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Hi folks, I have a question, I have sunk several crappie cover buckets using PVC for the limbs. I choose this type of material because it wont rot out should last forever but the problem I have found is my side and down scans will not pick up pvc stake beds. Anyone else found this out? I read somewhere this problem is normal when using the pvc for cover it doesnt show up on sonar?
Any thoughts?
Thanks Steve
Sonar detects differences in density of structure vs the surrounding water ...
PVC (when filled with or surrounded by water) has a very similar density as the water itself ...
Some sand the PVC to accelerate algae growth on the PVC ...
Some trap air in the PVC to create the different density factor ...
Others use PVC exactly for the reason you stated = it's harder for others to find ...
Rickie
Thanks Rickie, good explenation. I think I`ll add some wood or trap air in them to help me re-locate. You did say traping air may just be the answer?
See I gps them but where I put them at times there is current and somethimes, I think it could move or knock them over so finding them again would be very benifical to me.
Thanks Again,
Steve
PVC at the base of a drop.
Attachment 253944
Air has a different density than water ... which is why the fish's air bladder is believed to be the contributing factor of fish showing on Sonar ...Quote:
Originally Posted by steve telinda
Rickie
Rickie, the picture you sent reggarding the structure being pvc, is that one with air traped inside like you suggested?
If s0, I could seal both ends and hopefully have the same readings once sunk?
Thanks again
That pic is Justin's ...
I'm not sure if he trapped air inside his PVC structure ...
Rickie
This is one good reason to have GPS it lets you know that you are within about 3 meters from where you dropped the fish structure(PVC, brush, wood,etc.) Then you just go back to that concordance and look for the fish that show up around you structure on sonar to pinpoint where to fish it.:twocents
Rickie ... I've always heard that as well, BUT ... then how does one explain this DI screenshot :Quote:
Originally Posted by rnvinc
Attachment 253973
seeing as how it shows "fish" outlines and not simply air bladder density differences ??
Could it be the different megahertz frequencies between 2d & DI/SI ?? :scratchhead
And as a side note : if you cap the PVC pipes to trap air (or even add wood) ... wouldn't you also have to use more weight to hold them down, to compensate for the buoyancy of the air/wood ??
Yes I asume I`ll add the weight to hold em down. Im going to try it just to see, Sure can`t hurt.
I`ll let you know if i can see them on side and/or down imaging.
Air isn't the only density difference factor that Sonar detects ...Quote:
Originally Posted by CrappiePappy
There are other substances besides air that also have a different density than water (fish flesh, scales, structure, bottom composition, etc) ...
Air would be in the "less dense" category vs water ...
Flesh, scales, structure, etc would be in the "more dense" category vs water ...
Either side of the "vs water" density would be different than the water density itself ...
Rickie
OK, I got all that !! So, if a 2d sonar beam was restricted to a narrow fan shape by blocking the front & rear of the cone ... would/could it produce a similar image as the DI ?? It wouldn't, would it ?? But, is it the shape of the crystal or the frequency being transmitted that determines the image ?? Or am I comparing apples to oranges, here ??Quote:
Originally Posted by rnvinc
The shape of the piezo only affects the beam shape ... round piezoes create cones / bar piezoes create slices and fan beam shapes ... (size affects beamQuote:
Originally Posted by CrappiePappy
Angle) ...
If we were to connect a bar shape piezo to the 2d wire channel = we would have a fan (or slice) shape 2d Sonar beam ...
Fish echoes from this scenario would be painted in the 2d image as a colored dot (depending on 2d palette choice) ... just like a DI fan beam paints a white dot ...
A "dot fish echo" vs an "arch fish echo" we know is simply created by target time in the Sonar beam ... a fan beam doesn't allow the target to be pinged as many times ... and the few times that target is pinged in the fan (or slice) beam, the target is basically the same distance from the xducer (or negligible difference anyway) ...
Now to expand this scenario some ...
If we increase the frequency of this scenario's 2d fan beam (to 455kHz or 800kHz) ... we may even see some these 2d fish echo dots that look like fish ... but colored (depending on 2d palette choice) ...
Basically ... imaging is imaging because of higher frequency and fewer pings on the target ...(and processing the returns into several shades [by strength of return] of the same imaging palette color choice) ...
Rickie
I HAVE PUT PVC IN LAKE AND FOUND SOME IN IT ALSO ,I CAN SEE IT ON MY UNITS,859 AND 1199,I SAW IT WHEN I FIRST PUT IT DOWN,SAW IT A WEEK LATER AND SAW IT A MONTH LATER AND SAW IT PASS WEEK,DID NOT TRAP AIR IN IT ,NO ALGAE ON IT,AND DID NOT SCRATCH IT UP,IT IS A MATTER OF SETTING YOUR UNIT UP RIGHT TO SEE IT,HOWEVER YOU DO NOT NEED TO SEE IT IF YOU KNOW WHERE IT IS ,JUST SEE FISH AND IF NO FISH ,KEEP GOING
:ThumbsUp:ThumbsUp
Thanks, when you say setting my unit right to read the pvc do you have a tips on doing that? I have Lowrance HDS units.
The reason i want to make sure I am on the cover is because I put the pvc cover in an area with current,
Which Lowrance?
I have the hds 9 touch gen 3 on the dash and a hds 8 on the front hooked to trolling motor
If you have current, do't expect your stuff to be where you dropped it if the water has much depth. Trust me.Quote:
Originally Posted by steve telinda
If your structure scan transducer is installed correctly you should be able to run the units in auto and see the PVC. If it's small stuff it may be harder, but I don't know for sure. On almost all of my PVC beds I can see the weights.
I have a few beds in the main lake on Lake Barkley that have stayed in place. Having said that they'll probably be gone when I go to fish them this winter. LOL
Justin, i fish Ky lake the Jonhathan creek area how is Barkley compared to Ky lake regarding crappie?
Steveo