my ignorance

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

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. ;(

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

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

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

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

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:
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)."

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.

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