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Jan 04, 2012, 04:11 AM
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DIY Brushless outrigger

hi there
i have recently just built a outrigger out of my own design.
My problem is once it starts planing the throttle curve gets flatter (pretty much the boats not going as fast as i thought). My setup is a 3600kv motor, 60a ESC 2600mah lipo 20c, Graupner carbon hydro prop 29mm dia. At the moment the speeds are around 40-45kph. I have also noticed that it dosen't create a rooster tail. Any ideas on how to bring the speed up ?
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Jan 04, 2012, 08:17 AM
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wparsons's Avatar
How big is the hull? You mention 2600mah lipo, how many cells? A 2600mah 20c pack is only happy giving 50a best case, and is definitely undersized for a 2845 motor.

Any pictures of the rest of the hull?
Jan 04, 2012, 09:03 AM
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bill34207's Avatar
Photo 1 showing the strut looks to be a bit negative in attitude. This will cut down on rooster tail and probably over lift the rear.
As for speed increase I don't know if any faster would be a good idea looking at the steering linkage to the rudder.
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Jan 04, 2012, 04:20 PM
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forgot to say it is a 3 cell. Think nano tech batteries might be a good idea?
and when the boat is running at speed the back end still drags through the water (not much lift).
Jan 04, 2012, 10:10 PM
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Originally Posted by dannyzz
forgot to say it is a 3 cell. Think nano tech batteries might be a good idea?
and when the boat is running at speed the back end still drags through the water (not much lift).
What is the total length?
Jan 04, 2012, 11:08 PM
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Jan 05, 2012, 01:56 AM
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nice boat! just a couple of suggestions and a quick your first picture the space between your drive dog (the nut in front of your prop) is a long distance from the back of the strut. when your boat is at speed the cable will wrap up some but not enough to take up that much space. there should only be about a 3 mm gap. if the space is too big the prop will try to punch the armature of your motor through the motors case and will affect the speed of your boat and the life of your motor severely. you should also install a thrust washer or at a minimum a teflon washer between that nut and the back of the strut. hope this helps, good luck.
Jan 05, 2012, 11:01 PM
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26" is a big outrigger for a 2845 motor, and 2600 mah is very small for a boat this big. IMO it needs a 3650 and a 5000mah pack.

3600kv is on the high side for 3s (45k rpm unloaded).

29mm is also quite a small prop, my 15" hydro runs a 32mm prop and my 29" cat runs a 45mm prop.

I would bet that the prop can't push enough water or provide enough lift, and that would be why it's dragging the tail.
Jan 06, 2012, 01:00 AM
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so should i use a motor like this?
Jan 06, 2012, 08:13 AM
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wparsons's Avatar
You can try some other things before buying a new motor, but it could take a lot of fiddling.

Where's the balance point of it currently?

How warm is the motor/ESC after a run? How about the battery?

I think you need the balance further forward (to about an inch behind the sponson trailing edge), and a bigger prop.

If the motor/ESC/battery temps are already high, your only option for more prop is a bigger motor with a lower kv. The one on hobbyking would be better, but not a guaranteed fix if there are other setup issues.
Jan 06, 2012, 05:38 PM
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the motor gets warmish and the esc stays cool as for the battery it is also slightly warm.
but when it is running at speed it sounds like it might be over revving.
the balance point seems to be where you said.
i have ordered some different props and they should be here soon and i will see how i get on.
Jan 12, 2012, 03:36 AM
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FlyingNiko's Avatar
It is definitely the prop you should take a look at. In Europe we sail these riggers with 36mm - 39mm twoblade props. You could start with the K-series of Graupner and replace it with a metal prop once you are satisfied with the speed and handling. This is a small footage of my rigger, under windy Dutch conditions:

Hydro I Test 28 Dec 2011 (1 min 25 sec)

This is my protoype for Hydro I competition.
Jan 21, 2012, 01:45 AM
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I tried a 34mm turnigy prop ,it went well but at the end of the run 2 min? the motor was on the very edge of hot to touch. So increasing the size might be a bad idea and i am guessing it went 50kph at top speed. (forgot to take my camera) I will go for a run in the next few days and see how i go.
Jan 21, 2012, 07:02 AM
Boaters are nice people.
Hi Danny,

As others already mentioned, your set-up is on the edge;
The motor can handle 3S, turning a 36 mm Graupner K-series prop (2318.36), but the boat has to be set-up correctly to enable the motor to rev out, if it drags the tail, thing will get hot, as you've noticed.

You need to get the CoG further forward and, if you want to stay with this motor, consider adding rear sponsons to lift the rear end.

Regards, Jan.
Feb 03, 2012, 12:17 AM
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RC brushless outrigger (1 min 17 sec)

got it going better i put in a 3300mah nanotech 45c 3s battery.
i went back to the 29mm prop which seems to work best.
so would making the motor bigger be a good idea?

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