Earlier, (BllFs6) wrote:

...Which brings me to my question.....if you
are doing homemade carbon fiber
layups...and you are reasonably
careful in its construction....what
kind of real world numbers can you
expect for strength and stiffness
per pound over aluminum?

Jim's comparisons between aluminum and carbon for strength and
stiffness per pound are the only ones I know of, although there must
be others. Jim's a great guy to talk with on this topic; he seems to
have lots and lots of practical experience with a wide variety of
materials and techniques.

Actually, now that I think on it, there are some carbon properties
results in the Test and Research section of the NTSB report on the
Minden Nimbus 4 crash (though not comparisons with aluminum):

http://www.ntsb.gov/publictn/2002/AAB0206.pdf

See pages 35 and 36. For reference, I believe that one MPa
(megaPascal) equals about 145 pounds per square inch. Note that those
properties are achieved by people with lots of experience and lots of
high-tech tooling, and who take their jobs pretty seriously.

Here's a couple of pictures of my Graphlite-strip based wing spar:

http://www.hpaircraft.com/hp-24/update_4_dec_02.htm

http://www.hpaircraft.com/hp-24/update_21_March_04.htm

As you can see in the photos, I also used Graphlite strips as
stiffeners in my wing plugs. But only to give them enough stiffness to
make them easy to handle without creasing their fiberglass skins.

Thanks, and best regards to all

Bob K.
http://www.hpaircraft.com/hp-24/