Vodkaman

Looks like the circular tank is comming out on top. There are two proposals for driving it:- A) centre mounted paddle. edge mounted pump. Both will do the job, equally efficiently from a power point of view. But the centre mounted does have a few disadvantages, minor, but worth considering. 1) More work involved. The paddles have to be constructed. 2) a beam will be required to mount a bearing at the top of the paddle spindle. 3) in operation, the paddles will disturb the water close to the test area. The advantage of the centre mounted drive is that a wider selection of motors will be available, which will probably make for a cost saving. Also, with a top mounted motor, no sealing will be required, as the bottom bearing can be wet. Disadvantages of the side mounted bilge pump is cost (no research done, just assumption). Advantages are:- 1) simple construction. 2) the whole drive mechanism is self contained inside the pump housing. 3) sealing is simple, comprising a rubber gasket or sealing compound, to stop leakage. 4) the pump, located at the opposite end of the tank, has minimum possible effect on the test area. Incidently, if the tank was 6 feet diameter and 18 inches deep. The volume of water will be 264 gallons (UK) or 1.2 metre cube. My tap (pretty low pressure) at 23 secs per gal, would take 100 minutes to fill. This thread has been excellent. We have now arrived at a practical, workable solution. Compact, low cost and reasonably storeable in a workshop. I hope someone does build it.

It's a good idea, but I don't think you can beat the instantaneous feedback of the web site. Not only am I addicted to lure design, I am addicted to this site. I have viewed others, but this one is streets ahead of the rest.

I use the oven, BUT, if you over cook it, the surface can get very powdery. If you brush on the sealer, you can disturb the surface and destroy detail and finish. I make a 50/50 mix of elmers or PVA and make sure every part of the mould gets a soak for a few seconds. Longhorn is the man for Elmers use. Read all his threads and you will rapidly become an expert.

Same here, quality posts and a nice guy. Merry Christmas Pete and family.

I'm a car designer, I can do that!

It looks like the stuff used by rubber powered model aircraft.

Rent-a-test tank!

Just found this on the web. I had no instructions with my purchase. Seems like we are both roughly on the mark. I weighed 20 drops of water, 20 drops = 1cc. I know this is not the same, but close enough for me. http://www.eti-usa.com/consum/castresn/castinst.htm This link covers it.

If your scrapping the old one, experiment with it. Try the heat. Put it in a warm place a few days, if you don't fancy the food oven. 50 deg is pretty cool! Looks like you've figured it out. Post a pic when you've finished it. Thanks.

Palmetto and BobP. I just spent an hour writing a reply, only to find that you have comprehensively covered it! Plus, you can explain better than me.

Select: ‘My account’ ‘Edit options’ Scroll down to ‘messaging and notification’ The third box of this section is ‘private messaging’ Of the four boxes, click the top and bottom boxes. This should clear the problem.

Phil, I tried it. Didn't work, I ended up with a large bruise on the side of my head.

With the plaster being 'raw', there should be some absorbtion too, this will help. It has to be worth a try. Not every lure has fine detail and for these, powder could be the answer for a durable, shiny finish. I wish you luck with the project.

BobP, I already thought about this one. The lure will swim to a maximum line angle (line to water). Once this angle is reached, the lure swims horizontal. It will have a nose down attitude, as it will have in the lake, but it will not swim any deeper. In a test tank, this angle can be accurately measured. This measurement will not tell you exactly how deep the lure will dive, but it will give a good comparison to divers of known depth. If the lure hits the bottom of the tank, shorten the line or raise the tow point on the tank rig, to allow some lateral swim room.

Clamboni, it looks great. I like the pin joints, very tidy.

This is an early post on the subject. It is pre-crash so no pics, but still an excellent thread. http://www.tackleunderground.com/forum/showthread.php?t=126&highlight=wood+lead+mold+halves Someone published a similar technique recently for moulding simple lead weights for internal use. By pinning two pieces of timber and drilling down the joint. I tried this and it works VERY well. Surface finish is not good, but I didn't polish the wood. My next test in this area will be with fibreglass impregnated car filler. Very hard, good detail, smooth finish and quick to set. If this is a bad idea, please let me know!

A very interesting and valid point Spike. On the surface, a very silly idea, but I think that you are hiding a deeper knowledge of the subject. 'Dynamic similitude' and the science of Reynolds numbers etc is used extensively in science and engineering, prior to building full size models, for testing aerodynamic behavior. I explored the idea of testing in air. I calculated that a speed of about 30mph (from memory, long time ago) would be equivalent to 1m/s or two cranks per sec. I even managed to talk another TU member (I don't drive cars, I just design them) into testing the theory. Unfortunately, it did not work and it can be very embarrassing explaining your antics to the nice police officer. Todd, as for storage, the circular tank wins there too, it can be hung on the wall.

Although resin is hard in twenty minutes, it can take several days to cure completely in my experience. I don't think it is lack of thorough mixing as I could not be accused of that, yet I still get the problem. There is no excuse for not mixing this stuff properly, no measuring, it is fairly runny and you get a good five minutes for pure mixing, a couple of minutes to let the bubbles out and then pour. The stuff I am using gives me 11 mins before it strts to change. I suggest that you do a sample and time it, for this information. Secondly, you can vary the amount of catalyst to affect things. How many drops did you add? I usually add 3 drops for every 10gm of resin. This can be increased for a faster harden, but it gives off more heat. Not a problem for small stuff, but larger castings can crack. You could try a few hours in the oven (lowest heat and the door slightly open), the process is chemical and so heat will accelerate. When using any new material, there is always a learning curve. The resin that I am using now has completely different properties to the stuff I bought in the UK, 8 months ago. The new stuff is harder and brittle, a resonant ping when I tap it with my fingernail. My next mix, I am going to halve the catalyst to test the effect. I suggest that you keep notes and report back with your findings.

Husky, you sound like you have given up with the foam! I only got to play with it for a few days before I moved to Malaysia. I wish I had brought it with me. I experienced the variations in expansion. It seemed to be relative to how much airation was introduced in the mixing stage. I would imagine temperature would have a profound affect also. I did learn that PoP was not the mould material, every attempt was a disaster. Now I have RTV and no foam! I have done some experiments with the resin (50%) and air in a mould and rotating until the resin goes off. This leaves a centrally located bubble to provide the buoyancy required. I did not succeed totally, as turning the mould by hand was inconsistant. I estimate that one rev per second would do it. Unfortunately, I don't have the equipment to test this out. The resin 'goes off' from liquid to rubbery in just a few seconds, this is the reason for the speed. Testing with even higher speeds may be necessary. Has anyone tried this technique? If not, I invite one of you to have a go and report. It may be a while before I am in a position to test the method.

Thanks Bruce for your help, but it did not work. I've just spent the last two hours reading help docs and messing about with settings. NO MORE! It's going to the shop. Goolies (like it!). Interesting idea, but I still like the circular tank with the giant vortex. What am I talking about, I'm not the one building it, sorry for that. It is just that I spent so much time thinking about this project a few months ago.

I wish I could view the vids, something is not set up right on my laptop. I'll have to take it to the shop one day, unless one of you guru's can make a suggestion.

I cannot see a problem with a circular tank. The most important thing is that the flow is constant and uniform or laminar. The larger the diameter, the less the curvature will effect things. If it is the intention to use the tank to tune the lures for straight running prior to delivery, this could cause a slight problem. But by running a perfectly tuned lure first, would show if the tuned lure runs to one side or not. You just need to tune to the same pattern. I didn't explain that very well! I agree with Pete, the power to push the required volume of water through a straight pipe is large in comparison to the motor required to drive the circular tank.

I've never used powder, but I would imagine that any fine detail would be lost. It could be worth trying though. Report back with the results.

I think it is called polyester resin. You add a few drops of catalyst to activate it. I bought mine in a craft store, more expensive but I just wanted to try it out.

Fatfingers, your photography is outstanding!