my ignorance

I've been reading every post here for a few weeks. I am absolutely amazed by
the amount of knowledge that lives here!
With the butt kissing done, I hope you'll excuse my ignorance.

I was interested in the discussion concerning the weight of different prop
materials. Has anybody tried to make a hollow aluminum prop? What about
titanium? Carbon fiber?

What kind of testing needs to be done on a home built prop?
Are there prop styles that can be copied without patent infringements?

Has anybody tried making a flexible prop? My thinking is that it might be
possible to create a prop with a low angle of attack for high power take
offs, then have it flex to a higher angle of attack as the load decreases.
Could something like that give the performance of a constant speed prop
without the complexity and added weight?

If I were to play around with different prop designs, is there somebody
around here with the knowledge and time that might be willing to test them
for me?
--
"Don't be misled, bad company corrupts good character."
www.LCTPaintball.com
www.LCTProducts.com

"LCT Paintball" wrote in message

With the butt kissing done, I hope you'll excuse my ignorance.

That is some first class "butt kissing." g

I don't have many answers, but I'll answer what I think I know, since no one
else has answered.

I was interested in the discussion concerning the weight of different prop
materials. Has anybody tried to make a hollow aluminum prop?

They are a standard in larger props.

What about titanium?

Don't know. I think the answer here, is that it is too brittle to stand up
to the vibration, torque, and twisting.

Carbon fiber?

Yes. Some have been made with carbon fiber or fiberglass over wood or foam
cores.

What kind of testing needs to be done on a home built prop?

Much has been written, and there are even programs to predict performance.

Are there prop styles that can be copied without patent infringements?

As long as you don't copy too closely. There are some special features of
some props that are copyrighted.

Has anybody tried making a flexible prop?

Yes. Warp drive makes a flexible prop with a steel rod in the middle that
twists the tips with an electric motor, to change profiles for climb to
cruise. That is one feature that had better not be copied.

My thinking is that it might be possible to create a prop with a low angle
of attack for high power take offs, then have it flex to a higher angle of
attack as the load
decreases.

This has been done with a extremely swept back shape, called "scimitar",
that as it unloads at high speed, the tips twist back to higher angles of
attack. I am unaware if this is currently being produced. The trick is to
select materials and thickness, to get the twist just right, to work as
desired.

Could something like that give the performance of a constant speed prop
without the complexity and added weight?

There will always be tradeoffs of complexity and weight for this.

If I were to play around with different prop designs, is there somebody
around here with the knowledge and time that might be willing to test them
for me?

Hmm. My suggestion is learn, and do it yourself. g

I am sure there are more, here, that will correct some of what I have said,
and add more, given time.
--
Jim in NC

"LCT Paintball" wrote in
news:wtn4e.12908$Vx1.12789@attbi_s01:

I've been reading every post here for a few weeks. I am absolutely
amazed by the amount of knowledge that lives here!
With the butt kissing done, I hope you'll excuse my ignorance.

I was interested in the discussion concerning the weight of different
prop materials. Has anybody tried to make a hollow aluminum prop? What
about titanium? Carbon fiber?

Yes, to carbon fiber at least.

What kind of testing needs to be done on a home built prop?
Are there prop styles that can be copied without patent infringements?

Whatever you feel safe with, and a minimum of 40hrs (I think) on an
experimental, if it is a new combination or major change.

Has anybody tried making a flexible prop? My thinking is that it might
be possible to create a prop with a low angle of attack for high power
take offs, then have it flex to a higher angle of attack as the load
decreases. Could something like that give the performance of a
constant speed prop without the complexity and added weight?

Warnke almost constant speed among some.

If I were to play around with different prop designs, is there
somebody around here with the knowledge and time that might be willing
to test them for me?

Can you also provide the proper vehichle for the test period?


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Morgans wrote:
"LCT Paintball" wrote in message
What about titanium?

Don't know. I think the answer here, is that it is too brittle to stand up
to the vibration, torque, and twisting.

Not that I know (because I don't know), but it doesn't make sense
that titanium would be an unsuitable material. Gas turbines using
titanium alloy compressors have been around for, well, decades. Sort
of an apples and oranges comparison, but still... On the other hand
google doesn't seem to turn up anything, and it _always_ seems to
turn up something (!?).

Morgans wrote:
"LCT Paintball" wrote in message

With the butt kissing done, I hope you'll excuse my ignorance.

That is some first class "butt kissing." g

I don't have many answers, but I'll answer what I think I know, since
no one
else has answered.

I was interested in the discussion concerning the weight of
different prop
materials. Has anybody tried to make a hollow aluminum prop?

They are a standard in larger props.

What about titanium?

Don't know. I think the answer here, is that it is too brittle to
stand up
to the vibration, torque, and twisting.

Carbon fiber?

Yes. Some have been made with carbon fiber or fiberglass over wood
or foam
cores.

What kind of testing needs to be done on a home built prop?

Much has been written, and there are even programs to predict
performance.

Are there prop styles that can be copied without patent
infringements?

As long as you don't copy too closely. There are some special
features of
some props that are copyrighted.

Has anybody tried making a flexible prop?

Yes. Warp drive makes a flexible prop with a steel rod in the middle
that
twists the tips with an electric motor, to change profiles for climb
to
cruise. That is one feature that had better not be copied.

My thinking is that it might be possible to create a prop with a
low angle
of attack for high power take offs, then have it flex to a higher
angle of
attack as the load
decreases.

This has been done with a extremely swept back shape, called
"scimitar",
that as it unloads at high speed, the tips twist back to higher
angles of
attack. I am unaware if this is currently being produced. The trick
is to
select materials and thickness, to get the twist just right, to work
as
desired.

Could something like that give the performance of a constant speed
prop
without the complexity and added weight?

There will always be tradeoffs of complexity and weight for this.

If I were to play around with different prop designs, is there
somebody
around here with the knowledge and time that might be willing to
test them
for me?

Hmm. My suggestion is learn, and do it yourself. g

I am sure there are more, here, that will correct some of what I have
said,
and add more, given time.
--
Jim in NC

"Yes. Warp drive makes a flexible prop with a steel rod in the middle that
twists the tips with an electric motor, to change profiles for climb to
cruise. That is one feature that had better not be copied."

Sorry Morgan, but it is Ivo that makes them prop. Warpdrive are rather
rigid.

J.P.
"Morgans" wrote in message
news

"LCT Paintball" wrote in message

With the butt kissing done, I hope you'll excuse my ignorance.

That is some first class "butt kissing." g

I don't have many answers, but I'll answer what I think I know, since no
one
else has answered.

I was interested in the discussion concerning the weight of different
prop
materials. Has anybody tried to make a hollow aluminum prop?

They are a standard in larger props.

What about titanium?

Don't know. I think the answer here, is that it is too brittle to stand
up
to the vibration, torque, and twisting.

Carbon fiber?

Yes. Some have been made with carbon fiber or fiberglass over wood or
foam
cores.

What kind of testing needs to be done on a home built prop?

Much has been written, and there are even programs to predict performance.

Are there prop styles that can be copied without patent infringements?

As long as you don't copy too closely. There are some special features of
some props that are copyrighted.

Has anybody tried making a flexible prop?

Yes. Warp drive makes a flexible prop with a steel rod in the middle that
twists the tips with an electric motor, to change profiles for climb to
cruise. That is one feature that had better not be copied.

My thinking is that it might be possible to create a prop with a low
angle
of attack for high power take offs, then have it flex to a higher angle
of
attack as the load
decreases.

This has been done with a extremely swept back shape, called "scimitar",
that as it unloads at high speed, the tips twist back to higher angles of
attack. I am unaware if this is currently being produced. The trick is
to
select materials and thickness, to get the twist just right, to work as
desired.

Could something like that give the performance of a constant speed prop
without the complexity and added weight?

There will always be tradeoffs of complexity and weight for this.

If I were to play around with different prop designs, is there somebody
around here with the knowledge and time that might be willing to test
them
for me?

Hmm. My suggestion is learn, and do it yourself. g

I am sure there are more, here, that will correct some of what I have
said,
and add more, given time.
--
Jim in NC

"Jim Carriere" wrote

Not that I know (because I don't know), but it doesn't make sense
that titanium would be an unsuitable material. Gas turbines using
titanium alloy compressors have been around for, well, decades. Sort
of an apples and oranges comparison, but still...

Two big differences, as I see it. One, props on piston engines receive
massive power pulses, which are almost like stop and go, every 1/3rd to 1/2
rotation. A gas turbine blade has no pulses going to it; constant power and
constant rotation. Two, the turbine blade is very short and wide, compared
to the long slender prop.
--
Jim in NC

"Jean-Paul Roy" wrote

Sorry Morgan, but it is Ivo that makes them prop. Warpdrive are rather
rigid.

Ivo that makes them prop, Huh? g

See, I told you I wuld git somethang wong. ;-)
--
Jim in NC

Warp drive makes a flexible prop with a steel rod in the middle that
twists the tips with an electric motor, to change profiles for climb
to cruise. That is one feature that had better not be copied.

That has been done by Ivo Prop for a long time - www.ivoprop.com

On Tue, 05 Apr 2005 03:19:57 GMT, "LCT Paintball"
wrote:

I was interested in the discussion concerning the weight of different prop
materials. Has anybody tried to make a hollow aluminum prop? What about
titanium? Carbon fiber?

I am not a prop expert and don't play one on TV either, but like you
I've been hanging around here for a while (quite a long while
actually) and have learned a thing or two. I also spoke with a
Hamilton Standard engineer about a prop they built for the Lexus V-8
engine conversion. Hollow aluminum props are not uncommon. Don't
know about titanium. Carbon fiber props are made all the time by a
number of manufacturers, many are certified. Googling "carbon fiber
propeller" brings many hits including Warp Drive, Ivo and Sensenich,
to name a few.

What kind of testing needs to be done on a home built prop?
Are there prop styles that can be copied without patent infringements?

Be aware, props live in an EXTREMELY harsh environment. They are
subject to twisting loads, bending loads, centrifical forces and
engine power pulses. In addition they suffer abrasion from sand, dust
and gravel to rain and hail.

The one material I'm pretty sure you can use without much worry about
having one half of it disappear in flight is wood. Wood props dampen
vibration, metal and some composites can accelerate vibration if
encountered at the right frequency. The engineer I mentioned warned
me that in his opinion, many of the non certified prop makers were
making props that scared the absolute bejeesus out of him. Very few
did the kind of comprehensive vibration testing that they (the makers
of certified props) had to do, nor did they do long term systematic
test runs. He thought that people should be extremely careful about
what they use for a prop.

Has anybody tried making a flexible prop? My thinking is that it might be
possible to create a prop with a low angle of attack for high power take
offs, then have it flex to a higher angle of attack as the load decreases.
Could something like that give the performance of a constant speed prop
without the complexity and added weight?

Yes, a company did attempt to create a fixed pitch prop that varied
it's pitch by being flexible fairly recently. They called it the
Quasi Constant Speed Prop. It was computer designed using very
special composite materials oriented in specific patterns and thread
direction. They were scimitar shaped. They also incorporated
different airfoils for different parts of the prop because the prop
itself sees different airspeeds at different locations from the hub to
the tip. Many props use a Clark Y airfoil, which seems counter
intuitive when you realise that out at the tip, most props are going
some 400 to 500 mph.

Unfortunately, during vibration testing they discovered that the prop
had some problems and the last time I checked they'd given up
attempting to make an actual fixed yet variable pitch prop.

If I were to play around with different prop designs, is there somebody
around here with the knowledge and time that might be willing to test them
for me?
--
There are several on-line programs that allow you to design a prop.
The problem is prop design is inherently complicated due to the many
factors that go into their design. You have to factor in airplane
weight, wingspan, how fast the airplane is supposed to go, altitude it
will fly, air density, drag of the airframe, engine speed, prop
diameter, pitch, material to be used, air foil design, planform. I
mean it's almost hopelessly endless.

The formulas used to determine various aspects of prop design look
like nighmarish versions of greek. And that's if you're a
mathematician. :-)

There are also proprietary software designs that allow you to design
your own prop. These aren't cheap but they will allow you to create
your own prop and design virtually all aspects of it including the
planform. All the formulas are built into the program. You have to
plug in the particulars of your airplane.

To me, prop making is such a black art that I gave up attempting to
design my own and bought an Ivo.

Corky Scott