On the sky raider and ridge runner they use 48" with a loop at each end of 3/8" diam3ter bungee cord but only aircraft grade. THe shock strut gets 3 wraps on each side for a total of 6 wraps and that hold up a 950# plane...YOu could make an extra 2ft cord and if you needed more, just add another 2 wraps....
Here was the plane before I bought it. The seller kept the grove gear and put kitfox bush gear with coil springs (hatz type gear) He used a technique where he got rolling on takeoff and popped the flaps down to get in the air.. .It was pretty quik with a 582 no matter how you did it when empty.
I have had the best luck landing with power, on gravel, 3 point. I supposed a guy better know what it will behave like power off like during an engine failure... light airframe = low inertia= high drag=higher drag as the AOA increase and that last 10 or 20 mph bleed of in an accelerating fashion very quik.
https://youtu.be/62TGrm9_Qtg Ok before I get flamed by a bunch of you, watch this vid. When I smak the ground for a brief second you can see the lower left gear leg and it is bent. There were lots of things I did wrong in this landing but I had 1)kitfox bush gear with the coil spring. They only have about 2-2-1/2" compression before it bottoms out and then you have metal to metal...2) the second strike was I had 6:00x6 tires which took up little shock. As long as I made smooth landing not problem... One botched landing where I stalled 4 or 5 feet off the ground and it smaked hard. Most planes will settle with the wings still carrying some lift but I suspect this airfoil dont do that. I punched the throttle but it hit hard, the coil springs bottomed the left gear front tube bent and when it did, it toed the tire inward about 30 degrees so the plane immediately exited the runway to the right and hit a ditch.It was vilent enough my head smaked the door and my gopro flew off into the grass. I tried to taxi out but could only go in circle because the tail was bent as well... Anyway I fixed the plane in a week. , cut weld, fabric, spray etc. and sold it for 8K. Its is listed in Seattle wor 24K now. It has a 503 engine with only 12 hours since factory new and a C box with clutch all new... but 24k too much me thinks... Anyway I should have gone around and set up a stablized approach. Also the idle was stuck at 3000 rpm because the throttle cable housing ferrule slipped and made the throttle not close down.. I fixed all that after this flight but as made at the plane and myself so just sold it...Not the planes fault, its just a cold machine that will kill you if you get to complacent, that would be me!! Joey had the same gear and bent his so I was aware of the possibility and was working on making bungee shock struts like a super cub.
The Easy Raider with the bent wings and ripped off gear was a good flying plane. The owner removed the big 670 engine and installed a 582 and ground run the engine and was test flying it when the engine quit. He could not make the runway. If you look at the photos and blow it up you will se he hit a steel fence while gliding back towards the runway at a 45 intercept angle. He sold the eninge and mount so the mount might be a big deal for me, not sure I can get all the angles and stuff sorted to weld up a mount but I have a Ridge Runner coming and I think the mount might be the same...if so Ill try to find someone to weld me up a mount... I have a Lake LA4 that I flew for 28 yrs. The flaps only went up or down and down was 20 degrees.. max lift only , dont need more drag. It was underpowered anyway. WHen flaps down, the nose got real heavy and you have to hold the elevator trim towards nose up to trim off the stick pressure. The flaps are 80% of the wing span so I guess the CP of moves aft flaps down thus making the nose heavy... SO on the avids and Kitfox with undercamber wing it makes sense that flaps down the nose get heavy and I had no elevator trim so had to hold back pressure.. The Ridge RUnner, Sky Raider dont use flaperons, they use flaps and seperate ailerons and I cant remember a big pitch trim change flaps down vs flaps up, maybe a little change but nothing like the full span flaperons... So when the undercamber wing hits that wall trying to go faster then 85 I understand now. My RR1 could do 95 full power but I was always at aft CG so that might have taken some of the trim load off the tail., Ill probably just put it together and fly it like it is... Im nervouse messing around with airfoils too much because as a layman I know jsut enough to be dangerous... Thanks for modeling the airfoil and explaining it... that is worth a lot.
Turbo, I think you live just down the road from me.. Im in Davenport, over west of SPokane about 40 miles.... ANyway I bought this Easy Raider off Barnstormers....and I am pretty sure it is a copy of the sky raider so it has the undercamber airfoil...Since I have to repair the right wing, I was thinking of make it a straight line from leading edge to trailing edge on bottom of airfoil. Dont really care about the stol stuff especially if I could get 10mph more speed on same power and that is what I saw with teh comparison of flying the KF2 with under camber and the KF4 with the harry ribblet wing.,.both had same engine and prop,the KF4 was EW heavier at 860EW THe KF2 was 500EW and it really showed with a ROtax 582 65hp engine and 68" 3 blade warp drive.. The sky raider/easy raider I just want to fly single place . I have to make a jig and weld up the main gear as it is trashed unless I can get Stace Schrader to sell me a set for a Ridge RUnner... I also bought back my old Ridge RUnner 3 in MOntana and it should be here in a few weeks...It has a 503 and is stock. Well Id ditch the big tires and put 800x6 tires back on it.. dont like those big atv tires....too stiff, I had this RR3 all ready to fly then sold it to buy a RR1 which i flew a little bit.
The Avid on Floats is John Knapp in Bath, NC. I think he said it had a Rotax 670 or some such size.. YOu can ask him, he is on here occasionally. He still rides hot motorcycles at 85yrs old!!! He likes big engines...... I flew both the KF2 with the undercamber and 582 rotax, short take off 1000 fpm climb at 60, however it hits a wall at cruise and 85 is about as good as it gets... I also has a Kitfox 4 with a 582 and it took off about the same and climb about the same, stall speed maybe 3 or 4 mph faster than the undercamber wing, however the biggest thing I noticed was it plowed right thru 85 on up to 95 mph cruise with the same engine and prop as the KF2. It slid right thru the "wall of air" that the under camber wing hits about 85. I think all things considered, the KF 4 riblett airfoil is a better all around airfoil. THe under camber airfoil when you get slow, the airspeed bleeds off rapidly so I suspect the drag is getting real high at slow speeds and high AOA. IF you are not knowledge able of this , you can get too slow on landing and "arrive" with a thud when the wing just quits with no warning.. some kitfox pilots say to land with power. I have read of a few who land power off. It goes to reason that is you use the riblett airfoil you can reduce power, and get more range than the undercamber wing airfoil... me thinks anyway...!!
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
I used to live at Bradley Sky ranch from 1976 to 2014. Got tired of the cold and dark winters and Bradleys have the airport in shambles and so most took their planes out of there... I worked as A&P/IA since 1969 and went to work for BLM in 1998-2000 then FAA 2001 to 2014 and retired and left.. Not much retirement but enough to live here in Washington for now....
I bought that wrecked Easy Raider off barnstormers... should have my head examined.. I had a ridger runner 1 and 3 and sold them both , too squirrely on the ground. ANyway the wreck the gear is wiped off and so was thinking maybe I can modify kitfox or avid gear to fix. The Ridge Runner/Sky Raider use a J-3 type gear set up with Vee cabane and bungee shock struts.... The main thing is if the 1) attach fittings would come close to fitting the SkyRaider and 2) if the they do pin on ok would the axles be in reasonable alignment....Im trying to get the dimensions of between the gear fittings....the rest I can make work with a torch(also known as a gas hatchet!)
I might be interested.. I need to measure between my gear fitting on my sky raider to see if they will fit. Id have to hack them up a bit but thats ok the price is more than fair....if nothing else they would serve to roll the plane around while I figure out how to make new gear legs....
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