Hi Peter

Reversing polarity on motors does not always work with brush motor as some rev faster one way than the other.

Brushless motor rev the same both ways and to reverse them I swap the two outer wires over.

The torque from the props can cause the boat to roll over sideways!!

I see a Fantome (which is a very large boat) do is.

Every type of boat is a bit different in setting up, so it's down to a lot of testing.

Harry Smith

It's not something to worry about Peter. Thousands of models have been built with twin brushed motors over the years, and as Ashley says the differences are minimal. I've never had do do more than tweak the rudder, and that's with fast scale and sedate models. If, like Harry you're making a very fast boat that runs near its limits, that's another matter, but I presume you're not, so go ahead and just reverse the motor connections on one motor.

The most common reason to have contra rotating props on a model, is so that the turning circle is more even in each direction, the amount of difference varies between types of boat / ship. There are other reasons but I'm not opening that can of worms when you just need a straightforward answer.

Out of interest, what model are you building?

Chas.

The real boats actually ran in the same direction, surprisingly , perhaps.

I wonder how they handled in a turn.

Martin

The real boats were probably fitted with twin identical motors which may have only run in one direction with a geared drive for reverse. If the props were relatively small there may not have been much of a tendency to turn in one particular direction while at high speed and at lower speeds it could be easily compensated for with the rudder(s) and even taken advantage of when berthing/unberthing the boat as is the case with moderm sailing yachts.

There may certainly have been a slight difference in the turning circles between port and starboard but again, probably not enough to matter.

It's nice to have symmetry but not essential.

Colin