gas tank

Use klegecell foam and fiberglass resin.

This sounds like an interesting technique. Have you worked with klegecell? What are it's properties?

Thanks for the tip!

Klegecell is almost like "regular" styrofoam, but is fuel proof.
Easy to cut/sand/shape. Reinforce it with fiberglass cloth and polyester resin.
We make airplane fuel tanks with it, and it can be configured to almost any shape or size easily. It's not the cheapest, but there is no substitute. Look for at places like wicks or aircraftspruce.com

bikeguy joe thats awsome!

You can also use a method where you use klegacell, or other non reactive foam. (can't think of the type right off the top of my head, but they sell it at aircraftspruce.com)

Glue up a few pieces into a block, sand/shape it, then cover it with glass and resin. When you are done, pour some acetone in it to eat away the foam and you have a very light fuel tank that just needs a little putty on the outside for final finishing.

There are other types of resin as well, one is vinyl ester resin I believe.
Aircraft spruce specialties has an AWESOME free catalog that has a lot of good info on types of resin/foam/glues/ect ad nauseum.

you want to use vinyl ester or safety poxy resin some resins will be eaten by gas. I know this for a fact. Joe has it right on molding your tank lots of ways of doing it male or female molds or the mold less way.
Norman
Check out my fiberglass and wood home built airplane I built. VW powered goes 160mph straight and level will do over 200mph in a shallow dive. click on the link to see the plane do a over 200 mph pass on a video
Norman

I forgot to tell you. Some resins like polyester and vinylester will eat some of the foams so be sure you check to make sure they won't attack the foam your going to use.
Some foams like the beaded foam you can hot wire some foams you should not cut it with a hot wire and some you can't.
Some foams will put out poisonous fumes if you melt, burn, or try to hot wire cut them. The dust made from sanding them will also hurt like yell if you get the dust in your eyes so make sure before you start on this type of project you do the research to work with it safely.
Its lots of fun I think to create things with foam and fiberglass but its lots of work as well.
Aircraft spruce has good info in the catalog on what works with which types of foams and the proper chemicals to use along with the hazards that it can have. So get ready to get dirty!
Do be careful with it as some of the chemicals can eat your hide if you get careless might not happen right away but if you get allergic to it you will break out every time you mess with the uncured chemicals. I got allergic to the resins when I built my airplane and had some sore hands at the last building the wings. Had to stop let them heal up then go at it until they got sore again. At the time I couldn't sure a different chemical got stop my reaction that broke me out. Even now if I mess with that chemical I have to be every careful or I break out.
Norman

heres a tank shape to think about. it is as wide as the frame at the back and flares out to 10" at the front. http://motorbicycling.com/members/a...er-picture2489-yup-its-straight-pipe-i-am.jpg