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                           Kolb-List Digest Archive
                                      ---
                     Total Messages Posted Sun 04/04/21: 3
           ----------------------------------------------------------
 
 
Today's Message Index:
----------------------
 
     1. 09:27 AM - Re: Thrust line...?  (Rick Neilsen)
     2. 07:37 PM - Re: Thrust line...?  (Richard Pike)
     3. 09:32 PM - Re: Kolb-List Digest: 2 Msgs - 03/30/21  (chic)
 
 
________________________________  Message 1  _____________________________________


Time: 09:27:35 AM PST US
From: Rick Neilsen <neilsenrm@gmail.com>
Subject: Re: Kolb-List: Thrust line...?

Nick/All

It seems like John Hawk did some testing to see the effects of thrust line
changes and found no differences. From that I decided that the best thrust
line would be directly in line with the direction of flight.


There are two factors that are part of the equation, center of drag and
center of balance. The prop on most Kolbs is above the center of drag so we
get pitch changes with power changes. Hang your plane from the center of
balance (CG) position. The CG is forward of the position of the prop but
also fairly close to the CG. Press down on the prop and the plane pitches
up, lift and it pitches down. So if you set the thrust line a bit down from
the direction of flight the plane will pitch down more than it already does
with power increases, not good. Set the thrust line a bit up and the plane
will pitch down less with power increases which is good but it pushes the
plane down and that is really not a good thing.


The moment arm between the CG and the prop is very short in comparison to
the moment arm of the horizontal stabilizer and elevators so any pitch
considerations are most efficiently handled by the tail. So I suggest that
the prop thrust line be set directly in line with the direction of flight
which  is something around 3-5 degrees up from the bottom of the wing.


As usual this is worth what you paid for it.
Rick Neilsen
Redrive VW Powered MKIIIC


On Sat, Apr 3, 2021 at 8:52 PM Nick Cassara <nickc@mtaonline.net> wrote:

>
> Kolbers,
>
> I have been interest in the talk about desired thrust line. I took a piec
e
> line and attached to the front of my engine mount plate, I then walked it
> back to the tail, and lowered the string until it was making contact with
> the whole upper surface of the mount plate. The string ends up 4 inches
> above the end of the boom tube. The center of the prop is 8 inches above
> the string linei.e.12=99=99 above the top of the boo
m tube end.
>
> My Kolbra is the prototype, of the Kolbra=99s.
>
> Nick Cassara
> Palmer, Alaska
>
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>
>

________________________________  Message 2  _____________________________________


Time: 07:37:12 PM PST US
Subject: Kolb-List: Re: Thrust line...?
From: "Richard Pike" <thegreybaron@charter.net>


Appreciate your thoughts Rick. After a couple weeks of experimenting with this
rig, puzzling over it, and reading this, I think tomorrow I will order a couple
more longer bolts so that I can get the engine and thrust line back to what
it was originally (like Kolb had it), just a couple inches higher, because so
far, the closer I get it to original stock, the better it flies. It just needs
a bit more elevation so the prop will clear the tube when the thrust line is
stock.

Wind has  been too contrary & trashy to get any accurate readings yet, but so far
the 3.47:1 box & 72" three blade prop looks like an amazing improvement.

--------
Richard Pike
Kolb MKIII N420P (420ldPoops)
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=501264#501264


________________________________  Message 3  _____________________________________


Time: 09:32:36 PM PST US
Subject: Kolb-List: Re: Kolb-List Digest: 2 Msgs - 03/30/21
From: "chic" <gcechini@msn.com>


You have a 750 LB gross weight and that is what you should watch along with the
weight and balance which is critical......How much does your plane weigh? Mine
is about 400lbs empty so that will leave about 350lbs for people, fuel, & any
luggage/coolers ect. 10 gal gas is 60lbs so that leaves 290lbs in mine for pilot/pass.
I am 6'4" and I fit in mine so your height should work and if you are
290lbs or less you would work in mine! Hope that helps


Read this topic online here:

http://forums.matronics.com/viewtopic.php?p=501265#501265


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