The Rapala CD Magnums are among the best lures for fast trolling with a maximum trolling speed over 12 knots for the larger sizes of 18 and 22 cm, but very few people really know how to run them properly or fine tune them.
The first important point is to understand why the CD Magnums “swim” this way. The pressure of water against the metal lip tends to make the lure dive, whilst the line, pulling in the opposite direction, is restricting the depth at which the lure can swim. The conflicting pressures working on the lure create the “Rapala action”. Basically, as the pressure of the line increases, the “lip action” is reduced. More technically, when the surface area of the line in the water becomes larger than the surface area of the metal lip, the action of the lure is “killed”.
SHORT TROLLING DISTANCE
The important feature is to keep the line pressure as low as possible by trolling CD Magnums very close to the Boat. Twenty to 25 meters is almost too much if you want to troll fast. For small bluefin tuna we usually run six CD Magnums behind the boat at an average speed of eight knots. The first lure is only five meters from the transom and the longest is no more than 20 meters, but most of the catches are taken on the shorter lines.
SMALL DIAMETER LEADERS
The relation between the area of line in the water and the area of the CD Magnum’s metal lip dictates that the heavier the line and/or leader, the closer to the boat the lure should be run.
Using 50 lb monofilament (0.7mm) and tuning your lure between five and 15 meters behind the boat, you can easily achieve 10 to 12 knots with a CD Magnum 18, and eight to 10 knots with a CD Magnum 14. If you are trolling fast for mid-size tuna, avoid using a heavy leader, as it will totally kill the action of the lure. Tuna have very small teeth so there is only a slim chance that you will get ‘cut off’. If you want to troll fast in waters with “toothy predators’, your leader should be made of 49 strand cable or wire leader.
It is also very important to have the lowest angle between the line and the surface. By using a low positioned release clip you will reduce this angle and get two extra knots of maximum speed. A basic trick is to keep the rod holder as near the horizontal as possible reducing the line / surface angle to only 20 degrees.
If your rod holder is not moveable, and you don’t have a release clip, an elastic band can be used, but they often break and sometimes damage the line on the strike if the strength of the elastic band is too strong in relation to the line being used. A release clip is a must for high speed trollers.
POSITION IN THE SPREAD
The position of your Rapala lure in the spread is also important. You should avoid running them in the propeller wash as this puts extra pressure on the line. If your rod holders are badly placed, you can adjust the position of your lure by using a release clip. The best place for CD Magnums is parallel and very close to the propeller wash and in between the two washes if your boat is using two engines. The side of the boat can be used for trolling diving lures but you must pay attention to the angle of the line at the rod tip. Most of the time the line will not be inside the top roller, and it might break under the heavy pressure of the strike.
Another trick is to use a strong stainless steel snap to attach the line to the lure. By connecting the line directly to the ring of the CD Magnum you might encounter two problems. First, you will not permit the lure to vibrate enough at the towing point, creating a bad balance, reducing the vibration and the maximum trolling speed. Your lure will start jumping very quickly.
Secondly, the edges of metal lip on these lures can easily cut 50 pound mono under high tension. When a fish starts to circle under the boat, the line, which is under heavier pressure might come in to contact with the edge of the lip, and your fish will be lost.
Some fishermen use ball bearing swivels with snaps. It works, but basically a CD Magnum is running straight and should not spin, therefore the ball bearing is redundant. Most importantly, the ball bearing can create disturbance on the metal lip, inducing bad vibrations and causing the lure to rotate or jump.
I would strongly recommend the use of a stainless steel snap with an appropriate strength corresponding to the size of lure and strength of line.
On a CD Magnum 18, we usually use a 42 mm clip, which is exactly the length of the metal lip. The rating is around 200 pounds, which is very good for a 50 or even 80 pound test line. For CD 14 we use a smaller clip of 36 mm, rating 150 pounds, which is perfect for 30 to 50 pound test line. It is very important to rig your clip with the opening part facing up. Otherwise, the snap can open itself by pressing on the metal lip. If the opening is facing up, you are safe.
It is also very important to check the balance of the treble hooks on the CD Magnums. After a catch, carefully check that all points of your hook are not bent or opened. An out of shape treble hook will create immediate un-balance and make the lure “jump”. If a hook is damaged you have to change it immediately. At the same time check the anchoring points of the hooks as they may become twisted. You will need pliers to put them back perfectly "in-line".
The key is to avoid hitting the lure when trying to kill the fish by hitting it on the head. If you hit the lure with your priest, you might twist the metal lip, creating a “bad swimming Rapala”. The use of a hook remover helps a lot as it doesn’t t pull or twist the points of the hook out of shape like regular pliers.
If your CD Magnum is not swimming correctly, and keeps going to the side or jumping, it means that your metal lip is no longer in line with the body of the lure. You will have to fine-tune the lure by hand. Ascertain the direction in which your lure veers off course, and very carefully twist the metal lip in the same direction. For instance, if, when looking towards the back of your boat, the lure veers to the right and jumps, you have to very gently twist the metal lip clock wise (to the right), as this will produce more pressure on the lip and will bring the lure back perfectly straight. This operation is not easy, as the amount of pressure required is very hard to define. The adjustment of the lip can be less than a millimeter, even on a large lure. On most occasions we over twist the bib, creating the opposite effect by making the lure veer or jump to the left. Never use pliers, as you will certainly over twist the lip. The best way is to use your thumb and index finger like pliers. If you feel that the bib has moved it will probably mean that you have gone too far. The best tune is when you feel as if you have done nothing, and by magic your lure will come back perfectly in line at a very fast troll. You might have to do it two or three times to achieve a perfect tune. The CD Magnums are most effective when the line enterers the water at a 90 degree angle.
The torsion effect must be achieved perfectly in line with the lip. If the metal lip, is bent up or down, it will be very difficult to bring the lure back on track, and you should buy a new one at your favorite dealer.
Go fast, catch fish, and use Rapala CD Magnums…………
Top rated lures
O.S.P VARUNA 110 SP 8.67
Heddon Swim’n Image 8.64
DUO Realis Rozante 8.48
Megabass KANATA 8.42
Imakatsu Riprizer 8.36
Daiwa TD Minnow 8.35
FLT Garison 8.33
ZipBaits Orbit 80 8.27
FishyCat JungleCat 8.22