benton B

warm water vs cold water

24 posts in this topic

If you have a bait that rises slowly in 70 degree water, will that same bait slowly sink in 50 degree water?

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Depends on how close it is to neutral bouyancy (i.e., suspending). In general, I doubt a 20 deg change would make most slow floaters sink. Other factors also come into it. If you're using fluoro line, which sinks, on the slow floater, changing to mono would probably make it still float in 20 deg cooler water.

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Duh! I shoulda realized that was backwards! Benton, if it rises slowly at 70 deg, it will rise faster at 50 deg.

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Don't feel bad BobP, I nearly backed the whole thing up with calculations, no wonder I couldn't get them to work!

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Yeah, I was definitely having a senior moment. As far as fixing rise rates, the only sure way I know is to float the finished lure in the correct temp water and adjust ballast until it behaves. Hanging lead solder on the trebles works well and is easy to adjust. Then drill a hole, melt in the solder and patch.

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Right, but that 20 degree difference in water temp can make a pretty big difference in sink/rise rate. You can figure out the properties and actions of certain baits to make the float/sink slowly or suspend at certain temps.

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I should have asked my question differently. I have a LC pointer that I can't figure out why the darn thing sinks in the winter and floats in the summer. But it sinks faster in the cold water than it rises in the warm water. I know somewhere in the middle it will suspend, but I thought the higher density of cold water should make it float. Is that about as clear as mud?

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Unless it's cracked and taking on water, I'd think it has to be using different line, say sinking fluoro versus mono, or maybe you changed the trebles out? It's gotta obey the laws of physics.

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It still could be true. The same physics that apply to the water are applied to the plastic. The changes in density for diferent materials vary like metals expanding at diferent rates, so there could be an overlap.

There are lots of density tables available on the WWW for water, but may need a bit of research to find the equivalent for the plastic that you are using. Do some experiments and post the results. The results will be interesting and valid for this site.

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Vodkaman, you're talking to one of the guys that builds by trial and error or sometimes lots of errors. I'm not the guy for test and measurements, I wormed out of physics class for human biology. That's why I asked the question here. I know from the number of baits I've tested there are differences in the rise rates between cold and warm water. From my limited experience baits rise slower in cold water and that's what I'm trying to figure out. Bobp I only use braid and that line floats. I do thank you fellas for your posts and wisdom. I think I'll just build baits and not worry about what makes them work, just as long as they work.

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I do not want to argue with you guys about all the scientific terms but from fishing experience , I do know a bait is less bouyant in cold water.

Also if you take a water bottle for instance open it in warm air, seal it back , cool it down, as the temp drops pressure decreases it will collapse. but as the temp rises back up the pressure will rise and the bottle will expand back to normal.So Possibly this is what is going on within the bait .I'm no expert by no means, just my opinion .

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What about using woods that are less buoyant oak , walnut, etc then you would need less lead to reach neutral buoyancy ? Ive been wanting to make some wood baits that suspend but haven't yet tackled it.

I can make great swimming standard crankbaits but have yet to try experimenting with wood versions that will suspend. I Usually just buy Xraps, or others but have been wanting to try it on my own. I guess now is as good as any :)

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fishnfool38 has the right idea. This subject has come up before in the early days of TU. Its not the lure. Its the air inside the lure. I have had jerkbaits that you could hold in your hand and warm them up on very cold days and you could watch them rise when you first put them back in the cold water, then slowly start to sink when they got cold again. I think barometric pressure has a little to do with it also.

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Re-visiting this thread after so long, does put a fresh perspective on things. Upon re-reading fishnfool's post, it struck me immediately, the same as Hughesy, that the changes in the lure are causing the contradiction.

In my mind I was keeping the lure constant and only considering the water density. Respect to Fishnfool, no fool it seems!

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The buoyancy thing has nothing to do with the air inside the bait....unless the plastic changes shape. Air expands at higher temps and contracts at lower temps, everyone knows that, but if it's in a sealed container (lure body) it still has the same mass regardless of how much space it occupies. If the plastic expands and contracts enough it can change the density of the bait. But I don't think the plastic can change as much as the water does.

I hear a lot of people say they've noticed lures floating faster at higher water temps. This goes against the laws of physics. I actually notice the opposite happening. I don't know why, but I have baits that sink faster in 55 degree water then they sink in 45 degree water. I know the air in the bait contracts when it cools so that should make it heavier......but only if the container it's in contracts with it. I don't think that luer bodies expand and contract more than water does. In my personal experience...........baits that suspend perfectly in late october/early november........slowly float after that until Mid March or so.

I fish all winter here in NJ as long as the lakes aren't frozen. I'll try to remember to pay attention to this for the rest of the winter. I'll also try to remember to post what I've found once the water warms up again.

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Clamboni, I do agree with you. If the lures shell does not change shape then no matter how much pressure on the outside, the pressure of the air inside does not change. In this case, the lure will obey the changes to the water due to temperature, namely the lure will be more buoyant in the cold water.

But consider a balsa body with a standard epoxy top coat. This coat is not strong enough to resist the pressure difference and will distort. Hardly noticable, but the distortion would be more significant then the difference in the water due to temperature. Under these circumstances, IN THEORY, it could be explained why the lure might become less buoyant as the temperature dropped instead of more buoyant.

As the body compresses, the volume decreases, the weight stays the same. Therefore the average density of the lure increases and the lure sinks. Archimede's must have been a lure designer.

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Archimede's must have been a lure designer.

Nice.......

We think too much......

But if the outside of the lure is compressed enough, then yes, the density will increase.....You brought up balsa baits with epoxy topcoats. Making me think again. I had a big long post typed up about how I was gonna post without thinking deeply into it and I started thinking about it....damnit!! The more I thought about it the less I was able to decide if a balsa bait properly sealed and topcoated would change density enough.

I try to rationalise everythign I can with the laws of different sciences that I know. One of the things I love most about making lures is that you can think and think and think and end up being 100% sure how a bait is going to act. Then you make that first cast and watch the bait and you're like "HUH????!!!! that's not what was supposed to happen."

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I am sitting here, reading your post, with a big grin on my face. I've been there so many times!

I'm half way through writing a thread on volumetric analysis. It was supposed to be very useful for lure design, but it has got out of hand. So I have decided not to post it. I will re-visit it in a few months time and see if I can get a more useful perspective on the subject. In its current form, it will just annoy everyone (as usual).

Think too much? I don't think so. I don't think I think thoughts through thoroughly enough. This thinking thread has thunked me out. I think I need some of Bruces medicine!

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I don't think I think thoughts through thoroughly enough.

On another board I visit regularly, we have a smiley that just shakes his head.......

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Hi guys, just a thought. Plastic contracts and expands a lot in temperature changes. If the bait was cracking at the seam when it contracted in cold water it could be taking on water. Does it sink faster on the first cast? I read somewhere years ago about putting a bait in fairly hot water on the stove and if it is leaking the warm air will expand out the leak showing bubbles so you can repair the area.

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If it was dry for the first cast and assuming it was designed as a floater, then it would lose buoyancy as it took on water.

The hot water test would work, but I would be more afraid of creating a problem with the technique than solving a problem.

The expanding air, pushing its way out, will force good seal surfaces apart, thus creating a problem. Contracting air inside the lure will tend to close the good seal surfaces, a bit like a non-return valve. If the seal surface is damaged, then water will get in.

Hope that made sense.

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Speaking of hot water, some guys actually boil lipless rattle baits to expand out their sides and give them a different action and more rattle. Plastic baits are usually welded ultrasonically so the joints are as strong as the rest of the bait's body.

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