Topic: testing a polished ducer and crash the towfish

[abraquelebout]

in one topic (http://forums.sideimagingsoft.com/index.php?topic=363.0) i test polished ducer who not working.
i polished it again, isolate the ground by pua varnish and test it again on part of know river.

in begining i have good result in 800 khz, good return on rocks...
polished 800 khz
i decide to go on wooden wreck, suprise i don't see it and the tree behind are not in the screen...

i past on point again at 5 knots and sudenly hit the tree with the towfish, the towfish is crashed
(don't worry, i get 2 other)
i past in point with not polished and i see this:
i think the sound past in wood and i can't see it...
i think abbort the idea of polished ducer

[sonar2000]

Ara...when you get out again (sorry about the tree crash) See if you can turn off the water column and see what it looks like without that showing..
Snapshot and post here.

Chuck

[abraquelebout]

hi
in the test i turn of the water column, it's ok and don't see other thing
in pics i see a litle form of the wreck
i must admit it : i don't see wood
i think i polish ducer a lot ?
now i cut the crashed ducer for a new experiment...

[Rickard]

Abra,
There is an anomaly in the middle of the array (the polished area). Can you see what that is? From the photo it looks like a soldering or an air bubble...
/Rickard

[abraquelebout]

in middle there's soldering, yes there's soldering on the two array left and right, but this ducer work verry well before, it's my first ducer, i make the first towfish with it in begining of 2010

[Roddy]

Abra, Sorry about the tree hang. Did you get the tow fish back?

Tree hang,mud plowing,rock bouncing and harpooning wrecks its all part of the game! Sacrafices to the god's of the quest of knowledge.

Forward scanning sonar helps some.

Roddy

[abraquelebout]

yes, i get back the tow fish in few parts  (i haven't my diving material)
the dyneema cable tract 2 tons, the boat turn arround the tree and finaly i take out the fish.
for my interrest i think polishing a lot the ducer is a bad idea now i begin contruct another towfish for salt water.
hey roddy do you have some film with your "towed cam fish sonar" ?

[Sea-Rover]

Hi Abra,
The thickness of the sonar window is not only protection but also a component
the transducer for the attenuation in the frequency dependence.
If the layer is too thin, too many noises and disturbances to penetrate to the transducer.
It is overloaded and it can handle no longer strong enough signal.
So the image is blurred.
Therefore, should not simply be sanded. Measuring and testing.

In your pictures I've seen differences:

The picture with the wooden boat
In this recording of the hill in front of the boat is something
                 small and it is the tree / branch drawn much more.

Image without wooden boat with a red arrow and oval
                 Above the small hill there is a tree / branch
                  It is the same point as in the picture above but slightly marked.
                  They say that the wooden boat later appear on the sonar image below.
                 

The speed of the boat with the sonar recordings is not the same.
Both objects at the same speed should be roughly the same size.
Maybe not the same driving line.

greeting

[Roddy]

Abra, Yes I have many hours on VHS tape, I will get some of local ship wks put on data cards and try to post in Tow Fish section.
I have a few of the tow fish take n' a mud dive,crashing into wk hulls and my favorite getting hung in a subway car doorway at 110 feet depth, had to use a ROV to recover the tow fish. Roddy