I very recently purchased a new 2004 Trek carbon bike – in the “nude carbon” color. I love the bike – all Dura-Ace – no complaints at all. Maybe.

Does anyone know what the nude carbon should look like? Basically my bike is black with grey and white trim. My wife wonders if the “splotchy” look is normal. I had just assumed that’s the way it’s supposed to look, but she thinks otherwise. To me, if it weren’t for this sort of sanded appearance, it would simply be a black bike.

Anyway, I thought I would get some input before making a fool of myself by complaining about the “paint job”.

Yep, yours is normal for an 04.

I'd cover up is I were you ::blushing::

Most "nude" carbons should look like a fine checkered pattern. It's the most common way to weave the fibers. Got a close-up picture showing what you're talking about?

I have a nude carbon bike. There are parts of it that have that checkerboard pattern to it, and there are other parts that look splotchy (to use the original poster's original description). It's just how the manufacturer put the various layers together. I imagine the splotchy areas just indicate that virtually all of the carbon fibers are running in one direction

the splotchiness is the different thickness of resin. Racing sailboats use carbon fiber too and in some areas the resins are just thicker.

I think the word for the "splotchy" CF is "prepeg". essentially, the fibers are on a big spool (think of a loom for fabric, lots of strands running parallel) and they go through an assembly line type of process where resin is applied, then dried, and rolled into big rolls, generally kept frozen so that the resin doesn't cure. the manufacturer then just takes the sheets from the rolls, thaws them, then uses a heat gun type of device to cure the resin fully. there was a good picture of the process in my materials textbook, if I still had it I'd scan it.

The result is not a pretty carbon weave. instead, you get an ugly looking finish. generally, when you see that weave, it is not structural, it is there to look pretty and have a nice CF appearance. I suppose the "nude carbon" is just missing the cosmetic layer of "weave".

them there cranks, I 'reckon

(I had doubted merton's texanity before this)

Are they "nude?"

If not, then the final (really the first) layer was gel coat that can be made to look any color... such boats which are typically white, or truck shells which can be almost anycolor. The gel coat has no structural strength, but is simply a color layer. In fact if I remember correctly the resin has no structural strength either... it is the fibers that do all the work, and the resin simply is the binding for the fibers.

The difference in the looks is determined by whether the top layer is unidirectional fibers (common to the pre 2005 Treks- aka splotchy) or if the top layer is of a woven material- the checkerboard. Its not true that a woven top layer is "cosmetic". The woven material provides a more isotropic final layer, providing strength in mutliple directions. This is often doen to better absorb imapct.

It all just depends on what the engineers were trying to achieve in terms of fiber orientation for the outside layer. There are tradeoffs for every combination of fiber orientations. The outside layer may or may not reflect what is beneath it.