109jb

Thanks, but that one is too narrow at only 26" wide where it bolts to the fuselage.

My airplane with a 582 uses 1/4 lines throughout the fuel system.

Thanks.  That's what I suspected. 

Just a dumb question I have. Will a 912UL continue to windmill if the fire goes out at normal Kitfox glide speeds? Or will the prop eventually stop. Specifically, a 80 hp 912UL with a 3 blade GSC wood prop, but any info is good.  Thanks.

Where in the world did he put these to make the stall so dangerous? 

A gentle stall progresses from inboard to outboard. The tip stalling first is what you don't want. He could have placed the vortex generators only on part of the wing. For instance if he placed them inboard but not outboard  the VGs would delay the stall at the root but the tip remains unchanged. This could have resulted in the tips stalling first. Just one possible scenario but there could be others.

Pretty harsh criticism guys.  I found the video to be informative and presented a well thought out and well executed series of tests,  including their results and evaluation criteria. 

I agree with Willja67 that he was commenting on a stall test in which they had installed vortex generators in such a way that it aggravated the stall characteristics drastically enough that they almost created an unrecoverable spin condition.

If all thread is used then you would need 2 right hand heim joints. No left hand heim joints would be needed. Just won't be able to adjust it like a turnbuckle and will have to take a rod end loose to adjust.

I'm considering replacing the stock landing gear on my Kitfox IV with something else.  I figured I'd put some feelers out there for anyone who may have a grove gear for the Kitfox that they may want to get rid of.  I figure there may be some out there gathering dust with all of the cabane bush gear conversions that are going on.  Let me know what you have, where you are and how much you want.

Thanks,

John B

I have definitely drooled over your airplane and love the mods you have done.  Can I ask what your Mangy Fox came in at for empty weight and what engine you have in it?

Oops. I see it has a 912UL with the 105 hp zipper conversion

Well OK.  The primary mission is the typical mission for a Kitfox IV. Mostly just bombing around airport to airport, paved strips, grass strips. Ocassionally I will be landing on unimproved landing areas from time to time, mainly farm fields (sometimes a bit rough), and pastures of friends and family I have, and I'd like to take it out west at some point too. I'll be retiring in about 5 years and after that want to do a lot of grass-roots flying and experiencing as much as I can. Basically doing the flying that I couldn't do for the past 30 years raising kids and such. I want it to be a fast as is possible but that isn't a determining factor in the mission or modifications except that I'll do some lightweight fairing of things. I have a SES certificate so throw some amphibious floats on it at some time or another too. I like to build so will probably do Zenith amphibs. Because of where I live and where I want to fly I will have to have ADS-B out, Mode-C transponder, and comm radio, but the rest of the panel will only be a  G5x, an appropriate engine monitor and a tablet for navigation. No fancy heavy upholstery, just comfortable and lightweight. Covering I would love to do Oratex if it is in the budget when I get to that point, again to save weight as I don't consider oratex to be pretty. Modifications I want to do are those that are worthwhile for any of the above missions that are worth the weight penalty. Again I don't want to build an 800 pound Kifox IV so I will assess each suggestion very carefully.

Added a few more to the first post.  

Based on my experiences I'd say the manufacturer's numbers are probably pretty darn close for a properly running engine.

I have had the opportunity to run accident aircraft engines at manufacturer facilities in certified test cells . You'd probably be surprised but by and large they put out exactly what the manufacturer says they should even after being subjected to an accident.  One I remember in particular was a IO-520 that spent a week under water before recovery. It had less than  10/80 pre-run compression on all cylinders and yet is started, ran fine and produced full rated power. After the run the compressions were all over 50/80. I don't suspect Rotax's would be much different so would guess they would reach their rated numbers as well provided they are properly maintained.

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. 

Good to know. I'll definitely look at beefing that tailspring area up.

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. 

Yeah. I'm not looking for monster gear with 37" tires. The 21" Nanco's on my current kitfox are fine by me. I'd just like a little wider gear than the stock. The Grove does that and eliminates bungy failure concerns, is lower drag but from what I understand a bit heavier. A cabane gear is probably a good compromise and I'd probably build my own. Again, not looking for monster tires or even a taller stance for that matter, just wider for a little better ground stability. Quite honestly the gear decision can be made later since the gear designs I'd consider wouldn't require anything affecting the fabric.

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.

Definitely doing this as it is ounces of material for improving the strength of a known weak point.

Keep em coming.

I'm sorry if I somehow offended you because it wasn't my intention. I just wanted to make clear that I don't want anyone ommitting any potential modification due to some perceived mission profile.

Yes, I will decide if the mods  people suggest fit my mission and if I will incorporate them, but quite frankly that is not something you need to know. It is something for me to know and to decide.  I am intentionally not listing my exact mission specifics because I don't want to limit responses.

Also I am not only looking for airframe modifications, but all modifications. Nothing is too trivial.  Heck, even something like "weld a tab for a go-pro mount here" is welcome.

Admittedly it has been a several years. Last time was an ASR approach at Willard Field in Champaign, IL.

Yeah, the basic airframe is good but I'm looking for any kind of mod. Even something like an extra welded tab for a whatzit isn't off limits.

I may be able to get a Kitfox IV project close by where I live. It is uncovered and I wanted to get a list of modifications that you guys that have been flying Kitfoxes and Avids for a while have made and feel are worthwhile.  I'm interested in hearing about all modifications, but especially those that are considered mandatory and need to be done before covering. Don't think that any mod is too trivial or simple because I want to try to think of all and incorporate the ones I want during the build rather than try to add on later. I'll start the list below.  If you would when you post let me know if you think a particular mod is mandatory, nice to have, etc. Just so you know some of the parameters, the airplane will be a tailwheel airplane powered by an 80 hp Rotax 912. I'm going for light weight as much as possible.

Modifications List

1. Comply with all Kitfox service bulletins and service letters

2. Reinforce fuselage sides where landing gear mounts

3. Reinforce landing gear truss where bungees attach

4. Different main landing gear (Grove, cabane type, other) (I'll probably go with cabane type gear)

5. Larger pneumatic tailwheel  (Probably a 8" Matco)

6. In flight adjustable elevator trim tab. (Electric or manual)

Added to list from suggestions:

7. Beef up tailspring mount area.

8. Inspection ring near tailwheel spiring bolts

9. Ground plane for antenna mount

10. Widen fuselage at seat back (Murle Williams kit or other)

11. Relocate shoulder harness mount so that straps don't fall off shoulders. 

There is always PAR and ASR approaches. Fun to practice too if the facility isn't too busy.

Where do you see a UL power for under $10k. From Sonex the UL260i is $20k. UL power doesn't list prices on their website that I can find. 

There is another article "Kitfox Arrives" in Flying magazine October 1992 that describes it more clearly.

"Denney says he tested a 1,050-pound airframe to destruction to ascertain which areas needed beefing up for a 1,200-pound limit The airframe was loaded with weight equivalent to 5. 7 Gs at 1,550 pounds, which produced some deformation in the wing attach pins. At 1,600 pounds there was a quarter-inch permanent displacement at the tips of the spars. At 1,650 pounds the fuselage tore apart at the tube that runs across its bottom and connects the two liftstrut attach brackets; thicker-wall tubing is now used here. The steel-tube lift struts of the 1,050-pound airplane also wouldn't take -2.85 Gs at 1,200 pounds, so they have been changed on the 1,200-pounder to one-inch diameter with a wall thickness of .049 inches, compared with 7 /8ths and .035. The Kitfox's directional stability has been somewhat lacking, and so the vertical surfaces of the Kitfox IV-1200 have grown in height by seven inches; the rudder chord has been extended by two inches."

For the full article you can find it here if the link works: https://books.google.com/books?id=2dy-fCMhHwYC&pg=PA84&dq=kitfox+arrives&hl=en&sa=X&ved=2ahUKEwin1tfpkIfnAhX1dc0KHdMuD3cQ6AEwAnoECAEQAg#v=onepage&q=kitfox arrives&f=false

I have the plans for that airplane.  It is usually referred to as a Wag-A-Bond rather than a Traveler.   The  plans are indeed a good price.  I would still like to build it but have several projects in front.  It is basically a homebuilt version of the PA15/17 airplanes.  I've not flown in a Wag-A-Bond but have flown in a PA-20 several times many years ago which is a 4-place version of the airplane.The PA-20 is what promted me to buy the Wag-A-Bond plans.  

Not yet.  I have been very busy with other stuff and the airplane is 30 minutes away from me. On top of that it is in a gravel floor hangar that I have to cart my tools out to each time I want to work on it.  All that has slowed the progress of the things I want to get done on the airplane.  The good news is that after being on a waiting list a hangar at the airport 10 minutes from me came available.  I will need to get the airplane moved over and then outfit a bit with tools and then I can get to work. The rudder mod is toward the top of the list of things  I want to do but isn't quite at the top of the list. First on the list is to revamp the engine cooling system, then a tailwheel fix, then the rudder enlargement.

Congrats on the Sonex.  I have no doubt that you will enjoy it and it sounds like it fits your mission profile better.

In regard to the ground handling, nothing against John Monnett, I have a Sonerai IIL which is a great John Monnett design, but to be clear, the aft swept spring rod gear is not a John Monnett creation. It was pioneered by Steve Wittman in the 1930's, and used on the Tailwind and Buttecup airplanes. Also, the tapered rod direct linkage tailspring was also used by Wittman at least as early as his Buttercup built in 1938.

I am aware.  To be clear, my intention was not that it doesn't or can't happen, just that putting a secondary thermostat in will not change that scenario. I obviously worded it incorrectly.