View Full Version : S glass

04-16-2013, 11:57 AM
The design of the Joel White 23 I am building calls for S fiberglass for covering the veneer on the centerboard and rudder. The only thing I have been able to learn about S glass is that it is 20 percent stronger than "regular". Here is my question: Has carbon fiber replaced S glass in high strength situations? Is carbon fiber cloth any more difficult to work with than fiberglass? Thanks for all insights.

Cuyahoga Chuck
04-16-2013, 12:44 PM
Don't be one of those that thinks a more highly regarded fiber is better in every way than what had come before. Each fiber has it's downsides.
A lot of boaters are playing with CF(those that can afford it) not knowing whether or not they are getting anything for their money. The folks who make CF components for race cars and GP motorcycles are skilled technicians who adhere to a lot of engineering technicalities like which way to orient the weave to get the strength and stiffness required. If you are laminating over plywood you probably don't need any more stiffness but you might need additional strength around the mountings, encapsulation to keep the wood dry and abrasion resistence. So unless you or somebody else has the background to be able to compare the engineering factors like tensile strength, the various moduluses and any other pertinent qualities I would say save your money.

04-16-2013, 12:57 PM
Carbon fiber though stronger is also more brittle. I'd stick with the S glass.

04-16-2013, 01:49 PM

In production FG boats, I typically see it used as a lamination layer in conjunction with other reinforcements. For instance biax glass stringers capped with a carbon fiber; or a uni-directional layer of carbon fibers used in a glass radar arch. The carbon provides the stiffness, combined with the toughness, flex, tensile or other quality provided by the other material its laid up with.

The only place I can think of it being used by itself--outlandish racing machines with unlimited budget not counted--is for small parts under little stress like gauge panels.


Old Frog
04-16-2013, 08:06 PM
Graphite (CF) would not be a particularly wise choice in that application. IMHO, it would be a waste of money as, in that application, you would not benefit from its positive properites, probably would experience some of its negatives, and its properities would are significantly different than the substrate. So why bothger & spend the money? S glass is a fine use in that application. Spectra, might also be a good choice but probably not worth the bother to track down unless you have ready access to it.

04-16-2013, 09:07 PM
I'd just use E glass (the ordinary stuff) one weight heavier.

That said, I used carbon in Damfino's daggerboard. There a fair bit of uni for bending strength and the sheathing is DB for torsional stiffness so it won't hum.
As the board hasn't broken or hummed, I don't know whether this was excessive.

Read your PM.

Hugh Conway
04-16-2013, 10:22 PM
Carbon's much more expensive, harder to cut.

Todd D
04-17-2013, 08:46 AM
Actually carbon is really easy to cut compared to S- or e-glass. Carbon is also MUCH harder to wet out properly than normal glass. Unless you really need the extra stiffness it would be a waste of money to use carbon.

04-24-2013, 09:53 AM
Many thanks to all who responded. I have decided to use the S glass. We'll see how it goes.

Dan McCosh
04-24-2013, 10:31 AM
In a laminate with a wood core, glass fibers have such a high tensile strength, high-tech fibers would make little difference. The composite depends on the orientation of the fibers and their bonding to the substrate. S glass is a higher-tensile fiberglass, but the fiber orientation would be far more important than the fiber strength. Carbon fiber is extremely high-tensile, but as a result, tends to delaminate easily, is difficult to work with, etc.