How are boats made to be bigger and faster?

Depends on sailboating or motorboating

1. increase their size , decrease weight without destablizing the boat due to windsheer/airpressure/waterpressure.

Increasing size for sailboats allows a boat to handle greater windspeeds without capsizing (idealy, all boats have limits based on their size).

Increasing size and weight for a motorboat allows the boat to handle drag created by airpressure and the fuel is what gives a motorboat thrust.

All fast boats have 2 things in common just like aircraft

their really either huge and or weight alot. raceboats have to be heavier to handle windsheer drag created by airpressure. speedboats are big metal behmoths.

Sailboats that are bigger have more sails and can handle alot of wind easier making them go faster. Thier is a direct correlation in boats and planes with size. In fact you cant name any boats or planes that don't weight very much or arent huge metal beasts with large amounts of fuel supply other than a hanglider, wich doesnt go very fast. The spaceshuttle and sr-71 for instance are huge planes.

In a race between a 30 foot schooner saildboat and a dingy with a sail on it, the bigger boat will always win when both travel at their top windspeed, however the only time a small boat may overcome a big one is if their is less wind that cannot give the bigger boat lift, both at top maximum windspeed however, big wins everytime.

2. add lift to reduce drag. things in the air are much faster than things in the water due to lack of drag produced by waterpressure.

3. add heat to reduce foreward drag caused by air pressure and waterpressure. (pref in the forward part of the plane/boat as the bottom will cause the ship to sink like a stone).

Another reason why size is a factor is fire created by friction, a small craft wont survive high speeds due to friction, it will melt or disentigrate do to the amount of heat and or windforce needed to propel it as well as the effects of high speed friction, a bigger boat/plane will survive friction effects longer and handle airpressure/waterpressure.