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Lynn Matteson
Joined: 10 Jan 2006 Posts: 2778 Location: Grass Lake, Michigan
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Posted: Tue Jan 27, 2009 11:46 am Post subject: KF IV Distance from DATUM to center of wheel |
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Actually, Lowell, it was 43 lbs when weighed level. Then I added a
transponder, so a few ounces would have gone in the direction of the
tail, but not much. Maybe with the extra leaf of the 3-leaf spring,
it might be up to 45 by now.
Lynn Matteson
Kitfox IV Speedster, taildragger
Jabiru 2200, #2062, 600.2 hrs
Sensenich 62x46
Electroair direct-fire ignition system
New skis done and flying
On Jan 27, 2009, at 11:02 AM, Lowell Fitt wrote:
[quote]
<lcfitt(at)sbcglobal.net>
Paul,
That is the problem I find with math. The typical weight if the
Grove gear including fasteners and axle is 30 lbs and that was on
personal inquiry from Grove. In my head you would be moving a 30
lb. wt. forward about 10 inches or so by my guess - no math, just
looking at my uncovered fuselage and where his gear is and where
mine is.
Regarding the 55 lbs. That was calculated based on my tailwheel wt.
vs. gross wt. and my airplane flew fine with full three point
elevator authority. Lynn Matteson said his tailwheel wt was in the
55 lbs. range as well and that was at 6.25%. Maybe it is time for
another survey .
Lowell
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_________________ Lynn
Kitfox IV-Jabiru 2200
N369LM |
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Lynn Matteson
Joined: 10 Jan 2006 Posts: 2778 Location: Grass Lake, Michigan
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Posted: Tue Jan 27, 2009 12:57 pm Post subject: KF IV Distance from DATUM to center of wheel |
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Seems like my mains were 1/2" ahead of datum (leading edge of wing)
or behind...can't recall which. This is with Grove gear.
Lynn Matteson
Kitfox IV Speedster, taildragger
Jabiru 2200, #2062, 600.2 hrs
Sensenich 62x46
Electroair direct-fire ignition system
New skis done and flying
do not archive
On Jan 27, 2009, at 1:03 PM, Noel Loveys wrote:
[quote]
Re ran my calculations for a 65 lb tail wheel the answer comes out
that the
main wheel should be .41 in ahead of the datum. This maintains the
current
C of G
Noel
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_________________ Lynn
Kitfox IV-Jabiru 2200
N369LM |
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Lynn Matteson
Joined: 10 Jan 2006 Posts: 2778 Location: Grass Lake, Michigan
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Posted: Tue Jan 27, 2009 1:00 pm Post subject: KF IV Distance from DATUM to center of wheel |
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Better a loop than a nose-over.
Lynn Matteson
Kitfox IV Speedster, taildragger
Jabiru 2200, #2062, 600.2 hrs
Sensenich 62x46
Electroair direct-fire ignition system
New skis done and flying
do not archive
On Jan 27, 2009, at 2:35 PM, Noel Loveys wrote:
Quote: |
I just did a search on the web to try to get a handle on what the
weight on
the tail wheel should be for similar configured airplanes, if not
similar
weight. I checked C-180s and Pa-18s They both have the tail wheel
out under
the rudder. They were all around 5.5% of total weight on tail give
or take
0.1% except for one Super Cub that was way down at 4.6% and that
guy was
having problems with his W&B.
Going by that search, and limited data, I calculated the tail of
the plane
should be around 48.68 lb. Give or take a pound or two. To get that
weight
on the tail wheel without changing the CG would require the mains
be located
2.31 in aft of the datum. I double checked the calculations and that
includes the movement of the weight of the mains. I think he will
be safe
by moving the mains 5" ahead. His plane should have the same flight
characteristics but be a lot safer landing.
Any way we want to cut the grass I think we all concur that the
mains are
much too far aft to be safe if any braking is to be used. If he
doesn't
mind loooooooong run outs and stays away from rough strips the gear
that far
aft probably somewhat reduces the possibility of a landing loop as
does the
far aft gear on a tricycle gear plane.
Noel
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_________________ Lynn
Kitfox IV-Jabiru 2200
N369LM |
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Float Flyr

Joined: 19 Jul 2006 Posts: 2704 Location: Campbellton, Newfoundland
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lcfitt(at)sbcglobal.net Guest
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Posted: Tue Jan 27, 2009 4:25 pm Post subject: KF IV Distance from DATUM to center of wheel |
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For sure, Noel, then comes the flight testing and the tweaking to correct
for the math, making everything correspond to the desired performance. In
some of the articles I found on airfoils, Mr. Riblett was criticized for
having never subjected any of his designs to wind tunnel testing. And this
criticism was from aeronautical engineers - very much versed in math. So
much for math as the last word IMHO. In fact in one article, talk was of
one engineer working on one of the recent jet fighter wings doing all sorts
of things with numbers on his computer and in frustration, a senior
engineer, took a piece of flat plywood did some minor leading edge shaping
(by hand) and got wind tunnel results quite similar to the highly designed
wing profile.
It is sort of like a lot of our discussions, we all know what should happen,
then some curious guy actually tries it - take VGs for example and finds
results that vary considerably from expectations and the arguments begin.
On the Lancair list - while I was helping on that project - a guy built a
Lancair IV and made removable wingtips of both designs, the straight tip and
the winglet tip. He tested both tips on the same airframe. He found that
with the winglets, he lost cruise speed and everyone knew that was
impossible and the flames began there too.
Lowell
do not archive
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Float Flyr

Joined: 19 Jul 2006 Posts: 2704 Location: Campbellton, Newfoundland
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Posted: Tue Jan 27, 2009 4:28 pm Post subject: KF IV Distance from DATUM to center of wheel |
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Point, Match & Game Matteson.
Noel
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_________________ Noel Loveys
Kitfox III-A
Aerocet 1100 Floats |
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dcubj3(at)terra.com.br Guest
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Posted: Tue Jan 27, 2009 4:31 pm Post subject: KF IV Distance from DATUM to center of wheel |
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Mr.
Lynn Matterson
Noel Loveys
Jan - JC Propeller Design
Tom Jones
Paul Franz - Merlin GT
Guy Buchanan
Tks a lot!!! For all infomations !
I will read carefully all of emails with sugestions and will send you news
when take a decision.
Tks
FD
www.dcubj3.com.br
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dcubj3(at)terra.com.br Guest
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Posted: Tue Jan 27, 2009 5:23 pm Post subject: KF IV Distance from DATUM to center of wheel |
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Mr. Noel
The first decision was change laminar "grove type" gear to "tube bush" gear
less weight, more realiable
after two weeks of work (I think) I will do a new W&B
after that I will send you news
Tks a lot for useful information
FD
www.dcubj3.com.br
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Float Flyr

Joined: 19 Jul 2006 Posts: 2704 Location: Campbellton, Newfoundland
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Posted: Tue Jan 27, 2009 6:17 pm Post subject: KF IV Distance from DATUM to center of wheel |
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As a photographic technician I have spent a good part of a lifetime working
with simple math...and it has yet to fail me. The math I use is nothing
compared to fluid dynamics or structural analysis. That stuff is so far out
of my league I hope I spelled it right.
I think we all agree the mains are too far back for comfort.
Noel
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_________________ Noel Loveys
Kitfox III-A
Aerocet 1100 Floats |
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Float Flyr

Joined: 19 Jul 2006 Posts: 2704 Location: Campbellton, Newfoundland
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Posted: Tue Jan 27, 2009 8:04 pm Post subject: KF IV Distance from DATUM to center of wheel |
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I'll be waiting to hear how it turns out for you.
Noel
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Kitfox III-A
Aerocet 1100 Floats |
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Lynn Matteson
Joined: 10 Jan 2006 Posts: 2778 Location: Grass Lake, Michigan
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Posted: Wed Jan 28, 2009 11:30 am Post subject: KF IV Distance from DATUM to center of wheel |
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Absolutely!...pardon me, I've got something in my eye...wink,
wink....there, I think I've got it. : )
Actually no, no W&B....I just carved some of my prop away to make up
for it...(it didn't take much, either)
Lynn Matteson
Kitfox IV Speedster, taildragger
Jabiru 2200, #2062, 600.2 hrs
Sensenich 62x46
Electroair direct-fire ignition system
New skis done and flying
do not archive
On Jan 27, 2009, at 7:18 PM, Noel Loveys wrote:
[quote]
Did you do a W&B amendment for that leaf?
Noel
Sorry I get too caught up in the darn paperwork.
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_________________ Lynn
Kitfox IV-Jabiru 2200
N369LM |
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Float Flyr

Joined: 19 Jul 2006 Posts: 2704 Location: Campbellton, Newfoundland
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Posted: Wed Jan 28, 2009 6:59 pm Post subject: KF IV Distance from DATUM to center of wheel |
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Congrats!! Add weight to one end of the teeter totter and ya gotta add
weight to the other end too. LOL
Noel
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_________________ Noel Loveys
Kitfox III-A
Aerocet 1100 Floats |
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