critx

Hy everybody,

In my town we are just few people who build and drive rc boats.
We want to arrange a speed boat competion with the following restrictions:

- brushed motor not more then 300g weight;
- battery not more de 12Volts;
- monohull construction boat;

I am not to experienced in boat design and build, but I want to participate and I

want also not to be the last place in this competion.

So I would like to help me with few good advices.

I decide to get a 600 series motor:
Volt: 7.2 - 9.6 V
Nr. cells: 6-8 NiMH
Current: 10 A
max. Current: 25 A
RPMs: 14000 rpm
Diam. ax: 3.17 mm
Weight: 220 g
Dims: D38 x L57 mm

The hull will be a V construction (balsa covered with fiberglass ) but first thing I have to decide is where is
better to put the propellor:
- submersed or
- hydro

rebuilder

First question is, can you run lipo batteries, and can you use any brushed type speed controller? Also, how long will the boat be? I have some suggestions, but need to know these answers.

critx

Thank you for quick answere @rebuilder,

- the restrictions referes only to max. voltage so I can use 2S or 3S LiPo up to 12V (actualy I have 3pcs. 3S LiPo );
- no restrictions applies to brushed speed controller;

There are no restrictions to the lenght of the boat.

rebuilder

Ok, good, 3s lipos are deifinitely the way to power it, 25c continuous or better would be best. I see you are suggesting a 600 motor, i checked into 700's and the lightest came in at 320g, no go there. I would suggest a graupner 600 motor or the kershaw designs 650 revolver: http://www.kershawdesigns.com/ . The 600 graupners come in different nominal voltages........7.2, 8.4, 9.6 and 12v. Here is the one i would recommend of the graupners: http://shop.graupner.de/webuerp/servlet/AI?ARTN=6310 . The specs are as follows:

Nominal voltage 9,6 V
Operating voltage range 7,2 ... 12 V
No-load rpm 14300 min–1
No-load current drain 0,8 A
Current drain at max. efficiency 6,6 A
Current drain when stalled 55 A
Max. efficiency without gearbox 75 %
Length of case, excl. shaft 57 mm
Diameter 35,7 mm
Free shaft length 11,9 mm
Shaft diameter 3,17 mm
Weight 194 g

The Graupner 8.4 seems to like amperage a little more, it may have more torque. Its stall current is 87.5a compared to 55 on the 9.6

http://shop.graupner.de/webuerp/servlet/AI?ARTN=6309

specs:

Nominal voltage 8,4 V
Operating voltage range 6 ... 9,6 V
No-load speed 17000 min -1
No-load current drain 1,2 A
Current drain at max. efficiency 9,5 A
Stall current 87,5 A
Max. efficiency excl. gearbox 76 %
Permissible rot. direction R and L
Case lenght, excl. shaft 57 mm
Diameter 36 mm
Free shaft length 11,8 mm
Shaft diameter 3,17 mm
Weight 205 g


The esc i use on several different applications is what i consider a bulletproof, inexpensive, 10 cell esc ($35, cheapest ive ever found) Its the Streak....here it is: http://www3.towerhobbies.com/cgi-bin...&I=LXD523&P=ML

You probably need to go with 22-28 inch hull............somewhere in there. Im thinkin surface piercing myself, with somewhere in the range of an octura x435-x440.

ryan_t888

Is this for Oval racing or SAW racing?
Oval = several laps
Saw = Straight line racing 2-3 passes max.

Ryan

critx

Hy again,

@ryan_t888 will have a Oval race 3 short laps.The lake is 250m long and 130 wide (I have measured it in GoogleEarth).

@rebuilder I think I'll choose the Graupner motor becouse I have a local dealer near of me.
Regarding the controller, I'd never buyed things from TowerHobbies but I'll try to find a good one,from our local dealer (Robbe, Graupner) .
The prop. you suggested I cannot get it but tomorrow I'll show you some other possibilities.

critx

I found also that in our contest, the max. lenght of the boat is 600mm (~23 inch), and no other restrictions.

I would like to ask you kindly to suggest some V hull plans.
Next week I'll start to build it.

EmersonHW

i've used the graupner speed 600 race motors and theyre great. grsupner motors are really good. good luck with this build and post pics!