Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length.

[XV Pilot]

Hi!

As I am sure some of you know, the Robbe Katja does some strange things when cornering at speed. From what I gather, it has a tendency to roll onto its side when turning, and stay there even when rudder is released. The only way to get it back onto an even keel is to back off the throttle.

I am very much new to RC boats, and I have yet to take delivery of my Katja kit, but as I plan to run a fast 540 motor in it that I have left over from my RC car racing days, I anticipate that I will experience quite a bit of this behaviour unless I can do something about it.

Does anyone have a sufficiently good grasp of hydrodynamics to be able to explain to a layperson why the boat does this? And does anyone know what is needed to prevent it? If the hull needs to be modified, trim tabs added, transom extended, chines altered, turbulators applied or whatever, I'd rather do this as part of the build, rather than trying to retro-fit.

Thanks!
- XV

[Stavros]

http://www.youtube.com/watch?v=bUlb1bgUPv0

http://www.youtube.com/watch?v=VwqJ0uv6z5w&feature=fvwrel

Cant see anything really amiss with those vids


Dave

[essex2visuvesi]

One big thing regarding the Katja.... she does Not like to go in reverse at any speed above a crawl.  Too much speed in reverse and she will submarine.

The kids one is running a forwards only speed control for this reason

[roycv]

Hi from what I remember a fast car motor is wound differently to a good boat motor.  You are after torque low down for car racing and have few turns on the armature.  Boat motors are wound to have more turns to get power at higher revs.
Perhaps check with the guys you want to race with?
regards Roy