water temp and wake size

davidgree1 · Newbie Joined: 15 Apr 2003 Posts: 29

Have others noticed that the wake size is smaller when the water temp drops?

BIGMAC · Posted: Oct 19, 2003 7:53 pm Post subject:

No just other things Shocked

204Waker · Posted: Oct 19, 2003 8:10 pm Post subject: Re: water temp and wake size

criminally_minded · Posted: Oct 19, 2003 8:38 pm Post subject:

It's quite possible actually. When the temp drops, the water contracts, and becomes denser. This means less water by volume is displaced by your boat (eg: your boat rides higher) and the wake would be smaller.

It's sort of the same principal as fresh water vs. salt water. Salt water is heavier therefore more buoyant, and your boat rides higher, resulting in a smaller wake.

The river I ride on is quite brackish (mix or fresh and salt water) as it runs into the ocean and sometimes floods back. When the salt mix is high, our wake gets A LOT smaller. After it rains and the fresh content is high, the wake returns to normal. When we put the boat in a river which is 100% fresh, the wake is larger than normal.

The effects would be less when concerning temperature I would guess, but it is probably noticeable in areas with large temperature fluctuations.

I have never though about that before. Thanks for pointing it out!

Partyb · Posted: Oct 20, 2003 6:51 am Post subject:

Learn something new everyday. But I agree, the difference would be bigger with Salt v. fresh, as opposed to hot v. cold water. Assuming this argument is valid.

Leggester · Posted: Oct 20, 2003 6:57 am Post subject:

Water gets denser right as it freezes!

I'd guess you'd have more of a difference with algae or other crap in the water folks.

Gee, when the lake turns ( algae from the bottom thermocline reverses to the top thermocline ) does the algae make the wake thicker?

criminally_minded · Posted: Oct 20, 2003 4:57 pm Post subject:

I don't think objects in the water (such as algae) would change the density of the water, unless it was getting to the stage where it was 30-40% algae or more.

It's an interesting point though.

The theory of denser water/more buoyancy/less wake is sound, I guess it all swings on the expansion rate of water molecules and their variance in the range of say 8-24 degrees (I'm working in C here) which would be the mean range in a climate like mine.

I can't really comment with any certainty on that, however given that water is made up of a large percentile of oxygen, and oxygen expands throughout temperature variants, not just at singular points, I would have though there would be at least some change in density between freezing and boiling points.

llenta · Addict Joined: 22 Jul 2003 Posts: 788 City: Davis

all of you have a good point, but i don't think that it's a noticable difference. at least i can't notice it in my wake.
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DEMEROL REHAB ADVICE

MrBlean · Posted: Oct 21, 2003 1:53 pm Post subject: Error

LFADAM · Posted: Oct 21, 2003 2:43 pm Post subject:

wow criminally minded...do u have a master's degree in wakeboarding climate changes or something? ur really smart Shocked

davidgree1 · Newbie Joined: 15 Apr 2003 Posts: 29

The water temp is 53 now. In the summer it is 85. I notice a big difference in the wake size.

Mr. Mutt · Posted: Oct 21, 2003 4:05 pm Post subject:

The water does not get more or less dense depending on temperature. Water, or more precisely H2O, only changes density when it changes states (solid to liquid, liquid to gas, etc). That's because as a solid the energy within the solid form of H2O (ice) is not strong enough to break the molecular attraction between the H2O molecules. As energy increases, the molecules get excited, start banging against each other, and want to get away from one another. At the point of 0C @ 1 atmosphere (because these figures are pressure dependent), the energy begins to separate the H2O molecules to the point that they no longer stick with each other and they are free to move past one another (ie water). As you add more energy (heat), the water temperature increases until you reach the next state shift (liquid to gas). At this point, the molecule has so much energy that it breaks free of all bonds between it and other like molecules and floats away (steam). Note that a gas is significantly less dense than a solid or liquid, but unlike solids or gases it's volume varies with temperature (Avagadro's Law) and pressure (Charles' Law).

What does this mean? It means that water does not change density when it changes temperature, only when it changes states. And it means I'm a nerd...

Leggester · Posted: Oct 22, 2003 6:05 am Post subject:

Mr Blean,

Please explain "dense". AFAIC, Ice is much denser than water - it' very hard to get a boat through ice. Laughing

( and I've had to drill through it for fishing in the winter ) For that matter - wood is denser too! HAHAHAHAHAHAHAHAHAHAHA>

Actually, water is kind of neat. It's the only material that has the same volume when frozen as it does when liquid. The volume change occurs when it is on the process of freezing/thawing.

But, folks, come on. If that little of a change effects you're skiing/boarding, perhaps it's time to get out of the game.

bigfoot0922 · Outlaw Joined: 15 Aug 2003 Posts: 212 City: Belmont

projectely4 · Posted: Oct 22, 2003 7:50 am Post subject:

if there was a difference i don't think you'd be able to see a difference.

salmon_tacos · Posted: Oct 22, 2003 9:33 am Post subject:

Leggester,

Density is mass/volume. It has nothing to do with how "hard" something is. Also, water gets less dense as it freezes. I think that might be somewhat unique. The thermal coefficient of expansion is negative within the range of 0-4 degrees Celsius. Above 4 degrees, water does indeed expand with a rise in temperature but not that much.

Anyway, I did some calculations and it looks like water at 40 degrees is about 2.1% more dense than water at 80 degrees. Compare that to your average 80-degree seawater which is 5.4% more dense than the 80-degree freshwater.

So, it looks like a 40-degree temperature drop will have about 39% of the wake diminishing effect that saltwater does.

wakeborder5 · Soul Rider Joined: 12 Jan 2003 Posts: 279 City: Commerce

The change in the density of water when the tempature fluxuates(sp), is not enough to make a noticeable difference, although the difference between the density of salt water and fresh water does make a noticeable change. Although your wake will be smaller in fresh water because the water is more dense, doesn't that mean your wake will be more solid?

Leggester · Posted: Oct 22, 2003 11:46 am Post subject:

ST, easy man. I should have put many moroe smiley faces in.

A point in fact - at some point, as it freezes - not when frozen - it does become more dense. That's why, as Mr Blean stated also, the mass/volume does get greater. That's then the blocks crack - as I have good reason to know Embarassed

salmon_tacos · Posted: Oct 22, 2003 2:11 pm Post subject:

I wasn't trying to go off on you or anything. Actually, only the first part was directed at you because you said, "Please explain 'dense'."

Anyway, when the water expands and cracks your block, it actually gets less dense because:

1. Volume goes up. (obviously)
2. There is not extra mass (conservation of mass)
3. density=mass/volume so when the volume goes up and the mass stays the same, the density goes down.

To summarize my other post: As you go from 100C to 4C, water gets more dense. Then, as you go from 4C to 0C, it gets less dense. 0C is where it freezes. I'm not sure what happens after that. If it's like most other solids, it then gets more dense from 0C to -273C.

eeven73 · Posted: Oct 22, 2003 3:02 pm Post subject:

i love fluid dynamics threads Very Happy

MrBlean · Posted: Oct 23, 2003 4:51 pm Post subject: Denser than water

davidgree1 · Newbie Joined: 15 Apr 2003 Posts: 29

Fully weighted, my boat runs at a lower rpm at 21mph in cold water then warm water.

MrBlean · Posted: Oct 23, 2003 11:23 pm Post subject: Ahaaaaaa!

salmon_tacos · Posted: Oct 24, 2003 6:28 am Post subject:

Woohoo! I got a hundred! That's an A+.

I am quite the scholar. Very Happy

MrBlean · Posted: Oct 24, 2003 7:12 am Post subject: Freezing

vette74 · Posted: Oct 24, 2003 7:52 am Post subject:

davidgree1 wrote

mcfatty · Addict Joined: 13 Jan 2003 Posts: 725 City: Cookeville

mr blean

everything you say sounds good, real good but what is your background for such knowledge.

Also would a low pressure system or a high pressure system effect how high and far I can jump off the wake?

davidgree1 · Newbie Joined: 15 Apr 2003 Posts: 29

I am using a gps to guage speed as my venturi pick-up clogs alot. How much more H.P. will the engine develop at lower water temp? The temp of my lake is about 52 now. The high is 85 in the summer. Boat is a Toyota.

MrBlean · Posted: Oct 24, 2003 9:41 am Post subject: How dense can it get

As you can see from the table below, water is at its maximum density (and hence minimum volume) at 4 degrees C. (In fact, the precise figure is 3.9 deg C). Above and below that temperature it is less dense and hence its volume is greater i.e. it EXPANDS. Interestingly, according to this table, it appears to continue to expand as the temperature reduces from zero which explains why pipes and un-winterised engine blocks crack if the residual water in them freezes and the temperature drops further

Given that the change in density from 10 deg C to 30 deg C is 4Kg/cu metre i.e 0.4%, it’s kinda hard to believe that this would have any significant effect on how deep the boat sits in the water and hence that this has any noticeable effect on the wake.

Whilst the change in density of fresh water from 10 deg C to 30 deg C is only 4Kg/cu metre, the change in density from fresh water to typical sea water is 27.3 Kg/cu metre, nearly seven times as much. Therefore, the salinity of water has a significant impact on its density and may well affect the depth at which the boat sits and hence the wake.

If you wanna work it all out for yourselves, consult:

http://www2.cwr.uwa.edu.au/~prescott/ole107/physical_properties.pdf

And mcfatty, I think a lake with a downhill slope would have more impact on your ability to get great air than the air pressure itself. Very Happy

FYI, I am a degree qualified engineer from the UK.

davidgree1 - if you have an inboard, its operating temperature is regulated by the thermostat so the temperature of the lake water will have mimiumal effect. If it's an outboard, running warmer may increase efficiency by a small amount but variations in the temperature and humidity of the air inducted into the engine is likely to have a greater impact.

mcfatty · Addict Joined: 13 Jan 2003 Posts: 725 City: Cookeville

mrblean

I see you talking and yet I hear nothing. Laughing

break it down for me brotha.

when is it the best wake hot or cold?

Ocean Rider · Wakeboarder.Commie Joined: 24 Jun 2003 Posts: 1597

i dont get it lol Confused

MrBlean · Posted: Oct 25, 2003 3:18 am Post subject: Hot or cold?

mcfatty - quick answer is that there is highly unlikely to be any difference in wake between warm water and cold water. If there is, it will be minimal. However there is almost certain to be a difference between fresh and salt water. Fresh water will produce a bigger wake as the boat will sink considerably more in fresh water than salt.

All to often we see opinions expressed on this site that are based on perception without any "scientific" or logical explanation as to why it happens or could happen. In terms of difference in wake height, who has been out there with a tape measure and actualy physically measured the difference in wake from one day to another? Quick answer- NOBODY. It's all opinion-based.

All I have done is provided technical answers to a couple of ideas that people have put forward as to why they think it may be possible to get an increase in wake height with different water temperatures.

What I have provided is a technical explanation as to why, for the same boat weighted equally, there is almost certainly a difference in wake when used in salt then fresh water. What I have also explained is that the temperature of the water does have some small effect but it's so small the chance of being able to notice it isn't worth thinking about. This is exactly what the more "thinking" contributors to this thread have postulated.

But if someone wants to prove that there is a genuine effect between wake height and water temperature, let them show the evidence to prove it. Opinion alone doesn't cut much ice around here.

That help?

P.S. The table was to explain two things:

1) That water expands considerably BEFORE it freezes in response to Mr. Mutt's incorrect statements on the subject and to respond to salmon_tacos' query on what happens to the density below zero deg C.
2) The change in density (and hence the degree of flotation it provides) changes so little between 10 deg C and 30 deg C that you almost certainly won't notice the resulting difference in wake height. Could you spot a 0.4% change in something? Unless you are a very gifted individual, I suspect not. This is the diffenernce in bouyance between water at 10 deg C and water at 30 deg C. However, you probably would notice a 3% change in something which is what the difference in bouyancy is between fresh and typical sea water.

Inggy · Posted: Oct 25, 2003 9:45 pm Post subject:

all this is way over my head. I think that the original question was does the boat wake vary with temperature.

I think all that was wanted was a yes or no....

I'd say no though

MrBlean · Posted: Oct 26, 2003 12:46 am Post subject: Yes or no

So, Inggy, what would you have concluded if 100 people had responded with 50 saying yes and 50 saying no with no logic or reasoning for other statement? 100 opinions that count for nothing - like a lot of contributions you see on this site.

flip cutter · Outlaw Joined: 19 Aug 2003 Posts: 124 City: wilmington

big difference bt salt and fresh. i wonder if temperature effects each differently, just add more weight for the chilly water.