Had an interesting experience

[CraigP]

Speed, I have to stop you here and try to clear up some very misunderstood thoughts about “different water”. There is fresh water and salt water. Both of these can be moving water, as in a current. If the current is going your direction, you will pick the speed of the current up in your boat, and you will get propulsion thrust speed plus the current speed. Just the opposite if the current is moving against you.

That’s not the point you are making, but I thought I would lay it all out. You’re saying because of the increased density of salt water, that the propellor has to work harder to displace the water, or cut the water. You are correct in that thought, it does take additional power to cut higher density water. What you’re NOT thinking about is how higher density water aids your craft. Because it weighs more, more of your boat is out of the water and you don’t have to put in power to pick it out of the water to the degree of fresh water. Also, because of the higher density, things “skip” more easily across higher density water, also reducing power demands. In the end, boats actually can travel faster in salt water given the same relative calmness to fresh water. It actually takes less power for a given speed, because of the drop in hull resistance due to the higher density water. The prop is but one element on the negative side, while there are more things on the positive side.

Most of us don’t like salt water because it’s so hard on the boat in terms of corrosion. It’s a PIA to clean it and maintenance efforts are much higher. Also, there is only ONE set of physic equations. There are different coefficients to the expressions defining different sets of circumstances, but that’s it.

What you think you are observing just isn’t due to the things you think they are. I hope you will read this, and realize, while you are a naturally bright person, you have some holes to fill in. But we just aren’t buying your conclusions because they are based on a faulty premise of understanding. But keep thinking about it, and try posting some of your perceptions as questions because there are many here with an abundance of experience. Have fun boating and figuring it out, because that’s where the joy in the sport truly lays.

[kfxguy]

Speed, I have to stop you here and try to clear up some very misunderstood thoughts about “different water”. There is fresh water and salt water. Both of these can be moving water, as in a current. If the current is going your direction, you will pick the speed of the current up in your boat, and you will get propulsion thrust speed plus the current speed. Just the opposite if the current is moving against you.

That’s not the point you are making, but I thought I would lay it all out. You’re saying because of the increased density of salt water, that the propellor has to work harder to displace the water, or cut the water. You are correct in that thought, it does take additional power to cut higher density water. What you’re NOT thinking about is how higher density water aids your craft. Because it weighs more, more of your boat is out of the water and you don’t have to put in power to pick it out of the water to the degree of fresh water. Also, because of the higher density, things “skip” more easily across higher density water, also reducing power demands. In the end, boats actually can travel faster in salt water given the same relative calmness to fresh water. It actually takes less power for a given speed, because of the drop in hull resistance due to the higher density water. The prop is but one element on the negative side, while there are more things on the positive side.

Most of us don’t like salt water because it’s so hard on the boat in terms of corrosion. It’s a PIA to clean it and maintenance efforts are much higher. Also, there is only ONE set of physic equations. There are different coefficients to the expressions defining different sets of circumstances, but that’s it.

What you think you are observing just isn’t due to the things you think they are. I hope you will read this, and realize, while you are a naturally bright person, you have some holes to fill in. But we just aren’t buying your conclusions because they are based on a faulty premise of understanding. But keep thinking about it, and try posting some of your perceptions as questions because there are many here with an abundance of experience. Have fun boating and figuring it out, because that’s where the joy in the sport truly lays.

Good explanation

[Speed3]

I love the logics Craig it sound very good and seems to make sense.

I just want to share my view on the boat lifting easier. The denser water causes the boat to lift easy I agree.

So maybe the hull might lift to the max say 40 to 45mph in salt water.

While in fresh water it may have the same lift at say 55 to 60mph.

My view on this is the hull will reach it limit of stability much quicker in salt water. Which based on what I am seeing would seem to be reasonable thinking.

And because of the much denser water being harder on the prop. It would take a smaller prop with less pitch to push the shaft and the coupler to the torque limit. Which again I have found to be the case.

Example I followed the voracity turning thread because I was thinking of getting one and I was researching stuff that can be done to it.
I saw where someone used an octura x457 and x460. Big props 55 to close to 60mm in diameter on 6s with the leopard 4092. And the leopard has more torque than the stock voracity motor.

Actual example here in our waters. I have seen someone break the solid piece that holds the prop on the voracity with a sharpen and balance octura x450 2 blade. And that is with the stock voracity motor.

I myself have found the m545 with the leopard 4092 1730kv on 5s is pushing an upgraded octura coupler and an upgraded shaft to they torque limit. Anymore torque and the coupler can grip the shaft at full throttle.

This is what happens when you run in the denser waters in my area.

Thanks for you patients and feedback.

[vinnyp]

Speed,
I run my rc boats in salt water all the time, in a bay that is just a short hop from the Atlantic Ocean. I cant blame my lack of speed due to the salt content or denser water. I admit to not be able to run as fast as other members of this forum, simply because of my minimal experience and set ups. I am quite certain that if the speedy guys on this forum were to come and run in the waters in " My area" they would easily achieve the same speeds they get from their fresh water ponds.
I am certain there are places on this Earth where the salinity is unusually higher due to some type of natural phenomenom. Perhaps there is some special reason the salinity of your water is much higher than other places like the Atlantic?

On another note: I have run full sized offshore powerboats in both salt and fresh water and have seen no difference in speed or handling characteristics. In my opinion, the difference between salt and fresh water would be so small, it would be undetectable.

[Meniscus]

So, at risk of interjecting, let me share this. We have all had different experiences each time we go out to the pond. Many times, we try to make assumptions concerning why this is. Most of the time, we are trying to get more speed out of our model. There are many variables that have been identified in this thread already.

As-long-as we admit that there are always differences, then I believe sharing your experiences are good. Please keep in mind that everything from water temperature, the internal resistance for the cells and even the temperature of the cells can have a significant impact.

I have experienced first hand where I have seen gains in speed, even with hard water based on what I believed was my fine tune adjustments. However, every model, even those boats of the same model, will have differences in the way the run and react to different props. I've hand-wound motors just to find out that on some days, they run faster on the water with a different prop on different days.

The good news is that you are seeing cool temps. If you would like to increase the speed or change the way the model behaves, be sure to let the folks here know.

Regarding D-wind motors, best practice is to maintain lower timing. The extra heat may not become apparent until you start to swing a larger prop or one with more pitch, but there's a strong probability you will see more heat than if you set the timing lower. Just keep this in mind as you continue to enjoy the hobby. If it shaves off a couple MPH on one day or the next, try not to stress it too much. Also, if you decide to try to make quantitative assumptions, keep in mind that many, many variables come into play.

If you do not want to discuss additional factors that may improve performance (in speed, handling, runtimes, etc.), then I would recommend focusing on sharing what it is that you want to achieve. Otherwise, it is safe to say that you are happy with the reliability from the motors you have referenced. A statement like that is most useful for other readers and those who cannot afford to have several motors to test with.

[Speed3]

Thanks everyone who have provided feedback.

[MADRCER]

I know a guy who did 67.9mph in our waters. Fastest ever recorded in our waters.
The physics is totally different here.

Hey Speed, It looks like C-Mac just set the world on fire down in the BVI...Great job to him! You might not want to get that Revolt out there on the water with his boat! Shattered the previous record of 67.9mph you were talking about above. Maybe things are changing down in your area?

[Speed3]

No things are not changing, that's one of my running mates. And I know the setups in those boats.

I cannot disclose the setups but I can tell you those boats have in way more power than anything I have ever read about with a single motor.

Just to give a hint.

Imagine a Neu 2230 with above 700kv on 12s turning props 60 plus mm.

Imagine the speed that boat would do.

[CraigP]

Hmmm, special Laws of Physics, double top secret setups... You just don’t seem to bring much to the forum, other than controversy. I got a boat just like yours, just ran it at 140mph in some special water. I had 4 GPS units in it, all read within 1mph. I can’t tell you any more. Sound familiar? It’s the water that makes it so fast... Special water

[Speed3]

https://youtu.be/BYKEUHkvkx4

This was a race with my revolt vs a voracity with a x452.

Both boats was using 5s.

[Speed3]

The t class boats I think run 10s according to my research. Well those guys run hotter setups than those setups used for the t world records.

[MADRCER]

No things are not changing, that's one of my running mates. And I know the setups in those boats.

I cannot disclose the setups but I can tell you those boats have in way more power than anything I have ever read about with a single motor.

Just to give a hint.

Imagine a Neu 2230 with above 700kv on 12s turning props 60 plus mm.

Imagine the speed that boat would do.

Yes I know C-Mac is one of your mates....that's why I brought it to your attention that he had a fast boat in your area which you were saying just didn't happen down there. BTW PLEASE don't take it that I was trying to pry into ya'lls "fast boat" setups down there at all....Because I got a feeling that I can dial one in decent enough for me to have fun with. But if you get a spare moment read the comments in some of my videos and you will see that I have gladly answered EVERY question that C-Mac has EVER asked me about my Zelos 36 and the other 17,000+ people that have viewed that video has got my set up as well. Heck, if I remember right I usually just go ahead and post my info in plain sight for everyone to see because Rc boating to me isn't fun if you don't have anyone to beat....Lol! I REALLY like C-Mac's comment to me on his video below. Take a minute to read it if you have time.

[Speed3]

Madracer I would like to share info on the setups but I don't think the guys would like it. So I don't. But in the hint that I give with a neu 2230 and 12s and 60 plus mm props.

The motors are like that size, the cell count is 12s and props are big.

You probably saw the 72.7mph cheetah. That have a setup that would have easily been 90 plus. Based on my research.

Madracer I saw your 88mph video with your zelos. That cheetah that did 72.7 mph is setup to be faster than zelos twins with upgrade motors, ESC, prop.

I have seen them boy push motors to the limit where you hit a certain speed with a certain prop and put on bigger props. Diameter and pitch and the boat loses a little speed.

And I am referring to motors like leopards, tp's, castle and 4074, 4082, 56mm cans. I have seen them push to the point where they is no more speed.

I have seen setups run that man would be afraid to try.

70mph was something which couldn't be done.

Those speeds were only possible location where you see those video.

The zelos was hit 63 to 65 max. Highly upgraded. 4082 size motor, 47mm prop about 6s per motor. Couldn't pass 65mph.

When them boy went to that location they boats got more stable and they gain like 7mph to they speed.

So even on our little island the waters affect the speeds greatly.

The water could look flat and when you sail in it when you reach 50mph you have handling problems. Another location the same boat nothing change would be very stable in the 50's.

[MADRCER]

Awesome thanks for the info! I hopped the below little boat up to bring with me on vacation down in the Caribbean later this year, so I got it running 32-33mph here in the States and I was wanting to be solid in the 8-10mph range down there. How fast do you think it will be down there in that area? Stock it was around 19-20mph (US speed) and I figured that it would move about like a sail boat down there if I left it stock in those haunted waters, so I had to do something if you know what I mean.

[NativePaul]

Well I did some amp draw test to compare the salt water in my area to fresh water.

The salt water requires 140% more amps for the same exact setup. I did the test to compare the two waters.

A zelos twin with stock motors is doing a little over 60 max. After upgrading the props.

And I can tell you they know what they area doing the water is the difference.

I don't know if you every hear about the exceed shark2. I read it does 30mph on 3s out of the box.

It does 21 to 22 in our waters.

The stock revolt was said to be approaching 40mph with the stock grim racer 4255 and 4s.

It does about 30 to 31 max.

When using the octura m545 it goes up to 35mph.

That setup I read persons are getting 48mph.

The stock traxxas spartan did 35mph on a good 6s pack.

Same boat I saw videos of it doing 48mph.

I know a guy had a zelos twin, put in 4082 size sss or tp I think the kV was over 2000kv and 6s per motor. I think he had on counter rotating x447. Could not get the boat pass 65 to 66mph no matter what prop he used. And I have seen videos of zelos doing over 90mph with similar setups.

I know guys setup they boat based on setups they see. 90 plus mph setups and the boats get stuck in the 60's.

And because of the much denser water being harder on the prop. It would take a smaller prop with less pitch to push the shaft and the coupler to the torque limit. Which again I have found to be the case.

I know water can make a big difference, but I am mot sure I believe 140%.

Taking it at face value however it sounds like you need to start modding props, Detounging backcutting and reducing the diameter will all reduce the amp draw considerably without reducing the pitch speed.

You should be able to use the same props as others do for the same setups, but cut the props down so they pull the same amps, and get very similar performance in your soupy water.