my ignorance

"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

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 (!?).

"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

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

"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

Morgans wrote:

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.

Hartzell, very popular with the racing and nonracing Lancairs...

Nice photo of one he
http://www.ramaircraft.com/Whats-New...-Propeller.htm

Thrust comparison he
http://www.beryldshannon.com/Hartzell/chart.htm

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.


I want to say that the IVO prop has this mode of operation. I have not
looked at the Warp Drive closely enough to validate what you are saying.

The IVO has some drawbacks, however. I don't believe it's compatible
with 4 cylinder lycomings (torque pulses are damaging...) and i know of
a few who have tried to use the IVO in flight adjustable prop for high
speed flight, and found it less than satisfactory. Since the inboard
portion doesnt rotate as much, it must produce some "flat plate" drag..
anecdotal reports of a 10 mph penalty on a 200 mph aircraft are what I
recall.

For the slower planes, this may not be an issue..

Dave

i know of
a few who have tried to use the IVO in flight adjustable prop for
high speed flight, and found it less than satisfactory. Since the
inboard portion doesnt rotate as much, it must produce some "flat
plate" drag.. anecdotal reports of a 10 mph penalty on a 200 mph
aircraft are what I recall.

Thats at least partially true of all inflight adjustable props. For a
particular speed and power there is an ideal shape that can be achieved
by fixed pitch props. The adjustable (CS) props design their shape for
an average effect over the speed range. But the adjustable prop still
gives a decent high speed efficiency while giving that extra safety
factor at takeoff and landing - takeoff like a slingshot and you can
really slow down the plane on landing with low pitch setting. So you
have to take your choices - can't have everything.
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SQ2000 canard http://www.abri.com/sq2000