---------------------------------------------------------- Kolb-List Digest Archive --- Total Messages Posted Thu 06/15/17: 4 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 06:58 AM - Re: Strange Flying characteristics of new to me Mark III clasic (Ralph B) 2. 07:55 AM - Re: Re: Strange Flying characteristics of new to me Mark III clasic (John Hauck) 3. 08:20 AM - Re: Strange Flying characteristics of new to me Mark III clasic (Ralph B) 4. 03:25 PM - Re: Re: Strange Flying characteristics of new to me Mark III clasic (John Hauck) ________________________________ Message 1 _____________________________________ Time: 06:58:28 AM PST US Subject: Kolb-List: Re: Strange Flying characteristics of new to me Mark III clasic From: "Ralph B" I failed to mention the Kolbra fin offset was built that way due to the powerful 912 engine that spins in the opposite direction of a 2-stroke engine. From the rear of the airplane, it spins in a counterclockwise direction whereas a 2-stroke will spin in a clockwise direction. This makes a difference in how the airplane is trimmed out. When I upgraded to the 912uls 100hp engine, I was very happy have that offset built in as the rudder trim tab would not have been able to hold it without using constant rudder on the pedals. Even then, the airplane would have been flying in a constant yawed condition which I didn't like. Ralph B -------- Ralph B Kolb Kolbra 912uls N20386 550 hours Read this topic online here: http://forums.matronics.com/viewtopic.php?p=470154#470154 ________________________________ Message 2 _____________________________________ Time: 07:55:49 AM PST US From: "John Hauck" Subject: RE: Kolb-List: Re: Strange Flying characteristics of new to me Mark III clasic Don't want to contradict Ralph B, but I have a little different take on the upper vertical stabilizer leading edge offset. I tried for a very long time to get Old Kolb Aircraft to experiment with offsetting the leading edge of the upper vertical stabilizer on the factory MKIII because I had an idea that this would help remedy the adverse yaw problem. However, they never did. At that time I was flying with a rudder trim tab half the length of what I finally discovered solved the yaw problem. The reason I didn't want to experiment on my MKIII was because I didn't want to drill a bunch of holes and screw up my airplane. I had already made a 17,200 mile flight with the slip/skid ball yawed a half ball out, and got tired of looking at it. My MKIII flew great this way, but it just wasn't right. I started out by offsetting the leading edge by 1/2". No observable change. Drilled out the SS rivets and tried 1". Very slight change. Finally I got it pushed over to 1.5" with hardly any difference. Not worth all the effort. On the down side, doing it my way was actually twisting the tail post and bending the leading edge tube of the upper vertical stabilizer which eventually failed. Big job repairing this. When I did I went back to centering the upper vertical stabilizer the way it should be. Then I decided to experiment with the rudder trim tab. I chose to go big and built the first one three rib bays long. Wow! That was an overkill. Since I had attached with duct tape, I snatched it off, cut off a third (one rib bay), stuck it back on and discovered it was perfect. Slip/skid ball centered with my feet on the deck. ;-) I think Mark German modified the tail post on his Kolbra after he saw mine and talked with me. Cannot remember for sure. There is no need to offset the upper vertical stabilizer because an adequate rudder trim tab solves the yaw problem. A much simpler and effective solution. Direction of prop rotation and HP did not make much difference to the yaw problem. I had it with 65, 80, and 100 hp on my MKIII. John h mkIII Fayetteville, NC I failed to mention the Kolbra fin offset was built that way due to the powerful 912 engine that spins in the opposite direction of a 2-stroke engine. From the rear of the airplane, it spins in a counterclockwise direction whereas a 2-stroke will spin in a clockwise direction. This makes a difference in how the airplane is trimmed out. When I upgraded to the 912uls 100hp engine, I was very happy have that offset built in as the rudder trim tab would not have been able to hold it without using constant rudder on the pedals. Even then, the airplane would have been flying in a constant yawed condition which I didn't like. Ralph B -------- Ralph B Kolb Kolbra 912uls N20386 550 hours Read this topic online here: http://forums.matronics.com/viewtopic.php?p=470154#470154 ________________________________ Message 3 _____________________________________ Time: 08:20:59 AM PST US Subject: Kolb-List: Re: Strange Flying characteristics of new to me Mark III clasic From: "Ralph B" John, While in flight do you have to hold any rudder at all or are your feet neutral on the pedals with the ball centered? Just wondering ... The reason I say this is if you have to hold any rudder, then your trim tab is not working. I believe Mark German did consult with you and others before offsetting the fin like that. He didn't want to drill out extra holes in the tube, I'm sure, if he didn't have to. As it stands, with my 100hp 912, the only way to keep it from rolling was the offset fin. If I didn't have that, I would probably need a very large trim tab as you have. Ralph B -------- Ralph B Kolb Kolbra 912uls N20386 550 hours Read this topic online here: http://forums.matronics.com/viewtopic.php?p=470159#470159 ________________________________ Message 4 _____________________________________ Time: 03:25:52 PM PST US From: "John Hauck" Subject: RE: Kolb-List: Re: Strange Flying characteristics of new to me Mark III clasic Yes sir, I fly can with my feet off the pedals and on the deck with centered slip/skid ball, as I indicated in my original comment. John h mkIII Fayetteville, NC -----Original Message----- From: owner-kolb-list-server@matronics.com [mailto:owner-kolb-list-server@matronics.com] On Behalf Of Ralph B Sent: Thursday, June 15, 2017 11:21 AM Subject: Kolb-List: Re: Strange Flying characteristics of new to me Mark III clasic John, While in flight do you have to hold any rudder at all or are your feet neutral on the pedals with the ball centered? Just wondering ... The reason I say this is if you have to hold any rudder, then your trim tab is not working. I believe Mark German did consult with you and others before offsetting the fin like that. He didn't want to drill out extra holes in the tube, I'm sure, if he didn't have to. As it stands, with my 100hp 912, the only way to keep it from rolling was the offset fin. If I didn't have that, I would probably need a very large trim tab as you have. Ralph B -------- Ralph B Kolb Kolbra 912uls N20386 550 hours Read this topic online here: http://forums.matronics.com/viewtopic.php?p=470159#470159 ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message kolb-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/Kolb-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/kolb-list Browse Digests http://www.matronics.com/digest/kolb-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.