat the "Otto". It is a rebuilt pilot cutter. 20 mph top speed and 14m length. The shop offered me to test it so i guess i have to tape it to a pole and stick it in the water as i can´t mount it permanently for testing. We have a side scan sonar to so i am only interested in the Hummingbird as a substitute for the current Furuno sounder.

[jluttichau]

I wonder if it will be of any use if the boat is pitching from side to side, as the transducer seems to be mounted on the ship itself and not towed. Looking forward to your test results :)

Cheers

[Ingemar Lundgren]

I am not planning to tow it :D I will attach the transducer to a pole and lower it from the side of the boat and then attach it firmly to the boat. Should work.

[Per Lundström]

Here are some pictures taken with the above sounder in Sweden.

http://www.wern.com/id13.html

[Ingemar Lundgren]

Must say that i am impressed. The question is how it will preform at 50-70m depth ?

[bazmlb]

would this be a good unit for a group starting out to find wrecks with, a lot are in the 25 m range with some in 45-70m

Barry

[Richard Lundgren]

would this be a good unit for a group starting out to find wrecks with, a lot are in the 25 m range with some in 45-70m

Barry

It sure looks like its going to be a good entry level search tool. As we understand the depth for the side scan sonar function is about 30m with limited swath. The image will also deteriorate if the boat moved due to waves etc. Still, I would buy one, its dirt cheep.

Take care
Richard Lundgren

[bazmlb]

Thanks

we will give it a try, during cool season its pretty flat over here so should be good i hope, also looking around for a Mag any suggestions, i have heard of people putting their own together

Barry

[Ingemar Lundgren]

The problem with a hull mounted sonar is that you can not get below the thermocline. In the baltic sea during the warmer season the thermocline is huge giving these kind of systems a sharp decrease in performance. But considering the price i would go for it especially if you also need a chart plotter. You can expect to get good pictures from 30-50m depending on thermoclines etc. In some cases i think a hull mounted system is to be preferred over a side scan. If you are doing shallow surveys (15-30m) inside an archipelago or near shore i think this system has a place.

[bazmlb]

We dont get much change in temp in the water with thermoclines here, its pretty warm all the way down usually around 29c, with maybe a 2c drop around the 20m mark so this solution sounds ok i think.
Will try it and post some pics when we hit some wrecks

[Peo]

I'd be very interested in hearing some more about experiences with this sounder too.

We have an area with a large number of side scanned targets but without exact positions, in the 40-65 meter depth range, and are thinking about using this unit as a way to shorten the time it takes to locate the target from the approximate position compared to our usual search pattern with a traditional fish finder.

[Ingemar Lundgren]

Bazmlb, in warm water such as yours it should work well. Do not expect to get good performance deeper then 40-50m though (maybe less?). If possible try to borrow a unit and test it first. You could attach the transducer to a pole an lower it down along side the boat for testing.

[Peo]

In the winter, we don't have much of a thermocline in the area, though the water temperature is 8-9 centigrades. I'll probably give it a try...

[Mats]

It would be nice to try this unit with an extension cable and a towed transducer on a homemade towfish.

[Olly Agbebi]

It would be nice to try this unit with an extension cable and a towed transducer on a homemade towfish.

Is this a feasable DIY option?

[Mats]

Humminbird sells extensioncables for this unit, but the cable is only 10 feet.
Lets say that you will need atleast 30 feet of cable just to get it in the water. Then you will have to make your own extension cable (as I dont thing putting 3 of there extensions together is a good idea).
Humminbird suggested trying a low-loss, low capitance cable (Belden 9730).

You will also have to consider that with larger depth, you will get a larger 'blind spot' under the boat and reduced quality of the scan image, so you will have to lower the fish more in the water to reduce this blind spot and get a better scan.
Lowering the fish will make the search area on each side of the boat smaller, but with a better resolution and a smaller 'blind spot'.

The 455Khz beam seems to go out and down at about 45 deg angle, and tests has proven that at 55ft of water you will get useable returns out to about 200ft each side with a pretty good resolution.
With this data, you can get a picture of how long cable you will need (cable length is about 3-5x tow depth) if you want to search at a specific depth.

There is most certainly a max length that a cable can be, before the loss in signal strength is to big (I believe only experimenting will tell this length).
So, it is a feasable DIY project, but it will require a lot of work and testing.

[Olly Agbebi]

Humminbird sells extensioncables for this unit, but the cable is only 10 feet.
Lets say that you will need atleast 30 feet of cable just to get it in the water. Then you will have to make your own extension cable (as I dont thing putting 3 of there extensions together is a good idea).
Humminbird suggested trying a low-loss, low capitance cable (Belden 9730).
You will also have to consider that with larger depth, you will get a larger 'blind spot' under the boat and reduced quality of the scan image, so you will have to lower the fish more in the water to reduce this blind spot and get a better scan.
Lowering the fish will make the search area on each side of the boat smaller, but with a better resolution and a smaller 'blind spot'.

The 455Khz beam seems to go out and down at about 45 deg angle, and tests has proven that at 55ft of water you will get useable returns out to about 200ft each side with a pretty good resolution.
With this data, you can get a picture of how long cable you will need (cable length is about 3-5x tow depth) if you want to search at a specific depth.

There is most certainly a max length that a cable can be, before the loss in signal strength is to big (I believe only experimenting will tell this length).
So, it is a feasable DIY project, but it will require a lot of work and testing.

Thanks Mats.

Idealy I'd like to be able to scan to 80m depth but would settle for 50/60m depth.

Our water temperature varies between 17C and 30C and averages 25C. If I've understood you all correctly, for a boat mounted sender at 30C there is a possibility of succesfully scanning 50m but the scanned area will be narrow and the blind spot under the boat will be wide. Can any one quantify these limitations for me?

Has any one tried making a fish and been succesful?

Olly