Question from a "Foreigner"

[colvic]

Question from a \"Foreigner\"

As you chaps are used to being able to operate in shallower water than us raggies, is there a depth sounder or fish finder that you can recomend for accuracy whilst in the shallows say 1 to 3 mtrs.

Phil

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[hlb]

Re: Question from a \"Foreigner\"

Well every one I'ved used seems very accurate. Theres some bottoms that they dont like cos thay cant get a proper fix. Like thick weed or soft mud. I have a depth sounder and a fish finder. That way when one dont work the other usually does. Last week I had .01 showing on the fish finder and did not hit the props on anything. Dont think I'd try that again though!! That is a Plasmo fish finder. Handy thing is, it's through the hull so no holes or boat out of water for fitting.
But I would have thought any depth sounder would be ok.

<hr width=100% size=1> <font color=blue> Haydn

 

[petem]

Re: Question from a \"Foreigner\"

Important thing is to set the offset correctly, i.e. the vertical distance between the location of the sender unit and the bottom of the hull.

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[DavidJ]

Re: Question from a \"Foreigner\"

Agree with comments from Haydn and Peter. Just drawing your attention to a thread about a week ago expressing dissapointing results from the type that 'look forward'.
All standard ones work fine.
David

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[tcm]

Re: er, can powerboats use less depth?

It's an interesting idea that powerboats can use less water than a raggie, and although they draw less water, they don't go many places that a raggie would never go - the exception being perhaps some anchorages. This is cos grounding is distastrous for most planing powerboats - the props hit the ground before anything else. So not many powerboats would blast along in 2metres of water which at any moment could drop to under 1. In other words, they would (or should) be creeping along inunfamilair waters than read 1.x if their limit is x. And this is not the same for raggies - many east coast raggie regularly hit the bottom, even use a bump as the trigger to tack. So, powerboats don't tend to push the envelope as much as an east coast raggie would do, i beleive.

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[hlb]

Re: Question from a \"Foreigner\"

Yes TCM has hit the nail on the head once more. Even though we do not draw as much water. The concequench? of hitting bottom at 20/30 knots. props first, is not to be welcomed, where as sliding the keel along bottom in a raggy is only an inconviniance. Once us motorboaties have dragged you off. It's carry on as before. For us it's a compleat bottom refit, shafts, rudders, props. So where as we can sail in shallower water. We are much more carefull about it.

<hr width=100% size=1> <font color=blue> Haydn

 

[colvic]

Re: Question from a \"Foreigner\"

Thanks for all that. I agree that having a couple of tons of steel between oneself and the bottom does give a sort of sense of security, but it is still nerve racking to hear the noise.

This all came about from our experiences on the Mar Menor in Spain last summer when we ended up using a lead line as the readout from the Nasa Clipper was fluctuating so much. Had ensured offset was exact before entering and I expected no problems as the water is so clearyou can see the bottom wherever you are, as long as the surface isn't too disturbed, but I was amazed at just how difficult it is to judge the depth when you can see the bottom.

Thanks again


Phil

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[Deleted User YDKXO]

2 Sounders Interference?

David, I posted a thread about the poor performance of a Incastec (now Echopilot) Forward Looking Sounder fitted to my boat. I phoned Echopilot and they were very helpful. Basically, they're saying that, if you use 2 echo sounders at the same time, they can interfere with each other, something I've not heard before although there is a bit in last month's MBM about the same subject.
I must say I'm not entirely convinced because I've had a fish finder + standard echo sounder working together well on a previous boat but until I can get out to my boat and try the Incastec in isolation, the jury's out

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[Viking]

Re: Question from a "Foreigner"

An extending boathook?
Lead and line?
Or a long pole - If he doesnt mind getting wet!

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[byron]

Re: 2 Sounders Interference?

<font color=blue>Unless both sounders are the same make they are usually working different frequencies and do not interfere with each other which is why you cannot change your sounder and use the existing transducer. Of course there are exceptions to this, I believe for example NASA use the same frequency as Seafarers.

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[Guest]

Re: Question from a \"Foreigner\"

T'other thing to bear in mind is that if you read the small print on the sounders, they have a minimum depth they can work in. We draw about 3'6" (sensibly), and the tridata won't read anything accurately below 4' (and in practice, it can vary wildly at that depth). In other words, if you're creeping up river and the sounder says anything less than about 5', you could bottom out any second...

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[hlb]

Re: Question from a \"Foreigner\"

Funny. Mine seems to read ok with a few inches under it, even had zero. The boat was still rocking!!

<hr width=100% size=1> <font color=blue> Haydn

 

[Guest]

Re: Question from a \"Foreigner\"

We used to creep up through Christchurch with the sounder showing 3.8'. At 3.7', I knew we had to have the legs right up, or we were in trouble. Then one day, I plumbed the depth in the marina, and compared it to the sounder. The sounder thought it was showing depth below the skegs... So having recalibrated to depth from surface, I need to have 4.8' showing, or I bottom out. Previously, it would read 3.7' even if you needed a ladder to get down off the swim platform.

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[jfm]

electronic solution

If you really need to know, get a colour sounder that shows differing intensities of the return signal in different colours. Then if you are in mud or weed, you will be able to see the top of the weed, and the point where the bottom gets hard, all at the same time. Koden do a particulary good set, that has an electronic ability to draw a white line over the colour graph to show the point at which the bottom is firm enough to damage your boat. It also analyses the return signal and displays "soft mud" ,"mud", "rock" etc.

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[duncan]

Re: 2 Sounders Interference?

200mhz is now pretty standard for freshwater and inshore (<500ft) across most manufactures - probably us same sender basic unit even!
50 for deeper water
Many modern units use both the above from the same 'ducer puck.
182 (or 192?) used to be pretty common
many charter fishing boats use 3 or 4 at the same time don't seem to have a problem.


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