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[Drkomen86]

well Im having a poblem with a model of mine, wonder if you can help.
It is a deep vee hull and running a flexi-shaft with a brushless motor and one of thos red plastic UV joints, problem is that the joint vibrates and after a while it will just fly appart 
Does anyone has any ideas why this is or a way to stop it?

Also for no reason it flipped over 

any ideas people?

[Tugwash]

Hey Drkomen86

You should look at checking your motor alignment to reduce the vibrations that the uv is creating, a poorly aligned motor will cause excessive vibrations and destruction.

I can only assume you are running the boat at max speed for to long a period to make it randomly flip over, thats a common issue with fast boats is that to much speed will make them unstable in the water .

Harry

[Drkomen86]

Thanks will look into it.
To be honest it hasn't ran for that long, all I can think is it hit a ripple or something.
If that is the case how can I stop it?

[Tugwash]

Im not entirely sure, i have not run any type of power boats, i can only suggest to watch your speed, not to run on anything that's to choppy, possible add a bit of weight at the rear to help bring the nose up a tad, you may need some type of stabilisers fitted to the rear.
 I think that there are others here that may be able to give you better guidance to stability of power boats.

Harry

[Tombsy]

Is the red coupler between the motor and the flex shaft?
If it is you might have to go to a metal coupler to handle the brushless motor.
Also maybe the torque from the motor is helping to cause your roll?
I'm not sure of your set up but maybe turn-fins would help.

[martno1fan]

Why are you using a uv joint on a flex cable setup ? the whole idea of using a flex cable is to avoid using such things,get yourself a collet that fits onto the motor output shaft using grub screws ,the flex then pushes into the collet and its tightened up to hold it in place.Flex cables are flexable for a reason,means you can bend the tube to line up with the motor and vioala job done.
Mart
http://cgi.ebay.co.uk/steel-collet-1-8-motor-shaft-and-1-8-flex-cable-/300331822988?pt=Radio_Control_Vehicles&hash=item45ed2bef8c

[Drkomen86]

in all honesty I had one of them that I bought for it but it was the wrong size so I went down a different route.
This is my first scratch built boat and also my first flexi set up so all is new to me, but thank you for all the help 

[martno1fan]

Didnt mean to come across as a smart 4ss  ,good luck with it.You will def find it better using the collet once you find the right size  .

[w3bby]

A couple of pictures of the set up would help.  In the meantime;
1. What size boat?
2. What shaft size are you using?
3. What size stuffing tube?
4. What is the gap from stuffing tube to coupler?
5. What rpm are we talking about?
6. Is everything balanced, including the prop?
7. Which way does the boat flip, end over end, sideways or how?

I agree with Martin that you are introducing an unnecessary complication with the UJ. The flex shaft is exactly that, flexible and can be subject to whip. With the UJ in the loop it could well be causing your vibration and consequent destruction.

I can only assume you are running the boat at max speed for to long a period to make it randomly flip over, thats a common issue with fast boats is that to much speed will make them unstable in the water .

I cannot agree with this as it is all down to set up, too long is not a problem , too fast for the hulls capability can be as can too fast for the actual conditions.