Vodkaman

Pete. I too finally bought a set of digi scales. Essential equipment to design. But the first six months of my lure quest was done on the above beam scales.

Better late than never. Welcome. Come sit by the fire, it must be cold out there.

Luretrekker, I think your vortex theory is spot on. The thing about an aerodynamic or smooth flowing nose section, is that, like a wing, it promotes laminar flow and we need the vortices for the action. SO, before trying all the invasive solutions mentioned above, all of which are sound advice, try the silly puddy! Create a blunt nose, then increase the ventral depth and then try both. Try molding a blunt or flat above the eye location. All these trials are for free, no damage to the lure. But only change and test one parameter at a time, or you won't know which one worked. Once these tests have been exhausted with no result, then you can start cutting. If you really want to keep the fins, then as suggested above, you may have to introduce a lip. Lots of good advice above. Don't forget to report back with your findings. More can be learned about lure design from the failures than from the successes. Don't bin the failures, send them to me!

I think the lure looks great, I really hope you get it to work. What material did you use for the body?

You could experiment with the front section by molding some plasticine on the front and try swimming it. Messy, but non-invasive.

I was trying to give advice that fitted the budget, I assumed a budget of a couple of thousand as that is the price that CNC starts. Of course, with a 5 axis machine, you can make just about anything. But 5 axis and laser digitizers are just not feasible for this project. 1 - 2K will get you a desk top operation, 3 axis machine. They will cut an area of roughly an A4 sheet of paper (12x8). For cutting lips and bodies 4 at a time, a machine of this proportions should be adequate. The cheaper machines are based around a dremel type motor, but if you pay just a little extra, a more powerful, dedicated motor can be provided. A 15K budget will get you a very descent machine, probably upto A3 or even A2 size. It may be a good idea to contact suppliers of such machines in your area and see if they can put you intouch with other small machine operators in your area. You can then get a first hand appreciation of what is involved. The Smithy1240 looks good. You should have no trouble finding a user of this machine in your area. You can cut a lot of bodies on a 22” x 13” bed. Good luck, should you decide to persue this option.

Jerry, what rotation speeds did you try?

A week before and a week after.

Rossrods has a thread going, were he produced his master using CNC. http://www.tackleunderground.com/forum/showthread.php?t=11415&highlight=rossrods Perhaps Rossrods or anyone else could give us an indication of time to machine two halves of a body. I suspect that the time savings will not be spectacular. The advantages being repeatability rather than time. Also, other limitations have to be considered. The body will have to be machined in two halves. This works out nicely for installing through wire hangers and ballast. The wood has to be clamped or fixed in place for machining. This will leave the equivalent of sprue to be removed and cleaned up. Also, the surface finish will need improving, especially if using a very fibrous material like balsa (see photo's in Rossrods post). The machine would do a great job of cutting out lips, maybe twenty or more at a time. Again, there will be at least two, more likely three bits on each lip that will require dressing, but it sure beats the labor required to manually cut twenty lips. Care and thought has to be taken when it comes to any body detail that is required, like gill plates, lips and scales. I am not a machinist, so step in if I tell lies, but the final detail cuts will probably be made with a ball end cutter. The larger the cutter, the faster the operation. Obviously smaller cutters will be making a larger number of cuts and consequently wear out quicker. So the machinist wants to use the largest cutter possible. The artist in you, wants to do fine scale detail, with sharp cuts into the wood. This is not possible with a ball end cutter. I'm not sure what the minimum diameter cutters are, or what the experienced machinist would consider the practical minimum, I would like to know please! With this information, it is possible to design on CAD, ensuring that the minimum radius used, matches the CNC cutter requirements and you can reach a compromise with your design, which can be viewed before going to the machine. The model is then saved, hopefully to a format that will suit your machine. But, as Del would quickly point out, things that can be dismissed in a simple sentence, don’t usually work out that slick. Trouble shooting problems is going to be a long learning process. I am on the edge of jumping in myself, so I am trying to be a realist, probably coming across negative, sorry about that, I really want you to succeed with this huge step. If you don't want to go the CAD route, some machines provide a digitizing probe, this will load the shape into the computer. I know this is way more than you asked, I guess the subject is on my mind. The machine will buy you some hands free time while the machine is running. You could utilize this free time by carving out another body!

An idea that I was considering was rotation setting. Fill half of the two piece mold with resin. Close the mold. Rotate on a wheel until the resin sets. I tried rotating by hand, I got the bubble but it was not distributed well. My opinion is that a rotating mount, rotating at about 60 rpm would give a result. This speed is a guess, based on the viscosity. Once the resin starts to turn, it goes to jelly in a few seconds. If the rotation is too slow, it will give an uneven bubble. Possibly even faster rotation speeds might produce better results, using gyroscopic forces to distribute the resin. Another method that I tried, a balsa wood insert in a resin cast. This worked, but more labour intensive than I wanted.

Unless you buy blank bodies (hard baits) or copy an existing lure, the project always starts life as a sketch on a piece of paper. The sketch is refined and transferred to a chunk of wood or suitable material and the carving begins. Personally, once the very rough shape is cut out, I remove the paper guide and go with the flow, rather than trying to force a shape. Quite often, what looks good on the computer, is not so appealing in the hand. As for the carving part, there are a few articles on the subject. Basically covering marking of centerlines, guide lines and attention to symmetry. Some of the members are true artists when it comes to carving, I myself am not. I tend to steer clear of the fine detail and go for pure functionality. Actual carving skill tutorials for fine details I do remember reading at least one, but generally, everyone finds a method that works for them and goes to it. As I am not blessed with the carpentry skills, nor the patience, I take my whittled master to the molding table for reproduction. I envy and admire the work of those who can turn out true hand carved lures, individually tuned to swim correctly and finished to a high aesthetic standard. When you buy one of these, you are buying art, justifiably signed by the artist.

It is a shame that this thread has taken such a dive. The guy asked a simple question and immediately, the thread went off at a tangent. As a result, we missed the opportunity to convert a plastics guy to the joys of hard bait manufacture. I never read Benton’s post as a derogatory or negative in attitude. Hell, I hate being told to ‘go suck it and see’ or ‘go burn some firewood’, I don’t mind saying, I was furious when these comments were made to me twelve months ago. I read Benton’s comment as encouragement to ‘have a go’ and see if you can figure it out, as part of the pleasure of design is solving the problems. I even gave a hint as to the direction that I would have taken. No one ever suggested that the information should not be given. Another issue that was skirted upon, in this threads journey through the bowels of TU, was the moral intellectual rights of the original designer. I say moral, as the actual design is probably not protected, but if his design is used, he should at least get some credit for his problem solving skills. The suggestion made, to contact the original designer for information etc was a good one. I was disappointed when Loco took umbrage and announced his return to the plastics forum, never to visit the hard baits ever again. I PM’d my thoughts to him with an apology for my part in this mess, to which he sent me a very nice reply. Every time this issue comes to the table, it is always highly emotive and we never seem to learn from the outcome. My philosophy is to help people. Orion, thanks for those nice words, We must have exchanged fifty PM’s and e-mails, it felt good to help. A lot of the stuff that I write is difficult to understand. I am always happy to clarify points or answer other technical questions by post or PM, generally, this work gets priority over everything else, quite often I learn a great deal during this process. I really hope that we can put this one to bed and start solving some of the easier problems that plague the lure designer, like world peace!

Kevin, I know what you mean with the chrome spray. I bought some to try, it went on nice. It didn't look like chrome, more like the dull side of aly foil, but still metalic. I then coated it with epoxy, this killed it and it turned out a boring mid-grey. Not to mention all the compatability problems and drying times! The lures look great.

I just did a Google for Devcon 2 ton and found a data sheet. This states the cured density of the epoxy is 1.1gm/cm³. This means that one centimeter cube of epoxy weighs 1.1 grams. One centimeter cube of water weighs 1 gram. Therefore, the epoxy only adds 0.1 grams to the ballast for every centimeter cube of epoxy. In real terms, approximately 10% of what you add to the lure counts as ballast weight. For Bobs example, he added 0.57gm of epoxy. Of this, 10% (0.057gm) will count towards ballast. This is a very small number and will effect suspending lures, but its effect on floaters or sinkers is unlikely to have any visible effect.

Good job on the rendering, it looks great. I'll take two!

I could really do with a close up of the mold (I should have said, sorry). I want to see how the mold is vented, to see if anything could be modified or adapted to make it pour. If the mold is not usable as it is and you are up to a little experimentation, I'm sure I could come up with a plan. It is either that or just sell it!

This is one of those things that is on my "to do" list, but just haven't got around to. You can only really calculate or measure the effect for one particular shaped lure. The information gained cannot be applied to a different shaped lure. This is because the amount of epoxy and its effect on the average density of the lure is directly proportional to the surface area. So a deep, flat, thin body will have a larger surface area to body weight than a short, fat, round body. Therefore, the thin body will require relatively more epoxy and the average density will be affected more. To my knowledge, no one has actually measured the effect. We know the problem exists and the experienced builder allows for it, without even thinking about it. When I get to that stage, I will of course be calculating it to death and it will form part of a density spreadsheet. This will enable me to weigh the lure at any stage and I will be able to compensate for any differences with slight adjustments to the ballast. In the absence of such data, I suggest that you start the study off and calculate the effects on your lure. Do you own an accurate set of digital scales? if not, then the subject is going to grind to a halt very quickly. If you do own or can get hold of the scales and are interested to do a few minutes of testing, let me know and I will write you a method sheet. The method is very simple and will give you the density of your lure. Repeat after each coat of epoxy and you will be able to see the difference that each coat makes, each subsequent coat having a slightly larger effect than the previous, as you rightly pointed out, the volume of the lure increases as does the displacement. You have already figured most of it out, I hope you take up the challenge.

Could you post a pic of the grub mold, I would like to understand more what is going on and how the mold works.

Sounds harsh, but I do agree. It is the way that I work and satisfaction does come my way when I crack the problem. Also, this is the only way new techniques will come about. In a couple of weeks you could be posting a tutorial on how you solved the problem. I checked out the first link that you posted and it all looks fairly obvious to me, a wood/plastic sandwich.

I haven't totally made my mind up yet, but it's looking like light balsa for prototyping and resin/micro spheres for the finished articles. I'm having density issues, so may switch to foamies.

The characteristics of the line density etc, have little effect on the depth. Only the diameter of the wire catches the water forces. Again, when the upward forces on the line are equal to the downward forces on the lure, a balance is reached and the lure swims horizontal or parallel to the surface. The lure would swim at a constant depth below the surface.

VMAXX, the lure does bottom out and run horizontal. A depth is reached were the downward forces start to reduce as the line/lure angle increases, balance the upward forces of the line. At this point the lure swims horizontal. The lure is still trying to dive and is held up by the line. There will be a minimum ammount of line required to get the lure close to its maximum depth. Letting more line out will not result in any significant increase in depth.

Yes, but is all about the line.

That is correct. But the lure does not have a maximum depth. Given the right tow line angle, it will keep diving. All the limitations to diving are in the line. If you use the thinnest line available, the lure will dive deeper, quicker. The thinnest line has the least resistance to the water and will 'cut' through the water easier.

Kribman. It is best to have the ballast as close as possible to the CoG, you may want it slightly forward, to control the floating angle. When you add the ballast, you affect the CoG. If don't place it at the lures CoG, then the new CoG will be offset from the ballast and the original CoG and the action will be reduced, due to inertia of the ballast and the body. The denser the body material, the worse the problem. Balsa is so light, which means more ballast required. So, where ever you put the ballast is where the new CoG will be and the centre of the 'X'ng action or wiggle. So the answer to your question is: the centre.