any good ideas on how to avoid underwater objects?

[stylesabu]

Has anybody ever used fishfinder/sonar to spot underwater objects. what if FF transducer is turned 90 degrees pionting out front/forward of boat. Would this be able to read rocks/stumps and other obsticals in front of boat?

 

[Guest]

Re: any good ideas on how to avoid underwater objects?

The only way I know of to avoid those things is to go slow and learn the water ways you plan to travel on. Otherwise slow down and "LOOK WHERE YOU ARE GOING !!!" Sometimes those things that end up in the water can't be avoided. The first few weeks of spring are always the worst as well as after very heavy rain fall, stuff gets washed into the water and there is nothing you can do about them. :facepalm:

 

[5150abf]

Re: any good ideas on how to avoid underwater objects?

I don't think turning the transducer will get you anything, you would do alot better watching where yuou are going rather than staring at the fish finder anyhow.

There really is no way except as boateric said, just learn the waters you are on, I have hit stiuff in 6' of water before, you can learn to "read" the water over time, but that really only works on a river with current.

Are you on a lake or river?

 

[roscoe]

Re: any good ideas on how to avoid underwater objects?

any good ideas on how to avoid underwater objects?


stay out of the water

 

[stylesabu]

Re: any good ideas on how to avoid underwater objects?

I'm on lac lacroix in Canada.And we have maps and charts and gps with "bread crumb" trails. yes we also use a spotter, and we follow each others wake at a far enough distance,that if they hit something, the rest won't. The problem is the water level changes as much as 10 feet form year to year. we have most marked on our path in/out so we slow down when we know we are approaching a rock.But when we are fishing,its a little different story, yes we mark every rock we find, and its better every year. but the thing is they/locals and local business use canoe boats/water transport of people and canoes,some of the water doesn't allow power boats unless youre an indian.The canoe boats travel up 70 mph on same water, without hitting any thing.I now they travel same route 5-6 times a day, and at high speed not much of the boat is in the water. i did ask one of the drivers how they navigate at the begining of each season(the ice shifts the rocks alittle). he said sonar I will try my theory on a local river in a couple of weeks, there are bouys and cement pillars for bridges. lets see if i can pick these up and how much notice i may have.It would be nice if it works.will report on my finding in about a month.I have had people tell me it works.But I have to see it before i would reley on it. oh thanks Roscoe good advice. but I think an aluminum boat with jetdrive would be pretty good.

 

[H20Rat]

Re: any good ideas on how to avoid underwater objects?

but the thing is they/locals and local business use canoe boats/water transport of people and canoes,some of the water doesn't allow power boats unless youre an indian.The canoe boats travel up 70 mph on same water, without hitting any thing....

oh thanks Roscoe good advice. but I think an aluminum boat with jetdrive would be pretty good.

wait, a canoe at 70 mph? THIS i have to see! But I agree, a jet boat takes a couple inches max when on plane. With mine, I can actually feel the boat pitch forward when I'm in shallow water at speed, the increased pressure under the transom will actually lift it up and reduce the draft even more. (It pitches at least 10 degrees nose down from the normal attitude, its actually pretty weird feeling it the first time)

 

[stylesabu]

Re: any good ideas on how to avoid underwater objects?

they call them canoe boats because they hane an alunminum rack that will hold 6 canoes. they like 20-22ft boats with 250 on them. they move people and canoes. I will look for pictures.

 

[Moody Blue]

Re: any good ideas on how to avoid underwater objects?

As for your original question, you have to consider the speed at which you will be traveling.

Even if you could get the transducer to detect an echo from an object "just" under the surface, you probably wouldn't be able to react in time to avoid it. At just 30mph your are traveling at 44 feet per second.

 

[mommicked]

Re: any good ideas on how to avoid underwater objects?

How would you point it forward?It would have to be built into the hull,and the signal would change w the rising/falling of the bow!

 

[stylesabu]

Re: any good ideas on how to avoid underwater objects?

I would make 2 brackets or install 2 transducers with a switch. but if transducer is mounted basicaly paralell to bottom of boat with slight down ward angle to compensate for boat being up on plane. if unit is powerful enough to read 300 ft off bottom, at 30 mph that would give me 6 seconds to pull up motor. I already have a good idea where most rocks are, its just that water level changes.I do realize It might not give enough notice. but my ff is a 700.00 unit should be pretty strong

 

[DaNinja]

Re: any good ideas on how to avoid underwater objects?

I would make 2 brackets or install 2 transducers with a switch. but if transducer is mounted basicaly paralell to bottom of boat with slight down ward angle to compensate for boat being up on plane. if unit is powerful enough to read 300 ft off bottom, at 30 mph that would give me 6 seconds to pull up motor. I already have a good idea where most rocks are, its just that water level changes.I do realize It might not give enough notice. but my ff is a 700.00 unit should be pretty strong

Go for it! I look forward to reading your test results.
(Hopefully not reading about them somewhere else)

 

[roscoe]

Re: any good ideas on how to avoid underwater objects?

So you are going to rig a transducer, which will be 4-8 inches below water surface, and try to aim it forward to "see" an object 300' away, at a depth of 2-20".

Even the best forward looking and 3D sonars aren't going to be able to pick out an object like that at speed.
It will pick up contours, but how it would display on the screen is a different question.

 

[Silvertip]

Re: any good ideas on how to avoid underwater objects?

Here is a little anecdote for you regarding the fish finders, what they see, reaction time and boat speed. Picture this. Three of in the boat, speed at about 30 MPH, large body of water and we are traveling in 75 - 90 feet of water headed to a fishing hole we were directed to by the resort owner. In a heartbeat we went from 75 feet of water to 6. I just happened to glance at the locator seconds before the underwater ridge appeared on the screen. Chopped the throttle and just as quickly we were back in 75 feet of water. Turns out, before the dam on this body of water was installed this ridge ran from what is now an island to the shore about half a mile to our right. I don't care how expensive your locator is, at virtually any speed you will not have time to avoid whatever the locator is showing you. With a down facing sonar, whatever you see on the screen is already behind you when it finally appears on the screen. With a forward facing sonar, whatever you hit will be displayed just after impact. The key to avoiding underwater obstructions is to "know the water". If you don't, you had best study the charts and at least study the route to you ultimate destination before you turn the key.

 

[dingbat]

Re: any good ideas on how to avoid underwater objects?

Furuno and Interphase both make forward /360 degree sonar systems. I don't know the Interphase system but have fished with guys that have the Furuno CH-250 system on their boats. Works great. Can spot fish out to @ 1/2 mile radius from the boat.

A little pricey @ $8,500 once you add installation.

http://www.furuno.co.jp/en/product/marine/document/ch250.pdf

 

[H20Rat]

Re: any good ideas on how to avoid underwater objects?

a transducer pointed forward will not work, period.

A transducer is nothing but a little speaker. The direction doesn't actually make that much of a difference, not as much as you would think. it is NOT an underwater spotlight. So what happens if you turn it to face forward is that you will still get a return from the bottom, just not nearly as strong. What will happen on the screen is that you end up with the normal bottom, but it will resemble really soft mud, as the return is spread out over a long distance. (basically a really thick bottom line) It won't tell you ANYTHING about what is coming up in front of you.

 

[tnduc]

Re: any good ideas on how to avoid underwater objects?

As mentioned above, learn the water you are on. When I lived in Texas fishing the Laguna Madre you could go from 20 feet (in the channel) to 6 inches of depth almost immediately. Needles to say, I've stuck it a few times before I learned the water I fished.

 

[Dick Sorensen]

Re: any good ideas on how to avoid underwater objects?

It's called 'local knowledge.' Ask some of the folks in the area (gas station, launch ramp and around the marina) about the 'virgin' area you're going to be cruising in....get a chart....take a Piloting Course with your local Power Squadron..... slow down...have a spare prop, nut and wrench.....imagine if the Captain of the Titantic had listened to his lookouts!

 

[infideltarget]

Re: any good ideas on how to avoid underwater objects?

Add to that in areas like where I boat, and it sounds like you too OP, the water obstacles can and do change by the minute. Partially submerged waterlogged downed trees can float along just a few inches under the water and be nearly impossible to see sitting still, much less while in motion. You can learn the underwater topography by heart, and still hit an old tree stump. There is just no way to ever actually "know" what is under there. Just like you said, the topography can change drastically with a nearly imperceptible change in water level. So even if you have piloted this section a hundred times with no issues, today may be different. I once sheared a prop in open water, that we (and thousands of others) had driven for years. A tree stump had come loose from the bottom and had been moved around by some recent TVA activity. It was buoyant at around 10" under the surface apparently, and was completely invisible at 20 mph. I was in 100+' of water. I doubt very seriously that even if I had a super sonar, and I had been watching it instead of out in front of me, and it had somehow managed to read this obstacle and transmit it instantly to the screen, that I would have been able to see, understand, and react in time to do anything. Sometimes, you just have to go by the rule of s**t happens, and be prepared.

 

[stylesabu]

Re: any good ideas on how to avoid underwater objects?

Thanks, everybody. I don't really expect to get the results I want. But it won't take much effort to test my theory. i will post my results,good or bad. But it will be 3-4 weeks before its warm enough here.

 

[MultiBeamOp]

Re: any good ideas on how to avoid underwater objects?

Has anybody ever used fishfinder/sonar to spot underwater objects. what if FF transducer is turned 90 degrees pionting out front/forward of boat. Would this be able to read rocks/stumps and other obsticals in front of boat?

Great question... Just this week I was surveying and mapping a reservoir for the company I work for. We have a multi-beam sonar mounted off the bow of a Boston Whaler 17'. I had a guy on the bow watching for obstacles, an operator watching the sonar screen and I was only driving about 4 to 5 knots while navigating at a depth of 12 to 14 feet deep along the shore line. Out of nowhere came a pinnacle that was about 12" below the surface that no one saw coming until it was to late. We damaged the $250,000 sonar and mount. Hence why I'm reading posts about avoiding obstacles underwater. This is very important to us that we find a way to predict and avoid this happening again. The idea you have to mount the single beam sounder off the front of the boat may be good at seeing the angular depth but wouldn't give an image of a pinnacle sticking straight up however this gets my inventor brain going...

...Side scanning sonar exists that can shoot sonar signals off the side in a sweeping motion creating an image that looks like this:

http://www.hydro-international.com/wosimages/2570_267.jpg

the center line is the boat track, the top of the page is the direction of boat travel. I'm not sure why someone hasn't used this technology and mounted something like this on the front of the boat pointing forward and backwards that scans out in front and behind the boat. The side scanning images create a shadow for vertical objects that makes it easy to see not sure if it was mounted up front what the waterfall image would look like for a pinnacle but I'm sure an operator would be able to decipher objects with some practice. I have some contacts in the sonar industry I may bounce this idea off them and see what they can do. -Rob-