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Old Jun 02, 2011, 08:09 AM
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Pro Boat Apache Catamaran 24" EP RTR, Discussions / Modifications

Hi guys and girls.

I will be buying a new battery pack within the next hour for my new stock, standard Apache Catamaran 24" EP RTR.

I'd like to know what you would propose I get, regarding capacity. I will obviously be buying battery packs of the NiMh 6-Cell (7.2V) type.

Secondly, will it be better to buy one large-capacity battery pack or two smaller sized battery packs?

Thank you and best wishes.

George.
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Old Jun 02, 2011, 08:54 AM
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I will buy Lipo's from the start. You will go there later anyway. With Lipo's you get more MAH for the same weight, and a bit more volts to the motor. Hope this helps.

But if you want to stay stock, I would go for a 3300mah pack
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Old Jun 02, 2011, 10:07 AM
Boaters are nice people.
Sneek, Netherlands.
Joined May 2004
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Hi George,

Only if you like high maintenance batteries, the choice for NiMH is obvious...

I agree with Sarcfan; get a 2S 5000mAh 20-25C lipo pack and either change the ESC for one that has an adjustable Low Voltage Cutoff (LVC) so you don't damage the lipo by deep discharging it, or use a lipo guard, that will flash when the voltage drops below the desired value.

When I was running NiMH, for many years, my time doing maintenance was longer than my runtime on the water, at the penalty of dead cells after a winter of 'neglect'.
With Lipo's I have alot of time on my hands to run the boats instead of tampering with NiMH's...

When you get lipo's be aware of the long runtimes you'll get; the 550 motor wil have to be broken in, so the brushes fit onto the commutor snugly, not breaking in the brushes could result in a ruined commutor in the very first run.

Breaking in new brushes is done by submersing the motor in water and run it on a low voltage (2-3V) until the water starts to turn darker, take the motor out and check if the brushes have a good fit, dry the motor (compressed air or a night in a warm dry place) a tiny (!) drop of oil on the bearing and you're good to go.

While you're at it, add some heatconductive past between the cooling coil and the motorcan and cover it with a piece of shrinkwrap so it's pressed onto the can.
Also add brushtab cooling, your motor will thank you with a long life.

Regards, Jan.
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Old Jun 02, 2011, 10:22 AM
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Have been using Li-Po's on this stock system, which wokred fine, but they were old cells, so the tabs started breaking off, etc. so I threw them away yesterday.

Since I'll not be upgrading too soon, I had to buy some NiMh packs.

So I bought;

1x CHARGER : http://www.prolux.com.tw/product.php...&cid=44&pid=24
1x 1800mAH PACK : http://www.hpieurope.com/piw.php?lang=en&partNo=101930
1x 3300mAH PACK : http://www.yuntong-batt.com/v2007/prodisplay.php?id=126

Busy charging the 3300mAH @ 4Amps... Still 9 minutes to go then off to the dam.

Will provide feedback tonight on the first pack.
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Old Jun 02, 2011, 10:26 AM
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pompebled, I like the "voor" and "na" since it is very close to my mother tongue... Afrikaans...
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Old Jun 02, 2011, 10:31 AM
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How efficient is the coil-cooling system, because I do'nt like/trust it too much?

I'm also not too happy with the "water pressure" inside the cooling hoses. I feel/think the flow rate is too low. What possible solutions are there for upping this?

I think I should look into the brushtab-cooling as well. Looks like a good idea!
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Old Jun 02, 2011, 10:43 AM
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Hi George,

As Afrikaans has roots in Dutch, that's no wonder...

A cooling coil is only sufficient if the set-up doesn't require a lot of cooling, because the contact surface between the can and the coil is rather small, hence my suggestion to add heatconductive paste.

Most boat applications will generate substantually more heat.

A full jacket is much more effective and in combination with brushtab cooling should keep your motor well within the safe thermal range until it's worn out, unless you grossly overprop it, no motor can cope with that for long...

The motor in the picture is a 700 Neodym, used in a 12 cell set-up.
When the water is still cold in spring, the cooling is so effective, the moisture trapped inside the taped off hull condensed on the motor...

I have a tutorial and pictures on how to go about making these cancooling, if you want it, send me your emailadress by PM and I'll send it over.

Regards, Jan.
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Old Jun 02, 2011, 10:52 AM
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If you need more flow, reposition the intake.

It should be in the upper right quadrant, looking at it from the rear.
A little heat should do the trick I suppose.

Also check the tube for burrs by drilling it with a slightly larger diameter drill, more diameter equals more flow.

Lower the arch in the silicon tubing, every inch the pressure doesn't have to overcome is a gain in flow.

Reduce the length of tubing inside the hull, the drag in silicone tubing is substantual.

In boats where long tubes are unavoidable, I use 4 mm thin walled aluminum piping for the bulk of the distance and only short pieces to make the connections to the ESC and motor.

Keep in mind, don't overdo it on the flowrate, a steady drizzle works better than a speeding fountain...

Regards, Jan.
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Old Jun 02, 2011, 01:38 PM
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Motor break in.

Here's two images of the water before and after breaking in the motor. Did not take too long.
About 5 minutes before the water's colour changed.Name: Water before motor running in..jpg
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Description: Water before motor running in.Name: Water after motor running in..jpg
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Description: Water after motor running in.
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Old Jun 02, 2011, 02:18 PM
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Originally Posted by pompebled View Post
Hi George,

As Afrikaans has roots in Dutch, that's no wonder...

A cooling coil is only sufficient if the set-up doesn't require a lot of cooling, because the contact surface between the can and the coil is rather small, hence my suggestion to add heatconductive paste.

Most boat applications will generate substantually more heat.

A full jacket is much more effective and in combination with brushtab cooling should keep your motor well within the safe thermal range until it's worn out, unless you grossly overprop it, no motor can cope with that for long...

The motor in the picture is a 700 Neodym, used in a 12 cell set-up.
When the water is still cold in spring, the cooling is so effective, the moisture trapped inside the taped off hull condensed on the motor...

I have a tutorial and pictures on how to go about making these cancooling, if you want it, send me your emailadress by PM and I'll send it over.

Regards, Jan.
My point exactly. There's too little surface area in contact with the can of the motor to sufficiently cool it, that's why I'm not too fond of the coil system.

What do you think of my idea of a cooling system? (Image attached below.)

The outside solid piece is drilled/machined out of aluminium.
Then the holes are drilled through as indicated.
And then a minimum of two copper pipes are pushed through these holes with some heat conductive paste.
If need be more copper pipes can be installed and linked up, but I doubt it'll be necessary.

I have actually built one of these before and the mass increase was'nt too much. Just never had the water flowing through it since the small brushless motor's heat was already dissipated through this heatsink.

More holes are drilled through the aluminium to decrease mass as well as increase the surface area for cooling.

I'm also think of adapting the current ESC's heatsink so as to watercool it as well - Your opinion on this? The stock one is too small to drill through it so one can only fix a modified piece of heatsink to it, that works on the same principle as above.

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Old Jun 02, 2011, 02:47 PM
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Originally Posted by pompebled View Post
If you need more flow, reposition the intake.

It should be in the upper right quadrant, looking at it from the rear.
A little heat should do the trick I suppose.

Also check the tube for burrs by drilling it with a slightly larger diameter drill, more diameter equals more flow.

Lower the arch in the silicon tubing, every inch the pressure doesn't have to overcome is a gain in flow.

Reduce the length of tubing inside the hull, the drag in silicone tubing is substantual.

In boats where long tubes are unavoidable, I use 4 mm thin walled aluminum piping for the bulk of the distance and only short pieces to make the connections to the ESC and motor.

Keep in mind, don't overdo it on the flowrate, a steady drizzle works better than a speeding fountain...

Regards, Jan.
I removed all burrs before running it for the first time. All is clear.
I lowered / removed as much arches and curves possible.
Shortened all tubes to as short as possible. (Scored about 40mm of tubing.)

The flow rate is actualy fairly good. I also bevelled the intake more so as to allow for a greater intake surface area. I want to reroute the outlet from the side to the rear and seal off the side outlet. I removed the intake from the rudder now. I'm thinking of drilling another hole into it, fit another intake pipe that's bigger to the front of the prop as opposed to the original one behind the prop. Then take a y-piece or a t-piece to join the two intakes into one and then feed the cooling system.

Looking at the current flow rate I think I might need higher flow if/when I mod the motor and ESC for better water cooling.
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Old Jun 02, 2011, 02:48 PM
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Instead of that, just run a cooling jacket that is short enough to not go over the can vents. If you can't find one, or there are vents everywhere just cover the can with heat shrink tubing before putting the cooling jacket on it.
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Old Jun 02, 2011, 03:07 PM
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FEEDBACK ON THE FIRST RUN THIS AFTERNOON AFTER PURCHASING THE NEW BATTERY PACK :

Installed the freshly charged 3300mAh battery pack.
The power was amazing. Run time was about 10 minutes and the ESC did not disarm, for the battery still had plenty power.

The battery pack, ESC and motor was definately fairly warm to the touch. Motor being the coolest.

After giving all some time to cool I plugged the battery back in and tested throttle. All of a sudden I heard some loose things shattering on the inside. Opened up and found the "things" in the images below lying around in the hul, shattered to pieces. Any ideas on what this is / might be? The motor still runs, but when decreasing the throttle to 0% it suddenly stops, jerking the motor with a VERY SUDDEN stop. Not sure if this is correct - Doubt it.

I'm also not happy with the time it takes for the boat to plane. Any suggestions as to improve this and getting it to plane faster?

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Old Jun 02, 2011, 03:11 PM
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Sneek, Netherlands.
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Hi George,

The fact it took so short to turn the water dark means the motor has rather soft brushes, which in turn means it is a rather 'hot' motor with a shorter lifspan than a standard 540 three pole motor.

These took me about an hour and an half to break in at 3V, most of these motors are still running.

I also used hotter motors in my competition boats which lasted just a race season of 18 heats per motor and a couple of testruns, before they turned 'brushless'...

A variation on your theme is to solder cooling pipes directly onto the fluxring of the motor, as in the picture I added.

The fluxring was not on the motor during the soldering ofcourse, in order to prevent the 'baking if the magnets'...

These 'hot' motors (25.000 rpm on 8,4V) only had to survive 6 minute runs, so the limited cancooling combined with the brushtab cooling was sufficient.

The fluxring moved on to the next motor when the brushes had been used up.

What size is/was that ring in your pictures?
Does the motorshaft have excessive axial play?

Regards, Jan.
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Old Jun 02, 2011, 03:30 PM
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Originally Posted by wparsons View Post
Instead of that, just run a cooling jacket that is short enough to not go over the can vents. If you can't find one, or there are vents everywhere just cover the can with heat shrink tubing before putting the cooling jacket on it.
Will the heatshrink not insulate the heat generated by the motor from the water that is actually supposed to cool it?
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