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Ski rigging techniques

spinner2

MEMBER
Montana
After recently rigging my Carbon Concepts board skis I Thought I'd share my technique and where I sourced materials.

Both my plane and the skis are not certified so I'm not bound by an STC or Field Approval. I made reference to both 43.13 and Dodge's online ski rigging tips. Both are very helpful.

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The skis were received from Randy with pedestals but no rigging or attach points on the skis.

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I purchased the toe and tail attach fittings from Stoddards along with stainless steel axle washers. The fittings that attach on the gear bolts and the bungees came from Reeve's.

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I found some stainless steel clevis' with a high load rating from industrial supplier MSC that came with a 5/16" diameter pin.

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The threaded half of the clevis is threaded 5/16-24 so I replaced the pin with and AN5 bolt and as a keeper threaded on an AN nut. The plastic donut is UHMW that I machined a 1/2" radius into and drilled 5/16" for the bolt to pass through.

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On the gear attach point I used a Ronstan brand 6mm stainless steel, high load rated chain link. A hole was drilled though the hex section to accept a cotter key.

The second cable on the right is the check cable.

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Setting the angles for ski movement was made easy using a chain hoist, comealong, and a smart level.

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The first step is to set the length of the check cables. I went with a maximum down angle, should the bungee fail, of nine degrees. 43.13 allows for considerably more than this, but less seems better as long as there is enough slack to allow full ski movement over uneven ground.

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The next step is setting the length of the rear cable. With the skis flat on the hangar floor I raised the rear of the plane with a comealong. I found that one click of the ratchet was equal to one tenth of a degree on the smart level with the placement I used.

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I went with 1.5 degrees nose up ski attitude in flight. This meant raising the tail 1.5 degrees above level and the setting the rear cable to this length.

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Lastly the the bungees are attached and the length of the crust cutter cable is determined by the amount of down force required to stretch the bungees. 43.13 has a poundage guide based on ski displacement. This step is a little subjective and not real easy to measure. But the end goal is to have enough tension on the skis through the bungees that there is no in-flight flutter of the skis.

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The rigged skis weighed 33.2 pounds each. 1/8" diameter control cable was used per 43.13 for skis and a plane this size. After finding the center of balance for the rigged skis I made a new W&B. This is easy to do when existing component weights and arms are already in an Excel file.

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A pair of Dolly's were fabricated too.

I'm sure there are other ways to accomplish the same results but this is how I rigged these skis.
 

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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
 
Also after your bungees are setting in tension for awhile ( tail down ) that your bungees won't return to where you originally had them, they stretch out a little

Glenn
 
There was a time when it got cold that bungees were replaced with Atlee Dodge springs. On the ground the bungees wouldn't react to changes in ski position quickly enough and tended to stretch in flight under wind load and flop around. That's at about -30F or colder in my experience. Maybe there's better shock cord material available now or some skis can't use springs for some reason. I like springs as they never wear out much due to sun and weathering.

GAP
 
There was a time when it got cold that bungees were replaced with Atlee Dodge springs. On the ground the bungees wouldn't react to changes in ski position quickly enough and tended to stretch in flight under wind load and flop around. That's at about -30F or colder in my experience. Maybe there's better shock cord material available now or some skis can't use springs for some reason. I like springs as they never wear out much due to sun and weathering.

GAP

No experience with skis, but I've watched regular bungee cords slack to full extension in roughly-20/-30 weather. When brought back inside to warm up, we watched them shrink back to their normal unstretched size as they got back to room temperature. If I was flying anything that depended on bungees in a really cold environment, I'd look into springs too.
 
Put some silicone tape around that wire at the top of the bungie it will start to chafe quickly due to the wind.
DENNY
 
Put some silicone tape around that wire at the top of the bungie it will start to chafe quickly due to the wind.
DENNY

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Good suggestion. I put some spiral wire wrap around both ends on both sides.
 

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We had a foot or more of snow last Sunday but then the wind blew for a few days. Got to play a little today

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Step comes in handy

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Was having fun till freezing rain

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Glenn
 

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Glenn, telling us Alaska boys you have been ski flying is enough to get this thread sent to RnR:evil:
 
Nothing here in southcentral (Wasilla/Anchorage/Kenai). Airstrips dry as a bone. Only chance for skis is being based on lake ice, but then there is nowhere yet to land other than some other lake. Not sure how northeren Ak is doing.
 
Good ice, no sno on Dune Lake, (sw of fai )

btw, this photo my get submitted for next calendar thing.... Cause I didn't take it..!
 

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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

that is why 1/8" cable is too small for the check cable... Lose the bungees for springs...
 
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I've got about 25 hours and perhaps as many as 300 landings on these skis now and I am really pleased with the skis and the rigging. Without snowshoes on, the snow in this picture would let me sink past my knees. These skis also turn very tight with some forward stick both to the left and right.

I made a takeoff a few days ago into a 20 mph headwind and a DA of about -1500' and I'm sure the skis didn't slide more than about a ski length before I was in the air.
 

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"I've got about 25 hours and perhaps as many as 300 landings on these skis"

Wow. A landing every five minutes? Wow.
 
"I've got about 25 hours and perhaps as many as 300 landings on these skis"

Wow. A landing every five minutes? Wow.

I didn't do the math but I love to make multiple landings. I've got a couple of places, like on the reservoir yesterday, where I'd take off and get about 25' in the air and then make another landing. A minute or two later another one. And out there you can do that for 10 miles each direction. It doesn't take long to make a bunch of landings. Yesterday was such a great day I was out there for a long time.... :smile:
 
I didn't do the math but I love to make multiple landings. I've got a couple of places, like on the reservoir yesterday, where I'd take off and get about 25' in the air and then make another landing. A minute or two later another one. And out there you can do that for 10 miles each direction. It doesn't take long to make a bunch of landings. Yesterday was such a great day I was out there for a long time.... :smile:

Until you get powder like that to play in nobody will understand.

Glenn
 
We had a foot or more of snow last Sunday but then the wind blew for a few days. Got to play a little today

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Step comes in handy

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Was having fun till freezing rain

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Glenn


Seldom does a week go by that I am not asked by customers and local friends "why do you enjoy that Glenn guy so much?". I think his pictures answer the question - who on the planet could not love a guy who has a 12/3 SkiDoo (okay - so it doesn't have the optional front bumper) and a turn of the century (pre 1900's) metal lawn chair along with a pristine (and well used/well cared for) pa-11 in his hangar? Add in his most recent comment about skiing in powder and I think even Joe will have to agree - Glennie is a rock star.
 
"I've got about 25 hours and perhaps as many as 300 landings on these skis"

Wow. A landing every five minutes? Wow.

Today was another excellent ski flying day and I decided to go back to the reservoir. Wondering if I'd overestimated how many landings I may have made out there a couple of days ago, I thought I'd time myself doing a couple of 10 set landings routines with the stop watch on my iPhone. It surprised me. The first 10 took 2 minutes 16 seconds. The second set of ten were 2:44. That's 20 landings in 5 minutes.

These are not FAA type currency landings for a tail dragger. I takeoff and almost immediately setup for the next landing. Few of the landings are full stop. Most of the time I'm pushing in the throttle again when I've slowed to about 20 mph. Then a throttle bump and it is off again. Sometimes I'm changing from 2 notches of flaps for takeoff to 3 notches for landing. But sometimes I leave it at 2 or 3 for both. And some are done with no flaps.

I was introduced to this type of landing routine years ago when I got a seaplane rating in a PA18. The instructor had me do landing after landing like this on the lake we were operating on. We went for miles doing this. It was fun and didn't take long to get the sight picture and procedures established this way. It is still way too much fun. ;-)

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There is a lot of places to land out here.

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I didnt like seeing this; laying some tracks showed overflow on the next pass. Glad I didn't stop here.

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The overflow was in the shaded area on the far side of these islands.
 

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Used to be a large dairy barn where my hangar now sits, burned to the ground in 79. I'm stuck with a 10' deep X 20' blue harvester silo concrete foundation, I started make a ? structure out of it.

Glenn
 
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