DRAGONFIRE81M

if your talking about the nockoff it was a align like you find in t-rex's heli and i got it and a 30a esc for $30 on ebay oh and it was a 3500kv you could also go with a ammo
http://www3.towerhobbies.com/cgi-bin...&I=LXLWY5&P=SM

DRAGONFIRE81M

Quicksilver

Oh yeah the graupner provides more than adequate cooling pressure. You have to tap the "bowl" yourself, but it's easy and Works so well, that I had to put clamps on all my cooling lines or else it sprayed water everywhere inside. I too, found the Kehrer drive almost impossible to tap a pick up. There's just no nice place to put it.

The nozzle modification I made on the Kehrer drive, was supposed to just compress the water, but did act more like trim. It worked, but would have worked better with a 3 channel radio.

pics
my graupner water pickup

my variable nozzle on the kehrer.

and lastly a close up shot of the graupner pick up. Sorry this post got all wacky, I'm having trouble finding pics.

5150Cat

Quicksilver,
What kind of motor mount do you use on the Graupner jet?

I think I'm sticking with the Graupner drives for price and ease. As much as I'd like to play around with a bigger jet like the Kehrer bigger bore jets.....For now I'll stick with the Graupners.

Probably order one Friday and get the hull coming as well.

I'll keep you guys posted with pics.

Thanks again for all the help!

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DRAGONFIRE81M

just to let you know grumpner has a big drive . i will have to look to make sure but i thank its a 40mm the gr2340

5150Cat

Dragon-
I have seen that big drive that Graupner has.....I think I'd have to switch up hulls if I did that. Might be a little long for the Aquajet.....just for ease of install of the jet is the main reason I'm sticking with that hull. Seems to have a pretty shallow V and from the builds I've seen on here it runs pretty sweet.

But I might have to look at that bigger drive......just thinking the length would be to much if I recall. Good call on the 40mm though.

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Quicksilver

I'm using the OSE DR Motor Mount.

DRAGONFIRE81M

i have seen it in a nitro vee and yes it just huge . i know qiuck know the one im talking about

Quicksilver

yeah I do, that boat never did run, or at least the builder wasnt happy enough to show us how it ran. I wasnt in complete agreement with how he installed it.

5150Cat

So you guys think the 40mm is to big to fit in the Aquajet?

Going to look a little closer at the jet length vs the hull length and see if it would be doable.....thinking it would be to long. Probably put the motor way to far forward and throw off the CG of the hull I'm guessing.

The only other problem I could see would be the intake would be to far forward. Seems the smaller jet that you guys have used previous seems to fit perfect on there. But dang it's close as I look at it. And it's only 4" longer. Just hard to tell. Guess I should order the hull and then measure and figure from there. I think it would be worth it for that extra punch and bigger outlet on the jet.

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DRAGONFIRE81M

here you go man . thought quick would have bet me to this but here is the build on the nitro vee with that 40mm drive and the nitro vee comes in at 31" i thank the aquajet is only 27 but i could be wrong http://www.rcuniverse.com/forum/m_46...tm.htm#4671280

Quicksilver

thanks for the link I was too lazy for some reason. The first pic of the thread says it all. It's huge! If the drive shaft was cut down about 3" and the outlet had the normal steering nozzle and not that scale one, it might not look ridiculous. This being said, having personally helped vdub with his aqua jet-jet, I dont think that thing will fit in there. I'd love to see this drive run, but I dont want to see you frustrated either. The reason this drive doesnt seem to fit with the other drives, is mainly because it's meant for large scale motor yachts with lots of room inside. Whatever you do, please dont install it like that

5150Cat

Thanks guys. I'm seeing what you are saying. That thing is freakin huge! Why the hell did they put a 14" shaft on that thing? Dang! That's nuts. I'm with you Quicksilver that if it had a cut down shaft and different nozzle on it that it would look better and not so freakin huge.

I think I'll just stick with the smaller one.(not the mini) I'm just going for max hp's but realize that the boat will only be able to handle so much anyway. And from the vids I've seen of QSilvers and some of the Aquajets the smaller jet will be just fine I'm sure. And with the watercooled motor, 90amp esc watercooled jeti and some lipos I should be able to play with the power options a little also.

I do have a buddy who is a car modeller down here. He's just getting into doing injection molding and such for some of the projects at work so maybe I can have him practice and bust out a mold of that same Graupner jet with a bigger outlet or something? I'll check it out when I get it. For a Mt. Dew he'd do it! )

I bet that big one could be modified to work but my main concern would be in a hull that small....27" or so it would make the intake to far forward and not do any good for the performance part of things anyway. Think it'd be a cavitation monster then.

Think I'll order the hull and smaller drive tonight and see what kind of trouble I can get into next week! Thanks for the input guys.

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DRAGONFIRE81M

not sure if you have seen my 31" deep v with a 29mm drive and a ammo 36-50 2250 on 22.2v but this drive will hall ***** http://www.youtube.com/watch?v=hJNx468n45E

oh yeah and dont run 22.2v on an ammo thats rated for 18.8v it died only 4 more runs after that video

Quicksilver

dragon, that thing does haul, I'm not sure that I had seen that particular video before.

Tentatively, since I cannot balance my new octura props, I might get to fixing the jet-villain today. I have to split her right down the middle.

-

5150cat- One thing I've been wanting to do is tighten the nozzle on the 29mm jet. Technically speaking from full scale boats, the faster you go, the smaller the intake and nozzsle should be, since it will increase pressure in the bowl, there by increasing the exit velocity of the jet. So far I did decrease the intake are of my jet unit, but I havent messed with the nozzle. When I finish the hull, I post some pics of what I've changed.

DRAGONFIRE81M

you have to split her right down the middle.?????? what?[X(]

5150Cat

LOL.....split her.....hehehe!

Quicksilver. Trying to wrap my brain around what you said. You said the intake and exit nozzle should be smaller for faster speeds? That's messing with me. It seems like you would want to keep the rear nozzle small or stock, then make the intake as big as you could and then have huge amounts of torque and motor to thrust that water thru, compress it down and have it exit the smaller nozzle. Right?

Bigger in smaller out means faster and more force. I think. But it's my day off and I've had nothing but Dew so far so I could be way off! Not convinced my brain has kicked in yet!

In the same breath though it seems as though no matter how much torque or motor you have there is a maximum amount of water you can have pass through the exit nozzle. There's a point at which you it would be crazy. But then I think of when my buddy from Oregon cuts granite countertops with a water nozzle. That's an extreme case but same theory.

We'll see. I'm going to order the hull and mid sized jet and then play with HP's and RPM's.

Dragonholy freakin crap that thing is insane! That's pretty much what I'm going for. I think my Jeti is only rated at 11.1v but I think I should be able to make it scream. We'll see how it works. Either way I'm due for a new project. Pretty impressive though when you have to actually fight to keep the hull in the water at take off!

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5150Cat

One other question not sure if you guys will know.

Is there any diff in the 550 and the 750 Aquajet? Not thinking so and don't care about any other hardware. I can also reinforce the transome so I'm not worried there either. Doubt there's any diff.

I'm having a helluva time finding just a hull so I'm going to get the kit off of Tower but all they have is the 550 right now. Which should work fine......

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5150Cat

Just ordered the motor mount, and the jet drive with some random couplers to get things started. I'm holding off on the hull in case I need to order a battery also. I have a couple 11.1 3c's and a Venom Power 20C 5000mAh 7.4V as well.

What would you guys recommend for power. Got the specs on my esc.
Input Voltage 6-30v
Current: 125A
Lipo 3-7 cells
0.0010hm resistance

And it's watercooled as well as my motor. So I need to figure some major juice to pump to this sucker!

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DRAGONFIRE81M

looks like your pretty close to the same set up my esc was rated for 25v 50a and my motor was a 14.8-18v at 14.8 youll be running around 39k rpm thats your max inless you combine some pakes to get 18v since thats your max on that motor your planning . the rpms on that video is almost 50k rpm

i also lave a 14.8v run that would be just a little slower then yours at 33k http://www.youtube.com/watch?v=KSwoqBZp-uU

alloutcustom

Anyone have a completely ruined jet on their hands? PM me. I would like to make a jet ski hull or a jet boat hull out of glass and need to get one to design a boat around it. The jet ski i would like to make an exact(as close as i can get)replica of a kawasaki 08 jetski. And maybe a jet boat.

Quicksilver

well the intake nozzle thing is hard to wrap your brain around, I still have trouble sometimes.

Since I have trouble explaining it, here's a pretty good explanation, it's not quite as simple as I explained before, but.... anyway

"Impellers (and jet-pumps) work on the principal of positive and negative pressure, or a push/pull concept. As a blade rotates, it pushes water back (and outwards due to centrifugal and accelerated force). At the same time, water must rush in to fill the space left behind the blade. This results in a pressure differential between the two sides of the blade: a positive pressure, or pushing effect on the blade face and a negative pressure, or pulling effect, on the backside of the blade. This action occurs on all the blades around the full circle of rotation.

Thrust is created by water being drawn into the impeller and accelerated out the back. To further enhance velocity, water passes through the venturi before finally exiting the pump as thrust. The venturi works on the principle that a restriction or reduction in line size will cause water to accelerate if the same volume is to be realized at the other end of the restriction. This is where you get the "jet" in pumps. Finally, a steering nozzle is used to vector or deflect thrust for yaw direction.

Impeller design and efficiency is strongly linked to the other components that make up the jet-pump, i.e., the intake gullet, its volumetric area, the laminar transition of the intake housing, stator blade area (including angle of trajectory), venturi rate of compression, venturi "bowl" area, exiting orifice dimension, mass and weight of the hull, and pump placement or depth within the same.

The intake gullet is the recessed area within the hull leading up to the entrance of the jet pump. This area plays a vital role in jet pump efficiency. There are a multitude of factors that determine its length, size, shape and depth. For instance, a larger vessel with greater displacement may choose an intake gullet design with a more gradual rake leading up to the jet pump entrance. This maximizes the amount of water available for acceleration. In this scenario, intake gullet vacuum is not as critical because the weight of the hull (and the depth of the pump) will keep the intake cavity primed. In contrast, a light, high speed hull that rides closer to the water's surface, may use an intake gullet with a more aggressive rake and a reduced intake gullet area. This decrease in cavity size, increases the vacuum (or negative pressure zone) at the intake, which helps reduce ventilation brought on by a higher speed planing hulls that operate near the water's surface.

Ultimately, the best intake gullet design would be variable in size. In other words... larger for acceleration and smaller for high speed operation, to maximize intake vacuum when aeration is present." -some genius propulsion engineer
-
The nozzle by definition, should be smaller at high speeds simply because as said above the exiting velocity must be higher than the intake velocity in order to achieve a higher speed. So technically if you made a smaller, steeper raked intake and a smaller nozzle output, the boat could go faster, but will accelerate slower.......It's all crazy engineering efficiency principles.

With my boat, I did make the intake more aggressive and smaller and moved it towards thew stern more to decrease aeration. I had to make a step to protect the jet, but the principle still holds.
-

Dragon, yeah I literally have to cut right down the keel and re-work the whole bottom since it isnt completely flat......rather complicated. I almost worked on it, until I installed an on board camera on my rustler. I've got far too much rc stuff now.

Alloutcustom, I might sell/trade you my old kehrer drive, just has the broken stator and well no impeller. However if you got a graupner impeller it would be repairable. I'll have to think about that. Maybe for a brushless esc (60amp or better) I'd give you a boat with the pump installed.

5150Cat

Quicksilver,
Thanks for clearing that up. That makes more sense now. Either the Dew's worn off or just having time to sit down and think about it and draw it out seems to make it alot clearer. Thanks for that!

I'm looking forward to getting the boat going. Should be a blast to race around with.....

Also bidding on an ABC Hobbies Cesa 1882 on Ebay. I had one years ago and it was a great hull. And it's got a pretty shallow V that looks like it might fit that bigger jet into it a little easier. We'll see what it goes for but I think that might be a good candidate for a jet also.

5150

Quicksilver

no problem, it's pretty confusing. It reminds me of a Futurama episode.

"I understand how the engines work now. It came to me in a dream. The engines don't move the ship across the universe. The ship stays in place and the engines move the universe around it."

I ended up over complicating this picture, but I thought why only show two versions, let's show them all. You can see the intake, running surfaces and harware changes over time. There never really was anything wrong with any of them, but I like tinkering.
edit; since that came out so small, here's a pic of version 3.0 next to my surface drive villain.

5150Cat

Quicksilver,
Nice, pics help alot actually. And dang it you had one of my ideas in those pics. When I was making upgrades to my waverunner, one of the best upgrades was an extended plate that ran about 8" past the back of the hull. I want to say it was even with the end of the jet nozzle. What it did was help the hull from bouncing around when you were at speed. Also helped it get up on plane that much quicker but that doesn't seem to be a factor here.

The other thing I was going to steal from the ski's was some side fins. On each side of the rear of the hull there were these little plates....about 1 1/2' long that were adjustable. When you adjusted these things down and took a corner with the throttle nailed the G's would rip you off the ski if you weren't careful. Sort of like a skag I guess but being on the side of the hull really seemed to make a pretty big difference. Not sure if it will work for these boats. I ordered some trim tabs also just to play with but we'll see. That's half the fun is tinkering like you said.

5150