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Unofficial "NQD" Tear into Jetboat Thread

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Old 09-02-2012, 05:52 AM
  #2951
Ratrunner
 
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the ESC wont  "suck water"  it has to be forced through by the action of the motor.

on a regular boat, the water pick up is on the rear of the boat, and water is forced though as the boat moves forward.
on the jet boat, the water inlet is on the rear of the jet unit. as water is expelled from the jet unit, some is diverted through the cooling system.

there are plenty of pictures on this thread of the water pick up on the jet unit.

Jason.

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Old 09-02-2012, 05:54 AM
  #2952
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double post...

Jason.
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Old 09-02-2012, 06:18 AM
  #2953
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I see.. if ESC do not have the capability to suck water...is there any difference if connect water in to Motor first then ESC?

for the ESC, I suppose can connect to either tube as there is no indication on ESC?

Thanks
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Old 09-02-2012, 06:27 AM
  #2954
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it doesn't matter which way you connect things with the water cooling system.

you could connect the motor first or the esc. and you are correct, there's no In or out on the ESC.

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Old 09-02-2012, 06:36 AM
  #2955
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It is better to connect the water to the esc first then to the motor. The esc is generally more important and can't stand as much heat as the motor can.
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Old 09-02-2012, 11:21 PM
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Hi all, I am curious to know a couple of things and any info greatly appreciated!

Firstly, my boat seems to "skip" or "bounce" on the water a lot. Im only running it in my calm water dam and its continually losing prime just going over my own wake to the point of being a real pain in the ar*e and not much fun to play with. Im wondering if anyone has tried some ballast to keep the boat downin the water and stop the "skipping"? Also has anyone found an ideal cog? I've tried moving the battery around a bit and it seems to run best where I have it (just fwd of the motor, transverse to it) I am running with a ride plate and it makes no difference whether to run with an intake grill or not. Damned annoying! Prop shaft is well greased (tho only with an auto high temp bearing grease) which tends to make a hell of a mess when the water starts running up the shaft into the boat. Im running a3500kv outrunner, mostly at full throttle flying around the dam on 3s 2200mah nanotech's

Which leads me to my next question......has anyone 100% (ish)sealed their propshaft, whether by modding it, changing shaft, fit bearings/seals etc etc? Cause it really pee's me off finding water in the boat (and shaft grease) after a run. Maybe using a proper marine grease will help?

Would really like to get this boat running well, fun to play with, watertight (ish), and reliable so I can get onto my next project content in the knowledge if I want to hit any rapids with the NQD I will enjoy it! At the moment I wouldnt bother with rapids as it loses prime on its own wake!

Thanks for any wisdom!
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Old 09-03-2012, 02:23 AM
  #2957
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cant help with the other problems, but how ,much water are you getting inside after a run ?

i get 4-5 minutes per battery pack, and there is always a little water inside.
maybe 30-50 ml. not heaps. so im not too bothered by it.

i just tip it all out after each battery change.

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Old 09-03-2012, 02:57 AM
  #2958
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Yeah, much the same Jason, it just annoys me as I reckonthe H2o belongs on the outside! I have a couple of small bits of kitchen sponge to soak it up

The "bouncing & skipping" isnt porpoising, the boat gets up on plane nicely, just bounces a lot when its up there, would be darn uncomfortable to ride in!

cheers
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Old 09-03-2012, 07:56 AM
  #2959
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Quote:
ORIGINAL: swervyn

Hi all, I am curious to know a couple of things and any info greatly appreciated!

Firstly, my boat seems to ''skip'' or ''bounce'' on the water a lot. Im only running it in my calm water dam and its continually losing prime just going over my own wake to the point of being a real pain in the ar*e and not much fun to play with. Im wondering if anyone has tried some ballast to keep the boat down in the water and stop the ''skipping''? Also has anyone found an ideal cog? I've tried moving the battery around a bit and it seems to run best where I have it (just fwd of the motor, transverse to it) I am running with a ride plate and it makes no difference whether to run with an intake grill or not. Damned annoying! Prop shaft is well greased (tho only with an auto high temp bearing grease) which tends to make a hell of a mess when the water starts running up the shaft into the boat. Im running a 3500kv outrunner, mostly at full throttle flying around the dam on 3s 2200mah nanotech's

Which leads me to my next question......has anyone 100% (ish) sealed their propshaft, whether by modding it, changing shaft, fit bearings/seals etc etc? Cause it really pee's me off finding water in the boat (and shaft grease) after a run. Maybe using a proper marine grease will help?

Would really like to get this boat running well, fun to play with, watertight (ish), and reliable so I can get onto my next project content in the knowledge if I want to hit any rapids with the NQD I will enjoy it! At the moment I wouldnt bother with rapids as it loses prime on its own wake!

Thanks for any wisdom!
I wonder if your ride plate isn't causing it to skip or bounce. I have none on mine and experience no skip or bounce. I also have an intake screen as opposed to a grill on mine which seems to help with aeration. The only time that I've had problems is when the hole egged from wear in the housing. I replaced this with a bushing (brass tube) and added a bearing instead of the rubber seal. I do get a little water in but I can jump completely out of the water and instantly picks up prime when it comes back into the water surface. Your battery placement is ideal from what I and others have found. Hope this helps some.
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Old 09-04-2012, 10:55 AM
  #2960
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Here is my boat build. It's been through a couple ESCs, several steering nozzles, 3 servos, etc..

I'm using a 3700kv boat motor http://www.hobbyking.com/hobbyking/s..._Inrunner.html
50a birdie ESC
cheap orange servo from hobbyking stuck in a balloon and mounted with a custom steel plate

Overall this boat performs great, a different motor setup would probably gain some top end speed on smooth water. I use it mainly for river and creek runs so the tourqy 3700 motor is great for me. I've been through a lot of trial and error and can probably answer some questions if anyone has any.

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Old 09-04-2012, 12:16 PM
  #2961
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Nice boat there Murmuzy I like that servo mount, good work!
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Old 09-04-2012, 12:41 PM
  #2962
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Nice pictures, thanks.
I love many pictures in a thread. You know, "a picture is worth a thousand words"
I always save my pictures on a storage drive under category folders, then model name folders. For example; the category folder would be RC Boats, the model folder would be NQD Jet Boat.
They are quick and easy to find and I never mind reposting them.
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Old 09-04-2012, 07:37 PM
  #2963
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well i last posted saying my coupler wasn't long enough for my setup, but i found something laying around that worked perfect just had to drill and tap for the set screws. I have yet to get any pictures of it will do soon though, but on the other hand i do have a video let me know what you guys think.

Watch me

and me

first run i was only getting half of this speed and the next day my receiver was shot wouldn't work the motor, put in another receiver i had laying around now i dont have proportional throttle has half or full thinking it may be the receiver again, as the old one went slow but at least had throttle control.

Let me know what you think and thanks for all the help i found here in the thread.

Joe
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Old 09-04-2012, 10:51 PM
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Thanks for the info all
Just scrolling/searching back through the thread for the 14th million time looking for clues and came across wparsons post #1441 & 1449 on page 58 and he describes exactly the same issues I am having. Cant locate any definitive answer tho lol. Losing prime on small ripples, having to come to a complete stop to re-prime etc.
I too drilled out the shaft tube and fitted a 3mm brass tube liner. Due to a bent prop shaft the wobble caused the liner to come loose & reamed the hole out in the housing. So I drilled it out a bit more & fitted a 5mm O/D brass tube and used the 3mm tube inside that which worked quite well, (apart from water entering)BUT.....got me thinking that because I ran the brass tube all the way to the impeller that it has now restricted the water flow around where the impeller (2.3mm) shaft would normally be? Thus reducing the impellers ability to "suck" the water? (probably clutching at straws but this WILL NOT beat me!)
Shortened & squared off the back of the ride plate much like mumurzy's (thanks) as was a bit pointy before making it chinewalk also. Seemed to reduce the skipping slightly on the last run.(thanks damfurst)
Going to try the shaft liner again but this time shape it to the inside of the intake well instead of taking it back to the impeller and see if that helps.
Anyway the boat is in pieces again for the 764th time [:@]
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Old 09-06-2012, 12:54 AM
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didnt help grrr
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Old 09-06-2012, 06:38 AM
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Sounds like you have a couple of different problems. The shaft bore tolerance seems to be critical in this jet drive and wear can lead to air entry causing loss of prime, as well as water entry when setting still. This is why it is so important to keep the shaft lubed with a good waterproof marine grease. Though some have relined with success, at this point I would buy another pump, keep the shaft greased and be done with it. Your motor seems too high a KV for 3S. Go with something around 3000kv and it should settle down without much (if any) loss in speed. Something I found out a while back was this boat goes through stages with increased speed. Given more speed, it porpoises, a little more speed and it settles down. You're in-between with your setup is all. Good luck!
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Old 09-07-2012, 02:52 AM
  #2967
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Need help ...
My 2nd run using Turnigy 60A ESC, Leopard 4450kv Motor n 40~80C 2S Lipo battery..
Cooling tube water flow is normal but just 1~2 mins run, there is smoke n the motor ABC wire almost turn into ashes !!!
Any advise what when wrong ?

Thanks
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Old 09-07-2012, 03:59 AM
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Did you check to make sure there was no binding in the drive train? any resistance could cause problems.
Are you running 4s or 3s? If you are running 4s, make sure your motor is rated for that amount of voltage.
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Old 09-07-2012, 04:49 AM
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did not notice any resistence and I'm using a 2S 40~80C Lipo battery.
very puzzled why the wire could burn.
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Old 09-07-2012, 05:21 AM
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Quote:
ORIGINAL: spektrumFlux

did not notice any resistence and I'm using a 2S 40~80C Lipo battery.
very puzzled why the wire could burn.
Turn the coupling with your finger, it should be smooth with no resistance for a full turn. There are several things that can hang up - the loading ramp fit (if you removed the jet drive), the shaft could have come forward when you attached the coupling, allowing the shaft to come out of the rear bushing, a piece of plastic caused by the injection moulding process that wasn't fully removed, etc. One other thing is too small or inadequate connectors can cause high heat. And it could have been a bad motor - it happens now and then. Do you have any pics - they might explain more.
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Old 09-07-2012, 06:13 PM
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have tried to rotate the coupling, seem ok.

attached below are the burned wiring pictures.
http://www.freeimagehosting.net/nw6xg
http://www.freeimagehosting.net/aer5k
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Old 09-08-2012, 12:27 PM
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Fried to a crisp, aren't they? Well, there's no tellin'. How did it run?! Maybe you had an obstruction in the intake (leaves, algae, etc.) and didn't know it, so kept running it hard to keep up. That combo was right in the sweet range (4450kv on 2S) for this pump.
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Old 09-08-2012, 01:49 PM
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Started a new build of a tear into this week. Doing it for the son of a friend of mine. Thought I'd share as progress is made some of the pics. So far I've gutted it, installed flotation foam (2part stuff) in bow, done the bearing mod to front of drive, greased impeller shaft with Gorilla Snawt, and done the water pickup in the stator.

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Old 09-08-2012, 08:21 PM
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It's a newly modified boat and into the 2nd run.
Nothing stuck beneath and only run for 1~2 mins, followed by smoke and saw motor wiring almost turning into ashes.
Too much current supply to motor which burned the wiring???

Thanks.
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Old 09-08-2012, 08:47 PM
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How did it run (when you first ran it)?
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