fish finder / sonar

pjm · 11 July 2002, 15:25

I am thinking of getting some sort of depth gauge for my rib (just for fun). I was surprised that most of the fish finder type only show the depth directly below the boat. Is this much use???

I then found some ads for forward scanning sonar that shows the depth for something like 150M infront of the boat. This sounds more promissing.

I would be interested to hear peoples views on this.

gaelforce · 12 July 2002, 13:53

well i think the depth sounder is a great yoke. avoiding running aground is the main advantage and you can alarm for shallows and then take it easy keeping a sharp lookout (lookdown?) ahead. of course, looking forward is an advantage but more costly methinks. as for finding fish, erm well, lets say dont believe every fish than swims on ur fishfinder!

Garygee · 13 July 2002, 18:56

Hi there

Never had a forward looking sonar on a RIB but have a yacht.

It was the echo pilot silver.

Had little sucess with it was great in deper water but seamed to get confused when running in shallow water.Also the depth shown in not the depth under keel but a average of the depth so far in front of you.

On paper they look great. Maybe I had fitted the previous one wrong, wrong place etc. They look ideal for RIBS but need I need convincing to fit another to my new RIB especially at 800 quid !!.

Has anyone else had then and had good results ?.

Regards Gary

Richard B · 15 July 2002, 21:21

I'm not the best informed person on this, but have been told that depth sounders on RIBs aren't particularly popular, as they don't work at all when the boat's on the plane. This was confirmed by my experience of a charter RIB which had a sounder fitted - it worked very well at displacement speed (which is a sensible sort of speed to be doing when you're concerned about the depth!) but not at all when on the plane. I would fit an ordinary sounder to a RIB as I've got a peculiar aversion to running aground, but guess that the expense on a fancy forward looking one wouldn't be particularly worthwhile.

Alan · 16 July 2002, 10:03

Depth sounders or fish finders on RIBS can work whilst on the plane if the transducer (which is usually transom mounted) is installed so that it will still be in the water when the boat is planing. Often times they aren't and if not airborne are in aereated water and hence give no reading. That being said, a transom mounted sensor is reading the depth at the stern of the boat - i.e. what you have just gone over. If you are doing 35kts by the time your shallow alarm has gone off you will know the water is shallow by the sound of your outboard/drive leg & prop hitting the bottom!!

A depth sounder of some sort it essential kit however. The economics of them seem to make it cheaper to fit a fish finder (even if you are never going to fish or wreck find) than a pure numerical sounder. I also find it quite useful to have a graphical picture of what the seabed is doing.

No experience with forward looking ones but know they are expensive whereas a cheap fishfinder is £150 or so.

HTH, Alan

pjm · 16 July 2002, 17:55

Thank you all for your comments.

It looks like a cheap fish finder is the best option for a rib.

Keith Hart · 16 July 2002, 19:55

Hi there

There has been MUCH debate on this subject in RibNet, see previous postings (try a search on the subject).

It appears from the extensive research I have done (on the net etc.) that most fishfinders only work at slower speeds, due to the effect of planing and water disturbance. But, as I suppose they are FISH finders, they are actualy designed for fishermen milling about and looking for FISH, so we shouldn't be surprised!

I hope to get mine later in the year (remember to my BOSS

it's a SONAR), and I want (need

) it for the fun (necessity

) of just finding out what is under the boat.

I do remember though that there was a hand-held sonar (looked like a torch) that you could use in front of the boat.

Keith (still waiting for it) Hart

narked · 16 July 2002, 20:19

Or you could do what somebody on our boat handling course did, keep going until you see a bloke in waders fishing infront of you, but for some reason he didn't realise that that meants "shallow water" and kept going. Luckily I wasn't on the same boat, and it wasnt a RIB either, nor did it have any instrument to find depth. The RIB I was in however did, kinda useful with it being a dive boat and all...

Garygee · 16 July 2002, 21:38

On the issue of transom mount transducers, has anyone any info on how through hull transducers perform on RIB's.
At least they will be under the water

That is assuming you can get to the hull to fit one

.

Gary

Rene · 17 July 2002, 00:44

Hi

I just couldn't stop my self replying to this thread.

I have both a transom and a through hull transducer on my RIB.

The through hull transducer is connected to my eagle fishfinder
and the transom mounted to my Furuno Color fishfinder.

I don't know much about the through hull transducer, since it put inside the hull on production. It could also be the big diference in the fishfinder. But the transom one is the best.

I can have a nice steady picture of the sea floor with my transom mounted transducer and the Furuno, going up to 38 Knots, without any disorder (except when the boat is completly out of the water).

The main thing here i the position of the transducer. Mine is on the right hand side (star board) of the engine about 30 centimeters from the engine. The buttom of the transducers if about 5 mm below the rib hull, making some of the water go behind the transducer and up the transom, but keeping the transducer in the water at all times.

I havn't tried the forward looking ones, but would like to get more info on this subject. Also if anyone have had any experience with the ones thats looking out to both sides of the both. Could be great for Wreck finding when diving.

Rene