Unofficial NQD Tear Into Jet Boat Mod Thread - Page 54 - RC Groups
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Nov 28, 2012, 04:15 PM
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Well, the tolerences aint the best on these, werent ment to be, either, I agree with Fire, my batt is in the same location, side to side..

Ant, you could of course cut down the impeller to match, but, losing blade surface aint gonna help nothin..your boat doesnt sound bad, seems to have good speed, but, remember, it cant go forward when its suckin air..I got my best results by taking the time to tune the trim well, I had to add tabs to get it where I wanted it..made them from stainless stock, a pain, but, better than aluminum for ridgidity..if they get hung up rock crawlin, I dunno..

Last edited by chidago; Nov 28, 2012 at 04:22 PM.
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Nov 28, 2012, 06:20 PM
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madbugger's Avatar
Originally Posted by chidago
..if they get hung up rock crawlin, I dunno.
If I could get it for $72 like you, I might get another. Makes a difference being almost half as near to Oz as me, don't it. And the red hull is back, is it? It was a choice of black, white or clear when I got mine.

Anyway, to the point. Your trim tabs are longer than I at first thought but still no longer than my ride plate, and that doesn't present any problems when rock climbing. So on that basis I reckon Antslake could follow your example without fear.
Nov 28, 2012, 07:45 PM
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Well, Mad, I'm hopin they dont, cant see any good reason they would, but, if I wasnt trying to tune for speed and stability, just use it as a rock climber, it wouldnt need em..

Yeah, seems post to you from over there is horrible..shame too, free trade is how the world makes a living.
Nov 29, 2012, 03:19 AM
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Scratch built 30 mm Impeller Nozzel Area Reduction ratio 2.8:1

Scratch built 30 mm Impeller Nozzel Area Reduction ratio 2.8:1 maintained the same are reduction ratio as the NQD jet and turned down a 35 mm prop for an impeller.

Any thoughts recommendations on RPM I should spin it at?

Its metal loaded car filler and one layer of woven roving glass fiber. have a bearing mounted in a brass stator which I will locate with. the wear ring will be part of the nozzel housing, so it will be a duct and pump design like some jet skis

Last edited by nickatredbox; Nov 29, 2012 at 04:44 AM.
Nov 29, 2012, 12:05 PM
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Nick, what are you trying to accomplish? a no pitch, 3 vane stator, wont work, nor will a 2 blade impeller..pattern after a real jet, not the cheap hobby one, gotta have pitch in the stator, and look for a 4 blade prop to fit, at the least..these nqd, graupner pumps are really nothing but a glorified cort nozzle with a look a like a jet housing..

When I visited berkley jet, saw many, many jet designs, 2 stage is best, really cant do that in our scale..1/4 scale, like the jettec pump, yes, and ramp angle, etc, is so important.
Nov 29, 2012, 01:05 PM
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I think you are on the right track with the multi blade impeller I have a heavy model with twin NQD's The 4 blade impeller was much better in the bath for static thrust, than the NQD's stock 2 blade impeller on the 3Kg boat. That said both 2 and 4 blade worked pretty well. I copied the ramp angle from the NQD design. The NQD has no pitch on its stator either, I assume the edges of the stator should be curved apposing impeller pitch.

I just like tinkering to see what happens you can learn lots and its also fun, and my design is practically free to build. The NQD jet works quite well even when taken way past its design specification with a brushless. I want to see in practice what sort of thrust level and speed difference it makes to my yellow boat design. As you say they are toys really a prop in a pipe with a nozzel. I have maintained the nozzel area ratio of 2.8:1 like the NQD also as a start point

I used to be the systems engineer in a wind tunnel, so I have a working grasp of fluid dynamics and understand nothing is simple when it come to this sort of design. With the 2 blade impellers in the NQD drives you get good motor loading I have run the NQD up to 350 Watts without cavitation in the bath with a 4200kv heli motor

The Project 31 in action
Scale Project 31" 08-09-2012 On the pond in Heathcote Valley (3 min 24 sec)
Last edited by nickatredbox; Nov 29, 2012 at 01:29 PM.
Nov 29, 2012, 01:45 PM
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I have seen jets with nozzels with a bottle shape on fast boats here in Christchurch New Zealand home of Hamilton jet who I think invented the water jet concept.the NQD has a cone section. I suspect the contraction ratio is very important but also avoid in choking the flow given water can be considered un-compressible. These bottle shaped nozzels have tiny outlets which must give massive outlet velocity
Nov 29, 2012, 02:11 PM
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Nick, my formal is a masters in mechanical engineering, so, some hydro was part of it, but, my working knowledge came from being financially associated with berkeley jet. and having, and racing full size jets thruout the 80's, but, real things dont always scale down, so its a crap shoot..

The nqd, is a splash from the graupner, almost exact, and the graupner aint no big feat, for $50, you aint getting big engineering effort, they work in a hobby arena, thats it..

The jettec, which replaced, and went past, the old swashdrive pump, is a nice piece, much bigger, tho, and almost $900....I mod just to try and put some applicable practice to it.. = I'm bored..

If I were to try and build a pump, it would be a big flat pad aft hull, tapered slight angle flow path, in the scale here, 1/10th, single stage, 4 blade, axial stator, tight clearance, adjustable cone, huge power, 35k rpm..
Last edited by chidago; Nov 29, 2012 at 02:17 PM.
Nov 29, 2012, 02:39 PM
Kamikaze pilot
Hi guys! Im back with a new hulldesign. Now more like a real jet sprint. This one im maby gonna try to flatten in Rhino and laser cut the parts and make the plug by hand because the milling machine i got at hand is not working for the moment. Still got the deck part to do though. Any thoughts?
Nov 29, 2012, 02:44 PM
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OOOOH... I'm liking that one..good work, whats the length and width??? v is shallow enough, pad is GREAT..could use a little more defined strakes,a second one for sure, but, I would buy one NOW.
Nov 29, 2012, 03:02 PM
Kamikaze pilot
Hehe glad you like it
This one is same as the others i made, only differs in hight.
L:430mm W:180mm H:48mm

Will keep it smooth without strakes on the 3D model and put it on the plug by hand later on Maby made just by a thin brass lath so it makes a charp strake when vacuum molded, then its possible to fill it with epoxy from the inside to strengthen it.
Nov 29, 2012, 04:33 PM
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A 500 to 600 mm would make a MUCH more user friendly boat, if you ever rode a PWC in rough water, you will know what I mean..length keeps it hooked, will not only make a rock crawler, but, will make it more lake friendly..

the best jets would be the KMB, but, the stern of the boat has to be tall enough, and gunwale height, to accomodate the install..and it should be tall enough to accomodate KMB'S 40 mm jet too, for the power idiots like me..
Nov 29, 2012, 06:30 PM
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Nick, we used to play with nozzle reducers all the time, the ratio is important, changing the full size nozzle by .030 made a difference..and on the rc stuff, it would take a flow bench to set it right..
Last edited by chidago; Nov 29, 2012 at 06:48 PM.
Nov 30, 2012, 08:31 AM
Kamikaze pilot
Originally Posted by chidago
A 500 to 600 mm would make a MUCH more user friendly boat, if you ever rode a PWC in rough water, you will know what I mean..length keeps it hooked, will not only make a rock crawler, but, will make it more lake friendly..
Yeah it would. Could scale it up to fit a 40mm jet as a future version but for now im gonna try finnish this a bit more handy sized boat
Nov 30, 2012, 09:16 AM
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I'll be waiting for updates!

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