Depth Sounders

having my wife on the bow yelling "Mark Twain" just isn't in the cards.



Well someone will be needing accurate info when forward progress is STOPPED.

FF wrote:Well someone will be needing accurate info when forward progress is STOPPED.

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That's easy, there's a formula for that and it applies to all kinds of boats:

Dw =< Db

When forward progress is stopped due to grounding, the Depth of water is equal to or less than Draft of boat.


-- Edited by RickB on Wednesday 10th of November 2010 05:53:42 AM

In ICW motoring thru Georgia , we noticed an interesting result.

On out 90/90 the prop is a 19x13 , 2 blade , with "power boat " blades , rather than the thin "sailor" blades.

It is a cruising prop , so we can only turn 2100-2200 at flank (not 2500), but since wecruise ar 1600 to 1800 there is no problem.

Like every prop out Speed of Advance is calculated as part of the prop selection.

In tidal GA when just a bit out of the last channel (created by a barge "pushing mud" ) we go thru very sofy mud.

Its not enough to noticibly slow the boat , but we can hear the prop cavitating from the slower SOA.

Not every contact with the bottom is exciting , we just try to guess where the channel is and head that way.

We have been suffering through a poorly installed transducer experience for the last two summers. The outcome has been maximum depth readings of 400' and no fish finding whatsoever. We will be upgrading shortly to a proper through hull tranducer and perhaps a new DS. The point here though is the tranducer. With the through hull, we expect to have much greater depths showing , but more importantly a much cleaner and more accurate reading of the bottom. *Fish finding should also significantly improve, but that will only be for the delight of guests, as I am not a fisherman. My point is that the through hull will markedly improve the performance of the DS. (We are going from a transom style transducer siliconed to the inside of the hull to a through hull bronze transducer.)

I will agree that for most of the cruising we do (West coast of BC) any depths of more than 400' are not an issue, but I like to have the DS going all of the time, and when it goes into Charlie Sheen mode it can be annoying.

Furuno sells a Sonar that can see in all directions. But it isn't cheap!! And I would imagine it to be much like radar(it is actually exactly like radar in theory) in that it would take a lot of practice to get good at using it. But it's main purpose is finding fish in deep water...

Before putting more holes in the boat why not try remounting the current T.D. if it still is working
Maybe the problem is a poor bedding, either air bubbles or too thick a silicone layer or both.
A poor mounting can degrade the signal. I realize it may still not be what you want but I have an aversion to more holes in the hull and may be worth a try before
providing more water entries.

Baker wrote:
Furuno sells a Sonar that can see in all directions. But it isn't cheap!! And I would imagine it to be much like radar(it is actually exactly like radar in theory) in that it would take a lot of practice to get good at using it. But it's main purpose is finding fish in deep water...

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*The Navico family (Lowrance & Simrad) have come out with their Structurescan which looks very promising as it appears to give a great representation of the bottom all around you. Humminbird has something similar.*

How useful these are in the real world I don't know, but as a way of exploring the bottoms of bays and inlets without getting wet there might be a certain appeal. I'd still want a traditional DS for proper navigation though. Of course traditional is open to interpretation.

*

*

C lectric wrote:
Before putting more holes in the boat why not try remounting the current T.D. if it still is working Maybe the problem is a poor bedding, either air bubbles or too thick a silicone layer or both. A poor mounting can degrade the signal. I realize it may still not be what you want but I have an aversion to more holes in the hull and may be worth a try before providing more water entries.

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*We've played with the mounting but we are cursed and blessed with a thick hull (and maybe skull) that confounds our efforts, so are biting the bullet. I agree with your thoughts though; this will be the first time we've had a through hull transducer.

*

** I installed one on my 1977 Marine Trader. I bedded it in epoxy and it works just fine.

You can bed them in Sikaflex and it works as well, and is a bit more forgiving of surface and removable later if necessary. Once something is embedded in epoxy it's there forever - which can be a good thing, but not always.... Actually, I placed the transducer of the Lowrance GPS/Sonar combi I installed 7 ys ago in the for'd bilge as a temporary thing, just screwing the mount to a stringer and placed well wide of the thick keel, and it has worked so well there, just sitting in the puddle of water in that part of the bilge, I never got round to moving it to more permanent place, it works so well.... I also have an older Seafarer type which has its transducer in a mineral oil-filled tube, as back-up at the main helm, and an monochrome Lowrance XC70, depth only, which has a true through-hull, at the flybridge helm, and they all read fine and agree with each other, and can be run together as they are each using different frequencies, but I really don't want any more holes in the hull.

What I'd like to do now, as the Lowrance XC70 up top has bad screen drop-out with age, is put in another Lowrance colour depth sounder, (possibly a combo GPS also), up on the flybridge, and I'd love to be able to use that same through-hull transducer, which uses the same frequency as the XC70, and all the wiring from the flybridge right down to the thru-hull already there, but they tell me I can't. Does anyone out there know why not? Isn't it the main sender unit in the head that does the work, with the transducer just passing the pulse sent by the sender above, and receiving the rebound pulse. Surely the electrics in the transducer and wire connecting would be essentially the same, with a change of plug connection into the head unit being the thing which would need changing? Am I wrong in suspecting it is just a ploy to sell more equipment, rather than truly necessary, why newer models are made so they cannot use a pre-existing transducer from the same manufacturer and designed to send the same frequency...?


-- Edited by Peter B on Friday 25th of March 2011 05:22:16 AM

What was the question?

Oh yea, depth sounder.

"My other depth finder is a garmin and I used a airmar transducer the comes with a cup that you attach to the hull. You can adjust it for the angle of the hull, fill it with mineral oil and put the transducer in it. Works great and it has been there for many years."

I have installed three of these in three different boats and they work great. They recommend non toxic antifreeze now, not mineral oil, but either will do just fine.

I guess my hull is about an inch thick where the transducer is mounted and it works just fine. Actually, I was testing the mounting area so I just coated the bottom of the transducer with KY jelly and set it on the hull with a sandbag to hold it in place. By the time I got around to testing in deeper water and at speed, I had misplaced the cup and the rest of the parts. It's still in "test" mode after about two years. One of these days, I'll order the parts and install it permanently.

As for reading depths, all I really care about is, Is the water deep enough to run the boat and shallow enough to anchor it?

As for reading depths, all I really care about is, Is the water deep enough to run the boat and shallow enough to anchor it?


Contour Nav is a fine system , esp if you have a paper recorder, for when the GPS is down.

FF wrote:
As for reading depths, all I really care about is, Is the water deep enough to run the boat and shallow enough to anchor it?


Contour Nav is a fine system , esp if you have a paper recorder, for when the GPS is down.

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*

*Although you wouldn't have as much history as a paper recorder (which was very nice in its day, if rare on recreation vessels), would not a modern DS with a few minutes of depth history give you a reasonable amount of info for contour navigation?

"would not a modern DS with a few minutes of depth history give you a reasonable amount of info for contour navigation?"

You are approaching a shore near the continental shelf.It would be nice to know WHEN you crossed the line. A LOP.

Simply knowing you are still in deep water or not ,,is little navigation help.

Many on shelf areas are very flat , so simply knowing the current depth is almost useless in creating a LOP..

Better and simpler approach nowadays surely is a back up GPS (even small hand-held), and be sure, not just fairly sure, where one is. Depth contours only tell you where you might be at some point parallel to the shore - depending on correct tide information being on hand for that spot as well - not where you are in relation to the shore exactly, unless you already know, in which case there is no drama anyway. Trying to match chart contours from paper or plotter if really worried about where you are is just too much stress.

As I spend a lot of my time fishing and diving a depth sounder/fish finder is extremely important.
I run a duel frequency Furuno FCV 585 and previously an Echotec 1000 watt.
In changing the sounders I did not have to change the transducers 50 & 200 Hz seperate transducers so it was a pretty simple change over.

GPS units are pretty cheap these days so I run 2 mast mounted units , carry a handheld in my escape bag and have a USB unit that can be used in my lap top if required.
But if the whole system shuts down then it's back to paper.

Benn

"Better and simpler approach nowadays surely is a back up GPS"

Great idea , until the GPS system is put out of service.

Probably for 1/2 a decade.

North Korea already has the ability , as do other more rational Nations.

Belt and suspenders may be more work than push button ,

but having it aboard is like a life preserver or fire extinguisher, Prudent.

Point I was trying to make is that you can overdo the "what if" scenario to the point you are virtually paralyzed like a possum in the headlights from fear of not having enough back-up because "what if", and many therefore never really get out there and relax and enjoy the trip as much as they might, and some of the views one sees on this forum sometimes tend to feed that fear.

Peter B wrote:
..... you can overdo the "what if" scenario to the point you are virtually paralyzed ....of not having enough back-up because "what if"....and some of the views one sees on this forum sometimes tend to feed that fear.

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* * * * Couldn't agree more! I suffered from this malady years ago before I diagnosed it and found the cure. What's the cure? Suck it up and get out there! (With the obvious pre-cruise preparations, of course.)

*

(With the obvious pre-cruise preparations, of course.)

The simplest pre cruise precaution is to simply select gear that could be used in an emergency.

If one is going to knock a hole in the bottom for a depth sounder , why NOT a unit that might someday be handy for navigation?

Any small radio with a AM coil antenna will work for RDF (roughly), is it unwise to have one aboard?

Taking the bottom, a stout marked pole can both measure where the water is deeper , and help push off.

Painting the vessels depth , or 1 ft stripes on a pole should not cost that much that another year will be required before tossing the power hose.

I am thinking about putting a sounder in the stern of our Krogen. I have used a hand held depth sounder when anchoring and stern tying . Any one done this? I would stick a transducer inside vice drill a hole.

You can't put a transducer inside a*cored hull, and unless they've changed, all Krogen's have Airex (or approved equal) coring.

Keith is right about cored hulls and shooting thru the hull transducers.* However, the 42 Krogens stopped coring below the water line some time around 1993.*

superdiver wrote:
My only depth sounder is in the lower cabin, is it possible or hard to tie in another depth sounder to the existing one for the fly bridge? Or is it better to make a redundant system to put on the fly bridge?

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********* You can often use two simular depthfinders on one transducer.* A selector switch is required because you can only use one at a time.* An example is the Lowrance switch in the image.

JohnP

*

superdiver wrote:
My only depth sounder is in the lower cabin, is it possible or hard to tie in another depth sounder to the existing one for the fly bridge? Or is it better to make a redundant system to put on the fly bridge?

*

How old is the unit at*the lower helm?* It might be the time to upgrade with newer technology on the fly bridge.* We added*a Lowrance HDS-5x broad band*unit to the fly bridge.* The quality is comparable to commercial units that use to cost several thousand dollars.* On line the unit was less than $500.00 (minus transducer).

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*

We do have a solid hull below water line. Superdiver, we have 2 depth indicators running from 1 thru hull transducer. Autohelm (now Raymarine ) ST60s. no selector switch required. Both on at once.