On Mon, 19 Sep 2005 10:37:16 -0400, "Gordon Arnaut"
wrote:

Ron,

That's a good comparison. A Glasair or Lancair kit costs about double what a
Van's kit costs and it still takes about the same build time to complete. In
fact even the Van's quick-build costs less than a Glasair slow-build and you
get probably less than half the build time.

Ahhh... The Glasair takes a *lot* longer in build time. You are
looking at 4000 plus hours for a G-III or Super II.


And what if the Van's kit were designed to be built with pulled rivets? This
would cut build time dramatically and that slow-build kit could be built in
about the same time it takes to build one of the composite fast-build kits
that cost three times as much.

I think the Vans series are faster, more powerful, and more highly
stressed than the Zenith. It's kinda like apples and oranges.


Look at the Zenith 601, and compare its price to some of the sportplane
composite kits. The composte kits are usually twice as much money.

There are a few planes out there designed around the simplicity of
construction with build times on the order of 500 or so hours. OTOH I
understand the Jabaru has a relatively short build time and is a
combination of composite and metal.


The conclusion has to be that composites are more expensive because it costs
more to make them. No question about it, composite construction involves
lots of hands-on labor.

The way we do it now certainly takes a lot of labor. But the way the
parts are made, the individual lay-ups, there is a lot of room for
simplification (speeding up the construction). Even die cut foam for
the bulkheads and firewall would reduce the build time and increase
the accuracy.


Also composite materials are expensive compared to aluminum. So if there is
no advantage in labor costs and material costs are higher, how does
composite make sense for a cheap airplane? It doesn't.

Again, were we to use a couple layers of fiberglass over a steel tube
frame it would be much faster and easier and a lot cheaper than the
advanced composite. . When you get into the advanced composite using
layers of fiberglass, foam, more fiberglass and resin it can get
complicated and messy.

In addition, if you've ever worked with fiberglass cloth cut on the 45
degree bias the stuff is like working with a bucket full of worms. You
need an outline or form to which it needs to be fitted. Draw the
shape on the cloth, cut on the line and then when you wet it with
resin fit it to a shape where it goes. The stuff can easily change
length and width by as much as 30%. Of course when cut on the 90 or 0
bias the stuff has a tendency to come unraveled with loose threads all
over the place. On top of that the thickness varies. The leading
edge of the horizontal stab is made up of at least 6 layers of roughly
16 pieces. The are about 2 1/2 inches wide, various lengths, and the
ends are cut on a 45. Even with care a straight edge along the
leading edge shows many variations, so you fill and sand, fill and
sand, fill and sand...

Prepreg OTOH costs more, but the thickness is uniform, it uses a
minimum of resin, and holds its shape. It doesn't have that annoying
tendency to come unraveled either.

If you want expensive, the horizontal stab is constructed using foam
and carbon fiber. Look that stuff up by the cost per yard:-))


Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com

Regards,

Gordon.



"Ron Wanttaja" wrote in message
.. .
On Mon, 19 Sep 2005 03:47:38 -0400, Roger

wrote:

On Sun, 18 Sep 2005 23:37:30 -0400, "Gordon Arnaut"
wrote:

Evan,

I don't want to drag this out, I think some good points ahve been made --
however, I don't see why fiberglass airframe construction is going to be
less labor-intensive.

Once you have the moulds constructed, fiberglass lends itself well to
making large compound structures as one piece.

There is almost zero opportunity for automation in fiberglass
construction,

That depends on your thinking. Fiberglass composite also lends
itself well to putting pieces together.

I dunno, Roger. I've been both to the Glastar factory and the Vans
factory. At
Vans, a guy feeds a big piece of aluminum into a big CNC machine and
whango-whango-whango out comes a big pile of RV parts. But then I go see
the
Glastar's fiberglass fuselage made, and its spray the release agent onto
the
mold, then the gelcoat, then cut pieces of fiberglass and lay them into
the
mold, then squeegee on some resin, then apply the foam, then apply another
layer
of fiberglass and more resin, etc. etc., lather, rinse, repeat, then let
the
assembly tie up your every expensive mold while the resin cures.

Looked to me that manufacturing aircraft parts in fiberglass is a *lot*
more
effort...though I allow that less-skilled workers can probably be used.

Ron Wanttaja

P.S. Wanna hear something *really* scary? My spell checker passed
"whango-whango-whango" but hiccuped on "gelcoat."