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Ski rigging techniques

Camber angle

wheel camber.jpg

For skis, I currently have my camber set to zero, with the airplane sitting on the ground, at the weight that I most often land. Does anyone set negative camber ? If you are snow skiing and you ever allow your downhill edge to tilt down ( positive camber ) you usually face plant immediately.

The weak link for Supercub gear is a load inward, not aft. Of coarse you try not to, but I have had to turn with the outside ski lower than the inside ski. The landing gear is receiving a huge load inward because the outside edge is digging in. Some negative camber might help this. Having the inside ski dig in slightly, ( because of the negative camber ) might help pull you around ?????

Thoughts, comments and ideas welcome !

Jonny O
 

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Hey Jon, what skis are you using? They are usually slightly positive until the fat pilot gets in with all his gear and fuel! You should be sitting flat on the skegs loaded.
 
Keep an eye on your rear ski thimbles. If you notice stretching or flattening of the shape and often taxi over big drifts add some length as more nose up/longer rear cable may be desired.

GAP


I noticed that on my Datum setup,deformed thimbles indicating a major pull on the 1/8" cable. I kept a close eye on the bolts and and the bushings the bolts go thru, and didn't see any further cause for alarm, so kinda blew it off/didn't do anything. I do a lot of uneven terrain, especially going up my ramp to the hangar, every flight. The issue is, if I lengthen the rear cables, the inflight AOA will increase beyond what I want, and I'm already a bit more nose high then otherwise needed. I guess my "solution" is to continue to just keep an eye on things, it's been like that for the last 6 seasons, with no further thimble deformation. They are deformed a bit but not flattened. My old hang gliding experiences taught me that when a thimble deforms, you have reached the working load of the cable, and then some. If we saw that, we threw the cable away and re rigged it. I suppose I could re rig back there, the same lengths, and see if it happens again, and if so, after what taxiing conditions. Maybe do that, but use the next size cable up....my bushing attach bolt is AN-4.

Spinner2: Your rigging process sounds pretty straightforward, compared to figured out how/where to rig on retracts, having to take into account the fore and aft movement they have. Straight skis, must be nice! Yours look great.
 
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Hey Jon, what skis are you using? They are usually slightly positive until the fat pilot gets in with all his gear and fuel! You should be sitting flat on the skegs loaded.

All the federals I've flown are negative camber.

Glenn
 
I didnt take time to load and watch the vid.

Some ski installations have a strong spring on the rear cables for any extreme “ski-noseup” events. The aft spring needs to be stronger than the front bungee, obviously. A short loop of bungee has less give than a longer loop, so a shorter loop of the same diameter and durometer as the front bumgee works great.
 
All the federals I've flown are negative camber.

Glenn

Hey Jon, what skis are you using? They are usually slightly positive until the fat pilot gets in with all his gear and fuel! You should be sitting flat on the skegs loaded.


The skis are Atlee Dodge composites. Yes, they are slightly ( 1.5 degrees ) positive camber empty and about 3 degrees negative with full fuel, winter gear, 155 lb pilot, tent, woodstove and etc. I pumped up my Acme Gen 3 shocks to be stiffer for Winter ski flying, in the Interior, with our very deep sugar snow and very little crust. Thanks guys.

Jonny O
 
As somewhat of an aside.......I REALLY don’t like the forward limit cables on skis rigged to the gear bolts. I MUCH prefer they be rigged to lower engine mount bolts. Much better and safer geometry.

And, yes, I realize some installation instructions call for mounting to gear bolt.

MTV
 
Not really knowing what I was doing when I rigged my Datums, my old carpenter sense told me the same, the angle going back to the gear leg forward bolt was "wrong," not at all optimum. Even after I saw many others get away with using that location. My attach point is on the side of the fixed section of the boot cowl, an AN-5 bolt that goes thru a gusset at a firewall tube cluster, a bushing standoff keeps the cable and bungee ends clear of the boot cowl. I still check that gusset every annual closely for any signs of excess pull on it, and signs of deformation, same with the AN-5 bolt used, (as it is subject to bending loads, though the solid bushing stiffens it) all good so far. It gives me a vertical angle. IF I had known I was going to get into ski flying when I built the plane, I would have used a bit heavier sheet 4130 for that gusset, but as any pull on it is straight down, it seems to be adequately strong as is. I didn't think about the motor mount option until later, and then saw that it would have presented, with my application anyway, other issues. A rubber grommet in the boot cowl makes it all look OK, and when I take the skis and rigging off, Ace Hardware provided a tapered rubber plug that closes out the grommet hole perfectly flush, I thought that was a pretty nice touch!
 
I did a test on my new bungees from Datum, pull testing along with the old ones showed the 10 year old original ones (and I thought it had been 7 or 8 years, until I searched my records) were maybe 5 to 10 % weaker/easier to pull. With what seemed equal pull force, I could get the old one about gut high, the new one about waist high, with the end hooked in a floor grate and me standing on the grate. I was going to get fancy and pull them a measured distance, and use my fish scale to determine the difference, but didn't bother. This reaffirms my faith in the things, and other then the old ones being dirtier, I couldn't tell them apart, no apparent UV degradation, I guess it pays to hangar. Otherwise, the skis themselves seem to be good for the long haul, and I am still happy I bought them.
 
QUOTE=Jonnyo;760760]View attachment 45957

For skis, I currently have my camber set to zero, with the airplane sitting on the ground, at the weight that I most often land. Does anyone set negative camber ? If you are snow skiing and you ever allow your downhill edge to tilt down ( positive camber ) you usually face plant immediately.

The weak link for Supercub gear is a load inward, not aft. Of coarse you try not to, but I have had to turn with the outside ski lower than the inside ski. The landing gear is receiving a huge load inward because the outside edge is digging in. Some negative camber might help this. Having the inside ski dig in slightly, ( because of the negative camber ) might help pull you around ?????

Thoughts, comments and ideas welcome !

Jonny O[/QUOTE]

Well I know this is a couple of years old but I can give you a first hand account of what happens when you have positive camber on your skis. I bought a Pacer several years ago from a guy and it came with a pair of Landis 2500s that he'd been flying on it. I came in to Lake Hood one March day with a 17kt gusting to 23 left crosswind on a sunny Sunday afternoon on my way back from my cabin at Lake Louise and landed on a rutty icy lake. I held left wing low and kept the nose straight and as soon as i touched down I snowplowed off to the right and my ski folded under the cabane vee and I slid to a stop with no damage except the gear leg and some cracks in the left ski. I took the ski to Landis and they repaired it, and as me and the kid were sliding it back into my pick up the kid says, "It seems weird that this right ski is rigged for the left side." And me being the smart guy that I am I replied, "That's the left ski. See the L marked there with a magic marker?" And he said, "The serial number on our skis are all even for the left and odd for the right. This is a right ski. See how the axle hole is cambered? That's to keep you from digging and edge in on the ice." Sometimes you learn the hard way...
 
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