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Thread: brushless mini cat?????????????help!!!!!!!!!!!!!!!!!!

  1. #1
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    Question brushless mini cat?????????????help!!!!!!!!!!!!!!!!!!

    i have put a 370s 4400kv brush-less motor and a water cooled 20 amp esc with a 3s lipo in a mini c hull along with a spectrum receiver and new servo. The running gear is all the same except for the prop shaft witch is now threaded to take different props. I have tried three different props all about the same as the stock mini rio prop with different pitches i have even filed one down to half the original diameter and tried it all with the same result. the boat just flips no mater what. even when i try to be gentle with the throttle it just flips before it even gets on plane. with the moded prop i could just get it on plane but it still wanted to lean hard right and the cavitation was horrible. Anny prop or drive advice would be greatly appreciated.
    Thanks

  2. #2
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    Drop down to a 2s pack. Thats almost 50,000 rpm on 3s!!! Too much.

  3. #3
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    Volts X Kv = max RPM

    Max RPM should be 25-35k

    You can use a piece of #128 K&S brass as a shim and use the Venom 32mm props. But with 4400kv, wow, 35000 RPM that's about 55mph or more in that little hull!

    I did a similar build on 2s with 2900kv motors and 32mm props. No room for GPS, but it was wicked fast!
    FighterCatRacing Team CHING BLING - Ching Bling. Brilliant, Advanced Sparkle for your hull.

  4. #4
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    thanks for the answers, but my problem is it wont even get on plane without flipping.i have tried just slowly working it up but it still flips. The one time i did just hit it it flew out of the water about 4 feet spinning around, busted both universals, and striped the servo gears. I don't have any 2s laying around so i will just bring my throttle rate way down on the tx for now. Also if i put a regular mini strut and rudder on like diegoboy did on his, will this help at all with the rolling problem?
    Last edited by reelredneck; 10-10-2010 at 01:47 PM.

  5. #5
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    Where is the COG? It should be about 27-30%

    But , if the power delivery isn't smooth, it's going to over power that little hull and flip. Should be running at about half that RPM. JMO
    FighterCatRacing Team CHING BLING - Ching Bling. Brilliant, Advanced Sparkle for your hull.

  6. #6
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    my cog is 5 inches forward from the transom on the 14 in hull and the lipo is on the far left side of the hull to compensate.

  7. #7
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    Quote Originally Posted by reelredneck View Post
    my cog is 5 inches forward from the transom on the 14 in hull and the lipo is on the far left side of the hull to compensate.
    Might try moving it back to 4".

    You might try taking a vid of the behavior, it will tell us more than a description.
    FighterCatRacing Team CHING BLING - Ching Bling. Brilliant, Advanced Sparkle for your hull.

  8. #8
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    OK thanks I'll try moving it back a bit and I'm headed to the lake right now. I'll try to get a good video.

  9. #9
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    Thank you, fightercat you have been a great help. I put a new octura red 30 mm prop on it and took my throttle limit down to 60% with 25% expo. I took the cog back as far as i could to 4.5 in from the transom and it runs much better.
    At 60% throttle(max for now ) it still tilts right and wanders to the right but it is still bearable i just have to do a little compensating. The only problem is it is still plowing. The hull is running way to wet(3/4 of the hull in the water).I am going to ad a few nylon spacers to the prop shaft between the universal and the out drive and ad a shim between the hull and the drive to angle the prop up a bit more.Hopefully this will get it to ride right. If not ill try to ad some weight in the transom area.

  10. #10
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    Move the COG back to 4" and it should help stop the plowing.

    Cool, glad it helped. =)
    FighterCatRacing Team CHING BLING - Ching Bling. Brilliant, Advanced Sparkle for your hull.

  11. #11
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    Be careful. Running that esc at 60% throttle is transferring that other 40% into heat in the speed control. It could cause the esc to burn up.

  12. #12
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    I'm running a mongoose 8.5 6000kv sensored with a 40mm prop. On 2s it won't flip on 3 if I'm gentle out of the whole its pretty good but way too much power for that little boat

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