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Bill Designs: I'll show you mine if.... (long!)

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#1 BobP


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Posted 14 August 2005 - 10:04 PM

I see alot of TU queries on crankbait bills but not much specific design feedback. I get my body/bill designs by trial and error and/or by usiing a factory crankbait as a base model. I think most other builders may do the same. Why exactly does a particular bill work great and another not at all? I don?t know all the reasons but trying variations on a basic design has generated a few tentative conclusions. Here they are for what they?re worth, and I hope other builders will chime in with their thoughts and specifics regarding their bill designs and why they work on their crankbaits. There are times when I want a change from the "same ole" with a different body shape and bill that will run with a different wobble or at a different depth. I wish there was better info about bill design, beyond the basic principles of ?longer goes deeper? and ?wider bill, wider wobble?.

Here?s the data and some observations on my best crankbait (and its bill).

Crank: This is a thin, flat sided, medium shallow runner (see pic) with the following stats: 10mm wide, 65mm long, max 25mm tall, tapered tail, basswood, .33 oz without trebles. The ballast is in front of the belly treble and gives it a head down attitude and a slow rise when paused. It has a tight wiggle, a good amount of thump and runs 3-4 ft deep. Cranks with tight action are popular in cold water but I think they work great year round. I carved rather crude body segments into the bait and painted it ?summer craw? pattern to give the bass a different look. This past June, I caught a 17lb, 5 fish limit on a very tough clear water lake in 2 hours. Too bad it wasn?t a tournament! Maybe that was a fluke but I don?t think so because the crank has continued to catch good bass since then.

Bill: Fan shaped, exposed length (measured under the bill) 17mm, max width 18mm. Bill angle (measured from a horizontal line between the nose and tail) is 34 degrees.

Comments: I used .031" (1/32?) G-10 circuit board because it is the thinnest material I know with excellent rebound and hardness. Circuit board also goes by the name of G-10, Micarta, FR-4. It is a high-pressure laminate of epoxy over a fiberglass or linen substrate. It bounces off cover sharply and it?s super thin, which makes the bait dive a bit deeper than it would with a thicker material like polycarbonate or plastic. It's easily cut and shaped with tin snips and a Dremel sander. The fan shape was derived from a Flatshad, a popular commercial crank among tournament anglers, plus some prototype bill experiments. I upsized the bill from the Flatshad because this crank averages .03 - .04 oz heavier due to an epoxy clearcoat and more ballast. I figured extra bill area was required to get an equivalent action. The .031? brass wire line tie is on the bait?s nose, touching the bill. I feel this placement is important to get max thump. I was leery of such thin soft wire for the line tie but so far, 15+ bass up to 5 lbs haven?t deformed it, so it seems OK.

I?m happy with this bait but feel it still has room for improvement. I suspect more bill angle or a placing the ballast higher inside the bait might be interesting. Would more bill angle generate more thump? Wider wobble? More or less control? How about the ballast placement? A larger balsa variant of this bait with a proportionally larger bill, placed slightly lower on the chin at about 45 degrees, had enough thump to numb my left hand after hours of fishing. That was TOO much vibration (never thought I?d say that!). I don?t have a Cray mainframe to perform hydrodynamic calculations like they do for atomic submarines. Help me out here!