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KIS TR-1 Aerodynamics

 
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bakerocb



Joined: 15 Jan 2006
Posts: 727
Location: FAIRFAX VA

PostPosted: Sun Jul 04, 2010 3:39 am    Post subject: KIS TR-1 Aerodynamics Reply with quote

7/4/2010

Hello Mark, You wrote:

1) "We should also consider that since these planes are home built no two
are exactly alike so they may not have the same exact handling qualities."

True.

2) "One Tomahawk he flew would recover from a spin. Another would not."

Must have been a harsh touch down when it would not.

I also recall reading while that fiasco was going on that the production
Tomahawk wings had fewer leading edge ribs than called for in the original
designed and built test items. This economy measure permitted wing
distortion under load and unpredictable performance results.

3) "I moved my main gear contact point forward by making a flox wedge
between the gear and the fuselage so the main gear is now angled slightly
forward."

I also made this modification during construction. Maybe some day we can
make some exact measurements to see the fore and aft location of our main
gear axles with regard to some accepted base point such as the nose gear
axle or fire wall.

4) "...... this fully eliminate the landing nose slam ......"

But I did not get this definitive result. Maybe I need to start landing with
full nose up trim to ensure the lightest back stick force on touchdown. My
center stop spring bias pitch trim system has undergone some recent changes
as a result of trying to do away with a taped on bent aluminum tab. The Ray
Allen pitch trim motor does not have quite enough travel to fully meet my
needs. It seems pretty well balanced now -- just barely enough nose up and
barely enough nose down at each end of travel so I am reluctant to further
tweak it by changing springs or spacers. It is a bitch to work on because
the system is buried just forward of the pitch control idler.

Are you landing with any engine RPM above idle?

'OC' Baker Says: "The best investment we can make is the time and effort to
gather and understand knowledge."

========================================================
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ftyoder(at)yoderbuilt.com
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PostPosted: Sun Jul 04, 2010 4:30 am    Post subject: KIS TR-1 Aerodynamics Reply with quote

I built in the elevator extension and have always been able to hold the nose
wheel off at touch down.

Why don't we level the plane and drop a plumb line down to the floor from
the firewall and measure to the gear axle centerlines and compare notes.

Tim

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PostPosted: Sun Jul 04, 2010 11:10 am    Post subject: KIS TR-1 Aerodynamics Reply with quote

Hi OC,

Quote:

2) "One Tomahawk he flew would recover from a spin. Another would not."

Must have been a harsh touch down when it would not.

The plane was fully destroyed. The pilot had entered the spin at about 11,500 feet and after 3 turns tried to recover until he was at 4500 feet then removed himself and floated safely to the ground.

Quote:
I also recall reading while that fiasco was going on that the production
Tomahawk wings had fewer leading edge ribs than called for in the original
designed and built test items. This economy measure permitted wing
distortion under load and unpredictable performance results.

This was also what he told the class at the time.

Quote:
3) "I moved my main gear contact point forward by making a flox wedge
between the gear and the fuselage so the main gear is now angled slightly
forward."

I also made this modification during construction. Maybe some day we can
make some exact measurements to see the fore and aft location of our main
gear axles with regard to some accepted base point such as the nose gear
axle or fire wall.

4) "...... this fully eliminate the landing nose slam ......"

But I did not get this definitive result. Maybe I need to start landing with
full nose up trim to ensure the lightest back stick force on touchdown. My
center stop spring bias pitch trim system has undergone some recent changes
as a result of trying to do away with a taped on bent aluminum tab. The Ray
Allen pitch trim motor does not have quite enough travel to fully meet my
needs. It seems pretty well balanced now -- just barely enough nose up and
barely enough nose down at each end of travel so I am reluctant to further
tweak it by changing springs or spacers. It is a bitch to work on because
the system is buried just forward of the pitch control idler.

I have a full manual trim tab like on Rich's original TR1. I am big fan of this simple and fairly direct system.

Quote:
Are you landing with any engine RPM above idle?

No, I generally touch down with power at idle. Depending on the situation, I use a small amount of power to help slow decent but only right at the start of the flair. After that it is back to idle for the actual touch down. I have also landed fully no power from decent to touch down and still have not had a problem with keeping to nose off.

At the moment I can not measure my main gear location since the plane is disassembled for repainting and a new engine but will when I get a chance. I can not find my original notes and calculations on the subject.

Of course having the aircraft loaded to full aft CG helps reduce (mask?) the main gear too far aft situation. But having the main gear more forward helps in any loading condition.

Mark


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bakerocb



Joined: 15 Jan 2006
Posts: 727
Location: FAIRFAX VA

PostPosted: Tue Jul 06, 2010 8:44 am    Post subject: KIS TR-1 Aerodynamics Reply with quote

7/6/2010

Hello Fellow KIS TR-1 Builders and Flyers, I am impressed with the number of
postings on this subject -- not all under the same subject line. Obviously
the interest is fairly high, at least among a few of us.

For those interested in learning more about the effects of wing to fuselage
interface effects on airflow going back to the horizontal tail surfaces you
might investigate the RV-8 situation. I won't try to bias what you might
learn in that arena, but let me say a few words about strakes versus vortex
generators.

The two terms are used indiscriminately by many writers so there apparently
is no commonly accepted distinguishing definition between the two terms or
devices. An opinion that I hold is that the primary function of a strake is
to change the direction of airflow while the primary function of a vortex
generator is change the nature of the airflow energy from streamlines to
turbulence by generating a vortex, but this opinion is not universally held.

Strakes tend to be fewer in number and large while vortex generators tend
to be smaller in number and many used. It is possible that one kind of
device, regardless of how named, could perform both functions.

Just google some terms like strakes, vortex generators, RV-8 airflow, and
the like and you will be off to the races -- have fun.

'OC' Baker Says: "The best investment we can make is the time and effort to
gather and understand knowledge."

PS: You might also encounter the fact that automobiles are into airflow
modification devices aside from spoilers.


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bakerocb



Joined: 15 Jan 2006
Posts: 727
Location: FAIRFAX VA

PostPosted: Thu Jul 08, 2010 3:21 am    Post subject: KIS TR-1 Aerodynamics Reply with quote

7/8/2010

Hello Tim, You wrote:

1) "I would be interested to see your numbers."

I am working on a spread sheet to compare some numbers. I'll post it when
finished.

2) "Oh, Mark and 'OC' what was the thickness of your main gear shims? Are
they
fiberglass or aluminum or???"

I used a liquid shim of epoxy and glass fibers -- no specific thickness --
just whatever thickness resulted from the gear cross piece squished down
into the shim while tilted forward as much as considered feasible. Actual
final location of the main gear will be shown on the spread sheet.

'OC' Baker Says: "The best investment we can make is the time and effort to
gather and understand knowledge."

=============================================================

KIS-List message posted by: "F. Tim Yoder" <ftyoder(at)yoderbuilt.com>

Mark, 'OC' and all,

My gear dimensions are as follows;
Main gear axle center line to firewall is 42 1/8"
" " " " " " nose gear axle center line 53"

I would be interested to see your numbers.

In retrospect, I do have to watch and may have to increase stick pressure in
order to keep the nose gear off the runway. But I do have plenty of elevator
authority to do that.

Julian's plane was a tail dragger (conventional) I think. He was trying to
give it STOL qualities, an oxymoron I think. I forget what he built to
replace the KIS, I think it is a high wing with better STOL qualities.

Mark, I am in annual now, but I will try and report on your take off
procedure. That is if I don't stall, crash, and burn!

Also, maybe it would be helpful to confirm final approach and touch down
speeds from the GPS, if available, to confirm the accuracy of our different
pitot systems at slow speeds. I you are flying alone, it might be safest to
do this at altitude in a practice area.

'OC', maybe Mark and Rich are just better pilots than you and I because I
use your technique for more consistent landings.

Oh, Mark and 'OC' what was the thickness of your main gear shims? Are they
fiberglass or aluminum or???

Tim


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PostPosted: Thu Jul 08, 2010 6:48 am    Post subject: KIS TR-1 Aerodynamics Reply with quote

Hi Tim,

I did about the same thing as OC when making the shim. I taped a thin rubber sheet to the gear so the flox would not stick and there would be room for the rubber. Then put a excess amount of flox piled on the gear cross area. The flox was about 1/2 inch thick at the back edge and thin at the front edge and slightly convex. I was careful to make sure there were not any voids near the areas where the gear bolts attach the gear. Then I placed the gear into the tunnel and bolted it on place with well greased bolts making sure the main gear tires contacted the ground at the correct location.

So, I really do not know how thick the shim is. I just know that the shim was made so that the main gear contact point is at the correct location. And at the moment I can not find my notes on the location.

For this shim when I say flox I think I used not only cotton but also short chopped fiberglass in the mix. I did not use all chopped fiberglass but I am sure that also works well.

Mark

Quote:
I used a liquid shim of epoxy and glass fibers -- no specific thickness --
just whatever thickness resulted from the gear cross piece squished down
into the shim while tilted forward as much as considered feasible. Actual
final location of the main gear will be shown on the spread sheet.


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PostPosted: Thu Jul 08, 2010 12:45 pm    Post subject: KIS TR-1 Aerodynamics Reply with quote

Thanks Mark,

Tim
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