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Kolb-List:Stabilizer Angle
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victorbravo(at)sbcglobal.
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PostPosted: Sat Aug 18, 2018 12:01 pm    Post subject: Kolb-List:Stabilizer Angle Reply with quote

I'm not delicate by any stretch... I always felt that any time I held up my end of a good argument here lots of people got their panties in a twist Smile

Sent from my Samsung Captivate(tm) on AT&T

Larry Cottrell <lcottrell1020(at)gmail.com> wrote:

Quote:
On Sat, Aug 18, 2018 at 8:57 AM, Bill <victorbravo(at)sbcglobal.net> wrote:

>
>
> Just finished a 30 minute test flight. Aircraft improved by both the tape
> seal on the aileron gap and the trim tabs on elevator. Hands off at 40 mph
> at 4750-4800 rpm. 48-50 mph at 5300-5400 rpm with very light forward
> pressure on stick. Rudder trim for some reason was better than last flight
> even with no change. Still need a small additional bend in rudder trim tab.
> This flight was still WITH the raised stabilizer angle, but with the
> addition of the elevator trim tab.
>
> ---------------------------------------------------------------------------------------------------------------------------------------------------------------------
I believe that I mentioned before that without an adjustable trim tab, your
only option is to trim for what you consider "cruise" RPM's. Mine is 5400.
That gives me the most speed for the least amount of gas expended. When I
increase the RPM's it begins to climb, which is the proper function of
power anyway.

I went over to the ranch to check for stuck cows in the pothole field, and
I was in a hurry, so I was turning around 5800 (max continued power) and of
course the plane was climbing at about 300 fpm and I had to use a lot of
forward pressure on the stick to try to keep at the altitude that I wanted
to fly. It came to mind that this could possibly be what you are talking
about as a problem? I had never paid attention before because it is just
the way that Kolbs fly. Is it possible that you are expecting your kolb to
fly like a 172, cause it "ain't gonna happen". In essence it could be
possible that some of the things that are worrying you, could just be the
normal reaction of the aircraft that you are flying. Now I know that you
might be a bit delicate, but none of this is intended to insult you.

Larry
*The older I get, the less tolerant I am of those who are intolerant of
others.*

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


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Richard Pike



Joined: 09 Jan 2006
Posts: 1520
Location: Blountville, Tennessee

PostPosted: Sat Aug 18, 2018 3:20 pm    Post subject: Re: Kolb-List:Stabilizer Angle Reply with quote

Just thinking about elevator trim tabs - I have a small one on my MKIII because when I first flew it there was was one speed and throttle setting where it wanted to do something wonky - too long ago, can't remember what it was. Also that was before I could slightly reflex or droop the flaps while in flight, so the elevator trim tab is probably unnecessary now. Or maybe not - I'm not changing anything.

Anyway, on the MKIII, the elevator trim tab is optimized for solo flight, it has a spring loaded trim lever that is used when carrying a passenger because there are radical trim changes when you add a passenger. The MKIII spring system works good, no problem.

Then there is the Firefly; we built it with this little spring loaded device on the front of the stick because pitch trim changes depending on how much fuel you have left. This is more than sufficient, you only have to move it a notch or two from full fuel to minimum fuel.


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Richard Pike
Kolb MKIII N420P (420ldPoops)
Kolb Firefly Part 103 legal (Repairing the fiberglass nose bowl. Ugh.)
Kingsport, TN 3TN0

Forgiving is tough, being forgiven is wonderful, and God's grace really is amazing.
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PostPosted: Sat Aug 18, 2018 3:41 pm    Post subject: Kolb-List:Stabilizer Angle Reply with quote

Hi Richard. Did you get the little beast back in the air yet?

Sent from my iPhone

Quote:
On Aug 18, 2018, at 7:20 PM, Richard Pike <thegreybaron(at)charter.net> wrote:



Just thinking about elevator trim tabs - I have a small one on my MKIII because when I first flew it there was was one speed and throttle setting where it wanted to do something wonky - too long ago, can't remember what it was. Also that was before I could slightly reflex or droop the flaps while in flight, so the elevator trim tab is probably unnecessary now. Or maybe not - I'm not changing anything.

Anyway, on the MKIII, the elevator trim tab is optimized for solo flight, it has a spring loaded trim lever that is used when carrying a passenger because there are radical trim changes when you add a passenger. The MKIII spring system works good, no problem.

Then there is the Firefly; we built it with this little spring loaded device on the front of the stick because pitch trim changes depending on how much fuel you have left. This is more than sufficient, you only have to move it a notch or two from full fuel to minimum fuel.

--------
Richard Pike
Kolb MKIII N420P (420ldPoops)
Kolb Firefly Part 103 legal w/incredibly obnoxious Rotax 277
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=482525#482525




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Richard Pike



Joined: 09 Jan 2006
Posts: 1520
Location: Blountville, Tennessee

PostPosted: Sat Aug 18, 2018 4:40 pm    Post subject: Re: Kolb-List:Stabilizer Angle Reply with quote

[quote="gdhelton(at)gmail.com"]Hi Richard. Did you get the little beast back in the air yet?
[quote]
Nope. The primary source of our problems was using a free air engine when we should have been using fan cooled. Purchased an old fan cooled Rotax 277, now working on swapping around the best of several cranks, pistons, sleeves, etc. Then got to figure out new motor mounts.
Only flown the MKIII once this summer, too many projects.


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Richard Pike
Kolb MKIII N420P (420ldPoops)
Kolb Firefly Part 103 legal (Repairing the fiberglass nose bowl. Ugh.)
Kingsport, TN 3TN0

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PostPosted: Sat Aug 18, 2018 4:58 pm    Post subject: Kolb-List:Stabilizer Angle Reply with quote

Ok, I was just wondering how that project was going. Good luck. 👍

Sent from my iPhone

[quote] On Aug 18, 2018, at 8:40 PM, Richard Pike <thegreybaron(at)charter.net> wrote:



[quote="gdhelton(at)gmail.com"]Hi Richard. Did you get the little beast back in the air yet?
Quote:

Nope. The primary source of our problems was using a free air engine when we should have been using fan cooled. Purchased an old fan cooled Rotax 277, now working on swapping around the best of several cranks, pistons, sleeves, etc. Then got to figure out new motor mounts.
Only flown the MKIII once this summer, too many projects.

--------
Richard Pike
Kolb MKIII N420P (420ldPoops)
Kolb Firefly Part 103 legal w/incredibly obnoxious Rotax 277
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=482529#482529











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John Hauck



Joined: 09 Jan 2006
Posts: 4600
Location: Titus, Alabama (hauck's holler)

PostPosted: Sun Aug 19, 2018 4:29 am    Post subject: Kolb-List:Stabilizer Angle Reply with quote

Before and during initial build of my MKIII I was able to fly the 40 hours
off the Factory MKIII. This gave me a chance to determine what I
liked/unliked, what I felt needed changing and how to go about it. Pitch
trim was one of those things. We came up with infinite nose up trim because
we knew we would never need nose down. I wasn't crazy about Homer's trim
system and it was on the left side of the cockpit and I was going to fly
from the right seat to take advantage of the original center mounted
throttle and our dual sticks, first in a MKIII, long before Kolb decided to
follow suit.

Recently, after all these years and hours, I was getting aft pressure on the
stick. Couldn't understand why. It slowly began to increase back pressure.
Finally, I discovered the 1/16" cable system was binding at the pulley, not
releasing nose up trim pressure. Was a relief to discover that. Was
worrying me because I could not figure out why.

I don't need an elevator trim tab on the MKIII.

I flew my MKIII to Alaska a couple times with the slip/skid indicator a half
ball out. To center it took constant pressure on the left pedal which was
tiring and eventually uncomfortable on my foot. I was flying with half the
trim tab I have now. I had gone through the exercise of trying to offset
the leading edge of the upper vertical stabilizer, which didn't work and
only caused me to punch a lot of rivet holes in the tail boom. Finally, I
decided to experiment with the rudder trim tab again. Initially I made one
triple the size I was flying with. First test flight proved it was too big.
Cut off a third, which was one rib bay wide, and it was perfect. I could
fly with my feet off the pedals and the MKIII was perfectly trimmed in
cruise. Only problem was the rudder would start oscillating without
additional pressure on the pedals. Got the bright idea of doubling the
rudder pedal springs, which adds no resistance to operating the pedals.
Works perfectly. No more shuffle.

My MKIII wanted to roll left a tiny bit, at times. Sometimes it didn't. I
rigged a bungee trim system that slips up on the stick to increase lateral
trim. In the down position pressure is neutral. Works like a charm. Used
tiny hose clamps to make the loops on each end. A few minute to make up and
I had the parts laying around the shop.

So that's what it takes to trim up Miss P'fer and keep me happy. She
doesn't care whether she is trimmed up perfectly or not. That has been
verified by a lot of very long cross country hours with here happily flying
out of trim. I saw no increase or decrease either way.

Another decision was confirmed a day or two after I got to Homer Kolb's to
build my fuselage. Homer was flying family children in the MKIII. Brother
Jim and I were standing on his grass strip watching. On one landing Homer
made a 180 degree taxi turn with tail into the wind. Immediately tipped the
MKIII up on its nose. Jim and I looked at each other and said
simultaneously, "We're going to move the main gear forward." Never had a
problem keeping the tail wheel on the ground with my MKIII.

My ideas only. Don't recommend anyone else doing what I do.

john h
mkIII
Titus, Alabama


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John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama
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John Hauck



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Location: Titus, Alabama (hauck's holler)

PostPosted: Sun Aug 19, 2018 4:31 am    Post subject: Kolb-List:Stabilizer Angle Reply with quote

That's a good system on the FF. I have also seen this accomplished using a
small lever instead of hooks.

john h
mkIII
Titus, Alabama








Then there is the Firefly; we built it with this little spring loaded device
on the front of the stick because pitch trim changes depending on how much
fuel you have left. This is more than sufficient, you only have to move it a
notch or two from full fuel to minimum fuel.

--------
Richard Pike
Kolb MKIII N420P (420ldPoops)
Kolb Firefly Part 103 legal w/incredibly obnoxious Rotax 277
Kingsport, TN 3TN0


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John Hauck
MKIII/912ULS
hauck's holler
Titus, Alabama
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victorbravo(at)sbcglobal.
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PostPosted: Mon Aug 20, 2018 12:37 pm    Post subject: Kolb-List:Stabilizer Angle Reply with quote

OK we just did a second weight and balance to settle this issue. The aircraft was specifically put in the same configuration as it has been flown. Pilot wearing clothes, shoes, helmet, and a total of 6.5 gallons of fuel. Same digital scales. THIS Kolb has different landing gear legs than stock! Datum was wheel axles. Wing leading edge was 3.5" forward of datum. Main gear weights 331 and 300. Tail weight 67. Center of gravity was 18.36" aft of datun which is 21.86" aft of leading edge. 21.86" is 34.15% of the 64" wing chord specified by Kolb. So my CG is 34.15% which is significantly forward of the factory approved maximum of 37%. Actual flight weight in this configuration is 698 pounds, 27 pounds under gross weight. Empty weight, removing the weight of fuel and oil, works out to approx. 430. Heavier engine, tires, gear legs, exhaust, battery, and it had been painted twice.

Sent from my Samsung Captivate(tm) on AT&T

John Hauck <jhauck(at)elmore.rr.com> wrote:

Quote:


That's a good system on the FF. I have also seen this accomplished using a
small lever instead of hooks.

john h
mkIII
Titus, Alabama








Then there is the Firefly; we built it with this little spring loaded device
on the front of the stick because pitch trim changes depending on how much
fuel you have left. This is more than sufficient, you only have to move it a
notch or two from full fuel to minimum fuel.

--------
Richard Pike
Kolb MKIII N420P (420ldPoops)
Kolb Firefly Part 103 legal w/incredibly obnoxious Rotax 277
Kingsport, TN 3TN0




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John Hauck



Joined: 09 Jan 2006
Posts: 4600
Location: Titus, Alabama (hauck's holler)

PostPosted: Mon Aug 20, 2018 12:56 pm    Post subject: Kolb-List:Stabilizer Angle Reply with quote

Got me baffled.

I don't see how it could have a nose up tendency with that much weight in the front seat.

But it is what it is.

john h
mkIII
Titus, Alabama


--


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PostPosted: Mon Aug 20, 2018 1:31 pm    Post subject: Kolb-List:Stabilizer Angle Reply with quote

Quote:
I entered your numbers on my spread sheet....

You didnt give the arm for the tail wheel...   So i back calculated it.
I came up with your exact numbers provided the tail wheel is  191.25 behind the mains.
Boyd
Quote:





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PostPosted: Mon Aug 20, 2018 4:09 pm    Post subject: Kolb-List:Stabilizer Angle Reply with quote

Yes this measurement is approx 191 inches from the tailwheel to the main wheel axle line under the center of the fuselage.
Sent from my Samsung Captivate(tm) on AT&T

B Young <byoungplumbing(at)gmail.com> wrote:

Quote:
>
> I entered your numbers on my spread sheet....
>
> You didnt give the arm for the tail wheel... So i back calculated it.
>
> I came up with your exact numbers provided the tail wheel is 191.25
> behind the mains.
>
> Boyd
>


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PostPosted: Mon Aug 20, 2018 4:13 pm    Post subject: Kolb-List:Stabilizer Angle Reply with quote

Bill,

Very glad it is not a CG problem and that it has been definitively ruled out. Sorry for the extra work, but the symptoms called for the effort to be expended.

So now, we know that changing the angle of the horizontal stabilizers helped with the issue considerably even if it is "out of spec".

We have already discussed the wing center section gap seal, and that would be my next area of experimentation. After all you can change that without making any structural changes and it is easy to go back to what you have.

Another thought has occurred to me about your low airspeeds. A few questions:

Have you done a static full power run to make sure you are getting proper RPM's?
Or
Have you done a full power run in the air while straight and level?

Have you confirmed your tachometer with another device?

Have you confirmed your ASI (I know you changed the pitot/static setup) to verify that you are truly getting what you are seeing?

Idea for next flight. While straight and level, go to full throttle and see what happens. You only have to maintain it long enough to get a stable tachometer reading and to see what forces are required at the stick.

At this point I am just tossing out random thoughts in hopes that something ticks in your mind to say "hey, what if I did this?".

Hang in there, we're all pulling for you to figure this out.

Some people like mysteries, I rather tent to like the solutions!

Keep us informed,

Stuart

--


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PostPosted: Mon Aug 20, 2018 5:58 pm    Post subject: Kolb-List:Stabilizer Angle Reply with quote

Full throttle on takeoff and climbout gives me 5700-5800 rpm which is max continuous power. This yields 40-45mph climbing. I have not done extended full power in level flight yet but based on what I have seen so far I would expect 50-52mph and 6000 rpm. Brand new Tiny Tach installed per direct verbal installation instructions on the phone with their tech guy. Airspeed indicator tested with this same air probe stuck out thru the car sunroof, measured same as my car speedometer. Unless experienced Kolbers suggest otherwise, I will put on the short windshield as the next change. How much speed is typical improvement going from round to streamline struts??

Sent from my Samsung Captivate(tm) on AT&T

Stuart Harner <stuart(at)harnerfarm.net> wrote:

[quote]

Bill,

Very glad it is not a CG problem and that it has been definitively ruled out. Sorry for the extra work, but the symptoms called for the effort to be expended.

So now, we know that changing the angle of the horizontal stabilizers helped with the issue considerably even if it is "out of spec".

We have already discussed the wing center section gap seal, and that would be my next area of experimentation. After all you can change that without making any structural changes and it is easy to go back to what you have.

Another thought has occurred to me about your low airspeeds. A few questions:

Have you done a static full power run to make sure you are getting proper RPM's?
Or
Have you done a full power run in the air while straight and level?

Have you confirmed your tachometer with another device?

Have you confirmed your ASI (I know you changed the pitot/static setup) to verify that you are truly getting what you are seeing?

Idea for next flight. While straight and level, go to full throttle and see what happens. You only have to maintain it long enough to get a stable tachometer reading and to see what forces are required at the stick.

At this point I am just tossing out random thoughts in hopes that something ticks in your mind to say "hey, what if I did this?".

Hang in there, we're all pulling for you to figure this out.

Some people like mysteries, I rather tent to like the solutions!

Keep us informed,

Stuart

--


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John Hauck



Joined: 09 Jan 2006
Posts: 4600
Location: Titus, Alabama (hauck's holler)

PostPosted: Mon Aug 20, 2018 6:30 pm    Post subject: Kolb-List:Stabilizer Angle Reply with quote

To correctly prop an aircraft with ground adjustable or fixed pitch prop:

--Bump the red line (max continuous rpm) at WOT straight and level flight. That's wide open at top speed attained.

If you are turning 5800 at climb out you are under pitched. Probably part of your air speed problem.

ASI's are pressure/static instruments, extremely sensitive to static pressure. What you get out of the sun roof of your ride is not what you are going to get out of your Kolb. Inside a semi-enclosed cockpit, behind a nose cone, in a fully enclosed cockpit, you will experience low pressure. Low pressure gives a high false air speed reading. High pressure produces a low reading.

I would use a GPS, fly opposite headings, same altitude, same IAS. Average your two GPS readings. This will be very close to true air speed. Whether the ASI reads high or low, it will always indicate the same speed at stall.

Streamlined struts will reduce lift strut vibration and slightly increase air speed. How much? You'll have to experiment to see.

john h
mkIII
Titus, Alabama




Full throttle on takeoff and climbout gives me 5700-5800 rpm which is max continuous power. This yields 40-45mph climbing. I have not done extended full power in level flight yet but based on what I have seen so far I would expect 50-52mph and 6000 rpm. Brand new Tiny Tach installed per direct verbal installation instructions on the phone with their tech guy. Airspeed indicator tested with this same air probe stuck out thru the car sunroof, measured same as my car speedometer. Unless experienced Kolbers suggest otherwise, I will put on the short windshield as the next change. How much speed is typical improvement going from round to streamline struts??


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MKIII/912ULS
hauck's holler
Titus, Alabama
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PostPosted: Mon Aug 20, 2018 6:51 pm    Post subject: Kolb-List:Stabilizer Angle Reply with quote

Bill, those figures don’t sound that bad to me. I’m running a different engine of course. My original Firestar’s best climb rate is right at 45/46 mph. Straight and level 5500 rpm in calm air is 64/66 mph. That does require lots of forward stick pressure. It likes to cruise at 4800 to 5200rpm (at) 52/55 mph. Obviously we’re running two completely different engines. My max. hp is 40 (at) 5500rpm, that’s what I consider max. rpm even though it’s actually 5800. My max. torque is 49ft.lbs (at) 4800.
So, airframe-wise( I don’t think that’s actually a word?) I think the performance numbers are in the ballpark. It would be nice to bring the horizontal stabilizer back where it belongs. But, it’s your decision. Keep tinkering. And enjoy some flying.
Aero liftstruts? They claim 6 to 8 mph. But, that sounds alittle iffy to me? But, I did order a set of 3:1 aero fairings for mine so I’ll let you know how they work, like maybe next week. I think I just threw some money down the drain?
George H.
Firestar, FS100, 2702 Hirth
14GDH
Mesick, Michigan
gdhelton(at)gmail.com

Sent from my iPhone

[quote] On Aug 20, 2018, at 9:58 PM, Bill <victorbravo(at)sbcglobal.net> wrote:



Full throttle on takeoff and climbout gives me 5700-5800 rpm which is max continuous power. This yields 40-45mph climbing. I have not done extended full power in level flight yet but based on what I have seen so far I would expect 50-52mph and 6000 rpm. Brand new Tiny Tach installed per direct verbal installation instructions on the phone with their tech guy. Airspeed indicator tested with this same air probe stuck out thru the car sunroof, measured same as my car speedometer. Unless experienced Kolbers suggest otherwise, I will put on the short windshield as the next change. How much speed is typical improvement going from round to streamline struts??

Sent from my Samsung Captivate(tm) on AT&T

Stuart Harner <stuart(at)harnerfarm.net> wrote:

>
>
> Bill,
>
> Very glad it is not a CG problem and that it has been definitively ruled out. Sorry for the extra work, but the symptoms called for the effort to be expended.
>
> So now, we know that changing the angle of the horizontal stabilizers helped with the issue considerably even if it is "out of spec".
>
> We have already discussed the wing center section gap seal, and that would be my next area of experimentation. After all you can change that without making any structural changes and it is easy to go back to what you have.
>
> Another thought has occurred to me about your low airspeeds. A few questions:
>
> Have you done a static full power run to make sure you are getting proper RPM's?
> Or
> Have you done a full power run in the air while straight and level?
>
> Have you confirmed your tachometer with another device?
>
> Have you confirmed your ASI (I know you changed the pitot/static setup) to verify that you are truly getting what you are seeing?
>
> Idea for next flight. While straight and level, go to full throttle and see what happens. You only have to maintain it long enough to get a stable tachometer reading and to see what forces are required at the stick.
>
> At this point I am just tossing out random thoughts in hopes that something ticks in your mind to say "hey, what if I did this?".
>
> Hang in there, we're all pulling for you to figure this out.
>
> Some people like mysteries, I rather tent to like the solutions!
>
> Keep us informed,
>
> Stuart
>
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victorbravo(at)sbcglobal.
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PostPosted: Mon Aug 20, 2018 7:30 pm    Post subject: Kolb-List:Stabilizer Angle Reply with quote

Guys thank you all again for going down this bizarre rabbit hole with me.

The aircraft flies reasonably well as it is now, with stabilizer jacked up "way too high" and additional trim tabs on the elevator. If I lowered the stabilizer back down then I would be going back to holding a lot of forward pressure on the stick, which I do not need or want to do.The only other option is a very very large trim tab ont he elevator, which would likely be 10-12% of the size of the elevator. This is also a lot less desirable to me. A large trim tab adds weight on the un-safe side of the elevator (for flutter issues),a nd also drags in the weeds when you are on the ground.

Again, as it is right now I have 4 degrees of positive "decalage" angle at my current setting. This is relatively safe and very similar to Cessnas and J-3 Cubs and other "regular" airplanes.This tells me that the stock plans-built Kolb has something a lot more than that, maybe 8 or 10 degrees of decalage??? Wouldn't THAT sound excessive ?

I have not heard back from Duane at Kolb Aircraft. When we last spoke he said he would talk with Bryan and get back to me via e-mail. I have no idea if they have just not gotten to it yet, or whether Bryan decideed that me and my airplane were just too crazy to get involved with Smile

Forgive me for being repetitive, but for reference, at this stage we have the following known configuration:

Wing incidence measurement is almost perfectly matched to the measurement given to me by Duane at Kolb.
Tail boom tube length has not been shortened form a stock Firestar 2.
Fuselage tube structure is not obviously bent or patched, so the "upward angle" of the boom tube is likely the same as a stock FS2.
Weight and balance verified at 34.15% of chord, clearly within Kolb's acceptable range for safe filght (20-37 %).

One or two people have suggested that perhaps my exhaust coming out of the muffler is creating anose-up pitch, because the muffler is underneath the aircraft. I do not believe this is the case, because I have flown at low power settings, and the nose did not fall downward (which it would have done if the muffler "thrust" was lifting the nose).

Perhaps all the effort I put in over months of screwing around, to keep the thrust line as low as possible, has hurt me ? If the Kolb wing and stabilizer angle were designed for a thrust line that was farther above the aircraft , and mine is a lot lower, then THAT would perhaps explain how there is a nose-up pitch... because the designers at Kolb were assuming I would have a higher thrust line that would push the nose down some ???

My thurst line (center of propeller) is 33.25 inches above the TOP of the tailboom tube. Is this significantly LOWER than most of the other Firestars? What is the height of the center or the prop above other Kolbers Firestar tailboom tubes?

If everybody else's thrust line is 36 or 38 inches above the tailoom tube, then everyone else would have the engine pushing the nose down more than I do. If Kolb designed the Firestar's wing and tail angles for a thrust oline that was 36 or 38 inches high, and I only have 33.25 inches, then at least THAT would explain why my aircraft wanted to pitch upward and the other Kolbers don't have that problem.

Another possibility is that having any windshield on the aircraft creates a nose-down pitch, and since I have no windshield then that nose-down pitch is missing on my aircraft.Again this sounds implausible, but it would explain this strange situation.

Also, I have never flown mine without the VG's on the wing or tail. I had them on the first flight. Any Kolbers who have installed VG's... did this cause your aircraft to start pitching up where it did not do that without VG's???
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, 8/20/18, George Helton <gdhelton(at)gmail.com> wrote:

Subject: Re: Kolb-List:Stabilizer Angle
To: kolb-list(at)matronics.com
Date: Monday, August 20, 2018, 7:51 PM


Helton <gdhelton(at)gmail.com>

Bill, those figures don’t sound that
bad to me. I’m running a different engine of course. My
original Firestar’s best climb rate is right at 45/46 mph.
Straight and level 5500 rpm in calm air is 64/66 mph. That
does require lots of forward stick pressure. It likes to
cruise at 4800 to 5200rpm (at) 52/55 mph. Obviously we’re
running two completely different engines. My max. hp is 40 (at)
5500rpm, that’s what I consider max. rpm even though
it’s actually 5800. My max. torque is 49ft.lbs (at) 4800.
So, airframe-wise( I don’t think
that’s actually a word?) I think the performance numbers
are in the ballpark. It would be nice to bring the
horizontal stabilizer back where it belongs. But, it’s
your decision. Keep tinkering. And enjoy some flying.
Aero liftstruts? They claim 6 to 8 mph.
But, that sounds alittle iffy to me? But, I did order a set
of 3:1 aero fairings for mine so I’ll let you know how
they work, like maybe next week. I think I just threw some
money down the drain?
George H.
Firestar, FS100, 2702 Hirth
14GDH
Mesick, Michigan
gdhelton(at)gmail.com

Sent from my iPhone

> On Aug 20, 2018, at 9:58 PM, Bill
<victorbravo(at)sbcglobal.net>
wrote:
>
> --> Kolb-List message posted
by: Bill <victorbravo(at)sbcglobal.net>
>
> Full throttle on takeoff and
climbout  gives me 5700-5800 rpm which is max
continuous power. This yields 40-45mph climbing. I have not
done extended full power in level flight yet but based on
what I have seen so far I would expect 50-52mph and 6000
rpm. Brand new Tiny Tach installed per direct verbal
installation  instructions on the phone with their tech
guy. Airspeed indicator tested with this same air probe
stuck out thru the car sunroof, measured same as my car
speedometer. Unless experienced Kolbers suggest otherwise, I
will put on the short windshield as the next change. How
much speed is typical improvement going from round to
streamline struts??
>
> Sent from my Samsung Captivate(tm)
on AT&T
>
> Stuart Harner <stuart(at)harnerfarm.net>
wrote:
>
>> --> Kolb-List message
posted by: "Stuart Harner" <stuart(at)harnerfarm.net>
>>
>> Bill,
>>
>> Very glad it is not a CG
problem and that it has been definitively ruled out. Sorry
for the extra work, but the symptoms called for the effort
to be expended.
>>
>> So now, we know that changing
the angle of the horizontal stabilizers helped with the
issue considerably even if it is "out of spec".
>>
>> We have already discussed the
wing center section gap seal, and that would be my next area
of experimentation. After all you can change that without
making any structural changes and it is easy to go back to
what you have.
>>
>> Another thought has occurred
to me about your low airspeeds. A few questions:
>>
>> Have you done a static full
power run to make sure you are getting proper RPM's?
>> Or
>> Have you done a full power run
in the air while straight and level?
>>
>> Have you confirmed your
tachometer with another device?
>>
>> Have you confirmed your ASI (I
know you changed the pitot/static setup) to verify that you
are truly getting what you are seeing?
>>
>> Idea for next flight. While
straight and level, go to full throttle and see what
happens. You only have to maintain it long enough to get a
stable tachometer reading and to see what forces are
required at the stick.
>>
>> At this point I am just
tossing out random thoughts in hopes that something ticks in
your mind to say "hey, what if I did this?".
>>
>> Hang in there, we're all
pulling for you to figure this out.
>>
>> Some people like mysteries, I
rather tent to like the solutions!
>>
>> Keep us informed,
>>
>> Stuart
>>
>> --


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Richard Pike



Joined: 09 Jan 2006
Posts: 1520
Location: Blountville, Tennessee

PostPosted: Mon Aug 20, 2018 8:41 pm    Post subject: Re: Kolb-List:Stabilizer Angle Reply with quote

Adding VG's to the wing or the underside of the stab/elevator causes no pitch change.

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Richard Pike
Kolb MKIII N420P (420ldPoops)
Kolb Firefly Part 103 legal (Repairing the fiberglass nose bowl. Ugh.)
Kingsport, TN 3TN0

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Jerry-TS-MkII



Joined: 23 Aug 2017
Posts: 43
Location: Indiana

PostPosted: Tue Aug 21, 2018 7:40 am    Post subject: Re: Kolb-List:Stabilizer Angle Reply with quote

Mind if I chime in? In most of the responses.. I may have a different outlook. In part because I am NOT a Kolb expert.. but I have been flying airplanes of one sort or another since I was 8. And at last count, that's been 59 years.

So.. please consider some of this, as it applies to any virtual aircraft, OR YOURS! You have disclosed some new details recently.

I can take any given airplane.. say a model (which flies the same as a real plane).. and it will do the following. If I raise the wing incidence, or lower the incidence of the stab.. it will go nose up in a glide. That can be corrected by moving the CG forward.. or readjusting the decalage. If power is added, the plane will fly faster, and will climb because the wing is producing more lift. How to get both aspects in line? Add down thrust to the engine, or a lifting stabilizer. Oh, now it rolls with the torque? Add right (or left thrust) to the engine. With power on, the engine "effects" are reduced, by those offsets. If you add a chunk of weight to the airplane overall, one of two things are required for it to fly. It needs to go faster (and hence produce more lift), or the angle of attack needs to be increased (which works up to about 16° on most cambered airfoils, before it quits flying). In doing the latter, the DRAG goes up, because you are producing the same lift, at a slower speed. And that changes the pitching moments of the wing typically as well. YOUR airplane is hauling some weight, so it's got a higher angle of attack than you want.. but not much you can do about that, without a larger wing, or more motor.. both of which add weight!

How does that apply to YOUR plane? First off, I had no idea your engine thrust line was that much lower than the typical Kolb. So changing that (to less).. will certainly cause more stick forces to be needed, to keep the nose down under power. Throttle back, and it becomes less of an effect, and yes, up elevator is then needed to flare. If the prop were to be higher, more of it is in cleaner air, and produces more thrust than if right in line with the wing.

You do have a heavy Kolb, which means it either needs to fly faster (with much more HP/thrust), OR.. the necessary angle of attack will have the plane acting very draggy. (Hey, imagine that!). Add a hole in the center section of your wing.. and that causes a loss of lift, and more drag. Add in a reward CG (please disregards "the norms" because YOUR airplane is NOT normal, in comparison). So that means the stabilizer is doing all of the flight trim work that it can, (jacked up) to keep the nose down.. (less any help from the engine thrust line) and THAT is adding drag. It's no wonder it's flying slowly. Dropping the ailerons a few clicks would help with the trim. And EVERYTHING I've read about Kolbs (including the crash reports).. you DON'T want to stall it near the ground.. PERIOD! They apparently stop flying rather abruptly, which is true of most any sharp pointed leading edge airfoil, as the Kolb has.

Adding weight (for experimental purposed to adjust the CG) to a heavy airplane might be a non-starter. But if you DID relocate something forward, the tail won't be doing all the work. I doubt you can make your plane much lighter. More prop pitch may help generate more thrust. But reducing the drag might work best, by sealing the hole in the center section. And as for struts? Have you EVER seen a store bought strut braced wing, W/O streamlined struts? Likely not. It will help. Sealing all of your hinge gaps will help. And adding a canopy of some sort will reduce drag, and clean up the air flow.

Just because some folks on here have a truck tire on the tail, or that Kolb says, the CG range is XXX.. moving the CG forward will reduce the amount of drag generated by your extreme stab angle. Hey.. EVER SEEN A WEIGHT SHIFT HANG GLIDER OR JET WING FLY, WITH AUTHORITY?? No tail, no stab.. JUST changing the effective CG.

I do believe you are right regarding your lowered thrust line. Your engineer friend could calculate the difference in the amount of effective down thrust (forward pitching moment) generated by your engine, compared to one at the original thrust line. Probably enough to put your stab back to the starting point! You may want to raise your engine!

Jerry


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Richard Pike



Joined: 09 Jan 2006
Posts: 1520
Location: Blountville, Tennessee

PostPosted: Tue Aug 21, 2018 3:27 pm    Post subject: Re: Kolb-List:Stabilizer Angle Reply with quote

Great post Jerry; thanks.
FWIW - You can do a pretty good job of streamlining the round lift struts with a length of aluminum flashing, folded over and JB Welded (Liquid Nails, double stick carpet tape, etc) to your strut, with some aluminum duct tape around the front side to seal it up. You only fair the rear side. Not ideal, but a great improvement over a round tube.

Or you can get really serious like Jack Hart: http://jackbhart.com/firefly/firefly91.html


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Richard Pike
Kolb MKIII N420P (420ldPoops)
Kolb Firefly Part 103 legal (Repairing the fiberglass nose bowl. Ugh.)
Kingsport, TN 3TN0

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PostPosted: Tue Aug 21, 2018 6:46 pm    Post subject: Kolb-List:Stabilizer Angle Reply with quote

my Firestar was heavy with Aerothane paint 417# empty,but within the cg range spec.It required forward stick.I raised the horizontal in 1/2” increments to a max of 2 1/2” above stock.still needed a trim spring (nose down).But it wallowed around in rough air like a boat climbing over a wake before returning to level flight.I added two small bags of shot, cannot remember the weight,sorry,to the nose cone which put it closer to the forward limit.I could not believe the difference that it made in the stability and handling.I then dropped the stabilizer down to about 1”over stock and thats how it flew for the next 700 hrs.a 503 with an IVO and oil injection,5200 rpm static and 70mph at 5500rpm.I loved that FS. G.Aman FS2 503 750hrs MK3C jabiru 2200A 1060hrs
[quote] O n Aug 20, 2018, at 9:58 PM, Bill <victorbravo(at)sbcglobal.net> wrote:



Full throttle on takeoff and climbout gives me 5700-5800 rpm which is max continuous power. This yields 40-45mph climbing. I have not done extended full power in level flight yet but based on what I have seen so far I would expect 50-52mph and 6000 rpm. Brand new Tiny Tach installed per direct verbal installation instructions on the phone with their tech guy. Airspeed indicator tested with this same air probe stuck out thru the car sunroof, measured same as my car speedometer. Unless experienced Kolbers suggest otherwise, I will put on the short windshield as the next change. How much speed is typical improvement going from round to streamline struts??

Sent from my Samsung Captivate(tm) on AT&T

Stuart Harner <stuart(at)harnerfarm.net> wrote:

>
>
> Bill,
>
> Very glad it is not a CG problem and that it has been definitively ruled out. Sorry for the extra work, but the symptoms called for the effort to be expended.
>
> So now, we know that changing the angle of the horizontal stabilizers helped with the issue considerably even if it is "out of spec".
>
> We have already discussed the wing center section gap seal, and that would be my next area of experimentation. After all you can change that without making any structural changes and it is easy to go back to what you have.
>
> Another thought has occurred to me about your low airspeeds. A few questions:
>
> Have you done a static full power run to make sure you are getting proper RPM's?
> Or
> Have you done a full power run in the air while straight and level?
>
> Have you confirmed your tachometer with another device?
>
> Have you confirmed your ASI (I know you changed the pitot/static setup) to verify that you are truly getting what you are seeing?
>
> Idea for next flight. While straight and level, go to full throttle and see what happens. You only have to maintain it long enough to get a stable tachometer reading and to see what forces are required at the stick.
>
> At this point I am just tossing out random thoughts in hopes that something ticks in your mind to say "hey, what if I did this?".
>
> Hang in there, we're all pulling for you to figure this out.
>
> Some people like mysteries, I rather tent to like the solutions!
>
> Keep us informed,
>
> Stuart
>
> --


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