Searching and Running a Line?

[Bob DBF]

Well, sort of. Some techniques do work better than others, depending on the situation.

I did reinvent the wheel a couple of times when doing my project, I could blame it on narcosis I guess, but what looks good on dry paper sometimes falls apart when wet. I learned a few things I wasn't planning on during those dives.

The silt was quite a teacher. It didn’t take us long to work on non silting kicks, although I never could frog kick worth a crap. A line in it or a couple of crawdads evading us could drop the viz to zero in a significant area, which could make the area searched more haphazard. We gave up on the circular search, between the line hitting the bottom, it was not flat, and crawdads silting the next search area, and an occasional screw up on our part, we switched to out then move over and back.

Another issue was lights, our regular dive lights were ok when everything was going fine, but they were crap in a silt out. I finally converted an old DarrellAllen light to help.
Darrell Allen Light Rebuild Mod I


Bob

 

[rob.mwpropane]

I have no certifications in this, am I in trouble? Is this like giving medical advice without a license?

Yes. I've just contacted the appropriate authorities, they're on their way.

In all seriousness I appreciate everyone's feedback. It helps to hear what people do in the real world.

The bottom is very silty, so moving the line and dragging it through might not be the best. I like the wheel spoke idea, although that would take longer. For smaller structures / cars / whatever, I could see the circle method working at least for 25' or so from that point, and then maybe back to the wheel spoke idea.

Regardless it'll be GREAT to run a reel and to find my way back to where I came from.

 

[Bob DBF]

Regardless it'll be GREAT to run a reel and to find my way back to where I came from.

The big advantage for us was returning to the bridge abutment, which boats avoided, to surface, rather than ascending in open water under the span. It also minimized the surface swim. We only did the direct ascent a few times, once was to measure our progress.

If you can leave your lines it will greatly speed your mapping, if that’s the objective.

 

[tursiops]

What are the rough dimensions of the area you want to explore/survey/map?

 

[rob.mwpropane]

The big advantage for us was returning to the bridge abutment, which boats avoided, to surface, rather than ascending in open water under the span. It also minimized the surface swim. We only did the direct ascent a few times, once was to measure our progress.

If you can leave your lines it will greatly speed your mapping, if that’s the objective.

I can leave a line, what's a good type of line to leave that won't fall apart (and is cheap!)?

What are the rough dimensions of the area you want to explore/survey/map?

It's about 650' x 300'.

 

[The Chairman]

Some techniques do work better than others,

I find the circle search to be bulletproof, but look at how many think it's flawed. It's a personal preference as to what works best for you. Dive and let dive. Search and let search!

 

[tursiops]

I find the circle search to be bulletproof, but look at how many think it's flawed. It's a personal preference as to what works best for you.

Ever tried a circle search in low viz with a bottom that has snags sticking up? Don't even bother. It is not a personal preference, it is a physical impossibility.

 

[The Chairman]

Ever tried a circle search in low viz with a bottom that has snags sticking up? Don't even bother. It is not a personal preference, it is a physical impossibility.

I've done plenty of these and the snags could be pretty interesting. One was the stock of a broken shotgun. I usually use Moonie when teaching a class. He's been the snag on a few occasions.

 

[Bob DBF]

I can leave a line, what's a good type of line to leave that won't fall apart (and is cheap!)?

Home Depot Masons braided nylon fluorescent green or yellow, in a bright light you can lose white. You have to tighten it up over time as it stretches.

I find the circle search to be bulletproof, but look at how many think it's flawed.

I don’t think the circle search was flawed, it was just not optimal for the search I was making, which was for objects roughly off a straight line.

For locating an object dropped from the surface I would not think of using another method to find it. It’s been especially good to me for a Braille search in zero viz.


Bob

 

[tbone1004]

What about in salt?

A little OT but what about smb's? I usually lay mine out, but if I don't have to then forget it...

As far as the searching goes I'll just have to see what works. I don't think that circles would be an issue because there's no current, but no harm in trying. I like the spoke idea as well.

Thanks guys, I'm sure it'll be an S show but at least I'm on the right track...

nylon is not the ideal fiber to use in salt water because it will absorb the salt crystals into the line and as it dries, will actually abrade the fiber from the inside. Dacron/PET would be better, but the break strength on this stuff only matters for things like lift bags so you won't have any practical problem with it. I would make an effort to make sure it's soaked properly though