Author Topic: How can I tell how close my downrigger ball is to the bottom?  (Read 10719 times)

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Offline Yrral3215

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Hi folks,

Im going to be fishing in Lake Chelan this coming week. Ive been told the best bet for lake trout is to troll with your downrigger ball about 5 feet off the bottom. This is in 250' to 350' depths using a 15# to 20# ball.

Ive done some tests locally in salt water and I can easily see the ball and get a depth reading on it as well as see where it shows on the screen in relation to the bottom.

However, while trolling the ball is well behind the boat - 20 or 40 degrees easily. Im assuming that, because of the blow back, the ball will not actually be where it is shown in relation to the bottom. I have charts to make allowances for the blow back of the balls while trolling. So I can get a pretty good idea of the actual depth of the ball.

My question is - is the bottom depth shown on the unit in 2D mode the actual depth under the boat at that precise point or is it an average of the depth over the entire cone of coverage area or is it the shallowest point within the area of the cone or something else? I will be fishing in areas where the bottom has a significant amount of slope with some pretty dramatic depth changes.


I suspect the guys who are giving this advice are just looking at the screen and keeping the ball what "looks like" 5' off the bottom as shown on the screen. In other words, Im probably way over thinking this :)

Im still curious about how the sonar unit determines the actual depth - especially when the bottom is irregular right under the boat. Any tips or info would be appreciated.

Thanks,

Larry

Im trying to figure out how to keep my gear within 5 feet of the bottom


Offline Trytoofish

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Re: How can I tell how close my downrigger ball is to the bottom?
« Reply #1 on: May 31, 2013, 03:33:02 AM »
here is humminbirds answer

http://www.humminbird.com/FAQ.aspx?ContentId=3681

I have done a lot of salmon fishing and read a lot about lake trout fishing, it seems if they want it they will come and get it, sometimes coming up 50 feet to get a lure, so my thinking is a foot or two wont make a lot of difference.

you may also want to check out Humminbirds / Cannons cannon link. It has a bottom track feature and will keep a cannon downrigger a chosen distance off bottom raising and lowering automatically as needed.
Try Too Fish  Forced To Work

Offline Yrral3215

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Re: How can I tell how close my downrigger ball is to the bottom?
« Reply #2 on: May 31, 2013, 04:57:17 AM »
Thanks for the info! That link explains exactly what I wanted to know.

So if the sonar is using the highest point within it cone of coverage as the bottom, there is really no way to tell how close the downrigger ball is to the actual bottom. This would be especially true in lake Chelan where the bottom is a relatively narrow, steep canyon and you're fishing along one side of the canyon.

Between the blow back error and the sonar reading the side of the canyon as the bottom, I doubt the ball would even be within 50 ft of the real bottom when the screen says it within 5 ft.

Thats good news in one way. Now I can run the ball down to where the screen says its within 5 ft of the bottom with no worries about getting it snagged on something.

Ive got two Cannon Magnum 10 STX riggers now but I dont think they have a way to hook up to the Cannon link. At least I cant find any reference to it in the owners manual. Ive also got the 598ci HD SI sonar and Im pretty sure it doesn't have any networking features either. If I can afford to up-grade down the road, that sounds like a really handy option though!

Thanks again!

Larry
« Last Edit: May 31, 2013, 05:03:23 AM by Yrral3215 »


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