Kolb-List Digest Archive

Sun 04/04/21


Total Messages Posted: 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


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    Time: 09:27:35 AM PST US
    From: Rick Neilsen <neilsenrm@gmail.com>
    Subject: Re: 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 > =========== =========== =========== =========== =========== > >


    Message 2


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    Time: 07:37:12 PM PST US
    Subject: 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


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    Time: 09:32:36 PM PST US
    Subject: 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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