Graupner Hydro Sprint
 

Just bought a Hydro Sprint to play with :)

Stock motor is a speed 400 7,2V , but I want to try my Himax 2025-3200 brushless.
I have no ideait it will run right with this motor.....but its worth trying :D

Here are some pictures of the kit.

RE: Graupner Hydro Sprint
 

..

RE: Graupner Hydro Sprint
 

Making the "steps".

RE: Graupner Hydro Sprint
 

Hey SJN,

As you know I have a sprint and a brushless setup just like that, I toy'd with fitting the brushless in mine but after testing it with a 400 6v I decided against it, here are my reasons:

1) The brushless ESC is about 2/3rds of the size of the motor and it was going to be a squeeze to fit it and still be able to remove/replace the battery pack

2) The brushless gets hot and as I'd already fitted a switch in the rear I had nowhere to fit a cooling inlet.

3) the motor mount is ideal for a 400, but is only fixed on the shaft with cyano, it's already twisted free once with just the power of the 400, If you fit the brushless it'll need reinforcing or it'll tear the driveline apart.

4) It was already crazy fast and as the hull barely touches the water I feared it would be damn near undrivable with all that power, which is why it's going in my Gecko instead

However I'd love to see one in action, keep me posted

Couple of tip's I picked up building mine, keep the sponson edge's and ride point's square, it doesn't mention it in the instructions but it really reduces friction.

Uncase the receiver if possible it already takes up a lot of valuable space, make an aluminium turn fin the plasticard one has too much flex

Enjoy, I love these things, micros are the future!

RE: Graupner Hydro Sprint
 

hehe, thanks for the tip.
Ill secure the motor better.

Im "gluing" mine into the hull with some Rubber RTV, so I can caut it out easier later if needed.

RE: Graupner Hydro Sprint
 

Just gave the black coupler some more........this should hold it down. :D

RE: Graupner Hydro Sprint
 

That looks pretty good should brace it well against torque.
Keep up the good work...

RE: Graupner Hydro Sprint
 

Prop depth looks quite deep......but it is exactly in accordence with the 1:1 drawing.

RE: Graupner Hydro Sprint
 

The prop looks ideal to me, don't forget that it carries quite a lot of weight relative to it's size (not so much in your case, be careful that it's not too light!) so it'll sit very low in the water at rest and needs a deep prop to bring the rear up.

A top tip I got from somewhere else is to go straight for full throttle at startup, if you try to idle the cell pack weight will literally dive the nose below water (believe me I've done it), ease back on the throttle in the turn or it'll spin out.

By the way, love the miss Bud, something of a work of art those proboat hulls...

RE: Graupner Hydro Sprint
 

Yea, the Bud looks fantastic.
Im waiting for our pond to get filled up, before I can run it.

I just sealed up the esc, so water wont damage it.
Non corosive sealant was used.


Unfortunatly, I have to go to work now (night shift) , and have 12 hour shifts here in the weekend.....so there wont be much progress until next week :)

RE: Graupner Hydro Sprint
 

Had some time to finish her up, and went down to the lake to give it a sprint ;)


Well, Im pleased, and a little disapointed at the same time. This motor is very powerfull......maybe too powerfull :D

It scoots along nicely at around 1/3 throttle, but if I go to 1/2 throttle, the nose lifts quite alot off the water, and only the front turn fin is in the water. As the fin is on the right side, the boat veers to the right all the time. If you correct slightly with some left rudder, the left pontoon contacts the water, and it turns violantly to the left......it keeps zig zaging like that. [:o]


I might try to remove the tunfin, or add another on the opposit side....... and se what happenes, and try to move the CG a little forward.

RE: Graupner Hydro Sprint
 

Nice job, you should be pleased!

I think you might be right, it's a combination of a lot of power and not enough nose weight, even with a 400 mine is pretty skittish and takes a lot of corrections to keep on the straight and narrow, I don't know about the extra turn fin as this will increase drag and you might find it wont turn in either direction well as it is supposed to pivot around it.

I'm curious, what's the all up weight, if you are well short of the recommended 550g, I don't see why you can't ballast it up a little in the nose or even up to say 600g all over to calm it down a little, it's not as if you lack power to move the mass!!!

If it's any help my 2/3A 9.6v cell pack weighs 175g, I expect your Lipo's are half that AND higher voltage (11.1v right) so more weight can't hurt

How high is the heat from the motor and esc after the run?

RE: Graupner Hydro Sprint
 

Hi Gaijin.

Im at work now, so I cant weigh the boat.
The batt 1500 kokam 3s pack weighs 105g, so I can insert plenty of ballast.

The motor was quite warm, but nothing to worry about. The esc and battery was hardly noticable warm.
So it cant be using that many amps. But I did not run the pack down. Only sailed for 4-5 minutes below 1/2 throttle.

RE: Graupner Hydro Sprint
 

445g with the liop batt.

I have removed the turnfin, and see what happenes tomorrow:)

RE: Graupner Hydro Sprint
 

I look forward to find it.

You are either a crazy man or a genius (or maybe a bit of both!) [sm=biggrin.gif]

RE: Graupner Hydro Sprint
 

Hi Sonnich,

Nice work on that little monster!

The propshaft angle is much(!) too steep though.
You'll need a flexshaft or a 1,5mm steel shaft (bendable) and a strut, to make the propshaft angle close to zero, or you'll never be able to run full throttle.

Regards, Jan.

RE: Graupner Hydro Sprint
 

Hi Guys.

I tried it again today without the turnfin, and now it can come up to 1/2 throttle safely. :D It turns quite bad now at high speed.

But now it has a new problem. The prop is "walking" on the water, making the boat yaw sideways. The faster it goes, the more sideways the bout is....even though its going in a strait line! :)


Thanks for the tip Jan, I wonder where I can get one....

RE: Graupner Hydro Sprint
 

Ah now that's easy,

And I expect Jan might suggest the same, try

[link=http://www.hopf-modelltechnik.de/]Hopf[/link]

RE: Graupner Hydro Sprint
 

Thanks for the exelent link ! :D

RE: Graupner Hydro Sprint
 

Gaijin, there are too many to choose from !

which one should I order ?

RE: Graupner Hydro Sprint
 

Well that's a bit tricky, you will need to buy a flexshaft, motor mount , strut and prop (the 2mm graupner one will not fit), I would be tempted to suggest this one:
Hydraulic 1 wave plant 2mm BBmit aluminum rudder 1

But, I'm afraid that I don't speak German and therefore I am unsure as to what is a flexshaft and what is a solid (Babelfish struggles with technical descriptions), I do know that Hopf will cut the shaft to length for you to suit what you need as flexi's can be a bit tricky to cut yourself, the best advice I can give to prevent confusion is to PM Jan (Pomplebled) and ask him, he has WAY more experience than me in Pro setups and Is an alround nice guy, he'll help out!

Good luck, If I can help any other way I'll try

RE: Graupner Hydro Sprint
 

Thanks [8D];)

RE: Graupner Hydro Sprint
 

http://www.hopf-shop.de/product_info...da0fb5c977a648

Hi Sonnich, this is a 2,2mm flexshaft (Flexwelle) with strut for 400-480 type motors, make sure to give the correct length when/if you order.
Also make sure it includes an endpiece (Endstück) with thread for the prop.

Just let me know if you run into translation difficulties...

Regards, Jan.

RE: Graupner Hydro Sprint
 

How's it going Sonnich?

Did you try it with some ballast while you wait for the new propshaft?

I recommend you put the turn fin back by the way...

Many boats suffer the same issue of the back shifting to the right, it's called propwalking, the rotation of the propellor pulls it sideways.

RE: Graupner Hydro Sprint
 

Yes, I tried the ballast at the same time I took the fin off.

I think the answer is like Jan said....a flex shaft. At the angle the prop shaft is now, it just making the bout fly out of the water, instead of pushing it forward.