Help With How To Calculate Ballast For Glide Baits
21 replies to this topic
Posted 03 October 2011 - 08:06 PM
I posted this article about 10 minutes a go and I cannot find it, must be in hiperspace. Let me try one more time
I have been reading on TU just about every thing that has to do with hard baits. I am an avid muskie hunter and I really love the sport. I just caught my first 51 inch muskie, about a week ago, after 30 years .
I have been building bucktails and done really well, matter of fact I caught my 51 incher on my home made cowgirl. Now i want to try my skills on building glide baits, I know they are a lot more challenging than bucktails. I need to do something in the winter month. Making the baits it is the easy part but getting it ballasted properly it is challenging, placing the ballst in the right place not so much, Thanks to TU member, you gentile man provided a wealth of info.
I have done lots of research on the internet, on specifc gravity of wood. I think I understand how to figure the calculation, I hope I do not make a fool of my self but on the other hand you cannot learn if you do not ask.
I know on this site there are lots of people with mathematical engineering savvy, so hopefully some one can correct me if am wrong Here we go
on the internet I found that the specific gravity of water is 62.4LB./cu.ft. 1 cubic inch = .036LB. or .57OZ.
I am going to use Apple wood for my example the SG. is .73 .73 X62.4 = 45.55LB./cu.ft. 1 cubic inch = .416OZ.
in this example I am going to use a block of apple wood that measures 10"X.75"X1.5" = 11.25 cu./inches
Therefore the weight of water 11.25 cu/in. X.57OZ = 6.41OZ
the weight of apple wood 11.25 cu./in. X .416OZ = 4.68
It appears that the apple wood is 1.73 oz lighter than water. In order to achieve neutral buoancy I would have to add 1.73 OZ. of ballast to my bait, or if I wanted to make my bait sink add a litle more ballast. I realize that the block of wood will be cut to shape the bait so a fudge factor would have to be added.
Pardon me for my spelling and punchtuation I am from the old country, so am still learning the english language
Posted 03 October 2011 - 08:26 PM
Your close on your calculations but you left out a couple of factors. The hardware and hooks and paint and top coat will make the calc. a little off. The easiest way that I found is make a dummy lure with full hardware and hooks plus paint and top coat then float the bait and add the ballast a little at a time to the belly area by using CA glue till i get it the way i need it then just snap the ballast off and weight that way i can come relatively close the next time I do another bait.
Posted 03 October 2011 - 09:45 PM
The Archimedes dunk test that Vodkaman posted some time ago will get you closer than anything I've tried. You can get within a couple tenths of a gram of your desired weight on the first try. The test will show you the amount of weight to make the lure neutrally buoyant. Add a couple tenths to make it a slow sinker or more if you want a fast sinker. Subtract a couple tenths to make it a slow floater and so on. Here's the link to the thread.
Posted 03 October 2011 - 10:44 PM
Don't bother with the math...........each one will be different, weight then test.
Posted 03 October 2011 - 10:59 PM
If you are going to get involved in the numbers, which is the way I do it always. You need to change units. I know you guys love your pounds and ounces, feet and inches, but it just makes density calcs a nightmare. Try working with centimeters and grams. Much easier.
Posted 04 October 2011 - 04:00 AM
Thank you Vodkaman, I read your Archimedes dunk test a while back and I could not find it. Now I saved it and printed it. I will use this methot, also being Italian I do use the metric system, I purchased a pocket scale in .01 grams, Also thank you everyone for your input, you are a great bunch of guys.
Posted 04 October 2011 - 07:59 AM
Just remember, a bait make of balsa, and an identical bait made of lead, will displace the same amount of water, so test weighting, like Hillbilly suggested, is still the most accurate method.
Posted 04 October 2011 - 08:05 AM
Maybe we should include a disclaimer to the Archimedes dunk test that it only works when ballasting materials that actually float.
Posted 04 October 2011 - 09:51 AM
I've done it both ways and I like the dunk test because I tend to make one-offs for personal use. I have a pretty good idea of what my paint and topcoat typically add and I weigh all the hooks and hardware and subtract that from the total ballast. I typically make floaters, so getting to exact neutral buoyancy hasn't been important to me. If it was I'd probably go Dave's route, err on the side of "too floaty" and add weight from there with the Hillbilly method. Your mileage may vary.
Posted 04 October 2011 - 01:28 PM
When you look at the density of different wood species, you have to remember the value in a chart is a "nominal" density, averaging density over a number of samples - all of which differ to some extent. So while a density table is generally useful in choosing the right kind of wood, only a test of that specific piece of wood will get you where you want to go. JMHO, If you're not into ancient Greek science, the best way to get your ballast right is to FLOAT TEST the bait, adding and subtracting ballast until you get it right, then installing that amount of ballast in the bait.
Posted 01 December 2011 - 07:09 PM
I have tried the the Archimedes dunk test. My lure is patterned after a Rattle Trap... sort of. My lure is unfinished but sealed. I followed the test to the letter using a scale in grams as directed. My "wet"
weight was 12 g with the hooks and o rings. The dry weight was 5g with hooks / rings. So if I understand the method, I have to add 7g just to get it neutral. If I want it to sink then I have to add more weight. Is this correct or am I totally confused.
Posted 01 December 2011 - 07:25 PM
I think the Archimedes test is more for the volume of water a particular lure displaces.
To get the ballasting right, I would use BobP's method, and just add weight until it floats/sinks/suspends how I want it to.
Posted 01 December 2011 - 09:08 PM
I think so too
I took the bait to the test tank with a small weight attached to the belly. It floated in the upright position ... go figure.
I think the try method will be best for me in the long run.
Just see what it will do as I add and subtract the weight
My next question is " Does the belly hook position have to be where the belly weight is located or is this try and locate as well?"
Posted 01 December 2011 - 09:11 PM
You are correct Firechief. The dunk test will get you really close the first time, but you may need to weigh it again after ballasting the first time if you want to really dial it in for neutral buoyancy. This is because of the difference in weight of the wood that was removed, the ballast itself and the epoxy used to glue the ballast in. Just doing the test once should get you within a couple grams or less. You also need to figure in the weight of the paint and top coat. Sometimes the difference between a suspending lure and one that slowly sinks or floats is just the temperature of the water. Colder water being more dense will float a slightly heavier bait than warmer water will. I've had the weight of one split ring mean the difference between the lure being a suspending bait or one that slowly floats or sinks.
I've tried several different ways of ballasting my lures and have come to rely on the dunk test for figuring the ballast on all the baits I build. Once you do it a few times it only takes a few seconds and eliminates pretty much all the guesswork.
Posted 02 December 2011 - 04:21 AM
Firechief is right, almost. the body needs to increase its weight to 12 grams and like RayburnGuy stated, you will be removing a bit of wood to make room for the ballast. It is not about how much to add but all about the final weight. Yes, this is nit-picking, but makes all the difference.
This method is reliable, but does need a little practice, to get into the swing of things.
Posted 02 December 2011 - 09:37 AM
Thanks for the info. I had failed to allow for the removal of the wood for the weight. Also for the final finish.
It just seemed like a bunch of weight going into a relatively small area.
Remove the wood for the weight and continue to perform the weight test.
Paint / top coat and see what the two do to the overall weight. I understanding that it will be different every time but it should give me some idea. Should be around 1/6th of the total weight but that is only my assumption.
Posted 02 December 2011 - 08:29 PM
I like to have the final ballast hole/s already pre-drilled(on a completley finished plug) when I do the dunk test. The wood is sealed so submerging it briefly with all the hardware for the test is not a problem. I tend to go heavier than I need to. Since I fish wind/open water and brackish inshore, I like to make duplicate plugs, with one weighted to maintain depth in the chop and cross winds. You can always drill out some of the lead, if needed.
The dunk test is money for me. Its really helped me fine tune the balance issues needed for my gliders and sub surface walkers. If I know how much to add, I can put it in the right places.
Edited by markinorf, 02 December 2011 - 08:36 PM.
Posted 02 December 2011 - 09:24 PM
Well... I followed the advice given and the results are as follows.
My dunk test results with hooks and pre drill was 12 g
Dry weight with hooks was 6g therefore I can add one 6g weight and achieve neutral buoyancy??? , paint and finish will add some more to the overall weight. If I want it to slowly sink then I can just add a wee bit more weight. Is this correct?
SPECIAL NOTE: I noticed that my lure did float in the upright position with a lesser weight (about 4g) taped to the bottom. In fact it looked pretty good. The water line was about mid line to the bait with a small pitch forward in the nose.
Posted 03 December 2011 - 12:10 AM
The math your using is correct. You need to understand that you may have to do the test more than once as I explained earlier because your removing some of the buoyancy. (the wood the drilling will remove) I know of no way of ballasting a lure that will give you an exact measurement on the first try. Even the method of adding weight to the hooks while it's floating in water to get the bait to sink or suspend is not exact because the weight will be inside the lure and you still have to account for the wood that's removed. When your ballasting a lure your actually talking about water displacement. When trying to ballast a lure by adding weight to the hook your increasing the amount of water displacement and not getting a true measure of how that weight will effect the lure when placed inside the bait. By using the dunk method the water displacement remains the same.
When I ballast my lures using the Archimedes method I do exactly what your doing. Weigh the bait with all hardware attached both dry and wet. Then subtract the difference and that is how much weight I add. I then apply a coat of epoxy to seal and smooth the surface of the lure where the ballast holes were drilled. I then test them in the sink or bathtub to see if they float, sink or suspend depending on what I want the lure to do keeping in mind that I still need to allow for paint and clear coat. I usually allow anywhere from 1 to 2 grams for this depending on the size of the lure and what top coat is used. If the bait doesn't do what I want it to do I will perform the dunk test again and by this time you are usually only talking about tenths of a gram. Getting this close is usually only necessary if your trying to make a bait suspend. Building a bait to suspend is fairly hard to do. Especially if your planning on using the bait in different water temps as even the temperature of the water has an effect on whether it floats or suspends at a given weight.
Once you use this process a couple of times it will become second nature and you will know what you need to do to get the bait to react the way you want it to. I've tried several different ways of ballasting baits and for me this is the easiest and most precise way of doing it.
Posted 03 December 2011 - 10:11 AM
I think Ben's exactly right. You seem to have it figured out, at least as much as it can be figured out in the shop.
I only worry about a bait suspending with jerkbaits. I want all of my other cranks to be buoyant, so they float up and out of snags and hangups.
I've found that suspending baits almost never truly suspend, due to the differences in water density at different temps.
I typically use a bucket of water that's on my driveway for my test floats, and it's between 65 and 70 degrees most of the time. I try to make my suspending baits so they slowly sink in warmer water, like in my test bucket, and suspend in colder water.
But I find it almost impossible to outguess what the actual buoyancy is going to be once I get to the lake.
So I go fishing expecting to have to play with a suspending jerkbait every time I fish it to get it to suspend, or sink or rise slowly.
I change out the hooks and split rings to get them to be more or less buoyant on the water. And I use suspend dots. They are cheap and easy.
I've also found that, for cranks and jerkbaits, the amount of wood that's removed for ballast compensates for the added weight of the paint and topcoat, more or less, so I don't stress the last fraction of a gram. I get it close, and tune it with either hardware changes or suspend dots when I'm fishing.