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what material should be used to make a model boat? Answered

we hv made boat of aluminium but it is not sailing in straight direction
wat to do plz help
also what type of shaft should be use for solar  motor C (its pin is .8mm)



You could fit a rudder, or keel fins.
Use a shaft that works for you.


your sailing boat is not travelling in straight line because the wind deflects'/ pushes it away from the course. in practice you compensate with the rudder in order to maintain desired course.   

If the boat is not sailing straight, it is extremely unlikely that the problem is being caused by the material the boat is made from. More likely, either the hull is out of balance or your rudder isn't trimmed to center properly.
I have no idea what you mean by the second part of your question. Use a shaft that fitsonto your motor and is of the proper length.