New Sonar Technology

[Rusty123]

I installed a Garmin 741xs MFD last year, which I've been quite happy with. As I understand it, This model has "CHIRP" and "DownVu" technology built in, and "SideVu" can be added with a black-box add on. I would need to add a transducer to use any of this. (I have a standalone depth finder that works fine).

Anyone have experience with use of the new technology, particularly on a sailboat? I occasionally do a bit of fishing or crabbing (Puget Sound), so I'm thinking it might be handy for that, plus maybe assisting with anchoring. I don't want to spend a bunch more money, but it would be nice to utilize the features I already have in my MFD.

Comments?

[Jesse]

Definitely have a look at the transducer needed to accomplish what you want. The ones I've seen are huge and would create considerable drag.

[goboatingnow]

Unless you are interested in detailed bottom scans of the sea bed, I don't see the real attraction.

dave

[Massjester]

I'm sorry if this is an inane question, but why wouldn't sonar be useful for detecting sub surface objects at sea that might present a navigation hazard.

[Stumble]

Originally Posted by Massjester

I'm sorry if this is an inane question, but why wouldn't sonar be useful for detecting sub surface objects at sea that might present a navigation hazard.

It absolutely is. The problem is that to date sonars have been very expensive, have limited range, and were pretty low resolution. Surveying sonars get around this by towing huge arrays (up to 10 miles long) at low speeds.

I haven't looked at the current generation of sonars, but I know a few years ago they started to pop up on large powerboats (70' or bigger) and have slowly been working their way down market as prices and size have come down. But last I looked they are still not very accessible to most cruisers.

[landonshaw]

For me all I am interested in is that the water 6.5 feet deep, the depth of my keel. If I am in shallow water, 10 to 15 ft, we go very slow with a person on the bow. A forward looking depth gauge wold be nice to help I those situations.

[a64pilot]

Originally Posted by Massjester

I'm sorry if this is an inane question, but why wouldn't sonar be useful for detecting sub surface objects at sea that might present a navigation hazard.

CHIRP is amazing for fishing and finding diving sites. What it is is essentially a broadband Sonar that is capable of using a wide frequency range instead of a fixed frequency to discern great detail. I had a Dragonfly on my last fishing / diving boat and it was good for that, but don't see the need for a sailboat, as far as navigational hazards, youv'e hit it by the time you would see it.
At least on the dragonfly the xducer was a pretty good sized teardrop shape that looked low drag, pretty sure if it wasn't the 40 mph speeds of my old boat would have torn it off as it used the same plastic transom mount others use. But transom mounted on a sailboat it would be out of the water flow mostly so drag should be almost non existant.
On the Garmin, you may be able to use a shoot through the hull xducer, that is how I did the one for my 740s, that way no external xducer and no additional hole in the boat, but my 740 was not CHIRP, so I don't know.
If I had a 741, I'm afraid I'd want the CHIRP xducer just to see a detailed picture of the bottom just because I could, maybe not real useful, but it's cool seeing the bottom in detail

[Massjester]

Originally Posted by landonshaw

For me all I am interested in is that the water 6.5 feet deep, the depth of my keel. If I am in shallow water, 10 to 15 ft, we go very slow with a person on the bow. A forward looking depth gauge wold be nice to help I those situations.

Greetings landingshaw, I agree completely.

I saw a product named EchoPilot which seemed to offer a fine forward looking 3D image, but the range seemed much to short to offer meaningful protection while underway, although I could foresee it being helpful while exploring small unfamiliar anchorages.

Perhaps my ideal does not exist.

[skipmac]

At least a half dozen threads on this exact question in the last couple of years. Bottom line, unless you are going slow in calm water a forward looking sonar will not give enough warning of floating hazards to be of any use at all.

If you are in deep water and approaching a reef or shoal with a rapidly rising bottom then would probably get sufficient warning to do a 180 before you hit. If you entering an uncharted harbor at very slow speed you can use sonars to find the channel or at least avoid the shoals.