Can anyone comment on which manufacturers use "sandwich" construction
in the fuselage and which ones don't? I'm particularly interested in
the LS ships, but I'm also curious about what others are doing or have
done.

Tough question. My take on it is:

It's not going to break down well by manufacturer, or even by model.
In then production lives of all ships there will be minor changes,
including the starting or discontinuing of sandwich construction in
various models.

Most composite ships I've seen inside out have sandwich construction
in the vertical fin. That stands to reason, it's usually a ruled
surface that's easy to core and which gains a lot of panel stiffness
with a little bit of foam. Some ships have virtually no sandwich
construction anywhere in the fuselage, including the vertical fin. I
think that most ASW 20 fall into this category.

In my own fuselages I only have sandwich construction in the vertical
fin, with the builder adding sandwich stiffeners under the cockpit
rail and also at the skidmark patch of the fuselage belly under the
pilot's butt.

The only glider fuselages I've seen with all-over sandwich
construction are the Russia AC4 and AC5, and the ASC American Spirit
and American Falcon kit gliders. The Russias have tiny wings, and as a
consequence require very low gross weight to climb well. The sandwich
fuselage helps keep the fuselage weight down, but makes the
construction so light that crashworthiness seems to suffer somewhat.
For the ASC ships, I don't know the rationale for full-sandwich
construction, except perhaps it made those huge shells stiffer and
easier to handle until bonded together.

I've hear that some manufacturers have include sandwich stiffeners in
key areas such as near the aft lift tube carrythroughs, but I've seen
relatively little of this in the crashed gliders I've picked through.
But that's mostly due to the selection process itself; I've had
precious little opportunity to inspect crashed high-end gliders such
as Duo Discus, DG1000, and ASH25. WIth luck, few such opportunities
will present themselves.

Thanks, Bob K.
http://www.hpaircraft.com