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Old Aug 03, 2010, 10:26 AM
Im flying... don't talk!
helisfreak's Avatar
Arizona, USA
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Old tunnel hull 7.5kb to Electric Conversion

I bought a mini cat cheap, had lot of fun. So my friend gave me his antique Hull that had the stock 7.5KB motor to convert it to electric.

I do not know much about boat, but this is what I got so far, hopefully it will work. I am praying that water will not hit the motor... Also I am planning to plant the servo on the top and water seal it.

I removed the electronic tray so that more battery size and flexibility on moving it around for the CG... (BTW anyone know where the CG need to be?)


The motor is 585kv, planning to run it on 12s5000 (not sure if this will work)? Oh, the boat is about 32inches long.

Any inputs would be greatly appreciated.
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Old Aug 03, 2010, 10:35 AM
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Miami, Fl
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i say make like a water proof cover for the motor like fiberglass (continue it from the hull to make it one piece) this way very minimal water will get to the engine
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Old Aug 03, 2010, 11:28 AM
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Staffs UK
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Iv seen a few outrunners on outboards with no probs from water,im also planning using outrunners on outboards on another build im about to start.
Nice looking tunnel by the way very retro
good luck with the build and get some vids when it hits the water
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Old Aug 03, 2010, 11:41 AM
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helisfreak's Avatar
Arizona, USA
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hey F1,

I saw your build thread, awesome, this is no where near it... Anyway, if it run good, I might be looking forward to make a shell for it, I saw you make a shell for your servo, can you tell me how you made it and out of what materials?
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Old Aug 03, 2010, 11:49 AM
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Quote:
Originally Posted by helisfreak View Post
hey F1,

I saw your build thread, awesome, this is no where near it... Anyway, if it run good, I might be looking forward to make a shell for it, I saw you make a shell for your servo, can you tell me how you made it and out of what materials?
Cheers bud
just used balsa cut each individual piece and glued it together
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Old Aug 03, 2010, 11:51 AM
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Vancouver, Canada
Joined May 2007
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32inch on 12S?? wow... that is heavy for a small hull.
Maybe get a 6s on 1600KV. Save a lot of battery weight and drop down ESC cost from $300-$500 to a more manageable range of $100.
Maybe even a large motor with 1100KV and a large prop.
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Old Aug 03, 2010, 11:56 AM
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United States, CA, Santa Barbara
Joined Jun 2009
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Looks cool.

Don't know where your going to get an esc to handle 12 cells, or how your going to fit all the batteries in the hull...

Get your self a traxxas waterproof servo and your won't have to creat a waterproof housing for it. Just make a small waterproof box under the servo to hold the Rx and the esc if it isn't WP. That leaves you with plenty of room to fit batteries up front.

Does it have a under hull turn fin? Usually on tunnels these are placed near the center of gravity.
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Old Aug 03, 2010, 12:02 PM
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helisfreak's Avatar
Arizona, USA
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Quote:
Originally Posted by Vasy View Post
32inch on 12S?? wow... that is heavy for a small hull.
Maybe get a 6s on 1600KV. Save a lot of battery weight and drop down ESC cost from $300-$500 to a more manageable range of $100.
Maybe even a large motor with 1100KV and a large prop.
Really? I saw people run 6s 8000 or more 200+amps esc.. that would be the same weight.... I fly mostly helicopters and I am a High Voltage fan, the low voltage and high amp draw isn't my ideal. With this, I am hopping to use my Heli esc, which is rated 12s 100amps (I am not sure whether is need water cool or not.. .probably yes)

Anyhow, I do have 12s3300 and 12s2500, so if the 5000 turn out to be to heavy, I will use those. But I am not skipping down on the voltage...

Boat weight about 14lbs RTR.


Marc:

All my heli are flown on 12s, all my esc are 12s (they are not water cooled though, I hope I can buy the water cool heat sink for it). No worry about battery compartment, the entire boat is hollow inside, you can fit 12s10000 if you wanted to. The battery can be push all the way back until it hit the rear wall as well..

It does have a fin on the bottom, thanks for the tips.
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Old Aug 03, 2010, 12:14 PM
nick 30
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from my understanding (been doing boats for a while now) 12s + 100a esc in a boat = boooooom, gurgle gurgle, all boats electronics need to be waterproof and cooled

you can use high volt batts with low volt motors, the high volt batts and low kv motors will run cooler and amp draw will be low

this need's to be pointed out so please don't take offence

boats and heli's are completely different, some knowledge from heli's can be applied to boats, most boats are direct drive so real need for gearing

12s is more like SAW (straight away or drag boat racing) territory
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Old Aug 03, 2010, 12:35 PM
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helisfreak's Avatar
Arizona, USA
Joined Mar 2004
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Well, no offense at all.

But let me get this right, the motor is a 585kv x 50volt = 29250rpm. You're saying this will not work and it will pull more than 100amps continuous? I use this motor and esc combo on my 90 size helicopter, weight 12lbs, outputting 4500watts.

The esc will sit inside the boat, so it's water proof, as for the water cool, I think I will buy the add on water cool heat sink for it.

Again, I'm noob at boat, so looking for tips and advices. But it should be fun to see what this can do...
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Old Aug 03, 2010, 12:36 PM
I feel the need for speed!
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Not in complete agreement Nick.........a 585kv will run cool as can be........if the weight isnt an issue 12s should work if that is what he has available. He'll be in the "racing boat" rpm area of around 28,000....................

Heli, check out the turnigy 80a HV esc that handles 12s.............its at hobbycity
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Old Aug 03, 2010, 02:59 PM
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BTW, the stock servo on it is dead. How many OZ torque do you guys think it will need for this boat?
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Old Aug 03, 2010, 03:01 PM
nick 30
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i would go with a metal geared standard servo and use the aquacraft motor, esc etc
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Old Aug 03, 2010, 03:01 PM
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Canada, ON, Markham
Joined Aug 2008
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One thing to keep in mind is how much of a surge you could get with a boat. If you jump out of the water and unload the motor, there's a big spike in current when it lands again.
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Old Aug 03, 2010, 05:43 PM
I feel the need for speed!
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Southern U.S.
Joined Jun 2008
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This is what i run, even in boats up to 40", high torque and waterproof.............affordable too

http://www3.towerhobbies.com/cgi-bin...?&I=LXTKL0&P=7

Here's the link to the 80a 12s watercooled esc for $68 bucks

http://www.hobbycity.com/hobbyking/s...hless_Boat_ESC
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