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CarverGLX

How Much Weight Starting Point Calculations

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Hello all,



There seems to be a lot of questions about how much weight
to add to a bait. There are several methods described in other posts dealing
with this issue for a “new” bait. I have a system for developing consistency through
a line of the same bait as I’m sure many TU members have. My system is in no
way perfect but gives me a good starting point. This is my process.



I try to build lures by a repeatable process. I also use
balsa wood. These two things don’t always agree. Different boards are from
different trees and therefore have different densities that will affect the
action of the bait and amount of lead that should be added. I have designed a
system that allows me to come up with a reasonable starting point for a new
lure by deciding how much weight to add.



Whenever I try to decide how much lead to add to a bait I
start out with math. I take measurements from previously successful baits
(weight, vol, density,…) and use equations to get a rough idea of where to
start. These calculations in no way are absolute. The different shapes of baits
and amount of surface area that is exposed to epoxy or sealant also affect the
weight and final volume of the bait. Other factors that influence this include
line ties, hook hangers, lips, hooks, split rings….. and the way that many of
these are attached to the bait. These equations are meant to be a rough
estimate of how much lead to add in the construction.



When I first get a board I place it on a kitchen scale and
weigh it. I then record the weight on paper and on the board as well. I then
use the dimensions of the board and the weight to calculate a density for the
piece of lumber using the equation Density=Mass/Volume. (see attached volume
table) Using mass values in grams and volume values in centimeters allows me to
see what the density of the board is in relation to water (density=1g/cm^3).



When I create baits I use a router. This allows me to be as
repeatable as possible. I construct a bait by joining two halves together to
form a bait with epoxy. I try to be as consistent as possible in the joining of
the baits by the amount of epoxy I apply and always press the baits under a set
amount of pressure while drying.



Once the baits are joined I weigh them on a powder scale to
determine their mass. After taking 5-10 measurements I calculate an average mass
for the run of baits. By doing so after the baits are epoxied together allows
me to be closer on the end product than weighing them beforehand. This negates
some of the error encountered in gluing and from half to half.



After the average mass is calculated I determine the volume
of the lure body by using the known density and mass values. By comparing this
volume to previous baits I can get a rough idea of how much weight should be
added to a bait. (see area of drill bit table, multiply by depth of cavity and
gr per cubic centimeter for a rough estimate of mold size needed)  I then take the amount of weight calculated
and install it and finish a lure with all the necessary components  and coatings and test it. Sometimes I don’t coat
the lure for the sake of speed. From the test I make adjustments accordingly on
the amount of weight needed, hook size, line tie position, bill angle……



Once all this has been done for a particular style of bait
you can adjust the amount of weight needed by recalculation of the density.
Then you can adjust the weight accordingly to the density of a new board to get
the same rate of rise in the lure. The action will be somewhat different as the
distribution of mass in the lure is slightly different but usually the
difference is negligible.



By always recording all the measurements and calculations it
is possible to get very close to a run of baits from the past that have turned
out to be very successful. This can then be followed as a recipe. I’m sure this
is nothing new but thought some of the members might benefit from an
explanation of what it is to be repeatable and how to do so. The process, once
again, in no way is perfect (bits have different points, walkout,....). It is a good reference and starting point for me however.



Good Luck,



CarverGLX



 

Volume Table.PNG

Mold area by drill bit.PNG

Volume Table.PNG

Mold area by drill bit.PNG

Volume Table.PNG

Mold area by drill bit.PNG

Volume Table.PNG

Mold area by drill bit.PNG

Volume Table.PNG

Mold area by drill bit.PNG

Volume Table.PNG

Mold area by drill bit.PNG

Volume Table.PNG

Mold area by drill bit.PNG

Volume Table.PNG

Mold area by drill bit.PNG

post-22736-0-39687900-1387147334_thumb.png

post-22736-0-07785500-1387147398_thumb.png

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Whew!  Good description.  I use a simple system, basically working toward a target finished weight for each crankbait style that I build.  I base the target weight on past experience and/or the weight of a commercial crankbait that I'm copying.  I weigh the shaped and sanded body of the crankbait before I start applying finish, then weigh the lip and all the hardware.  On a "standard size" 2 1/4" bass crankbait, I estimate that the finish will add .03 oz to the final weight of the crankbait.  Those weights added together, then subtracted from the target weight gives me how much ballast is needed.  I typically get within .02 oz of the target weight when all is said and done.  Of course, the estimated weight of the finish can be unique to a particular builder;  mine is based on the baits I've built over the years.  And if you don't keep notes on the weights and build processes of your crankbaits as you build them, every bait is a new adventure in ballasting and you'll need a more involved method.

 

Note:  I use target crankbait weight without treble hooks and split rings.  If your target weight includes hooks and rings, you must remember to also add their weight into your formula too. 

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I have tried a similar method, but since I'm doing baits by hand, they vary more than a production shaped bait. Thus these variances overcome the ballast reproduction.

The other difficulty to consider is that a higher density of wood would (pardon the pun) be evenly distributed throughout the bait. The added ballast to compensate for a lower density would be necessarily in the ballast location. Thus the two baits, with exactly the same volume, shape and weight would still not necessarily have the same action.

One option to compensate somewhat for this would be to weigh a run on baits in grains pre and post epoxying. This should give you an average weight of the topcoat for a given shape. You could then use an extra coat or two as needed to adjust the weight distributed throughout the bait. Of course this would not. Be exact either, as this added weight, while evenly distributed, would be at the very outside, and thus working on a longer lever arm, creating more torque. This would suggest to me to go a little lighter than true equal weight in topcoat.

Another idea directly relating to this would be to chose the lighter baits for foil finishing, to same effect.

All this is currently moot for me, as I currently don't do production...

Clemmy

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All of us who have built quantities of wood baits through the years come to understand how hard it is to exactly reproduce a bait to a standard that guarantees each one will have exactly the same performance.  You really have to get persnickety with materials, equipment setups, and custom jigs to come close, and hobby builders willing to go to those lengths are rare - in fact, even custom builders often don't attain a very high level of repeatability.  As a hobbiest, I accept some variability in a batch of baits if I can then test them and determine how the variability affected the baits performance.  But small differences that are hard to detect can make a noticeable difference in performance, so it can be frustrating.  But interesting.  

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All of us who have built quantities of wood baits through the years come to understand how hard it is to exactly reproduce a bait to a standard that guarantees each one will have exactly the same performance.  You really have to get persnickety with materials, equipment setups, and custom jigs to come close, and hobby builders willing to go to those lengths are rare - in fact, even custom builders often don't attain a very high level of repeatability.  As a hobbiest, I accept some variability in a batch of baits if I can then test them and determine how the variability affected the baits performance.  But small differences that are hard to detect can make a noticeable difference in performance, so it can be frustrating.  But interesting.  

 

A guy told me once that he really liked the look of my baits (hand carved) but you need to be a "real craftsmen" to be able to make them all the same. Sounded like a challenge.... and here we are.

 

I'm generally within about 4 grains+/- on baits from the same board....Having a mistake that requires sanding gives me fits. I dont want to have to touch it if I dont have to. It's going to happen though.

 

BobP,

I agree most hobby makers wont go through the trouble. You can't even think of all the trouble to begin with. Fun figuring out all the problems and talking on here too.

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I just use Archimedes theory of water displacement. It's quick, simple and has proven invaluable when building suspending baits. If you want to test the accuracy of your method try building a few suspending baits. You will see just how much difference there is from one piece of wood to the next. Even if two pieces of wood are exactly the same size, shape and weight there can still be a difference in the buoyancy.

 

Ben

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I just use Archimedes theory of water displacement. It's quick, simple and has proven invaluable when building suspending baits. If you want to test the accuracy of your method try building a few suspending baits. You will see just how much difference there is from one piece of wood to the next. Even if two pieces of wood are exactly the same size, shape and weight there can still be a difference in the buoyancy.

Ben

True. It's not perfect. Even in the same board I fall in a range of +/- 4-5 grains per blank. Other things like epoxy getting thicker as it sets effect it too. It's just a good starting point for me.

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I don't know of any calculation that is perfect from one bait to the other because of the things you listed. The best we can hope for is to find something that is easy, works for us and has an allowable discrepency range. Looks like you've done that. :yay:

 

Ben

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I don't think any bait I've made were exactly alike, but that is what my friends and some of the guys I use as "test" pilots say. There as close to the same as I can make them, since they're made one at a time. The only thing that is exact, is the shape while in blank form, but they weigh the same, except when while checking the ballast. If they list to one side or the other, then the weight changes some, but only then. I try not to worry about the things I have no control over, but I think that would take the fun out of building customs. Just my .02.

 

Jerry

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I am fairly new to lure making, and make very small batches of lures. When I go to make a suspended (or slow sinking lure) I also use Archimedes theory of water displacement. But to do this I place a tray on my scale and zero out the scale. I then fill a container full of water until it is just shy of spilling out. I then place this container on the tray and begin by placing my hooks in the container, and then dip in the bait until completely submerged. This will cause water to spill out of the container into the tray. Upon removing the container from the tray the leftover water in the tray is weighed, and that will be the desired final weight of my lure. I then weigh my lure body, components, and then compensate slightly for paint/epoxy, and then use the difference between these two weights to determine the amount of weight to add to my bait. It is a tad bit time consuming but it has been fairly reliable when trying to make my jerkbaits sink as slowly as possible. 

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I'm going to attempt a couple suspending jerks. I do this is a fun hobby and build using pvc mostly. Can't I just build the lure, drill a couple holes for ballast and add ballast until I get the desired suspending action in a test tank? I know I'll have to add hooks etc when testing but this seems to be a bit less time consuming and most importantly, I don't have to do any math!

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Frog that will work but you'll have more trial and error with that. I think they were referring to taking some of that out for repeatability. Now as a beginner I'm doing exactly what you are doing and that can be most the fun and frustration for me at least. I'm a stay at home dad and work nights so my time to work on lures is slim so I appreciate the info about taking specs. It will definitely help so thanks guys for the great info!

Jared/Snapping necks

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Sure you can! Actual tank testing is the gold standard of balllasting. Of course, for suspending baits, it is only accurate for the temperature of water you test the bait in. And you have to choose at which point in the build you will do the test.

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CarverGLX,

You must be an engineer.  The only other person who I know who it that detailed is Vodkaman Dave.  Hahaha

 

FrogAddict,

I also use PVC, and this is what I suggest you do.  We have the advantage of consistent weight in our material, and the fact that it's waterproof lets us float test without any sealing, which is a huge bonus for me.

Make a test lure and learn what each step of your process does to it.

Try shaping it and adding your line tie and hooks.  Then put your lure into a pail of water, and add lead wire, split shot or egg sinkers to the front hook's tines ( rear, too, if needed) until you get your bait to sit/float/sink/suspend the way you want it to.

Then weigh the test ballast weight, duplicate it with whatever you use for ballast (I use 1/4" lead wire) and add it to your lure.

Subtract between 1 and 2 grams from the ballast you use for your paint and topcoat, depending on lure size and the finish you use.

Once you've completely finished the lure, you'll be able to tell how well your ballast adjustment worked.  For jerkbaits, a slow sink is okay, especially in cold weather/water, and a slow riser can be adjusted to suspend on the water with either lead wire around the shank or suspend dots.  You can add split rings to add weight, too.  Changing hook sizes also will affect how a lure suspends and hangs in the water.

The line you use can also change the sink/float of a jerkbait, so remember that when you're out on the water, and have several different reels with both thin and heavier flouro and one with mono, so you can change the bait's fall rate just by changing lines, without altering it's ballast on the water.

I just went through my jerkbait box and test floated all of them again.  I label my plano compartments suspending, sinking, and floating, so I know upfront what I'm tying on.  Plus I used a fine point sharp to mark their foreheads with either SP, S, or F.

I don't have any fast sink jerkbaits, so I know that S means slow sink.

In colder water, which is more dense, slow sink will suspend sometimes, too.

I hope this helps.

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Great thread. When I read the first post, I expected to see a barage of negativity. I am so glad I was wrong.

 

I have nothing to add except to say that I have tried lots of methods and like the Archimedes the best. Like Bob said in post No2, it is all about writing the information down for future use. I use spreadsheets on the computer for all my notes. It is clean, tidy and you can get a bit fancy by building in a few simple calcs too.

 

This thread has made my day :)

 

Dave

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First off, I love this Forum. You get all kinds but everyone comes at it with a healthy amount of respect. Mark, I appreciate your advice. I'm guessing in my situation, I'll go with your method but I really appreciate the more scientific approach of the engineer types. Hmm, I might have to go get a scale. Seems like another thread is going to make me spend more money!

 

Mark, 

 

I really like the idea of labeling the jerk baits so I know what's what on the water.

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