Carbon Fiber or Fiber Glass

I'd say make a wooden model as your male, then cover this with (mold release first!) then glass fibre/resin to make the female mold which you will then use for the final item.

Take care to design in a split line so you can get the female off the male (stop sniggering at the back!) and also make sure it has enough reinforcemnt to keep its shape once off the male.

It's a lot of work. Maybe simpler to fabricate it the old fashioned way in wood/foam and suchlike then a thin layer of glass/carbon fibre cloth?

Thank you!

You don't mention the scale of this thing Felipe. If it's modest, as in 0.5-1.0m long you might not notice much difference whether you use glass or graphite as the reinforcement, in term sof function of process. I reckon you'd hardly notice the difference in cost either as the material for the hull is likely to be a pretty small contributor to the overall. On a bigger scale the mechanical properties vs weight migth start to become more significant. The carbon/graphite will give you a more robust (or lighter depending on thickness) end result. Youll be able to sink the competition without the need for torpedos.

my especialty is automotive repair, have used fiber glass extensively but not carbon fiber, however, I do know it is used to build light (competition) boats. I am not familiar with its shock absorption and rigidness properties.

I've no experience of using carbon fibre but whenever I've seen film of it being used to construct boats/cars/planes etc. it always required baking in an autoclave to cure the resin whereas fibre glass cures at room temperature.

That depends on the resin! If you buy 'pre-preg' or when buying a resin check the curing recommendations

Check out the Gougeon Brothers website. Gougeon, in Michigan, is a leader in composite boat building. Also, IBEX, will be held again this fall in Miami.

Bob

Just from a pragmatic point of view, I don't think you will notice much difference in weight, but with the current big two aircraft builder sucking up all the carbon fiber in the world, you will notice a big difference in the price of carbon fiber over fiber glass. G10 fiber glass is close to carbon fiber in performance. Just a thought.

Steve

Hey Felipe.

There are so many types of fiberglass that I would encourage you to do a little more research.

I Googled: "types of fiberglass" and had immediate success.

cr3

Try Fiberglast http://www.fibreglast.com/ they are a supplier of small quantities of composite materials. They sell DVDs of how to work with composites. They have a good one for how to make one off parts with out a mold.

There are many other suppliers of small qty of composites. you should do a web search.

Felipe,

I would make a mold using foam blocks. they can be glued together with superglue and cut with a hot knife ( 2 sticks and a heated resistive wire). add all structural ribs (pre fab using s-glass or car fi). If you can fabricate all ribs ahead of time. slice their home in the foam. by leaving the ends of the ribs without resin, it allows you to have an anchoring point to attach to the hull structure. It is possible to piece (making angle bracket and add and adhesive to mount. easier to construct, just takes longer. Lay your hull. let air cure at room temp if using a non pre-preg. then thermal cure usually under 200F. A cup of acetone in the hull should remove the foam and leave you with a lightweight structure.

When using CF orientation of fiber is critical to strength, s-glass not so much although rigidity is about half. s-glass is more forgiving. CF will splinter upon impact. for an RC a patch can be done. Find a good epoxy resin for either using polyester will not give you the best performance of the composite. Polyester resins usually require MEK (not so good).

Using orientation of CF to give best results. CF strands are best in tensile, then compression, and last in shear ( normal to strands, very bad). There are references you can use to create a strand orientation. It takes alot of forethought to use CF to take advantage of its strength and rigidity.

S- glass is cheaper. no worries about galvanic corrosion like with CF. glass is usually used where joints will meet with dissimilar materials to prevent this, acts as a buffer. Also allows forces to act across a larger area to help prevent stress points.

I would use s glass for a prototype unless you are comfortable enough using CF. Any changes can be made and incorporated into a revised design. A layer of twill weave CF can be laid over the hull to give a desired look of CF. Use a UV protective additive in resin or clear coat with polyurethane.

I now have a wider imagination to what kind of material I possibly can use. Thank You!

www.rcgroups.com has many forums on composite design/construction that will help you.

Use carbon to add stiffness with a minimal weight increase.

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