From Cervelo web site:

The Myth of Modulus - Cervélo

Design and implementation also make a big difference. Case in point from the Fairwheels study is the single bike Specialized S-Works carbon cranks which appear to be very similar to Lightning cranks (Specialized licensed the hirth hitch axle design from Lightning), but the S-Works are a fair bit stiffer. Spider alignment and bearings are also very different between these mfr.

I did. The stiffness to weight data I posted is from an independent source.

It's a fact that on a per pound basis CF is stiffer than Ti. Given that the source I cited is 1992, it's likely the difference has only gotten greater in in the last 23 years, as CF layup techniques have gotten better.

Nobody's building truly lightweight single bikes out of Ti. (other than Litespeed's failed experiment with the Ghisallo) According to Eriksen, their Ti single weighs "about 3lbs". Why would you expect that to be different for a tandem?

And as for not being able to manage the layup in tubed construction. ENVE makes the tubset specifically for Calfee. I doubt that they're just slappin on the fabric willy nilly.

And fwiw, I think Ti is a great choice for a bike with couplers with which you're going to travel, just not the stiffest and lightest.

I believe that carbon does allow for more customization in theory. With layup changes one should be able to get a wide variety of results including what i have heard called "black aluminum" This is carbon laid up to be strong in every direction. It takes so much material that the end product is a carbon part about the same weight as aluminum. This is why carbon stems and seatposts do not save a lot of weight compared to high quality aluminum products.

I wonder how many options there are however in Calfee tandems. How many tubesets did you have to choose from? Is it just regular and extra stiff? I am really interested in the answer.

I agree with Merlin that for the ultimate in light weight and stiffness carbon is the way to go. On the other hand for me that is not the only two criteria. I believe many people who unlike merlin do not race seriously should consider other factors.

There are things in the Calfee design that I don't like. These things are not bad but just not for me. Just an example, our current top tube is 32mm in diameter and any my stoker nearly rubs it when pedaling. The Calfee fat carbon top tube is a non-starter for us. I have to admit looking at a well built Ti bike makes me drool. Calfee wrapped joints, not so much. There are other things on that list but I don't want it to look like I am dumping on Calfee. They are very good tandems but I would never pay the price for any that I have seen.

I will mention cost because it is not mentioned much in this or other threads but it is there and it is real factor that should be considered. Just because I can spend $10,000 on a frame does not mean I want to or that it is wise of me to do so.

Everyone should decide want they think is important to them (not everybody else) and pick the bike accordingly.

I completely agree with your information on the stiffness to weight ratio of the various materials. It is also a fact that along the optimal direction, carbon is stronger and stiffer than any metal. That is independently verifiable. Off angle from the fiber direction, however, cf is much weaker. Compare the breaking point of a flat plate of cf versus a flat plate of metal at 90 degree for example.

Also, you cannot extrapolate data on base material to the final product. That is like saying all carbon fiber bikes are light and stiff and all metal bikes are heavy. Like the cranks in the previous post, how each materials were used has a lot to do with the final outcome.

Layering carbon around a hollow tube that ENVE makes, for example, can only be done a few ways. Willy nilly or not, you can only orient your fibers along or around the tubes. On a single bike, the irregular shape and form of the frame helps mold the orientation of the fibers for the optimal stiffness and strength where it is needed. So less material is used where it is not needed for lightness. The lightest and stiffest single bikes are never based on round tubes. That would be no better than using round metal tubes.

Calfee use of the round tubes does not make optimal use of the material. Commercially they are very successful at it. I just don't have objective data to show how successful they are implementing their claims, neither does anyone else for that matter.

If it seems like I am dumping on carbon fiber bikes, Calfee, or Lightning cranks, I really am not. I do own and ride both carbon fiber and titanium bikes as well as steel and aluminum. I have a few friends who love their Calfees (which I personally think are beautiful bikes.) And, I have the Lightning cranks on my own tandem.

But if you're going to claim one bike is better than another, my response is: prove it.

If there is one thing I have learned in 40 years of cycling is that riding a bike is sensation, perception, feeling, and passion. None of these are provable they are just part of the experience.
Of course science can and does play a part in the materials and design of a bicycle frame, but what it comes down to is do you enjoy riding the bike.
It may be that Calfee doesn't take full advantage of the carbon fiber process, but what they do IMO is make the best riding tandem available today.
It is light, it doesn't flex when we ride it, It has the smoothest ride of any bike I have have ever ridden and it looks great. There is your proof.
I also think it is possible that the round carbon tubes that Calfee and others use maybe have in some ways superior properties over monocoque frames made in Asia.
The tubes are made in the USA and possibly with better materials and processes. It wasn't that long ago that some the best single bikes were tube and lug construction (think Colnago and Time).
I think what made in Asia monocoque frames get you is a lighter frame that can be mass produced and sold at a price point.
I owned such a frame, it was a Specialized Tarmac SL3. It was a very stiff fast bike, but it beat me up on rough roads. My perception was I wasn't enjoying the ride so much.
So I bought a different frame that was still a made in Asia monocoque frame and it is still very stiff but I enjoy the ride much more.
Tour magazine (based in Germany) does detailed scientific measurements on well known bike frames. These measurements includes things like how stiff the frame is in different places and how compliant it is in other places leading to predictions of ride comfort. You could call this proof but I think to buy a bike based on this is a huge mistake because it will not tell you which bike you will enjoy riding the most.

And I don't mean to be dumping on Ti bikes. (I own a ti single with S&S couplers). There is more to a bike than weight and stiffness. Ride quality, build quality, durability, aesthetics, all go into the equation. I just think that Ti is at a disadvantage on the two specific criteria I mentioned, which may or may not be relevant to a particular application.

Jnbrown,
I think we have the same point of view.

Merlin,
I do respect and value your opinion.
It is just the critical scientist in me that always question and request evidence for presumed "truths".
In the tandem world there are of course very little data.
The only information we have comes from the manufacturers and each other's experience.
I guess the best we can hope for is to have someone objectively ride all similarly equipped bikes and give us a comparison.
Until then, enjoy your ride.
CJ

Seven and Merlin come to mind as far as ti bikes.

Discs on a tandem make sense. The added weight alone not to mention the reduced wear on pads due to superior stopping power. Just imagine a long descent that could potentially eat a pair of normal pads.
At one point my downhill bike was about 54lbs, having quality discs makes a difference. Especially if you get caught in the rain. My downhill bike is about 38 lbs now but she still stops on a dime!

Seven and Merlin come to mind as far as ti bikes.

Discs on a tandem make sense. The added weight alone not to mention the reduced wear on pads due to superior stopping power. Just imagine a long descent that could potentially eat a pair of normal pads.
At one point my downhill bike was about 54lbs, having quality discs makes a difference. Especially if you get caught in the rain. My downhill bike is about 38 lbs now but she still stops on a dime!

Slightly off topic here but has anyone gone from a tandem with V-brakes to one with caliper brakes? Do they stop as well?

Yes and I prefer the caliper brakes.

For the record.
1st bike had Avid v brake front
2nd bike had Dura Ace caliper front
Both bikes had an Avid BB7 Rear.

Our previous tandem had V-Brakes, hated them always squealing and would grab causing unexpected lurching.

New tandem has Mavic SSC caliper brakes, no problems. If i was going to build up a new bike today would probably go with Dura Ace brakes.

How well do Ultegra (for instance) calipers STOP compared to V-Brakes?

We have Dura Ace 7800 brakes on our tandem, I initially built it with Ultegra and upgraded to DA. Our old tandem had canti's and the calipers stop as well as if not better than them. If I was building a new tandem and was concerned about brakes, I would go with DA 9000 calipers and a new internal shoe brake for use as a drag brake. The Santana article on disc vs rim brakes is excellent. I have always been of the persuasion that the rim brake is in effect a large disc.

^ I like our 622mm discs.

There is very very little reason to choose DA 9000 calipers over Ultegra 6800 calipers. I have both and IMO both are super strong and greatly outperform all of Shimano's earlier models including DA 7800 and Ultegra 6700.

While rims are indeed a big disc, a pivotal decision concerning caliper type (disc vs rim brake) needs to be determined regarding rim material (carbon vs alloy) plus anticipated terrain usage.