turbine propeller

Hi Jan I really appreciate the feedback,

Paragliders are inherently very very slow. A typical paramotor will
have between 15-30hp a very moderate climb rate of 150-300ft/min,
climb speed of 15-20mph, and cruise at about 25-30mph, max speed
~35mph on good day. Part of the reason im setting out to design my
own is that i plan to make use of an electric motor rather that
internal combustion engine. Im using a dc motor that produces maxium
power (15hp) at 48v with 72 rpm/volt =3456rpm. But i may try to run
it at 36v first =2592rpm. One of the nice things about this motor is
its increadibly high and flat torque across the rpm range.

so constant speed propeller= no twist but changes angle of attack
and constant pitch propeller =constant change in angle over length
(twist) how is that measured... angle change/inch???
fixed angle propeller =no change in pitch or angle of attack

how do i do i measure or determine loading... or since i know my
torque will be good at any speed should i design the propeller for
maximum power which i know is going to be ~3400rpm.

and how do i factor number of blades in the the equation...simpler
would be better but wont more blades allow more thrust per rpm and
smaller diameter and lower tip speed/noise...part of the reason im
going electric is to make it as quiet as possible...

thanks!!!!



'Jan Carlsson" wrote in message ...
Sebastian,

With data on both engine and speed it is easy to calculate an propeller.

I sugest you make a wood propeller first, then you can see how much prop you
need, The Idea is to "load" the engine so you get the desired RPM, with the
most optimum prop you can get at the design "point" (speed)
Even if it is calculated correctly there can be unknown factors, like if the
engine turn out 2 HP more or less!?
Then it is easy quick and cheep to make a new wood propeller

The blade have to be twisted, you have to know the differens of Pitch and
Angle, an prop with uniform pitch along the blade have the blade twisted to
higher angle closer to the hub. Even with reduced pitch near the hub, the
angle is normaly higher there.

With the Prop behind the back(pack) It will work in turbulant air, specially
near the hub it will be "dead" air, closer to the tip it will work in the
"aircrafts" forward speed + the induced air (air sucked in)
The Induced airspeed will be large compered to forward speed.

What is the normal Climb speed, Cruise speed and top speed for a paramotor?

Jan Carlsson
www.jcpropellerdesign.com

"sebastian" skrev i meddelandet
om...
then youre saying the best way to answer the questions
is...empirically.
or can i make decisions a priori about prop geometry based on my input
power (15hp) and rpm (2500)? it would seem that long non twisting,
tapered, symetric airfoil blades that are ground adjustable in pitch
and varied in the nr of blades on the hub would be the better way
since the the variables of pitch, diameter(shortening), & nr of blades
could be experimented with and optimized. I suppose under these
circumstances all effort should be put into aspect ratio since that is
the one varibale that would be most difficult to vary and test. so
with that said, any advice on choosing an aspect ratio for my purpose?
and as a i vary these parameters...how do i measure changes in thrust
directly...attach my motor to a scale somehow?

"Jan Carlsson" wrote in message
...
A constant pitch will be better then a constant angle and blade width.

The Q is what Pitch, what Diameter, what Aspect Ratio, what nr of
blades?

The questions is the same whatever it is a one meter model plane, back
pak
or a turbo-prop.

Jan Carlsson


"sebastian" skrev i meddelandet
om...
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" wrote

how do i do i measure or determine loading... or since i know my
torque will be good at any speed should i design the propeller for
maximum power which i know is going to be ~3400rpm.

and how do i factor number of blades in the the equation...simpler
would be better but wont more blades allow more thrust per rpm and
smaller diameter and lower tip speed/noise...part of the reason im
going electric is to make it as quiet as possible...

thanks!!!!

More importantly, how do you factor in the couple hundred pounds of battery
weight?

Start by doing some power required, and wattage required calculations. Then
convert that to battery weight you can afford. You may soon see why
electric flight has not become a realistic option.
--
Jim in NC


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"sebastian" wrote in message
om...
Hi Jan I really appreciate the feedback,

Paragliders are inherently very very slow. A typical paramotor will
have between 15-30hp a very moderate climb rate of 150-300ft/min,
climb speed of 15-20mph, and cruise at about 25-30mph, max speed
~35mph on good day. Part of the reason im setting out to design my
own is that i plan to make use of an electric motor rather that
internal combustion engine. Im using a dc motor that produces maxium
power (15hp) at 48v with 72 rpm/volt =3456rpm. But i may try to run
it at 36v first =2592rpm. One of the nice things about this motor is
its increadibly high and flat torque across the rpm range.

and how do i factor number of blades in the the equation...simpler
would be better but wont more blades allow more thrust per rpm and
smaller diameter and lower tip speed/noise...part of the reason im
going electric is to make it as quiet as possible...

thanks!!!!


You might want to consider that a horsepower is 746 watts.
15 times that is about 11000 watts. At 50 volts, you're going to be drawing
about 220 Amperes.
You're going to need a lot of copper to transmit that current. You're going
to need a lot of battery to provide 220 amps for any significant period of
time. Designing a motor controller at those currents is _NOT_ a trivial
exercise.

A propeller is the least of your worries.

Tim Ward

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.

I like your idea of experimenting if you just wanted to fly it would be
cheeper to just buy a redy to fly kit.

I put some comments in between below;

"sebastian" wrote.
Hi Jan I really appreciate the feedback,

Paragliders are inherently very very slow. A typical paramotor will
have between 15-30hp a very moderate climb rate of 150-300ft/min,
climb speed of 15-20mph, and cruise at about 25-30mph, max speed
~35mph on good day. Part of the reason im setting out to design my
own is that i plan to make use of an electric motor rather that
internal combustion engine. Im using a dc motor that produces maxium
power (15hp) at 48v with 72 rpm/volt =3456rpm. But i may try to run
it at 36v first =2592rpm. One of the nice things about this motor is [How
many HP is it developing at 36V?]
its increadibly high and flat torque across the rpm range.

so constant speed propeller= no twist but changes angle of attack [
Constant speed propellers keep the RPM at the from cockpit set RPM, The
propeller still have a twist ]
and constant pitch propeller =constant change in angle over length [
Correct]
(twist) how is that measured... angle change/inch??? [ Normaly the pitch
is measured at different Stations along the blade, like 15, 30, 45, 60, 75,
and 90% of the radii.]
fixed angle propeller =no change in pitch or angle of attack [Called Fixed
Pitch Propellers.]
[ A constantspeed/adjusteble prop can have a constant PITCH at a certain
angle measured at the 75% radii (like15 deg.) from tip to about 40% radii.
The blade angle change ofcourse with the radii to keep the pitch. When the
Pitch/angle is changed (blade rotated) the pitch will no longer be constant,
with higher then the 15 deg setting the PITCH will be greater at the tip
then at the 40% radii ]

how do i do i measure or determine loading... or since i know my
torque will be good at any speed should i design the propeller for
maximum power which i know is going to be ~3400rpm. [You want the engine
to turn at maximum at max speed, or with a less powerful engine near max rpm
at climb speed, then you will cruise at near max RPM but with reduced power,
that is good with en electric engine because it will use less energy at high
RPM then at reduced RPM with more propeller load. ]

and how do i factor number of blades in the the equation...simpler
would be better but wont more blades allow more thrust per rpm and
smaller diameter and lower tip speed/noise...part of the reason im
going electric is to make it as quiet as possible... [ I don't think the
tip speed will be a problem, a 2 blad prop will be better with its larger
diameter, what you want/need is max thrust with the extra weight from
batteries and the relativ weak engine. With the 15 HP/3450 RPM you will end
up with a 43"- 45" diameter, 38,5" with 3 blade, and 35,5" with 4 blade!]

Jan Carlsson
www.jcpropellerdesign.com



thanks!!!!



'Jan Carlsson" wrote in message
...
Sebastian,

With data on both engine and speed it is easy to calculate an
propeller.

I sugest you make a wood propeller first, then you can see how much prop
you
need, The Idea is to "load" the engine so you get the desired RPM, with
the
most optimum prop you can get at the design "point" (speed)
Even if it is calculated correctly there can be unknown factors, like if
the
engine turn out 2 HP more or less!?
Then it is easy quick and cheep to make a new wood propeller

The blade have to be twisted, you have to know the differens of Pitch
and
Angle, an prop with uniform pitch along the blade have the blade twisted
to
higher angle closer to the hub. Even with reduced pitch near the hub,
the
angle is normaly higher there.

With the Prop behind the back(pack) It will work in turbulant air,
specially
near the hub it will be "dead" air, closer to the tip it will work in
the
"aircrafts" forward speed + the induced air (air sucked in)
The Induced airspeed will be large compered to forward speed.

What is the normal Climb speed, Cruise speed and top speed for a
paramotor?

Jan Carlsson
www.jcpropellerdesign.com

"sebastian" skrev i meddelandet
om...
then youre saying the best way to answer the questions
is...empirically.
or can i make decisions a priori about prop geometry based on my input
power (15hp) and rpm (2500)? it would seem that long non twisting,
tapered, symetric airfoil blades that are ground adjustable in pitch
and varied in the nr of blades on the hub would be the better way
since the the variables of pitch, diameter(shortening), & nr of blades
could be experimented with and optimized. I suppose under these
circumstances all effort should be put into aspect ratio since that is
the one varibale that would be most difficult to vary and test. so
with that said, any advice on choosing an aspect ratio for my purpose?
and as a i vary these parameters...how do i measure changes in thrust
directly...attach my motor to a scale somehow?

"Jan Carlsson" wrote in message
...
A constant pitch will be better then a constant angle and blade
width.

The Q is what Pitch, what Diameter, what Aspect Ratio, what nr of
blades?

The questions is the same whatever it is a one meter model plane,
back
pak
or a turbo-prop.

Jan Carlsson


"sebastian" skrev i meddelandet
om...
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?

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