my ignorance

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.
----------------------------------------
SQ2000 canard http://www.abri.com/sq2000

abripl wrote:
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.

Variable pitch isn't only useful over an aircraft with a wide speed
range, it is practically necessary for a turbocharged engine.

If the engine maintains power up at a high altitude, coarser prop
pitch is required to take a bigger bite out of the thinner air.

I should be more specific and state a turbo-normalized engine (or
supercharged-normalized, if such things exist in great numbers).
Point being a powerplant that produces it's rated sea level power at
high altitude.

What about titanium?

I think that the lack of titanium bladed props is purely economic. It is a
very tough material, so I don't think strength or brittleness would be a
problem. Compared to wood, aluminum, and composite construction, it is very
expensive.

tom

A number of aftermarket manufacturers make coil springs for racing
cars. Titanium has good retention for a short period but eventually
loses shape under high stress - see description at
http://www.coilspring.com/performance/auto_racing/ particularly the
comment: "Titanium springs are not 'forever'..."

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

Nope, I can't even fly, unless of course I talk one of you guys into taking
me up.

I find the prospect of building an airplane very interesting. I've studied
the skills required, and have decided that I can handle it. I've also
studied the time required and found I'm not even close! ;(

I thought it might be interesting to play around with building a prop. I own
a machine shop complete with design tools, CAM software, and CNC equipment.
I have a better than average grasp of high school math, but obviously can't
handle the kind of design work it would take to pull of a project like this.

I enjoy wrapping my brain around a problem, and coming up with a low tech
solution. I don't have the time, or budget to get involved with a large
project, but thought a prop might be within reach. After reading the group's
responses, I'm still confident I can build one, but I don't think I can
design it. ;(

LCT Paintball wrote:
Can you also provide the proper vehichle for the test period?


Nope, I can't even fly, unless of course I talk one of you guys into taking
me up.

I find the prospect of building an airplane very interesting. I've studied
the skills required, and have decided that I can handle it. I've also
studied the time required and found I'm not even close! ;(

I thought it might be interesting to play around with building a prop. I own
a machine shop complete with design tools, CAM software, and CNC equipment.
I have a better than average grasp of high school math, but obviously can't
handle the kind of design work it would take to pull of a project like this.

I enjoy wrapping my brain around a problem, and coming up with a low tech
solution. I don't have the time, or budget to get involved with a large
project, but thought a prop might be within reach. After reading the group's
responses, I'm still confident I can build one, but I don't think I can
design it. ;(




http://ernest.isa-geek.org/Delta/Lib...wIMakeProp.pdf

--
This is by far the hardest lesson about freedom. It goes against
instinct, and morality, to just sit back and watch people make
mistakes. We want to help them, which means control them and their
decisions, but in doing so we actually hurt them (and ourselves)."

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

In article wtn4e.12908$Vx1.12789@attbi_s01,
"LCT Paintball" wrote:


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

Try at the Prop Carving website; http://www.wood-carver.com/store.html

I know of two company that sell propeller design software, and there are
some other online, but them seems all to be incomplete, I am not saying this
to sell more, just fact, but some don't calculate the Diameter ! one of the
most important design criteria, other lack strength and safety
calculations...

I made my program for my own use, then I have changed it many times to be
more user friendly and complete, Rome wasn't built in one day, so I have but
in many hours making the program work as I wanted it and by requests from
customers, and not least making it work with both US system and metric
system, and on computers all around the globe.

My program is made for the home builder in mind, it is not that difficult to
make a wood prop, if you can make a airplane you can make a propeller,
calculate it can be time consuming, isn't that the reason we have computers?
all the time we save with the computer... or is it spend with the computer?
anyway, Now it is possible to calculate a prop in a minute, make it in a CAD
program in 10 minutes, make drawings and templates or even let a CNC router
make the prop. (but we have to glue the laminates together) Making it by
hand is still an option, and very satisfying when finished, not all have a
home made prop in the nose or rear, at the fly-ins!

Real Propeller design software cost some, but that is saved in on the first
propeller made. then you can make props for your friends too.

Jan Carlsson
www.jcpropellerdesign.com



"LCT Paintball" skrev i meddelandet
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?

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