fiber glass is resin and hardener combined with cloth,the glasscloth is the shape the resin and harder strengthens the glass and keeps the shape.
you need some thing to copy the shape from,example an existing seat or tank or body panel.
lacking something already existing...you would then have to make your own "Mock up" or "Buck" as its called which is ussually made of clay or urethane foam shaped to what you want a seat or tank or what ever.can be made from anything that represents the shape.except styrofoam it will melt it.you need urethane foam.
you can get creative and meld to existing shapes together to come up with your own ...only your imagination limits shapes that can be done in glass.also carbon doesnt like taking shape as easily as glass cloth ..but when you read what carbon is for and the properties of glass you can make a better choice of materials.
you ussually make the mould from this,shape you have to copy, which is the reason fiber glass takes so much time.
You need to make a mould of what your making ,some times the mold or mould needs to be made in more then one piece depending on the shape your forming.
After you make a mould and its plenty of work, you then lay up gelcoat,which is the color finish you see ..let that dry for 24hrs or over night then you spray or brush in resin then lay in the cloth either fiber glass or carbon fiber ( this stuff is tuff and needs special tools to cut it to size and to trim).carbon fiber is about ten times cost of regular fiber glass .what you normally see is not true carbon fiber but carbon vener.
you have to apply a few layers of this,cloth resin combination, called the schedule.wait a few days for this to dry before taking out of mould wallah!!!
after weeks and weeks of work a part is made.
so unless your making a unussual part or planning on selling them its best to buy one,made.
never one to discourage anyone read here for EVERY THING YOU NEED TO KNOW.
and what they dont tell you is its itchy drippy messy stuff it smells and isnt good for a long life to breath.
here is the best company to start and buy stuff from they sell small and large quantities of glass and resin and gelcoat and teach you everything about glass and carbon fiber
actually carbon is very easy to cut dry. it is kinda pricy. $35 bucks a yard and up. you need to determine what you are trying to build. if you have a part or a plug... build a mold. make sure the part/plug is real pretty since the surface will be transferred to the mold surface and back to the part. bla bla bla i could go on for days about this but i wont since i have been in the industry for 8 years.
kevlar is difficult to cut dry, wet, cured.... carbon on the other hand is vey easy to cut , shape, grind etc
I have discovered that by far the easiest, most cost effective way for most people to obtain what they need in glass/CF is to have someone that knows what they are doing ( like Matt )....make it for them. Yes a fuel tank will cost you $350-400..... in the long run...way cheaper that the nightmare it becomes trying to do it right yourself.
Learned my lesson.....and the cheaper the part...ie belly pans etc....it my opinion it becomes even MORE cost effective to have it done by a professional.