Quicksilver

Well the jet-villain will be runnning once more, but way underpowered, basically like the beginning of my build thread. Doing this so my fiance has something to run and will be the rescue boat.

I recently bought out an old friend of all his rc stuff, as dragonfire kind of knows about.
Got a TRX Nitro Vee
2 futaba radios
2 six cell packs
1 30amp futaba esc
1 kinwald modified motor
1 20t traxxas stinger
1 johnson 540
2 chargers
and tons of tools and parts
Pretty much all 10yr old technology but all for $150

So the jet villain will get most likely one of the modded motors(water cooled), I've got a couple as well, and the futaba esc(gonna add water cooling). She'll be slow but scale.

Tugboat Andy

Hey guys

The NQD knock off arrived last night. I charged the battery for about an hour and threw it in the tub for the kids. After about 15 minutes the steering swervo jammed and the fun ended. Actually, that was better than I expected.

Time to cut into the deck. I haven't gotten through the whole thread yet but I have a question about cutting through the deck. I saw a picture and it looked like you make the cut so you leave the drain groove. It looks like there is about a 3/16" to 1/4" flange left inside of this.

If that sounds about right, I'll start cutting. Also - I'll try to finish reading all the posts before I ask another stupid question about motors and escs. A lot of the info is already here. I'm just not a fast electric guy yet and I don't understand a lot of the lingo.

Thanks again for the help and patience!!!

DRAGONFIRE81M

yes about 1/4 from the drain will work great . you wont to leave some for a strip of weather striping to seal against . and REMEMBER TO LEAVE THE BODY POST a good 1/2-5/8" on the front and bottom lips to give them suport . and some help on the reading i thank it starts on page 8 with headhunter

headhunter23

Hey dragon, perhaps we should make a post that essentially is complete in description etc for doing up knock off, then each time a person asks about em, just point em in the right direction.

Ivan.

DRAGONFIRE81M

sound like a good idea

Tugboat Andy

I think its an outstanding idea! Over at RC Groups we have a thread on everything to do with Springers. Almost any question you can imagine has been answered on how to build a basic Springer. I'm happy to post pics as I go along to help the next guy or gal.

There is a wealth of jet boat information on here. A ton of pratical information that cannot be found anywhere else. It would probably take thousands of dollars and many years to re-invent all the information you guys have posted here. Keep it up![8D]

headhunter23

Dunno abooot that but probably some good nuggets. Dragon you want to start the thread, and we'll try and get everyone to put some info for newbies?

Ivan.

paul73rc

Hey everyone,

Lately I have been craving the need for speed in RC boats. I have 2 Jet Boats (Graupner Jet Sprint - Knock Of Sprint) and running them fairly hard out I still don't put out the high speeds I am after. So, I need MORE speed, lol.

I have read quit a few pages here and there and from the info I have received, propellored boats are faster than jet boats.

Is this true? If I put the same electrics and engine in a jet boat and a propellored boat which will be faster? Also saying, the hulls are similar size - weight.

People have said that top speeds are reached mainly by propellored boats because jet boats can only get a certain amount of water in and it doesn't matter how fast the engine is.

So, any advice, information or help would be appreciated. Cheers and thankyou to all! Pauly

DRAGONFIRE81M

yes it true prop boat are way faster the jet . there mane perpose is for shallow running and quick take offs .

thanks head but i have no idea where to even start its alot of info for starters . you can start it since you where the first ganny pig and ill be more then happy to add to it .

paul73rc

Is there any prop boat that you would reccomend for high speeds? I want one that is small, light but still strong so I can achieve fairly high speeds. I am going for about 40mph, not sure if you think this is quick or slow, but that is what I roughly want to achieve. I have a water cooled 3600kv motor so I know need the boat.

So, basically I am asking: Is there any boat that stands out from others that you would use for high speeds?

Cheers, any advice is great!

headhunter23

Get a hull off ebay, 27-29" then get a hardware kit from OSE or somewhere. That's probably your easiest and best suggestion unless you wish to buy a used sv27 for not bad price or new for 300 buckish.

Ivan.

Quicksilver

and mind you 40mph is quite fast for a boat, an SV27 which headhunter suggested starts in the mid 30's, which is fast for a boat.

headhunter23

sv27`s top out at 40mph from what I heard, or is it 50. But serious hull mods for 50 if possible.

headhunter23

**INTERESTED IN GETTING INTO RC JET DRIVE BOATING CHEAP?! READ ENTIRE POST!**


Ok here`s the everything you need to know about getting into a `knock off`` jet drive boating for cheap. Little history, seems but not verified that NDQ bought the rights or mold off of the original jet sprint, or straight out stole it. The models side by side are near identical except for the spoiler or whatever it`s called for boats. Probably the best parts of jet driving is that you can run these boats all year round in streams, rivers and open ponds also running streams and such adds more excitement than running ponds etc.

How jet drive systems work - It's a water pump. That's all they are. Water is sucked through the bottom and expelled though the back which is directed left/right to turn. This allows for running extremely shallow and high manoverability.

Speed - Ah trying to figure out where to put this tidbit o info so sticking here especially because it's good to understand before you buy. These boats are not speed demons, don't get me wrong, they are fast, but will never compete with subsurface or surface drive systems in terms of top speeds attained. A jet drive system is generally 20% less efficient than the other two systems, which means you need 20% more power to run the same speed. The drives seem to be duplicates of the graupner mini jet drive which supposedly can do 22mph/35kph, not sure if they go that fast. They turn literly on a dime and have insane outta the whole, but max out as only so much water can physically make it through the pump. You can do minor changes to increase the water through the pump but for the "knock off" I wouldnt say it's worth the work for the increase. I would be surprised if it were noticibly at all.

Here are some examples of speed:
**Post your link here folks of your jet drive running speed and turns...


List o ordering:

1. Order boat
2. Order motor and esc with bec so you don`t need an extra battery pack
3. If your lucky you already have a radio system
4. Get a nice and light servo, 2.5g servo`s have worked well for me
5. Would suggest lipo`s for powering

1. Check out ebay, either look up seller: mideatoys or rc jet boat. The boat itself is cheap but the shipping looks expensive. Consider the whole cost as the value of the boat. For here in canada to my door it cost $52-56 depending on value of dollar etc, if you do live in Canada eh, then ensure it`s shipped via USPS, never with ups (they are *****`s and charge what I consider illegal minimum $25 bucks for anything across the border). In the states I think the total value is $10 bucks less bringing your total to $40ish. When searching the ebay sales, look for a little boat with 2 red helmut guys driving what looks to be a competition ski boat or atleast that`s what it looks like to me.

2. Motor selection is important. We try to run near the limit but for streams running near the limits can be completely useless. I run 7.2v generally and almost completely for streams and rivers, but will pop in 11.1v for ponds and lakes. When running streams etc is you'll have a tendency of hitting bumps jumps etc that break the surface contact of the pump. Then weirdly the pump will continue to run dry until you stop the motor and allow it to reprime(it's the only irratating thing, you can reduce this by a. slowing down your boat to fast enough, b. more weight in boat). (quicksilver I'm sure you have an explanation for this) Dragon what was the total rpm that we should be shooting for again? I completely forget now and don't want to go back through the posts to find it.

Running too high of a rpm doesn't seem to be susccesful and heats up the motor and esc rather quickly while draining your lipo's like thier going outta business. Your setup will also depend on how many cells your expecting to run and longevity of runs too. On 11.1v don't go any higher than 3200rpm/v and ensure your motor can do at least 30 amps. I would say 30 amps is minimum for whatever motor you get. 40amps max just due to weight restrictions, well you could go heavier but then will take more amps, more mah etc endless cycle of making a system that max's out.

Here are setups that people are running and their videos:
3200rpm/v 25amp, 25amp esc with reverse(which is handy if stuck on rock) - video later - headhunter
3500rpm/v 30amps I think - Dragon
**ah you guys will have to send me your setups and video links if you have them.

3. Radio systems, a basic 2 channel surface radio system works fine. There is no bucket reverse system on the knock off, so your esc will need to have reverse. But here's the kicker, for you to use reverse essentially you need the front stuck on a rock, or overload the boat till the drive is fully in the water. I've had 7.4v 4000mah cumulative and have been unable to get drive full under, its close but it really needs to be fully sealed. A nice light esc is always great in removing weight.

4. Ah yes servo's, lightest seems to work just fine.

5. Lipo's are the way to go, using nimh or nicd are just too bloody heavy, today's prices and especially the size of the boat mean getting lipo's is pretty cheap. You can run 2 packs in the boat or singles. Two packs make for easier balancing as you put them along the drive but will build more heat and use more mah in running due to increased weight. Single makes for a lighter ride but balancing is more difficult unless you kept the original top that you cut out and taped back in place after gutting. Generally most guys here are running 11.1v. I run 7.4v for streams as I like running light, reduces loss of prime and is enough speed to run. Pack sizes are generally around 2000mah I believe.

Here are some guys lipo selections in combination with motor rpm.
2 packs 7.4v 4000mah cumulative on 3200rpm/v - streams
1 pack 11.1v 1200mah on 3200rpm/v - ponds
**Anyone with knock off post your lipo setups...

That should give ya a head start on ordering.

Ok once you get this wonderful thing, charge battery and run the original system. See how crappy it runs? If you want more smiles some of the guys have over voltaged the system and had cheers burning out the system. Do you love how it turns on the original servo(is it even a servo)? Right neither did I, there seems to be a whole half second lag time from input to turn, on top of that it`s either left or right full, no intermediate.

So your done screwing around with the "toy"? Good, let`s get to it.

Cut the top off, this should be done carefully. You will want to keep the posts, so cut shy of them and leave a half inch on the sides. Keep the top! I have this idea that you can tape it in place and run single cells in the original location, not sure if someone has already done this mod. Later you will need this space on the sides and around the posts for helping to water seal the boat. After that gut the thing, I mean the whole thing, pull out the drive and everything. Get rid of all the hot glue. The best way to do this is to pry with some needle nose pliers, essentialy grab and twist. For me if the boat was cold, it seemed easier to break the bond of the hot glue to the model.

From here you`ll get ready for putting stuff back together. Best thing for me was to put the motor on the drive before putting in, it was the easiest for tightening and getting the coupler to work. Ah yes the coupler. Some have found that it cannot handle the power. I`ve used mine plenty and no issues, if I were you, I would drive till it breaks, save you 5-10 bucks out of pocket, if you do get one, best coupler seems to be straight aluminum, no flex drives or universals. For your cooler lines, place drive in boat and test to ensure you have enough clearance. The lines are generally custom, so far made from aluminum to stay light.

If it looks good, start gluing in the drive. *** do not use original gasket for back of boat, get rid of it, tis useless!!! *** I use shoe goo, makes a great seal and best of all with some coaxing you can pull everything apart without really wrecking anything. The trick for removing it is to grab with needle nose pliers a little bit and just rotate the pliers around and around and it will literly peel the glue off the boat. If you tried pulling it off you would more than likely damage the hull etc, on top of that it`s damn near impossible to just straight pry off.

Ensure you have a good seal when gluing, I like to put a bead all around the contact area then spread some on the inside kinda like caulking to finish it up. Now to make servo holder. Dragon`s design seems to work the best, simple yet effective. Grab some aluminum you can bend ... ahhh will have photos on this when editing.

Ummm add your esc, and receiver. Get rods and connectors in place and test out. I would test in a tub first as set screws have a terrible sense of timing for coming loose while out and aboot in the middle of a pond or some stream. Use CA glue to glue the set screws in place. Um... test steering etc.

Finally when everything looks good. Go hit the streams!


MODS TO KNOCK OFF

Prop replacements:

Bearing mod:

Painting mod:

Any other mod:

Ivan.

5150Cat

Well you guys suck! As if I don't need another project you have all got my interest goin in a jet boat. I need something fun that's quick and portable and will run anywhere no matter whether it's a pond or stream.

I'm going with the Aquajet conversion with the Graupner jet that some of you are running. Thanks to Quicksilver and Vdub for answering just about any question I could come up with!

My question is this. I have this motor:
HXT 36-56 2700kv Brushless Inrunner (WaterCooled)
Kv: 2700rpm/v
Required ESC: 80A
Voltage Range: 10-18v
No Load Current: 4.9A
Max Load: 68A
Max Power: 475W/60S
Weight: 317g
Shaft: 5mm
Here's the site for easier viewing: http://www.unitedhobbies.com/UNITEDH...idProduct=5146

Wondering how that will manage in that hull with some lipo's. I have a Jeti controller for it.....should be potent but I don't want to grenade that jet drive.

Any thoughts guys?
Thanks again,
5150

Quicksilver

From what I gather, the highest kv I could find being used for that jet was a 2300kv. I bet 2700kv will be alright, it'll probably scream if you keep her light. I keep forgetting how heavy my boat is. I was going to to say the kv was too high, but with lipos and not too much glass it'll be fine. I would run 3s(max)

headhunter23

Cat if you have 4s, I would test it for a short time see what it does. Gps it if possible, the drives do have rated speeds. I've got a kehrer in a villain and have run 5s 1680rpm/v 60amp and have still not maxed the drive to full potential.

Ivan.

5150Cat

Thanks guys. I think I'll give that a shot. I don't really have anything battery wise picked out yet. I have a couple 3s 11.1v laying around but I was going to build the boat first and then order the best battery for fit and power.

Holy crap 4s.....what kind of speeds do you think I could obtain with a 3s or 4s? Obiviosly I'm not going for a drag boat here but I have issues with overpowering things! )

I have no idea what to expect other than watching your guys vids! Pretty excited though. Should be a fun boat!
Thanks again for the input.
5150

5150Cat

Sorry, thought of another question.....

What are the differences between the Graupner and the Kehrer drives? Since I'm in the states would it be worth trying to get the Kehrer? Everything I've gotten from Germany boat wise has nothing short of rocked.....but they look pretty close.

What is your take on that Ivan? And Quicksilver I believe you have had pretty good luck with the Graupners.....any con's?

5150

5150Cat

Holy crap you'd think I could get it together to get all my concerns done in one post eh? LOL!

The reason I'm looking at the Fehrer jets is strictly for the 33mm vs the 28mm. It states that it's the same as the 28mm only a little bit fatter for better speed. And it also looks like it's easier from what I've read to get a couple of extra impellers from the start in case I end up jacking the original one up. From what it sounds like if you chew up one in the Graupner you're better off ordering a new unit vs just the impeller.

Also, do any of the drives come with an adjustable trim? As in adjusting the nozzle up or down? I know my Waverunner had that.....obviously not r/c.....but it was nice to have the 5 adjustable positions. And it's always nice to have options for different conditions. Curious how hard it would be to modify the jet?

Ok, that's it for tonight.
5150

Quicksilver

I've discussed my qualms with the kehrer many times on here. I'm not too keen on them, mainly due to price and lack of replacement parts. You can usually get replacement impellers for the graupner 29mm, the mini jet is the one that is hard to replace. I've had my graupner drive for 10+yrs now and it's been in two different boats. My kehrer drive lasted 5 runs and then the stator broke(which is pretty important). I recommend Kehrer drives for scale applications and for special applications like the sub that was recently built on here. They're built better, BUT I question their plastic(brittle). For high speed I dont see a point in them, theyre so close in design it's funny.

I agree as well, you could try 4s, but you get diminishing returns the higher you go.

I'll get to the other questions tomorrow. Been working in the heat all day.

Tugboat Andy

Headhunter23

Thanks for the NQD knockoff post. That condenses a lot of the information in one place which makes it a lot easier to read. That was alot of work and I am sure a bunch of us appreciate it. Thanks!

When you have time, I'd be interested in your thoughts on the following (I know you have a life and I don't expect you to rebuild this thing for me....[]):

A source for a straight coupling. I don't have the ability to machine my own. OSE???

I seem to recall someone modified the intake grill? Should we cut out the plastic grill that comes with the boat and glue in some rod or is that a mod for a rainy day?

Should we throw away the screws that hold the drive in and fill the holes with something?

Many thanks! [8D]

headhunter23

Cat:
Ya know you can edit a post right? No disrespect, I do the same thing sometimes... anyways quick is more the captain on the differences between the drives. My only real issue with the kehrer drive is the cooling tap does not work. I tapped it and there is no water pressure where it's located. I think the graupner one works though, right quick? Other than that it is made better than my graupner mini for sure but I never got the 33mm. The graupner looks easier to put in though. As for up and down motion, quicksilver had one made for his... kehrer drive?

Oh yet another, you can only get the kehrer drives from germany and shipping is huge, esspecially when converted, so price wise it's better to get graupner.[X(]




tug:
yea ose works for straight shaft. Machining one is a real pita, I would say it's worth it to pay for one just because it will be truely balanced. Yea I had modified the grill because the original broke first run and it was flimy. I put in very thin carbon fibre rods, just dremeled the plastic enough for them to fit in.

Yes throw away screws, fill in holes with either goop or epoxy. Epoxy would allow for a smoother bottom.

Will update the post in a bit.

Will try and go back to find photos and posts of stuff in a bit.[:'(]

Ivan.

DRAGONFIRE81M

I thank i had a 2700kv in big blue but to really go i was running it on 6s so i went with a 3300 kv so i could run it on 3s and get close to the same speed this is on the 29mm grupner drive

5150Cat

Dragon,
What kind of motor was the 3600? Any website recommendations?

5150