I can tell you that they make composite props for military applications that
include dirt strip transport planes ( I think some C130's are using MT's ).

A composite prop is not like a composite wing. What you see is what you
get. There is no wondering what stresses are going on inside anymore than
there is with a metal prop. Most dings can be fixed by filling up and
building up with epoxy, then sanding. If the ding meets a certain size,
then it has to be inspected by MT or someone specially trained.

Advantages of composite props are reduced weight and noise along with a
shock absorbing kind of flex. Disadvantages are that little dings that
would only scratch a metal prop will require epoxy repairs (but they are
easy and cheap repairs.

Given that most homebuilts will never fly enough hours to make a difference
in the maintenance costs, the MT is not a bad idea at all. Mine is smooth
and quiet, and I like it.



"x" wrote in message news:TcIac.45575$gA5.568680@attbi_s03...
"Corky Scott" wrote in message
...
On Wed, 31 Mar 2004 19:51:59 GMT, "x" wrote:

Anyone care to comment on using one of MT's composite blade props with
electric pitch control?

Eggenfellner seems to really want you to use this prop with his Subaru
setup.

I'm a bit concerned both with a composite prop and an electric pitch
control.


I don't think there's anything wrong with a properly made composite
prop, and MT is one of better known prop manufacturers. They make
LOTS of props, many of them for certified airplanes.

What's your specific concern?

Corky Scott

I don't know anything about using composite construction for a propeller.
I
do know a little about fiberglass and carbon fiber composite, just from an
"educated layman" point of view. So bearing that in mind, I would be
worried about:

1) Would continual flex/unflex cause fatigue and how would you detect it
if
it's internal? (I think in the research environment they basically CAT
scan
parts to look for internal fatigue?)
2) How could you tell a trivial rock ding from a potentially disastrous
one
(again, hard to see what's inside)?

Again, I'm not all all claiming these things happen, I just am asking if
people know of any gotchas. Of course, there are lots of testimonials
that
basically say "I've had mine for X years and it hasn't broken yet", but
that's not really data.

Secondly, does the electric system work automatically (so that you don't
do
anything), or is there a control that works like manifold pressure (i.e.
"governed" so that changes in RPM cause automatic changes in blade pitch),
or is there just a blade pitch control? Why would it be better/worse than
hydraulic?

Does anyone out there have one who can ring in on this?