Today's Message Index:
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1. 06:58 AM - Re: Strange Flying characteristics of new to me Mark III clasic (Ralph B)
2. 07:55 AM - Re: Re: Strange Flying characteristics of new to me Mark III clasic (John Hauck)
3. 08:20 AM - Re: Strange Flying characteristics of new to me Mark III clasic (Ralph B)
4. 03:25 PM - Re: Re: Strange Flying characteristics of new to me Mark III clasic (John Hauck)
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Subject: | Re: Strange Flying characteristics of new to me Mark III clasic |
I failed to mention the Kolbra fin offset was built that way due to the powerful
912 engine that spins in the opposite direction of a 2-stroke engine. From the
rear of the airplane, it spins in a counterclockwise direction whereas a 2-stroke
will spin in a clockwise direction. This makes a difference in how the
airplane is trimmed out. When I upgraded to the 912uls 100hp engine, I was very
happy have that offset built in as the rudder trim tab would not have been able
to hold it without using constant rudder on the pedals. Even then, the airplane
would have been flying in a constant yawed condition which I didn't like.
Ralph B
--------
Ralph B
Kolb Kolbra 912uls
N20386
550 hours
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=470154#470154
Message 2
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Subject: | Re: Strange Flying characteristics of new to me Mark III |
clasic
Don't want to contradict Ralph B, but I have a little different take on the
upper vertical stabilizer leading edge offset.
I tried for a very long time to get Old Kolb Aircraft to experiment with
offsetting the leading edge of the upper vertical stabilizer on the factory
MKIII because I had an idea that this would help remedy the adverse yaw
problem. However, they never did.
At that time I was flying with a rudder trim tab half the length of what I
finally discovered solved the yaw problem.
The reason I didn't want to experiment on my MKIII was because I didn't want
to drill a bunch of holes and screw up my airplane. I had already made a
17,200 mile flight with the slip/skid ball yawed a half ball out, and got
tired of looking at it. My MKIII flew great this way, but it just wasn't
right.
I started out by offsetting the leading edge by 1/2". No observable change.
Drilled out the SS rivets and tried 1". Very slight change. Finally I got
it pushed over to 1.5" with hardly any difference. Not worth all the
effort. On the down side, doing it my way was actually twisting the tail
post and bending the leading edge tube of the upper vertical stabilizer
which eventually failed. Big job repairing this. When I did I went back to
centering the upper vertical stabilizer the way it should be.
Then I decided to experiment with the rudder trim tab. I chose to go big
and built the first one three rib bays long. Wow! That was an overkill.
Since I had attached with duct tape, I snatched it off, cut off a third (one
rib bay), stuck it back on and discovered it was perfect. Slip/skid ball
centered with my feet on the deck. ;-)
I think Mark German modified the tail post on his Kolbra after he saw mine
and talked with me. Cannot remember for sure.
There is no need to offset the upper vertical stabilizer because an adequate
rudder trim tab solves the yaw problem. A much simpler and effective
solution.
Direction of prop rotation and HP did not make much difference to the yaw
problem. I had it with 65, 80, and 100 hp on my MKIII.
John h
mkIII
Fayetteville, NC
I failed to mention the Kolbra fin offset was built that way due to the
powerful 912 engine that spins in the opposite direction of a 2-stroke
engine. From the rear of the airplane, it spins in a counterclockwise
direction whereas a 2-stroke will spin in a clockwise direction. This makes
a difference in how the airplane is trimmed out. When I upgraded to the
912uls 100hp engine, I was very happy have that offset built in as the
rudder trim tab would not have been able to hold it without using constant
rudder on the pedals. Even then, the airplane would have been flying in a
constant yawed condition which I didn't like.
Ralph B
--------
Ralph B
Kolb Kolbra 912uls
N20386
550 hours
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=470154#470154
Message 3
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Subject: | Re: Strange Flying characteristics of new to me Mark III clasic |
John,
While in flight do you have to hold any rudder at all or are your feet neutral
on the pedals with the ball centered? Just wondering ...
The reason I say this is if you have to hold any rudder, then your trim tab is
not working.
I believe Mark German did consult with you and others before offsetting the fin
like that. He didn't want to drill out extra holes in the tube, I'm sure, if
he didn't have to.
As it stands, with my 100hp 912, the only way to keep it from rolling was the offset
fin. If I didn't have that, I would probably need a very large trim tab
as you have.
Ralph B
--------
Ralph B
Kolb Kolbra 912uls
N20386
550 hours
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=470159#470159
Message 4
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Subject: | Re: Strange Flying characteristics of new to me Mark III |
clasic
Yes sir, I fly can with my feet off the pedals and on the deck with centered
slip/skid ball, as I indicated in my original comment.
John h
mkIII
Fayetteville, NC
-----Original Message-----
From: owner-kolb-list-server@matronics.com
[mailto:owner-kolb-list-server@matronics.com] On Behalf Of Ralph B
Sent: Thursday, June 15, 2017 11:21 AM
Subject: Kolb-List: Re: Strange Flying characteristics of new to me Mark III
clasic
John,
While in flight do you have to hold any rudder at all or are your feet
neutral on the pedals with the ball centered? Just wondering ...
The reason I say this is if you have to hold any rudder, then your trim tab
is not working.
I believe Mark German did consult with you and others before offsetting the
fin like that. He didn't want to drill out extra holes in the tube, I'm
sure, if he didn't have to.
As it stands, with my 100hp 912, the only way to keep it from rolling was
the offset fin. If I didn't have that, I would probably need a very large
trim tab as you have.
Ralph B
--------
Ralph B
Kolb Kolbra 912uls
N20386
550 hours
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=470159#470159
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