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Old Jul 12, 2014, 01:59 PM
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Graupner B28 brushless upgrade?

Hi all,

I have just bought an old Graupner b28 with the graupner ultra1300 -9m motor which was running 2x 12v nimh 4000mAh packs .
It has obviously been gathering dust for quite some time and I was considering swapping it out for a new brushless set up with a new 180w or 200w esc..,
anyone any idea on recommending a brushless motor suitable to replace it with more power ect...
and what size lipos to run with it for maximum usability/speed....??
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Old Jul 12, 2014, 02:44 PM
Boaters are nice people.
Sneek, Netherlands.
Joined May 2004
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Hi SF,

The narrow B-28 needs the weight of the 24 NiMH cells to make it run properly, changing to Lipo's may render it undrivable...

The Ultra motors are starting to become a collectors item, build by Plettenberg they were quite expensive (for the price of one motor you could buy a complete RTR boat today).

Designed for flying, the motors couldn't cope with high current and long runtimes (3 minutes tops) before the commutor would start to overheat and shed tin (which you would find all through the boat).

Running a Ultra on Lipo's can be done (very good even) but keep the runtimes short.

As a budget set up, this would be a suitable motor (needs a watercooling jacket!):
http://www.hobbyking.com/hobbyking/s...nner_19T_.html
ESC something like the T-120:
http://www.hobbyking.com/hobbyking/s..._Boat_ESC.html
With a 45 mm twoblade the boat will run about 65 km/h (40 mph+)
Use two 4S Lipo's 5000mAh 30C (or more) wired in parallel (for the weight).

Or; go for a lower KV motor and a higher cellcount (6-8S) to achieve the same result (or faster if you want).
Something like in this video;
A Leopard 4074 1050Kv on 8S turning a 45 mm prop and this ESC:
http://www.hobbyking.com/hobbyking/s...ler_Opto_.html

Graupner B-28 Leopard 4074 1050kv (0 min 36 sec)


The video shows my point regarding the lack of weight.
Also notice the lack of driving skill, as the boat is turned over due to driver error (too much rudder at high speed and turning left with a single prop boat at this speed).
The prop is on the small side, the motor used can tutn a 48mm easily, bigger than that will become problematic for the hull to handle, maybe a 48 mm threeblade would remedy that.

Regards, Jan.
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Last edited by pompebled; Jul 12, 2014 at 05:01 PM. Reason: Addition.
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Old Jul 12, 2014, 02:59 PM
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thanks for the reply, from what I am told the boat has only seen water twice and only once with that motor then it just sat around.
I dont want to go mad, but budget isnt a major concern, was thinking that I
could run much bigger lipos than the old gear, but want a motor that will have plenty of punch as a replacement.

I think ~I will likely have to fit a new motor mounting frame and driveline as the orignal arrangement doesnt really look to be up to the job
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Last edited by sinking feeling; Jul 12, 2014 at 03:26 PM.
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Old Jul 12, 2014, 05:05 PM
Boaters are nice people.
Sneek, Netherlands.
Joined May 2004
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Some pictures of the state it's in when you got it would be nice.

Selling the Ultra/Plettenberg might give you budget for a nice motor.

Keep in mind that 'plenty of punch' in this type of hull has it's limits (rather sooner than later...).

Regards, Jan.
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Old Jul 12, 2014, 06:16 PM
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as requested pictures as bought, I think its in pretty good condition with very little use evident..







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Old Jul 13, 2014, 03:09 AM
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#edit...just saw your addition above before AFTER posting this...



what about this? running watercooled with 200amp water cooled ESC, but not sure on best performance lipo sizes... -

Leopard 4082 -
Max. Current: 120A
Max.Volt: 33V
Max. Power: 3500W
Rotational Speed: 1600KV
Mounting Hole Depth: 7mm
Shaft Diameter: 5mm
Shaft Length: 20mm
Dimensions (Diameter x Length): 39.8mm x 81.8mm
Weight: 485g
running with 2x 4s lipo packs


or

Leopard 4092 -
Specifications
Max Amps: 115A
Max Volt-age: 23V
Max Power: 4200W
KV(RPM/Volt): 1480KV
Resist-ance: 0.097
No-load Current(15V): 3.8A
Mount-ing hole depth: 7mm
Length of extend Shaft: 20mm
Shaft Diameter(mm):5.0mm
Weight: 492g
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Last edited by sinking feeling; Jul 13, 2014 at 03:41 AM.
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Old Jul 13, 2014, 05:08 AM
Boaters are nice people.
Sneek, Netherlands.
Joined May 2004
4,961 Posts
Hi SF,

I checked my drawer with spare motors and it turns out I have the same motor here, the Ultra 1300-9M is the Plettenberg HP 290BM/30/7-9 T:
http://plettenberg-motors.com/estore...-290bm307-p-34
I also added brushcooling like on your motor.

As you can see, the maximum efficiency of these motors is 84%, which is quite high for a brushed motor (compared to the Mabuchi and Johnson motors), but still, 16% of your battery power is converted into heat, which explains the relative short runtimes, before tin starts to fly.
If you turn the prop by hand, you should clearly feel the cogging from the powerful Neodym magnets.

If the batteries still work (after a few charge / discharge cycles) you could run the boat as it is just to see how it performs, mount a Graupner 2318.45K prop, the one in the picture looks smaller (callipers?).
Make a video to have footage to compare it later, against the brushless upgrade.
Also weigh the boat in the current (NiMH) state, to have a reference, if the brushless set-up tends to be undrivable...

Rule of thumb is to aim for 30 - 32000 rpm under load.

http://www.ebay.com/itm/RC-LEOPARD-L...-/301021210806
A 1600Kv motor on 8S would mean 29,6V x 1600 x 0,8 = 37888 rpm, which is rather 'enthousiastic' in my opinion.
A 1600Kv motor is more 6S material.

On 6S, you could even use the 200A Mystery ESC, but you'd have to disable the BEC by pulling the red wire from the connector (lift the plastic tab) and use a seperate receiver pack, or a UBEC and remove the shrinkwrap and level the Fets prior to using the ESC.

Reason for this is the questionable workmanship, usually less than 30% of the Fets physically touch the cooling.
Here's a picture of a 100A version I watercooled, the dull spots on the thermal mat is where the Fets actually touched the cooler:



My son runs the 200A version in his 4S boat and after sanding the Fets flat, it runs flawlessly.
If you decide to go for another ESC, the motor is cheaper here:
http://www.hobbyhot.com/LEOPARD-Mode...tor-IM147.html

A 1480Kv motor on 8S is still very hot:
29,6 x 1480 x 0,8 = 35000 rpm under load...
But, as the hull won't handle large props anyway, you may get away with it
http://www.hobbyhot.com/LEOPARD-RC-M...tor-IM153.html

Regarding the pictures;

Measure the distance between the endbearing of the propshaft and the transom; this shouls be 10% of the hull length, but it looks much less in the picture.

The (very flexible) turnfin sits in a peculiar place, usually, a turnfin sits on the outside, and only gets wet when the boat banks into a turn.

For a hull this size, the use of trimtabs is questionable; none of my boats use them, only when exceeding 50 Mph, they may come in handy to correct the running attitude.

Otherwise: 'Trimtabs are a bandaid for a poor set-up.'

Regards, Jan.
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Old Jul 13, 2014, 05:41 AM
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Hi
the measurement from transom to end of prop is 75mm and
the current prop is a 42mm.
the turn fin is VERY flexible lol.. couldbe change for 2 aluminium turn fins either side but at the same angle as the 2 trim tabs I suppose.
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Last edited by sinking feeling; Jul 13, 2014 at 05:51 AM.
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Old Jul 13, 2014, 05:48 AM
Boaters are nice people.
Sneek, Netherlands.
Joined May 2004
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Quote:
Originally Posted by sinking feeling View Post
Hi the current prop is a 42mm.
The previous owner was obviously aware of the thermal limitations of the motor.

Run it with the 42 mm prop and see if a 45mm makes a lot of difference (which it will...).
Keep the runs short (2 minutes) and check for heat build up after that runtime.

Regards, Jan
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Old Jul 13, 2014, 05:59 AM
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would a turnigy aquastar 180amp work better.
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Old Jul 13, 2014, 07:21 AM
Boaters are nice people.
Sneek, Netherlands.
Joined May 2004
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Quote:
Originally Posted by sinking feeling View Post
would a turnigy aquastar 180amp work better.
Better than the 200A Mystery, you mean?

If the Fets are sanded into one plane and the watercooling works, both ESC's will work as advertized.

Before deciding on an ESC, you need to know which motor and which Voltage you're going to run.

If you go for 8S, this ESC should work fine, provided you don't overdo it on the prop:
http://www.hobbyking.com/hobbyking/s...ler_Opto_.html
Otherwise the bigger 180A version is in order:
http://www.hobbyking.com/hobbyking/s...ler_Opto_.html
Get the programming card with these ESC's,

The YEP ESC's are re-labeled Sunrise ICE ESC's:
http://www.sunrisemodel.com/showproduct.asp?id=520
The link is to the flight version, but you see the similarities.

Regards, Jan.
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Old Jul 13, 2014, 08:16 AM
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why all hobyking ESCs? I thought they had bad reliablity issues?
the turnigy 180A is cheaper too?
so if I go with this set up...is here anything you would cnsider wrong or going to fry it? I want to try and get it right first time ish...

replace the plastic turn fin for 2x aluminium fins either side at a 45 degree angle from horizontal (probably max I can get due to the positioning of the trim tabs.)
1x Leopard 4082 1600KV brushless with water cooling jacket
1X watercooled motor mounting frame
1x 180A Turnigy Aquastar ESC
1x 45mm brass prop
2xTurnigy 5000mAh 4S 40C

or should I be looking at a 48mm prop?
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Old Jul 13, 2014, 10:28 AM
Boaters are nice people.
Sneek, Netherlands.
Joined May 2004
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Quote:
Originally Posted by sinking feeling View Post
1) why all hobbyking ESCs? I thought they had bad reliablity issues?
2) the turnigy 180A is cheaper too?
3) replace the plastic turn fin for 2x aluminium fins either side at a 45 degree angle from horizontal (probably max I can get due to the positioning of the trim tabs.)
4) 1x Leopard 4082 1600KV brushless with water cooling jacket
5) 1X watercooled motor mounting frame
6) 1x 180A Turnigy Aquastar ESC
7) 1x 45mm brass prop
8) 2xTurnigy 5000mAh 4S 40C

9) or should I be looking at a 48mm prop?
Hi SF,

1) Hobbyking is a re-seller, any issues with ESC's come from the manufacturer, who usually try their best to resolve things.
The T-120 and T180 are among the most reliable ESC's in their price class, usually it's user error/abuse when something goes up in smoke.
Even the cheap Mystery ESC's which I adapted by adding a watercooler still work after years of service.

2) The T-180 is a 6S Max ESC, not much good if you're going for 8S.

3) A single turnfin on the right side is sufficient, left hand turns are wide at best, try turning narrow at speed and you'll flip the boat.

4) As mentioned earlier, 1600Kv on 8S is asking for trouble, in reliability, wear and tear and handling.
The 37888 rpm under load becomes momentarily 47000 rpm when the boat jumps over a wave, putting enormous strain on the drivetrain and the ESC.

5) A watercooled motormount isn't really necessary for an inrunner with a fullsize cooling jacket, but it won't hurt and the rear support ring is a nice feature.

6) You'll have to provide a link to that ESC, as the Aquastar is 160A and the next size is the Aquastar 200A:
http://www.hobbyking.com/hobbyking/s...rless_ESC.html

7) Unless you are skilled in balancing and sharpening props, I'd use the Graupner 2318 series to start with and get a (sharpened & balanced) brass or aluminum one once the boat is dialed in properly.
Brass props containing Berillium need to be worked on with extreme caution as it's highy poisonous!

8) No problem, a higher capacity, with the weight in mind, would work better though.

9) See 7), start with the carbon Graupner props and see what size works best.

I can't stress it enough; aim for 30000 rpm under load, as a 47000+ rpm SAW set-up in the B-28 will not make you a happy boater!

Regards, Jan.
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Old Jul 13, 2014, 10:52 AM
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Hi, sorry for the confusion- my bad - it was this180A turnigy ESC -

http://www.hobbyking.co.uk/hobbyking..._Boat_ESC.html

didnt notice that it was 6s too..
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Old Jul 13, 2014, 11:08 AM
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so if I modify my spec as follows -

1x Leopard 4082 1600KV brushless with water cooling jacket
1X watercooled motor mounting frame
1x 180A Turnigy ESC
1x 45mm prop (you can buy ready sharpened and balanced props mail order?)
2xTurnigy Nano-Tech 6000mAh 3s/11.1v 25c-50c
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