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)
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Subject: | 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.
>
>
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Subject: | 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)
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From: | "Ron @ KFHU" <captainron1@cox.net> |
Subject: | 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 <russ@rkiphoto.com> 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
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Subject: | 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.
>>
>>
>>
>>
>>
>>
>
>
____________________________________________________________
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Subject: | 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 <russ@rkiphoto.com> 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
>
>
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Subject: | 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.
>>>
>>>
>>>
>>>
>>>
>>>
>>
>>
>
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Subject: | 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!
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Subject: | 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!
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Subject: | 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!
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From: | "Ron @ KFHU" <captainron1@cox.net> |
Subject: | 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 <slyck@frontiernet.net> 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 <russ@rkiphoto.com> 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
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Subject: | strange sputtering |
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
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Subject: | 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
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