I built one of these LRI and flew with it a while but found that it just wasn't for me. Found that it was better to listen/feel the airplane and respond without distracting me from the job at hand. I still have it around somewhere and the patched hole in the panel to remind me Your mileage my very.
Even with the Zipper Kit and others there have been failures with the older engines. Hal of Zipper fame will not buy the older UL engines for up grade pre 2006 if I recall. I would give Ronnie Smith at Mississippi Light Aircraft a call they also sell a low compression upgrade kit he or his son will give you the actual serial number cutoff for the older engines. Maybe if you go the route that flywise suggests above it would be okay but why not pickup a good used ULS and go fly. All that said I do have my used Zipper kit that I will sell that I had on my early 90's UL for $2500 USD. It has about 200 hrs on it but I would have to look back at the logs for the actual number of hrs if anyone is interested. I lost confidence in the upgrade after a friends engine failed within fifty hour of installation ( Larry's old plane and engine that we upgraded after my friend bought it) There is my nickel worth. I bought a new ULS after I lost confidence in the upgrading the old engines. If I had a later model UL I would still be flying the Zipper.
The yoke "H" needs to be loose enough to move freely so that it acts as a universal joint in addition to Leni's comment. I'm fine with the friction flap handle when properly adjusted holds great and allows precise adjustment albeit somewhat rather stiff.
The thread on the Avid is a 10-32 and it was the F7a that used the 1/4" tube with a socket head screw welded in both ends supplied by some. My welder did not like that idea so the ones that I supplied were constructed differently but at any rate I do believe that the original parts for both Avid and KF were a speciality part. I looked at grade eight all thread but found some long grade 8 set screws to do the job but not sure if they make any long enough to use in the standard application. I would be comfortable using the grade 8 all thread but that is just me. https://www.mcmaster.com/all-thread-rods
Everything looks ok in the fuselage in the tail section? There was a post several days ago about the failure of the rudder hinges on another 4. Is there any other folks flying Avids or KF in your area that can help you look at the plane? Perhaps the cable slipped in a Nicropress sleeve if the loop was big or the end left long? The fact that it wanted to climb also is disturbing. How about the return springs everything look ok there?
The tab that is welded on the vertical stab, which holds the tailspring from lateral movement is a weak point. I've seen several of them fail. Avid's mount is better IMHO. We built that sort of mount for one IV and it is holding up well. Also built a plate that mounts under the spring for another where the tabs had bent but not broken but had been bent. The issue presents itself because the spring doesn't have a good flat surface to mount to. With side pressure the spring rolls to the side bending the main bolt and bending or breaking the tabs. Otherwise I have to say I'm pretty impressed with the KF 4. Faster that the Avid just a tiny bit slower to get off the ground. Not a fan of the Grove gear or the so called bush great with the heavy springs, still waiting to see if Leni's suggested fix with the snogo springs will cure the issue. I'm using the Roberts Rage gear with my own gear leg design and I like the TK1 gear of Tony's but both are not cheap. Larry's beefing up of his fuselage surely would be on my list also for both the KF and the Avid. JIm Chuk and many others also documented ways of beefing up the cockpit area of the fuselage,there are a lot of good options out there.
So take a moment to consider the Faa is quietly shutting down the ILS approaches across the country. So what happens when there is no ground based approaches and they are fiddling with the GPS, you have now lost the alternates so you can't fly. What you say why do us puddle hoppers need to worry about not being able to fly IFR, hell lm not even rated. But I bet you like the thought of getting a life flight to come get you if it is IFR, how about those aircraft parts from ACS, Wicks, Kitfox or Amazon.com. You might still have time to campaign in your area to save your ILS, we did here but the fight is not over I'm sure, just postponed. Those of you that fly IFR should think about the implications of how this will affect your livelihood. OK, I'm done.
Hey Randy, looking at your wing build I noticed that you made provision for the flat plate on the wing tip but did not see it in the completed pictures. Are you flying with it now and if so what results are you seeing. Also I'm curious if you considered other shapes for the wing tip with your build or simply a flat plate on the final rib like I've seen on other planes. The Avid wing tip seems to offer little beyond the fact that it is pleasing to the eye but maybe I'm missing something. I'm considering building Hoerner style tips for mine but have not made the final decision although I have ordered some nicrome wire so maybe closer than I think.
I don't believe that was Hoerner's conclusion. He actually wrote a short paper just about wing tips, "AERODYNAMIC SHAPE OF WING TIPS" which is online if searched for. I will refer you to that and you can draw your own conclusions. There is a nice YouTube video of a fellow making some Hoerner tips for his Sonerai. I will try to link to that for those interested. https://youtu.be/ULhZchv7ito