zadwit

There is a formula that aircraft designers use for TW aircraft. The determine the aft CG loaded for flight, level  the aircraft and draw a line vertical thru the CG. Then they measure 12 degrees from the CG forward and that line shoujld  not go thru the axles center line. If it does, it make the airplane very tail heavy and hard or nearly impossible to control. Ironically I read this in Design for flying by Dave Thurston, aeronautical engineer and a few days before I read it I was talkeing to Dean Wilson about trouble with ground handling on my Ridge Runner 1. Guess what, the Axle center line is 20 degrees maybe a little more ahead of the Datum, with plane loaded aft CG ready to fly on the Ridge Runner which is why it is such a squirrel on the ground. The Main gear axles are 8.75" fwd of the WLE on the Ridge Runner 1. When loaded to most fwd CG the angle from CG to axle is 10 degrees but it will never be there bevause the fat pilot is 22" aft!!!! so most of the time the wing CG is at the aft limit of 16 inches.........
The tail is slow to come up even with a 503, a bigger engine than designed.. and it wanders all over the runway. Does not want to go straight. The closer the axle centerline is to the loading flying CG, the more stable ground handling, easier to nose over, but tail  comes up quik.  Partly at Play on the PA-180150 is the engine is canted down on the mount, the engine is powerful and so the thrust line is above the axles quite a ways which all adds to lifting the tail quickly.  COnverted Tri pacer to tailwheel were terrible  on skis because you could not get the tail up out of the snow so takeoff runs for very long. The PA20 was not as bad because it had more down elevator travbel,, a lot more down travel.
 
Same problem  on the TexasTail Dragger Cessna 150, the gear so far fwd impossible to pickup the tail on takeoff so in the snow a real problem....
I have not measured the angle on a PA 18 but I looked this info up. Datum is Wing Leading Edge (WLE)
Axles centerline is 2" aft of the datum. Level the plane  and the axle will be 2" aft of the WLE, the CG  is still farther aft,
CG range is 10.5" to 20" aft of the WLE on PA-180150
YOu would need a scale dwg of a pa-18, mark the CG location fwd and aft, then draw a line 12 degrees thru the CG at the wing down towards the axles and see what it measures..
 
 

 

Generally straight skis are best for performance esp in deep snow plus you are removing the weight of the wheels when you install straight skis.
Out where i live there is 3 months of deep wind drifted snow, the airport is plowed mostly but no place for straight skis plus having wheels under it allows me to fold the wings and take it  home... A hangar would be ideal but the city here wants $250 a month to store in this hangar with  4 other planes and there are quesitons about working on the plane in the hangar.....so thats not such a good deal, the only other option is lease the ground and build a hangar but not sure I want to do that.. .I might get a wild hair and drag up and move someplace nicer to fly, less wind, the damn wind here reminds me of the north slope of AK in the winter......Davenport, Washington  30 sm west of Spokane in the wheatfield country...
no cover.....mark

I watched a Youtube Video of a guy landing a red kitfox and it swereved just a little one way then made a big sweeping groundloop with screeching tires and all but it didnt hurt it...the first thing the pilot did was look around to see  if anyone saw it!!! I laughed so hard my side hurt......
WHen you screw up the first run of order is:
1) did anyone see it?
2) can I blame it on someone else?
3) can I shit-can
4 problem solved!!!

I would like to get a set of wheel penetration skis to put under my classic IV main in case the engine quits or I am forced to land in a farmers field with 2 feet of snow.... 
I just fly around  for fun by my self, not into any off airport stuff anymore, it always cost way too much $$$$$$$$$$$$$$$$$$$
 
As a side note, the exwife has not seen my new plane and if I play my cards right and keep her entertained she feel sorry for pathetic me and make a small contribution to the

"Markie FUnd"!!!!!!!!!keeping my fingers crossed....
 

In Kotzebue the sea ice would  get so  rough one eskimo had a super cub with wood and galvanized bottoms skis that had a nitrogenshock strut built onto it off of a SIngle engine  otter. He said he cojuld land on the roughes ice and itwas like landing on powder...

On the Avid the skis are bolted to a drilled and tapped axles hole.
 
On the Skyraider, the axle is driller thru and a 5/16" rod pins the skis on 

These are photos of skis installs I have or found on the internet...This Avid  has a 503 Model IV "Bandit"This is a Skyraider 1 and the skis are smaller....than the Avid  or Kitfox one...
I wonder if anyone has the original jigs for the skis?????????for Avids or Kits????

Ive found cracked axles on PA-18s  inAlaska and cracked gear attach fittings where they tightened the bolts to o much and bent the fitting and cracked it. One was broke clean off the fuselage and only the back 1/2of the fitting was holding on. It was on a guides plane at Prudhoe Bay Airport during hunting season and hethrew a fit when I tagged this plane. He screamed and yelled at me and said how am I supposed to that fixed up here??????  His mechanic in Fairbanks called me up and said how  can we take care of this.. I said find a welder in Prudhoe who can weld it back on, and send you a photo and if you say its ok, write it in his airframe log and I will sign off on the tag as good to go so that is what we did. It worked fine...other inspectors sneered at me but I would just say we are not supposed to be cops we are safety advocates that is all nothing more nothing less...It was  a nice tricked out cub... with all the mods.... Would  have been a shame to have thegear fail with some of those horrible loads thoses buys put in themmmm, they overload  the hell out of theml andthen  tie horns and hind quarters on the lift stuts after they stuff the inside full....

I sure you could clean the failed area and reweld the gear leg, then apply a flat 4130 patch 1"-to 1-1/2" wide, .062" thick over the welded area from one side, around the bottom, up the other side. gas or TIG Weld it and when finished, stress relieve the weld. 
 
Then check the axles for alignment.
put the wheels on, measure from one tire center other tire center. Write that number down, say 60", divide by 2=30"
Now go to  the back of the plane and measure out from center of stablizer under the fin 30", mark a spot with a marker. 
Now  take a flourscent mason string and wrap around  the tail and tap it so it lies on that mark at the 30" point.
Pull the line fwd. and just hold it above the center of the tire , where you made that first measurement, and just look down. IF that wheel is toed in or out you will see it right now...
Simple and it works..  A little toe out say  1 degree OK but no more and NO toe in.....Parallel is  best....
 
I went to the oral surgeon today and my face hurts and Im on pain meds so I hope this all makes sense. YOu can call me if you have questions of email  me even if you think I am full of it......I called Murele Williams in Phoenix and he didnt hesitate and said buy Grove gear and install when I asked about a wider maybe a little taller but mainly more stable main landing gear....Mark Smith   907-378-9632   exfaa@outlook.com
Yup I was FAA inspector for a while.. I felt like a whore going to church every time I went thru the door to work and after 10 yrs my BP was so high even in meds I knew I would die behind the computer so I quit as  soon as I could . The FAA  Division managers tell me the FAA doesnt care about GA, that it  is dying and  they mainly want to concentrate on 121 Airlines and the big repair stations...145s and in Alaska on the 135 operators that crash a lot..... But get this....They let the 135s fly VFR at night when really those young guys are flying IFR on at real low altitudes and the FAA allows 4 or more airplanes in the surface class E airspace when the wx if below VFR minimums, and they tell them to maintain visual seperation!!!! What a joke.. They do this so the little planes can get in to drop PAX for the Alaska Jet. This is done at Kotzebue, Nome and Barrow.... and they wonder why the planes with passengerts fly into the ground once in a while!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!"
OK enough. At least they leave Exp airplanes alone pretty much....
 

legacy airplanes like Piper J series and Aeronca etc had most all the steel parts gas welded and then normalized to stress relieve and then a weld  inspector inspected  the welds.
I have always been leery of MIG welding that a lot of companies use. I know they ues it because it is fast, and quicker building = more profit
But do they stress relieve Steel 4130N ( is steel tubing that is in a normalized condition, meaning not heat treated. When finished welding it still have higher strength than 1020 mild steel so no need to head treat it. SOme parts were heat treated like the wing tubular spar on a Beech 18 series or like the main gear legs on a Helio Courier.
From the looks of the photo, it was a very poor weld that let you down. I  would encourage everyone of that vintage airplane with that type of  gear to get down there and clean away the paint and look at it real close with a 10X glass.  If you see anything that looks like a crack or rust stains in a thin line, then I would use dye penetrant and see if it is cracked.
The area is highly stressed because the axle it trying to break away vertical and aft. Also low points in a gear leg or any other part of the plane collect moisture.
I know on PA-18 series the lower fuselage carry thru tube for the lift strut  attach and rear gear leg fitting is a lot heavier wall thickness, and I figured it was for 2 reasons.
Higher stresses in that area, and they want that part to rust out LAST!!!! Just my opinion. I worked on lots of steel tube planes in Alaska since 1964 to 2014 and left, the state tired of the cold, dark.....I miss some of the flying 
Mark SMith    retired, ASMEL, SES, Instrument, A&P/IA since 1970
 

My Ridge Runner 1 has a 503 Rotax, DCDI, IVO 68 Grd. adjustable prop set for 6100 static. Empty weight is 400#.
Flying weight is 400# +230 fat pilot+60# (ten gallons gas)
Before VGS installed , stall was a sharp break at 45 flaps up and 43ish full flaps power off.  Never did try to stall it full power  with full flaps...
After VGs, (StolSpeed Vgs from AC Spruce) , stall is more of a mush around 25-26 mph, able to do steady state flight at 28-30 MPH easily.
Make approach at 50 , slow to 40 on final and over the end of the runway hold the plane off and it was touching down around 30.  I am sure it would go slower on landing but I would have to use a lot of power and the tail would  hit first.... Also the VGs definitely made the ailerons more responsive and crisp....I installed the Vgs just like the directions said....
 
I know Vgs work differently or not at all on different shaped airfoils but they sure helps this under cambered airfoil. You can still get the airplane into a high sink/mush rate but now with VGs at a much lower airspeed....definitely worth the $100 I spent... I had so much trouble with the double backed tape, I just super glued  them on..Mark

These football tanks were originally seen used on Birdman CHinook Ultralight aircraft. One on each side suspended at tje jury strut strut  site. It help reduce the load the wing has to carry because the weight is not  in the center of the fuselage..... Could be used as aux fuel tanks with quik release setup for longer trips . IF you dont need  them for local  flying ,just remove them. I think some Rans S-7 uses them.....

Yes it is from Ellensburg....

I have three enclosed trailers and have the planes well hid!!!

There is a you tube video of jato on an  Ercoupe years ago. Not sure what it about but I always thought man that would be goodto have if somebody landed in a place they could not get out of, Strap on the rocket just to get out of there......The jato were mounted under each wing, small ones, maybe 3 under each wing....

Dont feel bad, Normally I find  a woman I hate, buy her a house and then leave in my plane with only my shirt  on  my back!! I can sleep in the  plane but cant fly the house!!

My ex wife is flying down from Alaska to check up on me ina few days. She lost her parents last years and siblings and I lost my parents last year and she is afraid something will happen to me and she will be left all alone.... but Im not a daredevil anymore.... Im am very careful in my approach to driving and flying.....SHe  knows I have 2 planes and one is for sale, I didnt tell her I bought another one because she will throw a fit, so I have two of them hid in my enclosed trailers....!!!! She just doesnt understand that flying airplanes is an incurable form of madness for which there is no know cure!!!!
 
Mark

In Alaska years ago I was out on a short strip surrounded by stumps and on takeoff I missed on with the MLG but the lower flying wire got ripped off. I didnt know it until I was in the air... There is an airload normally pushing down on the tail and I know I hit something so was looking back and the tail looked fine but  if I pushed fwd just a little on the stickthe stablizer and elevator on one side would move up several inches so I didnt mess with it and went on home and landed.   If you ever loose the top flying wire on the tail, you would be in big trouble. I mention this because I see over the years some companies have eliminated the top flying wires and only have a lower tubular steel brace which is ok but prone to getting hit with rocks so it is worth keeping a close eye on it....The Sky Raiders had cables on the top and bottom,, a better deal I think.....

This is great info GUys. I belong to the Ridge Runner group and there is very little if any info out there on the ridge runner and Sky raider is out of business so I have had to learn everything the  hard way. Had enough, selling the Ridge Runner 1, its on barnstormers and looking for a Kit fox model 1,2,3 or IV.Cant afford anything bigger than that. 582 would be nice to  have.. Ill wait on the the big king kong engine for a while and see how it shakes out.... my budget is  16,000 but if I have to I can go to to 20,000 but that is prutting me in a money bind pretty bad. Id have to bring it home and park it for a while.....til I sell the Ridge Runner...
 
Thanks again for the input. Im looking at the little Kitfox 1 that Jim Chuk had and also if  I can contact him, Thomas Jones in Ellensburg has a KitfoxIV with a 503 which is what I want for now, because  I have a spare new engine(503)  then later maybe upgrade to teh 582..but then it all depends on how  much they want. Jims is a kitfox 1 but Id be ok with that. Looks lilke he has worked all the bugs out of it so that is nice... Im an A&P (was IA for 30yrs), worked for flt standards for 10 yrs and retired.
..Thanks again, Mark
https://youtu.be/wxSj3WaNsMk   Here is a short video I took  of my Ridge Runner 1 this September. It was 85, at 2500 msl