Zee

Hi,

I have just completed a Graupner mini sprint with a Mini ac 1215/12 brushless setup, 45000 rpm kokam 1100mah lipo cells. Mini servo and micro receiver. Futaba uap8 radio. The boat weighs 400g as opposed to the std setups 590g.

It is very very fast, full throttle is not possible, I have reached 3/4 on water like glass, it is very entertaining to drive.

Anyone done a similar machine?

Regards
Zee

Zee

...and the forum is speechless...

kwiktsi

I haven't done anything like this, BUT I have been wanting to for a while and couldn't figure out what hull to use. I wanted a small, light 400 sized boat to run on lipos like you did. Maybe I will look into the mini sprint. Any other ones out there that you can think of that are similar size just so I have some options?

Zee

I chose the Mini Sprint because of its scale look, MHZ makes a range of s400 size boats. I like the Volvo Batboat, I think I will do one of them next.

I highly recommend trying this combination, I struggled for many years with many combinations of electric boats. So this boat has been really rewarding.

Red Rocket

I just ordered a mini sprint today! I was wondering, stock with the speed 400, what batteries did you run? Was it fast?

hellomynameisdookie

What about upgrading one of those 380 sized ZigZags to a brushless setup and lipos? How do you think that would perform?

Zee

The Mini sprint is quoted at running 15mph standard, using lightweight radio and lipo power you can reduce the weight by a third. This has to translate into speed. I would use a 7,2v speed 400 motor so that you dont over tax the lipo's.

The Zig Zag racer looks like it would go like hell on brushless, it has no rocker at the transom so flat out speed should be good, but turning might be a bit unresponsive at speed. The good thing is the fact that it is a self righting hull, the last thing you need is $300,00 of electonics going up in smoke.

What I like about the Mini sprint is that the whole scale setup ofthe boat seems to work. The wing is supposed to parallel to the water, as soon as the bow of the boat pitches up, the wing lifts the back up, therefore the boat runs very flat. It has a double step in the hull that works too, kind of like a hyrdoplane would, it aerates the water under the hull reducing friction.

Believe me, I have been flying planes driving top end cars and gas boats, for ten years and nothing has left me with more of an adrenalin rush than this setup, it really performs.

mr-2

Hello ZEE, iam new to this hobby and after reading your post, i very serious of thinking getting the Graupner Mini Sprint 400,the problem for me is, here in Canada i don't think i can get it, so if you know anyone or yourself that wants to sell a boat that has simular set -up please let me know.Thanks!

pompebled

The Mini Sprint out of the box with the 400 motor is a rather slow affair, even boring I would say.

We raced them a couple of years ago in our club, and though it's a nice view to see eight similar boats running around the track, the pilots gave it full throttle at the start, put their left hand in their pocket and steered it round the course, while talking among each other, with one eye on the boats...

The "Zee" setup is quite another animal, but I would not recomend it as a first boat, you'll need some experience in settig up such a fast small boat before trying this.

Not quite scale-like, but easier as a first mini is the MHZ Gecko ( www.mhzusa.com or www.mhz-engines.com ), glass epoxy hull and very fast too (depending on what you throw at it of course), I've seen them with the standard 400 motor and with brusless motor (virtually undrivable, see Zee's post) to a version with a nitro engine that touches the water every four meters or so.....

Regards, Jan.

Pennywizz6

I might get a gecko by mhz! How much was your motor and controller setup and where did you find it!? Please link me!

Thanks,

Phil

Zee

Hi Phil

Dont discount the Graupner boat, it is very fast, and I am sure the wing is a big part of that. It holds the nose down, keeping it level.

I got the whole setup from MAD Models www.madmodels.co.za

You can buy from www.hobby-lobby.com, the price are all on the site, just do a search for mini ac. You will look at about $350,00

I would investigate other motors as well if I were you. The new multiplex motors look quite good too.

Also dont forget to water cool the motor. Otherwise all the smoke will come out of the ESC and then it wont work anymore.

I am looking at the idea of putting the Mini Ac into a jet type of s400 boat , who knows what to expect? I beleive that water jets only start to perform at 10000rpm, so putting 40000rpm into one should cause quite a stir.

This little motor is really fascinating me, I am putting one into a F16 jet, the unit produces 18oz of static thrust. The plane only weighs 20oz the performance is going to be very interesting. 80mph here we come...[:@]

Velocity-8

My Feedback: (15)

I just completed building a Mini Sprint. Great little boat IMO. I also have a Zig Zag 1 and 2, a Reef Racer, H2O and Villain.

The Sprint is too fast for the pool so I use that at a local pond. With a stock set up and a 7 cell battery it runs pretty fast for a small boat. It has a lot of potential to to be a screamer with the right motor. I got the kit for $45 brand new on a clearance sale but they should sell in the US for around $70.

Here's some pics...

Zee

Hi Velocity-8

Some time has passed, have you made any mods to your boat? I have just ordered a 2-turn brushless motor for mine, I am going to try and blueprint the hull using carbon fibre sheeting, to get it cleaner. I am also going to change the prop to a brass, balanced and polished version. I may add turn fins to help keep it on the water.

I have had a couple of boats, including some very loud K&B powered nitro boats, but this little boat is still very exciting and challenging.
So I want to make it faster...

Will let you know how it goes...

Cheers-Zee

Velocity-8

My Feedback: (15)

Actually I sold that boat to a member here. It was too fast for my pool! That boat with a brushless motor would be pretty insane!

Airmicro

My Feedback: (2)

Hey Zee, what esc did you use? I have a Graupner Mini Sprint Hydro I'm doing, and am thinking of doing it BL.

Zee

Hi

I used a 25A model motors esc. (not reccommended) future setups will have Jeti controllers.

I have just received a HET 2 turn 4650Rpm/v motor, this is going to get interesting.

Zee

northernmike

what good luck to find this thread! just rebuilding my mini sprint, have had it in stock form on a shelf for some time. bent the propellor shaft. so now i'd like to set it up right. Zee you are an inspiriation. can i ask how you built the drive system? i have had small and great experience with small diameter driveshafts, ("piano wire" ) but this looks already tiny @ 2mm.... is there something harder i can use that won't bend as easily? do you happen to know the thread for this shaft? i'd like to source a tap and die. what propellor are you using to handle such power?? 45k rpm is just barely believeable. what kind of runtime do you get? i neglected to use the wing when i built my boat, and now it is lost... but i don't expect to afford brushless right now. perhaps 8 cells and the stock motor - but i'd like to get the propellor and driveshaft right at the very least. any help is appreciated.


also agreement with you on the Jeti controllers - nothing but good results and reliablity in my experience.

regards,

- mike

nighthawkhk

Hi Folks

I need some expert opinions from you.

Just finished the Mini Sprint with the original Speed 400 motor and original prop. The boat is running on 6V with a 5 cell NiMh 1200mAh pack. The weight is exact 500g.

The only thing I didn't mount is the wing, because my kid is running it in the pool and the wings would have been most likely crashed from time to time against the pool wall.

The problem is, that the speed is quite boring. The running time is good, about 20 to 25 min. It sounds like the prop is cavitating since you can here this "blubber" sound from 3/4 throttle on.

Has anybody any suggestions for prop, replacement motor and trim? Would be highly appreciated!

Greetings from Hong Kong!

Velocity-8

My Feedback: (15)

5 cells is good for a pool. I ran 7 GP1100 cells in my MS (pitured above - no wing either) and it was WAY to fast for my 32' pool. Try adjusting the prop down or moving the battery to stop the cavitating. Keep in mind that the MS is a surface drive so you get the "bubbling" sound.

Zee

Hi Nighthawk

Thanks for reading our post, personally I am amazed that 1025 people have read this thread. I think it is interesting to experiment with the micro boats, I am involved with high performance boats full scale, and many of the innovations can be found in models. The wing and the step hull are amazing advancements. The fact that for $500,00 a person can have a glimpse of the characteristics of these machines is wonderful (Reynolds factor excluded), for a young guy this can only lead to future development and advance.

For your boat, I would strongly suggest a brushless motor, there are many available with the same mounting pattern as the S400. It is worth the money.

How big is your pool, my pool is 50' long and the boat virtually jumped out of it?

If you dont want to put too much money into this I would look at a Speed 400 6V motor, they are stronger than the 7.2v motor. You should check the balance of the boat longitudinally. Change the prop to something a bit sharper or sharpen the one you have. Make shure your driveshaft is very well lubricated. Try LiPo cells. Did you install the trim tabs?

As the classic saying goes...

Speed costs money, how fast do you want to go?

Good luck, please let me know what you decide, and the results?

jsm922

I was wondering if you have done the Volvo Bat Boat yet?

Reason I ask is I am trying to locate a fast electric version that is RTR using the Nimbus Hull?

If you know anything about it I would appreciate your help
thanks

Zee

Hi
Which model Nimbus were you thinking of? I like it a lot, stepped hull, narrow...
I think graupners one is an epoxy glass hull which would be great. They are a lot bigger if I recall, so you would have to look at a Hacker motor and much more battery power.
This would be a much more radical project.

fstop7

ZEE, or anyone else out there with help!

I am building both a Graupner MiniSprint400 and a HydroSprint... Want to put brushless in each of those. First off, what kind of drive shaft are you using--surely not the 2mm kit one? The 400-size brushless motors i am hoping to use have a 1/8in (3mm ?) shaft. What size drive shaft or coupling are you using/where do you find shaft and couplings for this size boat? Any particular motor mounts installed? Right now i am considering using a 4mm drive shaft to epoxy into the hull--would like to use standard thread-on 4mm props--but the shortest (length) 4mm driveshaft i can find is 10" long. Am planning on using a Multiplex BL-480 brushless motor (3.175mm shaft diameter). ALSO--what about watercooling--i regularly put it in my big boats with 700 size cans--but where do you find cooling coils for 400-size cans?
Any info/help anyone can provide for converting these small GRP hulls to brushless would be greatly appreciated!!


THANKS and hoping to hear some help out there!

Zee

You sure sound like you mean business.

Coming from an airplane building backround, my idea was to keep the boat as light as possible , that is why I put the lipo's in it, I used micro servo as well. The model motors is a speed 300 size motor. I see you are going for a speed 400 size motor.

Just remember the thing still has to float once you have packed it full of very high end equipment. For the amount of power you are going to put in,you will have to use a bigger shaft, otherwise you wont be able to use the size of prop you need. I used the standard prop size, but a bronze brlium version. My mount is the std graupner one it mounts the whole motor to the shaft, worked well, I think I was lucky this whole thing didnt vibrate itself to death. But it is a good system, it makes sure you have everything aligned. Cooling I did not install since my runs were short. I didnt want to burn out the lipos with the current draw. The heat did build up but not too bad, I just opened the cab once I got it to shore.

What are your goals for this project? What type of speeds are you aiming at?

Please keep us posted.

jdoug

What size brushless controller are you using for these little brushless motors? 30A?