HoosierSMW

I've watched most of TJay's videos. Very well done and a talented guy. The way he made his new wing ribs is almost exactly how I set up to do mine. I have access to a laser so making the hangars is no problem. Just trying to get the orientation right so I don't have any weird handling issues. 

Got it - Thank you Sir! I thought I had seen them only on top but wasn't sure after seeing your picture.

Do all the later Kitfoxes have an upper and lower 2pc bracket like this?

Thank you Jim. I appreciate you taking the time to help me out. This picture helps a lot.

Unfortunately, this kit came with 3/4" lift struts which I understand lowered the gross weight. If I could find some 7/8" struts (or get better at tig welding), I would substitute them. The ribs are spaced closer than the stol wing. 

My kit originally was an aerobatic speedwing with .083" spar tubes. I am (very slowly) building new wings with .063 tubes and Just Aircraft spar stiffener inserts. I believe they are the same inserts as Kitfox currently uses. The new wings should be plenty strong for a higher gross but my guess is the plane would then be limited by the fuselage construction and struts. would be nice to know the structural differences with the MkIV. Specifically tube diameters and wall thickness in critical areas. I've seen the extra gussets in a few places but can't imagine they are the only changes.

I stand corrected. I had not seen the model letter on anything else. Thanks for the information. Mine was delivered in August of 1990 so obviously would be a C based on that.

Thank you for sharing. I haven't been on skis since I was a kid in the Cub with dad back in the 60's. Loved it and would love to do it again. Don't get as much snow as we used here in the plains of Indiana though. I see you are in Minnesota. Vacationed in the Boundry Waters every summer as a kid. Best memories of my life. Watched it get a lot busier through the years and wonder what it is like now.

The article I referenced above by Mr. Larsen says by 1990 they were into production of the D model. Did the company ever reference the different models "A, B, or C) in any of their literature or kit paperwork? I see those letters all around the web but not in official company statements. The brochures available don't seem to mention a letter designation. It seems they were all called the Avid Flyer until the MkIV was introduced. I could be wrong (not out of the realm of possibility:)
Thanks for all the input.

Did the A model have smaller carry through tubes? I wonder if that is an area of concern. In all the searching and reading I have done on the subject, I have never seen a mention of failure in that area for any of the models. Of course, that doesn't mean is hasn't happened. 

Thank you for that information Mark. That was what I took from the article. Do you know what was different on your plane vs the C model? When Was your kit ordered?

The spar carry-thru tubes are both 7/8" OD x .035 (I measured .040 but don't see that as a stock wall thickness). They are definitely not .049" wall. The seat truss top tube is 5/8" od and the bottom is 1/2" od. This kit was ordered as an aerobatic speedwing but the lift struts are only 3/4" od. I appreciate your help with my questions.

Another question - does the MkIV have larger or thicker spar carry-thru tubes than the C?

My rudder is offset and the frame seems to have all the characteristics of a C. I wish I had a serial number to confirm but it is lost to time and ownership changes. I was curious about a model D because John Larsen, the author of the article, said he had a model D that he made changes to. He said Avid incorporated those changes and made it the MkIV. It seems like that would indicate a version between the C and MkIV. This is a section of the article that had me thinking about this.
("By 1990, many changes had been made and the Model D was in production, but still had the overheating problems. My model D was no different, and since I had years of experience with 2-stroke engines and racing modifications, I began to make changes to cool the planes engine more effectively. I designed the cowling and cooling system that got rid of the cooling problems by placing two radiators in the nose of the cowl.. Changes were also made to the rudder getting rid of the parallelogram rudder for the rounded one. A trim tab was built into the elevator. Dean Wilson was next door building the Explorer so I would run over and get his sanction for many of the new design changes.There was fierce competition between Kitfox and Avid at that time, and KF had just produced their Series 3 plane. Avid GM Jim Metzger chose to produce my design modifications of the Model D and call it the Avid MKIV just to get one PR step ahead of the KF series 3. As a result, there were few Model 3 KF planes produced as Dan Denny at KF began development of their Series 4. The Kitfox was outselling the Avid at the time as the KF had been a better looking plane to many of the buyers.The MKIV was a real after market money maker for Avid, as most of the pilots owning Models A-D ordered up-grade kits to their earlier Models were fitted with MKIV kits to solve the cooling problem and to give them a appearance upgrade so they looked more like a real airplane.") What should the max gross be on this airframe with stol wings? Thanks,Dean

Hello Sir,
Thank you for the quick reply. There is no serial number on any of the paperwork I have. The finish is matt black paint or primer. It did come with a side mount radiator (heavy!!) and was ordered as a tri-gear. Do you have any knowledge of the Model D talked about in the article? Wonder what would be different than the C or MkIV.
RV-8 wings

I appreciate the information and lead. My ship is rigged for a 1 1/4” wide spring. Do you feel the single 5/16” thick spring is stiff enough? I was going to use two 1/4” thick leaves. Thanks.

I am using a 582 so hopefully won't need to add weight to the tail. If I do, I would want it to be useful weight (springs, reinforcements, etc.). I am also thinking about upgrading the tail feathers to MkIV size with a trim tab so that would add some weight as well.

Thanks for the input gentlemen
Jim, do you think the longer spring would put too much stress on the attach point? I was thinking it would allow more flex to protect the structure but may be wrong there. The vertical pivot is angling back a little and the spring does need to be bent a little more. I don't know how much the tail will sag when loaded so I will just have to experiment with that. I am going with two leaves as I don't think the single one will be strong enough. Would I weld in another tube to the spring bracket for the bolt to go through like the original bolt has?
Dusty, I like the idea of a continuous arc to the tailwheel but not sure if I have the equipment to form it. I have access to a press brake with radius dies but not that large of a radius. Our forming rolls may work but would be difficult to end up at an exact angle. I could probably use the press to make a final kink to get just the right angle. May need to play with that one. Sounds like a little shorter spring with the continuous arc would be ideal. 
 

Would it be beneficial to have 1 or 2 pucks in the stack with a lower shore rating to allow a small amount of softer travel?

Thanks for the information Randy. This helps ease my mind a lot for my build. I had hoped the reduced washout wouldn't produce dangerous stall characteristics. I may decide to make or buy new tanks so I don't have to fight them to get the wings where I want them. I was thinking I could move the front lift strut attach point inboard to reduce washout. Hopefully that will work without causing other problems. Thanks again, Dean 

Another question - Did the built-in twist in the fuel tanks cause problems with the build? 
Thanks again, Dean