Actual Dipsey Diver-Downrigger Depth


Capt.Jimmy Samia


Knowing your actual dipsey diver-downrigger depths in real time while trolling is paramount to maximizing your fishing success. Would’nt it be nice to have a way to just look at your outfits whether dipsey divers or downriggers while they are deployed and know within a few feet where they are actually running below the surface? Well, there is and it”s basically free!

A while ago we included an article on our website called “Do you know where your stuff is running” which outlined some very good insights on how to figure out actual dipsey diver-downrigger depth when trolling on Lake Ontario. Although we still use a lot of those methods to determine our actual dipsey diver-downrigger depth today, we finally figured out an easier way that works in real time and in any direction under all conditions. It all goes back to high school trigonometry. Yup! Good ole high school trig.

For figuring out the actual dipsey diver-downrigger depth, we will need to use only two trigonometric functions. For dipseys, we use the sin function and for downriggers we use the cos function of the angles created by these apparatuses as they enter the water to determine actual dipsey diver-downrigger depth. Here’s how it works for the dipsey. If we look at the angle created by where the dipsey line enters the water and the surface of the water, we can take the sin of that angle and figure out the opposite side of that angle which would be the depth that the dipsey is running at. For the downrigger, we will use the cos of the angle created by where the rigger cable swings back from the rigger pulley at the end of the downrigger arm and calculate from there.

Working out an example for an actual dipsey diver-downrigger depth for dipseys would go something like this. Let’s say that we wanted our dipseys to run down 80 feet in the column, actual depth. We look at the angle created by the dipsey line and see that it’s 20 degrees (angle “A” in diagram below). Using our smartphone we look up the sin of 20 degrees and see that its value is .34. Remembering that the sin=o/h where o=the actual depth(opposite side in diagram below) of the diver in this case and h= the hypotenuse or in this case the amount of dipsey line out, we can then figure that  .34=80/h  remembering that h (the hypotenuse in diagram) = the amount of line we need to let out on the diver. So, solving for h we get h=80/.34 which equals 235 ft of dipsey line that we would need to let out to get the depth we wanted of 80 ft in the column.

dipsey diver-downrigger depth using trig functions

use sin of angle A for dipseys

Working out an example for an actual dipsey diver-downrigger depth for downriggers is also quite similar except we are going to use the cos function of the rigger cable angle as it comes off of the end of the downrigger(angle B in diagram). Lets say we want to run our downrigger ball down to a depth of 80 ft in the column. We estimate the angle of the rigger flare (angle B) to be 15 degrees . We look up the cos of 15 degrees on google and see that its value is .97. So in this case cos B=a/h where a=the adjacent side to the angle or in this case the actual depth of the rigger ball, and h= the hypotenuse or in this case the amount of downrigger cable we need to let out. We find that   .97=80ft/h  solving for “B” we get B= 80/.97 which equals 82 ft of line we would have to let out.

actual dipsey diver-downrigger depth using cosine function

Use cosine of angle B for downriggers

Using trig functions to determine actual dipsey diver-downrigger depth may seem a bit daunting at first, but once you get used to using them, they can really save the day. Granted, we use a Fishhawk X4D on our downrigger which gives actual depth of our downrigger, it’s still nice to know that you can use some high school math to verify its accuracy or reverse engineer the angle of the cable (angle B) to get the feel for it. There is also newer technology on the market today that is supposed to give you reel time underwater feedback of downspeed and depth for copper lines,riggers,and dipseys called Smart Troll , but it’s pricey. It cost over a 1000.00 dollars. It’s newer technology and the jury is still out on it overall performance.

We used trig functions this past summer to determine actual dipsey diver-downrigger depth and it really helped us to dial in on the fish. The temperature was really deep that particular day and our dipsey divers were not getting bit. in fact, the whole charter fleet was starving for dipsey diver bites. Because of the deep temps and wicked underwater currents, we knew that we would have to run mag divers to get down to the fish. The temp was down 125ft. We noticed that the angle of the dipsey line to the water was about 22 degrees while trolling east. Using our formula we took the sin of 22 which was .37, so to get down to 125 ft in the column we calculated .37=125/h where “h ” is the hypotenuse or the amount of line we had to let out which was 125/.37  or 338 ft of line out. We ran our dipseys out to 340 on the counters and don’t you know are dipseys started firing. When we were trolling in the opposite direction, in this case west, the angle on the diver was about 30 degrees ,so …sin of 30 degrees =.5  then 125/.5=250 ft of line out. We then starting catching fish on the dipseys going west as well even though it took  90 ft less of line out.

To those of you who got through this article on actual dipsey diver-downrigger depth and understand it, give this a try next time you’re out on the big pond pulling dipseys or setting downriggers. It really does work. For those of you who missed those days in high school and are still struggling to wrap your head around this, we suggest brushing up on your high school trig, or just go back to guessing or experimenting to get your dipseys to go. As always, you can read more about Lake Ontario info and tips on our website

Here are a few related Blog posts worth the read:

Rigging Dipsey Divers

Setting Up Dipsey Divers