Lip Size Vs Depth

[rwfleming]

Hey guys , its me again...Mr Many Questions........i did a search but didnt find anything......is there a way to determine the depth the lure will run buy the size of the lip/bill on the crank?

Edited April 15, 2015 by rwfleming

[mark poulson]

For me, no.  

I take a commercial lure that runs the depth I want to match, and use that as a guide for lure size, lip size, line tie attachment, and lip angle.  They spend a lot of money on R & R to get their baits to work, so I "use" their research.

Once I have made a similar lure, and it works, I vary off of that design, to see if I can make something different that still works.

[Vodkaman]

RW - do not concern yourself about the questions. Even if the question has been asked before, it serves a purpose to re-address a question and see if any new ideas come to surface.

This is a very interesting question and was actually one of my pet projects in my early days of TU, when I attempted to write a spreadsheet for designing lures; were you enter in all your parameters and the sheet would tell you if the lure was stable or not, how deep it would swim, how wide the wobble would be and how fast it would wobble.

Everyone warned me that it was impossible, but that only encourages me. Actually some things are possible to predict mathematically, but there are so many variables that have to be taken into account. At the time, my limited knowledge was holding me back, but as my knowledge from testing improved, I found that I did not need a spreadsheet to tell me how a lure would swim, I could just tell.

Predicting the depth is one of those difficult features. This is because there is a lot more to it than the length, shape and angle of the lip. The most important variable in determining the swim depth is the tow eye position.

But, there is even more to it than this; the length, width, shape and curvature of the back of the lure has an effect. The length of the active edge of the lip, combined with the length, width and shape, all these features have an effect.

So, certainly predicting a swim depth with simple spreadsheet maths is not possible.

What you can do, is learn what affect each feature has on the depth of the lure. Think about how a lure achieves depth in the first place. Understanding these details is what experience is all about.

Here is an example:

A deep diver design, long lip, shallow angle with tow eye on the lip. There is an ideal position for the eye for maximum depth. Move the eye forward and the lure swims shallower, move the eye further back and the lure swims shallower.

Analogy - firing a cannon ball. There is an optimum firing angle. Fire too low an angle, distance shortens, fire too steep, distance shortens.

Back to the lure; The eye position is a balance of all the features that I mentioned above. This means that I can alter the swim depth by altering any of those features. Let's say you have a lure that has the perfect balance, then obviously altering anything is going to make the lure swim shallower, but what we can do is think of the change in terms of the tow eye position. Starting off with an easy one:

Shorten the lip length - effectively eye position moves forwards. Swim angle reduces, bait swims shallower.
Lengthen lip length - eye position moves rearwards. Swim angle increases, nose down, but bait swims shallower with a harder thump.
Narrower lip - eye forwards.
Wider lip - eye rearwards.
Thicker lip - eye forwards.
Thinner lip - eye rearwards.
longer body - eye forwards.
shorter body - eye rearwards.
Fatter body - eye forwards.
Thinner body - eye rearwards.
Rounder body - eye forwards.
flatter body - eye rearwards.

This should be enough to get you thinking about the design.

Dave

[RayburnGuy]

Good stuff Dave.

 

Ben

[rwfleming]

i must agree......that is an awesome read.......thanks a ton

[benton B]

my own research showed for 1 inch of bill length you get approx. 7ft of depth.   I find lexan bills run a bit shallow and circuit board bills to run a tad deeper than the projected depth.  

[SLT785]

Thank you Professor Dave. A very eye opening reply. I'm putting it into the " Check back to often" file folder

[Vodkaman]

Benton B - your statement of the Lexan and the circuit board fits the profile exactly. The sharp edge of the thinner circuit board generates more energy for want of a better word.

 

SLT785 and anyone else - I can explain in more details, any of the cases quoted above, if the statements are not making sense.

 

Dave

[diemai]

Very nice write-up , Dave , ....thanks a lot for your efforts .

 

If I may add something to it that I seem to miss , ........which is the general buoancy of the lure body .

 

The lest buoyant a lureblank is , the deeper a given lip will get it down , ...f. e. if you make two identical crankbaits , one of balsa and one of cedar or basswood , you will find, that the balsa lure will not go down as deep , simply because it's high buoancy counterworks the lip's tendency to pull the lure down more than it would with the less buoyant basswood or cedar material .

 

Most likely you would have to add ballast to your lures , ..first to stabilize their swimming , f. e. not to overturn and blow out , ...second effect is a reduction of buoancy ,  which finally lets the lure run deeper .

 

BUT , ........too much belly ballast also does reduce the intensity of wiggle , as it works like the keel ballast of a sailing vessel preventing it from capsizing , .......also a less buoyant timber material would come up with a less lively wiggling action compared to very buoyant material .

 

So, in a nutshell , .....all of the performance properties of a crankbait do not depend on just one of it's construction features like lip size , shape and angle or line tie location , rather more on the entire lot of it's dynamics , which must somehow be made to match one another ........and this is what never does make it boring to me , not even after 25 years of lure carving !

 

Greetings , Dieter

Edited April 17, 2015 by diemai

[Vodkaman]

Indeed Dieter, the upward force of buoyancy is an obvious counter to achieving depth.

 

Not really part of the lure construction, but your choice of line thickness has a huge effect on depth. The cumulative effect of the lines cross section is what ultimately sets the maximum depth that a lure can swim to.

 

Dave

[imagine_studios]

Are there any other variables we can throw in there?

 

This might be too simplified, but it's certainly something to think about if you're as mental as I am.  Make sure you're testing the lures the same way you'll be fishing them.  I messed around with a couple lures getting everything lined up so they ran right where I wanted them.  Like a big dummy, though, I was testing them by casting them out and reeling them back in over a known depth of water with the tip of the rod almost touching the water.  That's all great until you start to troll with them and the trolling rod holders have the tips of the rods about 9 feet above the surface of the water, and of course, that actually matters. 

 

I now test by trolling my lures the way they'll be fished over a sandy area to see when they start to touch bottom using line counter reels to make sure line length isn't messing with me too. 

 

If this were easy, it wouldn't be as much fun.

 

Jason

[Vodkaman]

Jason - Good points about testing how you intend to use the lure, just like you should always test with the hooks and any other hardware attached.

If speed is important in my design, I measure how much line for one crank of my reel. After that, it is not difficult to estimate how many cranks per second you are retrieving. From here, you can calculate speed in meters per second or miles per hour, what ever you need.

Variables - everything can be said to be a variable, as there is hardly anything that you can alter without it having an effect. Tie a feather to the rear hook and it will have an effect.

The secret to lure design is understanding what each change/modification/alteration will do to the performance of the lure, be it action or depth.

Understanding the mechanics of what makes a lure move the way it does, I think is very important to design. Understand this and you can start to get creative in your design and even come up with new designs never seen before.

Google 'vortex shedding' or 'Kármán vortex street'. This is the engine under the hood.

DAve

Edited April 17, 2015 by Vodkaman

[Jordanlures]

Thanks Dave, I now see a whole lot clearer the lure as a whole not as individual components, excellent post , thanks again. David J

[hazmail]

Jason-- One variable I have used for quite a few years is putting a curve in the lip (concave)--On a 8Cm lure (3 1/4") with a lip overhang of 17mm ( apx 3/4'') they will dive to 15' as opposed to the same standard flat lip of the same size and overhang, this will dive to about 8'-10' at best--this is with the tow point on the nose of the lure -Dave would be able to enlighten you on why this is so, I'm not up on "Vortex Shedding" although it really fascinates me.

Dave- Great post's as usual, it's always an education when you get involved .

Pete

[Vodkaman]

Thanks Pete, always a treasure to read your posts.

 

Yes, the forward curvature on your formed lip, increases the power of the vortex and accounts for the increase in depth achieved. Thinking about it, there will be an optimum curvature to achieve the maximum depth, as yet, this has not been explored. The optimum is the forward angle at the edge of the lip. Once the angle is greater than the optimum, power reduces.

 

This needs adding to the list of experiments.

 

Dave

[SW Lures]

Been working on it Dave. As some of you know, I'm working on a lure to reach 20-25' without any assistance other then the trolling of the boat. I have design a crank with a slim profile (width) and a tall height, heavier wood, bill design concave just at about a 1/32" from center and weighted appropriately I hope. I will test a couple of these this weekend in a trolling test.

I also can advise anyone that is new to this craft, read Dave's post somewhere in the forum and his suggestion to a thread of the engine of a crankbait. Very interesting read and has made me rethink what I thought I knew. It actually enhance my thinking, the read made me think deeper into the topic. I have even come to thinking of the bill as the starter of the engine and the line tie as the battery cables. Heck of an analogy right. Lol

I started this because I either could not find the shape or colors scheme I wanted (a typical baitfish in that area). There maybe a reason for this, wish me luck. I'll keep y'all informed on how things goes, maybe in another topic thread.

Take Care; Dale

[Jordanlures]

Dave and Pete, I guess I am a little thick in my understanding here, is the curvature fwd to aft or across the x axis and how deep of a concave on a 3/4" long bill Thanks David J

[Vodkaman]

Here's one I prepared earlier.

 

Dave

[goolies]

Could you predict diving depth of a homemade lure by measuring it's tow line angle on a short fixed length tow line and then comparing that tow line angle to the tow line angles of manufactured lures with known diving depths?

[Vodkaman]

Goolies - No you cannot.

 

What matters is the angle that the lip swims relative to the tow line. There is an optimum angle for maximum depth. This angle is determined by the balance between the water forces acting above the tow eye (on the back of the lure) and the water forces acting below the tow eye (the lip).

 

Variables that affect this balance are:

 

Above tow eye - body length, body thickness, body curvature, body depth.

 

Below tow eye - angle of lip, length of lip, width of lip, thickness of lip, edge of lip, and as we have just discussed, the cross section shape of lip.

 

This does not mean that all these parameters have to be just so. You can change one parameter and compensate with the adjustment of another parameter.

 

Dave

[Jdeee]

I always found that big lips impede depth.

[Jordanlures]

Picture is worth a thousand words thanks Dave 

[goolies]

I'm not questioning what makes one lure dive deaper than another.  That's a given.  I'm asking if I build a 5-1/2" sick bait can I estimate it's diving depth by comparing it to another stck bait?  Specifically, comparing tow line angles.  Shouldn't a steeper tow line angle indicate a deeper depth?

Edited October 8, 2015 by goolies

[Vodkaman]

Goolies - Imagine that the lip is so large that the lure swims 90 degrees to the tow line. There is nothing to drive the lure downwards and the lure will swim at around 3'. As the angle decreases from the 90 degrees, the lure will swim deeper.

 

Now imagine a bait that swims at zero degrees to the tow line. Again, there is nothing to drive the lure down. As the angle increases from zero, the lure will start to dive deeper.

 

Somewhere between the two is an optimum angle that gives maximum dive.

 

I think comparing the tow/lip angle is a good indication of depth. Not an easy thing to do though, but I do agree.

 

Dave

Edited October 8, 2015 by Vodkaman

[JRammit]

Heres a good question

Has anyone devised a way to test running depth... Besides the obvious use of clear water in a swimming pool

I was thinking of rigging a small slip bobber above the lure, adjusting the stop knot every cast until the lure no longer pulls it under... But i think the arc in the line (caused by the bobber) would restrict the dive

Any other ideas??