Vodkaman

I just read a comprehensive article on the subject. It basically says that most lures reach 90% of its max diving depth with 120ft of line out. It also states that each lure is an individual entity and that some lures are only just getting warmed up with 120ft and will perform with far more line out. http://www.precisionangling.com/learn.html So, I find your figures strange. Perhaps you could post a link to the table that you are using.

That does not read right. Surely with more line out, the thing should swim deeper.

Pete, I don't follow your links! So, are we designing a fish now? Your design inginuity combined with some of the paint artistry on this site, next years bass masters is in the bag.

I know you have already managed to cut the block, but my method would have been to chain drill a series of 1/4 dia holes close together across the block and then saw or do the hatchet thing.

I'm sure every progressive thinking lure designer has given this one a thought for about five minutes, so here are mine. The propulsion would have to be at the front, because of weight distribution. My idea was a driven prop to draw water in at the nose, into a tube or cowl. The prop would be inside the cowl and not visible. the tube would split into two and vent out the sides at an angle, thus driving the lure forward. The motor would be switched on and off by a water resistance cmos switch, so it only operates when wet, saving battery power. Problems. Size, power, sealing the electronics, battery replacement. These are not major problems, easily solved with a little creativity. The main problem is the the water jets would be rotating in opposite directions relative to the body, out of the exhaust vents and will probably cause some rotation of the body. This too could be designed out. But the main problem was that the driven water would kill any vortex driven action and it would probably swim like a lively log! I moved on to the next idea.

I am relieved to hear this, as I think polyester resin makes a great sealer coat. Very strong, smooth and it seems to accept paint well, although I don't do much there, other than applying some white for visibility.

Shortening the lip is probably not going to fix this problem. Let me guess, you are experimenting with a wider than usual lip, possibly a fan shape. The lure flips on its side but does not roll over completely. If this is true, then you have wandered into another type of instability that has not yet been discussed. The solution is to reduce the side to side angle of the lip, This will reduce the width slightly, but should fix the problem. Hope it is not too late.

I kind of get what you are trying to say Senkoman85. The plane and the sub are equally good for your analogy. When the human body dives, as you explained, the body is compressed. The air in the lungs is compressed. This is equivalent to a soft, flat sided balsa body. The body pressures balance out when the pressure inside equals the pressure outside. In a sub, the pressure inside essentially stays at one atmosphere. The enormous pressure on the outside is absorbed by the structure of the hard shell. In a plane, again, the presure stays essentially at one atmosphere, the enormous pressure on the INSIDE is held in by the rigid structure of the hard shell. Both these analogies are the equivalent of the hollow hard plastic body. Eventually, a depth will be reached where the pressure loads will be greater than the rigid structure resisting them and the body will implode. In reality, on aircraft, they reduce the internal pressure to the equivalent of 10,000 ft. This is why your ears pop as they regulate the pressure and you feel tired and occasionally gasp for an extra breath for no apparent reason. By introducing this pressure drop, the difference between the inside pressure and the outside vacuum is reduced and thus the loads on the airframe are reduced. Also, a submariner does not have to worry about the bends, he does not have to control his rate of ascent, as he is working at a constant pressure of 1 atmosphere. If a regular diver rises too fast. Certain gasses start to come out of the blood as bubbles. Exactly the same way as a bottle of coke starts to fizz when you open the cap. The sudden reduction in pressure causes the dissolved carbon dioxide to come out of the solution as gas.

The Ekranoplan project. I think some entrepreneur started making small versions in the US. I saw a documentary on the subject a few years back.

I would not give up just yet. You need to do some tests to find out what the problem was. Cast a few more and coat with the resin. When cured, put them out in the sun. Put an uncoated casting out too, for comparison. It could, as you suggested, be an adverse reaction. You are playing with a very complex chemistry set, the sun's UV is another reactive component. Try a different sealer! By giving up to move to resin, you are making me nervous, as I am about to make the move in the opposite direction! You have already invested plenty of money in the foam, you might as well follow through. By all means, build some resin baits, but do the foam tests. Then you can compare the pro's and con's of both materials.

I wouldn't spend hours painting the Mona Lisa to try out a new technique. Rough out a quick test piece. Seal it in your usual way. Splash some paint on it. THEN try the technique. Another, more effective way to pre-heat, is to set up an open box, so the air can circulate. Set up a hair drier. Control the temperature by adjusting the distance of the drier. You only want to warm the lures through (not just the surface), so just a hand warm airflow is enough. If you heat is too hot, yes you will damage the paint, but you do not need to get close to those kind of temperatures. Hope you get it sorted out.

You are correct. In fact, the effects are very strong in water. When I started all this, the application of aerodynamics was my first plan. The problem was, I could not find the oscillation (wiggle). I figured that if I curved one side, it would step out into the flow, reach a stall condition and fall back. This did not happen. The lure stepped out until the stall was reached, it would then reach a balanced condition and swim to one side. Failure. Only then did I examine existing lipped lures. My aircraft background told me that the lip would just create turbulence. So I googled turbulence, which lead to vortex,then to vortex shedding, Karman vortex street and within an hour, I had the complete(ish) story. Curvature can be used as part of your design, by adding or subtracting it from the back or the belly. A curved or domed back will raise the dive angle and reduce the size of the lip. But you may want more lip for more action, so reducing the back curvature may be the solution. At the end of the day, the lure has to balance the fore/aft forces, top curvature is just another factor. Vortices are a major part of flight theory, generally, we try to reduce the vortices to zero and use the laminar flow to obtain pressure differences above and below the wing to generate lift. But only now are we learning that the birds cheat. They use laminar flow, but also utilize the energy in the vortex flow. In fact, insects fly purely off vortices. The only commercial aircraft to utilize vortices was Concorde. The swept wing created a massive vortex, which sucked the wing upwards. Once the craft gained speed, laminar theory took over. If you can find a way to make laminar flow make the lure swim, I would like to hear about it, as so far I have failed.

Regarding the clumping, you may well have answered your own question. But the underlying problem is the bubbles. Are the bubbles in the epoxy and could be attributed to your mixing technique OR are the bubbles eminating from the body. Close examination should reveal the answer. Epoxy is an exothermic chemical reaction, in other words, it gives off heat. If the body is light balsa, this heat will cause the air inside to expand and find a way through your sealer. The heat you apply would worsen this condition, but would also help clear the bubbles away. I can see a couple of solutions to this problem: a more substantial sealer and/or warm the lures up, under a lamp, before applying the top coat. This way the air escapes before you apply the epoxy. Vacuum systems have been discussed in the past, during the sealing process. This would allow deeper sealer penetration and make air escape more difficult. Try a few searches on key words like sealer, bubbles, vacuum etc. I'm sure you will find an answer that works.

Chartreuse, excellent description. Do a google on "vortex shedding", fascinating subject, easy to understand and it tells the whole story.

Del does a starter kit that may fill your needs and get you started. He advertises on this site (Del mart). This should let you know whether you want to continue with pouring or go back to retail. Is your chosen bait a one piece mold (is it flat on one side). If so, a simple PoP (plaster of paris) mold will get you started and it doesn't get simpler or cheaper than that. If your bait is rounded and you can see a seam or join line, then it is a two piece. PoP is still possible, but you might consider RTV (room temperature vulcanising) rubber, it's just a two part mix that pours and sets at room temperature. No special equipment needed, at least at the start. RTV is more expensive. Use the search function at the top of the page and read about the whole process. Click forums and select member submitted tutorials, there is a ton and a half of information on this site. Once you are more familiar with the process, it will be easier to make a decision. BE WARNED, pouring is addictive, once you start, you may not be able to stop. One or two members run 10 step programs for lure addicts and claim that they have the habbit under control.

A stirring rod.

I hate iceholes, I'll stick to casting resin!

The biggest drill bit we could find was 3/4 dia. I've caught four lips so far!

Are you sure you didn't pick up the supermarket plans by accident? That is BIG. Very nice too.

I've since built an 8ft extension piece, thanks to all the rod building information here on TU. Problem solved. Now all I have to do is lower the lure through the hole. That's engineering!

My brother bought me an ice fishing rod and a pair of spikes for Xmas 2006. Cheers bro! Found it difficult to use, I kept missing the hole when casting. I'm sure there's a knack to it.

Thanks Redg8r, good information. Oomoo 25 seems to fit the bill, 15 min pot life, 75 min cure and shore hardness of 25. Oomoo 30 has a cure time of 30 min, but the cure time is 6 hours and a shore hardness of 30. I don't think I have the patience for that cure time. Hawk, good luck with your project.

I can see how that would be discouraging. 16 hours does seem excessive, the stuff I used was solid in less than an hour and I could throw the second half of the mold after two hours. I can see how a softer RTV would give clamping problems, as I did experience some of that myself. This is a good enough reason to go for a firmer product. So, an additional question: What are the normal set times that other members are experiencing?

Before I make my next purchase of RTV, does anyone have any opinions on the advantages and disadvantages of the hardness of the compound or have any preferences. Also, which brand do you prefer. My first purchase was thixotropic RTV, it mixes to the consistency of a thick paste. I went for this product in light of all the threads discussing the expense of RTV and how to cut down the cost. Thixotropic RTV goes where you put it and usually ends up the shape of a cow pat. With a little practice, it makes a reasonable mold, but clamping the two halves together is a nightmare, so never again, I would sooner pay the extra.

It sound to me that every time you make a special effort, the problem occurs. The prototypes worked fine, then you made a dozen to use in a comp, problem. Then you made a bunch for charity, problem. Every casting is going to have some flash type deformation at the mold joint and will require a certain amount of finishing. My guess is that in your attempt at preparing for the best finish possible, you are removing too much material from the raw casting and clipping the top off some of the bubbles. The bubble fractures are not large enough to allow the primer coat into the bubble void, thus preserving a weakly contained bubble of air. Once in service, any direct sunlight will be soaked up by your colors and the air bubble expands. The solution is to address the problem. Remove as little material post casting as you can get away with. Still assume that some of the bubbles have been compromised and seal accordingly. A very thin sealer with a low viscosity would probably be favourite, maybe propionate. Maybe heating the casting in a low oven for five minutes before applying the sealer would help by expanding the air. As the air contracts with the sealer application, the sealer will be drawn in. I'm not convincing myself on this one, warming the sealer might help too (no open flames!!!). Before moving onto the next phase, why not test the results under a 50W bulb for 30 minutes. If the problem exists, this should reveal it. I have only the briefest of experience with foam, so the above is not from personal trials, just common sense and engineering. I will bow to experience here, should it conflict with the above, as I too need a solution to this problem, as I am thinking of going over to foam myself.