The science behind making your own crankbait lips
http://www.angelfire.com/tn/treetotreasure/lips.html
THE SCIENCE BEHIND MAKING YOUR OWN CRANKBAIT LIPS
Compiled (from the posts from the “Tacklemaking.com” forum) and written by Gene Graham (Lincoya)
Most crankbait makers start by making topwater baits because they don’t understand the science involved in the fabrication and placement of the crankbait lip. Eventually they will try to make a diving crankbait and some will be lucky enough to get it to work right the first time only to have problems on subsequent tries. Others may never have problems. Then there are the few who never seem to get it right and continue to make only topwaters.
Hopefully, the following information can help ALL crankbait makers.
We will start with the mechanics of how crankbait lips work and finish by explaining how to make your own.
Crankbait Lips
All diving lures have a lip or flat surface that protrudes out from the front of the lure at different angles, depending on the type of lure. When retrieved, the lip makes the water flow over the top of the lure, thus creating the diving effect. Different hydrodynamic pressures occur on either side of the lure body, so it swings one way making the water pressure on the other side lower, thus forcing it to swing back. The lure now shows the wobble that represents a swimming fish. This wobbling action will vary according to the size of the lip and shape of the body.
A crankbait's tracking speed, running depth, wiggle, and profile are all affected by the size and shape of the lip, where the line tie is located, and at what angle the lip is connected to the body. Typically a lip is not selected based solely on body design; rather it is selected with a desired action or depth in mind.
The swimming action of a lure is very important. This action is determined by the size of the lip and body shape. Remember minnows should generally have a tight wiggle and wobblers a slow and wide wiggle. The tighter lure actions are generally designed for quicker lure retrieves while shorter or fatter lures like slow to moderate retrieves, and swim with a wide slow wobble.
When considering which size and shape lip to buy or make, evaluate the lip in terms of surface area. The size of the lip depends on several factors: size and shape of the lure, the desired depth of the lure, the action (wide or tight wiggle), and where the line tie will be located. The more surface area, the more water the lip will catch and the deeper it will run. Narrow lips don't move as much water and thus don't dive as deep. Wide lips with more surface area displace much more water and dive much deeper. A deep diver with a big lip grabs the water and forces it down deep. Although these lures get down deep, they are also tiring to retrieve after a lot of casts. Narrowing the lip where it joins the lure body may relieve some of this pressure.
The shape of the lip affects the diving depth, the wiggle ('action') and the lure's ability to safely bounce off underwater obstacles. Round lips displace water equally to both sides, but they displace different amounts of water at different points on the curve. The end of the round lip has very little surface area and doesn't move much water and the middle of the lip is much wider and displaces much more water. This means that the lure will not dive as deep, but will have a wider and slower wiggle.
Round lips are excellent at gliding off of obstacles resulting in less disruption during the retrieve.
Triangular lips also do a great job of naturally deflecting off cover without sacrificing much depth. When they hit an obstacle, they typically just tilt and glide past it.
Rectangular lips basically displace the water equally to both sides and the lure will dive and retrieve straight (assuming it is tuned properly) without much wiggle. Unfortunately, when it hits an obstacle, it will "bounce" back and disrupt the lure's natural appearance. Use these in deep diving lures that aren't likely to hit many obstacles.
Another factor is the angle of the lip. Lips that are cut parallel to the length of the lure (i.e. they come straight out forward from the nose) dive the deepest and have the tightest wiggle. Lips that are connected at a 90-degree diving angle run shallow and have an exaggerated wiggle. Lips that are connected in the middle of these two positions will have medium wiggle and medium diving depth.
Body shape can also make the lure swim in a tight wiggle or a wide slow swaying style. Making the body wider than the dive lip will produce a more erratic action.
The goal of all of this is to select a lip design and position it in a way that produces the desired depth, wiggle (action), and cover-colliding properties. The only real way to do this is to use these rules to experiment with different designs.
Material
Most crankbait lips are made from polycarbonate (brand name Lexan), aluminum, or stainless steel. Each material has its own pro's and con's. Aluminum and stainless steel lips are durable, add flash, produce stronger ultrasonic vibrations, and are easier to "tune" by hand. Unfortunately, they also extend the crankbait's profile, which can negatively affect the lure's appeal. Lexan lips are clear and do not affect the bait's profile, but they cannot be tuned without the assistance of a heat source and they do not emit strong ultrasonic vibrations.
Overall, the Lexan lip's clear profile makes it the preferred lip of many tackle makers. Acrylic (brand name Plexiglas) may also be used (but is not recommended) for making lips. It works fine in warm to hot water. However, in water below 60-degrees it starts to become brittle and may break upon impact with a rock, stump or other structure.
Line Tie Position
When determining where to place the line tie consider the following: The closer the line tie to the body, the tighter the wiggle and deeper the dive. The farther away the line tie is from the body, the shallower the dive and wider the wobble. It takes some practice to find the right spot for the line tie but that comes with experience. Generally the longer the lip the farther out on the lip the line tie should go. On minnow style lures and short lips the line tie can go straight into the body over the lip.
The position of the line tie determines the lip's "positive diving surface". The "positive diving surface" is the area of the lip that is between the line tie and the end of the lip. The "negative diving surface" is the area of the lip that is between the line tie and the body of the lure. The greater the positive diving surface, the deeper the bait will dive and the tighter the wiggle. A line tie placed exactly where the lip meets the body will have virtually no wiggle and will run deeper. A line tie placed at the end of the lip will have a bunch of wiggle and will run shallower.
The advantage of using a through-wire lip design is that the lip comes pre-molded to fit the through-wire so there isn’t a risk weakening the lip with a screwed hole for the line tie. It also handles the force applied on the lie tie during a catch much more efficiently than a screw. With a screw in the lip, the screw acts like a lever inside the lip. When a force of the line is applied to the screw, the screw tries to tilt within its screw hole - thus applying all of the force at a single point on the lip. This weakens the lip.
With the through-wire design, the force is not centralized at the screw point...in fact, the line tie passes under, up, and through the crankbait to minimize the force at the line tie. When a fish is on, the force of the fight is evenly distributed along the entire end of the lip in an upward direction. This diminishes the force at any single point along the lip. With the wire running through a grove in the bottom of the lip it also helps keep the line tie from rotating like screw-in line ties have tendency to do. Another disadvantage of the screw line tie is with tuning the crankbait.
As the screws turn in the hole during a catch, the eye can bend or twist within the hole. This will cause the lure to not run true over time. The through-wire design requires less tuning because it has a little more "wiggle room" and the force is not centralized at the attachment point.
Cutting The Slot
Cutting the slot for the lip can be done at any time during the lure shaping process. However, it is much easier to cut the lip slot into the blank before shaping the lure. This will keep it perpendicular to the blank.
Cutting the slot for the lip is easy with a band saw, but if using hand tools, make sure that the lure is held securely in a vice. Be careful not to squash the timber with the jaws of the vice. Use some scrap leather or even newspaper for protection.
Securing The Lip
Drill two 1/32-in holes in the bottom corners of the lip. These holes will act as glue points and will lock the lip into place. Put epoxy on the top and bottom of the lip. Fill the holes with the epoxy also. Then put epoxy in the slot for the lip and press in the lip. Wipe the excess off of the nose and the sides of the slot.
Making Your Own Crankbait Lips
Use 1/16-inch thick polycarbonate (Lexan) for making your lips. Thicker material may be used and would be preferred for larger lures.
Lexan must be cut with a fine-toothed saw. You can use a bandsaw, scroll saw, coping saw, file or the cut off wheels that are used with a Dremel tool. Use whatever method you prefer to cut the lip out.
Cut the Lexan into strips 3-inches wide then take 3M Super 77 spray glue and stack them 6 deep.
On the top use some masking tape so you can mark around your patterns. Then lay your pattern on the tape, trace it and cut it out. Leave the paper on it when you cut the lip. If you take the paper off and then use a scroll saw or bandsaw to cut it, it may melt behind itself as you cut it. After you cut the lip out use a file or some sandpaper to clean up the edges.
Mark two spots approximately 1/8-inch apart on the lip where you want the tie to be. Take a strip of wire approximately 2-inches long and bend a "U" shape into the middle of it. This “U” should be about 1/8-inch wide. This will be your line tie. Heat the ends of the wire and touch it to the marks you made on the lip. Push the wire completely through the lip. If it doesn't go completely through then leave the wire in and heat the middle of the wire and finish pushing it through. DO NOT push hard on the wire to get it through.
The entire wire is hot and it will enlarge the holes when it does go through. Just apply light pressure and let the heat do its job. Pull both ends of the wire through the holes. Make sure the top of the line tie is fairly close to the lip. If you leave it too high then you may have to tune the lure too often. Bend the ends of the wire back to the end of the lip and cut off the excess. Be slow and be easy when doing this. If you get in a rush and you could crack the lip.
For an alternate method you can drill two holes in the lip (the same size as the diameter of the wire), in the centerline, about 1/8-inch apart. Bend the wire in a U-shape and stick that through the holes. Leave about 1/8-inch above the lip and cut the wire below the lip leaving about 1/8-inch of length. Bend the wire ends 180° opposite of each other on the lip's bottom side. Pull the wire down through the bottom of the lip as far as possible; apply a small amount of 2-ton epoxy and pull the line tie back up on the top of the lip. Slide a small nail or dowel through the line tie to hold it in place until the epoxy sets up.
Take a Dremel tool, a knife, or file and cut a groove one half of the thickness of your Lexan on the bottom of the lip from the holes for the line tie to the back of the lip for your wire to lay in. Depending on the length of the lip, you may need to shorten the wire. Lay the wire shaft into the groove. Epoxy the wire in place making sure the line tie is straight up. Then use Devcon 2-ton epoxy to glue the lip into place.
In conclusion, there are a lot of different pre-fabricated styles and sizes of crankbait lips available that you can buy. But with the above information you don’t have to depend on what is available. You can make your own. This will be especially helpful when it comes time to make that new “secret lure” that you have designed.
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Originally Posted by jigfreak
