Unofficial NQD Tear Into Jet Boat Mod Thread - Page 66 - RC Groups
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Dec 20, 2012, 03:33 PM
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madbugger's Avatar
Originally Posted by Tiernan85
the Gopro gives a bit of a false sense of speed.
Gopro or not, your boat looks fine. I've got many streams like the one at beginning of the vid, but few bits of open water like the dock area featured later. Then again, nowhere's perfect. For example, I envy Chi his nearby lake/pond (call it what you like), but he is bemoaning the lack of local streams. Reminds me of a joke, but this is hardly the place for it. In fact no thread is the place for it, unfortunately
Last edited by madbugger; Dec 20, 2012 at 05:31 PM.
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Dec 20, 2012, 05:55 PM
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I'm to ashamed and I'm sure its out of policy for YouTube its a bit like catching your reflection when you don't expect to only worse
Dec 20, 2012, 07:16 PM
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T, Steve is gonna be doing a larger boat, about the length of the kmb hull, but, it the plastic that works for crawlin, with the kmb jet, it will do double duty, which is the BIG answer...
Dec 20, 2012, 07:59 PM
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Tiernan85's Avatar
Yea just had a quick word with him about them. Need to save a few pennies, now is not the greatest time for that!
Dec 20, 2012, 09:21 PM
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Good..BUT, you'll get 2 boats in one, actually a better value, cause the big one will be good for crawlin too..

Dec 21, 2012, 06:17 AM
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Tiernan85's Avatar
Very true
Dec 21, 2012, 10:51 AM
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Yup..and so much nicer to have room inside to rig it YOUR way..batts on the side, for one thing, gets the CG where you want it..
Dec 22, 2012, 03:17 AM
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nickatredbox's Avatar

Yellow Boat 3 Power Tests with Turnigy 500W H450 2100kv

Scratch Built hull, water jet and cooling pump made from Coroplast and junk Yellow Boat 3 Power Test (0 min 45 sec)

Scratch Built hull, water jet and cooling pump made from Coroplast and junk Yellow Boat 3 Power Test

Boat build log here
Jet pump build here
Cooling pump testing here

Test results
Dynamic loses
29.5 Watts
2.3 Amps

Peak power
532 Watts
47.5 Amps on a 3C

Home brew cooling small centrifugal pump made from junk, with a scoop on the hull. The pump is mounted directly above the scoop and primes its self with the standard trim at rest.

I also found that if I re-introduce the out let from the cooling circuit into the jet ramp, there is a tendency for the water to be sucked through by the main drive when the throttle is up thus improving cooling flow at high loads, a win win. I wanted a circulation pump because taking a tap from the pressure side of the jet unit uses some thrust and is only available at speed, with low throttle or stopped there is no flow and this I thought would cause over heating when stopping after a long high power burst.
Last edited by nickatredbox; Dec 22, 2012 at 03:48 AM.
Dec 22, 2012, 10:16 AM
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Sic improvements

Last edited by Mikedown; Dec 22, 2012 at 04:23 PM.
Dec 22, 2012, 12:37 PM
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madbugger's Avatar
Originally Posted by Mikedown
Sic improvements
Not quite sure where you are going with this.
With the Sic flex shaft and indeed most proprietary flex shafts there is a small section of solid shaft from before the prop mounting, and which (in the case of things like the Sic shaft) extends into the stator bearing behind the prop. The union between flex and solid shaft is normally by industrial cyano, tig welding, or other bomb-proof means of coupling. And on top of that, assuming your flex cable is wound the right way, the drag of the prop will tend to keep the flex shaft from unfurling.

If this were not the case every hydro, FSRV, competition mono, or other flex-shaft boat (of which there are many hundreds of thousands throughout the world) would be in trouble. That said, I am not a GURU as you put it. And being as I am (in the words of Winnie the Pooh) "a bear of very little brain" I may have completely misunderstood your problem. In which case, state it more clearly and perhaps the GURUS will wade in to help.

As far as the greasing is concerned, use a good marine grease which will last. If you have to strip the nozzle every so often to re-grease the shaft, it means you're getting a lot of water-time and therefore it's a small price to pay. Will still only take a few minutes. But then, one man's PITA is another man's 'routine maintenance'.
Last edited by madbugger; Dec 22, 2012 at 01:35 PM.
Dec 22, 2012, 01:29 PM
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jet mod

Last edited by Mikedown; Dec 22, 2012 at 04:46 PM.
Dec 22, 2012, 02:12 PM
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Mad is completely correct, in fact, flex is the only thing that can be used RELIABLY in high output configs..solid shafts of any length require way to much support for high torque applications..

On the gas boats, we use either 6.35mm, or,7.93mm cable, but, if you notice the gap between my prop dog and the drive unit, which is about 7mm, is for the rap up of the cable under acceleration, I am putting 9 hp to it, it will tighten itself enough without the gap to blow the prop and dog off, or, break the cable..

But, knowing to do that, you have a trouble free running gear..I have shafts 10-12 years old still running fine..
Dec 22, 2012, 02:47 PM
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madbugger's Avatar
Originally Posted by chidago
Mad is completely correct.
Well, there has to be one time in everyone's life. To be completely correct, I mean.

But more to the point, thank you Chi for ramming my point home. You are more of a marine specialist than I could ever become. If you say it, it must be true. And you provided photo evidence Mikedown, take notice.
Last edited by madbugger; Dec 22, 2012 at 03:23 PM.
Dec 22, 2012, 03:08 PM
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madbugger's Avatar
or not
Last edited by madbugger; Dec 22, 2012 at 03:22 PM.
Dec 22, 2012, 04:23 PM
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Jet boat

merry x-mas and a happy new year.
Last edited by Mikedown; Dec 22, 2012 at 11:13 PM.

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