---------------------------------------------------------- Kolb-List Digest Archive --- Total Messages Posted Tue 06/02/09: 12 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 07:18 AM - Re: Re: WRT M3X prop boom measurements. (russ kinne) 2. 10:06 AM - michigan fly in for June 7th (Arksey@AOL.COM) 3. 12:08 PM - Re: Re: WRT M3X prop boom measurements. (Ron @ KFHU) 4. 12:34 PM - Re: Re: WRT M3X prop boom measurements. (Brad Stump) 5. 12:56 PM - Re: Re: WRT M3X prop boom measurements. (robert bean) 6. 03:10 PM - Re: Re: WRT M3X prop boom measurements. (russ kinne) 7. 04:09 PM - Re: Re: WRT M3X prop boom measurements. (Dana Hague) 8. 04:09 PM - Re: Re: WRT M3X prop boom measurements. (Dana Hague) 9. 04:10 PM - Re: Re: WRT M3X prop boom measurements. (Dana Hague) 10. 04:51 PM - Re: Re: WRT M3X prop boom measurements. (Ron @ KFHU) 11. 07:37 PM - strange sputtering (cristalclear13) 12. 08:53 PM - Re: strange sputtering (Mike Welch) ________________________________ Message 1 _____________________________________ Time: 07:18:13 AM PST US From: russ kinne Subject: Re: Kolb-List: Re: WRT M3X prop boom measurements. Boyd Excellent comments in re prop blades. Straightforward and, more importantly, accurate. Thank you Russ K do not archive On Jun 1, 2009, at 11:30 PM, b young wrote: > > Long winded post about props. If you are not interest hit delete. > > I have seen the charts that show small diameter props turning fast > rpm's > reach their maximum efficiencies at high speeds. AND large diameter > props reach their maximum efficiencies at slow speeds. > > SO when building a plane the first thing you want to do is to > determine > what the plane is to be designed to do. That will determine the > speed > range of the design, the speed of the design will determine the prop > diameter and pitch. > > > That said, the most efficient prop is a "1" blade prop... you read > it right > "one" blade. The problem with a one blade prop is keeping things in > balance. And yes it has been experimented with, you have to have > a counter > balance on the other side, and by playing with the angle of a > pivot you can > make it more or less a constant speed prop. When it is pulling > hard it will > cone forward and if mounted at the correct pivot angle it will > reduce the > pitch,,, when the plane is up to speed the centrifugal force > causes it to > run in a flatter coneing angle, increasing the pitch. Why do I > mention the > one blade prop as the most efficient???? because every prop or > wing going > through the air has two types of drag acting on it. > > Drag: drag may de subdivided into induced drag and parasite > drag. Induced > drag is simply the drag created in the process of developing lift / > thrust. > In addition to the induced drag caused by the development of lift, > there is > parasite drag due to skin friction and form. This term is used > because > parasite drag is not directly associated with the development of lift. > Parasite drag is present ant time the wing or prop is moving > through the > air, even in a zero lift condition. > > The more blades the more parasite drag. The more parasite drag, > the more HP > will be used up that is not creating lift / thrust, the more hp not > producing thrust the less efficient the prop / wing. > > Now props work best when set to the best pitch angle at cruise, as > to be > able to use up the available HP. Fast aircraft have a high pitch > angle. > And if set as a constant pitch, they have very poor takeoff > performance. > That is why they put on a variable pitch prop on fast aircraft. So > they can > maximize the efficiency at both slow and fast speeds. At the > speed that > the kolb line of aircraft fly,, the variable pitch seems unnecessary. > Because we get good take off performance and flight with one > pitch. Look at > the production aircraft that fly in the speeds that the kolbs fly. > They > have very simple fixed pitch props. Generally a two blade prop. > Now as > the HP increases and you start to have prop ground clearance > problems, and > you cant pitch the prop to use up the available HP in cruise, by > setting the > pitch for maximum efficiency, then you add an additional blade. > > Now on a pusher there is a different reason to add the third blade > sooner > than you would on a tractor, that is because of the noise > developed by > having a prop with greater pitch go into and out of the disturbed > airflow. > The smaller pitch on a three blade seem to make less noise. But we > trade > the quieter operation for less efficiency caused by increased > parasite > drag. > > On most aircraft the prop diameter is limited by ground > clearance. Has > anyone ever seen a Cessna 150, or a j5 cub with a 45 inch 6 blade > prop? If > it were more efficient it would be the norm. > > Boyd Young > Kolb MkIII C 580+ hours and counting > Brigham City Utah. > > ________________________________ Message 2 _____________________________________ Time: 10:06:23 AM PST US From: Arksey@AOL.COM Subject: Kolb-List: michigan fly in for June 7th I am planning on attending the coldwater (OEB) Michigan fly in 6-7-09, Looks like there will be several of us with Kolbs there if weather permits...forecast is for cloudy, 63 deg. wind ENE at 11 miles per hour....hope to get there my 9 am... do not archive JIM SWAN firestar ll, 503, N663S Eaton Rapids, Mi. 48827 PH 517-663-8488 runway 2300' E & W (42-28.58N 084-44.69 W ) **************An Excellent Credit Score is 750. See Yours in Just 2 Easy Steps! eExcfooterNO62) ________________________________ Message 3 _____________________________________ Time: 12:08:27 PM PST US From: "Ron @ KFHU" Subject: Re: Kolb-List: Re: WRT M3X prop boom measurements. A couple of years ago I pretty much had said to Bob B pretty much what I will say again. The claim that a singe blade prop is more efficient than say a 2 blade prop does not stand the test of reason. I have heard that claim since I was a kid, that a one blade prop is better but never quite understood it even back then. As Bob just stated the one blade prop is supposedly more efficient because it always slices in undisturbed air. Well !!! As I said a couple of years ago that is false, the claim that a one blade prop is more efficient is false! Lets for example take my airplane in cruise flight I believe its a 80 inch bore spiral. In any one revolution of the prop you move forward 80 inches. Okay,,,? so the second blade is always ahead of where the first blade was by 40 inches. In other words at all times unless maybe right at the beginning of the take off roll the following blade is always in undisturbed air. On a four blade prop each blade is always 20 inches forward than the previous one and so on. Why we don't have a 4 blade prop on a J3? Well I doubt it was certified with one back in the Golden days of aviation. But I have seen glider tow airplanes using 4 blades for towing. On a J3 we are not going to see all that much difference in cruise but we will see it in climb. The drag of the airframe gets ever greater as the speed increases so prop efficiency will only help so much, but in a climb where the speed is low there we see the better efficiency, the exponential increase in drag is still less noticed at low air speeds. But in our draggy Kolbs we may see it for other reasons one of which the turbulent air for a pusher, there the multi blade will shine very nicely because it is able to "catch" more of the "crappy" air behind us. ================================================================================================================= ---- russ kinne wrote: ============ Boyd Excellent comments in re prop blades. Straightforward and, more importantly, accurate. Thank you Russ K do not archive On Jun 1, 2009, at 11:30 PM, b young wrote: > > Long winded post about props. If you are not interest hit delete. > > I have seen the charts that show small diameter props turning fast > rpm's > reach their maximum efficiencies at high speeds. AND large diameter > props reach their maximum efficiencies at slow speeds. > > SO when building a plane the first thing you want to do is to > determine > what the plane is to be designed to do. That will determine the > speed > range of the design, the speed of the design will determine the prop > diameter and pitch. > > > That said, the most efficient prop is a "1" blade prop... you read > it right > "one" blade. The problem with a one blade prop is keeping things in > balance. And yes it has been experimented with, you have to have > a counter > balance on the other side, and by playing with the angle of a > pivot you can > make it more or less a constant speed prop. When it is pulling > hard it will > cone forward and if mounted at the correct pivot angle it will > reduce the > pitch,,, when the plane is up to speed the centrifugal force > causes it to > run in a flatter coneing angle, increasing the pitch. Why do I > mention the > one blade prop as the most efficient???? because every prop or > wing going > through the air has two types of drag acting on it. > > Drag: drag may de subdivided into induced drag and parasite > drag. Induced > drag is simply the drag created in the process of developing lift / > thrust. > In addition to the induced drag caused by the development of lift, > there is > parasite drag due to skin friction and form. This term is used > because > parasite drag is not directly associated with the development of lift. > Parasite drag is present ant time the wing or prop is moving > through the > air, even in a zero lift condition. > > The more blades the more parasite drag. The more parasite drag, > the more HP > will be used up that is not creating lift / thrust, the more hp not > producing thrust the less efficient the prop / wing. > > Now props work best when set to the best pitch angle at cruise, as > to be > able to use up the available HP. Fast aircraft have a high pitch > angle. > And if set as a constant pitch, they have very poor takeoff > performance. > That is why they put on a variable pitch prop on fast aircraft. So > they can > maximize the efficiency at both slow and fast speeds. At the > speed that > the kolb line of aircraft fly,, the variable pitch seems unnecessary. > Because we get good take off performance and flight with one > pitch. Look at > the production aircraft that fly in the speeds that the kolbs fly. > They > have very simple fixed pitch props. Generally a two blade prop. > Now as > the HP increases and you start to have prop ground clearance > problems, and > you cant pitch the prop to use up the available HP in cruise, by > setting the > pitch for maximum efficiency, then you add an additional blade. > > Now on a pusher there is a different reason to add the third blade > sooner > than you would on a tractor, that is because of the noise > developed by > having a prop with greater pitch go into and out of the disturbed > airflow. > The smaller pitch on a three blade seem to make less noise. But we > trade > the quieter operation for less efficiency caused by increased > parasite > drag. > > On most aircraft the prop diameter is limited by ground > clearance. Has > anyone ever seen a Cessna 150, or a j5 cub with a 45 inch 6 blade > prop? If > it were more efficient it would be the norm. > > Boyd Young > Kolb MkIII C 580+ hours and counting > Brigham City Utah. > > -- kugelair.com ________________________________ Message 4 _____________________________________ Time: 12:34:26 PM PST US From: Brad Stump Subject: Re: Kolb-List: Re: WRT M3X prop boom measurements. Hi Russ, I hope i'am not asking a dumb question here,but I need some advice.My engine's peak Hp is at 6500 rpm,I climb out at 700-800 fpm,and cruse at 65-70 mph.If I increase the pitch of my 3-blade prop, will I increase my cruse or climb rate? > -----Original Message----- > From: russ@rkiphoto.com > Sent: Tue, 2 Jun 2009 10:13:53 -0400 > To: kolb-list@matronics.com > Subject: Re: Kolb-List: Re: WRT M3X prop boom measurements. > > > Boyd > Excellent comments in re prop blades. Straightforward and, more > importantly, accurate. > Thank you > Russ K > do not archive > > On Jun 1, 2009, at 11:30 PM, b young wrote: > >> >> Long winded post about props. If you are not interest hit delete. >> >> I have seen the charts that show small diameter props turning fast >> rpm's >> reach their maximum efficiencies at high speeds. AND large diameter >> props reach their maximum efficiencies at slow speeds. >> >> SO when building a plane the first thing you want to do is to >> determine >> what the plane is to be designed to do. That will determine the >> speed >> range of the design, the speed of the design will determine the prop >> diameter and pitch. >> >> >> That said, the most efficient prop is a "1" blade prop... you read >> it right >> "one" blade. The problem with a one blade prop is keeping things in >> balance. And yes it has been experimented with, you have to have >> a counter >> balance on the other side, and by playing with the angle of a >> pivot you can >> make it more or less a constant speed prop. When it is pulling >> hard it will >> cone forward and if mounted at the correct pivot angle it will >> reduce the >> pitch,,, when the plane is up to speed the centrifugal force >> causes it to >> run in a flatter coneing angle, increasing the pitch. Why do I >> mention the >> one blade prop as the most efficient???? because every prop or >> wing going >> through the air has two types of drag acting on it. >> >> Drag: drag may de subdivided into induced drag and parasite >> drag. Induced >> drag is simply the drag created in the process of developing lift / >> thrust. >> In addition to the induced drag caused by the development of lift, >> there is >> parasite drag due to skin friction and form. This term is used >> because >> parasite drag is not directly associated with the development of lift. >> Parasite drag is present ant time the wing or prop is moving >> through the >> air, even in a zero lift condition. >> >> The more blades the more parasite drag. The more parasite drag, >> the more HP >> will be used up that is not creating lift / thrust, the more hp not >> producing thrust the less efficient the prop / wing. >> >> Now props work best when set to the best pitch angle at cruise, as >> to be >> able to use up the available HP. Fast aircraft have a high pitch >> angle. >> And if set as a constant pitch, they have very poor takeoff >> performance. >> That is why they put on a variable pitch prop on fast aircraft. So >> they can >> maximize the efficiency at both slow and fast speeds. At the >> speed that >> the kolb line of aircraft fly,, the variable pitch seems unnecessary. >> Because we get good take off performance and flight with one >> pitch. Look at >> the production aircraft that fly in the speeds that the kolbs fly. >> They >> have very simple fixed pitch props. Generally a two blade prop. >> Now as >> the HP increases and you start to have prop ground clearance >> problems, and >> you cant pitch the prop to use up the available HP in cruise, by >> setting the >> pitch for maximum efficiency, then you add an additional blade. >> >> Now on a pusher there is a different reason to add the third blade >> sooner >> than you would on a tractor, that is because of the noise >> developed by >> having a prop with greater pitch go into and out of the disturbed >> airflow. >> The smaller pitch on a three blade seem to make less noise. But we >> trade >> the quieter operation for less efficiency caused by increased >> parasite >> drag. >> >> On most aircraft the prop diameter is limited by ground >> clearance. Has >> anyone ever seen a Cessna 150, or a j5 cub with a 45 inch 6 blade >> prop? If >> it were more efficient it would be the norm. >> >> Boyd Young >> Kolb MkIII C 580+ hours and counting >> Brigham City Utah. >> >> >> >> >> >> > > ____________________________________________________________ GET FREE 5GB EMAIL - Check out spam free email with many cool features! Visit http://www.inbox.com/email to find out more! ________________________________ Message 5 _____________________________________ Time: 12:56:34 PM PST US From: robert bean Subject: Re: Kolb-List: Re: WRT M3X prop boom measurements. Ron, you are referencing the the wrong "Bob" I have stayed out of this pointless joust fest (with the exception of the heli viewpoint) because it has gone beyond my attention span. Important update: between beers I have managed to complete the steel gear leg installation with a healthy guess as to alignment, hauled the old beast up the hill to the summer bug infested shelter (carpenter bees the size of wrens) and somehow managed to avoid dinging another delicate surface. I have a Powerfin 2 blade hub creeping via UPS across the USA that I will be comparing with my current 2 blade WD setup. To be fair it will be 65" powerfin against 70" WD so it really isn't apples to apples. By the time I get the wings back on with the assistance of my brother, the summer should be half over. With any luck I may? get as much time in this season as John H. did in one week. -nahhh BB On 2, Jun 2009, at 3:07 PM, Ron @ KFHU wrote: > > A couple of years ago I pretty much had said to Bob B pretty much > what I will say again. > The claim that a singe blade prop is more efficient than say a 2 > blade prop does not stand the test of reason. I have heard that > claim since I was a kid, that a one blade prop is better but never > quite understood it even back then. > As Bob just stated the one blade prop is supposedly more efficient > because it always slices in undisturbed air. > Well !!! As I said a couple of years ago that is false, the claim > that a one blade prop is more efficient is false! > Lets for example take my airplane in cruise flight I believe its a > 80 inch bore spiral. In any one revolution of the prop you move > forward 80 inches. > Okay,,,? so the second blade is always ahead of where the first > blade was by 40 inches. In other words at all times unless maybe > right at the beginning of the take off roll the following blade is > always in undisturbed air. On a four blade prop each blade is > always 20 inches forward than the previous one and so on. > Why we don't have a 4 blade prop on a J3? Well I doubt it was > certified with one back in the Golden days of aviation. But I have > seen glider tow airplanes using 4 blades for towing. On a J3 we are > not going to see all that much difference in cruise but we will see > it in climb. The drag of the airframe gets ever greater as the > speed increases so prop efficiency will only help so much, but in a > climb where the speed is low there we see the better efficiency, > the exponential increase in drag is still less noticed at low air > speeds. But in our draggy Kolbs we may see it for other reasons one > of which the turbulent air for a pusher, there the multi blade will > shine very nicely because it is able to "catch" more of the > "crappy" air behind us. > ====================================================================== > =========================================== > ---- russ kinne wrote: > > ============ > > Boyd > Excellent comments in re prop blades. Straightforward and, more > importantly, accurate. > Thank you > Russ K > do not archive > > On Jun 1, 2009, at 11:30 PM, b young wrote: > >> >> Long winded post about props. If you are not interest hit delete. >> >> I have seen the charts that show small diameter props turning fast >> rpm's >> reach their maximum efficiencies at high speeds. AND large >> diameter >> props reach their maximum efficiencies at slow speeds. >> >> SO when building a plane the first thing you want to do is to >> determine >> what the plane is to be designed to do. That will determine the >> speed >> range of the design, the speed of the design will determine the prop >> diameter and pitch. >> >> >> That said, the most efficient prop is a "1" blade prop... you read >> it right >> "one" blade. The problem with a one blade prop is keeping things in >> balance. And yes it has been experimented with, you have to have >> a counter >> balance on the other side, and by playing with the angle of a >> pivot you can >> make it more or less a constant speed prop. When it is pulling >> hard it will >> cone forward and if mounted at the correct pivot angle it will >> reduce the >> pitch,,, when the plane is up to speed the centrifugal force >> causes it to >> run in a flatter coneing angle, increasing the pitch. Why do I >> mention the >> one blade prop as the most efficient???? because every prop or >> wing going >> through the air has two types of drag acting on it. >> >> Drag: drag may de subdivided into induced drag and parasite >> drag. Induced >> drag is simply the drag created in the process of developing lift / >> thrust. >> In addition to the induced drag caused by the development of lift, >> there is >> parasite drag due to skin friction and form. This term is used >> because >> parasite drag is not directly associated with the development of >> lift. >> Parasite drag is present ant time the wing or prop is moving >> through the >> air, even in a zero lift condition. >> >> The more blades the more parasite drag. The more parasite drag, >> the more HP >> will be used up that is not creating lift / thrust, the more hp not >> producing thrust the less efficient the prop / wing. >> >> Now props work best when set to the best pitch angle at cruise, as >> to be >> able to use up the available HP. Fast aircraft have a high pitch >> angle. >> And if set as a constant pitch, they have very poor takeoff >> performance. >> That is why they put on a variable pitch prop on fast aircraft. So >> they can >> maximize the efficiency at both slow and fast speeds. At the >> speed that >> the kolb line of aircraft fly,, the variable pitch seems >> unnecessary. >> Because we get good take off performance and flight with one >> pitch. Look at >> the production aircraft that fly in the speeds that the kolbs fly. >> They >> have very simple fixed pitch props. Generally a two blade prop. >> Now as >> the HP increases and you start to have prop ground clearance >> problems, and >> you cant pitch the prop to use up the available HP in cruise, by >> setting the >> pitch for maximum efficiency, then you add an additional blade. >> >> Now on a pusher there is a different reason to add the third blade >> sooner >> than you would on a tractor, that is because of the noise >> developed by >> having a prop with greater pitch go into and out of the disturbed >> airflow. >> The smaller pitch on a three blade seem to make less noise. But we >> trade >> the quieter operation for less efficiency caused by increased >> parasite >> drag. >> >> On most aircraft the prop diameter is limited by ground >> clearance. Has >> anyone ever seen a Cessna 150, or a j5 cub with a 45 inch 6 blade >> prop? If >> it were more efficient it would be the norm. >> >> Boyd Young >> Kolb MkIII C 580+ hours and counting >> Brigham City Utah. >> >> >> >> >> >> > > > -- > kugelair.com > > ________________________________ Message 6 _____________________________________ Time: 03:10:53 PM PST US From: russ kinne Subject: Re: Kolb-List: Re: WRT M3X prop boom measurements. Brad You should be asking Boyd Young or John Hauck. They're much more informed than I am. In any case I think testing is the only way to know for sure. Russ K On Jun 2, 2009, at 3:35 PM, Brad Stump wrote: > > Hi Russ, > I hope i'am not asking a dumb question here,but I need some > advice.My engine's peak Hp is at 6500 rpm,I climb out at 700-800 > fpm,and cruse at 65-70 mph.If I increase the pitch of my 3-blade > prop, will I increase my cruse or climb rate? > >> -----Original Message----- >> From: russ@rkiphoto.com >> Sent: Tue, 2 Jun 2009 10:13:53 -0400 >> To: kolb-list@matronics.com >> Subject: Re: Kolb-List: Re: WRT M3X prop boom measurements. >> >> >> Boyd >> Excellent comments in re prop blades. Straightforward and, more >> importantly, accurate. >> Thank you >> Russ K >> do not archive >> >> On Jun 1, 2009, at 11:30 PM, b young wrote: >> >>> >>> Long winded post about props. If you are not interest hit delete. >>> >>> I have seen the charts that show small diameter props turning fast >>> rpm's >>> reach their maximum efficiencies at high speeds. AND large >>> diameter >>> props reach their maximum efficiencies at slow speeds. >>> >>> SO when building a plane the first thing you want to do is to >>> determine >>> what the plane is to be designed to do. That will determine the >>> speed >>> range of the design, the speed of the design will determine the prop >>> diameter and pitch. >>> >>> >>> That said, the most efficient prop is a "1" blade prop... you read >>> it right >>> "one" blade. The problem with a one blade prop is keeping things in >>> balance. And yes it has been experimented with, you have to have >>> a counter >>> balance on the other side, and by playing with the angle of a >>> pivot you can >>> make it more or less a constant speed prop. When it is pulling >>> hard it will >>> cone forward and if mounted at the correct pivot angle it will >>> reduce the >>> pitch,,, when the plane is up to speed the centrifugal force >>> causes it to >>> run in a flatter coneing angle, increasing the pitch. Why do I >>> mention the >>> one blade prop as the most efficient???? because every prop or >>> wing going >>> through the air has two types of drag acting on it. >>> >>> Drag: drag may de subdivided into induced drag and parasite >>> drag. Induced >>> drag is simply the drag created in the process of developing lift / >>> thrust. >>> In addition to the induced drag caused by the development of lift, >>> there is >>> parasite drag due to skin friction and form. This term is used >>> because >>> parasite drag is not directly associated with the development of >>> lift. >>> Parasite drag is present ant time the wing or prop is moving >>> through the >>> air, even in a zero lift condition. >>> >>> The more blades the more parasite drag. The more parasite drag, >>> the more HP >>> will be used up that is not creating lift / thrust, the more hp not >>> producing thrust the less efficient the prop / wing. >>> >>> Now props work best when set to the best pitch angle at cruise, as >>> to be >>> able to use up the available HP. Fast aircraft have a high pitch >>> angle. >>> And if set as a constant pitch, they have very poor takeoff >>> performance. >>> That is why they put on a variable pitch prop on fast aircraft. So >>> they can >>> maximize the efficiency at both slow and fast speeds. At the >>> speed that >>> the kolb line of aircraft fly,, the variable pitch seems >>> unnecessary. >>> Because we get good take off performance and flight with one >>> pitch. Look at >>> the production aircraft that fly in the speeds that the kolbs fly. >>> They >>> have very simple fixed pitch props. Generally a two blade prop. >>> Now as >>> the HP increases and you start to have prop ground clearance >>> problems, and >>> you cant pitch the prop to use up the available HP in cruise, by >>> setting the >>> pitch for maximum efficiency, then you add an additional blade. >>> >>> Now on a pusher there is a different reason to add the third blade >>> sooner >>> than you would on a tractor, that is because of the noise >>> developed by >>> having a prop with greater pitch go into and out of the disturbed >>> airflow. >>> The smaller pitch on a three blade seem to make less noise. But we >>> trade >>> the quieter operation for less efficiency caused by increased >>> parasite >>> drag. >>> >>> On most aircraft the prop diameter is limited by ground >>> clearance. Has >>> anyone ever seen a Cessna 150, or a j5 cub with a 45 inch 6 blade >>> prop? If >>> it were more efficient it would be the norm. >>> >>> Boyd Young >>> Kolb MkIII C 580+ hours and counting >>> Brigham City Utah. >>> >>> >>> >>> >>> >>> >> >> > > ____________________________________________________________ > GET FREE 5GB EMAIL - Check out spam free email with many cool > features! > Visit http://www.inbox.com/email to find out more! > > ________________________________ Message 7 _____________________________________ Time: 04:09:55 PM PST US From: Dana Hague Subject: Re: Kolb-List: Re: WRT M3X prop boom measurements. At 03:07 PM 6/2/2009, Ron @ KFHU wrote: >A couple of years ago I pretty much had said to Bob B pretty much what I >will say again. >The claim that a singe blade prop is more efficient than say a 2 blade >prop does not stand the test of reason. I have heard that claim since I >was a kid, that a one blade prop is better but never quite understood it >even back then... For aircraft like ours, I agree that there wouldn't be much if any measurable advantage to a one blade prop, and the associated problems would outweigh any slight advantages. However, they have been used to advantage on some model airplanes... control line "speed" ships that can do 200mph, with engines turning around 30,000 rpm. With such tiny props turning so fast, the blades ARE close enough together that going to one blade helps. -Dana -- A goverment that fears arms in the hands of it people should also fear ROPE! ________________________________ Message 8 _____________________________________ Time: 04:09:56 PM PST US From: Dana Hague Subject: Re: Kolb-List: Re: WRT M3X prop boom measurements. At 03:07 PM 6/2/2009, Ron @ KFHU wrote: >A couple of years ago I pretty much had said to Bob B pretty much what I >will say again. >The claim that a singe blade prop is more efficient than say a 2 blade >prop does not stand the test of reason. I have heard that claim since I >was a kid, that a one blade prop is better but never quite understood it >even back then... For aircraft like ours, I agree that there wouldn't be much if any measurable advantage to a one blade prop, and the associated problems would outweigh any slight advantages. However, they have been used to advantage on some model airplanes... control line "speed" ships that can do 200mph, with engines turning around 30,000 rpm. With such tiny props turning so fast, the blades ARE close enough together that going to one blade helps. -Dana -- A goverment that fears arms in the hands of it people should also fear ROPE! ________________________________ Message 9 _____________________________________ Time: 04:10:07 PM PST US From: Dana Hague Subject: Re: Kolb-List: Re: WRT M3X prop boom measurements. At 03:35 PM 6/2/2009, Brad Stump wrote: >I hope i'am not asking a dumb question here,but I need some advice.My >engine's peak Hp is at 6500 rpm,I climb out at 700-800 fpm,and cruse at >65-70 mph.If I increase the pitch of my 3-blade prop, will I increase my >cruse or climb rate? If your prop is already pitched optimally for climb, increasing the pitch will improve your cruise at the expense of climb. If it's pitched too flat for best climb, you'll improve both. If you already have too much pitch for best cruise, both may suffer. Generally a prop is pitched for a good compromise between climb and cruise, often a bit more one way or another... so you hear people talk about a "climb prop" or a "cruise prop". On a typical small slow plane, IIRC the difference is about 2" of pitch. -Dana -- A goverment that fears arms in the hands of it people should also fear ROPE! ________________________________ Message 10 ____________________________________ Time: 04:51:16 PM PST US From: "Ron @ KFHU" Subject: Re: Kolb-List: Re: WRT M3X prop boom measurements. Sorry about the mix up. :-) Its kinda fun but its getting boring, I think I have reached the end of my stamina on this subject. Good for you about the gear legs, I am ever more worried about the ones that came with the kit on my M3x. with the big motor which I estimate my power unit flying weight complete to be around 200 pounds. Them skinny 7075 legs will not take much to start looking like a soggy noodles. ---- robert bean wrote: ============ Ron, you are referencing the the wrong "Bob" I have stayed out of this pointless joust fest (with the exception of the heli viewpoint) because it has gone beyond my attention span. Important update: between beers I have managed to complete the steel gear leg installation with a healthy guess as to alignment, hauled the old beast up the hill to the summer bug infested shelter (carpenter bees the size of wrens) and somehow managed to avoid dinging another delicate surface. I have a Powerfin 2 blade hub creeping via UPS across the USA that I will be comparing with my current 2 blade WD setup. To be fair it will be 65" powerfin against 70" WD so it really isn't apples to apples. By the time I get the wings back on with the assistance of my brother, the summer should be half over. With any luck I may? get as much time in this season as John H. did in one week. -nahhh BB On 2, Jun 2009, at 3:07 PM, Ron @ KFHU wrote: > > A couple of years ago I pretty much had said to Bob B pretty much > what I will say again. > The claim that a singe blade prop is more efficient than say a 2 > blade prop does not stand the test of reason. I have heard that > claim since I was a kid, that a one blade prop is better but never > quite understood it even back then. > As Bob just stated the one blade prop is supposedly more efficient > because it always slices in undisturbed air. > Well !!! As I said a couple of years ago that is false, the claim > that a one blade prop is more efficient is false! > Lets for example take my airplane in cruise flight I believe its a > 80 inch bore spiral. In any one revolution of the prop you move > forward 80 inches. > Okay,,,? so the second blade is always ahead of where the first > blade was by 40 inches. In other words at all times unless maybe > right at the beginning of the take off roll the following blade is > always in undisturbed air. On a four blade prop each blade is > always 20 inches forward than the previous one and so on. > Why we don't have a 4 blade prop on a J3? Well I doubt it was > certified with one back in the Golden days of aviation. But I have > seen glider tow airplanes using 4 blades for towing. On a J3 we are > not going to see all that much difference in cruise but we will see > it in climb. The drag of the airframe gets ever greater as the > speed increases so prop efficiency will only help so much, but in a > climb where the speed is low there we see the better efficiency, > the exponential increase in drag is still less noticed at low air > speeds. But in our draggy Kolbs we may see it for other reasons one > of which the turbulent air for a pusher, there the multi blade will > shine very nicely because it is able to "catch" more of the > "crappy" air behind us. > ====================================================================== > =========================================== > ---- russ kinne wrote: > > ============ > > Boyd > Excellent comments in re prop blades. Straightforward and, more > importantly, accurate. > Thank you > Russ K > do not archive > > On Jun 1, 2009, at 11:30 PM, b young wrote: > >> >> Long winded post about props. If you are not interest hit delete. >> >> I have seen the charts that show small diameter props turning fast >> rpm's >> reach their maximum efficiencies at high speeds. AND large >> diameter >> props reach their maximum efficiencies at slow speeds. >> >> SO when building a plane the first thing you want to do is to >> determine >> what the plane is to be designed to do. That will determine the >> speed >> range of the design, the speed of the design will determine the prop >> diameter and pitch. >> >> >> That said, the most efficient prop is a "1" blade prop... you read >> it right >> "one" blade. The problem with a one blade prop is keeping things in >> balance. And yes it has been experimented with, you have to have >> a counter >> balance on the other side, and by playing with the angle of a >> pivot you can >> make it more or less a constant speed prop. When it is pulling >> hard it will >> cone forward and if mounted at the correct pivot angle it will >> reduce the >> pitch,,, when the plane is up to speed the centrifugal force >> causes it to >> run in a flatter coneing angle, increasing the pitch. Why do I >> mention the >> one blade prop as the most efficient???? because every prop or >> wing going >> through the air has two types of drag acting on it. >> >> Drag: drag may de subdivided into induced drag and parasite >> drag. Induced >> drag is simply the drag created in the process of developing lift / >> thrust. >> In addition to the induced drag caused by the development of lift, >> there is >> parasite drag due to skin friction and form. This term is used >> because >> parasite drag is not directly associated with the development of >> lift. >> Parasite drag is present ant time the wing or prop is moving >> through the >> air, even in a zero lift condition. >> >> The more blades the more parasite drag. The more parasite drag, >> the more HP >> will be used up that is not creating lift / thrust, the more hp not >> producing thrust the less efficient the prop / wing. >> >> Now props work best when set to the best pitch angle at cruise, as >> to be >> able to use up the available HP. Fast aircraft have a high pitch >> angle. >> And if set as a constant pitch, they have very poor takeoff >> performance. >> That is why they put on a variable pitch prop on fast aircraft. So >> they can >> maximize the efficiency at both slow and fast speeds. At the >> speed that >> the kolb line of aircraft fly,, the variable pitch seems >> unnecessary. >> Because we get good take off performance and flight with one >> pitch. Look at >> the production aircraft that fly in the speeds that the kolbs fly. >> They >> have very simple fixed pitch props. Generally a two blade prop. >> Now as >> the HP increases and you start to have prop ground clearance >> problems, and >> you cant pitch the prop to use up the available HP in cruise, by >> setting the >> pitch for maximum efficiency, then you add an additional blade. >> >> Now on a pusher there is a different reason to add the third blade >> sooner >> than you would on a tractor, that is because of the noise >> developed by >> having a prop with greater pitch go into and out of the disturbed >> airflow. >> The smaller pitch on a three blade seem to make less noise. But we >> trade >> the quieter operation for less efficiency caused by increased >> parasite >> drag. >> >> On most aircraft the prop diameter is limited by ground >> clearance. Has >> anyone ever seen a Cessna 150, or a j5 cub with a 45 inch 6 blade >> prop? If >> it were more efficient it would be the norm. >> >> Boyd Young >> Kolb MkIII C 580+ hours and counting >> Brigham City Utah. >> >> >> >> >> >> > > > -- > kugelair.com > > -- kugelair.com ________________________________ Message 11 ____________________________________ Time: 07:37:10 PM PST US Subject: Kolb-List: strange sputtering From: "cristalclear13" Decided to take my dad, who is visiting me, on a little cross country in my Kolb Mark II to Douglas, GA. I wanted to show him the WWII museum there but found out they are only open on Fridays and Saturdays once we got there. We had had some fog in the morning but it burned off around 10:30am and so we headed out. When we got to Douglas and landed, I was about to turn the plane around and exit on the taxiway I just passed but when I started to turn and gave it a little more on the throttle it kind of sputtered and wouldn't rev up. I pulled it back and tried it again and it went fine. Then when I was parking her it did it again. My carbs were sweating the front one more than the back. That isn't unusual in the hot weather we have though. On the front carb where the rubber socket is the carb had some black stuff along the edge where it fits into the socket (whereas my back carb was nice and clean in that area). I grabbed my screwdriver and tightened the clamp around the socket. It may have been a little loose. Perhaps it was sucking air? We ate lunch, considered our options and then decided to start it up, if no problems then take off and go around the airport a bit. We didn't have any more problems so we headed home and didn't have any more symptoms of the sort. The afternoon thermals sure gave us an interesting ride home. I think I'm getting more used to it. I think I had my best landing yet with a full-size passenger when Dad and I got back to Waycross. :D Side note to George Alexander: Got your message...thanks. -------- Cristal Waters Kolb Mark II Twinstar Rotax 503 DCSI Read this topic online here: http://forums.matronics.com/viewtopic.php?p=246552#246552 ________________________________ Message 12 ____________________________________ Time: 08:53:33 PM PST US From: Mike Welch Subject: RE: Kolb-List: strange sputtering > My carbs were sweating the front one more than the back. That isn't unusu al in the hot >weather we have though.> -------- > Cristal Waters > Kolb Mark II Twinstar > Rotax 503 DCSI Christal=2C Sounds as though you experienced the classic symptoms of "carb icing"=2C although from your description of the carb's sweating=2C you may have only developed condensation=2C not icing. If your rpms are high=2C as they are in cruise=2C your engine can usually ride out the humidity's sweating condition. However=2C the moisture often presents itself on throttling back=2C as in the landing mode or taxiing. It's not uncommon for some people to report their engines died on enterin g the traffic pattern(with a reduced power setting). I'm not sure what you could do to minimize this tendency. Has anyone com e up with a carb heat mechanism for Bing carbs?? Mike Welch MkIII _________________________________________________________________ Insert movie times and more without leaving Hotmail=AE. http://windowslive.com/Tutorial/Hotmail/QuickAdd?ocid=TXT_TAGLM_WL_HM_Tut orial_QuickAdd_062009 ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message kolb-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/Kolb-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/kolb-list Browse Digests http://www.matronics.com/digest/kolb-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.