Guesstimating Lure Depth - How Deep are they???
 

A common question that comes up is, "How do you determine how deep your baits are running?"

There are many suggested ways to try to determine this along with some charts that were developed. Here's something that I do to "guesstimate" how deep my baits are running...simple yet effective for me. I do this with each set of baits/lure of varing weights since different weights will run at different depths. Also, diffent line types (mono, braid, dacron, etc) make a BIG difference as well.

1. set baits in water and make sure they are running right (hair is straight back and not over hook or line, shad swimming true not sideways, etc), many people just "PLOP" their baits in the water and drop them back
   
   There are a couple of methods to do this...first method...which is the more accurate of the two methods since the line is in the water which accounts for water drag
   
2. let out 10 feet of line while keeping an eye on your baits
   
3. place your rod tip down so it just touches the surface of the water
4. look at your baits and see how deep they are
5. now you know how deep your bait will drop for every 10 feet of line you let out
   
   http://i180.photobucket.com/albums/x...h/DSCF0866.jpg
   
   Second method to do this....
   
6. drop your bait back 10 feet
7. now this time you're going to raise the rod tip up until the bait is right at the surface...if you are using an in-line weight, hold the weight at the surface
8. now you look at how high your rod tip is above the water, this is the depth of the lure at 10 feet back, so again you know how deep the baits drop for every 10 feet of line you let out

http://i180.photobucket.com/albums/x...h/DSCF0864.jpg

This is not an exact science but it will give you a feel for where your baits are running. Also, take into consideration the final placement of the rod in a holder, if you end up placing your rod in a rod holder that raises your rod tip higher than when you gauged the depth, you have to factor that into the approximate depth of the bait...While doing this depth check, you can vary the distance you let the baits back, 20 feet works well too

There's a not so simple math formula you can use to figure out your depth. You need to know the angle of the line to the water, length of line from rod tip to lure and height of rod tip above the water to calculate (I had the formula somewhere when I was messing with my downrigger depths but can't find it). Any math guys on the board?

Note: you won't get an EXACT depth because of the arc in the line once it hits the water but it'll be so damn close that the difference won't really matter.

I always thought the drag from my 40# mono running line created a lifting effect that kept my lures a little higher. I like your ideas though. Thanks for sharing.

I am liking Ralph's approach but as Slayer states the curvature of the line through water resistance throws off the math a bit. As far as the downriggers, I found through use of my depth finder that with a 10 lb weight down "X" number of feet, moving at 3 knots and the lure 30 feet back off of the ball, with deflection in the downrigger cable, the lure was running at the depth the downrigger was set at. That was with a medium umbrella and two 2 or 3 oz bucktails on either side.

All of you are right on all comments...

This is just a very quick, basic, NON-SCIENTIFIC approach that I use for an approximation (guesstimation) of lure depth. There are a few charts that have been developed based on more scientific approaches...There are many things that effect the lures position in the water column.

DISCLAIMER: :D (a little humor here for those that tend to miss these types of things) ... This method does not factor in variances for changes in speed, direction of travel, wind factor, current speed, going with or against current, water density, barometric pressure, lure manufacturer, rod and reel manufacturer, time of day, sharp objects can cut you, hot items can burn you, if ya hat's turned sideways, have gold in ya mouth, and ya pants on da ground!

The way I've always been told from guys who have been doing this longer than I, is watch the fishfinder. If you're marking fish at say 20, or 30 ft, pay attention to which rod they hit. You now know that rod was running about that depth. I know when I've fished with Skip, or Mark (mlag) alot of times we'll mark fish on the fishfinder, and they say, "watch that rod" (pointing towards a particular rod, or "watch the deep rod" etc... and BAM... So basically, takes time to learn your spread set up and where you're marking fish and which rod is catching what you're marking. Hope that makes sense.

I just fish a million rods, cover all depths, and be done with it. It kind of takes the guess work out of it.