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Steve Boetto
Joined: 11 Jan 2006
Posts: 365
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 Posted: Sat Mar 31, 2007 7:40 pm Post subject: Rudder Trim tabs for MIIIC w/ 912UL |
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In a message dated 3/31/2007 10:58:53 A.M. Eastern Daylight Time, orcabonita(at)hotmail.com writes:
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That say a lot for Bryans building skills. If all the trim tabs on all his planes all turn out to be the same, thats as close to perfect as you will ever get.
Mike
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Mike,
Its not just his planes, on any Kolb built fairly straight, he will recommend the same thing. When he recovered my Firefly (Duanetheplane built) he mounted the same tab. Result, the Firefly flew straight.
steve
do not archive
See what's free at AOL.com.
[quote][b]
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russ(at)rkiphoto.com
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| Posted: Sun Apr 01, 2007 5:40 am Post subject: Rudder Trim tabs for MIIIC w/ 912UL |
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Jack
Nor would I want to fly with a 10-lb weight on one wingtip. But once
in rural Oregon I saw a picture of a Cub that had flown home with a
dressed-out deer, weighing over 100 lb , hanging from the wing-strut
attach point on the left wing!
Amazing it would fly at all -- but the Cub is one very special
aircraft that occasionally does the impossible.
do not archive
Russ kinne
On Mar 31, 2007, at 11:18 PM, Jack B. Hart wrote:
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<jbhart(at)onlyinternet.net>
From: N27SB(at)aol.com
Date: Sat, 31 Mar 2007 07:41:12 EDT
> It is interesting to look at an example of a Tail-less Pusher like a
Long-EZ and see the results. On mine with a 160 hp engine and a
64x79 pitch
wide blade prop there was almost no rudder change across idle to
full power.
P factor and torque are real issues but I agree with the Kolb
Masters that
the main culprit is wash on the vertical tail.
Steve and Kolbers,
Out of curiosity, I looked at the magnitude of the propeller torque
that has
to be resisted by the FireFly in the roll axis for level flight.
Assuming
that under cruise conditions the engine is developing a torque of
40 foot
pounds. Multiplying by the belt ratio (2.7) gives 108 foot pounds
torque
that the air frame must resist. To compensate most add trim some
where in
the roll control system. Another possibility is that one could add
weight
to the propeller down swing wing tip to dynamically balance out the
torque.
I would have to add 108/11 or 9.82 pounds to the right wing tip to
prevent
torque roll off at cruise. For those who are moving up the hp
scale, the
amount could easily double and triple. I would not want to try to
takeoff
or land a FireFly with a 10 pound weight on one wing tip.
Not practical but interesting.
Jack B. Hart FF004
Winchester, IN
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pj.ladd(at)btinternet.com
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| Posted: Sun Apr 01, 2007 7:15 am Post subject: Rudder Trim tabs for MIIIC w/ 912UL |
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came up with the dimensions and photos I shared a couple days ago.>>
Hi John,
I saw the pics. Very neat. You didn`t intend it to work loose did you?
Challengers come with a clear perspex adjustable trim tab which rivets onto
the tail plane trailing edge. I fitted it to one side only. As far as I
could see its main job was to stop the tail plane banging on the ground when
the pilot released the stick .
I never bothered with one on the rudder as she yawed around the sky pretty
much where she wanted to go anyway.
Cheers
Pat
do not archive
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pj.ladd(at)btinternet.com
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| Posted: Sun Apr 01, 2007 7:19 am Post subject: Rudder Trim tabs for MIIIC w/ 912UL |
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Newton: Equal and opposite reaction.>>
Hi Dana. Of course you are right. Silly me.
Exit stage left .with knuckles dragging on the ground.
Cheers
Pat
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Dennis.Kirby(at)kirtland.
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| Posted: Wed Apr 04, 2007 9:44 am Post subject: Rudder Trim tabs for MIIIC w/ 912UL |
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<< Blame Rotax - They build the 912 so it spun the prop in the wrong
Direction.... Mark >>
There may be some truth to this.
When I had the Verner engine on my Mark-III, it flew without the need
for any rudder trim tab. The prop rotated in the opposite direction of
the 912.
Now, with a 912ul on my plane, I need a fairly large trim tab to keep
the yaw string centered.
Dennis Kirby
Cedar Crest, NM
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barry9315
Joined: 16 Jul 2014
Posts: 11
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| Posted: Thu Jul 31, 2014 2:21 pm Post subject: Re: Rudder Trim tabs for MIIIC w/ 912UL |
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Really confussef. if your kolb m 3 x wants to fly left why the hell do you put the rudder trim on the left. trimming the rudder on the right side i would think would even things out
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byoungplumbing(at)gmail.c
Guest
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| Posted: Thu Jul 31, 2014 2:39 pm Post subject: Rudder Trim tabs for MIIIC w/ 912UL |
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before I could make an informed answer I think I would need more
information.... I don’t know much about your set up. let me tell you about
mine and you may come to an answer on yours,,, or I will try again.... I
fly a mk III C with a 912 ul. I did not use a jig when building wings,
ailerons etc.. but with the engine turning counter clockwise (looking from
the back) the equal and opposite reaction had my plane wanting to roll to
the right. I put on an aileron trim tab to remove the left stick pressure
required to fly hands off. the aileron tab is mounted on the bottom of the
left aileron, and bends down a bit. now the plane is flying hands off.
and as I understand the need for the rudder trim is due to the swirling air
from the prop going past the rudder. when I put on a yaw string, I still
needed right rudder pressure to center things up... so I mounted a rudder
trim tab on the left side of my rudder and the bend is to the left. now
I fly hands off straight and level with the yaw string centered without
pilot input. that is my story and I am sticking to it.....
as I understand, those who use 2 stroke engines,,, the prop spins
clockwise looking from the rear, their planes want to roll left (opposite
reaction to the right turning prop) if your plane wants to roll left with
a counter clockwise rotating prop.... my best guess is that something is
not rigged straight.
does anyone else have a better answer?
boyd young
mkIIIc
utah
800 plus hours
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WhiskeyVictor36(at)aol.co
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| Posted: Thu Jul 31, 2014 7:40 pm Post subject: Rudder Trim tabs for MIIIC w/ 912UL |
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In a message dated 7/31/2014 6:22:30 P.M. Eastern Daylight Time, barbob5742(at)gmail.com writes:
| Quote: | Really confussef. if your kolb m 3 x wants to fly left why the hell do you put the rudder trim on the left. trimming the rudder on the right side i would think would even things out
Hi Barry,
If you are using your right foot to maintain straight flight, that means your rudder is swinging to the right, which turns your Kolb to the right, thus making you fly straight. Now install a trim tab on the rudder so you don't have to use your foot pressure. The trim tab can be mechanically attached to either side of the rudder, BUT the bend, or off set of the tab, has to be towards the left (as viewed from the rear of the plane). The trim tab will then push the rudder to the right which will relieve the foot pressure you previously used to maintain straight flight.
How much of a bend? Start with 10 or 15 degrees. Test fly and then bend more or less as needed to get straight flight without using your foot pressure.
Hope this will help you understand how a trim tab works.
Bill Varnes
Original Kolb FireStar - builder & pilot
Audubon NJ
My 20th season flying Kolb
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