Question:
– Hide quoted text — Show quoted text -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
Response:
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? – Hide quoted text — Show quoted text – 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 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?
Response:
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 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?
– Hide quoted text — Show quoted text – 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 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?
Response:
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!!!! – Hide quoted text — Show quoted text – 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 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? 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 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?
Response:
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 — Outgoing mail is certified Virus Free. Checked by AVG anti-virus system (http://www.grisoft.com).
Response:
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
Response:
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… – Hide quoted text — Show quoted text – 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
Response:
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 – Hide quoted text — Show quoted text – 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
Response:
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!!!!
– Hide quoted text — Show quoted text – 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 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? 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 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?
Response:
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. – Hide quoted text — Show quoted text – Thanks Ernest, To all you electric nay sayers take a look at this… http://www.aviationtomorrow.com/nuke/modules.php?set_albumName=album0… 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 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… 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.
Response:
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
Response:
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
Response:
Thanks Ernest, To all you electric nay sayers take a look at this… http://www.aviationtomorrow.com/nuke/modules.php?set_albumName=album0… 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 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… – Hide quoted text — Show quoted text – 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.
Response:
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 – Hide quoted text — Show quoted text – 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?
– Hide quoted text — Show quoted text – Well spoken Dan Thomas, I wanted Sebastian to see and come to an understanding of the difference him self. Even if it was a airplane propeller that was used as wind mill, (just as wrong) it is the wrong way to start with the propeller, then put an engine and aircraft to the propeller. It have to be a careful process picking out a propeller to suit the engine AND airplane, when correct you can fine tune the purpose of the propeller a few inch in diameter and pitch, depending on if you want a good climb or cruise or something in between. Jan Carlsson If the wind-mill fan is correctly engineered to be wind-driven it is unlikly good as propeller. A propeller have the convex side in the direction of flight, and the round leading edge in direction of rotation, and the pitch …. Jan Carlsson www.jcpropellerdesign.com Definitely won’t work, as Jan says. The blade camber is backward to a propeller’s, since it it designed to convert thrust to rotation rather than rotation to thrust. I’d be worried about that turbine failing when driven by an engine. It is designed for more or less constant rotational speed, but a piston engine has powerful torque pulses that will cause failure of such light structures as a wind turbine fan. Airplane propellers are designed to withstand those forces. If your fan threw a blade, the vibration would rip the engine off your paraglider, and/or the remaining blades might do serious damage to you or the machine. Dan Hi I’m working on an aviation project…a motorized paraglider fan specifically…and i had a question about using a wind turbine as the propeller The one on this page is the one im thinking of using: http://www.hydrogenappliances.com/bladekits.html Its some kind of plastic reinforced carbon fiber with ~60" diameter. Six blades. Its supposed to be good up to several thousand rpm and has a 70 year outdoor weather rating…so im guessing its reasonably tough…not bad for $89. My main question is will it work as a propeller to generate enough thrust…say 50-100lbs…im going to be able to supply it with geometry…near the hub it has an eliptical cross section with a wide base and a severe pitch… as the blade proceeds out to the tip it goes COMPLETELY flat (no pitch) but in cross section it has a lovely airfoil with a flat side (bottom of wing) and a curved airfoil on the other side (top of wing)…for the wind turbine application use they indicate to put the flat side of the airfoil facing the wind…which way should I orient the flat side if I want to use it for thrust…how would I make thrust calculations or even better measure thrust directly? Will the flexabilty of the prop be stabilized by centripital force even when under load (pushing my 180lb body under a paraglider wing) i.e. will the prop remain reasonably flat if spinning fast enough and not bend and hack my legs/head off….it seems like it is really well engineered from a aeronautics standpoint…i would probalbly make a custom heavy duty hub so please focus replies on the blades…thanks…more generally have any of you used 5/6 blade props on an ultralight? id be interesting in hearing your impressions of how well it worked for you compared to a 2/3/4 blade prop…
Response:
Hi I’m working on an aviation project…a motorized paraglider fan specifically…and i had a question about using a wind turbine as the propeller The one on this page is the one im thinking of using: http://www.hydrogenappliances.com/bladekits.html Its some kind of plastic reinforced carbon fiber with ~60" diameter. Six blades. Its supposed to be good up to several thousand rpm and has a 70 year outdoor weather rating…so im guessing its reasonably tough…not bad for $89. My main question is will it work as a propeller to generate enough thrust…say 50-100lbs…im going to be able to supply it with geometry…near the hub it has an eliptical cross section with a wide base and a severe pitch… as the blade proceeds out to the tip it goes COMPLETELY flat (no pitch) but in cross section it has a lovely airfoil with a flat side (bottom of wing) and a curved airfoil on the other side (top of wing)…for the wind turbine application use they indicate to put the flat side of the airfoil facing the wind…which way should I orient the flat side if I want to use it for thrust…how would I make thrust calculations or even better measure thrust directly? Will the flexabilty of the prop be stabilized by centripital force even when under load (pushing my 180lb body under a paraglider wing) i.e. will the prop remain reasonably flat if spinning fast enough and not bend and hack my legs/head off….it seems like it is really well engineered from a aeronautics standpoint…i would probalbly make a custom heavy duty hub so please focus replies on the blades…thanks…more generally have any of you used 5/6 blade props on an ultralight? id be interesting in hearing your impressions of how well it worked for you compared to a 2/3/4 blade prop…
Response:
If the wind-mill fan is correctly engineered to be wind-driven it is unlikly good as propeller. A propeller have the convex side in the direction of flight, and the round leading edge in direction of rotation, and the pitch …. Jan Carlsson www.jcpropellerdesign.com – Hide quoted text — Show quoted text – Hi I’m working on an aviation project…a motorized paraglider fan specifically…and i had a question about using a wind turbine as the propeller The one on this page is the one im thinking of using: http://www.hydrogenappliances.com/bladekits.html Its some kind of plastic reinforced carbon fiber with ~60" diameter. Six blades. Its supposed to be good up to several thousand rpm and has a 70 year outdoor weather rating…so im guessing its reasonably tough…not bad for $89. My main question is will it work as a propeller to generate enough thrust…say 50-100lbs…im going to be able to supply it with geometry…near the hub it has an eliptical cross section with a wide base and a severe pitch… as the blade proceeds out to the tip it goes COMPLETELY flat (no pitch) but in cross section it has a lovely airfoil with a flat side (bottom of wing) and a curved airfoil on the other side (top of wing)…for the wind turbine application use they indicate to put the flat side of the airfoil facing the wind…which way should I orient the flat side if I want to use it for thrust…how would I make thrust calculations or even better measure thrust directly? Will the flexabilty of the prop be stabilized by centripital force even when under load (pushing my 180lb body under a paraglider wing) i.e. will the prop remain reasonably flat if spinning fast enough and not bend and hack my legs/head off….it seems like it is really well engineered from a aeronautics standpoint…i would probalbly make a custom heavy duty hub so please focus replies on the blades…thanks…more generally have any of you used 5/6 blade props on an ultralight? id be interesting in hearing your impressions of how well it worked for you compared to a 2/3/4 blade prop…
Response:
If the wind-mill fan is correctly engineered to be wind-driven it is unlikly good as propeller. A propeller have the convex side in the direction of flight, and the round leading edge in direction of rotation, and the pitch …. Jan Carlsson www.jcpropellerdesign.com
Definitely won’t work, as Jan says. The blade camber is backward to a propeller’s, since it it designed to convert thrust to rotation rather than rotation to thrust. I’d be worried about that turbine failing when driven by an engine. It is designed for more or less constant rotational speed, but a piston engine has powerful torque pulses that will cause failure of such light structures as a wind turbine fan. Airplane propellers are designed to withstand those forces. If your fan threw a blade, the vibration would rip the engine off your paraglider, and/or the remaining blades might do serious damage to you or the machine. Dan – Hide quoted text — Show quoted text – Hi I’m working on an aviation project…a motorized paraglider fan specifically…and i had a question about using a wind turbine as the propeller The one on this page is the one im thinking of using: http://www.hydrogenappliances.com/bladekits.html Its some kind of plastic reinforced carbon fiber with ~60" diameter. Six blades. Its supposed to be good up to several thousand rpm and has a 70 year outdoor weather rating…so im guessing its reasonably tough…not bad for $89. My main question is will it work as a propeller to generate enough thrust…say 50-100lbs…im going to be able to supply it with geometry…near the hub it has an eliptical cross section with a wide base and a severe pitch… as the blade proceeds out to the tip it goes COMPLETELY flat (no pitch) but in cross section it has a lovely airfoil with a flat side (bottom of wing) and a curved airfoil on the other side (top of wing)…for the wind turbine application use they indicate to put the flat side of the airfoil facing the wind…which way should I orient the flat side if I want to use it for thrust…how would I make thrust calculations or even better measure thrust directly? Will the flexabilty of the prop be stabilized by centripital force even when under load (pushing my 180lb body under a paraglider wing) i.e. will the prop remain reasonably flat if spinning fast enough and not bend and hack my legs/head off….it seems like it is really well engineered from a aeronautics standpoint…i would probalbly make a custom heavy duty hub so please focus replies on the blades…thanks…more generally have any of you used 5/6 blade props on an ultralight? id be interesting in hearing your impressions of how well it worked for you compared to a 2/3/4 blade prop…
Response:
Yeah, maybe you should try one of those egg-beater windmills instead. Won’t get you anywhere, but you’ll win with the "cool factor". Pete
Response:
Well spoken Dan Thomas, I wanted Sebastian to see and come to an understanding of the difference him self. Even if it was a airplane propeller that was used as wind mill, (just as wrong) it is the wrong way to start with the propeller, then put an engine and aircraft to the propeller. It have to be a careful process picking out a propeller to suit the engine AND airplane, when correct you can fine tune the purpose of the propeller a few inch in diameter and pitch, depending on if you want a good climb or cruise or something in between. Jan Carlsson
– Hide quoted text — Show quoted text – If the wind-mill fan is correctly engineered to be wind-driven it is unlikly good as propeller. A propeller have the convex side in the direction of flight, and the round leading edge in direction of rotation, and the pitch …. Jan Carlsson www.jcpropellerdesign.com Definitely won’t work, as Jan says. The blade camber is backward to a propeller’s, since it it designed to convert thrust to rotation rather than rotation to thrust. I’d be worried about that turbine failing when driven by an engine. It is designed for more or less constant rotational speed, but a piston engine has powerful torque pulses that will cause failure of such light structures as a wind turbine fan. Airplane propellers are designed to withstand those forces. If your fan threw a blade, the vibration would rip the engine off your paraglider, and/or the remaining blades might do serious damage to you or the machine. Dan Hi I’m working on an aviation project…a motorized paraglider fan specifically…and i had a question about using a wind turbine as the propeller The one on this page is the one im thinking of using: http://www.hydrogenappliances.com/bladekits.html Its some kind of plastic reinforced carbon fiber with ~60" diameter. Six blades. Its supposed to be good up to several thousand rpm and has a 70 year outdoor weather rating…so im guessing its reasonably tough…not bad for $89. My main question is will it work as a propeller to generate enough thrust…say 50-100lbs…im going to be able to supply it with geometry…near the hub it has an eliptical cross section with a wide base and a severe pitch… as the blade proceeds out to the tip it goes COMPLETELY flat (no pitch) but in cross section it has a lovely airfoil with a flat side (bottom of wing) and a curved airfoil on the other side (top of wing)…for the wind turbine application use they indicate to put the flat side of the airfoil facing the wind…which way should I orient the flat side if I want to use it for thrust…how would I make thrust calculations or even better measure thrust directly? Will the flexabilty of the prop be stabilized by centripital force even when under load (pushing my 180lb body under a paraglider wing) i.e. will the prop remain reasonably flat if spinning fast enough and not bend and hack my legs/head off….it seems like it is really well engineered from a aeronautics standpoint…i would probalbly make a custom heavy duty hub so please focus replies on the blades…thanks…more generally have any of you used 5/6 blade props on an ultralight? id be interesting in hearing your impressions of how well it worked for you compared to a 2/3/4 blade prop…
Response:
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? – Hide quoted text — Show quoted text – Well spoken Dan Thomas, I wanted Sebastian to see and come to an understanding of the difference him self. Even if it was a airplane propeller that was used as wind mill, (just as wrong) it is the wrong way to start with the propeller, then put an engine and aircraft to the propeller. It have to be a careful process picking out a propeller to suit the engine AND airplane, when correct you can fine tune the purpose of the propeller a few inch in diameter and pitch, depending on if you want a good climb or cruise or something in between. Jan Carlsson If the wind-mill fan is correctly engineered to be wind-driven it is unlikly good as propeller. A propeller have the convex side in the direction of flight, and the round leading edge in direction of rotation, and the pitch …. Jan Carlsson www.jcpropellerdesign.com Definitely won’t work, as Jan says. The blade camber is backward to a propeller’s, since it it designed to convert thrust to rotation rather than rotation to thrust. I’d be worried about that turbine failing when driven by an engine. It is designed for more or less constant rotational speed, but a piston engine has powerful torque pulses that will cause failure of such light structures as a wind turbine fan. Airplane propellers are designed to withstand those forces. If your fan threw a blade, the vibration would rip the engine off your paraglider, and/or the remaining blades might do serious damage to you or the machine. Dan Hi I’m working on an aviation project…a motorized paraglider fan specifically…and i had a question about using a wind turbine as the propeller The one on this page is the one im thinking of using: http://www.hydrogenappliances.com/bladekits.html Its some kind of plastic reinforced carbon fiber with ~60" diameter. Six blades. Its supposed to be good up to several thousand rpm and has a 70 year outdoor weather rating…so im guessing its reasonably tough…not bad for $89. My main question is will it work as a propeller to generate enough thrust…say 50-100lbs…im going to be able to supply it with geometry…near the hub it has an eliptical cross section with a wide base and a severe pitch… as the blade proceeds out to the tip it goes COMPLETELY flat (no pitch) but in cross section it has a lovely airfoil with a flat side (bottom of wing) and a curved airfoil on the other side (top of wing)…for the wind turbine application use they indicate to put the flat side of the airfoil facing the wind…which way should I orient the flat side if I want to use it for thrust…how would I make thrust calculations or even better measure thrust directly? Will the flexabilty of the prop be stabilized by centripital force even when under load (pushing my 180lb body under a paraglider wing) i.e. will the prop remain reasonably flat if spinning fast enough and not bend and hack my legs/head off….it seems like it is really well engineered from a aeronautics standpoint…i would probalbly make a custom heavy duty hub so please focus replies on the blades…thanks…more generally have any of you used 5/6 blade props on an ultralight? id be interesting in hearing your impressions of how well it worked for you compared to a 2/3/4 blade prop…
Response:
It is possible to use the NMEA output of the Garmin 430/530 as an input for a PC. 
Flew VOR direct from KBTR, taxi’d right into the parking lot at AirTech. Looks like they had a recent resurfacing of the runway and taxiways, very nice and smooth. Excellent lighting too, grass was a bit tall though… Any details on that 150 in the weeds one the north end of the ramp? I looked up the N number, but that guy doesn’t exist in the nearby area… 
) 
kneeboard. it keeps my small notepad handy and allows me to scribble notes with one hand — i don’t have to fish for the pad, and i don’t have to hold it in place when i write. I write notes on a small spiral notepad, preferably with a pen. Everything else goes into a little bag or a pocket where I can reach it when I need it. There is absolutely no need to have everything spread out in front of you all of the time. A simple clipboard is sufficient for your cross country navigation log. 