Is Carbon Really Better?

[Wes K]

I have been reading around about Carbon Lay-up hulls vs Fiberglass, and everything I read says Fiberglass is better for taking hard hits over and over while Carbon is not because of it's stiffness it will not flex enough; thus break.

This is just what I have read on the internet, and just wanted to clarify.

Thankyou

 

[kevbo]

Our hulls put load most of the load on the resin instead of the fiber. This is where composites are weakest. Carbon weighs 50% less than glass and is slightly better in shear. So a carbon laminate is lighter and stronger for a given thickness, but is also very expensive. Hulls become too fragile when the builder trys to save too much weight and material cost, like they all do. When done properly the weight savings will cost around $100 per pound.

 

[Dustin Mustangs]

You are gonna be hard pressed to find quality info along these lines in a forum like this. The people that really know what they are talking about are tight lipped because this type of info is how they make their living. What ever info you do get you probably want to take with a grain of salt (not aimed at kevbo). My personal recommendation is to go down to your local library and see try to find this or something similar. I learned a TON from reading this book!

http://www.amazon.com/Fiberglass-Other-Composite-MaterialsHP1498-AutomotiveRacing/dp/1557884986/ref=pd_sim_b_2

 

[Waternut]

Our hulls put load most of the load on the resin instead of the fiber. This is where composites are weakest.

That's actually why carbon is so beneficial. It's stiffer or equal to the stiffness of the resin. Obviously, each manufacturer makes things different but generally speaking fiberglass has an elongation of 3% and carbon fiber has an elongation of 1.5%. Polyester resin is 1.5%, vinylester resin is 3% and epoxy is 5%. What this means is that carbon fiber and epoxy or a vinylester resin will be the best since the load is actually being put on the fibers which have the most strength. The problem is most hull makers use fiberglass and polyester because it's the cheapest and this puts the majority of the load on the resin and once the resin has stretched almost to its limit, then the fibers jump in and help out.

 

[WFO Speedracer]

Get some information from someone who knows what they are doing, thats my best advice.

 

[snowxr]

Many hull builders do not have the education/training/resourses to develop a layup that meets the structural needs of a hull. A hull, unlike a F1 car wing, must hold it's shape AND withstand impacts (a variety, which would be difficult to reproduce in a test).

Carbon is stronger than glass per weight. Make 2 hulls that weight the same from each, and the carbon hull will be stronger. BUT, that's not what the buyers are asking for. The demand is lighter weight. So, you can have a lighter carbon hull, that's the same strength (relatively) as fiberglass, but cannot handle the localized impacts that a thicker fiberglass hull could survive.

Just for referance, here's a hull I built over 10yrs ago. Full carbon 250Lbs. Sunk twice. punctured and repaired twice. Still kicking.

 

[Dustin Mustangs]

That's actually why carbon is so beneficial. It's stiffer or equal to the stiffness of the resin. Obviously, each manufacturer makes things different but generally speaking fiberglass has an elongation of 3% and carbon fiber has an elongation of 1.5%. Polyester resin is 1.5%, vinylester resin is 3% and epoxy is 5%. What this means is that carbon fiber and epoxy or a vinylester resin will be the best since the load is actually being put on the fibers which have the most strength. The problem is most hull makers use fiberglass and polyester because it's the cheapest and this puts the majority of the load on the resin and once the resin has stretched almost to its limit, then the fibers jump in and help out.

Tensile strength and stiffness is only half the story. Literally!

 

[kevbo]

Get some information from someone who knows what they are doing, thats my best advice.

Or spend a few years breaking test specimens for a defense contractor.