r/c pt boat problems, please help .

[Guest]

today i tried my model r/c model pt boat on the water for the first time.

i was very impressed with it as it sat perfectly in the water and cruised very well at slow speeds but on high speed or full throttle the boat tilted in the water as if it was going to roll.

does anyone no any possible causes for this ?

the model is 31'' long (1/32nd scale) and has a 540 35 turn motor with direct drive and a p45 2 blade prop

the model i have built can be viewed here The ELCO PT boat scale electric model boat

i have followed the build perfectle apart from making the motor direct drive and i have finished the hull with sanding sealer rather than tissue.

and suggestions are very greatfull.

thanks in advance

mark

[Guest]

Hi mark, this sounds very much like prop reaction, quite often experiencesd in fast models. It is simply the model trying to obey Newtons law and move in an opposite direction to the rotation of the propeller. Check your prop rotation and I suspect the model will be tilting in the opposite direction.

On real boats they fit trim tabs to the transom to counteract this effect which generate a slight lift to counterbalance the torque reaction but on a scale model such as this they would look out of place.

I tend to think though that a 540 motor might just be a bit too powerful and this is what is causing the effect in your model. I would go for a slightly smaller motor and see how the model performs with that and you might find you have to sacrifice a bit of performance for the sake of sorting it out.

You could also play around with props and see if you can improve it. A finer pitch would help as would a smaller diameter, again at the expense of performance but that might be a better way. Don't forget though that you want the model to be moving at a roughly scale speed and I strongly suspect that you have a model flying across the water here at well over scale. If it was me I would slow down the PT boat to a scale speed and enjoy it and buy a specially designed speed boat for the really fast buzz. They are designed for it and can even be fitted with trim tabs.

[Guest]

Agreed, that sounds like a torque effect of the motor spinning at higher revs.

[Ian M]

Looks like Richard got that covered. It also explains why the kit had a drive reduction in it.

A third option is to remove the motor and fit it out with two motors, rotating in opposite directions. Not the simplest of jobs agreed!

Ian M

[Guest]

hi there

thanks for all that info there .

upon speaking to allan from astec models yesterday he also agreed that i should go from a p45 prop down to a p35 prop and no bigger, my problem being exactly as you mentioned , the direct drive. , at the time i thauhgt the reduction gears wernt really needed and i when for the direct option. now i know why glynn guest used the gears !

as you mentioned bunkerbarge , the model is way over scale speed but been my first model boat , i think i got a bit exceited thinking about performance rather than realism.

thanks again for the help.