Ntn-600 Modification and several questions

[huseyinozsut]

Hi,

I am new to the fast boats. I have an 32 years old scale boat, around 11 inch long. It's all electronic was dead. Since it meaned alot to family (lot's of good memories) I repaired and got it much faster. Added navigation lamps and a projector etc. etc. I completed that project. Now it is time for a fast boat!


Now, I am upgrading NTN-600. I got 120A Hobbyking ESC, I will use the original motor, which is 2858kv and use 4s lipo battery. I will add a mini dc pump and again navigation lamps to this boat also. I bought transparent screws and nuts to mount canopy hatch. I will mount a led to each screw, and hope the screw and nuts will pass the light to outside. And I don't trust the water cooling system of NTN-600. I will use a mini pump for it. Both navigation lights and pump is radio controlled (I have 6ch receiver).

The thing I don't know is, which battery should I use? I am looking 4s batteries between 4000mah - 5200mah. I found Multistar 5200mah 10C battery; but I have some doubts about it, since it has a 10C discharge rate. But it has light weight. So I could not decide. I guess my burst consumption would be more that 52A. So, I guess this battery is not for me. If you say it won't be a problem, I'll buy this battery. If it is a problem, I will look at least 20c batteries...

[785boats]

Firstly, the kv of that motor is 2881 & 4s is a bit too much for it, giving you over 42000 revs. The driveline in that boat will most probably flog out in a pretty short time.
The specs for the boat call for a 3s pack of 4000mah. That will give you around 32000rpm unloaded which is a much better number to work with for a beginners sport boat.
They only list a 20C pack but a 40c pack or above would be better.
The Multistar packs are too low in the C rating & will not deliver the power required.
Something like these would work well, without spending too much money.
http://www.hobbyking.com/hobbyking/s..._3S1P_45C.html

Or this depending on what type of connector you wish to use.



http://www.hobbyking.com/hobbyking/s..._3S1P_40C.html

Of course, you can change the connectors yourself to whatever matches the rest of your system.


Larger capacity batteries will be heavier & may upset the handling characteristics of the hull. But you can always try if you want. But check the physical dimensions first to see if they fit.
The Zippy 'Compact' series are also a good pack with different dimensions to the standard packs

You will be surprised at how efficient that water pickup really is. You may not need the pump.
Your other mods with the lights sound really cool. Are you anticipating some night runs?

Cheers.
Paul.

[huseyinozsut]

Thank you for your enlightening answer!

Actually I had doubts also with the motor. Maybe I can change the motor also and buy a lower kv motor. 4S batteries would probably increase my use time. I read somewhere, lower kv higher voltage systems would give better usage time compared to a 3s sytem with higher amp battery. (4s 3000mah and 3s 4000mah batteries can be counted as equal, 2160kv motor in 4s and 2881kv motor in 3s would come up with same rpm; but as said, 4s system would give more usage time, is it true?)

Here in Turkey, I can not find everything I want for cheap. They are really expensive here. So I buy used parts generally. The ESC I bought was certainly an overkill; but I did not have any other choise. I wanted reverse also and the original ESC does not have. Then I tought, since I have a esc that supports higher voltage, why not hunt for a 4s battery?

In first run, I tried the boat with 2x3300mah 3s batteries (used parallel), mounted on the original mounting place (middle of the boat, just ahaed of motor). My two 3s batteries weight 500g. The boat could not lift it's nose up and could not go that fast, much water splashing at front. I guess 500g was too much for that place.

Also I saw several modifications made to NTN-600. All of them used two batteries each side, near motor to bring center of weight backwards. So I thought, this boat was not designed well at the beginning. My plan was also to put ESC ahead of motor (to battery compartment at original) and use two batteries each side near motor (this will put the batteries weight 5-15cm back, lead a lighter front and help the boat to lift her nose up!) If extra weight is needed in left (since ESC was on left at original, which means, left needs an extra weight) My RC switches and 7812 voltage regulator for leds will be on left.

I can use two 3s batteries working parallel, or use two 2s batteries working in series. Would you reccomend a motor upgrade and switch to 4s? Or it is not needed? I also don't know the usage time even roughly with a 4000mah 3s battery pack. Would it make 30 mins? or am I asking for too much?

I actually like the idea of watercooling at NTN600. It gets the water not from the rudder, it takes the water directly under the hull; but this brings one problem. After swim, cleaning the cooling system will be seriously hard. Propellers water push won't cause any circulation. Also, after the first run, I noticed that my motor was seriously heated up. I do not want to burn anything. Pump would ensure the waterflow even in steady condition, so even if I heat up the motor exessively, I can stop and pump can cool down the motor. At first few runs, pump is my insurance. After I am sure about the system, I can take it out (80g pump, 20g switch, total 100g is not negligible) and use it with a much thinner hose to mount it to water intake inlet, just only to clean the cooling system in bathtub.

I don't have much free time even in weekends. I can not go to a lake or a pond before afternoons, so at most of the times I use my boats at and after sundowns. So navigation leds are important for me. I hope transparent screws will do the trick. It was very hard for me to find them.

[785boats]

I use one of these on 4s with great success. But you will need to find a 29mm water jacket. 'TP Power' make them for their motors.
It should bolt straight onto your mount, but just check that the bolt spacings on your mount are 19mm first.

http://www.hobbyking.com/hobbyking/s...ion_29mm_.html

http://stores.ebay.com/kwboater?_dmd=1&_nkw=29mm+cooling+jacket

Two batteries side by side would be the best option as you suggested.
.

[huseyinozsut]

I bought dr mad thrust motor and 29mm water jacket!

And I found a very interesting thing, because of shipping prices to Turkey, buying two of these

http://hobbyking.com/hobbyking/store...APPROVED_.html

costs only 25$ more than buying 4000mah 25C Zippy Compacts.


Zippy compacts weights around 30g lighter than nanotech shorty at total (15g each).

- A cheap 3s 4000mah battery would weight around 320g I guess. These batteries will weight 400g at total. I have 80g extra weight there.
- My new ESC is 200g. My old ESC was 90g. I have 110g extra there.
- Leds, cables, canopy mounts, RC switches will cause me another 60g I guess.

So I will have 250g extra weight compared with the original design. But my new motor is like 2 times stronger than the original. So I can change the propeller if needed. I hope I can compansate the increase in weight. Any estimation about that? Also any rough estimation about use time?

[huseyinozsut]

Hi,

I completed the setup, except I broke the flexhaft when trying to fit the coupler... My flexhaft is square end type and 4mm metric. I found them on an online store with a huge shipping rate to my country. So I will buy some propellers with it also (shipping price does not change).

My boat is 250g havier, has an motor which has nearly the same max rev with the original; but twice as strong. My original prop was TFL 435, which is bronze, has 35mm diameter and 1.4 pitch.

My plan is to use CNC Magnalium 7075 propellers, like 42mm or 48mm with 1.4 pitch. With much higher motor power, I thought increasing diameter would not hurt. I don't know how to sharpen or balance a propeller, so I thought these CNC ones would be good for me. I know propellers are somewhat "test and see" stuff; but if I am at a totally wrong path, if you can warn me, I will be very pleased.

Roughly what I done is below:
I soldered battery connectors to make a serial connection.
IMAG1024.jpg

I made my own 2 x 2s = 4s balance cable
IMAG1025.jpg

On right, behind the servos there are two rc relays. One is for pump, one is for leds. On left, there is the Rc receiver, and emitter of wireless battery alarm.
IMAG1027.jpg

There is a chip mounted on a copper surface. That is Lm7812, a simple voltage regulator. 12-30V in, 12V out. 12V out is connected to relays.
IMAG1028.jpg

Every led colours are in series. Then they are connected in series with appropriate resistors, then connected to each other parallel. On front screw, there is a mini power led. On back, there are two white leds mounted on the pole I built. That pole includes cables to leds, receiver cable (with copper end) and battery alarm emmitters cable.

http://s29.postimg.org/g2w3qphtz/IMAG1031.jpg

http://s29.postimg.org/8lmwbhsav/IMAG1030.jpg

http://s29.postimg.org/txue96c93/IMAG1032_2.jpg

[huseyinozsut]

Hi again!

I completed the boat and made a few test with it. It is much more balanced now. Though, it tends to turn right. An extra weight to left-back side will most probably do the trick; but I could not test this; because season here, has ended. I modified my tx. Now I can get 450-500 meters range without any amplification.

Now I'm building a U shaped rescue boat. And I will fit a fpv system to it. When I was making my tests, I rolled the boat several times. If these accidents happen 300-350 meters away, there is no chance for me to see either the rescue boat or NTN600. So rescue boat will have a camera on it, so I will be able to navigate.

Then I thought, what about having one more transmitter and camera? Maybe I can modify my boat for FPV?

In near future I'll also become a rc plane hobbyist also. So I thought, I should by a mid-range Tx/Rx for being able to use in any flying object in near future. Now I'm looking to 1.2ghz FPV Tx/Rx. Can anybody suggest a good one? The one's I look has over 5km range ON AIR. But we are on land. The range probably will be much less on land. But how much?

Also applying telemetry with FPV is much easier. No need to a transmitter for that. There are some cheap cards, that can show all those informations on the video!