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THe sky raider and ridge runner use the under camber airfoil. SO did my Kitfox model 2. My kitfox model 4 classic had what I think was the Harry Ribblett airfoil and it was more predictable than the undercamber wing. My question is, how much trouble is it to span across the bottom of the wing ribs to change the undercamber airfoil to the RIbblett airfoil??

Have any of you fine feathered friends tried this??? IF so was it worth the trouble??? Did ti fly better???

Thanks Mark Smith

A couple of things I dont like about carbon fibre..

1) tiny slivers can get in your fingers and really cause problems.. ONLY a doc with a special magnifying glass can see the slivers and even then it is hard to get them out.

2) carbon fibre can be strong but it really needs to be engineered. I have read about  a few failurs of extra 300 wing spars made of carbon fibre and when the fail it is like bank and the wing is gone...

3) if you ever catch carbon fibre on fire, run.. .The particle floating in the air you will breath in have ever lasting respiratory problems...

The airline industry uses carbon fibre wet layups on the Boeing jets and lots of other aircraft, heavily engineered... I made some 1/8"plywood laminated with carbon fibre, floor boards for a super cub and they were super light. THose same floor boards are still going 14, 000 hrs later.... I also made a few tail skis out of carbon fibre, light weight and tough. Problem is carbon fibre is expensive.... so yeah its great stuff if you can make the part at minimum weight... Burt RUtan was an expert at this using fibreglass layups on the varieze....

ALuminum ribs, once you have the press molds made, and it takes a lot of work to make them, but once they are made and you can get hyour hands on pur soft aluminum, you can press out ribs fast as pressing coke bottle caps.... bet getting pure soft aluminum is not easy.. ALcoa will sell you a 5000# roll and companies like Univair can buy that much but you try  to get it..... I tried all kinds of aluminum 3003-1/4 hard was the best I could do. Univair Gave me a couple of square feet years ago because I used to buy lots of parts from them. I was trying to make aluminum blisters for a taylorcraft. IT took about 10 days to make the maple pressing  part which was pressed down into the aluminum which was bolted between two 1/2" steel plates with a template cutout of a blister. The aluminum had to be greased and the steel plates bolted together but not too tight and then a 20 ton press forced the maple form down into the plates which held the aluminum. You need to use .040 or thicker because it stretchs and work hardens also...you can tell when the aluminum has work hardened because the pressesure got way up while forming it.. stop, removed teh part, anneal it and then put it all back together and press on!! IT worked well. The guy who helped me demanded I give him the molds later on so I did an dnot sure what he did with them...but I learned how to do it

Nice photo Fred! Looks just like some places in Alaska... most of the best ski flying for fun in Alaska is in the springtime about a month long. Lots of sun, relatively warm but risk of overflow on lakes and rivers, shelf ice to rip gear off and other risk but all in all fun and when most get out and do it..

Thats the big problem right now, to make and sell a kit cost the MFG. more than flying or complete aircraft are available on the market right now...and Im sure the kit manufacturers are pretty bitter and upset, having put years into the building and marketing and selling of the kits...still they should realize they can make money just selling parts to a lot of us who dont want to spend months making a jig and welding up parts we might need after an incident.

Atlle Dodge in Anchorage Alaska made a good living buy making bolt on parts for super cubs.. He used to do rebuilds years ago but told me he could make more money selling mods, especially bolt on mods....ones that are easy for the owner to put on the plane...

http://www.challengers101.com/Bulletproofing503.html

HEAT! gotta get rid of the heat... thats the whole idea behind ceramic coatings.... aluminum and steel "wick" heat . IN the case of steel at about 1600(F) it really starts wicking heat and glows bright red... Ceramic allows surface temps to go higher without soaking into the part so the engine runs cooler... Im not good at explaining this stuff . The article above it pretty good..

Federal Ski Mfg in Minneapolis used to put white plastic on A-2500 and A-2000 wheel replacement skis back in the 50s  but being cheap Alaskans after it wore out most didnt replace it nor did they realize just what it did until a few years went by... also plastic allows you to slide over rocks and mud. A lot of airboat guy use it in Alaska as well.. .one guy got drunk and drove his airboat down airport way almost to Pikes landing and he would have except the plastic ground off and the aluminum boat bottom slowed him to a halt and the cops got him.. It was a bet with large amounts of Alcohol involved...!!Plastic works!!

UHMW   1/8" or whatever thickness is on there... it will last a long time as wheel penetration skis...

UHMW is what all the dog runners are usings.. .there are all kinds of plastic, white, blue, black, IN Fairbanks the State of ALaska lines thier dump trucks with 3/4" bluw plastic to help reduce snow from sticking in the box when clearing snow... but the most common on airplanes is 1/8" UHMW white... some guys tried 1/4" and maybe down around Anchorage where you are running over rocks all the time but it adds a lot of weight so in the interior most use 1/8".

If you were to ever get in water or overflow and dont have plastic you come to a screeching halt...and then the work begins.... with plastic bottoms you just slid right thru it..

Vance, put the white LDR plastic back on the skis. It last a long time. By the time its all chewed up , several years will have gone by.. The plastic will not stick to the snow.. I know aluminum will. I was stuck many many times with bare metal skis in the early 70s and we tried everything including black electrical tape.

Many times I had to tromp out ruts with my snow shoes in order to be able to take off again...

I havent seen any body up there in Alaska use anything else on ski bottom but the UHMW plastic. (ultra high mocular weight). Even the dog sled runners on the Iditarod sled racers use UHMW plastic...its the stuff to use...

I agree with your evaluation of the market... there are "X" number of these built and flying and no new ones being built (of the old Avid KF model4 or early type) and every year more of them get destroyed by weather or accidents. I sold my KF4 with a factory new 582, grove gear spare NEW Aerolux prop for 20K and had people fighting to get it,...I knew I screwed when the first guy called and bought it sight unseen, then 1/2 hr later someone else called I said sold already and he offer me $5000 more to sell to him and he would come that day to get it....!! My old man said I was a FU, guess he was right!!

there was a guy in Fairbanks years ago, he was a true outlaw mechanic who commonly said "F' the FAA... He used a ford falcon(1960 vintage front shock I think and put it in a bucket of ice and welded on the ears off a broken hydro sorb. off a super cub. The whole idea is to control the rebound of the gear. Big heavy tires and brakes and extra heavy bungees the gear would slam back and bottom out and after a few years the fluid leaks out and then what happens is the "V" cabane gets bulges in it from compression failure and eventually breaks... The guys who used the adjustable shocks like on the late model snow machines are on to something but pretty expensive I guess...

no longer need 

I had a kitfox 2 with kitfox bush gear. It was nice and wide but had the springs... Ill try  to post a video of what happens if you make a hard landing.. Now keep in mind, I had 600x6 tires installed so they dont offer much shock absorption. If yhou watch the video after It stalls a few feet off the ground, and fall you can see the left gear leg forward tube is bent. This turned the left wheel and axle inward and I lost control of the plane and into the ditch. I was able to fix it in about a week. It twisted the tail and ripped off the left wing tip.. I was pissed at myself more than anything and I add a lot of things go wrong all at once but more on that later.. I dont like the spring because once it bottoms out, metal will bend.  C-5 found this out as well and he had big tires. The advantage of the bungee is you can change the number of wraps to control the stiffness and bungess cord is relatively easy to get. so Ill try to post the video now hope it works.. Mark Smith 

https://youtu.be/62TGrm9_Qtg

The GPS info is superimposed and you will see it quit flying about 50mph because I had a 20 mph tail wind. Also the airspeed if a piece of junk someone installed and while I had one on order it had not shown up. The airspeed in the the KF during this crash you could not see the numbers are the low end...

Leni use bungees. I know you are a die hard and can fly springs but think of all the mortals like me out there who make hard landings and they will bend the gear and then the name calling and finger pointing start..... remember the basic rule, when a pilot screws up the truth aint in him!

I ran the 2 air tubes down the rear wing spar tube into the wing tip area...

I mounted the  probe to a flat  6"x2", .020 aluminum piece that I simplypunched hole in the bottom of the wing fabric and then used silicon to hold it to the fabric and side of the wing rib...the directions say to set the angle at about 50 degrees I think and that was pretty close.  Go up to safe altitude and slow fly towards a stall and as you get close note where the needle is.. you want the needle right at the bottom of the red arc when it stalls..... then if you approach at the top of the red arc, you will be about 3 or 4 mph above stall speed... OK in dead calm wind if you want to approach this slow, most approach faster...

THe tach is dead nuts on. I used a tiny tach and optical tach with a reflector on face of prop blade and the tach is on the money..

The fuel flow is another issue.. I ordered the gold gravity transducer, WRONG, I got it dialed in and it reads proper now but quits reading below 3gph so I spent $259 and ordered the red transducer with a smaller metering hole and it reads right one with 100% K factor but I told Kevin to double check it that it might need tweaking a tiny bit...

THe angle of attack indicator, I cold see where that could come in real handy for landing short... IF you putt the needle in the red about 2 lines from the the far left, it is a speed about 3mph above stall speed..... and it remains consistent, only thing is you are VERY slow and you can feel yourself letting the plane deep in the danger zone but I tried it a couple of times and that little silver KF could easily be a contender in a short field landing contest.....its just I have this string that runs from my wallet and is securely attached to my BALLS!!!!! so I fly buy the old mantra "Vref + 10 for mom and the kids"

MY mom had the same eye problem, macular in both eye,worse in the left exactly like me, pus cataracts.. .so I  agreed to have the catarcats fixed, that will take a few months total but not much can be done for macular. I have been flhying using my right eye only for a few months now because my left eye sees double and is consantly blurry like eye drops are permently in it....never clears up.....

It is upsetting to me, Ive flown 50 years, I accidently taught my selt to fly  in a t-craft when I got to taxing too fast and it got airborne but thats anothe story,... I can say I tried to drive it on the ground only to bounce off, finally I remember reading "how to fly a j-3" andit showed the position of the control stick during takeoff and landing so I tried to just level off and made anice landing immediately followed by wild gorund loop! it didnt hurt theplane, scared the hell out of me but I couldnt wait to learn to fly.

I got up the toher day and just realized I had to face reality, my left eye is shot, maybe they can make it alittle betterr but odds are  not in my favor and while I can fly with just my right eye its not easy and notmuch fun. I say to myself, "self, the jigs up" so without giving it too much thought I listed the KF4 on barnstormers  and within a hour had over 20 calls from all over the country.... I listed it for 20K thinking thats fair.. I had 28K in it so thats what I like to do, buy high , sell low, pay no income tax!!!! I bet my add was the shortest listing on barnstormers ever... first called bought it within a few minutes of posting it.......

I soon was told by others that the model 4 is the one everyone wants, it has all the improvement over the early KF and that is true, it flys so nice...It still hurts to think its gone, however, Kevin promised me we will all see it in future Trent videos!!!!!! so that would be wonderful

I listed my 2000 Kitfox Model IV on Barnstormers with a 160 total airframe time, 6 hrs on factory new 582, Garmin G-5, Aera 660, grove spring gear, matco wheel and brakes, 8" tailwheel    $20,000

Within in 30 minutes of placing the add I had over 20 calls..... several wanted it sight unseen... Trents brother was the first to call...

What the heck is going on??I was on barnstormers for a few minutes and the plane sold so I put "sale pending" but with so many who were willing to buy sight unseen??is there a shortage of model 4s out there  or did I sell too cheap????I just picked a price, I have over 25K in it. The money is less important than making sure it ends up with someone who is on fire to fly.......hopefully he will stay out of trouble with the help of his brother til he gets some time in the plane then I suspect he will introduce dozens of people to flying and Trent will make the videos and we will all get to see it!! Thats what I hope for......like a super "young eagles program" 

THe Garmin G-5 has an RS-232 input, only one wire from the Aera 660 to the G-5. SO if I have an active waypoint I am going to , the G-5 and change to HSI page and the pointer appears showing the direction of the way point. STill shows compass heading and ground track as well. Its the hot set up...

Add 2 servos and an autopilot controler and you have an autopilot, just sit back adn relax and watch the scenery go buy..

The LRI is a fantastic instrument, simple and it works. It uses air pressure  but it is fool proof.. I got the last one the guy made. I beggedhim so he made me on, I could make it myself but his quality  is so much better...... Fred in France made it own and it works fine....by placing it on top the dack I can see it while landing and after parctcing up at altitude, you can watch the needle get in the red on landing and know you are 1, 2 or 5 mph about stalling angle and weight makes no difference, nor density altitude.... it is a great instrument.....

My vision problems came on suddenly like within 3 weeks so more test but I am pretty sure Im screwed. both parents had MD and I have the highest uncontrolled BP of the family so the jigs up... I havent given up, just I realize I might as well stick a fork in myselft because Im done!!!!

I sold my kitfox N503TJ to Trents brother, "sale pending" but Im sure he will buy it.. I tossed in my spare Aerolux prop and 2 engine mounts and all the spares I have...

WHy? Im only 66 but have been fighting high BP for years and the docs in ALaska said OH dont worry bout it, thats normal for your age......(BS!)

IT typically run 180/100 for years.... once I moved to Washington and got a new doc( A German doc) he flipped out at the high BP and said I could have a stroke or heart attack any moment....that set me back on my heels.. we tried different meds and got the systolic down to around 140 but the Distolic will not come down... he oreded  ultrasound and my heart muscle wall has thickened up and become stiff so it probably never will go below 90 luntil I go toes up even on meds....

But I digress, so I have high BP , big deal, well it is.. now my eyes are going.. macular brought on by high bp, cataracts that I can get replaced but macular they cant do anything about....mine is medium fast progression so I decided to quit flying... I have a hard time driving at night, see 6 head lights so aim for the middle!!

ANyway Trent Palmer does lots of videos and is the best advertising agent for kitfox there is.....so maybe we will ole 503TJ  in future videos......

Me, next year Im trying to New ZEaland for a few months, the Bali for a few months then come back here and sell out....

Mark

I wrapped the muffler can and hot air outlet hose nd the inlet stack with HD tin foil and used safety wire to secure it.... I will probably remove the tin foil this summer when it warms up....but every little bit make a difference...

Thank Lenni.... I still have trouble with video stuff... Yup thats it.... The heater works great... IF I did anything to improve, Id take the fibreglass stove door seal material and make a spiral around the muffler can and force the air to swirl around muffler to get a little more heat.. .On climbe the heater air was hot, on cruise, it cools some but lots of airpressure in that cowl so that was part of it.. all in all it made it warmer in the cockpit... even though a lot of the air is blasting under the seat on my side,,,,so I need to seal up the area under the seat a little bit.....THe AOA is a neat little gadget, not sure how much or if Ill use it as I have a very accurate AS indicator and this plane that TOm built is very predictable and a true joy to fly.....IT does perform better with my 72" Aerolux prop, shorter takeoff, faster climb and faster cruise and WAY WAY smoother prop.. most 2 blades are rough running but not the Aerolux

try this

https://youtu.be/kHAHEVKJEds

I installed hot air muffler cabin heat, works great, LRI (AOA) on top dash, Garmin G-5 tied to my Garmin Aera 660 for navigation, electric carb heaters (for carb anti ice), electric fuel pump, and LED mav lights. PUt my old Warp drive 3 blade 68" prop back on, my 2 blade is faster in cruise, and almost identical in climb..about 1000 fpm at 60mph

kHAHeVKJEds[1]

Ideally you want the tail spring to take the shock loads. That is why I never was a big proponent of installing stiffer tail springs on Super Cubs. Those that did ended up putting more stress on the tubes in the tail area and eventually something would bend or crack.....

IN the case of the Avid, maybe someone dropped the tail in the past or got it to crow hopping on the runway or ran the tail thru a ditch, who knows... the poor tail wheel takes a beating... solid rubber tailwheels add more stress, pneumatic tail wheel tires take up some shock.....

I wouldnt be worried about it Vance, it is just a light weight structure but is you beef it up just a little, it will put the stresses back on the tail spring which is what you want...

About the only tubing primer I ever saw that could stand up to MEK based fabric coating systems was stits epoxy tubing primer, (green). There might be others out there but I know Stits works, spendy but works...

Weld in two tube ,about 3/8" or 7/16" OD from the center of the bend in the vertical fin post to the center of the lower longeron bays. THis will stiffen it a little bit. Ive seen the same thing super cubs in Alaska and that is how we fixed it....YOu dont need large tubes, just small one to add a little strength in the middle of  the long spans...

If you tig weld, have a spotter  with fire extinguisher in case you catch the adjacent fabric on fire.... Gas welding is easier for me but what ever you are comfortable with.

GLue on a patch with poly tak, let it dry, shrink it , apply the primer coat(poly brush) and the silver (poly spray ) and top coat and your done! OR what ever coating system you use. If the old fabric has enamel, try to clean it off with MEK so you can get a good glue bond with the poly tak...

YOur absolutely correct......if it looks iffy at all, replace it. That way when you are up in the air you wont be as concerned about it.....

Its not the lift strut rod end I am concerned about. It is the welded in stud that the FEMALE rod end attachs to. This is on some of the early model 4 kitfoxes. I see the factory change and started using a MALE rod end that threads into the end of the lift strut. The earlier style is the one that worries me. It has CUT threads placed under tension....not good.

THis silver strut has a stud welded into the strut end and a FEMALE rod end threads onto it....The threads are CUT threads...The aviation industry learned all about cut threads on Piper lift strut forks when Univair made replace forks with cut threads. Even the rolled piper threads failed after so many cycles and hours so finally Piper came out with a lift strut that had a really large diamer HD strut fork that does not have a life.....

The WHite lift strut in the photo below is a later model Kitfox strut. Note the end of the strut is drilled and threaded to accept a MALE rod end....

This is better but I think I will design some kind of secondary load path for th strut attach point.... Probably a flat strap that picks up on the lift strut wing fitting and then is riveted to the lift strut tube with 4 or 5 steel high shear cherry max rivets. 

WHen new and tested even the cut threads will hold a lot, but they are WAY more suspetable to fatique crack(the cut thread already has a built in stress riser), add to that flight cycles, people pushing on the struts and you are asking for trouble....

The way Avid and early kit fox struts were built is the way to to go. Put the attach bolt in shear. The CAA accident aircraft C-FOLD  (theres a good N number!!!) shows a threaded strut end fitting that failed and they think it failed on take off. WHo know the history.. was it in a previous accident? How old is it? Was it rusted? Anyway according to he accident report the aircraft lifted off and a loud crack was heard followed by an uncommanded roll to the left...... it was the left rear lift strut attack threaded part that failed.... The plane crashed and was BER...

dft_avsafety_pdf_023415.pdf