I have heard the Rainsong guitars, and I'm not impressed. The problem with
them seems to be that so much carbon fiber is required to resist the torque
of the bridge on the top that they are too stiff acoustically, and 'way too
heavy. The sound ends up being 'thin' and soft, although I'm told they
amplify well. Much the same is true, IMHO, of the Ovation guitars, because
the back is 'dead'. The long and short of it is that fiberglass or carbon
fiber don't seem to be to well adapted for guitar use.
The harp, on the other hand, seems a perfect candidate. Both carbon fiber and
fiberglass are really good in tension, and gain a lot of stiffness when made
in curved sections. Conic shells are a snap with composites, and end up being
very strong and light; several people have commented on the lightness of the
'60's vintage 'glass bodied harps. A carbon fiber soundboard could be molded
in one piece that would curve around the edge of the body; instant rub rails!
Because of the string tension the edges of the soundboard would tend to grip
the body sides, and this could be taken advantage of in the design; properly
done it would almost snap on and not be relying on the glue joint for
strength. The pillar is a piece of cake; carbon skins over plastic honeycomb
spring to mind. The main problem would probably be in the arm; taper pin
tuners only really work well in wood. If folks were willing to go to a sort
of Paraguayan setup it would be easy; the structure would be much like the
pillar. Alternatively, planetary gear tuners could be used; let's see, 36 @
$25 is...
Aside from weather resistance, several advantages present themselves. One is
stability, both in terms of weather changes and over time. The carbon
soundboard would pull up to a certain point and then stop. I imagine the
weight would be about half of a 'normal' harp. Cracks., etc., would be a
thing of the past as long as you didn't drop it out of a fourth floor window.
Extended soundboards would also be easy.
On the down side; you would not get to look at all that gorgeous wood.
"Black, black, black, is the color..." The concert folks would feel right at
home.
I would think that the sound would not be a problem. The carbon fiber layup
could be oriented to provide the proper stiffness with minimum weight, and
the damping factor of carbon fiber is really low. I would expect it to be
pretty loud, and full, with good clarity, if properly designed.
The cost of such a beast would not be low. Tooling would be a factor; the
best way to lay up carbon fiber is using heat cured pre-preg, which requires
a steel form. Hand layups are also the rule. Rainsong says that their guitars
take twice as long to make as wood ones, and I believe it. A concert version
would certainly be in the same range as what is currently seen, and 'folk'
types might be more expensive than their current counterparts. On the other
hand, You would end up with a maintenance-free harp (except for the strings
and sharps) that could be passed on to your great-greats. Something to think
about...
BTW, I saw an article (in "Popular Science"?) some years back about a fellow
who made a full-sized harp of scrap aluminum. It was said to sound great.
Cold to handle, though. There is a copper Church Bass in the Boston Museum of
Fine Arts; sounds 'tinny', I'm told.