turbine propeller

On 17 Mar 2004 13:03:08 -0800, (sebastian) wrote:

ah well, that was exactly the type of feeback i was looking for
thanks.

My revised plan is to experiment with building a carbon fiber
propeller. I like the general design theory behind the wind turbine
that i specified, so I am thinking of inverting the pitch for thrust
and making the blade shorter and broader (45-50" diameter, 2-4" wide
tapering to tip). My plan is to make foam airfoil cores with a
hotwire cutter, extensively reinforce the lengthwise direction with
unidirectional carbon fiber roving, and wrap the whole blade with
carbon fiber farbric and vacuum bag. I would use a similar twisting
geometry that narrows and goes from ~20 degrees to nearly a flat pitch
at the tip and transforms from an elipitcal cross section at the hub
to an airfoil at the tip. or would it be better and simpler to have a
constant pitch, width, and airfoil and make the overall pitch ground
adjustable. Rememeber i need it to be as light and efficent as
possible this is for a paraglider fan (backpack type) not some big
beefy airplane. Any suggestions?

Sebastian, several people have fabricated composite propellers in
their shop. It isn't easy to do and the prop REALLY has to be of
sound construction in order to withstand the forces of thrust,
vibration reasonance and turbulence.

I suggest you do a search on the internet to see if you can find the
websites of those who have documented their techniques. Be prepared
to spend a LOT of time getting it right.

Propeller design is not simple.

Good luck, Corky Scott

Corky Scott wrote:


Sebastian, several people have fabricated composite propellers in
their shop. It isn't easy to do and the prop REALLY has to be of
sound construction in order to withstand the forces of thrust,
vibration reasonance and turbulence.

I suggest you do a search on the internet to see if you can find the
websites of those who have documented their techniques. Be prepared
to spend a LOT of time getting it right.

Propeller design is not simple.

Good luck, Corky Scott

In the library section to my website I have a link to "How I Make
Propeller"

The author does a very good job of telling you things you want to know.

--
http://www.ernest.isa-geek.org/
"Ignorance is mankinds normal state,
alleviated by information and experience."
Veeduber

Thanks Ernest,

To all you electric nay sayers take a look at this...
http://www.aviationtomorrow.com/nuke...ew_photo. php

the reason this guy is smilin is hes probably going to be the first
private aviator to have an functional electric airplane...never mind
its costing half a million smackers...ultimately hes gona use fuel
cells...but before that hes using...drumroll please...li ion
batteries...theyre doing the first electric flights in april so well
see...check out the rest of their web site pretty intersting...

you guys are right about lead acid batteries and that weight is the
major limitation but i think general aviation is on the cusp of
practical electic flight...im gona give it a try...and li ion
batteries
are part of my trick too...ive sourced some 10 amp hour li ion
batteries...and my total weight for 20ah@48v will be...well a small
fraction of la bats...not cheap...i also found some 100amp lightweight
controllers that i can run in parallel to as someone correctly
calculated run ~200amps peak...so i might be able to just barely do
it...keep my copper connectors short...and if i can run for 10 minutes
electric i would be happy because i know i could optimize tweek and
lighten to get more...thats the plan...so now i need a REALLY good
prop any more sugguestions appreciated...






Ernest Christley wrote in message om...
Corky Scott wrote:


Sebastian, several people have fabricated composite propellers in
their shop. It isn't easy to do and the prop REALLY has to be of
sound construction in order to withstand the forces of thrust,
vibration reasonance and turbulence.

I suggest you do a search on the internet to see if you can find the
websites of those who have documented their techniques. Be prepared
to spend a LOT of time getting it right.

Propeller design is not simple.

Good luck, Corky Scott

In the library section to my website I have a link to "How I Make
Propeller"

The author does a very good job of telling you things you want to know.

If you want an electric plane, you can buy one here.

http://www.alisport.com/eu/eng/silent_b.htm

They claim you can climb to over 2000 feet with a 90 pound battery, then
it turns into a sailplane and you do the rest with "solar thermal"
energy.

sebastian wrote:

Thanks Ernest,

To all you electric nay sayers take a look at this...
http://www.aviationtomorrow.com/nuke...ew_photo. php

the reason this guy is smilin is hes probably going to be the first
private aviator to have an functional electric airplane...never mind
its costing half a million smackers...ultimately hes gona use fuel
cells...but before that hes using...drumroll please...li ion
batteries...theyre doing the first electric flights in april so well
see...check out the rest of their web site pretty intersting...

you guys are right about lead acid batteries and that weight is the
major limitation but i think general aviation is on the cusp of
practical electic flight...im gona give it a try...and li ion
batteries
are part of my trick too...ive sourced some 10 amp hour li ion
batteries...and my total weight for 20ah@48v will be...well a small
fraction of la bats...not cheap...i also found some 100amp lightweight
controllers that i can run in parallel to as someone correctly
calculated run ~200amps peak...so i might be able to just barely do
it...keep my copper connectors short...and if i can run for 10 minutes
electric i would be happy because i know i could optimize tweek and
lighten to get more...thats the plan...so now i need a REALLY good
prop any more sugguestions appreciated...

Ernest Christley wrote in message om...
Corky Scott wrote:


Sebastian, several people have fabricated composite propellers in
their shop. It isn't easy to do and the prop REALLY has to be of
sound construction in order to withstand the forces of thrust,
vibration reasonance and turbulence.

I suggest you do a search on the internet to see if you can find the
websites of those who have documented their techniques. Be prepared
to spend a LOT of time getting it right.

Propeller design is not simple.

Good luck, Corky Scott

In the library section to my website I have a link to "How I Make
Propeller"

The author does a very good job of telling you things you want to know.

The Book "How I Make Propeller" is very good for what it says to be, HIS way
to make propellers, Interesting to see how he struggle to learn, He most of
the times have to make 2-3-4 propellers before he get it right, but he learn
from it every time, working a lot with VW's he is out on unknown waters, and
that don't make it easier. But he get to know his VW's (and others)

He is wrong about that it is impossible to calculate the correct pitch and
propeller, you don't have to guess.
They could do that during and before WW I
What he is guessing is really how powerful his engines is, and how fast the
plane will be.
Knowing the HP, RPM and Speed you can calculate an correct Propeller the
first time.
You can do that with pen and paper, hand-calculator or why not a computer.
The Computer make it possible to calculate it faster and more exact, easy to
change a parameter and see the result and get warnings when it start to get
unsafe, all in a milli sec.

Carving the Propeller isn't that hard as many think, all you need is some
tools most homebuilder have. Make a few templates, start with a saw and axe
or power disk sander, a draw knife or planer, and finish with sandpaper. A
propeller balancer should every homebuilder or wood propeller owner have.

Jan Carlsson
www.jcpropellerdesign.com


"Ernest Christley" skrev i meddelandet
m...
Corky Scott wrote:


Sebastian, several people have fabricated composite propellers in
their shop. It isn't easy to do and the prop REALLY has to be of
sound construction in order to withstand the forces of thrust,
vibration reasonance and turbulence.

I suggest you do a search on the internet to see if you can find the
websites of those who have documented their techniques. Be prepared
to spend a LOT of time getting it right.

Propeller design is not simple.

Good luck, Corky Scott

In the library section to my website I have a link to "How I Make
Propeller"

The author does a very good job of telling you things you want to know.

--
http://www.ernest.isa-geek.org/
"Ignorance is mankinds normal state,
alleviated by information and experience."
Veeduber

Knowing the HP, RPM and Speed you can calculate an correct Propeller the
first time.
You can do that with pen and paper, hand-calculator or why not a computer.
The Computer make it possible to calculate it faster and more exact, easy to
change a parameter and see the result and get warnings when it start to get
unsafe, all in a milli sec.


lets see ive got 15hp, 3400rpm and 25mph...can you help me out with
the calculations? thank you

hmm so i found this little model aiplane prop calculator utility...
http://www.gylesaero.com/freeware/propcalc.shtml

i plug in 3400 rpm and 0mph airspeed (static) and if i want ~100lbs of
thrust w/a 2blade it says i need an 8" pitch 50" diameter prop... i
think thats doable but many questions remain...

how do i select a propeller airfoil, aspect ratio?
does an 8" pitch seem reasonable for my application? thats 3.8degrees
at 0.75r if this little caculator is correct
so is pitch usually measures at 3/4 the radius of the prop?
how then do i determine twist from tip to hub?
Shold i just use constant pitch with no twist for simplicity?
how broad should the blade be?

aaaahh...


(sebastian) wrote in message . com...
Knowing the HP, RPM and Speed you can calculate an correct Propeller the
first time.
You can do that with pen and paper, hand-calculator or why not a computer.
The Computer make it possible to calculate it faster and more exact, easy to
change a parameter and see the result and get warnings when it start to get
unsafe, all in a milli sec.


lets see ive got 15hp, 3400rpm and 25mph...can you help me out with
the calculations? thank you