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High Thrust Line Question
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victorbravo(at)sbcglobal.
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PostPosted: Mon May 07, 2018 2:23 pm    Post subject: High Thrust Line Question Reply with quote

Kolbers, I ran into a significant problem on my Firestar, and it may cause me to not be able to finish the project. I hope this is not as much of a problem as I fear.

When I bought my HKS engine I did not know to ask whether it had one type gearbox or another. It has the 3.47 to 1 box, which will spin a large propeller very slowly.

After reading some ot the Kolb List stories about high thrust lines and putting the Kolb over on its nose, I realized I wanted to keep the thrust line as low as possible for best performance and handling. However, with the gearbox rotated to the "down" position, it limited the propeller diameter to 64 inches with a one inch tailboom clearance. With the 3.47 gearbox I have, a three blade propeller with 62-64 inch diameter is not enough... the engine will overspeed before I get the full amount of thrust.

Someone suggested using a four or five blade propeller, but that would prevent the wings from folding back.

I contacted the engine distributor to ask if I could switch the gears around to make my gearbox a 2.58 to 1 ratio,a nd you cannot do that without changing the gearbox itself.

So I asked how much it would cost to buy a new gearbox, andit is way too high for me to consider doing right now. Maybe when I win the lottery.

Someone else suggested that I turn the gearbox around facing "up", which would allow a much larger propeller. My first reaction was "Oh goodness no, that will raise the thrust line too high, and it will cause the airplane to nose over on takeoff, I'll run out of elevator control, etc. etc...."

But then I realized that was an assumption rather than a known fact. Before I gave up on the project, perhaps I can move the gearbox upwards and not have problems... but how far?

So I would like to ask the experienced Kolbers: JUST EXACTLY HOW HIGH can the thrust line be on a Kolb Firestar 2 before it creates safety/handling/nose-over problems? Can the center of the propeller be 34 inches above the tailboom...36 inches...38 inches...40 inches????
Bill Berle
www.ezflaphandle.com  - safety & performance upgrade for light aircraft
www.grantstar.net           - winning proposals for non-profit and for-profit entities


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lcottrell



Joined: 29 May 2006
Posts: 1490
Location: Jordan Valley, Or

PostPosted: Mon May 07, 2018 2:38 pm    Post subject: High Thrust Line Question Reply with quote

I'm swinging a 66 inch Warp with the gear box in the down position.Larry
On Mon, May 7, 2018 at 4:21 PM, Bill Berle <victorbravo(at)sbcglobal.net (victorbravo(at)sbcglobal.net)> wrote:
Quote:
--> Kolb-List message posted by: Bill Berle <victorbravo(at)sbcglobal.net (victorbravo(at)sbcglobal.net)>

Kolbers, I ran into a significant problem on my Firestar, and it may cause me to not be able to finish the project. I hope this is not as much of a problem as I fear.

When I bought my HKS engine I did not know to ask whether it had one type gearbox or another. It has the 3.47 to 1 box, which will spin a large propeller very slowly.

After reading some ot the Kolb List stories about high thrust lines and putting the Kolb over on its nose, I realized I wanted to keep the thrust line as low as possible for best performance and handling. However, with the gearbox rotated to the "down" position, it limited the propeller diameter to 64 inches with a one inch tailboom clearance. With the 3.47 gearbox I have, a three blade propeller with 62-64 inch diameter is not enough... the engine will overspeed before I get the full amount of thrust.

Someone suggested using a four or five blade propeller, but that would prevent the wings from folding back.

I contacted the engine distributor to ask if I could switch the gears around to make my gearbox a 2.58 to 1 ratio,a nd you cannot do that without changing the gearbox itself.

So I asked how much it would cost to buy a new gearbox, andit is way too high for me to consider doing right now. Maybe when I win the lottery.

Someone else suggested that I turn the gearbox around facing "up", which would allow a much larger propeller. My first reaction was "Oh goodness no, that will raise the thrust line too high, and it will cause the airplane to nose over on takeoff, I'll run out of elevator control, etc. etc...."

But then I realized that was an assumption rather than a known fact. Before I gave up on the project, perhaps I can move the gearbox upwards and not have problems... but how far?

So I would like to ask the experienced Kolbers: JUST EXACTLY HOW HIGH can the thrust line be on a Kolb Firestar 2 before it creates safety/handling/nose-over problems? Can the center of the propeller be 34 inches above the tailboom...36 inches...38 inches...40 inches????


Bill Berle
www.ezflaphandle.com  - safety & performance upgrade for light aircraft
www.grantstar.net           - winning proposals for non-profit and for-profit entities


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John Hauck



Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

PostPosted: Mon May 07, 2018 2:50 pm    Post subject: High Thrust Line Question Reply with quote

Larry C's Warp is a two blade.

john h
mkIII
Titus, Alabama



From: owner-kolb-list-server(at)matronics.com [mailto:owner-kolb-list-server(at)matronics.com] On Behalf Of Larry Cottrell
Sent: Monday, May 07, 2018 5:37 PM
To: kolb-list(at)matronics.com
Subject: Re: High Thrust Line Question


I'm swinging a 66 inch Warp with the gear box in the down position.
Larry

On Mon, May 7, 2018 at 4:21 PM, Bill Berle <victorbravo(at)sbcglobal.net (victorbravo(at)sbcglobal.net)> wrote:
--> Kolb-List message posted by: Bill Berle <victorbravo(at)sbcglobal.net (victorbravo(at)sbcglobal.net)>

Kolbers, I ran into a significant problem on my Firestar, and it may cause me to not be able to finish the project. I hope this is not as much of a problem as I fear.

When I bought my HKS engine I did not know to ask whether it had one type gearbox or another. It has the 3.47 to 1 box, which will spin a large propeller very slowly.

After reading some ot the Kolb List stories about high thrust lines and putting the Kolb over on its nose, I realized I wanted to keep the thrust line as low as possible for best performance and handling. However, with the gearbox rotated to the "down" position, it limited the propeller diameter to 64 inches with a one inch tailboom clearance. With the 3.47 gearbox I have, a three blade propeller with 62-64 inch diameter is not enough... the engine will overspeed before I get the full amount of thrust.

Someone suggested using a four or five blade propeller, but that would prevent the wings from folding back.

I contacted the engine distributor to ask if I could switch the gears around to make my gearbox a 2.58 to 1 ratio,a nd you cannot do that without changing the gearbox itself.

So I asked how much it would cost to buy a new gearbox, andit is way too high for me to consider doing right now. Maybe when I win the lottery.

Someone else suggested that I turn the gearbox around facing "up", which would allow a much larger propeller. My first reaction was "Oh goodness no, that will raise the thrust line too high, and it will cause the airplane to nose over on takeoff, I'll run out of elevator control, etc. etc...."

But then I realized that was an assumption rather than a known fact. Before I gave up on the project, perhaps I can move the gearbox upwards and not have problems... but how far?

So I would like to ask the experienced Kolbers: JUST EXACTLY HOW HIGH can the thrust line be on a Kolb Firestar 2 before it creates safety/handling/nose-over problems? Can the center of the propeller be 34 inches above the tailboom...36 inches...38 inches...40 inches????
Bill Berle
www.ezflaphandle.com - safety & performance upgrade for light aircraft
www.grantstar.net - winning proposals for non-profit and for-profit entities
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PostPosted: Mon May 07, 2018 3:04 pm    Post subject: High Thrust Line Question Reply with quote

On Mon, 5/7/18, Larry Cottrell <lcottrell1020(at)gmail.com> wrote:

I'm swinging a 66 inch Warp with the gear box in the down position.

With the 3.47 to 1 gearbox????


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John Hauck



Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

PostPosted: Mon May 07, 2018 3:15 pm    Post subject: High Thrust Line Question Reply with quote

I have run 72" props on my mkIII with 3/4" tail boom clearance. That puts the center of thrust 36.375" above the top of the tail boom.

If the engine overpowers the elevator, come back on the power a bit. Doesn't take much to get a Kolb off the ground. Soon as you get some airspeed, go back to full throttle. I had to do that initially, when I upgraded from an 80 to a 100 hp 912.

Kolbers that let the Kolb nose over on takeoff need to learn how to fly the airplane. I don't dump the throttle on takeoff. Be gentle and it will do what you want it too.

Go to longer main gear legs to put the nose up and put more weight on the tail wheel.

These are things I have done over the years with my Kolbs. Not recommending anyone else follow suit.

john h
mkIII
Titus, Alabama


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PostPosted: Mon May 07, 2018 3:56 pm    Post subject: High Thrust Line Question Reply with quote

THANK YOU John H, I appreciate the experience you have shared.

I have already put very tall Slingshot gear legs on my Firestar to get the nose up, and larger tires on top of that. I measured 32 inches from the edge of the "socket" tube on the fuselage down the gear leg, around the bend, and down to the axle, making this possibly the "tallest" Firestar out there. It sure looks like a STOL airplane Smile

I am also looking at photos and videos of Firestars and MK 3's, noticing how far above the wing the thrust line is. I even watched the 20 year old Kolb promotional ideo with a young John H flying the Slingshot Smile It APPEARS from those videos that my thrust line with the gearbox turned "up" should fall within those dimensions.

Since turning the gearbox around doesn't cost anything, and since I really would like to keep the Kolb and continue getting it in the air, it looks like I will try this first and see. So I'll sell all my other airplane junk instead, and use that money to finish the Kolb Smile

Anyone need an A-65 engine or a nice Avid Flyer B model airframe?

Bill Berle
www.ezflaphandle.com  - safety & performance upgrade for light aircraft
www.grantstar.net           - winning proposals for non-profit and for-profit entities

--------------------------------------------
On Mon, 5/7/18, John Hauck <jhauck(at)elmore.rr.com> wrote:

Subject: RE: High Thrust Line Question
To: kolb-list(at)matronics.com
Date: Monday, May 7, 2018, 4:14 PM


Hauck" <jhauck(at)elmore.rr.com>

I have run 72" props on my mkIII with
3/4" tail boom clearance.  That puts the center of
thrust 36.375" above the top of the tail boom.

If the engine overpowers the elevator,
come back on the power a bit.  Doesn't take much to get
a Kolb off the ground.  Soon as you get some airspeed,
go back to full throttle.  I had to do that initially,
when I upgraded from an 80 to a 100 hp 912.

Kolbers that let the Kolb nose over on
takeoff need to learn how to fly the airplane.  I don't
dump the throttle on takeoff.  Be gentle and it will do
what you want it too.

Go to longer main gear legs to put the
nose up and put more weight on the tail wheel.

These are things I have done over the
years with my Kolbs.  Not recommending anyone else
follow suit.

john h
mkIII
Titus, Alabama




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lcottrell



Joined: 29 May 2006
Posts: 1490
Location: Jordan Valley, Or

PostPosted: Mon May 07, 2018 4:47 pm    Post subject: High Thrust Line Question Reply with quote

I don't know for sure what gear box, but whatever, the location of the propeller shaft shouldn't change. Why don't you call Daryl at Warp and tell him what you have and what he recommends. John turned me on to him and he hasn't done me or anyone that I know of, wrong.Larry
On Mon, May 7, 2018 at 5:02 PM, Bill Berle <victorbravo(at)sbcglobal.net (victorbravo(at)sbcglobal.net)> wrote:
Quote:
--> Kolb-List message posted by: Bill Berle <victorbravo(at)sbcglobal.net (victorbravo(at)sbcglobal.net)>

On Mon, 5/7/18, Larry Cottrell <lcottrell1020(at)gmail.com (lcottrell1020(at)gmail.com)> wrote:

  I'm swinging a 66  inch Warp with the gear box in the down position.

With the 3.47 to 1 gearbox????
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PostPosted: Mon May 07, 2018 6:49 pm    Post subject: High Thrust Line Question Reply with quote

With the propeller shaft in the SAME "down" position, the 3.47 gearbox I have will make the propeller turn at 1671 RPM at theax. coninuous power of 5800 engine RPM. At "cruise" RPM it will turn even slower. With the 2.58 gearbox that I suspect you have, your propeller will turn almost 2250 at 5800 engine RPM.

So with those numbers, in order to get the same thrust (and absorb the same 60 horsepower and torque from the HKS) I would need a whole lot more propeller blade area than you would need. Usually you can just put on a 4 blade prop or 5 blade, and that will do the trick. But with a Kolb you can't do it and still fold the wings.

Putting on a much wider chord propeller blade (a paddle prop that looks like a T-28 warbird) could work, but again in this case the prop blades would hit the rear of the wing when folded.

HKS says the gearbox will take almost $2000 to buy, plus some special tools they would rent me, and however much time from a qualified mechanic familiar with these engines. Plus the use of a hydraulic shop press. That is not gonna work in my current situation, and so I briefly considered selling everything I had, engine, airframe, etc. and starting over with another option. But now I have myself calmed down a little and am not throwing wrenches across the shop cursing Smile

So before I do anything rash, I want to figure out whether the "up" position of the gearbox is a minor problem or a huge problem. I know that "down" is the preference, but that cannot happen because I have the wrong gearbox.

I will be HAPPY to call Warp Drive and ask them, he may have some magic wand that the other prop manufacturers don't have.

Bill Berle
www.ezflaphandle.com  - safety & performance upgrade for light aircraft
www.grantstar.net           - winning proposals for non-profit and for-profit entities

--------------------------------------------
On Mon, 5/7/18, Larry Cottrell <lcottrell1020(at)gmail.com> wrote:

Subject: Re: High Thrust Line Question
To: "kolb-list(at)matronics.com" <kolb-list(at)matronics.com>
Date: Monday, May 7, 2018, 5:45 PM

I don't know for
sure what gear box, but whatever, the location of the
propeller shaft shouldn't change. Why don't you call
Daryl at Warp and tell him what you have and what he
recommends. John turned me on to him and he hasn't done
me or anyone that I know of,
wrong.Larry
On Mon, May 7, 2018 at
5:02 PM, Bill Berle <victorbravo(at)sbcglobal.net>
wrote:

Bill Berle <victorbravo(at)sbcglobal.net>



On Mon, 5/7/18, Larry Cottrell <lcottrell1020(at)gmail.com>
wrote:



  I'm swinging a 66  inch Warp with the gear box in
the down position.



With the 3.47 to 1 gearbox????

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intolerant of others.
If you forward this email, or any part of
it, please remove my email address before sending.


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George Alexander



Joined: 10 Jan 2006
Posts: 245
Location: SW Florida

PostPosted: Tue May 08, 2018 4:39 am    Post subject: Re: High Thrust Line Question Reply with quote

victorbravo(at)sbcglobal. wrote:
S- N- I- P

With the 3.47 gearbox I have, a three blade propeller with 62-64 inch diameter is not enough... the engine will overspeed before I get the full amount of thrust.

S- N- I- P
Bill Berle
S- N- I- P


MY FS II is equipped with R503 DCDI, a C Box 3.47 - 1, mounted in the "Up" position and swinging a 68", 3 blade Powerfin 'F' model prop.
In a couple of hundred hours, have encountered none of the problems you identified as potential ones.


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rickofudall



Joined: 19 Sep 2009
Posts: 1392
Location: Udall, KS, USA

PostPosted: Tue May 08, 2018 5:09 am    Post subject: High Thrust Line Question Reply with quote

Don't bother wasting your time calling Darryl. He'll tell you that the gearbox won't work, blah, blah, blah. Horse exhaust. He told me that the 4 to 1 gearbox I run with a 582 was all wrong. Funny thing though, when I had a 582 in the shop with a 2.57 gearbox I started swapping props between the two. I had to put about 20 minutes (yeah, 1/3 of a degree) more pitch on the 4 to 1 engine. Otherwise, performance was the same. For what it's worth, the R3350's of the B29 turned the prop at a bit over 900 rpm.Suggest you leave the gearbox in the up position and put the short side up on the front engine mount and put the rear mounts long side up.
Don't know if it will transfer from the Mk III but the lower prop rpm allows me to run a rudder trim tab that's about 1/3 the size of the factory recommended tab and the total deflection angle is only about 5 degrees. I need a tiny amount of right rudder on takeoff and a bit of left rudder in cruise.
As for running a four or five blade prop, I have run a three blade Warp and a four blade Power Fin on my HKS. No difference when set right. I even stripped the Power Fin back to two blades. It vibrated a bit more and made virtually no difference so I put the other two blades back in.
If you think your thrust line is high, look at the pics. Travis told me the factory set this engine up for the fourth owner of the PFH (plane from hell) who just had to have an "E" gearbox.
Your HKS will power your Firestar just fine, your prop will work just fine.
I set my HKS so that the prop tops out at 6000 rpm on climb out.
Rick
On Mon, May 7, 2018 at 9:46 PM, Bill Berle <victorbravo(at)sbcglobal.net (victorbravo(at)sbcglobal.net)> wrote:
Quote:
--> Kolb-List message posted by: Bill Berle <victorbravo(at)sbcglobal.net (victorbravo(at)sbcglobal.net)>

With the propeller shaft in the SAME "down" position, the 3.47 gearbox I have will make the propeller turn at 1671 RPM at theax. coninuous power of 5800 engine RPM. At "cruise" RPM it will turn even slower. With the 2.58 gearbox that I suspect you have, your propeller will turn almost 2250 at 5800 engine RPM.

So with those numbers, in order to get the same thrust (and absorb the same 60 horsepower and torque from the HKS) I would need a whole lot more propeller blade area than you would need. Usually you can just put on a 4 blade prop or 5 blade, and that will do the trick. But with a Kolb you can't do it and still fold the wings.

Putting on a much wider chord propeller blade (a paddle prop that looks like a T-28 warbird) could work, but again in this case the prop blades would hit the rear of the wing when folded.

HKS says the gearbox will take almost $2000 to buy,  plus some special tools they would rent me, and however much time from a qualified mechanic familiar with these engines. Plus the use of a hydraulic shop press. That is not gonna work in my current situation, and so I briefly considered selling everything I had, engine, airframe, etc. and starting over with another option. But now I have myself calmed down a little and am not throwing wrenches across the shop cursing Smile

So before I do anything rash, I want to figure out whether the "up" position of the gearbox is a minor problem or a huge problem. I know that "down" is the preference, but that cannot happen because I have the wrong gearbox.

I will be HAPPY to call Warp Drive and ask them, he may have some magic wand that the other prop manufacturers don't have.

Bill Berle
www.ezflaphandle.com  - safety & performance upgrade for light aircraft
www.grantstar.net           - winning proposals for non-profit and for-profit entities

--------------------------------------------
On Mon, 5/7/18, Larry Cottrell <lcottrell1020(at)gmail.com (lcottrell1020(at)gmail.com)> wrote:

 Subject: Re: High Thrust Line Question
 To: "kolb-list(at)matronics.com (kolb-list(at)matronics.com)" <kolb-list(at)matronics.com (kolb-list(at)matronics.com)>
 Date: Monday, May 7, 2018, 5:45 PM
 
 I don't know for
 sure what gear box, but whatever, the location of the
 propeller shaft shouldn't change. Why don't you call
 Daryl at Warp and tell him what you have and what he
 recommends. John turned me on to him and he hasn't done
 me or anyone that I know of,
 wrong.Larry
 On Mon, May 7, 2018 at
 5:02 PM, Bill Berle <victorbravo(at)sbcglobal.net (victorbravo(at)sbcglobal.net)>
 wrote:
 --> Kolb-List message posted by:
 Bill Berle <victorbravo(at)sbcglobal.net (victorbravo(at)sbcglobal.net)>



 On Mon, 5/7/18, Larry Cottrell <lcottrell1020(at)gmail.com (lcottrell1020(at)gmail.com)>
 wrote:



   I'm swinging a 66  inch Warp with the gear box in
 the down position.



 With the 3.47 to 1 gearbox????

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 older I get, the less tolerant I am of those who are
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rickofudall



Joined: 19 Sep 2009
Posts: 1392
Location: Udall, KS, USA

PostPosted: Tue May 08, 2018 5:19 am    Post subject: High Thrust Line Question Reply with quote

PS, the other benefit of lower prop rpm is that your airplane will be a whole lot more quiet. My neighbors told me they could hear the 2.57 gearbox engine all the way around the pattern, but the 4.00 gearbox was below hearing level when the plane was on downwind.

Rick
On Tue, May 8, 2018 at 8:08 AM, Richard Girard <aslsa.rng(at)gmail.com (aslsa.rng(at)gmail.com)> wrote:
Quote:
Don't bother wasting your time calling Darryl. He'll tell you that the gearbox won't work, blah, blah, blah. Horse exhaust. He told me that the 4 to 1 gearbox I run with a 582 was all wrong. Funny thing though, when I had a 582 in the shop with a 2.57 gearbox I started swapping props between the two. I had to put about 20 minutes (yeah, 1/3 of a degree) more pitch on the 4 to 1 engine. Otherwise, performance was the same. For what it's worth, the R3350's of the B29 turned the prop at a bit over 900 rpm.Suggest you leave the gearbox in the up position and put the short side up on the front engine mount and put the rear mounts long side up.
Don't know if it will transfer from the Mk III but the lower prop rpm allows me to run a rudder trim tab that's about 1/3 the size of the factory recommended tab and the total deflection angle is only about 5 degrees. I need a tiny amount of right rudder on takeoff and a bit of left rudder in cruise.
As for running a four or five blade prop, I have run a three blade Warp and a four blade Power Fin on my HKS. No difference when set right. I even stripped the Power Fin back to two blades. It vibrated a bit more and made virtually no difference so I put the other two blades back in.
If you think your thrust line is high, look at the pics. Travis told me the factory set this engine up for the fourth owner of the PFH (plane from hell) who just had to have an "E" gearbox.
Your HKS will power your Firestar just fine, your prop will work just fine.
I set my HKS so that the prop tops out at 6000 rpm on climb out.
Rick
On Mon, May 7, 2018 at 9:46 PM, Bill Berle <victorbravo(at)sbcglobal.net (victorbravo(at)sbcglobal.net)> wrote:
Quote:
--> Kolb-List message posted by: Bill Berle <victorbravo(at)sbcglobal.net (victorbravo(at)sbcglobal.net)>

With the propeller shaft in the SAME "down" position, the 3.47 gearbox I have will make the propeller turn at 1671 RPM at theax. coninuous power of 5800 engine RPM. At "cruise" RPM it will turn even slower. With the 2.58 gearbox that I suspect you have, your propeller will turn almost 2250 at 5800 engine RPM.

So with those numbers, in order to get the same thrust (and absorb the same 60 horsepower and torque from the HKS) I would need a whole lot more propeller blade area than you would need. Usually you can just put on a 4 blade prop or 5 blade, and that will do the trick. But with a Kolb you can't do it and still fold the wings.

Putting on a much wider chord propeller blade (a paddle prop that looks like a T-28 warbird) could work, but again in this case the prop blades would hit the rear of the wing when folded.

HKS says the gearbox will take almost $2000 to buy,  plus some special tools they would rent me, and however much time from a qualified mechanic familiar with these engines. Plus the use of a hydraulic shop press. That is not gonna work in my current situation, and so I briefly considered selling everything I had, engine, airframe, etc. and starting over with another option. But now I have myself calmed down a little and am not throwing wrenches across the shop cursing Smile

So before I do anything rash, I want to figure out whether the "up" position of the gearbox is a minor problem or a huge problem. I know that "down" is the preference, but that cannot happen because I have the wrong gearbox.

I will be HAPPY to call Warp Drive and ask them, he may have some magic wand that the other prop manufacturers don't have.

Bill Berle
www.ezflaphandle.com  - safety & performance upgrade for light aircraft
www.grantstar.net           - winning proposals for non-profit and for-profit entities

--------------------------------------------
On Mon, 5/7/18, Larry Cottrell <lcottrell1020(at)gmail.com (lcottrell1020(at)gmail.com)> wrote:

 Subject: Re: High Thrust Line Question
 To: "kolb-list(at)matronics.com (kolb-list(at)matronics.com)" <kolb-list(at)matronics.com (kolb-list(at)matronics.com)>
 Date: Monday, May 7, 2018, 5:45 PM
 
 I don't know for
 sure what gear box, but whatever, the location of the
 propeller shaft shouldn't change. Why don't you call
 Daryl at Warp and tell him what you have and what he
 recommends. John turned me on to him and he hasn't done
 me or anyone that I know of,
 wrong.Larry
 On Mon, May 7, 2018 at
 5:02 PM, Bill Berle <victorbravo(at)sbcglobal.net (victorbravo(at)sbcglobal.net)>
 wrote:
 --> Kolb-List message posted by:
 Bill Berle <victorbravo(at)sbcglobal.net (victorbravo(at)sbcglobal.net)>



 On Mon, 5/7/18, Larry Cottrell <lcottrell1020(at)gmail.com (lcottrell1020(at)gmail.com)>
 wrote:



   I'm swinging a 66  inch Warp with the gear box in
 the down position.



 With the 3.47 to 1 gearbox????

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Richard Pike



Joined: 09 Jan 2006
Posts: 1669
Location: Blountville, Tennessee

PostPosted: Tue May 08, 2018 3:38 pm    Post subject: Re: High Thrust Line Question Reply with quote

Bill; notice the extent to which Rick raised his engine. (Great pictures) Maybe you can leave the gearbox down and raise the engine up?

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PostPosted: Tue May 08, 2018 7:09 pm    Post subject: High Thrust Line Question Reply with quote

Everybody THANK YOU for taking time for this discussion.

I spoke to the Kolb factory today by phone, and went out to the local UL flying field to see an HKS engine run.

Duane and Bryan at Kolb were asked one specific question by me: What is the maximum number of inches allowable or advisable between the center of the propeller and the top of the tailboom?

Bryan said that 36 inches is about standard for a "normal" Firestar, and he would not want to fly an airplane with that distance raised to 39 or 40 inches.

I went back to my hangar and measured, and the distance on my Firestar would be over 40 or 41 inches if I turned the gearbox upward. So if the Kolb factory owner says 40 inches is too high, I can only be humble and assume that I wouldn't want to fly it at 40 inches either. If any of the highly experienced Kolbers on this forum are flying with their thrust line 40 inches above the tailboom, I REALLY would like to know about it pronto.

As big of an ego as I have had a few times in my life, and as much as I think of myself as a reasonably skilled pilot, I don't need to be a test pilot here and try to push any envelope at this early stage. So if I can ask the Kolb ilst a favor... if any of you are flying a Firestar with the engine thrust line 39 or 40 or 41 incvhes above the tailboom please post this on the list and let me know ifyou have any issues with the handling, pitch-over, etc.

Bill Berle
www.ezflaphandle.com  - safety & performance upgrade for light aircraft
www.grantstar.net           - winning proposals for non-profit and for-profit entities

--------------------------------------------
On Tue, 5/8/18, Richard Pike <thegreybaron(at)charter.net> wrote:

Subject: Re: High Thrust Line Question
To: kolb-list(at)matronics.com
Date: Tuesday, May 8, 2018, 4:38 PM


Pike" <thegreybaron(at)charter.net>

Bill; notice the extent to which Rick
raised his engine. (Great pictures) Maybe you can leave the
gearbox down and raise the engine up?

--------
Richard Pike
Kolb MKIII N420P (420ldPoops)
Kingsport, TN 3TN0

Forgiving is tough, being forgiven is
wonderful, and God's grace really is amazing.




Read this topic online here:

http://forums.matronics.com/viewtopic.php?p=479963#479963






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John Hauck



Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

PostPosted: Tue May 08, 2018 7:22 pm    Post subject: High Thrust Line Question Reply with quote

I am certainly not an aeronautical engineer by any means, but I realize that the higher the thrust line the more power it takes to fly. That long arm/lever is doing a good job of pushing the nose down, the elevators are working hard to keep the nose up, and that all takes power. Eventually the high thrust line would probably consume the aircraft.

I mentioned a day or so ago a major difference from flying my mkIII with an 80 hp and then making my first takeoff with the 100 hp. It wouldn't break ground until I came back on the power. In a short time muscle memory took care of that little problem, but it was a good demonstration to me how much a high thrust line consumes power.

Some things work and some don't.

john h
mkIII
Titus, Alabama


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PostPosted: Wed May 09, 2018 8:41 am    Post subject: High Thrust Line Question Reply with quote

Well Bill, thanks for bringing up the topic. I replaced my little Rotax 377 with new low rpm Hirth 2702 over the winter. I really hadn’t measured the distance between the prop hub and boom tube. You sparked my interest so I stopped by my hanger this morning to check it out. The Hirth uses a G50 gearbox with 2:29 to 1 ratio. which translates to 2400 rpm prop speed (at) the engine’s max. HP rpm of 5500rpm.
Anyway, it measures 35.5 inches. This is on a Kolb original Firestar. I did have to move the engine forward 2.625” to compensate for the extra weight of the new gear box. I went with a 64” 3 blade Powerfin prop set at 6.4 degrees of pitch. This setup gives me 3.5” of clearance from the boom tube. Thanks for inspiring me to check it out. I’m sure there is a good combination of prop out there for an HKS.
George Helton
1986 Firestar, FS100
14GDH
Mesick, Michigan
gdhelton(at)gmail.com

Sent from my iPhone

Quote:
On May 8, 2018, at 11:08 PM, Bill Berle <victorbravo(at)sbcglobal.net> wrote:



Everybody THANK YOU for taking time for this discussion.

I spoke to the Kolb factory today by phone, and went out to the local UL flying field to see an HKS engine run.

Duane and Bryan at Kolb were asked one specific question by me: What is the maximum number of inches allowable or advisable between the center of the propeller and the top of the tailboom?

Bryan said that 36 inches is about standard for a "normal" Firestar, and he would not want to fly an airplane with that distance raised to 39 or 40 inches.

I went back to my hangar and measured, and the distance on my Firestar would be over 40 or 41 inches if I turned the gearbox upward. So if the Kolb factory owner says 40 inches is too high, I can only be humble and assume that I wouldn't want to fly it at 40 inches either. If any of the highly experienced Kolbers on this forum are flying with their thrust line 40 inches above the tailboom, I REALLY would like to know about it pronto.

As big of an ego as I have had a few times in my life, and as much as I think of myself as a reasonably skilled pilot, I don't need to be a test pilot here and try to push any envelope at this early stage. So if I can ask the Kolb ilst a favor... if any of you are flying a Firestar with the engine thrust line 39 or 40 or 41 incvhes above the tailboom please post this on the list and let me know ifyou have any issues with the handling, pitch-over, etc.

Bill Berle
www.ezflaphandle.com - safety & performance upgrade for light aircraft
www.grantstar.net - winning proposals for non-profit and for-profit entities

--------------------------------------------
On Tue, 5/8/18, Richard Pike <thegreybaron(at)charter.net> wrote:

Subject: Re: High Thrust Line Question
To: kolb-list(at)matronics.com
Date: Tuesday, May 8, 2018, 4:38 PM


Pike" <thegreybaron(at)charter.net>

Bill; notice the extent to which Rick
raised his engine. (Great pictures) Maybe you can leave the
gearbox down and raise the engine up?

--------
Richard Pike
Kolb MKIII N420P (420ldPoops)
Kingsport, TN 3TN0

Forgiving is tough, being forgiven is
wonderful, and God's grace really is amazing.




Read this topic online here:

http://forums.matronics.com/viewtopic.php?p=479963#479963






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John Hauck



Joined: 09 Jan 2006
Posts: 4639
Location: Titus, Alabama (hauck's holler)

PostPosted: Wed May 09, 2018 10:17 am    Post subject: High Thrust Line Question Reply with quote

3.5" is about 2.5" to much. 1" clearance operating with stand Lord Mounts is more than adequate clearance. I flew with a 72" prop and .75" clearance for many hours, including my last 48 day flight to Alaska and back. Prop might be noisier with the tips passing that close to the tail boom, but I'll take the lower thrust line over noise.

I'm flying with a 68" prop that gives me 2.75" of clearance. Can't tell the difference in noise level. It is still noisy.

john h
mkIII
Titus, Alabama


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PostPosted: Wed May 09, 2018 10:19 am    Post subject: High Thrust Line Question Reply with quote

I have been pulling out what's left of my hair over this issue. I really don't want to quit, I LIKE the Kolb airframe and it will fit my mission well. I like the HKS fuel economy and improved reliability. I just wound up with the wrong gearbox on it and cannot afford to change it.

What I have learned thus far is:

1) My 3.47 to 1 gearbox really wants to swing a larger propeller than what is actually "correct" for the height of the thrust line on the Kolb airframe.

2) Turning the gearbox upwards will solve the prop diameter problem, but it creates a thrust line that is higher than the Kolb factory thinks is advisable.

3) I could easily go to a 4 or 5 blade propeller, solves the gearbox AND thrust line problems, but that interferes with folding the wings.

I have considered many possible solutions or "work-arounds" :

1) Get a 5 blade propeller and remove it after every flight, which would allow ALL of the problems to be solved, at the cost of additional time and effort every time I fly. This will cost the least of all the "solutions".

2) Remove the wings after every flight instead of folding the wings. This allows a 5 blade propeller to be used but adds complexity and requires me to build a complicated ground fixture to allow the wings to be removed and installed by myself alone.

3) Make a folding propeller, like the electric R/C model gliders have, where the blades fold rearward. This solves all of the problems, no complex ground equipment, but designing and manufacturing such a propeller will be prohibitvely expensive.

4) Buy another gearbox from HKS. This is the best solution mechanically, but I cannot afford it.

5) Turn the gearbox upwards, install the right propeller, and live with the possibly dangerous or funky flight handling of the airplane.

Any other/better/wiser/workable ideas from the Kolb List are very very welcome!


Bill Berle
www.ezflaphandle.com  - safety & performance upgrade for light aircraft
www.grantstar.net           - winning proposals for non-profit and for-profit entities

--------------------------------------------
On Wed, 5/9/18, George Helton <gdhelton(at)gmail.com> wrote:

Subject: Re: Re: High Thrust Line Question
To: kolb-list(at)matronics.com
Date: Wednesday, May 9, 2018, 9:39 AM


Helton <gdhelton(at)gmail.com>

Well Bill, thanks for bringing up the
topic. I replaced my little Rotax 377 with new low rpm Hirth
2702 over the winter. I really hadn’t measured the
distance between the prop hub and boom tube. You sparked my
interest so I stopped by my hanger this morning to check it
out. The Hirth uses a G50 gearbox with 2:29 to 1 ratio.
which translates to 2400 rpm prop speed (at) the engine’s
max. HP rpm of 5500rpm.
Anyway, it measures 35.5 inches. This
is on a Kolb original Firestar. I did have to move the
engine forward 2.625” to compensate for the extra weight
of the new gear box. I went with a 64” 3 blade Powerfin
prop set at 6.4 degrees of pitch. This setup gives me 3.5”
of clearance from the boom tube. Thanks for inspiring me to
check it out.  I’m sure there is a good combination
of prop out there for an HKS.
George Helton
1986 Firestar, FS100
14GDH
Mesick, Michigan
gdhelton(at)gmail.com

Sent from my iPhone

> On May 8, 2018, at 11:08 PM, Bill
Berle <victorbravo(at)sbcglobal.net>
wrote:
>
> --> Kolb-List message posted
by: Bill Berle <victorbravo(at)sbcglobal.net>
>
> Everybody THANK YOU for taking
time for this discussion.
>
> I spoke to the Kolb factory today
by phone, and went out to the local UL flying field to see
an HKS engine run.
>
> Duane and Bryan at Kolb were asked
one specific question by me:  What is the maximum
number of inches allowable or advisable between the center
of the propeller and the top of the tailboom?
>
> Bryan said that 36 inches is about
standard for a "normal" Firestar, and he would not want to
fly an airplane with that distance raised to 39 or 40
inches.
>
> I went back to my hangar and
measured, and the distance on my Firestar would be over 40
or 41 inches if I turned the gearbox upward. So if the Kolb
factory owner says 40 inches is too high, I can only be
humble and assume that I wouldn't want to fly it at 40
inches either. If any of the highly experienced Kolbers on
this forum are flying with their thrust line 40 inches above
the tailboom, I REALLY would like to know about it pronto.
>
> As big of an ego as I have had a
few times in my life, and as much as I think of myself as a
reasonably  skilled pilot, I don't need to be a test
pilot here and try to push any envelope at this early stage.
So if I can ask the Kolb ilst a favor... if any of you are
flying a Firestar with the engine thrust line 39 or 40 or 41
incvhes above the tailboom please post this on the list and
let me know ifyou have any issues with the handling,
pitch-over, etc.
>
> Bill Berle
> www.ezflaphandle.com  -
safety & performance upgrade for light aircraft
> www.grantstar.net   
      - winning proposals for non-profit and
for-profit entities
>
>
--------------------------------------------
> On Tue, 5/8/18, Richard Pike
<thegreybaron(at)charter.net>
wrote:
>
> Subject: Re: High
Thrust Line Question
> To: kolb-list(at)matronics.com
> Date: Tuesday, May 8, 2018, 4:38
PM
>
> --> Kolb-List message posted
by: "Richard
> Pike" <thegreybaron(at)charter.net>
>
> Bill; notice the extent to which
Rick
> raised his engine. (Great
pictures) Maybe you can leave the
> gearbox down and raise the engine
up?
>
> --------
> Richard Pike
> Kolb MKIII N420P (420ldPoops)
> Kingsport, TN 3TN0
>
> Forgiving is tough, being forgiven
is
> wonderful, and God's grace really
is amazing.
>
>
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=479963#479963
>
>
>
>
>
>
> The Kolb-List Email Forum -
> Navigator to browse
> List Un/Subscription,
> 7-Day Browse, Chat, FAQ,
>      - MATRONICS
WEB FORUMS -
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WIKI -
> Email List Wiki!
>    - List Contribution
Web Site -
> support!
>         
     
>    -Matt Dralle, List
Admin.
>
>
>
>
>
>
>
>

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PostPosted: Wed May 09, 2018 10:38 am    Post subject: High Thrust Line Question Reply with quote

Bill, I know that this might sound crazy but, can’t you just buy a different set of gears for the gearbox? Being a mechanic may be a benefit here but I can’t imagine that HKS can’t supply replacement parts. The gearbox case doesn’t care what gears fit inside of it.
If they don’t, I’d sure shy away from buying one.
George Helton
1986 Firestar, FS100
14GDH
Mesick, Michigan
gdhelton(at)gmail.com

Sent from my iPhone

Quote:
On May 9, 2018, at 2:18 PM, Bill Berle <victorbravo(at)sbcglobal.net> wrote:



I have been pulling out what's left of my hair over this issue. I really don't want to quit, I LIKE the Kolb airframe and it will fit my mission well. I like the HKS fuel economy and improved reliability. I just wound up with the wrong gearbox on it and cannot afford to change it.

What I have learned thus far is:

1) My 3.47 to 1 gearbox really wants to swing a larger propeller than what is actually "correct" for the height of the thrust line on the Kolb airframe.

2) Turning the gearbox upwards will solve the prop diameter problem, but it creates a thrust line that is higher than the Kolb factory thinks is advisable.

3) I could easily go to a 4 or 5 blade propeller, solves the gearbox AND thrust line problems, but that interferes with folding the wings.

I have considered many possible solutions or "work-arounds" :

1) Get a 5 blade propeller and remove it after every flight, which would allow ALL of the problems to be solved, at the cost of additional time and effort every time I fly. This will cost the least of all the "solutions".

2) Remove the wings after every flight instead of folding the wings. This allows a 5 blade propeller to be used but adds complexity and requires me to build a complicated ground fixture to allow the wings to be removed and installed by myself alone.

3) Make a folding propeller, like the electric R/C model gliders have, where the blades fold rearward. This solves all of the problems, no complex ground equipment, but designing and manufacturing such a propeller will be prohibitvely expensive.

4) Buy another gearbox from HKS. This is the best solution mechanically, but I cannot afford it.

5) Turn the gearbox upwards, install the right propeller, and live with the possibly dangerous or funky flight handling of the airplane.

Any other/better/wiser/workable ideas from the Kolb List are very very welcome!




Bill Berle
www.ezflaphandle.com - safety & performance upgrade for light aircraft
www.grantstar.net - winning proposals for non-profit and for-profit entities

--------------------------------------------
On Wed, 5/9/18, George Helton <gdhelton(at)gmail.com> wrote:

Subject: Re: Re: High Thrust Line Question
To: kolb-list(at)matronics.com
Date: Wednesday, May 9, 2018, 9:39 AM


Helton <gdhelton(at)gmail.com>

Well Bill, thanks for bringing up the
topic. I replaced my little Rotax 377 with new low rpm Hirth
2702 over the winter. I really hadn’t measured the
distance between the prop hub and boom tube. You sparked my
interest so I stopped by my hanger this morning to check it
out. The Hirth uses a G50 gearbox with 2:29 to 1 ratio.
which translates to 2400 rpm prop speed (at) the engine’s
max. HP rpm of 5500rpm.
Anyway, it measures 35.5 inches. This
is on a Kolb original Firestar. I did have to move the
engine forward 2.625” to compensate for the extra weight
of the new gear box. I went with a 64” 3 blade Powerfin
prop set at 6.4 degrees of pitch. This setup gives me 3.5”
of clearance from the boom tube. Thanks for inspiring me to
check it out. I’m sure there is a good combination
of prop out there for an HKS.
George Helton
1986 Firestar, FS100
14GDH
Mesick, Michigan
gdhelton(at)gmail.com

Sent from my iPhone

> On May 8, 2018, at 11:08 PM, Bill
Berle <victorbravo(at)sbcglobal.net>
wrote:
>
> --> Kolb-List message posted
by: Bill Berle <victorbravo(at)sbcglobal.net>
>
> Everybody THANK YOU for taking
time for this discussion.
>
> I spoke to the Kolb factory today
by phone, and went out to the local UL flying field to see
an HKS engine run.
>
> Duane and Bryan at Kolb were asked
one specific question by me: What is the maximum
number of inches allowable or advisable between the center
of the propeller and the top of the tailboom?
>
> Bryan said that 36 inches is about
standard for a "normal" Firestar, and he would not want to
fly an airplane with that distance raised to 39 or 40
inches.
>
> I went back to my hangar and
measured, and the distance on my Firestar would be over 40
or 41 inches if I turned the gearbox upward. So if the Kolb
factory owner says 40 inches is too high, I can only be
humble and assume that I wouldn't want to fly it at 40
inches either. If any of the highly experienced Kolbers on
this forum are flying with their thrust line 40 inches above
the tailboom, I REALLY would like to know about it pronto.
>
> As big of an ego as I have had a
few times in my life, and as much as I think of myself as a
reasonably skilled pilot, I don't need to be a test
pilot here and try to push any envelope at this early stage.
So if I can ask the Kolb ilst a favor... if any of you are
flying a Firestar with the engine thrust line 39 or 40 or 41
incvhes above the tailboom please post this on the list and
let me know ifyou have any issues with the handling,
pitch-over, etc.
>
> Bill Berle
> www.ezflaphandle.com -
safety & performance upgrade for light aircraft
> www.grantstar.net
- winning proposals for non-profit and
for-profit entities
>
>
--------------------------------------------
> On Tue, 5/8/18, Richard Pike
<thegreybaron(at)charter.net>
wrote:
>
> Subject: Re: High
Thrust Line Question
> To: kolb-list(at)matronics.com
> Date: Tuesday, May 8, 2018, 4:38
PM
>
> --> Kolb-List message posted
by: "Richard
> Pike" <thegreybaron(at)charter.net>
>
> Bill; notice the extent to which
Rick
> raised his engine. (Great
pictures) Maybe you can leave the
> gearbox down and raise the engine
up?
>
> --------
> Richard Pike
> Kolb MKIII N420P (420ldPoops)
> Kingsport, TN 3TN0
>
> Forgiving is tough, being forgiven
is
> wonderful, and God's grace really
is amazing.
>
>
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=479963#479963
>
>
>
>
>
>
> The Kolb-List Email Forum -
> Navigator to browse
> List Un/Subscription,
> 7-Day Browse, Chat, FAQ,
> - MATRONICS
WEB FORUMS -
> via the Web Forums!
> - NEW MATRONICS LIST
WIKI -
> Email List Wiki!
> - List Contribution
Web Site -
> support!
>

> -Matt Dralle, List
Admin.
>
>
>
>
>
>
>
>

The Kolb-List Email Forum -
Navigator to browse
List Un/Subscription,
7-Day Browse, Chat, FAQ,
- MATRONICS WEB FORUMS -
via the Web Forums!
- NEW MATRONICS LIST WIKI -
Email List Wiki!
- List Contribution Web Site -
support!

-Matt Dralle, List Admin.










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Back to top
victorbravo(at)sbcglobal.
Guest





PostPosted: Wed May 09, 2018 11:56 am    Post subject: High Thrust Line Question Reply with quote

The replacement gear set does not fit into the same gearbox case. So unfortunately I cannot just buy two new gears and slide them into place.

BUT... I am making progress towards one of the other potential solutions. After consulting with an experienced aircraft structures and metallurgy engineer, I believe I can make a simple prop extension that is held on with one central nut (a great big nut !) and remove the propeller before folding the wings.

The key to doing this SAFELY is called the Belleville Spring, or Belleville Washer. It is a conical spring steel washer that becomes flat (like a regular washer) as it is tightened, providing a known, reliable tension/compression force over a reasonable range of installation torques.

This means that I can install the propeller, tighten the nut until the Belleville Washer is more or less flat, and be confident that there is plenty of tension/compression in the propeller mounting without having to use a torque wrench, elaborate bolt stretch charts, etc. etc. This also provides a much more convenient and error-proof option instead of havign to torque six propeller bolts and safety wire the bolts, install six Cotter Pins, etc.

All of this means I will be hopefully able to use a 4, 5, or 6 blade prop with the thrust line within Kolb's recommended distance from the tailboom.

The only downside is that Kolbers around the world will never stop making fun of me for turning a simple airplane into a major engineering project Smile

The HKS engine is a VERY good quality engine and I believe the other Kolb/HKS owners will agree they love the engine. If you wish to use this engine on a Kolb, don't hold my mis-adventures against the engine... just make darn sure you get the 2.58 gearbox !

Bill Berle
www.ezflaphandle.com  - safety & performance upgrade for light aircraft
www.grantstar.net           - winning proposals for non-profit and for-profit entities

--------------------------------------------
On Wed, 5/9/18, George Helton <gdhelton(at)gmail.com> wrote:

Subject: Re: Re: High Thrust Line Question
To: kolb-list(at)matronics.com
Date: Wednesday, May 9, 2018, 11:37 AM


Helton <gdhelton(at)gmail.com>

Bill, I know that this might sound
crazy but, can’t you just buy a different set of gears for
the gearbox? Being a mechanic may be a benefit here but I
can’t imagine that HKS can’t supply replacement parts.
The gearbox case doesn’t care what gears fit inside of it.

If they don’t, I’d sure shy away
from buying one.
George Helton
1986 Firestar, FS100
14GDH
Mesick, Michigan
gdhelton(at)gmail.com

Sent from my iPhone

> On May 9, 2018, at 2:18 PM, Bill
Berle <victorbravo(at)sbcglobal.net>
wrote:
>
> --> Kolb-List message posted
by: Bill Berle <victorbravo(at)sbcglobal.net>
>
> I have been pulling out what's
left of my hair over this issue. I really don't want to
quit, I LIKE the Kolb airframe and it will fit my mission
well. I like the HKS fuel economy and improved reliability.
I just wound up with the wrong gearbox on it and cannot
afford to change it.
>
> What I have learned thus far is:
>
> 1) My 3.47 to 1 gearbox really
wants to swing a larger propeller than what is
actually  "correct" for the height of the thrust line
on the Kolb airframe.
>
> 2) Turning the gearbox upwards
will solve the prop diameter problem, but it creates a
thrust line that is higher than the Kolb factory thinks is
advisable.
>
> 3) I could easily go to a 4 or 5
blade propeller, solves the gearbox AND thrust line
problems, but that interferes with folding the wings.
>
> I have considered many possible
solutions or "work-arounds" :
>
> 1) Get a 5 blade propeller and
remove it after every flight, which would allow ALL of the
problems to be solved, at the cost of additional time and
effort every time I fly. This will cost the least of all the
"solutions".
>
> 2) Remove the wings after every
flight instead of folding the wings. This allows a 5 blade
propeller to be used but adds complexity and requires me to
build a complicated ground fixture to allow the wings to be
removed and installed by myself alone.
>
> 3) Make a folding propeller, like
the electric R/C model gliders have, where the blades fold
rearward. This solves all of the problems, no complex ground
equipment, but designing and manufacturing such a propeller
will be prohibitvely expensive.
>
> 4) Buy another gearbox from HKS.
This is the best solution mechanically, but I cannot afford
it.
>
> 5) Turn the gearbox upwards,
install the right propeller, and live with the possibly
dangerous or funky flight handling of the airplane.
>
> Any other/better/wiser/workable
ideas from the Kolb List are very very welcome!
>
>
>
>
> Bill Berle
> www.ezflaphandle.com  -
safety & performance upgrade for light aircraft
> www.grantstar.net   
      - winning proposals for non-profit and
for-profit entities
>
>
--------------------------------------------
> On Wed, 5/9/18, George Helton
<gdhelton(at)gmail.com>
wrote:
>
> Subject: Re: Re: High
Thrust Line Question
> To: kolb-list(at)matronics.com
> Date: Wednesday, May 9, 2018, 9:39
AM
>
> --> Kolb-List message posted
by: George
> Helton <gdhelton(at)gmail.com>
>
> Well Bill, thanks for bringing up
the
> topic. I replaced my little Rotax
377 with new low rpm Hirth
> 2702 over the winter. I really
hadn’t measured the
> distance between the prop hub and
boom tube. You sparked my
> interest so I stopped by my hanger
this morning to check it
> out. The Hirth uses a G50 gearbox
with 2:29 to 1 ratio.
> which translates to 2400 rpm prop
speed (at) the engine’s
> max. HP rpm of 5500rpm.
> Anyway, it measures 35.5 inches.
This
> is on a Kolb original Firestar. I
did have to move the
> engine forward 2.625” to
compensate for the extra weight
> of the new gear box. I went with a
64” 3 blade Powerfin
> prop set at 6.4 degrees of pitch.
This setup gives me 3.5”
> of clearance from the boom tube.
Thanks for inspiring me to
> check it out.  I’m sure
there is a good combination
> of prop out there for an HKS.
> George Helton
> 1986 Firestar, FS100
> 14GDH
> Mesick, Michigan
> gdhelton(at)gmail.com
>
> Sent from my iPhone
>
>> On May 8, 2018, at 11:08 PM,
Bill
> Berle <victorbravo(at)sbcglobal.net>
> wrote:
>>
>> --> Kolb-List message
posted
> by: Bill Berle <victorbravo(at)sbcglobal.net>
>>
>> Everybody THANK YOU for
taking
> time for this discussion.
>>
>> I spoke to the Kolb factory
today
> by phone, and went out to the
local UL flying field to see
> an HKS engine run.
>>
>> Duane and Bryan at Kolb were
asked
> one specific question by me: 
What is the maximum
> number of inches allowable or
advisable between the center
> of the propeller and the top of
the tailboom?
>>
>> Bryan said that 36 inches is
about
> standard for a "normal" Firestar,
and he would not want to
> fly an airplane with that distance
raised to 39 or 40
> inches.
>>
>> I went back to my hangar and
> measured, and the distance on my
Firestar would be over 40
> or 41 inches if I turned the
gearbox upward. So if the Kolb
> factory owner says 40 inches is
too high, I can only be
> humble and assume that I wouldn't
want to fly it at 40
> inches either. If any of the
highly experienced Kolbers on
> this forum are flying with their
thrust line 40 inches above
> the tailboom, I REALLY would like
to know about it pronto.
>>
>> As big of an ego as I have had
a
> few times in my life, and as much
as I think of myself as a
> reasonably  skilled pilot, I
don't need to be a test
> pilot here and try to push any
envelope at this early stage.
> So if I can ask the Kolb ilst a
favor... if any of you are
> flying a Firestar with the engine
thrust line 39 or 40 or 41
> incvhes above the tailboom please
post this on the list and
> let me know ifyou have any issues
with the handling,
> pitch-over, etc.
>>
>> Bill Berle
>> www.ezflaphandle.com  -
> safety & performance upgrade
for light aircraft
>> www.grantstar.net 
>        -
winning proposals for non-profit and
> for-profit entities
>>
>>
>
--------------------------------------------
>> On Tue, 5/8/18, Richard Pike
> <thegreybaron(at)charter.net>
> wrote:
>>
>> Subject: Re: High
> Thrust Line Question
>> To: kolb-list(at)matronics.com
>> Date: Tuesday, May 8, 2018,
4:38
> PM
>>
>> --> Kolb-List message
posted
> by: "Richard
>> Pike" <thegreybaron(at)charter.net>
>>
>> Bill; notice the extent to
which
> Rick
>> raised his engine. (Great
> pictures) Maybe you can leave the
>> gearbox down and raise the
engine
> up?
>>
>> --------
>> Richard Pike
>> Kolb MKIII N420P (420ldPoops)
>> Kingsport, TN 3TN0
>>
>> Forgiving is tough, being
forgiven
> is
>> wonderful, and God's grace
really
> is amazing.
>>
>>
>>
>>
>> Read this topic online here:
>>
>> http://forums.matronics.com/viewtopic.php?p=479963#479963
>>
>>
>>
>>
>>
>>
>> The Kolb-List Email Forum -
>> Navigator to browse
>> List Un/Subscription,
>> 7-Day Browse, Chat, FAQ,
>>      -
MATRONICS
> WEB FORUMS -
>> via the Web Forums!
>>      - NEW
MATRONICS LIST
> WIKI -
>> Email List Wiki!
>>    - List
Contribution
> Web Site -
>> support!
>>       
 
>     
>>      -Matt
Dralle, List
> Admin.
>>
>>
>>
>>
>>
>>
>>
>>
>
> The Kolb-List Email Forum -
> Navigator to browse
> List Un/Subscription,
> 7-Day Browse, Chat, FAQ,
>      - MATRONICS
WEB FORUMS -
> via the Web Forums!
>    - NEW MATRONICS LIST
WIKI -
> Email List Wiki!
>    - List Contribution
Web Site -
> support!
>         
     
>    -Matt Dralle, List
Admin.
>
>
>
>
>
>
>
>

The Kolb-List Email Forum -
Navigator to browse
List Un/Subscription,
7-Day Browse, Chat, FAQ,
    - MATRONICS WEB FORUMS -
via the Web Forums!
    - NEW MATRONICS LIST WIKI -
Email List Wiki!
  - List Contribution Web Site -
support!
               
    -Matt Dralle, List Admin.


- The Matronics Kolb-List Email Forum -
 

Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

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Back to top
Jack B Hart



Joined: 22 Feb 2018
Posts: 11
Location: Winchester, IN

PostPosted: Wed May 09, 2018 12:32 pm    Post subject: High Thrust Line Question Reply with quote

Bill,

If you are worried about the effects of a high thrust line, you may want to consider adding some area to your horizontal stabilizer. This should reduce some of the increased stick forces and tail work load.

Jack B. Hart FF004
Winchester, IN



From: "Bill Berle" <victorbravo(at)sbcglobal.net> Sent: Wednesday, May 9, 2018 3:58 PM To: kolb-list(at)matronics.com Subject: Re: Re: High Thrust Line Question
--> Kolb-List message posted by: Bill Berle <victorbravo(at)sbcglobal.net> The replacement gear set does not fit into the same gearbox case. So unfortunately I cannot just buy two new gears and slide them into place. BUT... I am making progress towards one of the other potential solutions. After consulting with an experienced aircraft structures and metallurgy engineer, I believe I can make a simple prop extension that is held on with one central nut (a great big nut !) and remove the propeller before folding the wings. The key to doing this SAFELY is called the Belleville Spring, or Belleville Washer. It is a conical spring steel washer that becomes flat (like a regular washer) as it is tightened, providing a known, reliable tension/compression force over a reasonable range of installation torques. This means that I can install the propeller, tighten the nut until the Belleville Washer is more or less flat, and be confident that there is plenty of tension/compression in the propeller mounting without having to use a torque wrench, elaborate bolt stretch charts, etc. etc. This also provides a much more convenient and error-proof option instead of havign to torque six propeller bolts and safety wire the bolts, install six Cotter Pins, etc. All of this means I will be hopefully able to use a 4, 5, or 6 blade prop with the thrust line within Kolb's recommended distance from the tailboom. The only downside is that Kolbers around the world will never stop making fun of me for turning a simple airplane into a major engineering project Smile The HKS engine is a VERY good quality engine and I believe the other Kolb/HKS owners will agree they love the engine. If you wish to use this engine on a Kolb, don't hold my mis-adventures against the engine... just make darn sure you get the 2.58 gearbox ! Bill Berle www.ezflaphandle.com - safety & performance upgrade for light aircraft www.grantstar.net - winning proposals for non-profit and for-profit entities -------------------------------------------- On Wed, 5/9/18, George Helton <gdhelton(at)gmail.com> wrote: Subject: Re: Re: High Thrust Line Question To: kolb-list(at)matronics.com Date: Wednesday, May 9, 2018, 11:37 AM --> Kolb-List message posted by: George Helton <gdhelton(at)gmail.com> Bill, I know that this might sound crazy but, can&rsquo;t you just buy a different set of gears for the gearbox? Being a mechanic may be a benefit here but I can&rsquo;t imagine that HKS can&rsquo;t supply replacement parts. The gearbox case doesn&rsquo;t care what gears fit inside of it. If they don&rsquo;t, I&rsquo;d sure shy away from buying one. George Helton 1986 Firestar, FS100 14GDH Mesick, Michigan gdhelton(at)gmail.com Sent from my iPhone > On May 9, 2018, at 2:18 PM, Bill Berle <victorbravo(at)sbcglobal.net> wrote: > > --> Kolb-List message posted by: Bill Berle <victorbravo(at)sbcglobal.net> > > I have been pulling out what's left of my hair over this issue. I really don't want to quit, I LIKE the Kolb airframe and it will fit my mission well. I like the HKS fuel economy and improved reliability. I just wound up with the wrong gearbox on it and cannot afford to change it. > > What I have learned thus far is: > > 1) My 3.47 to 1 gearbox really wants to swing a larger propeller than what is actually "correct" for the height of the thrust line on the Kolb airframe. > > 2) Turning the gearbox upwards will solve the prop diameter problem, but it creates a thrust line that is higher than the Kolb factory thinks is advisable. > > 3) I could easily go to a 4 or 5 blade propeller, solves the gearbox AND thrust line problems, but that interferes with folding the wings. > > I have considered many possible solutions or "work-arounds" : > > 1) Get a 5 blade propeller and remove it after every flight, which would allow ALL of the problems to be solved, at the cost of additional time and effort every time I fly. This will cost the least of all the "solutions". > > 2) Remove the wings after every flight instead of folding the wings. This allows a 5 blade propeller to be used but adds complexity and requires me to build a complicated ground fixture to allow the wings to be removed and installed by myself alone. > > 3) Make a folding propeller, like the electric R/C model gliders have, where the blades fold rearward. This solves all of the problems, no complex ground equipment, but designing and manufacturing such a propeller will be prohibitvely expensive. > > 4) Buy another gearbox from HKS. This is the best solution mechanically, but I cannot afford it. > > 5) Turn the gearbox upwards, install the right propeller, and live with the possibly dangerous or funky flight handling of the airplane. > > Any other/better/wiser/workable ideas from the Kolb List are very very welcome! > > > > > Bill Berle > www.ezflaphandle.com - safety & performance upgrade for light aircraft > www.grantstar.net - winning proposals for non-profit and for-profit entities > > -------------------------------------------- > On Wed, 5/9/18, George Helton <gdhelton(at)gmail.com> wrote: > > Subject: Re: Re: High Thrust Line Question > To: kolb-list(at)matronics.com > Date: Wednesday, May 9, 2018, 9:39 AM > > --> Kolb-List message posted by: George > Helton <gdhelton(at)gmail.com> > > Well Bill, thanks for bringing up the > topic. I replaced my little Rotax 377 with new low rpm Hirth > 2702 over the winter. I really hadn&rsquo;t measured the > distance between the prop hub and boom tube. You sparked my > interest so I stopped by my hanger this morning to check it > out. The Hirth uses a G50 gearbox with 2:29 to 1 ratio. > which translates to 2400 rpm prop speed (at) the engine&rsquo;s > max. HP rpm of 5500rpm. > Anyway, it measures 35.5 inches. This > is on a Kolb original Firestar. I did have to move the > engine forward 2.625&rdquo; to compensate for the extra weight > of the new gear box. I went with a 64&rdquo; 3 blade Powerfin > prop set at 6.4 degrees of pitch. This setup gives me 3.5&rdquo; > of clearance from the boom tube. Thanks for inspiring me to > check it out. I&rsquo;m sure there is a good combination > of prop out there for an HKS. > George Helton > 1986 Firestar, FS100 > 14GDH > Mesick, Michigan > gdhelton(at)gmail.com > > Sent from my iPhone > >> On May 8, 2018, at 11:08 PM, Bill > Berle <victorbravo(at)sbcglobal.net> > wrote: >> >> --> Kolb-List message posted > by: Bill Berle <victorbravo(at)sbcglobal.net> >> >> Everybody THANK YOU for taking > time for this discussion. >> >> I spoke to the Kolb factory today > by phone, and went out to the local UL flying field to see > an HKS engine run. >> >> Duane and Bryan at Kolb were asked > one specific question by me: What is the maximum > number of inches allowable or advisable between the center > of the propeller and the top of the tailboom? >> >> Bryan said that 36 inches is about > standard for a "normal" Firestar, and he would not want to > fly an airplane with that distance raised to 39 or 40 > inches. >> >> I went back to my hangar and > measured, and the distance on my Firestar would be over 40 > or 41 inches if I turned the gearbox upward. So if the Kolb > factory owner says 40 inches is too high, I can only be > humble and assume that I wouldn't want to fly it at 40 > inches either. If any of the highly experienced Kolbers on > this forum are flying with their thrust line 40 inches above > the tailboom, I REALLY would like to know about it pronto. >> >> As big of an ego as I have had a > few times in my life, and as much as I think of myself as a > reasonably skilled pilot, I don't need to be a test > pilot here and try to push any envelope at this early stage. > So if I can ask the Kolb ilst a favor... if any of you are > flying a Firestar with the engine thrust line 39 or 40 or 41 > incvhes above the tailboom please post this on the list and > let me know ifyou have any issues with the handling, > pitch-over, etc. >> >> Bill Berle >> www.ezflaphandle.com - > safety & performance upgrade for light aircraft >> www.grantstar.net > - winning proposals for non-profit and > for-profit entities >> >> > -------------------------------------------- >> On Tue, 5/8/18, Richard Pike > <thegreybaron(at)charter.net> > wrote: >> >> Subject: Re: High > Thrust Line Question >> To: kolb-list(at)matronics.com >> Date: Tuesday, May 8, 2018, 4:38 > PM >> >> --> Kolb-List message posted > by: "Richard >> Pike" <thegreybaron(at)charter.net> >> >> Bill; notice the extent to which > Rick >> raised his engine. (Great > pictures) Maybe you can leave the >> gearbox down and raise the engine > up? >> >> -------- >> Richard Pike >> Kolb MKIII N420P (420ldPoops) >> Kingsport, TN 3TN0 >> >> Forgiving is tough, being forgiven > is >> wonderful, and God's grace really > is amazing. >> >> >> >> >> Read this topic online here: >> >> http://forums.matronics.com/viewtopic.php?p=479963#479963 >> >> >> >> >> >> >> The Kolb-List Email Forum - >> Navigator to browse >> List Un/Subscription, >> 7-Day Browse, Chat, FAQ, >> - MATRONICS > WEB FORUMS - >> via the Web Forums! >> - NEW MATRONICS LIST > WIKI - >> Email List Wiki! >> - List Contribution > Web Site - >> support! >> > >> -Matt Dralle, List > Admin. >> >> >> >> >> >> >> >> > > The Kolb-List Email Forum - > Navigator to browse > List Un/Subscription, > 7-Day Browse, Chat, FAQ, > - MATRONICS WEB FORUMS - > via the Web Forums! > - NEW MATRONICS LIST WIKI - > Email List Wiki! > - List Contribution Web Site - > support! > > -Matt Dralle, List Admin. > > > > > > > > The Kolb-List Email Forum - Navigator to browse List Un/Subscription, 7-Day Browse, Chat, FAQ, - MATRONICS WEB FORUMS - via the Web Forums! - NEW MATRONICS LIST WIKI - Email List Wiki! - List Contribution Web Site - support! -Matt Dralle, List Admin. =========== =========== =========== =========== ===========


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Use the List Feature Navigator to browse the many List utilities available such as the Email Subscriptions page, Archive Search & Download, 7-Day Browse, Chat, FAQ, Photoshare, and much more:

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Jack B Hart FFoo4
Winchester, IN
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