Archive-URL: http://search.bikelist.org/getmsg.asp?Filename=tandem.10310.0502.eml
Date: Wed, 22 Oct 2003 09:58:26 -0700 (PDT)
From: SANTANAINC(AT)aol.com
Subject: [T(AT)H] CARBON De-mystified

Part 2 of a post from Bill at Santana. 

In order to understand some distinctions between the Beyond and frames that 
appear similar, here are nine salient differences

First, in the process of being pressure-cured, carbon fiber tubing gets a 
controlled (smooth) side formed against an impermeable mandrel or mold, and an 
uncontrolled (uneven) side that results when gasses and voids are flushed out. 
With the standard method, the carbon is cured while sandwiched between a solid 
mandrel and heat-shrink tape. When the tape comes off a rough exterior 
remains. A more expensive way to produce tubes is "inside out" or "molded" 
construction where carbon is wrapped around an inflatable mandrel and 
locked in a solid 
cavity. In this case the carbon is cured within a high-pressure and 
high-temperature mold---very similar to the method used by Reynolds to 
build our 500g 
Ouzo-Pro carbon tandem fork. Because the rough outer plies of a cheaper 
mandrel-wrapped tube must be partially destroyed (ground away) in order to 
produce a 
uniform exterior, a molded tube with the same weight and diameter can test 20% 
stronger. While many of the best framesets now include molded carbon forks and 
stays, Santana and Titus are, as yet, the only builders using molded frame 
tubes.

Second, a molded tube allows advanced geometric shapes. While Ben Serotta, 
for instance, clearly understands the importance of an externally-tapered 
downtube (a concept he pioneered 15 years ago), his carbon composite 
frames can't 
incorporate this advantage. Because of proprietary molds, Santana's Beyond not 
only includes a Serotta-inspired tapered downtube, it's the first carbon 
tandem 
with an oval bottom tube.

Third, the inflatable mandrel allows a carbon tube to be internally 
double-butted. Frames built from double butted tubing (no matter what the 
material) can 
be 25% lighter without increased risk of failure. In addition to being 
lighter and/or stronger, a double butted frame is also more comfortable. 
Double 
butted carbon tubes are another Santana/Titus exclusive.

Fourth, in addition to internal butting near the ends of each tube, the 
inflatable mandrel also allows added internal layers of unidirectional 
"stripes" of 
carbon at the right and left edges of our tubes. These thickened edges 
provide greater lateral stiffness while damping out vertical harshness. No 
other 
bicycle frame tubes (in any material) share this feature that is exclusive to 
Santana.

Fifth, the largest advantage of our molded tubing is IsoGrid --- a skeleton 
of Kevlar-wrapped carbon that is affixed to the mandrel before the other 
layers. The resulting tube with its internal lattice is not unlike an 
airplane's 
fuselage---where the thin skin is supported by an underlying network of 
supporting ribs. In the case of an IsoGrid tube, however, the application 
of heat and 
pressure permanently bonds the Kevlar/carbon ribs to the carbon skin.

Sixth, just as metals come in different gauges; sheets of carbon come in 
different ply weights. The thinnest plies, made from finer strands, can be 
built 
into tougher and lighter tubes. Further, additional layers allow a wider range 
of tuneability. Over 95% of the carbon sheeting used by the bicycle industry 
is "150" or higher FAW (Fiber Arial Weight). A very few items, including 
Reynolds' Ouzo Pro tandem fork, use super-premium 120 FAW carbon. Our 
Beyond uses 
ultra-exotic 90 FAW. The downside of thinner plies? Each sheet is more 
expensive 
and a higher number of plies means increased labor to produce the tube. Where 
else can you buy frames built with 90 FAW? Good question!

Seventh, just as "metal" includes a wide family of materials with various 
properties, "carbon" describes a range of complex hydrocarbons. Most 
carbons used 
in the bicycle industry are standard modulus---considerably less expensive 
than titanium. A few companies use intermediate modulus --- as expensive as 
titanium. High modulus carbons are exceptionally rare, and are too 
expensive for 
bicycle frames. But because the stiffness difference between standard and high 
modulus is a whopping 48%, Santana has decided to break the rules.
 
Eighth, just before the numerous layers of Kevlar/carbon IsoGrid ribs, 
unidirectional edge strands, butting plies and 90 FAW high modulus carbon 
are placed 
into the mold, a short section of thinwall titanium tubing is slid part way 
onto each extreme end. During the high temperature and high pressure molding 
process these titanium ends become permanently fused to the carbon. The 
resulting Bi/Fusion tube is all-carbon except for the short titanium tips.

Note: While IsoGrid and Bi/Fusion are independent technologies (that are 
owned, registered and patented by VyaTek Sports---www.vyatek.com), the 
tubes used 
by Santana and Titus are IsoGrid AND Bi/Fusion. In short, IsoGrid makes a 
carbon tube stronger and more damage resistant; Bi/Fusion makes a carbon tube 
weldable.

Ninth, to produce similar looking frames Merlin and Serotta glue carbon tubes 
into pre-welded titanium lugs. At the Santana and Titus workshops, there are 
no pots of glue. Instead, the Bi/Fusion tubes are mitered, and TIG-welded 
directly to each other. Because TIG joints are both stronger and lighter than 
glued joints, the process used by Titus and Santana is superior. Think of 
it this 
way: while glued-together aluminum frames were popular 15-20 years ago (Vitus, 
Alan, Trek, and many others), these heavier and/or weaker frames are no 
longer being produced.

Summary. While tandem buyers will naturally want to compare our new carbon 
Beyond with previous exotic frames built by Santana, Seven and Calfee, the 
numerous advantages of IsoGrid and Bi/Fusion technologies are undeniable.

For instance, when weighed on an accurate scale the Beyond frame is at least 
15% lighter than the lightest previous carbon frames and 20% lighter than our 
titanium frames. When stressed on a precision testing jig the Beyond is 
stiffer than the stiffest frames built from steel or aluminum. And beneath our 
testers' delicate derrieres, the Beyond is supremely comfortable---most 
have rated 
it "twice as comfortable" as the tandem they currently own.

Mark again: "Very cool technology but I'm still waiting to see the cost..."

My reply: $9695 will get you a uniquely efficient and comfortable sub-30 
pound tandem with a lifetime frame warranty and proven components. Gram 
shavers 
and competitors will be able to wring out an additional five pounds. 
Either way, 
you cannot buy a faster and lighter tandem at any price.

Bill McCready

PS: Because tandeming is a reliable indicator of an evolved lifestyle, 
spending more signifies advanced intelligence.

PPS: Your neighbors already think you're crazy. Why not confirm it!