In order to use the chart you have to estimate the angle your line comes off the rod tip and meets the water. When I troll at my usual speed the angle is about 45 degrees. If I go into a “slow” troll it falls off to about 20 degrees, and at “let’s boogie” speed it increases to about 60 degrees.
In the upper left-hand corner of the chart is the rod tip. All measurements (except the depth scale on the left axis) are FROM THE ROD TIP. (my rod tip is 1.5 ft above the waterline). As an example, If my line is at a 45-degree angle and I want my bait at 15 feet deep, I need to let out 23.3 feet of line (remember, that’s 23.3 feet from the rod tip). You can see the 23.3 about in the middle of the page. The number under it in parens (16.5 in this case) is the number of feet your bait is trailing THE ROD TIP, i.e. how far back?
If your rod tip height, line angle or depth requirements are significantly different from mine you can easily make your own chart. Just go to Calculate Angle and Sides opposite, hypotenuse, adjacent of right angled triangle calculator In the calculation box use the drop-down menus to choose "I want to calculate “Hypotenuse Side” & “Adjacent Side” (those sides of the triangle are the amount of line out and the distance back from the rod tip, respectively). In the “Opposite Side” box enter the depth you want to achieve…remember to add the height of your rod tip above the waterline to the depth! The box “Angle q” gets a little tricky because the angle number you’ll enter is actually 90 degrees minus your angle, i.e. to calculate at 30 degrees you enter “60”. The “Angle b” box thankfully will show “30” to confirm it’s the angle you want. I know it sounds confusing but it’s harder to type out an explanation than it is do.
My jigs are usually 1/8 oz with a small plastic, tipped with small piece of cut bait.
I run a 3/8 oz sinker about 18" in front of the jig.
My 4 and 8 lb. lines don’t seem to change the angle much. But the 20 lb line is a huge change: 45 degrees on the 4 or 8 lb. line is easily 60 degrees on the 20 lb line.
Unfortunately I don’t know my boat speed. On my 45# thrust TM my typical speed is set on “25” on a 0-100 scale. Slow trolling is at about “15” on the scale, and let’s boogie is a shade over “50”. It’s just a 12 foot aluminum jon boat so it moves it pretty easily.
Anyone can use the scale; they just need to be able to estimate the angle their line comes off the tip. I’m probably pretty comfortable with it from too many years of carpentry
Ifn I understand it right, the speed is irrelevant. Speed equates to the angle at the rod tip, and the angle at the rod tip and the amount of line out determines the depth. Huh?
Precision Trolling. By Mark Romanac. No Trig., no guessing, all done with 10# test line. Almost every bait is in this book. You can get it on line. Saves a lot of guesswork.
Correct. Speed, line size, bait weight, etc will all effect the bait’s depth…but it’s all reflected in the angle of the line at the rod tip. The biggest eye-opener for me was the effect of line size. The angles of my 4 and 8 lb. lines weren’t much different; but the 20 lb. on the baitcaster was a MUCH bigger angle.
You are making the assumption that the line is a straight line. It generally is not straight as the line bows. Bowing will be affected by speed, line size, and lure size (particularly displacement). I am pretty certain that there is not a 1:1 ratio between displacement size and speed.
Are those variances enough to throw off your predicted depths, I don’t know that one?
Ain’t gotta know math in this bidness…only need to know which account number to deduct fees from and have a good nose for where you’re liable to hide your collateral when it’s time to come load it on the trailer.
Bow would throw it off a bit, I’m sure, but that’s about as well thought out as anything I’ve seen. Bow would increase or decrease the accuracy at long liner speeds, but for spider riggers, that’d be pretty dang close. You could decrease the bow by stepping down the diameter of the lines too…say a 2/10 braid would prolly have very little bow, I’m guessing.
Besides, until one of you knuckle heads come up with a better chart, I’m book marking this one and there ain’t a dang thing you can do about it neither.
I thought about that while making the chart, but guessed that the effect would be within my margin-of-error. Nothing to base that on, except my innate laziness.
Part of it is that my home lake is only 13-15 ft deep and I usually mark fish between 3 and 8 feet. Bowing deflection at those numbers would only be a couple of inches. I fear that I’ve given the impression that I’m trying to be real precise while trolling; nothing could be further from the truth. I just needed a guide to get the bait within the general area. No line counters except me pulling line off the reel and counting "one, two, three…). I do have slip bobber knots at the 7- and 12-foot marks on the line. That really speeds things up because I know that when the 7-foot mark bobber stop is at my rod tip I’m trolling at about 3-1/2 feet; the 12-foot mark bobber stop at the rod tip trolls at about 7 feet.
If you’re trolling at really deep depths like 50-70 feet the deflection is probably decreasing your bait depth by a foot - or three. Maybe more, I really don’t know.
